--- embedaddon/pcre/doc/pcre.txt 2012/10/09 09:19:17 1.1.1.3 +++ embedaddon/pcre/doc/pcre.txt 2014/06/15 19:46:04 1.1.1.5 @@ -8,13 +8,13 @@ pcretest commands. ----------------------------------------------------------------------------- -PCRE(3) PCRE(3) +PCRE(3) Library Functions Manual PCRE(3) + NAME PCRE - Perl-compatible regular expressions - INTRODUCTION The PCRE library is a set of functions that implement regular expres- @@ -32,20 +32,28 @@ INTRODUCTION either one or both to be built. The majority of the work to make this possible was done by Zoltan Herczeg. - The two libraries contain identical sets of functions, except that the - names in the 16-bit library start with pcre16_ instead of pcre_. To - avoid over-complication and reduce the documentation maintenance load, - most of the documentation describes the 8-bit library, with the differ- - ences for the 16-bit library described separately in the pcre16 page. - References to functions or structures of the form pcre[16]_xxx should - be read as meaning "pcre_xxx when using the 8-bit library and - pcre16_xxx when using the 16-bit library". + Starting with release 8.32 it is possible to compile a third separate + PCRE library that supports 32-bit character strings (including UTF-32 + strings). The build process allows any combination of the 8-, 16- and + 32-bit libraries. The work to make this possible was done by Christian + Persch. + The three libraries contain identical sets of functions, except that + the names in the 16-bit library start with pcre16_ instead of pcre_, + and the names in the 32-bit library start with pcre32_ instead of + pcre_. To avoid over-complication and reduce the documentation mainte- + nance load, most of the documentation describes the 8-bit library, with + the differences for the 16-bit and 32-bit libraries described sepa- + rately in the pcre16 and pcre32 pages. References to functions or + structures of the form pcre[16|32]_xxx should be read as meaning + "pcre_xxx when using the 8-bit library, pcre16_xxx when using the + 16-bit library, or pcre32_xxx when using the 32-bit library". + The current implementation of PCRE corresponds approximately with Perl - 5.12, including support for UTF-8/16 encoded strings and Unicode gen- - eral category properties. However, UTF-8/16 and Unicode support has to - be explicitly enabled; it is not the default. The Unicode tables corre- - spond to Unicode release 6.0.0. + 5.12, including support for UTF-8/16/32 encoded strings and Unicode + general category properties. However, UTF-8/16/32 and Unicode support + has to be explicitly enabled; it is not the default. The Unicode tables + correspond to Unicode release 6.3.0. In addition to the Perl-compatible matching function, PCRE contains an alternative function that matches the same compiled patterns in a dif- @@ -73,17 +81,50 @@ INTRODUCTION client to discover which features are available. The features them- selves are described in the pcrebuild page. Documentation about build- ing PCRE for various operating systems can be found in the README and - NON-UNIX-USE files in the source distribution. + NON-AUTOTOOLS_BUILD files in the source distribution. The libraries contains a number of undocumented internal functions and data tables that are used by more than one of the exported external functions, but which are not intended for use by external callers. - Their names all begin with "_pcre_" or "_pcre16_", which hopefully will - not provoke any name clashes. In some environments, it is possible to - control which external symbols are exported when a shared library is - built, and in these cases the undocumented symbols are not exported. + Their names all begin with "_pcre_" or "_pcre16_" or "_pcre32_", which + hopefully will not provoke any name clashes. In some environments, it + is possible to control which external symbols are exported when a + shared library is built, and in these cases the undocumented symbols + are not exported. +SECURITY CONSIDERATIONS + + If you are using PCRE in a non-UTF application that permits users to + supply arbitrary patterns for compilation, you should be aware of a + feature that allows users to turn on UTF support from within a pattern, + provided that PCRE was built with UTF support. For example, an 8-bit + pattern that begins with "(*UTF8)" or "(*UTF)" turns on UTF-8 mode, + which interprets patterns and subjects as strings of UTF-8 characters + instead of individual 8-bit characters. This causes both the pattern + and any data against which it is matched to be checked for UTF-8 valid- + ity. If the data string is very long, such a check might use suffi- + ciently many resources as to cause your application to lose perfor- + mance. + + One way of guarding against this possibility is to use the + pcre_fullinfo() function to check the compiled pattern's options for + UTF. Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF + option at compile time. This causes an compile time error if a pattern + contains a UTF-setting sequence. + + If your application is one that supports UTF, be aware that validity + checking can take time. If the same data string is to be matched many + times, you can use the PCRE_NO_UTF[8|16|32]_CHECK option for the second + and subsequent matches to save redundant checks. + + Another way that performance can be hit is by running a pattern that + has a very large search tree against a string that will never match. + Nested unlimited repeats in a pattern are a common example. PCRE pro- + vides some protection against this: see the PCRE_EXTRA_MATCH_LIMIT fea- + ture in the pcreapi page. + + USER DOCUMENTATION The user documentation for PCRE comprises a number of different sec- @@ -94,10 +135,11 @@ USER DOCUMENTATION lows: pcre this document - pcre16 details of the 16-bit library pcre-config show PCRE installation configuration information + pcre16 details of the 16-bit library + pcre32 details of the 32-bit library pcreapi details of PCRE's native C API - pcrebuild options for building PCRE + pcrebuild building PCRE pcrecallout details of the callout feature pcrecompat discussion of Perl compatibility pcrecpp details of the C++ wrapper for the 8-bit library @@ -116,10 +158,10 @@ USER DOCUMENTATION pcrestack discussion of stack usage pcresyntax quick syntax reference pcretest description of the pcretest testing command - pcreunicode discussion of Unicode and UTF-8/16 support + pcreunicode discussion of Unicode and UTF-8/16/32 support In addition, in the "man" and HTML formats, there is a short page for - each 8-bit C library function, listing its arguments and results. + each C library function, listing its arguments and results. AUTHOR @@ -135,14 +177,15 @@ AUTHOR REVISION - Last updated: 10 January 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 13 May 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCRE(3) PCRE(3) +PCRE(3) Library Functions Manual PCRE(3) + NAME PCRE - Perl-compatible regular expressions @@ -278,8 +321,8 @@ THE PCRE 16-BIT LIBRARY THE HEADER FILE There is only one header file, pcre.h. It contains prototypes for all - the functions in both libraries, as well as definitions of flags, - structures, error codes, etc. + the functions in all libraries, as well as definitions of flags, struc- + tures, error codes, etc. THE LIBRARY NAME @@ -297,9 +340,9 @@ STRING TYPES PCRE_UCHAR16 specifies an appropriate data type, and PCRE_SPTR16 is defined as "const PCRE_UCHAR16 *". In very many environments, "short int" is a 16-bit data type. When PCRE is built, it defines PCRE_UCHAR16 - as "short int", but checks that it really is a 16-bit data type. If it - is not, the build fails with an error message telling the maintainer to - modify the definition appropriately. + as "unsigned short int", but checks that it really is a 16-bit data + type. If it is not, the build fails with an error message telling the + maintainer to modify the definition appropriately. STRUCTURE TYPES @@ -350,8 +393,10 @@ STRUCTURE TYPES SUBJECT STRING OFFSETS - The offsets within subject strings that are returned by the matching - functions are in 16-bit units rather than bytes. + The lengths and starting offsets of subject strings must be specified + in 16-bit data units, and the offsets within subject strings that are + returned by the matching functions are in also 16-bit units rather than + bytes. NAMED SUBPATTERNS @@ -372,83 +417,86 @@ OPTION NAMES For the pcre16_config() function there is an option PCRE_CONFIG_UTF16 that returns 1 if UTF-16 support is configured, otherwise 0. If this - option is given to pcre_config(), or if the PCRE_CONFIG_UTF8 option is - given to pcre16_config(), the result is the PCRE_ERROR_BADOPTION error. + option is given to pcre_config() or pcre32_config(), or if the + PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF32 option is given to pcre16_con- + fig(), the result is the PCRE_ERROR_BADOPTION error. CHARACTER CODES - In 16-bit mode, when PCRE_UTF16 is not set, character values are + In 16-bit mode, when PCRE_UTF16 is not set, character values are treated in the same way as in 8-bit, non UTF-8 mode, except, of course, - that they can range from 0 to 0xffff instead of 0 to 0xff. Character - types for characters less than 0xff can therefore be influenced by the - locale in the same way as before. Characters greater than 0xff have + that they can range from 0 to 0xffff instead of 0 to 0xff. Character + types for characters less than 0xff can therefore be influenced by the + locale in the same way as before. Characters greater than 0xff have only one case, and no "type" (such as letter or digit). - In UTF-16 mode, the character code is Unicode, in the range 0 to - 0x10ffff, with the exception of values in the range 0xd800 to 0xdfff - because those are "surrogate" values that are used in pairs to encode + In UTF-16 mode, the character code is Unicode, in the range 0 to + 0x10ffff, with the exception of values in the range 0xd800 to 0xdfff + because those are "surrogate" values that are used in pairs to encode values greater than 0xffff. - A UTF-16 string can indicate its endianness by special code knows as a + A UTF-16 string can indicate its endianness by special code knows as a byte-order mark (BOM). The PCRE functions do not handle this, expecting - strings to be in host byte order. A utility function called - pcre16_utf16_to_host_byte_order() is provided to help with this (see + strings to be in host byte order. A utility function called + pcre16_utf16_to_host_byte_order() is provided to help with this (see above). ERROR NAMES - The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16 corre- - spond to their 8-bit counterparts. The error PCRE_ERROR_BADMODE is - given when a compiled pattern is passed to a function that processes - patterns in the other mode, for example, if a pattern compiled with + The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16 corre- + spond to their 8-bit counterparts. The error PCRE_ERROR_BADMODE is + given when a compiled pattern is passed to a function that processes + patterns in the other mode, for example, if a pattern compiled with pcre_compile() is passed to pcre16_exec(). - There are new error codes whose names begin with PCRE_UTF16_ERR for - invalid UTF-16 strings, corresponding to the PCRE_UTF8_ERR codes for - UTF-8 strings that are described in the section entitled "Reason codes - for invalid UTF-8 strings" in the main pcreapi page. The UTF-16 errors + There are new error codes whose names begin with PCRE_UTF16_ERR for + invalid UTF-16 strings, corresponding to the PCRE_UTF8_ERR codes for + UTF-8 strings that are described in the section entitled "Reason codes + for invalid UTF-8 strings" in the main pcreapi page. The UTF-16 errors are: PCRE_UTF16_ERR1 Missing low surrogate at end of string PCRE_UTF16_ERR2 Invalid low surrogate follows high surrogate PCRE_UTF16_ERR3 Isolated low surrogate - PCRE_UTF16_ERR4 Invalid character 0xfffe + PCRE_UTF16_ERR4 Non-character ERROR TEXTS - If there is an error while compiling a pattern, the error text that is - passed back by pcre16_compile() or pcre16_compile2() is still an 8-bit + If there is an error while compiling a pattern, the error text that is + passed back by pcre16_compile() or pcre16_compile2() is still an 8-bit character string, zero-terminated. CALLOUTS - The subject and mark fields in the callout block that is passed to a + The subject and mark fields in the callout block that is passed to a callout function point to 16-bit vectors. TESTING - The pcretest program continues to operate with 8-bit input and output - files, but it can be used for testing the 16-bit library. If it is run + The pcretest program continues to operate with 8-bit input and output + files, but it can be used for testing the 16-bit library. If it is run with the command line option -16, patterns and subject strings are con- verted from 8-bit to 16-bit before being passed to PCRE, and the 16-bit - library functions are used instead of the 8-bit ones. Returned 16-bit - strings are converted to 8-bit for output. If the 8-bit library was not - compiled, pcretest defaults to 16-bit and the -16 option is ignored. + library functions are used instead of the 8-bit ones. Returned 16-bit + strings are converted to 8-bit for output. If both the 8-bit and the + 32-bit libraries were not compiled, pcretest defaults to 16-bit and the + -16 option is ignored. When PCRE is being built, the RunTest script that is called by "make - check" uses the pcretest -C option to discover which of the 8-bit and - 16-bit libraries has been built, and runs the tests appropriately. + check" uses the pcretest -C option to discover which of the 8-bit, + 16-bit and 32-bit libraries has been built, and runs the tests appro- + priately. NOT SUPPORTED IN 16-BIT MODE Not all the features of the 8-bit library are available with the 16-bit - library. The C++ and POSIX wrapper functions support only the 8-bit + library. The C++ and POSIX wrapper functions support only the 8-bit library, and the pcregrep program is at present 8-bit only. @@ -461,73 +509,422 @@ AUTHOR REVISION - Last updated: 14 April 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 12 May 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCREBUILD(3) PCREBUILD(3) +PCRE(3) Library Functions Manual PCRE(3) + NAME PCRE - Perl-compatible regular expressions + #include + +PCRE 32-BIT API BASIC FUNCTIONS + + pcre32 *pcre32_compile(PCRE_SPTR32 pattern, int options, + const char **errptr, int *erroffset, + const unsigned char *tableptr); + + pcre32 *pcre32_compile2(PCRE_SPTR32 pattern, int options, + int *errorcodeptr, + const unsigned char *tableptr); + + pcre32_extra *pcre32_study(const pcre32 *code, int options, + const char **errptr); + + void pcre32_free_study(pcre32_extra *extra); + + int pcre32_exec(const pcre32 *code, const pcre32_extra *extra, + PCRE_SPTR32 subject, int length, int startoffset, + int options, int *ovector, int ovecsize); + + int pcre32_dfa_exec(const pcre32 *code, const pcre32_extra *extra, + PCRE_SPTR32 subject, int length, int startoffset, + int options, int *ovector, int ovecsize, + int *workspace, int wscount); + + +PCRE 32-BIT API STRING EXTRACTION FUNCTIONS + + int pcre32_copy_named_substring(const pcre32 *code, + PCRE_SPTR32 subject, int *ovector, + int stringcount, PCRE_SPTR32 stringname, + PCRE_UCHAR32 *buffer, int buffersize); + + int pcre32_copy_substring(PCRE_SPTR32 subject, int *ovector, + int stringcount, int stringnumber, PCRE_UCHAR32 *buffer, + int buffersize); + + int pcre32_get_named_substring(const pcre32 *code, + PCRE_SPTR32 subject, int *ovector, + int stringcount, PCRE_SPTR32 stringname, + PCRE_SPTR32 *stringptr); + + int pcre32_get_stringnumber(const pcre32 *code, + PCRE_SPTR32 name); + + int pcre32_get_stringtable_entries(const pcre32 *code, + PCRE_SPTR32 name, PCRE_UCHAR32 **first, PCRE_UCHAR32 **last); + + int pcre32_get_substring(PCRE_SPTR32 subject, int *ovector, + int stringcount, int stringnumber, + PCRE_SPTR32 *stringptr); + + int pcre32_get_substring_list(PCRE_SPTR32 subject, + int *ovector, int stringcount, PCRE_SPTR32 **listptr); + + void pcre32_free_substring(PCRE_SPTR32 stringptr); + + void pcre32_free_substring_list(PCRE_SPTR32 *stringptr); + + +PCRE 32-BIT API AUXILIARY FUNCTIONS + + pcre32_jit_stack *pcre32_jit_stack_alloc(int startsize, int maxsize); + + void pcre32_jit_stack_free(pcre32_jit_stack *stack); + + void pcre32_assign_jit_stack(pcre32_extra *extra, + pcre32_jit_callback callback, void *data); + + const unsigned char *pcre32_maketables(void); + + int pcre32_fullinfo(const pcre32 *code, const pcre32_extra *extra, + int what, void *where); + + int pcre32_refcount(pcre32 *code, int adjust); + + int pcre32_config(int what, void *where); + + const char *pcre32_version(void); + + int pcre32_pattern_to_host_byte_order(pcre32 *code, + pcre32_extra *extra, const unsigned char *tables); + + +PCRE 32-BIT API INDIRECTED FUNCTIONS + + void *(*pcre32_malloc)(size_t); + + void (*pcre32_free)(void *); + + void *(*pcre32_stack_malloc)(size_t); + + void (*pcre32_stack_free)(void *); + + int (*pcre32_callout)(pcre32_callout_block *); + + +PCRE 32-BIT API 32-BIT-ONLY FUNCTION + + int pcre32_utf32_to_host_byte_order(PCRE_UCHAR32 *output, + PCRE_SPTR32 input, int length, int *byte_order, + int keep_boms); + + +THE PCRE 32-BIT LIBRARY + + Starting with release 8.32, it is possible to compile a PCRE library + that supports 32-bit character strings, including UTF-32 strings, as + well as or instead of the original 8-bit library. This work was done by + Christian Persch, based on the work done by Zoltan Herczeg for the + 16-bit library. All three libraries contain identical sets of func- + tions, used in exactly the same way. Only the names of the functions + and the data types of their arguments and results are different. To + avoid over-complication and reduce the documentation maintenance load, + most of the PCRE documentation describes the 8-bit library, with only + occasional references to the 16-bit and 32-bit libraries. This page + describes what is different when you use the 32-bit library. + + WARNING: A single application can be linked with all or any of the + three libraries, but you must take care when processing any particular + pattern to use functions from just one library. For example, if you + want to study a pattern that was compiled with pcre32_compile(), you + must do so with pcre32_study(), not pcre_study(), and you must free the + study data with pcre32_free_study(). + + +THE HEADER FILE + + There is only one header file, pcre.h. It contains prototypes for all + the functions in all libraries, as well as definitions of flags, struc- + tures, error codes, etc. + + +THE LIBRARY NAME + + In Unix-like systems, the 32-bit library is called libpcre32, and can + normally be accesss by adding -lpcre32 to the command for linking an + application that uses PCRE. + + +STRING TYPES + + In the 8-bit library, strings are passed to PCRE library functions as + vectors of bytes with the C type "char *". In the 32-bit library, + strings are passed as vectors of unsigned 32-bit quantities. The macro + PCRE_UCHAR32 specifies an appropriate data type, and PCRE_SPTR32 is + defined as "const PCRE_UCHAR32 *". In very many environments, "unsigned + int" is a 32-bit data type. When PCRE is built, it defines PCRE_UCHAR32 + as "unsigned int", but checks that it really is a 32-bit data type. If + it is not, the build fails with an error message telling the maintainer + to modify the definition appropriately. + + +STRUCTURE TYPES + + The types of the opaque structures that are used for compiled 32-bit + patterns and JIT stacks are pcre32 and pcre32_jit_stack respectively. + The type of the user-accessible structure that is returned by + pcre32_study() is pcre32_extra, and the type of the structure that is + used for passing data to a callout function is pcre32_callout_block. + These structures contain the same fields, with the same names, as their + 8-bit counterparts. The only difference is that pointers to character + strings are 32-bit instead of 8-bit types. + + +32-BIT FUNCTIONS + + For every function in the 8-bit library there is a corresponding func- + tion in the 32-bit library with a name that starts with pcre32_ instead + of pcre_. The prototypes are listed above. In addition, there is one + extra function, pcre32_utf32_to_host_byte_order(). This is a utility + function that converts a UTF-32 character string to host byte order if + necessary. The other 32-bit functions expect the strings they are + passed to be in host byte order. + + The input and output arguments of pcre32_utf32_to_host_byte_order() may + point to the same address, that is, conversion in place is supported. + The output buffer must be at least as long as the input. + + The length argument specifies the number of 32-bit data units in the + input string; a negative value specifies a zero-terminated string. + + If byte_order is NULL, it is assumed that the string starts off in host + byte order. This may be changed by byte-order marks (BOMs) anywhere in + the string (commonly as the first character). + + If byte_order is not NULL, a non-zero value of the integer to which it + points means that the input starts off in host byte order, otherwise + the opposite order is assumed. Again, BOMs in the string can change + this. The final byte order is passed back at the end of processing. + + If keep_boms is not zero, byte-order mark characters (0xfeff) are + copied into the output string. Otherwise they are discarded. + + The result of the function is the number of 32-bit units placed into + the output buffer, including the zero terminator if the string was + zero-terminated. + + +SUBJECT STRING OFFSETS + + The lengths and starting offsets of subject strings must be specified + in 32-bit data units, and the offsets within subject strings that are + returned by the matching functions are in also 32-bit units rather than + bytes. + + +NAMED SUBPATTERNS + + The name-to-number translation table that is maintained for named sub- + patterns uses 32-bit characters. The pcre32_get_stringtable_entries() + function returns the length of each entry in the table as the number of + 32-bit data units. + + +OPTION NAMES + + There are two new general option names, PCRE_UTF32 and + PCRE_NO_UTF32_CHECK, which correspond to PCRE_UTF8 and + PCRE_NO_UTF8_CHECK in the 8-bit library. In fact, these new options + define the same bits in the options word. There is a discussion about + the validity of UTF-32 strings in the pcreunicode page. + + For the pcre32_config() function there is an option PCRE_CONFIG_UTF32 + that returns 1 if UTF-32 support is configured, otherwise 0. If this + option is given to pcre_config() or pcre16_config(), or if the + PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF16 option is given to pcre32_con- + fig(), the result is the PCRE_ERROR_BADOPTION error. + + +CHARACTER CODES + + In 32-bit mode, when PCRE_UTF32 is not set, character values are + treated in the same way as in 8-bit, non UTF-8 mode, except, of course, + that they can range from 0 to 0x7fffffff instead of 0 to 0xff. Charac- + ter types for characters less than 0xff can therefore be influenced by + the locale in the same way as before. Characters greater than 0xff + have only one case, and no "type" (such as letter or digit). + + In UTF-32 mode, the character code is Unicode, in the range 0 to + 0x10ffff, with the exception of values in the range 0xd800 to 0xdfff + because those are "surrogate" values that are ill-formed in UTF-32. + + A UTF-32 string can indicate its endianness by special code knows as a + byte-order mark (BOM). The PCRE functions do not handle this, expecting + strings to be in host byte order. A utility function called + pcre32_utf32_to_host_byte_order() is provided to help with this (see + above). + + +ERROR NAMES + + The error PCRE_ERROR_BADUTF32 corresponds to its 8-bit counterpart. + The error PCRE_ERROR_BADMODE is given when a compiled pattern is passed + to a function that processes patterns in the other mode, for example, + if a pattern compiled with pcre_compile() is passed to pcre32_exec(). + + There are new error codes whose names begin with PCRE_UTF32_ERR for + invalid UTF-32 strings, corresponding to the PCRE_UTF8_ERR codes for + UTF-8 strings that are described in the section entitled "Reason codes + for invalid UTF-8 strings" in the main pcreapi page. The UTF-32 errors + are: + + PCRE_UTF32_ERR1 Surrogate character (range from 0xd800 to 0xdfff) + PCRE_UTF32_ERR2 Non-character + PCRE_UTF32_ERR3 Character > 0x10ffff + + +ERROR TEXTS + + If there is an error while compiling a pattern, the error text that is + passed back by pcre32_compile() or pcre32_compile2() is still an 8-bit + character string, zero-terminated. + + +CALLOUTS + + The subject and mark fields in the callout block that is passed to a + callout function point to 32-bit vectors. + + +TESTING + + The pcretest program continues to operate with 8-bit input and output + files, but it can be used for testing the 32-bit library. If it is run + with the command line option -32, patterns and subject strings are con- + verted from 8-bit to 32-bit before being passed to PCRE, and the 32-bit + library functions are used instead of the 8-bit ones. Returned 32-bit + strings are converted to 8-bit for output. If both the 8-bit and the + 16-bit libraries were not compiled, pcretest defaults to 32-bit and the + -32 option is ignored. + + When PCRE is being built, the RunTest script that is called by "make + check" uses the pcretest -C option to discover which of the 8-bit, + 16-bit and 32-bit libraries has been built, and runs the tests appro- + priately. + + +NOT SUPPORTED IN 32-BIT MODE + + Not all the features of the 8-bit library are available with the 32-bit + library. The C++ and POSIX wrapper functions support only the 8-bit + library, and the pcregrep program is at present 8-bit only. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 12 May 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREBUILD(3) Library Functions Manual PCREBUILD(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +BUILDING PCRE + + PCRE is distributed with a configure script that can be used to build + the library in Unix-like environments using the applications known as + Autotools. Also in the distribution are files to support building + using CMake instead of configure. The text file README contains general + information about building with Autotools (some of which is repeated + below), and also has some comments about building on various operating + systems. There is a lot more information about building PCRE without + using Autotools (including information about using CMake and building + "by hand") in the text file called NON-AUTOTOOLS-BUILD. You should + consult this file as well as the README file if you are building in a + non-Unix-like environment. + + PCRE BUILD-TIME OPTIONS - This document describes the optional features of PCRE that can be - selected when the library is compiled. It assumes use of the configure - script, where the optional features are selected or deselected by pro- - viding options to configure before running the make command. However, - the same options can be selected in both Unix-like and non-Unix-like - environments using the GUI facility of cmake-gui if you are using CMake - instead of configure to build PCRE. + The rest of this document describes the optional features of PCRE that + can be selected when the library is compiled. It assumes use of the + configure script, where the optional features are selected or dese- + lected by providing options to configure before running the make com- + mand. However, the same options can be selected in both Unix-like and + non-Unix-like environments using the GUI facility of cmake-gui if you + are using CMake instead of configure to build PCRE. - There is a lot more information about building PCRE in non-Unix-like - environments in the file called NON_UNIX_USE, which is part of the PCRE - distribution. You should consult this file as well as the README file - if you are building in a non-Unix-like environment. + If you are not using Autotools or CMake, option selection can be done + by editing the config.h file, or by passing parameter settings to the + compiler, as described in NON-AUTOTOOLS-BUILD. The complete list of options for configure (which includes the standard - ones such as the selection of the installation directory) can be + ones such as the selection of the installation directory) can be obtained by running ./configure --help - The following sections include descriptions of options whose names + The following sections include descriptions of options whose names begin with --enable or --disable. These settings specify changes to the - defaults for the configure command. Because of the way that configure - works, --enable and --disable always come in pairs, so the complemen- - tary option always exists as well, but as it specifies the default, it + defaults for the configure command. Because of the way that configure + works, --enable and --disable always come in pairs, so the complemen- + tary option always exists as well, but as it specifies the default, it is not described. -BUILDING 8-BIT and 16-BIT LIBRARIES +BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES - By default, a library called libpcre is built, containing functions - that take string arguments contained in vectors of bytes, either as - single-byte characters, or interpreted as UTF-8 strings. You can also - build a separate library, called libpcre16, in which strings are con- - tained in vectors of 16-bit data units and interpreted either as sin- + By default, a library called libpcre is built, containing functions + that take string arguments contained in vectors of bytes, either as + single-byte characters, or interpreted as UTF-8 strings. You can also + build a separate library, called libpcre16, in which strings are con- + tained in vectors of 16-bit data units and interpreted either as sin- gle-unit characters or UTF-16 strings, by adding --enable-pcre16 + to the configure command. You can also build yet another separate + library, called libpcre32, in which strings are contained in vectors of + 32-bit data units and interpreted either as single-unit characters or + UTF-32 strings, by adding + + --enable-pcre32 + to the configure command. If you do not want the 8-bit library, add --disable-pcre8 - as well. At least one of the two libraries must be built. Note that the - C++ and POSIX wrappers are for the 8-bit library only, and that pcre- - grep is an 8-bit program. None of these are built if you select only - the 16-bit library. + as well. At least one of the three libraries must be built. Note that + the C++ and POSIX wrappers are for the 8-bit library only, and that + pcregrep is an 8-bit program. None of these are built if you select + only the 16-bit or 32-bit libraries. BUILDING SHARED AND STATIC LIBRARIES - The PCRE building process uses libtool to build both shared and static - Unix libraries by default. You can suppress one of these by adding one - of + The Autotools PCRE building process uses libtool to build both shared + and static libraries by default. You can suppress one of these by + adding one of --disable-shared --disable-static @@ -547,48 +944,49 @@ C++ SUPPORT to the configure command. -UTF-8 and UTF-16 SUPPORT +UTF-8, UTF-16 AND UTF-32 SUPPORT To build PCRE with support for UTF Unicode character strings, add --enable-utf - to the configure command. This setting applies to both libraries, - adding support for UTF-8 to the 8-bit library and support for UTF-16 to - the 16-bit library. There are no separate options for enabling UTF-8 - and UTF-16 independently because that would allow ridiculous settings - such as requesting UTF-16 support while building only the 8-bit - library. It is not possible to build one library with UTF support and - the other without in the same configuration. (For backwards compatibil- - ity, --enable-utf8 is a synonym of --enable-utf.) + to the configure command. This setting applies to all three libraries, + adding support for UTF-8 to the 8-bit library, support for UTF-16 to + the 16-bit library, and support for UTF-32 to the to the 32-bit + library. There are no separate options for enabling UTF-8, UTF-16 and + UTF-32 independently because that would allow ridiculous settings such + as requesting UTF-16 support while building only the 8-bit library. It + is not possible to build one library with UTF support and another with- + out in the same configuration. (For backwards compatibility, --enable- + utf8 is a synonym of --enable-utf.) - Of itself, this setting does not make PCRE treat strings as UTF-8 or - UTF-16. As well as compiling PCRE with this option, you also have have - to set the PCRE_UTF8 or PCRE_UTF16 option when you call one of the pat- - tern compiling functions. + Of itself, this setting does not make PCRE treat strings as UTF-8, + UTF-16 or UTF-32. As well as compiling PCRE with this option, you also + have have to set the PCRE_UTF8, PCRE_UTF16 or PCRE_UTF32 option (as + appropriate) when you call one of the pattern compiling functions. - If you set --enable-utf when compiling in an EBCDIC environment, PCRE - expects its input to be either ASCII or UTF-8 (depending on the run- + If you set --enable-utf when compiling in an EBCDIC environment, PCRE + expects its input to be either ASCII or UTF-8 (depending on the run- time option). It is not possible to support both EBCDIC and UTF-8 codes - in the same version of the library. Consequently, --enable-utf and + in the same version of the library. Consequently, --enable-utf and --enable-ebcdic are mutually exclusive. UNICODE CHARACTER PROPERTY SUPPORT - UTF support allows the libraries to process character codepoints up to - 0x10ffff in the strings that they handle. On its own, however, it does + UTF support allows the libraries to process character codepoints up to + 0x10ffff in the strings that they handle. On its own, however, it does not provide any facilities for accessing the properties of such charac- ters. If you want to be able to use the pattern escapes \P, \p, and \X, which refer to Unicode character properties, you must add --enable-unicode-properties - to the configure command. This implies UTF support, even if you have + to the configure command. This implies UTF support, even if you have not explicitly requested it. - Including Unicode property support adds around 30K of tables to the - PCRE library. Only the general category properties such as Lu and Nd + Including Unicode property support adds around 30K of tables to the + PCRE library. Only the general category properties such as Lu and Nd are supported. Details are given in the pcrepattern documentation. @@ -598,9 +996,9 @@ JUST-IN-TIME COMPILER SUPPORT --enable-jit - This support is available only for certain hardware architectures. If - this option is set for an unsupported architecture, a compile time - error occurs. See the pcrejit documentation for a discussion of JIT + This support is available only for certain hardware architectures. If + this option is set for an unsupported architecture, a compile time + error occurs. See the pcrejit documentation for a discussion of JIT usage. When JIT support is enabled, pcregrep automatically makes use of it, unless you add @@ -611,14 +1009,14 @@ JUST-IN-TIME COMPILER SUPPORT CODE VALUE OF NEWLINE - By default, PCRE interprets the linefeed (LF) character as indicating - the end of a line. This is the normal newline character on Unix-like - systems. You can compile PCRE to use carriage return (CR) instead, by + By default, PCRE interprets the linefeed (LF) character as indicating + the end of a line. This is the normal newline character on Unix-like + systems. You can compile PCRE to use carriage return (CR) instead, by adding --enable-newline-is-cr - to the configure command. There is also a --enable-newline-is-lf + to the configure command. There is also a --enable-newline-is-lf option, which explicitly specifies linefeed as the newline character. Alternatively, you can specify that line endings are to be indicated by @@ -630,40 +1028,40 @@ CODE VALUE OF NEWLINE --enable-newline-is-anycrlf - which causes PCRE to recognize any of the three sequences CR, LF, or + which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as indicating a line ending. Finally, a fifth option, specified by --enable-newline-is-any causes PCRE to recognize any Unicode newline sequence. - Whatever line ending convention is selected when PCRE is built can be - overridden when the library functions are called. At build time it is + Whatever line ending convention is selected when PCRE is built can be + overridden when the library functions are called. At build time it is conventional to use the standard for your operating system. WHAT \R MATCHES - By default, the sequence \R in a pattern matches any Unicode newline - sequence, whatever has been selected as the line ending sequence. If + By default, the sequence \R in a pattern matches any Unicode newline + sequence, whatever has been selected as the line ending sequence. If you specify --enable-bsr-anycrlf - the default is changed so that \R matches only CR, LF, or CRLF. What- - ever is selected when PCRE is built can be overridden when the library + the default is changed so that \R matches only CR, LF, or CRLF. What- + ever is selected when PCRE is built can be overridden when the library functions are called. POSIX MALLOC USAGE - When the 8-bit library is called through the POSIX interface (see the - pcreposix documentation), additional working storage is required for - holding the pointers to capturing substrings, because PCRE requires + When the 8-bit library is called through the POSIX interface (see the + pcreposix documentation), additional working storage is required for + holding the pointers to capturing substrings, because PCRE requires three integers per substring, whereas the POSIX interface provides only - two. If the number of expected substrings is small, the wrapper func- - tion uses space on the stack, because this is faster than using mal- - loc() for each call. The default threshold above which the stack is no + two. If the number of expected substrings is small, the wrapper func- + tion uses space on the stack, because this is faster than using mal- + loc() for each call. The default threshold above which the stack is no longer used is 10; it can be changed by adding a setting such as --with-posix-malloc-threshold=20 @@ -673,115 +1071,132 @@ POSIX MALLOC USAGE HANDLING VERY LARGE PATTERNS - Within a compiled pattern, offset values are used to point from one - part to another (for example, from an opening parenthesis to an alter- - nation metacharacter). By default, two-byte values are used for these - offsets, leading to a maximum size for a compiled pattern of around - 64K. This is sufficient to handle all but the most gigantic patterns. - Nevertheless, some people do want to process truly enormous patterns, - so it is possible to compile PCRE to use three-byte or four-byte off- - sets by adding a setting such as + Within a compiled pattern, offset values are used to point from one + part to another (for example, from an opening parenthesis to an alter- + nation metacharacter). By default, in the 8-bit and 16-bit libraries, + two-byte values are used for these offsets, leading to a maximum size + for a compiled pattern of around 64K. This is sufficient to handle all + but the most gigantic patterns. Nevertheless, some people do want to + process truly enormous patterns, so it is possible to compile PCRE to + use three-byte or four-byte offsets by adding a setting such as --with-link-size=3 - to the configure command. The value given must be 2, 3, or 4. For the - 16-bit library, a value of 3 is rounded up to 4. Using longer offsets - slows down the operation of PCRE because it has to load additional data - when handling them. + to the configure command. The value given must be 2, 3, or 4. For the + 16-bit library, a value of 3 is rounded up to 4. In these libraries, + using longer offsets slows down the operation of PCRE because it has to + load additional data when handling them. For the 32-bit library the + value is always 4 and cannot be overridden; the value of --with-link- + size is ignored. AVOIDING EXCESSIVE STACK USAGE When matching with the pcre_exec() function, PCRE implements backtrack- - ing by making recursive calls to an internal function called match(). - In environments where the size of the stack is limited, this can se- - verely limit PCRE's operation. (The Unix environment does not usually + ing by making recursive calls to an internal function called match(). + In environments where the size of the stack is limited, this can se- + verely limit PCRE's operation. (The Unix environment does not usually suffer from this problem, but it may sometimes be necessary to increase - the maximum stack size. There is a discussion in the pcrestack docu- - mentation.) An alternative approach to recursion that uses memory from - the heap to remember data, instead of using recursive function calls, - has been implemented to work round the problem of limited stack size. + the maximum stack size. There is a discussion in the pcrestack docu- + mentation.) An alternative approach to recursion that uses memory from + the heap to remember data, instead of using recursive function calls, + has been implemented to work round the problem of limited stack size. If you want to build a version of PCRE that works this way, add --disable-stack-for-recursion - to the configure command. With this configuration, PCRE will use the - pcre_stack_malloc and pcre_stack_free variables to call memory manage- - ment functions. By default these point to malloc() and free(), but you + to the configure command. With this configuration, PCRE will use the + pcre_stack_malloc and pcre_stack_free variables to call memory manage- + ment functions. By default these point to malloc() and free(), but you can replace the pointers so that your own functions are used instead. - Separate functions are provided rather than using pcre_malloc and - pcre_free because the usage is very predictable: the block sizes - requested are always the same, and the blocks are always freed in - reverse order. A calling program might be able to implement optimized - functions that perform better than malloc() and free(). PCRE runs + Separate functions are provided rather than using pcre_malloc and + pcre_free because the usage is very predictable: the block sizes + requested are always the same, and the blocks are always freed in + reverse order. A calling program might be able to implement optimized + functions that perform better than malloc() and free(). PCRE runs noticeably more slowly when built in this way. This option affects only the pcre_exec() function; it is not relevant for pcre_dfa_exec(). LIMITING PCRE RESOURCE USAGE - Internally, PCRE has a function called match(), which it calls repeat- - edly (sometimes recursively) when matching a pattern with the - pcre_exec() function. By controlling the maximum number of times this - function may be called during a single matching operation, a limit can - be placed on the resources used by a single call to pcre_exec(). The - limit can be changed at run time, as described in the pcreapi documen- - tation. The default is 10 million, but this can be changed by adding a + Internally, PCRE has a function called match(), which it calls repeat- + edly (sometimes recursively) when matching a pattern with the + pcre_exec() function. By controlling the maximum number of times this + function may be called during a single matching operation, a limit can + be placed on the resources used by a single call to pcre_exec(). The + limit can be changed at run time, as described in the pcreapi documen- + tation. The default is 10 million, but this can be changed by adding a setting such as --with-match-limit=500000 - to the configure command. This setting has no effect on the + to the configure command. This setting has no effect on the pcre_dfa_exec() matching function. - In some environments it is desirable to limit the depth of recursive + In some environments it is desirable to limit the depth of recursive calls of match() more strictly than the total number of calls, in order - to restrict the maximum amount of stack (or heap, if --disable-stack- + to restrict the maximum amount of stack (or heap, if --disable-stack- for-recursion is specified) that is used. A second limit controls this; - it defaults to the value that is set for --with-match-limit, which - imposes no additional constraints. However, you can set a lower limit + it defaults to the value that is set for --with-match-limit, which + imposes no additional constraints. However, you can set a lower limit by adding, for example, --with-match-limit-recursion=10000 - to the configure command. This value can also be overridden at run + to the configure command. This value can also be overridden at run time. CREATING CHARACTER TABLES AT BUILD TIME - PCRE uses fixed tables for processing characters whose code values are - less than 256. By default, PCRE is built with a set of tables that are - distributed in the file pcre_chartables.c.dist. These tables are for + PCRE uses fixed tables for processing characters whose code values are + less than 256. By default, PCRE is built with a set of tables that are + distributed in the file pcre_chartables.c.dist. These tables are for ASCII codes only. If you add --enable-rebuild-chartables - to the configure command, the distributed tables are no longer used. - Instead, a program called dftables is compiled and run. This outputs + to the configure command, the distributed tables are no longer used. + Instead, a program called dftables is compiled and run. This outputs the source for new set of tables, created in the default locale of your - C run-time system. (This method of replacing the tables does not work - if you are cross compiling, because dftables is run on the local host. + C run-time system. (This method of replacing the tables does not work + if you are cross compiling, because dftables is run on the local host. If you need to create alternative tables when cross compiling, you will have to do so "by hand".) USING EBCDIC CODE - PCRE assumes by default that it will run in an environment where the - character code is ASCII (or Unicode, which is a superset of ASCII). - This is the case for most computer operating systems. PCRE can, how- + PCRE assumes by default that it will run in an environment where the + character code is ASCII (or Unicode, which is a superset of ASCII). + This is the case for most computer operating systems. PCRE can, how- ever, be compiled to run in an EBCDIC environment by adding --enable-ebcdic to the configure command. This setting implies --enable-rebuild-charta- - bles. You should only use it if you know that you are in an EBCDIC - environment (for example, an IBM mainframe operating system). The + bles. You should only use it if you know that you are in an EBCDIC + environment (for example, an IBM mainframe operating system). The --enable-ebcdic option is incompatible with --enable-utf. + The EBCDIC character that corresponds to an ASCII LF is assumed to have + the value 0x15 by default. However, in some EBCDIC environments, 0x25 + is used. In such an environment you should use + --enable-ebcdic-nl25 + + as well as, or instead of, --enable-ebcdic. The EBCDIC character for CR + has the same value as in ASCII, namely, 0x0d. Whichever of 0x15 and + 0x25 is not chosen as LF is made to correspond to the Unicode NEL char- + acter (which, in Unicode, is 0x85). + + The options that select newline behaviour, such as --enable-newline-is- + cr, and equivalent run-time options, refer to these character values in + an EBCDIC environment. + + PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT By default, pcregrep reads all files as plain text. You can build it so @@ -843,9 +1258,77 @@ PCRETEST OPTION FOR LIBREADLINE SUPPORT immediately before the configure command. +DEBUGGING WITH VALGRIND SUPPORT + + By adding the + + --enable-valgrind + + option to to the configure command, PCRE will use valgrind annotations + to mark certain memory regions as unaddressable. This allows it to + detect invalid memory accesses, and is mostly useful for debugging PCRE + itself. + + +CODE COVERAGE REPORTING + + If your C compiler is gcc, you can build a version of PCRE that can + generate a code coverage report for its test suite. To enable this, you + must install lcov version 1.6 or above. Then specify + + --enable-coverage + + to the configure command and build PCRE in the usual way. + + Note that using ccache (a caching C compiler) is incompatible with code + coverage reporting. If you have configured ccache to run automatically + on your system, you must set the environment variable + + CCACHE_DISABLE=1 + + before running make to build PCRE, so that ccache is not used. + + When --enable-coverage is used, the following addition targets are + added to the Makefile: + + make coverage + + This creates a fresh coverage report for the PCRE test suite. It is + equivalent to running "make coverage-reset", "make coverage-baseline", + "make check", and then "make coverage-report". + + make coverage-reset + + This zeroes the coverage counters, but does nothing else. + + make coverage-baseline + + This captures baseline coverage information. + + make coverage-report + + This creates the coverage report. + + make coverage-clean-report + + This removes the generated coverage report without cleaning the cover- + age data itself. + + make coverage-clean-data + + This removes the captured coverage data without removing the coverage + files created at compile time (*.gcno). + + make coverage-clean + + This cleans all coverage data including the generated coverage report. + For more information about code coverage, see the gcov and lcov docu- + mentation. + + SEE ALSO - pcreapi(3), pcre16, pcre_config(3). + pcreapi(3), pcre16, pcre32, pcre_config(3). AUTHOR @@ -857,32 +1340,34 @@ AUTHOR REVISION - Last updated: 07 January 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 12 May 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCREMATCHING(3) PCREMATCHING(3) +PCREMATCHING(3) Library Functions Manual PCREMATCHING(3) + NAME PCRE - Perl-compatible regular expressions - PCRE MATCHING ALGORITHMS This document describes the two different algorithms that are available in PCRE for matching a compiled regular expression against a given sub- ject string. The "standard" algorithm is the one provided by the - pcre_exec() and pcre16_exec() functions. These work in the same was as - Perl's matching function, and provide a Perl-compatible matching opera- - tion. The just-in-time (JIT) optimization that is described in the - pcrejit documentation is compatible with these functions. + pcre_exec(), pcre16_exec() and pcre32_exec() functions. These work in + the same as as Perl's matching function, and provide a Perl-compatible + matching operation. The just-in-time (JIT) optimization that is + described in the pcrejit documentation is compatible with these func- + tions. - An alternative algorithm is provided by the pcre_dfa_exec() and - pcre16_dfa_exec() functions; they operate in a different way, and are - not Perl-compatible. This alternative has advantages and disadvantages - compared with the standard algorithm, and these are described below. + An alternative algorithm is provided by the pcre_dfa_exec(), + pcre16_dfa_exec() and pcre32_dfa_exec() functions; they operate in a + different way, and are not Perl-compatible. This alternative has advan- + tages and disadvantages compared with the standard algorithm, and these + are described below. When there is only one possible way in which a given subject string can match a pattern, the two algorithms give the same answer. A difference @@ -972,72 +1457,81 @@ THE ALTERNATIVE MATCHING ALGORITHM at the fifth character of the subject. The algorithm does not automati- cally move on to find matches that start at later positions. + PCRE's "auto-possessification" optimization usually applies to charac- + ter repeats at the end of a pattern (as well as internally). For exam- + ple, the pattern "a\d+" is compiled as if it were "a\d++" because there + is no point even considering the possibility of backtracking into the + repeated digits. For DFA matching, this means that only one possible + match is found. If you really do want multiple matches in such cases, + either use an ungreedy repeat ("a\d+?") or set the PCRE_NO_AUTO_POSSESS + option when compiling. + There are a number of features of PCRE regular expressions that are not supported by the alternative matching algorithm. They are as follows: - 1. Because the algorithm finds all possible matches, the greedy or - ungreedy nature of repetition quantifiers is not relevant. Greedy and + 1. Because the algorithm finds all possible matches, the greedy or + ungreedy nature of repetition quantifiers is not relevant. Greedy and ungreedy quantifiers are treated in exactly the same way. However, pos- - sessive quantifiers can make a difference when what follows could also + sessive quantifiers can make a difference when what follows could also match what is quantified, for example in a pattern like this: ^a++\w! - This pattern matches "aaab!" but not "aaa!", which would be matched by - a non-possessive quantifier. Similarly, if an atomic group is present, - it is matched as if it were a standalone pattern at the current point, - and the longest match is then "locked in" for the rest of the overall + This pattern matches "aaab!" but not "aaa!", which would be matched by + a non-possessive quantifier. Similarly, if an atomic group is present, + it is matched as if it were a standalone pattern at the current point, + and the longest match is then "locked in" for the rest of the overall pattern. 2. When dealing with multiple paths through the tree simultaneously, it - is not straightforward to keep track of captured substrings for the - different matching possibilities, and PCRE's implementation of this + is not straightforward to keep track of captured substrings for the + different matching possibilities, and PCRE's implementation of this algorithm does not attempt to do this. This means that no captured sub- strings are available. - 3. Because no substrings are captured, back references within the pat- + 3. Because no substrings are captured, back references within the pat- tern are not supported, and cause errors if encountered. - 4. For the same reason, conditional expressions that use a backrefer- - ence as the condition or test for a specific group recursion are not + 4. For the same reason, conditional expressions that use a backrefer- + ence as the condition or test for a specific group recursion are not supported. - 5. Because many paths through the tree may be active, the \K escape + 5. Because many paths through the tree may be active, the \K escape sequence, which resets the start of the match when encountered (but may - be on some paths and not on others), is not supported. It causes an + be on some paths and not on others), is not supported. It causes an error if encountered. - 6. Callouts are supported, but the value of the capture_top field is + 6. Callouts are supported, but the value of the capture_top field is always 1, and the value of the capture_last field is always -1. - 7. The \C escape sequence, which (in the standard algorithm) always - matches a single data unit, even in UTF-8 or UTF-16 modes, is not sup- - ported in these modes, because the alternative algorithm moves through - the subject string one character (not data unit) at a time, for all - active paths through the tree. + 7. The \C escape sequence, which (in the standard algorithm) always + matches a single data unit, even in UTF-8, UTF-16 or UTF-32 modes, is + not supported in these modes, because the alternative algorithm moves + through the subject string one character (not data unit) at a time, for + all active paths through the tree. - 8. Except for (*FAIL), the backtracking control verbs such as (*PRUNE) - are not supported. (*FAIL) is supported, and behaves like a failing + 8. Except for (*FAIL), the backtracking control verbs such as (*PRUNE) + are not supported. (*FAIL) is supported, and behaves like a failing negative assertion. ADVANTAGES OF THE ALTERNATIVE ALGORITHM - Using the alternative matching algorithm provides the following advan- + Using the alternative matching algorithm provides the following advan- tages: 1. All possible matches (at a single point in the subject) are automat- - ically found, and in particular, the longest match is found. To find + ically found, and in particular, the longest match is found. To find more than one match using the standard algorithm, you have to do kludgy things with callouts. - 2. Because the alternative algorithm scans the subject string just + 2. Because the alternative algorithm scans the subject string just once, and never needs to backtrack (except for lookbehinds), it is pos- - sible to pass very long subject strings to the matching function in + sible to pass very long subject strings to the matching function in several pieces, checking for partial matching each time. Although it is - possible to do multi-segment matching using the standard algorithm by - retaining partially matched substrings, it is more complicated. The - pcrepartial documentation gives details of partial matching and dis- + possible to do multi-segment matching using the standard algorithm by + retaining partially matched substrings, it is more complicated. The + pcrepartial documentation gives details of partial matching and dis- cusses multi-segment matching. @@ -1045,8 +1539,8 @@ DISADVANTAGES OF THE ALTERNATIVE ALGORITHM The alternative algorithm suffers from a number of disadvantages: - 1. It is substantially slower than the standard algorithm. This is - partly because it has to search for all possible matches, but is also + 1. It is substantially slower than the standard algorithm. This is + partly because it has to search for all possible matches, but is also because it is less susceptible to optimization. 2. Capturing parentheses and back references are not supported. @@ -1064,14 +1558,15 @@ AUTHOR REVISION - Last updated: 08 January 2012 + Last updated: 12 November 2013 Copyright (c) 1997-2012 University of Cambridge. ------------------------------------------------------------------------------ -PCREAPI(3) PCREAPI(3) +PCREAPI(3) Library Functions Manual PCREAPI(3) + NAME PCRE - Perl-compatible regular expressions @@ -1140,6 +1635,11 @@ PCRE NATIVE API STRING EXTRACTION FUNCTIONS PCRE NATIVE API AUXILIARY FUNCTIONS + int pcre_jit_exec(const pcre *code, const pcre_extra *extra, + const char *subject, int length, int startoffset, + int options, int *ovector, int ovecsize, + pcre_jit_stack *jstack); + pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize); void pcre_jit_stack_free(pcre_jit_stack *stack); @@ -1175,70 +1675,76 @@ PCRE NATIVE API INDIRECTED FUNCTIONS int (*pcre_callout)(pcre_callout_block *); -PCRE 8-BIT AND 16-BIT LIBRARIES +PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES - From release 8.30, PCRE can be compiled as a library for handling - 16-bit character strings as well as, or instead of, the original - library that handles 8-bit character strings. To avoid too much compli- - cation, this document describes the 8-bit versions of the functions, - with only occasional references to the 16-bit library. + As well as support for 8-bit character strings, PCRE also supports + 16-bit strings (from release 8.30) and 32-bit strings (from release + 8.32), by means of two additional libraries. They can be built as well + as, or instead of, the 8-bit library. To avoid too much complication, + this document describes the 8-bit versions of the functions, with only + occasional references to the 16-bit and 32-bit libraries. - The 16-bit functions operate in the same way as their 8-bit counter- - parts; they just use different data types for their arguments and - results, and their names start with pcre16_ instead of pcre_. For every - option that has UTF8 in its name (for example, PCRE_UTF8), there is a - corresponding 16-bit name with UTF8 replaced by UTF16. This facility is - in fact just cosmetic; the 16-bit option names define the same bit val- + The 16-bit and 32-bit functions operate in the same way as their 8-bit + counterparts; they just use different data types for their arguments + and results, and their names start with pcre16_ or pcre32_ instead of + pcre_. For every option that has UTF8 in its name (for example, + PCRE_UTF8), there are corresponding 16-bit and 32-bit names with UTF8 + replaced by UTF16 or UTF32, respectively. This facility is in fact just + cosmetic; the 16-bit and 32-bit option names define the same bit val- ues. References to bytes and UTF-8 in this document should be read as refer- - ences to 16-bit data quantities and UTF-16 when using the 16-bit - library, unless specified otherwise. More details of the specific dif- - ferences for the 16-bit library are given in the pcre16 page. + ences to 16-bit data units and UTF-16 when using the 16-bit library, or + 32-bit data units and UTF-32 when using the 32-bit library, unless + specified otherwise. More details of the specific differences for the + 16-bit and 32-bit libraries are given in the pcre16 and pcre32 pages. PCRE API OVERVIEW PCRE has its own native API, which is described in this document. There - are also some wrapper functions (for the 8-bit library only) that cor- - respond to the POSIX regular expression API, but they do not give - access to all the functionality. They are described in the pcreposix - documentation. Both of these APIs define a set of C function calls. A + are also some wrapper functions (for the 8-bit library only) that cor- + respond to the POSIX regular expression API, but they do not give + access to all the functionality. They are described in the pcreposix + documentation. Both of these APIs define a set of C function calls. A C++ wrapper (again for the 8-bit library only) is also distributed with PCRE. It is documented in the pcrecpp page. - The native API C function prototypes are defined in the header file - pcre.h, and on Unix-like systems the (8-bit) library itself is called - libpcre. It can normally be accessed by adding -lpcre to the command - for linking an application that uses PCRE. The header file defines the + The native API C function prototypes are defined in the header file + pcre.h, and on Unix-like systems the (8-bit) library itself is called + libpcre. It can normally be accessed by adding -lpcre to the command + for linking an application that uses PCRE. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release - numbers for the library. Applications can use these to include support + numbers for the library. Applications can use these to include support for different releases of PCRE. In a Windows environment, if you want to statically link an application - program against a non-dll pcre.a file, you must define PCRE_STATIC - before including pcre.h or pcrecpp.h, because otherwise the pcre_mal- + program against a non-dll pcre.a file, you must define PCRE_STATIC + before including pcre.h or pcrecpp.h, because otherwise the pcre_mal- loc() and pcre_free() exported functions will be declared __declspec(dllimport), with unwanted results. - The functions pcre_compile(), pcre_compile2(), pcre_study(), and - pcre_exec() are used for compiling and matching regular expressions in - a Perl-compatible manner. A sample program that demonstrates the sim- - plest way of using them is provided in the file called pcredemo.c in + The functions pcre_compile(), pcre_compile2(), pcre_study(), and + pcre_exec() are used for compiling and matching regular expressions in + a Perl-compatible manner. A sample program that demonstrates the sim- + plest way of using them is provided in the file called pcredemo.c in the PCRE source distribution. A listing of this program is given in the - pcredemo documentation, and the pcresample documentation describes how + pcredemo documentation, and the pcresample documentation describes how to compile and run it. - Just-in-time compiler support is an optional feature of PCRE that can + Just-in-time compiler support is an optional feature of PCRE that can be built in appropriate hardware environments. It greatly speeds up the - matching performance of many patterns. Simple programs can easily - request that it be used if available, by setting an option that is - ignored when it is not relevant. More complicated programs might need - to make use of the functions pcre_jit_stack_alloc(), - pcre_jit_stack_free(), and pcre_assign_jit_stack() in order to control - the JIT code's memory usage. These functions are discussed in the - pcrejit documentation. + matching performance of many patterns. Simple programs can easily + request that it be used if available, by setting an option that is + ignored when it is not relevant. More complicated programs might need + to make use of the functions pcre_jit_stack_alloc(), + pcre_jit_stack_free(), and pcre_assign_jit_stack() in order to control + the JIT code's memory usage. + From release 8.32 there is also a direct interface for JIT execution, + which gives improved performance. The JIT-specific functions are dis- + cussed in the pcrejit documentation. + A second matching function, pcre_dfa_exec(), which is not Perl-compati- ble, is also provided. This uses a different algorithm for the match- ing. The alternative algorithm finds all possible matches (at a given @@ -1384,21 +1890,30 @@ CHECKING BUILD-TIME OPTIONS PCRE_CONFIG_UTF8 The output is an integer that is set to one if UTF-8 support is avail- - able; otherwise it is set to zero. If this option is given to the - 16-bit version of this function, pcre16_config(), the result is + able; otherwise it is set to zero. This value should normally be given + to the 8-bit version of this function, pcre_config(). If it is given to + the 16-bit or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION. PCRE_CONFIG_UTF16 The output is an integer that is set to one if UTF-16 support is avail- - able; otherwise it is set to zero. This value should normally be given + able; otherwise it is set to zero. This value should normally be given to the 16-bit version of this function, pcre16_config(). If it is given - to the 8-bit version of this function, the result is PCRE_ERROR_BADOP- - TION. + to the 8-bit or 32-bit version of this function, the result is + PCRE_ERROR_BADOPTION. + PCRE_CONFIG_UTF32 + + The output is an integer that is set to one if UTF-32 support is avail- + able; otherwise it is set to zero. This value should normally be given + to the 32-bit version of this function, pcre32_config(). If it is given + to the 8-bit or 16-bit version of this function, the result is + PCRE_ERROR_BADOPTION. + PCRE_CONFIG_UNICODE_PROPERTIES - The output is an integer that is set to one if support for Unicode + The output is an integer that is set to one if support for Unicode character properties is available; otherwise it is set to zero. PCRE_CONFIG_JIT @@ -1408,39 +1923,42 @@ CHECKING BUILD-TIME OPTIONS PCRE_CONFIG_JITTARGET - The output is a pointer to a zero-terminated "const char *" string. If + The output is a pointer to a zero-terminated "const char *" string. If JIT support is available, the string contains the name of the architec- - ture for which the JIT compiler is configured, for example "x86 32bit - (little endian + unaligned)". If JIT support is not available, the + ture for which the JIT compiler is configured, for example "x86 32bit + (little endian + unaligned)". If JIT support is not available, the result is NULL. PCRE_CONFIG_NEWLINE - The output is an integer whose value specifies the default character - sequence that is recognized as meaning "newline". The four values that - are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, - and -1 for ANY. Though they are derived from ASCII, the same values - are returned in EBCDIC environments. The default should normally corre- + The output is an integer whose value specifies the default character + sequence that is recognized as meaning "newline". The values that are + supported in ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338 + for CRLF, -2 for ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, + ANYCRLF, and ANY yield the same values. However, the value for LF is + normally 21, though some EBCDIC environments use 37. The corresponding + values for CRLF are 3349 and 3365. The default should normally corre- spond to the standard sequence for your operating system. PCRE_CONFIG_BSR The output is an integer whose value indicates what character sequences - the \R escape sequence matches by default. A value of 0 means that \R - matches any Unicode line ending sequence; a value of 1 means that \R + the \R escape sequence matches by default. A value of 0 means that \R + matches any Unicode line ending sequence; a value of 1 means that \R matches only CR, LF, or CRLF. The default can be overridden when a pat- tern is compiled or matched. PCRE_CONFIG_LINK_SIZE - The output is an integer that contains the number of bytes used for + The output is an integer that contains the number of bytes used for internal linkage in compiled regular expressions. For the 8-bit library, the value can be 2, 3, or 4. For the 16-bit library, the value - is either 2 or 4 and is still a number of bytes. The default value of 2 - is sufficient for all but the most massive patterns, since it allows - the compiled pattern to be up to 64K in size. Larger values allow - larger regular expressions to be compiled, at the expense of slower - matching. + is either 2 or 4 and is still a number of bytes. For the 32-bit + library, the value is either 2 or 4 and is still a number of bytes. The + default value of 2 is sufficient for all but the most massive patterns, + since it allows the compiled pattern to be up to 64K in size. Larger + values allow larger regular expressions to be compiled, at the expense + of slower matching. PCRE_CONFIG_POSIX_MALLOC_THRESHOLD @@ -1448,27 +1966,34 @@ CHECKING BUILD-TIME OPTIONS POSIX interface uses malloc() for output vectors. Further details are given in the pcreposix documentation. + PCRE_CONFIG_PARENS_LIMIT + + The output is a long integer that gives the maximum depth of nesting of + parentheses (of any kind) in a pattern. This limit is imposed to cap + the amount of system stack used when a pattern is compiled. It is spec- + ified when PCRE is built; the default is 250. + PCRE_CONFIG_MATCH_LIMIT - The output is a long integer that gives the default limit for the num- - ber of internal matching function calls in a pcre_exec() execution. + The output is a long integer that gives the default limit for the num- + ber of internal matching function calls in a pcre_exec() execution. Further details are given with pcre_exec() below. PCRE_CONFIG_MATCH_LIMIT_RECURSION The output is a long integer that gives the default limit for the depth - of recursion when calling the internal matching function in a - pcre_exec() execution. Further details are given with pcre_exec() + of recursion when calling the internal matching function in a + pcre_exec() execution. Further details are given with pcre_exec() below. PCRE_CONFIG_STACKRECURSE - The output is an integer that is set to one if internal recursion when + The output is an integer that is set to one if internal recursion when running pcre_exec() is implemented by recursive function calls that use - the stack to remember their state. This is the usual way that PCRE is + the stack to remember their state. This is the usual way that PCRE is compiled. The output is zero if PCRE was compiled to use blocks of data - on the heap instead of recursive function calls. In this case, - pcre_stack_malloc and pcre_stack_free are called to manage memory + on the heap instead of recursive function calls. In this case, + pcre_stack_malloc and pcre_stack_free are called to manage memory blocks on the heap, thus avoiding the use of the stack. @@ -1485,65 +2010,67 @@ COMPILING A PATTERN Either of the functions pcre_compile() or pcre_compile2() can be called to compile a pattern into an internal form. The only difference between - the two interfaces is that pcre_compile2() has an additional argument, - errorcodeptr, via which a numerical error code can be returned. To - avoid too much repetition, we refer just to pcre_compile() below, but + the two interfaces is that pcre_compile2() has an additional argument, + errorcodeptr, via which a numerical error code can be returned. To + avoid too much repetition, we refer just to pcre_compile() below, but the information applies equally to pcre_compile2(). The pattern is a C string terminated by a binary zero, and is passed in - the pattern argument. A pointer to a single block of memory that is - obtained via pcre_malloc is returned. This contains the compiled code + the pattern argument. A pointer to a single block of memory that is + obtained via pcre_malloc is returned. This contains the compiled code and related data. The pcre type is defined for the returned block; this is a typedef for a structure whose contents are not externally defined. It is up to the caller to free the memory (via pcre_free) when it is no longer required. - Although the compiled code of a PCRE regex is relocatable, that is, it + Although the compiled code of a PCRE regex is relocatable, that is, it does not depend on memory location, the complete pcre data block is not - fully relocatable, because it may contain a copy of the tableptr argu- + fully relocatable, because it may contain a copy of the tableptr argu- ment, which is an address (see below). The options argument contains various bit settings that affect the com- - pilation. It should be zero if no options are required. The available - options are described below. Some of them (in particular, those that - are compatible with Perl, but some others as well) can also be set and - unset from within the pattern (see the detailed description in the - pcrepattern documentation). For those options that can be different in - different parts of the pattern, the contents of the options argument + pilation. It should be zero if no options are required. The available + options are described below. Some of them (in particular, those that + are compatible with Perl, but some others as well) can also be set and + unset from within the pattern (see the detailed description in the + pcrepattern documentation). For those options that can be different in + different parts of the pattern, the contents of the options argument specifies their settings at the start of compilation and execution. The - PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and - PCRE_NO_START_OPTIMIZE options can be set at the time of matching as + PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and + PCRE_NO_START_OPTIMIZE options can be set at the time of matching as well as at compile time. If errptr is NULL, pcre_compile() returns NULL immediately. Otherwise, - if compilation of a pattern fails, pcre_compile() returns NULL, and + if compilation of a pattern fails, pcre_compile() returns NULL, and sets the variable pointed to by errptr to point to a textual error mes- sage. This is a static string that is part of the library. You must not - try to free it. Normally, the offset from the start of the pattern to - the byte that was being processed when the error was discovered is - placed in the variable pointed to by erroffset, which must not be NULL - (if it is, an immediate error is given). However, for an invalid UTF-8 - string, the offset is that of the first byte of the failing character. + try to free it. Normally, the offset from the start of the pattern to + the data unit that was being processed when the error was discovered is + placed in the variable pointed to by erroffset, which must not be NULL + (if it is, an immediate error is given). However, for an invalid UTF-8 + or UTF-16 string, the offset is that of the first data unit of the + failing character. Some errors are not detected until the whole pattern has been scanned; in these cases, the offset passed back is the length of the pattern. - Note that the offset is in bytes, not characters, even in UTF-8 mode. - It may sometimes point into the middle of a UTF-8 character. + Note that the offset is in data units, not characters, even in a UTF + mode. It may sometimes point into the middle of a UTF-8 or UTF-16 char- + acter. - If pcre_compile2() is used instead of pcre_compile(), and the error- - codeptr argument is not NULL, a non-zero error code number is returned - via this argument in the event of an error. This is in addition to the + If pcre_compile2() is used instead of pcre_compile(), and the error- + codeptr argument is not NULL, a non-zero error code number is returned + via this argument in the event of an error. This is in addition to the textual error message. Error codes and messages are listed below. - If the final argument, tableptr, is NULL, PCRE uses a default set of - character tables that are built when PCRE is compiled, using the - default C locale. Otherwise, tableptr must be an address that is the - result of a call to pcre_maketables(). This value is stored with the - compiled pattern, and used again by pcre_exec(), unless another table - pointer is passed to it. For more discussion, see the section on locale - support below. + If the final argument, tableptr, is NULL, PCRE uses a default set of + character tables that are built when PCRE is compiled, using the + default C locale. Otherwise, tableptr must be an address that is the + result of a call to pcre_maketables(). This value is stored with the + compiled pattern, and used again by pcre_exec() and pcre_dfa_exec() + when the pattern is matched. For more discussion, see the section on + locale support below. - This code fragment shows a typical straightforward call to pcre_com- + This code fragment shows a typical straightforward call to pcre_com- pile(): pcre *re; @@ -1556,154 +2083,167 @@ COMPILING A PATTERN &erroffset, /* for error offset */ NULL); /* use default character tables */ - The following names for option bits are defined in the pcre.h header + The following names for option bits are defined in the pcre.h header file: PCRE_ANCHORED If this bit is set, the pattern is forced to be "anchored", that is, it - is constrained to match only at the first matching point in the string - that is being searched (the "subject string"). This effect can also be - achieved by appropriate constructs in the pattern itself, which is the + is constrained to match only at the first matching point in the string + that is being searched (the "subject string"). This effect can also be + achieved by appropriate constructs in the pattern itself, which is the only way to do it in Perl. PCRE_AUTO_CALLOUT If this bit is set, pcre_compile() automatically inserts callout items, - all with number 255, before each pattern item. For discussion of the + all with number 255, before each pattern item. For discussion of the callout facility, see the pcrecallout documentation. PCRE_BSR_ANYCRLF PCRE_BSR_UNICODE These options (which are mutually exclusive) control what the \R escape - sequence matches. The choice is either to match only CR, LF, or CRLF, + sequence matches. The choice is either to match only CR, LF, or CRLF, or to match any Unicode newline sequence. The default is specified when PCRE is built. It can be overridden from within the pattern, or by set- ting an option when a compiled pattern is matched. PCRE_CASELESS - If this bit is set, letters in the pattern match both upper and lower - case letters. It is equivalent to Perl's /i option, and it can be - changed within a pattern by a (?i) option setting. In UTF-8 mode, PCRE - always understands the concept of case for characters whose values are - less than 128, so caseless matching is always possible. For characters - with higher values, the concept of case is supported if PCRE is com- - piled with Unicode property support, but not otherwise. If you want to - use caseless matching for characters 128 and above, you must ensure - that PCRE is compiled with Unicode property support as well as with + If this bit is set, letters in the pattern match both upper and lower + case letters. It is equivalent to Perl's /i option, and it can be + changed within a pattern by a (?i) option setting. In UTF-8 mode, PCRE + always understands the concept of case for characters whose values are + less than 128, so caseless matching is always possible. For characters + with higher values, the concept of case is supported if PCRE is com- + piled with Unicode property support, but not otherwise. If you want to + use caseless matching for characters 128 and above, you must ensure + that PCRE is compiled with Unicode property support as well as with UTF-8 support. PCRE_DOLLAR_ENDONLY - If this bit is set, a dollar metacharacter in the pattern matches only - at the end of the subject string. Without this option, a dollar also - matches immediately before a newline at the end of the string (but not - before any other newlines). The PCRE_DOLLAR_ENDONLY option is ignored - if PCRE_MULTILINE is set. There is no equivalent to this option in + If this bit is set, a dollar metacharacter in the pattern matches only + at the end of the subject string. Without this option, a dollar also + matches immediately before a newline at the end of the string (but not + before any other newlines). The PCRE_DOLLAR_ENDONLY option is ignored + if PCRE_MULTILINE is set. There is no equivalent to this option in Perl, and no way to set it within a pattern. PCRE_DOTALL - If this bit is set, a dot metacharacter in the pattern matches a char- + If this bit is set, a dot metacharacter in the pattern matches a char- acter of any value, including one that indicates a newline. However, it - only ever matches one character, even if newlines are coded as CRLF. - Without this option, a dot does not match when the current position is + only ever matches one character, even if newlines are coded as CRLF. + Without this option, a dot does not match when the current position is at a newline. This option is equivalent to Perl's /s option, and it can - be changed within a pattern by a (?s) option setting. A negative class + be changed within a pattern by a (?s) option setting. A negative class such as [^a] always matches newline characters, independent of the set- ting of this option. PCRE_DUPNAMES - If this bit is set, names used to identify capturing subpatterns need + If this bit is set, names used to identify capturing subpatterns need not be unique. This can be helpful for certain types of pattern when it - is known that only one instance of the named subpattern can ever be - matched. There are more details of named subpatterns below; see also + is known that only one instance of the named subpattern can ever be + matched. There are more details of named subpatterns below; see also the pcrepattern documentation. PCRE_EXTENDED - If this bit is set, white space data characters in the pattern are - totally ignored except when escaped or inside a character class. White - space does not include the VT character (code 11). In addition, charac- - ters between an unescaped # outside a character class and the next new- - line, inclusive, are also ignored. This is equivalent to Perl's /x - option, and it can be changed within a pattern by a (?x) option set- - ting. + If this bit is set, most white space characters in the pattern are + totally ignored except when escaped or inside a character class. How- + ever, white space is not allowed within sequences such as (?> that + introduce various parenthesized subpatterns, nor within a numerical + quantifier such as {1,3}. However, ignorable white space is permitted + between an item and a following quantifier and between a quantifier and + a following + that indicates possessiveness. - Which characters are interpreted as newlines is controlled by the - options passed to pcre_compile() or by a special sequence at the start - of the pattern, as described in the section entitled "Newline conven- + White space did not used to include the VT character (code 11), because + Perl did not treat this character as white space. However, Perl changed + at release 5.18, so PCRE followed at release 8.34, and VT is now + treated as white space. + + PCRE_EXTENDED also causes characters between an unescaped # outside a + character class and the next newline, inclusive, to be ignored. + PCRE_EXTENDED is equivalent to Perl's /x option, and it can be changed + within a pattern by a (?x) option setting. + + Which characters are interpreted as newlines is controlled by the + options passed to pcre_compile() or by a special sequence at the start + of the pattern, as described in the section entitled "Newline conven- tions" in the pcrepattern documentation. Note that the end of this type - of comment is a literal newline sequence in the pattern; escape + of comment is a literal newline sequence in the pattern; escape sequences that happen to represent a newline do not count. - This option makes it possible to include comments inside complicated - patterns. Note, however, that this applies only to data characters. - White space characters may never appear within special character + This option makes it possible to include comments inside complicated + patterns. Note, however, that this applies only to data characters. + White space characters may never appear within special character sequences in a pattern, for example within the sequence (?( that intro- duces a conditional subpattern. PCRE_EXTRA - This option was invented in order to turn on additional functionality - of PCRE that is incompatible with Perl, but it is currently of very - little use. When set, any backslash in a pattern that is followed by a - letter that has no special meaning causes an error, thus reserving - these combinations for future expansion. By default, as in Perl, a - backslash followed by a letter with no special meaning is treated as a + This option was invented in order to turn on additional functionality + of PCRE that is incompatible with Perl, but it is currently of very + little use. When set, any backslash in a pattern that is followed by a + letter that has no special meaning causes an error, thus reserving + these combinations for future expansion. By default, as in Perl, a + backslash followed by a letter with no special meaning is treated as a literal. (Perl can, however, be persuaded to give an error for this, by - running it with the -w option.) There are at present no other features - controlled by this option. It can also be set by a (?X) option setting + running it with the -w option.) There are at present no other features + controlled by this option. It can also be set by a (?X) option setting within a pattern. PCRE_FIRSTLINE - If this option is set, an unanchored pattern is required to match - before or at the first newline in the subject string, though the + If this option is set, an unanchored pattern is required to match + before or at the first newline in the subject string, though the matched text may continue over the newline. PCRE_JAVASCRIPT_COMPAT If this option is set, PCRE's behaviour is changed in some ways so that - it is compatible with JavaScript rather than Perl. The changes are as + it is compatible with JavaScript rather than Perl. The changes are as follows: - (1) A lone closing square bracket in a pattern causes a compile-time - error, because this is illegal in JavaScript (by default it is treated + (1) A lone closing square bracket in a pattern causes a compile-time + error, because this is illegal in JavaScript (by default it is treated as a data character). Thus, the pattern AB]CD becomes illegal when this option is set. - (2) At run time, a back reference to an unset subpattern group matches - an empty string (by default this causes the current matching alterna- - tive to fail). A pattern such as (\1)(a) succeeds when this option is - set (assuming it can find an "a" in the subject), whereas it fails by + (2) At run time, a back reference to an unset subpattern group matches + an empty string (by default this causes the current matching alterna- + tive to fail). A pattern such as (\1)(a) succeeds when this option is + set (assuming it can find an "a" in the subject), whereas it fails by default, for Perl compatibility. (3) \U matches an upper case "U" character; by default \U causes a com- pile time error (Perl uses \U to upper case subsequent characters). (4) \u matches a lower case "u" character unless it is followed by four - hexadecimal digits, in which case the hexadecimal number defines the - code point to match. By default, \u causes a compile time error (Perl + hexadecimal digits, in which case the hexadecimal number defines the + code point to match. By default, \u causes a compile time error (Perl uses it to upper case the following character). - (5) \x matches a lower case "x" character unless it is followed by two - hexadecimal digits, in which case the hexadecimal number defines the - code point to match. By default, as in Perl, a hexadecimal number is + (5) \x matches a lower case "x" character unless it is followed by two + hexadecimal digits, in which case the hexadecimal number defines the + code point to match. By default, as in Perl, a hexadecimal number is always expected after \x, but it may have zero, one, or two digits (so, for example, \xz matches a binary zero character followed by z). PCRE_MULTILINE - By default, PCRE treats the subject string as consisting of a single - line of characters (even if it actually contains newlines). The "start - of line" metacharacter (^) matches only at the start of the string, - while the "end of line" metacharacter ($) matches only at the end of - the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY - is set). This is the same as Perl. + By default, for the purposes of matching "start of line" and "end of + line", PCRE treats the subject string as consisting of a single line of + characters, even if it actually contains newlines. The "start of line" + metacharacter (^) matches only at the start of the string, and the "end + of line" metacharacter ($) matches only at the end of the string, or + before a terminating newline (except when PCRE_DOLLAR_ENDONLY is set). + Note, however, that unless PCRE_DOTALL is set, the "any character" + metacharacter (.) does not match at a newline. This behaviour (for ^, + $, and dot) is the same as Perl. When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs match immediately following or immediately before internal @@ -1713,25 +2253,43 @@ COMPILING A PATTERN lines in a subject string, or no occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect. + PCRE_NEVER_UTF + + This option locks out interpretation of the pattern as UTF-8 (or UTF-16 + or UTF-32 in the 16-bit and 32-bit libraries). In particular, it pre- + vents the creator of the pattern from switching to UTF interpretation + by starting the pattern with (*UTF). This may be useful in applications + that process patterns from external sources. The combination of + PCRE_UTF8 and PCRE_NEVER_UTF also causes an error. + PCRE_NEWLINE_CR PCRE_NEWLINE_LF PCRE_NEWLINE_CRLF PCRE_NEWLINE_ANYCRLF PCRE_NEWLINE_ANY - These options override the default newline definition that was chosen - when PCRE was built. Setting the first or the second specifies that a - newline is indicated by a single character (CR or LF, respectively). - Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by the - two-character CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies + These options override the default newline definition that was chosen + when PCRE was built. Setting the first or the second specifies that a + newline is indicated by a single character (CR or LF, respectively). + Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by the + two-character CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three preceding sequences should be recognized. Setting - PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should be - recognized. The Unicode newline sequences are the three just mentioned, - plus the single characters VT (vertical tab, U+000B), FF (form feed, - U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS - (paragraph separator, U+2029). For the 8-bit library, the last two are - recognized only in UTF-8 mode. + PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should be + recognized. + In an ASCII/Unicode environment, the Unicode newline sequences are the + three just mentioned, plus the single characters VT (vertical tab, + U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line sep- + arator, U+2028), and PS (paragraph separator, U+2029). For the 8-bit + library, the last two are recognized only in UTF-8 mode. + + When PCRE is compiled to run in an EBCDIC (mainframe) environment, the + code for CR is 0x0d, the same as ASCII. However, the character code for + LF is normally 0x15, though in some EBCDIC environments 0x25 is used. + Whichever of these is not LF is made to correspond to Unicode's NEL + character. EBCDIC codes are all less than 256. For more details, see + the pcrebuild documentation. + The newline setting in the options word uses three bits that are treated as a number, giving eight possibilities. Currently only six are used (default plus the five values above). This means that if you set @@ -1758,62 +2316,75 @@ COMPILING A PATTERN be used for capturing (and they acquire numbers in the usual way). There is no equivalent of this option in Perl. - NO_START_OPTIMIZE + PCRE_NO_AUTO_POSSESS + If this option is set, it disables "auto-possessification". This is an + optimization that, for example, turns a+b into a++b in order to avoid + backtracks into a+ that can never be successful. However, if callouts + are in use, auto-possessification means that some of them are never + taken. You can set this option if you want the matching functions to do + a full unoptimized search and run all the callouts, but it is mainly + provided for testing purposes. + + PCRE_NO_START_OPTIMIZE + This is an option that acts at matching time; that is, it is really an option for pcre_exec() or pcre_dfa_exec(). If it is set at compile time, it is remembered with the compiled pattern and assumed at match- - ing time. For details see the discussion of PCRE_NO_START_OPTIMIZE - below. + ing time. This is necessary if you want to use JIT execution, because + the JIT compiler needs to know whether or not this option is set. For + details see the discussion of PCRE_NO_START_OPTIMIZE below. PCRE_UCP - This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W, - \w, and some of the POSIX character classes. By default, only ASCII - characters are recognized, but if PCRE_UCP is set, Unicode properties - are used instead to classify characters. More details are given in the - section on generic character types in the pcrepattern page. If you set - PCRE_UCP, matching one of the items it affects takes much longer. The - option is available only if PCRE has been compiled with Unicode prop- + This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W, + \w, and some of the POSIX character classes. By default, only ASCII + characters are recognized, but if PCRE_UCP is set, Unicode properties + are used instead to classify characters. More details are given in the + section on generic character types in the pcrepattern page. If you set + PCRE_UCP, matching one of the items it affects takes much longer. The + option is available only if PCRE has been compiled with Unicode prop- erty support. PCRE_UNGREEDY - This option inverts the "greediness" of the quantifiers so that they - are not greedy by default, but become greedy if followed by "?". It is - not compatible with Perl. It can also be set by a (?U) option setting + This option inverts the "greediness" of the quantifiers so that they + are not greedy by default, but become greedy if followed by "?". It is + not compatible with Perl. It can also be set by a (?U) option setting within the pattern. PCRE_UTF8 - This option causes PCRE to regard both the pattern and the subject as + This option causes PCRE to regard both the pattern and the subject as strings of UTF-8 characters instead of single-byte strings. However, it - is available only when PCRE is built to include UTF support. If not, - the use of this option provokes an error. Details of how this option + is available only when PCRE is built to include UTF support. If not, + the use of this option provokes an error. Details of how this option changes the behaviour of PCRE are given in the pcreunicode page. PCRE_NO_UTF8_CHECK When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is - automatically checked. There is a discussion about the validity of - UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence is - found, pcre_compile() returns an error. If you already know that your - pattern is valid, and you want to skip this check for performance rea- - sons, you can set the PCRE_NO_UTF8_CHECK option. When it is set, the + automatically checked. There is a discussion about the validity of + UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence is + found, pcre_compile() returns an error. If you already know that your + pattern is valid, and you want to skip this check for performance rea- + sons, you can set the PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid UTF-8 string as a pattern is undefined. It - may cause your program to crash. Note that this option can also be - passed to pcre_exec() and pcre_dfa_exec(), to suppress the validity - checking of subject strings. + may cause your program to crash or loop. Note that this option can also + be passed to pcre_exec() and pcre_dfa_exec(), to suppress the validity + checking of subject strings only. If the same string is being matched + many times, the option can be safely set for the second and subsequent + matchings to improve performance. COMPILATION ERROR CODES - The following table lists the error codes than may be returned by - pcre_compile2(), along with the error messages that may be returned by - both compiling functions. Note that error messages are always 8-bit - ASCII strings, even in 16-bit mode. As PCRE has developed, some error - codes have fallen out of use. To avoid confusion, they have not been - re-used. + The following table lists the error codes than may be returned by + pcre_compile2(), along with the error messages that may be returned by + both compiling functions. Note that error messages are always 8-bit + ASCII strings, even in 16-bit or 32-bit mode. As PCRE has developed, + some error codes have fallen out of use. To avoid confusion, they have + not been re-used. 0 no error 1 \ at end of pattern @@ -1849,7 +2420,7 @@ COMPILATION ERROR CODES 31 POSIX collating elements are not supported 32 this version of PCRE is compiled without UTF support 33 [this code is not in use] - 34 character value in \x{...} sequence is too large + 34 character value in \x{} or \o{} is too large 35 invalid condition (?(0) 36 \C not allowed in lookbehind assertion 37 PCRE does not support \L, \l, \N{name}, \U, or \u @@ -1877,7 +2448,7 @@ COMPILATION ERROR CODES name/number or by a plain number 58 a numbered reference must not be zero 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT) - 60 (*VERB) not recognized + 60 (*VERB) not recognized or malformed 61 number is too big 62 subpattern name expected 63 digit expected after (?+ @@ -1896,70 +2467,81 @@ COMPILATION ERROR CODES 74 invalid UTF-16 string (specifically UTF-16) 75 name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN) 76 character value in \u.... sequence is too large + 77 invalid UTF-32 string (specifically UTF-32) + 78 setting UTF is disabled by the application + 79 non-hex character in \x{} (closing brace missing?) + 80 non-octal character in \o{} (closing brace missing?) + 81 missing opening brace after \o + 82 parentheses are too deeply nested + 83 invalid range in character class - The numbers 32 and 10000 in errors 48 and 49 are defaults; different + The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may be used if the limits were changed when PCRE was built. STUDYING A PATTERN - pcre_extra *pcre_study(const pcre *code, int options + pcre_extra *pcre_study(const pcre *code, int options, const char **errptr); - If a compiled pattern is going to be used several times, it is worth + If a compiled pattern is going to be used several times, it is worth spending more time analyzing it in order to speed up the time taken for - matching. The function pcre_study() takes a pointer to a compiled pat- + matching. The function pcre_study() takes a pointer to a compiled pat- tern as its first argument. If studying the pattern produces additional - information that will help speed up matching, pcre_study() returns a - pointer to a pcre_extra block, in which the study_data field points to + information that will help speed up matching, pcre_study() returns a + pointer to a pcre_extra block, in which the study_data field points to the results of the study. The returned value from pcre_study() can be passed directly to - pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block also con- - tains other fields that can be set by the caller before the block is + pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block also con- + tains other fields that can be set by the caller before the block is passed; these are described below in the section on matching a pattern. - If studying the pattern does not produce any useful information, - pcre_study() returns NULL. In that circumstance, if the calling program - wants to pass any of the other fields to pcre_exec() or - pcre_dfa_exec(), it must set up its own pcre_extra block. + If studying the pattern does not produce any useful information, + pcre_study() returns NULL by default. In that circumstance, if the + calling program wants to pass any of the other fields to pcre_exec() or + pcre_dfa_exec(), it must set up its own pcre_extra block. However, if + pcre_study() is called with the PCRE_STUDY_EXTRA_NEEDED option, it + returns a pcre_extra block even if studying did not find any additional + information. It may still return NULL, however, if an error occurs in + pcre_study(). - The second argument of pcre_study() contains option bits. There are - three options: + The second argument of pcre_study() contains option bits. There are + three further options in addition to PCRE_STUDY_EXTRA_NEEDED: PCRE_STUDY_JIT_COMPILE PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE - If any of these are set, and the just-in-time compiler is available, - the pattern is further compiled into machine code that executes much - faster than the pcre_exec() interpretive matching function. If the - just-in-time compiler is not available, these options are ignored. All - other bits in the options argument must be zero. + If any of these are set, and the just-in-time compiler is available, + the pattern is further compiled into machine code that executes much + faster than the pcre_exec() interpretive matching function. If the + just-in-time compiler is not available, these options are ignored. All + undefined bits in the options argument must be zero. - JIT compilation is a heavyweight optimization. It can take some time - for patterns to be analyzed, and for one-off matches and simple pat- - terns the benefit of faster execution might be offset by a much slower + JIT compilation is a heavyweight optimization. It can take some time + for patterns to be analyzed, and for one-off matches and simple pat- + terns the benefit of faster execution might be offset by a much slower study time. Not all patterns can be optimized by the JIT compiler. For - those that cannot be handled, matching automatically falls back to the - pcre_exec() interpreter. For more details, see the pcrejit documenta- + those that cannot be handled, matching automatically falls back to the + pcre_exec() interpreter. For more details, see the pcrejit documenta- tion. - The third argument for pcre_study() is a pointer for an error message. - If studying succeeds (even if no data is returned), the variable it - points to is set to NULL. Otherwise it is set to point to a textual + The third argument for pcre_study() is a pointer for an error message. + If studying succeeds (even if no data is returned), the variable it + points to is set to NULL. Otherwise it is set to point to a textual error message. This is a static string that is part of the library. You - must not try to free it. You should test the error pointer for NULL + must not try to free it. You should test the error pointer for NULL after calling pcre_study(), to be sure that it has run successfully. - When you are finished with a pattern, you can free the memory used for + When you are finished with a pattern, you can free the memory used for the study data by calling pcre_free_study(). This function was added to - the API for release 8.20. For earlier versions, the memory could be - freed with pcre_free(), just like the pattern itself. This will still - work in cases where JIT optimization is not used, but it is advisable + the API for release 8.20. For earlier versions, the memory could be + freed with pcre_free(), just like the pattern itself. This will still + work in cases where JIT optimization is not used, but it is advisable to change to the new function when convenient. - This is a typical way in which pcre_study() is used (except that in a + This is a typical way in which pcre_study() is used (except that in a real application there should be tests for errors): int rc; @@ -1979,83 +2561,97 @@ STUDYING A PATTERN Studying a pattern does two things: first, a lower bound for the length of subject string that is needed to match the pattern is computed. This does not mean that there are any strings of that length that match, but - it does guarantee that no shorter strings match. The value is used by - pcre_exec() and pcre_dfa_exec() to avoid wasting time by trying to - match strings that are shorter than the lower bound. You can find out - the value in a calling program via the pcre_fullinfo() function. + it does guarantee that no shorter strings match. The value is used to + avoid wasting time by trying to match strings that are shorter than the + lower bound. You can find out the value in a calling program via the + pcre_fullinfo() function. Studying a pattern is also useful for non-anchored patterns that do not - have a single fixed starting character. A bitmap of possible starting - bytes is created. This speeds up finding a position in the subject at + have a single fixed starting character. A bitmap of possible starting + bytes is created. This speeds up finding a position in the subject at which to start matching. (In 16-bit mode, the bitmap is used for 16-bit + values less than 256. In 32-bit mode, the bitmap is used for 32-bit values less than 256.) These two optimizations apply to both pcre_exec() and pcre_dfa_exec(), and the information is also used by the JIT compiler. The optimiza- - tions can be disabled by setting the PCRE_NO_START_OPTIMIZE option when - calling pcre_exec() or pcre_dfa_exec(), but if this is done, JIT execu- - tion is also disabled. You might want to do this if your pattern con- - tains callouts or (*MARK) and you want to make use of these facilities - in cases where matching fails. See the discussion of - PCRE_NO_START_OPTIMIZE below. + tions can be disabled by setting the PCRE_NO_START_OPTIMIZE option. + You might want to do this if your pattern contains callouts or (*MARK) + and you want to make use of these facilities in cases where matching + fails. + PCRE_NO_START_OPTIMIZE can be specified at either compile time or exe- + cution time. However, if PCRE_NO_START_OPTIMIZE is passed to + pcre_exec(), (that is, after any JIT compilation has happened) JIT exe- + cution is disabled. For JIT execution to work with PCRE_NO_START_OPTI- + MIZE, the option must be set at compile time. + There is a longer discussion of PCRE_NO_START_OPTIMIZE below. + + LOCALE SUPPORT PCRE handles caseless matching, and determines whether characters are letters, digits, or whatever, by reference to a set of tables, indexed - by character value. When running in UTF-8 mode, this applies only to - characters with codes less than 128. By default, higher-valued codes - never match escapes such as \w or \d, but they can be tested with \p if - PCRE is built with Unicode character property support. Alternatively, - the PCRE_UCP option can be set at compile time; this causes \w and - friends to use Unicode property support instead of built-in tables. The - use of locales with Unicode is discouraged. If you are handling charac- - ters with codes greater than 128, you should either use UTF-8 and Uni- - code, or use locales, but not try to mix the two. + by character code point. When running in UTF-8 mode, or in the 16- or + 32-bit libraries, this applies only to characters with code points less + than 256. By default, higher-valued code points never match escapes + such as \w or \d. However, if PCRE is built with Unicode property sup- + port, all characters can be tested with \p and \P, or, alternatively, + the PCRE_UCP option can be set when a pattern is compiled; this causes + \w and friends to use Unicode property support instead of the built-in + tables. - PCRE contains an internal set of tables that are used when the final - argument of pcre_compile() is NULL. These are sufficient for many + The use of locales with Unicode is discouraged. If you are handling + characters with code points greater than 128, you should either use + Unicode support, or use locales, but not try to mix the two. + + PCRE contains an internal set of tables that are used when the final + argument of pcre_compile() is NULL. These are sufficient for many applications. Normally, the internal tables recognize only ASCII char- acters. However, when PCRE is built, it is possible to cause the inter- nal tables to be rebuilt in the default "C" locale of the local system, which may cause them to be different. - The internal tables can always be overridden by tables supplied by the + The internal tables can always be overridden by tables supplied by the application that calls PCRE. These may be created in a different locale - from the default. As more and more applications change to using Uni- + from the default. As more and more applications change to using Uni- code, the need for this locale support is expected to die away. - External tables are built by calling the pcre_maketables() function, - which has no arguments, in the relevant locale. The result can then be - passed to pcre_compile() or pcre_exec() as often as necessary. For - example, to build and use tables that are appropriate for the French - locale (where accented characters with values greater than 128 are - treated as letters), the following code could be used: + External tables are built by calling the pcre_maketables() function, + which has no arguments, in the relevant locale. The result can then be + passed to pcre_compile() as often as necessary. For example, to build + and use tables that are appropriate for the French locale (where + accented characters with values greater than 128 are treated as let- + ters), the following code could be used: setlocale(LC_CTYPE, "fr_FR"); tables = pcre_maketables(); re = pcre_compile(..., tables); - The locale name "fr_FR" is used on Linux and other Unix-like systems; + The locale name "fr_FR" is used on Linux and other Unix-like systems; if you are using Windows, the name for the French locale is "french". - When pcre_maketables() runs, the tables are built in memory that is - obtained via pcre_malloc. It is the caller's responsibility to ensure - that the memory containing the tables remains available for as long as + When pcre_maketables() runs, the tables are built in memory that is + obtained via pcre_malloc. It is the caller's responsibility to ensure + that the memory containing the tables remains available for as long as it is needed. The pointer that is passed to pcre_compile() is saved with the compiled - pattern, and the same tables are used via this pointer by pcre_study() - and normally also by pcre_exec(). Thus, by default, for any single pat- + pattern, and the same tables are used via this pointer by pcre_study() + and also by pcre_exec() and pcre_dfa_exec(). Thus, for any single pat- tern, compilation, studying and matching all happen in the same locale, - but different patterns can be compiled in different locales. + but different patterns can be processed in different locales. - It is possible to pass a table pointer or NULL (indicating the use of - the internal tables) to pcre_exec(). Although not intended for this - purpose, this facility could be used to match a pattern in a different - locale from the one in which it was compiled. Passing table pointers at - run time is discussed below in the section on matching a pattern. + It is possible to pass a table pointer or NULL (indicating the use of + the internal tables) to pcre_exec() or pcre_dfa_exec() (see the discus- + sion below in the section on matching a pattern). This facility is pro- + vided for use with pre-compiled patterns that have been saved and + reloaded. Character tables are not saved with patterns, so if a non- + standard table was used at compile time, it must be provided again when + the reloaded pattern is matched. Attempting to use this facility to + match a pattern in a different locale from the one in which it was com- + piled is likely to lead to anomalous (usually incorrect) results. INFORMATION ABOUT A PATTERN @@ -2063,15 +2659,15 @@ INFORMATION ABOUT A PATTERN int pcre_fullinfo(const pcre *code, const pcre_extra *extra, int what, void *where); - The pcre_fullinfo() function returns information about a compiled pat- - tern. It replaces the pcre_info() function, which was removed from the + The pcre_fullinfo() function returns information about a compiled pat- + tern. It replaces the pcre_info() function, which was removed from the library at version 8.30, after more than 10 years of obsolescence. - The first argument for pcre_fullinfo() is a pointer to the compiled - pattern. The second argument is the result of pcre_study(), or NULL if - the pattern was not studied. The third argument specifies which piece - of information is required, and the fourth argument is a pointer to a - variable to receive the data. The yield of the function is zero for + The first argument for pcre_fullinfo() is a pointer to the compiled + pattern. The second argument is the result of pcre_study(), or NULL if + the pattern was not studied. The third argument specifies which piece + of information is required, and the fourth argument is a pointer to a + variable to receive the data. The yield of the function is zero for success, or one of the following negative numbers: PCRE_ERROR_NULL the argument code was NULL @@ -2080,11 +2676,12 @@ INFORMATION ABOUT A PATTERN PCRE_ERROR_BADENDIANNESS the pattern was compiled with different endianness PCRE_ERROR_BADOPTION the value of what was invalid + PCRE_ERROR_UNSET the requested field is not set - The "magic number" is placed at the start of each compiled pattern as - an simple check against passing an arbitrary memory pointer. The endi- + The "magic number" is placed at the start of each compiled pattern as + an simple check against passing an arbitrary memory pointer. The endi- anness error can occur if a compiled pattern is saved and reloaded on a - different host. Here is a typical call of pcre_fullinfo(), to obtain + different host. Here is a typical call of pcre_fullinfo(), to obtain the length of the compiled pattern: int rc; @@ -2095,39 +2692,40 @@ INFORMATION ABOUT A PATTERN PCRE_INFO_SIZE, /* what is required */ &length); /* where to put the data */ - The possible values for the third argument are defined in pcre.h, and + The possible values for the third argument are defined in pcre.h, and are as follows: PCRE_INFO_BACKREFMAX - Return the number of the highest back reference in the pattern. The - fourth argument should point to an int variable. Zero is returned if + Return the number of the highest back reference in the pattern. The + fourth argument should point to an int variable. Zero is returned if there are no back references. PCRE_INFO_CAPTURECOUNT - Return the number of capturing subpatterns in the pattern. The fourth + Return the number of capturing subpatterns in the pattern. The fourth argument should point to an int variable. PCRE_INFO_DEFAULT_TABLES - Return a pointer to the internal default character tables within PCRE. - The fourth argument should point to an unsigned char * variable. This + Return a pointer to the internal default character tables within PCRE. + The fourth argument should point to an unsigned char * variable. This information call is provided for internal use by the pcre_study() func- - tion. External callers can cause PCRE to use its internal tables by + tion. External callers can cause PCRE to use its internal tables by passing a NULL table pointer. PCRE_INFO_FIRSTBYTE Return information about the first data unit of any matched string, for - a non-anchored pattern. (The name of this option refers to the 8-bit - library, where data units are bytes.) The fourth argument should point + a non-anchored pattern. (The name of this option refers to the 8-bit + library, where data units are bytes.) The fourth argument should point to an int variable. - If there is a fixed first value, for example, the letter "c" from a - pattern such as (cat|cow|coyote), its value is returned. In the 8-bit - library, the value is always less than 256; in the 16-bit library the - value can be up to 0xffff. + If there is a fixed first value, for example, the letter "c" from a + pattern such as (cat|cow|coyote), its value is returned. In the 8-bit + library, the value is always less than 256. In the 16-bit library the + value can be up to 0xffff. In the 32-bit library the value can be up to + 0x10ffff. If there is no fixed first value, and if either @@ -2141,66 +2739,94 @@ INFORMATION ABOUT A PATTERN of a subject string or after any newline within the string. Otherwise -2 is returned. For anchored patterns, -2 is returned. + Since for the 32-bit library using the non-UTF-32 mode, this function + is unable to return the full 32-bit range of the character, this value + is deprecated; instead the PCRE_INFO_FIRSTCHARACTERFLAGS and + PCRE_INFO_FIRSTCHARACTER values should be used. + PCRE_INFO_FIRSTTABLE - If the pattern was studied, and this resulted in the construction of a - 256-bit table indicating a fixed set of values for the first data unit - in any matching string, a pointer to the table is returned. Otherwise - NULL is returned. The fourth argument should point to an unsigned char + If the pattern was studied, and this resulted in the construction of a + 256-bit table indicating a fixed set of values for the first data unit + in any matching string, a pointer to the table is returned. Otherwise + NULL is returned. The fourth argument should point to an unsigned char * variable. PCRE_INFO_HASCRORLF - Return 1 if the pattern contains any explicit matches for CR or LF - characters, otherwise 0. The fourth argument should point to an int - variable. An explicit match is either a literal CR or LF character, or + Return 1 if the pattern contains any explicit matches for CR or LF + characters, otherwise 0. The fourth argument should point to an int + variable. An explicit match is either a literal CR or LF character, or \r or \n. PCRE_INFO_JCHANGED - Return 1 if the (?J) or (?-J) option setting is used in the pattern, - otherwise 0. The fourth argument should point to an int variable. (?J) + Return 1 if the (?J) or (?-J) option setting is used in the pattern, + otherwise 0. The fourth argument should point to an int variable. (?J) and (?-J) set and unset the local PCRE_DUPNAMES option, respectively. PCRE_INFO_JIT - Return 1 if the pattern was studied with one of the JIT options, and + Return 1 if the pattern was studied with one of the JIT options, and just-in-time compiling was successful. The fourth argument should point - to an int variable. A return value of 0 means that JIT support is not - available in this version of PCRE, or that the pattern was not studied - with a JIT option, or that the JIT compiler could not handle this par- - ticular pattern. See the pcrejit documentation for details of what can + to an int variable. A return value of 0 means that JIT support is not + available in this version of PCRE, or that the pattern was not studied + with a JIT option, or that the JIT compiler could not handle this par- + ticular pattern. See the pcrejit documentation for details of what can and cannot be handled. PCRE_INFO_JITSIZE - If the pattern was successfully studied with a JIT option, return the - size of the JIT compiled code, otherwise return zero. The fourth argu- + If the pattern was successfully studied with a JIT option, return the + size of the JIT compiled code, otherwise return zero. The fourth argu- ment should point to a size_t variable. PCRE_INFO_LASTLITERAL - Return the value of the rightmost literal data unit that must exist in - any matched string, other than at its start, if such a value has been + Return the value of the rightmost literal data unit that must exist in + any matched string, other than at its start, if such a value has been recorded. The fourth argument should point to an int variable. If there is no such value, -1 is returned. For anchored patterns, a last literal - value is recorded only if it follows something of variable length. For + value is recorded only if it follows something of variable length. For example, for the pattern /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value is -1. + Since for the 32-bit library using the non-UTF-32 mode, this function + is unable to return the full 32-bit range of characters, this value is + deprecated; instead the PCRE_INFO_REQUIREDCHARFLAGS and + PCRE_INFO_REQUIREDCHAR values should be used. + + PCRE_INFO_MATCH_EMPTY + + Return 1 if the pattern can match an empty string, otherwise 0. The + fourth argument should point to an int variable. + + PCRE_INFO_MATCHLIMIT + + If the pattern set a match limit by including an item of the form + (*LIMIT_MATCH=nnnn) at the start, the value is returned. The fourth + argument should point to an unsigned 32-bit integer. If no such value + has been set, the call to pcre_fullinfo() returns the error + PCRE_ERROR_UNSET. + PCRE_INFO_MAXLOOKBEHIND - Return the number of characters (NB not bytes) in the longest lookbe- - hind assertion in the pattern. Note that the simple assertions \b and - \B require a one-character lookbehind. This information is useful when - doing multi-segment matching using the partial matching facilities. + Return the number of characters (NB not data units) in the longest + lookbehind assertion in the pattern. This information is useful when + doing multi-segment matching using the partial matching facilities. + Note that the simple assertions \b and \B require a one-character look- + behind. \A also registers a one-character lookbehind, though it does + not actually inspect the previous character. This is to ensure that at + least one character from the old segment is retained when a new segment + is processed. Otherwise, if there are no lookbehinds in the pattern, \A + might match incorrectly at the start of a new segment. PCRE_INFO_MINLENGTH If the pattern was studied and a minimum length for matching subject strings was computed, its value is returned. Otherwise the returned - value is -1. The value is a number of characters, which in UTF-8 mode - may be different from the number of bytes. The fourth argument should + value is -1. The value is a number of characters, which in UTF mode may + be different from the number of data units. The fourth argument should point to an int variable. A non-negative value is a lower bound to the length of any matching string. There may not be any strings of that length that do actually match, but every string that does match is at @@ -2228,28 +2854,31 @@ INFORMATION ABOUT A PATTERN the 8-bit library, where the first two bytes of each entry are the num- ber of the capturing parenthesis, most significant byte first. In the 16-bit library, the pointer points to 16-bit data units, the first of - which contains the parenthesis number. The rest of the entry is the - corresponding name, zero terminated. + which contains the parenthesis number. In the 32-bit library, the + pointer points to 32-bit data units, the first of which contains the + parenthesis number. The rest of the entry is the corresponding name, + zero terminated. - The names are in alphabetical order. Duplicate names may appear if (?| - is used to create multiple groups with the same number, as described in - the section on duplicate subpattern numbers in the pcrepattern page. - Duplicate names for subpatterns with different numbers are permitted - only if PCRE_DUPNAMES is set. In all cases of duplicate names, they - appear in the table in the order in which they were found in the pat- - tern. In the absence of (?| this is the order of increasing number; - when (?| is used this is not necessarily the case because later subpat- - terns may have lower numbers. + The names are in alphabetical order. If (?| is used to create multiple + groups with the same number, as described in the section on duplicate + subpattern numbers in the pcrepattern page, the groups may be given the + same name, but there is only one entry in the table. Different names + for groups of the same number are not permitted. Duplicate names for + subpatterns with different numbers are permitted, but only if PCRE_DUP- + NAMES is set. They appear in the table in the order in which they were + found in the pattern. In the absence of (?| this is the order of + increasing number; when (?| is used this is not necessarily the case + because later subpatterns may have lower numbers. - As a simple example of the name/number table, consider the following + As a simple example of the name/number table, consider the following pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white space - including newlines - is ignored): (? (?(\d\d)?\d\d) - (?\d\d) - (?\d\d) ) - There are four named subpatterns, so the table has four entries, and - each entry in the table is eight bytes long. The table is as follows, + There are four named subpatterns, so the table has four entries, and + each entry in the table is eight bytes long. The table is as follows, with non-printing bytes shows in hexadecimal, and undefined bytes shown as ??: @@ -2258,31 +2887,31 @@ INFORMATION ABOUT A PATTERN 00 04 m o n t h 00 00 02 y e a r 00 ?? - When writing code to extract data from named subpatterns using the - name-to-number map, remember that the length of the entries is likely + When writing code to extract data from named subpatterns using the + name-to-number map, remember that the length of the entries is likely to be different for each compiled pattern. PCRE_INFO_OKPARTIAL - Return 1 if the pattern can be used for partial matching with - pcre_exec(), otherwise 0. The fourth argument should point to an int - variable. From release 8.00, this always returns 1, because the - restrictions that previously applied to partial matching have been - lifted. The pcrepartial documentation gives details of partial match- + Return 1 if the pattern can be used for partial matching with + pcre_exec(), otherwise 0. The fourth argument should point to an int + variable. From release 8.00, this always returns 1, because the + restrictions that previously applied to partial matching have been + lifted. The pcrepartial documentation gives details of partial match- ing. PCRE_INFO_OPTIONS - Return a copy of the options with which the pattern was compiled. The - fourth argument should point to an unsigned long int variable. These + Return a copy of the options with which the pattern was compiled. The + fourth argument should point to an unsigned long int variable. These option bits are those specified in the call to pcre_compile(), modified by any top-level option settings at the start of the pattern itself. In - other words, they are the options that will be in force when matching - starts. For example, if the pattern /(?im)abc(?-i)d/ is compiled with - the PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE, + other words, they are the options that will be in force when matching + starts. For example, if the pattern /(?im)abc(?-i)d/ is compiled with + the PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED. - A pattern is automatically anchored by PCRE if all of its top-level + A pattern is automatically anchored by PCRE if all of its top-level alternatives begin with one of the following: ^ unless PCRE_MULTILINE is set @@ -2294,30 +2923,91 @@ INFORMATION ABOUT A PATTERN For such patterns, the PCRE_ANCHORED bit is set in the options returned by pcre_fullinfo(). + PCRE_INFO_RECURSIONLIMIT + + If the pattern set a recursion limit by including an item of the form + (*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth + argument should point to an unsigned 32-bit integer. If no such value + has been set, the call to pcre_fullinfo() returns the error + PCRE_ERROR_UNSET. + PCRE_INFO_SIZE - Return the size of the compiled pattern in bytes (for both libraries). - The fourth argument should point to a size_t variable. This value does - not include the size of the pcre structure that is returned by - pcre_compile(). The value that is passed as the argument to pcre_mal- - loc() when pcre_compile() is getting memory in which to place the com- - piled data is the value returned by this option plus the size of the - pcre structure. Studying a compiled pattern, with or without JIT, does - not alter the value returned by this option. + Return the size of the compiled pattern in bytes (for all three + libraries). The fourth argument should point to a size_t variable. This + value does not include the size of the pcre structure that is returned + by pcre_compile(). The value that is passed as the argument to + pcre_malloc() when pcre_compile() is getting memory in which to place + the compiled data is the value returned by this option plus the size of + the pcre structure. Studying a compiled pattern, with or without JIT, + does not alter the value returned by this option. PCRE_INFO_STUDYSIZE - Return the size in bytes of the data block pointed to by the study_data - field in a pcre_extra block. If pcre_extra is NULL, or there is no - study data, zero is returned. The fourth argument should point to a - size_t variable. The study_data field is set by pcre_study() to record - information that will speed up matching (see the section entitled - "Studying a pattern" above). The format of the study_data block is pri- - vate, but its length is made available via this option so that it can - be saved and restored (see the pcreprecompile documentation for - details). + Return the size in bytes (for all three libraries) of the data block + pointed to by the study_data field in a pcre_extra block. If pcre_extra + is NULL, or there is no study data, zero is returned. The fourth argu- + ment should point to a size_t variable. The study_data field is set by + pcre_study() to record information that will speed up matching (see the + section entitled "Studying a pattern" above). The format of the + study_data block is private, but its length is made available via this + option so that it can be saved and restored (see the pcreprecompile + documentation for details). + PCRE_INFO_FIRSTCHARACTERFLAGS + Return information about the first data unit of any matched string, for + a non-anchored pattern. The fourth argument should point to an int + variable. + + If there is a fixed first value, for example, the letter "c" from a + pattern such as (cat|cow|coyote), 1 is returned, and the character + value can be retrieved using PCRE_INFO_FIRSTCHARACTER. + + If there is no fixed first value, and if either + + (a) the pattern was compiled with the PCRE_MULTILINE option, and every + branch starts with "^", or + + (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not + set (if it were set, the pattern would be anchored), + + 2 is returned, indicating that the pattern matches only at the start of + a subject string or after any newline within the string. Otherwise 0 is + returned. For anchored patterns, 0 is returned. + + PCRE_INFO_FIRSTCHARACTER + + Return the fixed first character value in the situation where + PCRE_INFO_FIRSTCHARACTERFLAGS returns 1; otherwise return 0. The fourth + argument should point to an uint_t variable. + + In the 8-bit library, the value is always less than 256. In the 16-bit + library the value can be up to 0xffff. In the 32-bit library in UTF-32 + mode the value can be up to 0x10ffff, and up to 0xffffffff when not + using UTF-32 mode. + + PCRE_INFO_REQUIREDCHARFLAGS + + Returns 1 if there is a rightmost literal data unit that must exist in + any matched string, other than at its start. The fourth argument should + point to an int variable. If there is no such value, 0 is returned. If + returning 1, the character value itself can be retrieved using + PCRE_INFO_REQUIREDCHAR. + + For anchored patterns, a last literal value is recorded only if it fol- + lows something of variable length. For example, for the pattern + /^a\d+z\d+/ the returned value 1 (with "z" returned from + PCRE_INFO_REQUIREDCHAR), but for /^a\dz\d/ the returned value is 0. + + PCRE_INFO_REQUIREDCHAR + + Return the value of the rightmost literal data unit that must exist in + any matched string, other than at its start, if such a value has been + recorded. The fourth argument should point to an uint32_t variable. If + there is no such value, 0 is returned. + + REFERENCE COUNTS int pcre_refcount(pcre *code, int adjust); @@ -2398,7 +3088,10 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION In the 16-bit version of this structure, the mark field has type "PCRE_UCHAR16 **". - The flags field is used to specify which of the other fields are set. + In the 32-bit version of this structure, the mark field has type + "PCRE_UCHAR32 **". + + The flags field is used to specify which of the other fields are set. The flag bits are: PCRE_EXTRA_CALLOUT_DATA @@ -2409,39 +3102,48 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_EXTRA_STUDY_DATA PCRE_EXTRA_TABLES - Other flag bits should be set to zero. The study_data field and some- - times the executable_jit field are set in the pcre_extra block that is - returned by pcre_study(), together with the appropriate flag bits. You - should not set these yourself, but you may add to the block by setting + Other flag bits should be set to zero. The study_data field and some- + times the executable_jit field are set in the pcre_extra block that is + returned by pcre_study(), together with the appropriate flag bits. You + should not set these yourself, but you may add to the block by setting other fields and their corresponding flag bits. The match_limit field provides a means of preventing PCRE from using up - a vast amount of resources when running patterns that are not going to - match, but which have a very large number of possibilities in their - search trees. The classic example is a pattern that uses nested unlim- + a vast amount of resources when running patterns that are not going to + match, but which have a very large number of possibilities in their + search trees. The classic example is a pattern that uses nested unlim- ited repeats. - Internally, pcre_exec() uses a function called match(), which it calls - repeatedly (sometimes recursively). The limit set by match_limit is - imposed on the number of times this function is called during a match, - which has the effect of limiting the amount of backtracking that can + Internally, pcre_exec() uses a function called match(), which it calls + repeatedly (sometimes recursively). The limit set by match_limit is + imposed on the number of times this function is called during a match, + which has the effect of limiting the amount of backtracking that can take place. For patterns that are not anchored, the count restarts from zero for each position in the subject string. When pcre_exec() is called with a pattern that was successfully studied - with a JIT option, the way that the matching is executed is entirely + with a JIT option, the way that the matching is executed is entirely different. However, there is still the possibility of runaway matching that goes on for a very long time, and so the match_limit value is also used in this case (but in a different way) to limit how long the match- ing can continue. - The default value for the limit can be set when PCRE is built; the - default default is 10 million, which handles all but the most extreme - cases. You can override the default by suppling pcre_exec() with a - pcre_extra block in which match_limit is set, and - PCRE_EXTRA_MATCH_LIMIT is set in the flags field. If the limit is + The default value for the limit can be set when PCRE is built; the + default default is 10 million, which handles all but the most extreme + cases. You can override the default by suppling pcre_exec() with a + pcre_extra block in which match_limit is set, and + PCRE_EXTRA_MATCH_LIMIT is set in the flags field. If the limit is exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT. + A value for the match limit may also be supplied by an item at the + start of a pattern of the form + + (*LIMIT_MATCH=d) + + where d is a decimal number. However, such a setting is ignored unless + d is less than the limit set by the caller of pcre_exec() or, if no + such limit is set, less than the default. + The match_limit_recursion field is similar to match_limit, but instead of limiting the total number of times that match() is called, it limits the depth of recursion. The recursion depth is a smaller number than @@ -2461,60 +3163,73 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the flags field. If the limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT. - The callout_data field is used in conjunction with the "callout" fea- + A value for the recursion limit may also be supplied by an item at the + start of a pattern of the form + + (*LIMIT_RECURSION=d) + + where d is a decimal number. However, such a setting is ignored unless + d is less than the limit set by the caller of pcre_exec() or, if no + such limit is set, less than the default. + + The callout_data field is used in conjunction with the "callout" fea- ture, and is described in the pcrecallout documentation. - The tables field is used to pass a character tables pointer to - pcre_exec(); this overrides the value that is stored with the compiled - pattern. A non-NULL value is stored with the compiled pattern only if - custom tables were supplied to pcre_compile() via its tableptr argu- - ment. If NULL is passed to pcre_exec() using this mechanism, it forces - PCRE's internal tables to be used. This facility is helpful when re- - using patterns that have been saved after compiling with an external - set of tables, because the external tables might be at a different - address when pcre_exec() is called. See the pcreprecompile documenta- - tion for a discussion of saving compiled patterns for later use. + The tables field is provided for use with patterns that have been pre- + compiled using custom character tables, saved to disc or elsewhere, and + then reloaded, because the tables that were used to compile a pattern + are not saved with it. See the pcreprecompile documentation for a dis- + cussion of saving compiled patterns for later use. If NULL is passed + using this mechanism, it forces PCRE's internal tables to be used. - If PCRE_EXTRA_MARK is set in the flags field, the mark field must be - set to point to a suitable variable. If the pattern contains any back- - tracking control verbs such as (*MARK:NAME), and the execution ends up - with a name to pass back, a pointer to the name string (zero termi- - nated) is placed in the variable pointed to by the mark field. The - names are within the compiled pattern; if you wish to retain such a - name you must copy it before freeing the memory of a compiled pattern. - If there is no name to pass back, the variable pointed to by the mark - field is set to NULL. For details of the backtracking control verbs, + Warning: The tables that pcre_exec() uses must be the same as those + that were used when the pattern was compiled. If this is not the case, + the behaviour of pcre_exec() is undefined. Therefore, when a pattern is + compiled and matched in the same process, this field should never be + set. In this (the most common) case, the correct table pointer is auto- + matically passed with the compiled pattern from pcre_compile() to + pcre_exec(). + + If PCRE_EXTRA_MARK is set in the flags field, the mark field must be + set to point to a suitable variable. If the pattern contains any back- + tracking control verbs such as (*MARK:NAME), and the execution ends up + with a name to pass back, a pointer to the name string (zero termi- + nated) is placed in the variable pointed to by the mark field. The + names are within the compiled pattern; if you wish to retain such a + name you must copy it before freeing the memory of a compiled pattern. + If there is no name to pass back, the variable pointed to by the mark + field is set to NULL. For details of the backtracking control verbs, see the section entitled "Backtracking control" in the pcrepattern doc- umentation. Option bits for pcre_exec() - The unused bits of the options argument for pcre_exec() must be zero. - The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx, - PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, - PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and + The unused bits of the options argument for pcre_exec() must be zero. + The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx, + PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, + PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. - If the pattern was successfully studied with one of the just-in-time + If the pattern was successfully studied with one of the just-in-time (JIT) compile options, the only supported options for JIT execution are - PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, - PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an - unsupported option is used, JIT execution is disabled and the normal + PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, + PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an + unsupported option is used, JIT execution is disabled and the normal interpretive code in pcre_exec() is run. PCRE_ANCHORED - The PCRE_ANCHORED option limits pcre_exec() to matching at the first - matching position. If a pattern was compiled with PCRE_ANCHORED, or - turned out to be anchored by virtue of its contents, it cannot be made + The PCRE_ANCHORED option limits pcre_exec() to matching at the first + matching position. If a pattern was compiled with PCRE_ANCHORED, or + turned out to be anchored by virtue of its contents, it cannot be made unachored at matching time. PCRE_BSR_ANYCRLF PCRE_BSR_UNICODE These options (which are mutually exclusive) control what the \R escape - sequence matches. The choice is either to match only CR, LF, or CRLF, - or to match any Unicode newline sequence. These options override the + sequence matches. The choice is either to match only CR, LF, or CRLF, + or to match any Unicode newline sequence. These options override the choice that was made or defaulted when the pattern was compiled. PCRE_NEWLINE_CR @@ -2523,109 +3238,110 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_NEWLINE_ANYCRLF PCRE_NEWLINE_ANY - These options override the newline definition that was chosen or - defaulted when the pattern was compiled. For details, see the descrip- - tion of pcre_compile() above. During matching, the newline choice - affects the behaviour of the dot, circumflex, and dollar metacharac- - ters. It may also alter the way the match position is advanced after a + These options override the newline definition that was chosen or + defaulted when the pattern was compiled. For details, see the descrip- + tion of pcre_compile() above. During matching, the newline choice + affects the behaviour of the dot, circumflex, and dollar metacharac- + ters. It may also alter the way the match position is advanced after a match failure for an unanchored pattern. - When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is - set, and a match attempt for an unanchored pattern fails when the cur- - rent position is at a CRLF sequence, and the pattern contains no - explicit matches for CR or LF characters, the match position is + When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is + set, and a match attempt for an unanchored pattern fails when the cur- + rent position is at a CRLF sequence, and the pattern contains no + explicit matches for CR or LF characters, the match position is advanced by two characters instead of one, in other words, to after the CRLF. The above rule is a compromise that makes the most common cases work as - expected. For example, if the pattern is .+A (and the PCRE_DOTALL + expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not set), it does not match the string "\r\nA" because, after - failing at the start, it skips both the CR and the LF before retrying. - However, the pattern [\r\n]A does match that string, because it con- + failing at the start, it skips both the CR and the LF before retrying. + However, the pattern [\r\n]A does match that string, because it con- tains an explicit CR or LF reference, and so advances only by one char- acter after the first failure. An explicit match for CR of LF is either a literal appearance of one of - those characters, or one of the \r or \n escape sequences. Implicit - matches such as [^X] do not count, nor does \s (which includes CR and + those characters, or one of the \r or \n escape sequences. Implicit + matches such as [^X] do not count, nor does \s (which includes CR and LF in the characters that it matches). - Notwithstanding the above, anomalous effects may still occur when CRLF + Notwithstanding the above, anomalous effects may still occur when CRLF is a valid newline sequence and explicit \r or \n escapes appear in the pattern. PCRE_NOTBOL This option specifies that first character of the subject string is not - the beginning of a line, so the circumflex metacharacter should not - match before it. Setting this without PCRE_MULTILINE (at compile time) - causes circumflex never to match. This option affects only the behav- + the beginning of a line, so the circumflex metacharacter should not + match before it. Setting this without PCRE_MULTILINE (at compile time) + causes circumflex never to match. This option affects only the behav- iour of the circumflex metacharacter. It does not affect \A. PCRE_NOTEOL This option specifies that the end of the subject string is not the end - of a line, so the dollar metacharacter should not match it nor (except - in multiline mode) a newline immediately before it. Setting this with- + of a line, so the dollar metacharacter should not match it nor (except + in multiline mode) a newline immediately before it. Setting this with- out PCRE_MULTILINE (at compile time) causes dollar never to match. This - option affects only the behaviour of the dollar metacharacter. It does + option affects only the behaviour of the dollar metacharacter. It does not affect \Z or \z. PCRE_NOTEMPTY An empty string is not considered to be a valid match if this option is - set. If there are alternatives in the pattern, they are tried. If all - the alternatives match the empty string, the entire match fails. For + set. If there are alternatives in the pattern, they are tried. If all + the alternatives match the empty string, the entire match fails. For example, if the pattern a?b? - is applied to a string not beginning with "a" or "b", it matches an - empty string at the start of the subject. With PCRE_NOTEMPTY set, this + is applied to a string not beginning with "a" or "b", it matches an + empty string at the start of the subject. With PCRE_NOTEMPTY set, this match is not valid, so PCRE searches further into the string for occur- rences of "a" or "b". PCRE_NOTEMPTY_ATSTART - This is like PCRE_NOTEMPTY, except that an empty string match that is - not at the start of the subject is permitted. If the pattern is + This is like PCRE_NOTEMPTY, except that an empty string match that is + not at the start of the subject is permitted. If the pattern is anchored, such a match can occur only if the pattern contains \K. - Perl has no direct equivalent of PCRE_NOTEMPTY or - PCRE_NOTEMPTY_ATSTART, but it does make a special case of a pattern - match of the empty string within its split() function, and when using - the /g modifier. It is possible to emulate Perl's behaviour after + Perl has no direct equivalent of PCRE_NOTEMPTY or + PCRE_NOTEMPTY_ATSTART, but it does make a special case of a pattern + match of the empty string within its split() function, and when using + the /g modifier. It is possible to emulate Perl's behaviour after matching a null string by first trying the match again at the same off- - set with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then if that + set with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then if that fails, by advancing the starting offset (see below) and trying an ordi- - nary match again. There is some code that demonstrates how to do this - in the pcredemo sample program. In the most general case, you have to - check to see if the newline convention recognizes CRLF as a newline, - and if so, and the current character is CR followed by LF, advance the + nary match again. There is some code that demonstrates how to do this + in the pcredemo sample program. In the most general case, you have to + check to see if the newline convention recognizes CRLF as a newline, + and if so, and the current character is CR followed by LF, advance the starting offset by two characters instead of one. PCRE_NO_START_OPTIMIZE - There are a number of optimizations that pcre_exec() uses at the start - of a match, in order to speed up the process. For example, if it is + There are a number of optimizations that pcre_exec() uses at the start + of a match, in order to speed up the process. For example, if it is known that an unanchored match must start with a specific character, it - searches the subject for that character, and fails immediately if it - cannot find it, without actually running the main matching function. + searches the subject for that character, and fails immediately if it + cannot find it, without actually running the main matching function. This means that a special item such as (*COMMIT) at the start of a pat- - tern is not considered until after a suitable starting point for the - match has been found. When callouts or (*MARK) items are in use, these - "start-up" optimizations can cause them to be skipped if the pattern is - never actually used. The start-up optimizations are in effect a pre- - scan of the subject that takes place before the pattern is run. + tern is not considered until after a suitable starting point for the + match has been found. Also, when callouts or (*MARK) items are in use, + these "start-up" optimizations can cause them to be skipped if the pat- + tern is never actually used. The start-up optimizations are in effect a + pre-scan of the subject that takes place before the pattern is run. - The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, - possibly causing performance to suffer, but ensuring that in cases - where the result is "no match", the callouts do occur, and that items + The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, + possibly causing performance to suffer, but ensuring that in cases + where the result is "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK) are considered at every possible starting - position in the subject string. If PCRE_NO_START_OPTIMIZE is set at - compile time, it cannot be unset at matching time. The use of - PCRE_NO_START_OPTIMIZE disables JIT execution; when it is set, matching - is always done using interpretively. + position in the subject string. If PCRE_NO_START_OPTIMIZE is set at + compile time, it cannot be unset at matching time. The use of + PCRE_NO_START_OPTIMIZE at matching time (that is, passing it to + pcre_exec()) disables JIT execution; in this situation, matching is + always done using interpretively. Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation. Consider the pattern @@ -2681,7 +3397,7 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION points to the start of a character (or the end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid string as a subject or an invalid value of startoffset is undefined. Your program - may crash. + may crash or loop. PCRE_PARTIAL_HARD PCRE_PARTIAL_SOFT @@ -2711,149 +3427,156 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION The string to be matched by pcre_exec() The subject string is passed to pcre_exec() as a pointer in subject, a - length in bytes in length, and a starting byte offset in startoffset. - If this is negative or greater than the length of the subject, + length in length, and a starting offset in startoffset. The units for + length and startoffset are bytes for the 8-bit library, 16-bit data + items for the 16-bit library, and 32-bit data items for the 32-bit + library. + + If startoffset is negative or greater than the length of the subject, pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting offset is zero, the search for a match starts at the beginning of the subject, - and this is by far the most common case. In UTF-8 mode, the byte offset - must point to the start of a UTF-8 character (or the end of the sub- - ject). Unlike the pattern string, the subject may contain binary zero - bytes. + and this is by far the most common case. In UTF-8 or UTF-16 mode, the + offset must point to the start of a character, or the end of the sub- + ject (in UTF-32 mode, one data unit equals one character, so all off- + sets are valid). Unlike the pattern string, the subject may contain + binary zeroes. - A non-zero starting offset is useful when searching for another match - in the same subject by calling pcre_exec() again after a previous suc- - cess. Setting startoffset differs from just passing over a shortened - string and setting PCRE_NOTBOL in the case of a pattern that begins + A non-zero starting offset is useful when searching for another match + in the same subject by calling pcre_exec() again after a previous suc- + cess. Setting startoffset differs from just passing over a shortened + string and setting PCRE_NOTBOL in the case of a pattern that begins with any kind of lookbehind. For example, consider the pattern \Biss\B - which finds occurrences of "iss" in the middle of words. (\B matches - only if the current position in the subject is not a word boundary.) - When applied to the string "Mississipi" the first call to pcre_exec() - finds the first occurrence. If pcre_exec() is called again with just - the remainder of the subject, namely "issipi", it does not match, + which finds occurrences of "iss" in the middle of words. (\B matches + only if the current position in the subject is not a word boundary.) + When applied to the string "Mississipi" the first call to pcre_exec() + finds the first occurrence. If pcre_exec() is called again with just + the remainder of the subject, namely "issipi", it does not match, because \B is always false at the start of the subject, which is deemed - to be a word boundary. However, if pcre_exec() is passed the entire + to be a word boundary. However, if pcre_exec() is passed the entire string again, but with startoffset set to 4, it finds the second occur- - rence of "iss" because it is able to look behind the starting point to + rence of "iss" because it is able to look behind the starting point to discover that it is preceded by a letter. - Finding all the matches in a subject is tricky when the pattern can + Finding all the matches in a subject is tricky when the pattern can match an empty string. It is possible to emulate Perl's /g behaviour by - first trying the match again at the same offset, with the - PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED options, and then if that - fails, advancing the starting offset and trying an ordinary match + first trying the match again at the same offset, with the + PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED options, and then if that + fails, advancing the starting offset and trying an ordinary match again. There is some code that demonstrates how to do this in the pcre- demo sample program. In the most general case, you have to check to see - if the newline convention recognizes CRLF as a newline, and if so, and + if the newline convention recognizes CRLF as a newline, and if so, and the current character is CR followed by LF, advance the starting offset by two characters instead of one. - If a non-zero starting offset is passed when the pattern is anchored, + If a non-zero starting offset is passed when the pattern is anchored, one attempt to match at the given offset is made. This can only succeed - if the pattern does not require the match to be at the start of the + if the pattern does not require the match to be at the start of the subject. How pcre_exec() returns captured substrings - In general, a pattern matches a certain portion of the subject, and in - addition, further substrings from the subject may be picked out by - parts of the pattern. Following the usage in Jeffrey Friedl's book, - this is called "capturing" in what follows, and the phrase "capturing - subpattern" is used for a fragment of a pattern that picks out a sub- - string. PCRE supports several other kinds of parenthesized subpattern + In general, a pattern matches a certain portion of the subject, and in + addition, further substrings from the subject may be picked out by + parts of the pattern. Following the usage in Jeffrey Friedl's book, + this is called "capturing" in what follows, and the phrase "capturing + subpattern" is used for a fragment of a pattern that picks out a sub- + string. PCRE supports several other kinds of parenthesized subpattern that do not cause substrings to be captured. Captured substrings are returned to the caller via a vector of integers - whose address is passed in ovector. The number of elements in the vec- - tor is passed in ovecsize, which must be a non-negative number. Note: + whose address is passed in ovector. The number of elements in the vec- + tor is passed in ovecsize, which must be a non-negative number. Note: this argument is NOT the size of ovector in bytes. - The first two-thirds of the vector is used to pass back captured sub- - strings, each substring using a pair of integers. The remaining third - of the vector is used as workspace by pcre_exec() while matching cap- - turing subpatterns, and is not available for passing back information. - The number passed in ovecsize should always be a multiple of three. If + The first two-thirds of the vector is used to pass back captured sub- + strings, each substring using a pair of integers. The remaining third + of the vector is used as workspace by pcre_exec() while matching cap- + turing subpatterns, and is not available for passing back information. + The number passed in ovecsize should always be a multiple of three. If it is not, it is rounded down. - When a match is successful, information about captured substrings is - returned in pairs of integers, starting at the beginning of ovector, - and continuing up to two-thirds of its length at the most. The first - element of each pair is set to the byte offset of the first character - in a substring, and the second is set to the byte offset of the first - character after the end of a substring. Note: these values are always - byte offsets, even in UTF-8 mode. They are not character counts. + When a match is successful, information about captured substrings is + returned in pairs of integers, starting at the beginning of ovector, + and continuing up to two-thirds of its length at the most. The first + element of each pair is set to the offset of the first character in a + substring, and the second is set to the offset of the first character + after the end of a substring. These values are always data unit off- + sets, even in UTF mode. They are byte offsets in the 8-bit library, + 16-bit data item offsets in the 16-bit library, and 32-bit data item + offsets in the 32-bit library. Note: they are not character counts. - The first pair of integers, ovector[0] and ovector[1], identify the - portion of the subject string matched by the entire pattern. The next - pair is used for the first capturing subpattern, and so on. The value + The first pair of integers, ovector[0] and ovector[1], identify the + portion of the subject string matched by the entire pattern. The next + pair is used for the first capturing subpattern, and so on. The value returned by pcre_exec() is one more than the highest numbered pair that - has been set. For example, if two substrings have been captured, the - returned value is 3. If there are no capturing subpatterns, the return + has been set. For example, if two substrings have been captured, the + returned value is 3. If there are no capturing subpatterns, the return value from a successful match is 1, indicating that just the first pair of offsets has been set. If a capturing subpattern is matched repeatedly, it is the last portion of the string that it matched that is returned. - If the vector is too small to hold all the captured substring offsets, + If the vector is too small to hold all the captured substring offsets, it is used as far as possible (up to two-thirds of its length), and the - function returns a value of zero. If neither the actual string matched - nor any captured substrings are of interest, pcre_exec() may be called - with ovector passed as NULL and ovecsize as zero. However, if the pat- - tern contains back references and the ovector is not big enough to - remember the related substrings, PCRE has to get additional memory for - use during matching. Thus it is usually advisable to supply an ovector + function returns a value of zero. If neither the actual string matched + nor any captured substrings are of interest, pcre_exec() may be called + with ovector passed as NULL and ovecsize as zero. However, if the pat- + tern contains back references and the ovector is not big enough to + remember the related substrings, PCRE has to get additional memory for + use during matching. Thus it is usually advisable to supply an ovector of reasonable size. - There are some cases where zero is returned (indicating vector over- - flow) when in fact the vector is exactly the right size for the final + There are some cases where zero is returned (indicating vector over- + flow) when in fact the vector is exactly the right size for the final match. For example, consider the pattern (a)(?:(b)c|bd) - If a vector of 6 elements (allowing for only 1 captured substring) is + If a vector of 6 elements (allowing for only 1 captured substring) is given with subject string "abd", pcre_exec() will try to set the second captured string, thereby recording a vector overflow, before failing to - match "c" and backing up to try the second alternative. The zero - return, however, does correctly indicate that the maximum number of + match "c" and backing up to try the second alternative. The zero + return, however, does correctly indicate that the maximum number of slots (namely 2) have been filled. In similar cases where there is tem- - porary overflow, but the final number of used slots is actually less + porary overflow, but the final number of used slots is actually less than the maximum, a non-zero value is returned. The pcre_fullinfo() function can be used to find out how many capturing - subpatterns there are in a compiled pattern. The smallest size for - ovector that will allow for n captured substrings, in addition to the + subpatterns there are in a compiled pattern. The smallest size for + ovector that will allow for n captured substrings, in addition to the offsets of the substring matched by the whole pattern, is (n+1)*3. - It is possible for capturing subpattern number n+1 to match some part + It is possible for capturing subpattern number n+1 to match some part of the subject when subpattern n has not been used at all. For example, - if the string "abc" is matched against the pattern (a|(z))(bc) the + if the string "abc" is matched against the pattern (a|(z))(bc) the return from the function is 4, and subpatterns 1 and 3 are matched, but - 2 is not. When this happens, both values in the offset pairs corre- + 2 is not. When this happens, both values in the offset pairs corre- sponding to unused subpatterns are set to -1. - Offset values that correspond to unused subpatterns at the end of the - expression are also set to -1. For example, if the string "abc" is - matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not - matched. The return from the function is 2, because the highest used - capturing subpattern number is 1, and the offsets for for the second - and third capturing subpatterns (assuming the vector is large enough, + Offset values that correspond to unused subpatterns at the end of the + expression are also set to -1. For example, if the string "abc" is + matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not + matched. The return from the function is 2, because the highest used + capturing subpattern number is 1, and the offsets for for the second + and third capturing subpatterns (assuming the vector is large enough, of course) are set to -1. - Note: Elements in the first two-thirds of ovector that do not corre- - spond to capturing parentheses in the pattern are never changed. That - is, if a pattern contains n capturing parentheses, no more than ovec- - tor[0] to ovector[2n+1] are set by pcre_exec(). The other elements (in + Note: Elements in the first two-thirds of ovector that do not corre- + spond to capturing parentheses in the pattern are never changed. That + is, if a pattern contains n capturing parentheses, no more than ovec- + tor[0] to ovector[2n+1] are set by pcre_exec(). The other elements (in the first two-thirds) retain whatever values they previously had. - Some convenience functions are provided for extracting the captured + Some convenience functions are provided for extracting the captured substrings as separate strings. These are described below. Error return values from pcre_exec() - If pcre_exec() fails, it returns a negative number. The following are + If pcre_exec() fails, it returns a negative number. The following are defined in the header file: PCRE_ERROR_NOMATCH (-1) @@ -2862,7 +3585,7 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_ERROR_NULL (-2) - Either code or subject was passed as NULL, or ovector was NULL and + Either code or subject was passed as NULL, or ovector was NULL and ovecsize was not zero. PCRE_ERROR_BADOPTION (-3) @@ -2871,82 +3594,82 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_ERROR_BADMAGIC (-4) - PCRE stores a 4-byte "magic number" at the start of the compiled code, + PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch the case when it is passed a junk pointer and to detect when a pattern that was compiled in an environment of one endianness is run in - an environment with the other endianness. This is the error that PCRE + an environment with the other endianness. This is the error that PCRE gives when the magic number is not present. PCRE_ERROR_UNKNOWN_OPCODE (-5) While running the pattern match, an unknown item was encountered in the - compiled pattern. This error could be caused by a bug in PCRE or by + compiled pattern. This error could be caused by a bug in PCRE or by overwriting of the compiled pattern. PCRE_ERROR_NOMEMORY (-6) - If a pattern contains back references, but the ovector that is passed + If a pattern contains back references, but the ovector that is passed to pcre_exec() is not big enough to remember the referenced substrings, - PCRE gets a block of memory at the start of matching to use for this - purpose. If the call via pcre_malloc() fails, this error is given. The + PCRE gets a block of memory at the start of matching to use for this + purpose. If the call via pcre_malloc() fails, this error is given. The memory is automatically freed at the end of matching. - This error is also given if pcre_stack_malloc() fails in pcre_exec(). - This can happen only when PCRE has been compiled with --disable-stack- + This error is also given if pcre_stack_malloc() fails in pcre_exec(). + This can happen only when PCRE has been compiled with --disable-stack- for-recursion. PCRE_ERROR_NOSUBSTRING (-7) - This error is used by the pcre_copy_substring(), pcre_get_substring(), + This error is used by the pcre_copy_substring(), pcre_get_substring(), and pcre_get_substring_list() functions (see below). It is never returned by pcre_exec(). PCRE_ERROR_MATCHLIMIT (-8) - The backtracking limit, as specified by the match_limit field in a - pcre_extra structure (or defaulted) was reached. See the description + The backtracking limit, as specified by the match_limit field in a + pcre_extra structure (or defaulted) was reached. See the description above. PCRE_ERROR_CALLOUT (-9) This error is never generated by pcre_exec() itself. It is provided for - use by callout functions that want to yield a distinctive error code. + use by callout functions that want to yield a distinctive error code. See the pcrecallout documentation for details. PCRE_ERROR_BADUTF8 (-10) - A string that contains an invalid UTF-8 byte sequence was passed as a - subject, and the PCRE_NO_UTF8_CHECK option was not set. If the size of - the output vector (ovecsize) is at least 2, the byte offset to the - start of the the invalid UTF-8 character is placed in the first ele- - ment, and a reason code is placed in the second element. The reason + A string that contains an invalid UTF-8 byte sequence was passed as a + subject, and the PCRE_NO_UTF8_CHECK option was not set. If the size of + the output vector (ovecsize) is at least 2, the byte offset to the + start of the the invalid UTF-8 character is placed in the first ele- + ment, and a reason code is placed in the second element. The reason codes are listed in the following section. For backward compatibility, - if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8 char- - acter at the end of the subject (reason codes 1 to 5), + if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8 char- + acter at the end of the subject (reason codes 1 to 5), PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8. PCRE_ERROR_BADUTF8_OFFSET (-11) - The UTF-8 byte sequence that was passed as a subject was checked and - found to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the - value of startoffset did not point to the beginning of a UTF-8 charac- + The UTF-8 byte sequence that was passed as a subject was checked and + found to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the + value of startoffset did not point to the beginning of a UTF-8 charac- ter or the end of the subject. PCRE_ERROR_PARTIAL (-12) - The subject string did not match, but it did match partially. See the + The subject string did not match, but it did match partially. See the pcrepartial documentation for details of partial matching. PCRE_ERROR_BADPARTIAL (-13) - This code is no longer in use. It was formerly returned when the - PCRE_PARTIAL option was used with a compiled pattern containing items - that were not supported for partial matching. From release 8.00 + This code is no longer in use. It was formerly returned when the + PCRE_PARTIAL option was used with a compiled pattern containing items + that were not supported for partial matching. From release 8.00 onwards, there are no restrictions on partial matching. PCRE_ERROR_INTERNAL (-14) - An unexpected internal error has occurred. This error could be caused + An unexpected internal error has occurred. This error could be caused by a bug in PCRE or by overwriting of the compiled pattern. PCRE_ERROR_BADCOUNT (-15) @@ -2956,7 +3679,7 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_ERROR_RECURSIONLIMIT (-21) The internal recursion limit, as specified by the match_limit_recursion - field in a pcre_extra structure (or defaulted) was reached. See the + field in a pcre_extra structure (or defaulted) was reached. See the description above. PCRE_ERROR_BADNEWLINE (-23) @@ -2970,49 +3693,64 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_ERROR_SHORTUTF8 (-25) - This error is returned instead of PCRE_ERROR_BADUTF8 when the subject - string ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD - option is set. Information about the failure is returned as for - PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this case, but - this special error code for PCRE_PARTIAL_HARD precedes the implementa- - tion of returned information; it is retained for backwards compatibil- + This error is returned instead of PCRE_ERROR_BADUTF8 when the subject + string ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD + option is set. Information about the failure is returned as for + PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this case, but + this special error code for PCRE_PARTIAL_HARD precedes the implementa- + tion of returned information; it is retained for backwards compatibil- ity. PCRE_ERROR_RECURSELOOP (-26) This error is returned when pcre_exec() detects a recursion loop within - the pattern. Specifically, it means that either the whole pattern or a - subpattern has been called recursively for the second time at the same + the pattern. Specifically, it means that either the whole pattern or a + subpattern has been called recursively for the second time at the same position in the subject string. Some simple patterns that might do this - are detected and faulted at compile time, but more complicated cases, + are detected and faulted at compile time, but more complicated cases, in particular mutual recursions between two different subpatterns, can- not be detected until run time. PCRE_ERROR_JIT_STACKLIMIT (-27) - This error is returned when a pattern that was successfully studied - using a JIT compile option is being matched, but the memory available - for the just-in-time processing stack is not large enough. See the + This error is returned when a pattern that was successfully studied + using a JIT compile option is being matched, but the memory available + for the just-in-time processing stack is not large enough. See the pcrejit documentation for more details. PCRE_ERROR_BADMODE (-28) This error is given if a pattern that was compiled by the 8-bit library - is passed to a 16-bit library function, or vice versa. + is passed to a 16-bit or 32-bit library function, or vice versa. PCRE_ERROR_BADENDIANNESS (-29) - This error is given if a pattern that was compiled and saved is - reloaded on a host with different endianness. The utility function + This error is given if a pattern that was compiled and saved is + reloaded on a host with different endianness. The utility function pcre_pattern_to_host_byte_order() can be used to convert such a pattern so that it runs on the new host. - Error numbers -16 to -20, -22, and -30 are not used by pcre_exec(). + PCRE_ERROR_JIT_BADOPTION + This error is returned when a pattern that was successfully studied + using a JIT compile option is being matched, but the matching mode + (partial or complete match) does not correspond to any JIT compilation + mode. When the JIT fast path function is used, this error may be also + given for invalid options. See the pcrejit documentation for more + details. + + PCRE_ERROR_BADLENGTH (-32) + + This error is given if pcre_exec() is called with a negative value for + the length argument. + + Error numbers -16 to -20, -22, and 30 are not used by pcre_exec(). + Reason codes for invalid UTF-8 strings - This section applies only to the 8-bit library. The corresponding - information for the 16-bit library is given in the pcre16 page. + This section applies only to the 8-bit library. The corresponding + information for the 16-bit and 32-bit libraries is given in the pcre16 + and pcre32 pages. When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT- UTF8, and the size of the output vector (ovecsize) is at least 2, the @@ -3083,7 +3821,14 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION The first byte of a character has the value 0xfe or 0xff. These values can never occur in a valid UTF-8 string. + PCRE_UTF8_ERR22 + This error code was formerly used when the presence of a so-called + "non-character" caused an error. Unicode corrigendum #9 makes it clear + that such characters should not cause a string to be rejected, and so + this code is no longer in use and is never returned. + + EXTRACTING CAPTURED SUBSTRINGS BY NUMBER int pcre_copy_substring(const char *subject, int *ovector, @@ -3097,78 +3842,78 @@ EXTRACTING CAPTURED SUBSTRINGS BY NUMBER int pcre_get_substring_list(const char *subject, int *ovector, int stringcount, const char ***listptr); - Captured substrings can be accessed directly by using the offsets - returned by pcre_exec() in ovector. For convenience, the functions + Captured substrings can be accessed directly by using the offsets + returned by pcre_exec() in ovector. For convenience, the functions pcre_copy_substring(), pcre_get_substring(), and pcre_get_sub- - string_list() are provided for extracting captured substrings as new, - separate, zero-terminated strings. These functions identify substrings - by number. The next section describes functions for extracting named + string_list() are provided for extracting captured substrings as new, + separate, zero-terminated strings. These functions identify substrings + by number. The next section describes functions for extracting named substrings. - A substring that contains a binary zero is correctly extracted and has - a further zero added on the end, but the result is not, of course, a C - string. However, you can process such a string by referring to the - length that is returned by pcre_copy_substring() and pcre_get_sub- + A substring that contains a binary zero is correctly extracted and has + a further zero added on the end, but the result is not, of course, a C + string. However, you can process such a string by referring to the + length that is returned by pcre_copy_substring() and pcre_get_sub- string(). Unfortunately, the interface to pcre_get_substring_list() is - not adequate for handling strings containing binary zeros, because the + not adequate for handling strings containing binary zeros, because the end of the final string is not independently indicated. - The first three arguments are the same for all three of these func- - tions: subject is the subject string that has just been successfully + The first three arguments are the same for all three of these func- + tions: subject is the subject string that has just been successfully matched, ovector is a pointer to the vector of integer offsets that was passed to pcre_exec(), and stringcount is the number of substrings that - were captured by the match, including the substring that matched the + were captured by the match, including the substring that matched the entire regular expression. This is the value returned by pcre_exec() if - it is greater than zero. If pcre_exec() returned zero, indicating that - it ran out of space in ovector, the value passed as stringcount should + it is greater than zero. If pcre_exec() returned zero, indicating that + it ran out of space in ovector, the value passed as stringcount should be the number of elements in the vector divided by three. - The functions pcre_copy_substring() and pcre_get_substring() extract a - single substring, whose number is given as stringnumber. A value of - zero extracts the substring that matched the entire pattern, whereas - higher values extract the captured substrings. For pcre_copy_sub- - string(), the string is placed in buffer, whose length is given by - buffersize, while for pcre_get_substring() a new block of memory is - obtained via pcre_malloc, and its address is returned via stringptr. - The yield of the function is the length of the string, not including + The functions pcre_copy_substring() and pcre_get_substring() extract a + single substring, whose number is given as stringnumber. A value of + zero extracts the substring that matched the entire pattern, whereas + higher values extract the captured substrings. For pcre_copy_sub- + string(), the string is placed in buffer, whose length is given by + buffersize, while for pcre_get_substring() a new block of memory is + obtained via pcre_malloc, and its address is returned via stringptr. + The yield of the function is the length of the string, not including the terminating zero, or one of these error codes: PCRE_ERROR_NOMEMORY (-6) - The buffer was too small for pcre_copy_substring(), or the attempt to + The buffer was too small for pcre_copy_substring(), or the attempt to get memory failed for pcre_get_substring(). PCRE_ERROR_NOSUBSTRING (-7) There is no substring whose number is stringnumber. - The pcre_get_substring_list() function extracts all available sub- - strings and builds a list of pointers to them. All this is done in a + The pcre_get_substring_list() function extracts all available sub- + strings and builds a list of pointers to them. All this is done in a single block of memory that is obtained via pcre_malloc. The address of - the memory block is returned via listptr, which is also the start of - the list of string pointers. The end of the list is marked by a NULL - pointer. The yield of the function is zero if all went well, or the + the memory block is returned via listptr, which is also the start of + the list of string pointers. The end of the list is marked by a NULL + pointer. The yield of the function is zero if all went well, or the error code PCRE_ERROR_NOMEMORY (-6) if the attempt to get the memory block failed. - When any of these functions encounter a substring that is unset, which - can happen when capturing subpattern number n+1 matches some part of - the subject, but subpattern n has not been used at all, they return an + When any of these functions encounter a substring that is unset, which + can happen when capturing subpattern number n+1 matches some part of + the subject, but subpattern n has not been used at all, they return an empty string. This can be distinguished from a genuine zero-length sub- - string by inspecting the appropriate offset in ovector, which is nega- + string by inspecting the appropriate offset in ovector, which is nega- tive for unset substrings. - The two convenience functions pcre_free_substring() and pcre_free_sub- - string_list() can be used to free the memory returned by a previous + The two convenience functions pcre_free_substring() and pcre_free_sub- + string_list() can be used to free the memory returned by a previous call of pcre_get_substring() or pcre_get_substring_list(), respec- - tively. They do nothing more than call the function pointed to by - pcre_free, which of course could be called directly from a C program. - However, PCRE is used in some situations where it is linked via a spe- - cial interface to another programming language that cannot use - pcre_free directly; it is for these cases that the functions are pro- + tively. They do nothing more than call the function pointed to by + pcre_free, which of course could be called directly from a C program. + However, PCRE is used in some situations where it is linked via a spe- + cial interface to another programming language that cannot use + pcre_free directly; it is for these cases that the functions are pro- vided. @@ -3187,7 +3932,7 @@ EXTRACTING CAPTURED SUBSTRINGS BY NAME int stringcount, const char *stringname, const char **stringptr); - To extract a substring by name, you first have to find associated num- + To extract a substring by name, you first have to find associated num- ber. For example, for this pattern (a+)b(?\d+)... @@ -3196,35 +3941,35 @@ EXTRACTING CAPTURED SUBSTRINGS BY NAME be unique (PCRE_DUPNAMES was not set), you can find the number from the name by calling pcre_get_stringnumber(). The first argument is the com- piled pattern, and the second is the name. The yield of the function is - the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no + the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of that name. Given the number, you can extract the substring directly, or use one of the functions described in the previous section. For convenience, there are also two functions that do the whole job. - Most of the arguments of pcre_copy_named_substring() and - pcre_get_named_substring() are the same as those for the similarly - named functions that extract by number. As these are described in the - previous section, they are not re-described here. There are just two + Most of the arguments of pcre_copy_named_substring() and + pcre_get_named_substring() are the same as those for the similarly + named functions that extract by number. As these are described in the + previous section, they are not re-described here. There are just two differences: - First, instead of a substring number, a substring name is given. Sec- + First, instead of a substring number, a substring name is given. Sec- ond, there is an extra argument, given at the start, which is a pointer - to the compiled pattern. This is needed in order to gain access to the + to the compiled pattern. This is needed in order to gain access to the name-to-number translation table. - These functions call pcre_get_stringnumber(), and if it succeeds, they - then call pcre_copy_substring() or pcre_get_substring(), as appropri- - ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate names, the + These functions call pcre_get_stringnumber(), and if it succeeds, they + then call pcre_copy_substring() or pcre_get_substring(), as appropri- + ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate names, the behaviour may not be what you want (see the next section). Warning: If the pattern uses the (?| feature to set up multiple subpat- - terns with the same number, as described in the section on duplicate - subpattern numbers in the pcrepattern page, you cannot use names to - distinguish the different subpatterns, because names are not included - in the compiled code. The matching process uses only numbers. For this - reason, the use of different names for subpatterns of the same number + terns with the same number, as described in the section on duplicate + subpattern numbers in the pcrepattern page, you cannot use names to + distinguish the different subpatterns, because names are not included + in the compiled code. The matching process uses only numbers. For this + reason, the use of different names for subpatterns of the same number causes an error at compile time. @@ -3233,76 +3978,76 @@ DUPLICATE SUBPATTERN NAMES int pcre_get_stringtable_entries(const pcre *code, const char *name, char **first, char **last); - When a pattern is compiled with the PCRE_DUPNAMES option, names for - subpatterns are not required to be unique. (Duplicate names are always - allowed for subpatterns with the same number, created by using the (?| - feature. Indeed, if such subpatterns are named, they are required to + When a pattern is compiled with the PCRE_DUPNAMES option, names for + subpatterns are not required to be unique. (Duplicate names are always + allowed for subpatterns with the same number, created by using the (?| + feature. Indeed, if such subpatterns are named, they are required to use the same names.) Normally, patterns with duplicate names are such that in any one match, - only one of the named subpatterns participates. An example is shown in + only one of the named subpatterns participates. An example is shown in the pcrepattern documentation. - When duplicates are present, pcre_copy_named_substring() and - pcre_get_named_substring() return the first substring corresponding to - the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING - (-7) is returned; no data is returned. The pcre_get_stringnumber() - function returns one of the numbers that are associated with the name, + When duplicates are present, pcre_copy_named_substring() and + pcre_get_named_substring() return the first substring corresponding to + the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING + (-7) is returned; no data is returned. The pcre_get_stringnumber() + function returns one of the numbers that are associated with the name, but it is not defined which it is. - If you want to get full details of all captured substrings for a given - name, you must use the pcre_get_stringtable_entries() function. The + If you want to get full details of all captured substrings for a given + name, you must use the pcre_get_stringtable_entries() function. The first argument is the compiled pattern, and the second is the name. The - third and fourth are pointers to variables which are updated by the + third and fourth are pointers to variables which are updated by the function. After it has run, they point to the first and last entries in - the name-to-number table for the given name. The function itself - returns the length of each entry, or PCRE_ERROR_NOSUBSTRING (-7) if - there are none. The format of the table is described above in the sec- - tion entitled Information about a pattern above. Given all the rele- - vant entries for the name, you can extract each of their numbers, and + the name-to-number table for the given name. The function itself + returns the length of each entry, or PCRE_ERROR_NOSUBSTRING (-7) if + there are none. The format of the table is described above in the sec- + tion entitled Information about a pattern above. Given all the rele- + vant entries for the name, you can extract each of their numbers, and hence the captured data, if any. FINDING ALL POSSIBLE MATCHES - The traditional matching function uses a similar algorithm to Perl, + The traditional matching function uses a similar algorithm to Perl, which stops when it finds the first match, starting at a given point in - the subject. If you want to find all possible matches, or the longest - possible match, consider using the alternative matching function (see - below) instead. If you cannot use the alternative function, but still - need to find all possible matches, you can kludge it up by making use + the subject. If you want to find all possible matches, or the longest + possible match, consider using the alternative matching function (see + below) instead. If you cannot use the alternative function, but still + need to find all possible matches, you can kludge it up by making use of the callout facility, which is described in the pcrecallout documen- tation. What you have to do is to insert a callout right at the end of the pat- - tern. When your callout function is called, extract and save the cur- - rent matched substring. Then return 1, which forces pcre_exec() to - backtrack and try other alternatives. Ultimately, when it runs out of + tern. When your callout function is called, extract and save the cur- + rent matched substring. Then return 1, which forces pcre_exec() to + backtrack and try other alternatives. Ultimately, when it runs out of matches, pcre_exec() will yield PCRE_ERROR_NOMATCH. OBTAINING AN ESTIMATE OF STACK USAGE - Matching certain patterns using pcre_exec() can use a lot of process - stack, which in certain environments can be rather limited in size. - Some users find it helpful to have an estimate of the amount of stack - that is used by pcre_exec(), to help them set recursion limits, as - described in the pcrestack documentation. The estimate that is output + Matching certain patterns using pcre_exec() can use a lot of process + stack, which in certain environments can be rather limited in size. + Some users find it helpful to have an estimate of the amount of stack + that is used by pcre_exec(), to help them set recursion limits, as + described in the pcrestack documentation. The estimate that is output by pcretest when called with the -m and -C options is obtained by call- - ing pcre_exec with the values NULL, NULL, NULL, -999, and -999 for its + ing pcre_exec with the values NULL, NULL, NULL, -999, and -999 for its first five arguments. - Normally, if its first argument is NULL, pcre_exec() immediately - returns the negative error code PCRE_ERROR_NULL, but with this special - combination of arguments, it returns instead a negative number whose - absolute value is the approximate stack frame size in bytes. (A nega- - tive number is used so that it is clear that no match has happened.) - The value is approximate because in some cases, recursive calls to + Normally, if its first argument is NULL, pcre_exec() immediately + returns the negative error code PCRE_ERROR_NULL, but with this special + combination of arguments, it returns instead a negative number whose + absolute value is the approximate stack frame size in bytes. (A nega- + tive number is used so that it is clear that no match has happened.) + The value is approximate because in some cases, recursive calls to pcre_exec() occur when there are one or two additional variables on the stack. - If PCRE has been compiled to use the heap instead of the stack for - recursion, the value returned is the size of each block that is + If PCRE has been compiled to use the heap instead of the stack for + recursion, the value returned is the size of each block that is obtained from the heap. @@ -3313,26 +4058,26 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION int options, int *ovector, int ovecsize, int *workspace, int wscount); - The function pcre_dfa_exec() is called to match a subject string - against a compiled pattern, using a matching algorithm that scans the - subject string just once, and does not backtrack. This has different - characteristics to the normal algorithm, and is not compatible with - Perl. Some of the features of PCRE patterns are not supported. Never- - theless, there are times when this kind of matching can be useful. For - a discussion of the two matching algorithms, and a list of features - that pcre_dfa_exec() does not support, see the pcrematching documenta- + The function pcre_dfa_exec() is called to match a subject string + against a compiled pattern, using a matching algorithm that scans the + subject string just once, and does not backtrack. This has different + characteristics to the normal algorithm, and is not compatible with + Perl. Some of the features of PCRE patterns are not supported. Never- + theless, there are times when this kind of matching can be useful. For + a discussion of the two matching algorithms, and a list of features + that pcre_dfa_exec() does not support, see the pcrematching documenta- tion. - The arguments for the pcre_dfa_exec() function are the same as for + The arguments for the pcre_dfa_exec() function are the same as for pcre_exec(), plus two extras. The ovector argument is used in a differ- - ent way, and this is described below. The other common arguments are - used in the same way as for pcre_exec(), so their description is not + ent way, and this is described below. The other common arguments are + used in the same way as for pcre_exec(), so their description is not repeated here. - The two additional arguments provide workspace for the function. The - workspace vector should contain at least 20 elements. It is used for + The two additional arguments provide workspace for the function. The + workspace vector should contain at least 20 elements. It is used for keeping track of multiple paths through the pattern tree. More - workspace will be needed for patterns and subjects where there are a + workspace will be needed for patterns and subjects where there are a lot of potential matches. Here is an example of a simple call to pcre_dfa_exec(): @@ -3354,55 +4099,55 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION Option bits for pcre_dfa_exec() - The unused bits of the options argument for pcre_dfa_exec() must be - zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEW- + The unused bits of the options argument for pcre_dfa_exec() must be + zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEW- LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, - PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, - PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR- - TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last - four of these are exactly the same as for pcre_exec(), so their + PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, + PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR- + TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last + four of these are exactly the same as for pcre_exec(), so their description is not repeated here. PCRE_PARTIAL_HARD PCRE_PARTIAL_SOFT - These have the same general effect as they do for pcre_exec(), but the - details are slightly different. When PCRE_PARTIAL_HARD is set for - pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of the sub- - ject is reached and there is still at least one matching possibility + These have the same general effect as they do for pcre_exec(), but the + details are slightly different. When PCRE_PARTIAL_HARD is set for + pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of the sub- + ject is reached and there is still at least one matching possibility that requires additional characters. This happens even if some complete matches have also been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end - of the subject is reached, there have been no complete matches, but - there is still at least one matching possibility. The portion of the - string that was inspected when the longest partial match was found is - set as the first matching string in both cases. There is a more - detailed discussion of partial and multi-segment matching, with exam- + of the subject is reached, there have been no complete matches, but + there is still at least one matching possibility. The portion of the + string that was inspected when the longest partial match was found is + set as the first matching string in both cases. There is a more + detailed discussion of partial and multi-segment matching, with exam- ples, in the pcrepartial documentation. PCRE_DFA_SHORTEST - Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to + Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as soon as it has found one match. Because of the way the alterna- - tive algorithm works, this is necessarily the shortest possible match + tive algorithm works, this is necessarily the shortest possible match at the first possible matching point in the subject string. PCRE_DFA_RESTART When pcre_dfa_exec() returns a partial match, it is possible to call it - again, with additional subject characters, and have it continue with - the same match. The PCRE_DFA_RESTART option requests this action; when - it is set, the workspace and wscount options must reference the same - vector as before because data about the match so far is left in them + again, with additional subject characters, and have it continue with + the same match. The PCRE_DFA_RESTART option requests this action; when + it is set, the workspace and wscount options must reference the same + vector as before because data about the match so far is left in them after a partial match. There is more discussion of this facility in the pcrepartial documentation. Successful returns from pcre_dfa_exec() - When pcre_dfa_exec() succeeds, it may have matched more than one sub- + When pcre_dfa_exec() succeeds, it may have matched more than one sub- string in the subject. Note, however, that all the matches from one run - of the function start at the same point in the subject. The shorter - matches are all initial substrings of the longer matches. For example, + of the function start at the same point in the subject. The shorter + matches are all initial substrings of the longer matches. For example, if the pattern <.*> @@ -3417,21 +4162,30 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION - On success, the yield of the function is a number greater than zero, - which is the number of matched substrings. The substrings themselves - are returned in ovector. Each string uses two elements; the first is - the offset to the start, and the second is the offset to the end. In - fact, all the strings have the same start offset. (Space could have - been saved by giving this only once, but it was decided to retain some - compatibility with the way pcre_exec() returns data, even though the + On success, the yield of the function is a number greater than zero, + which is the number of matched substrings. The substrings themselves + are returned in ovector. Each string uses two elements; the first is + the offset to the start, and the second is the offset to the end. In + fact, all the strings have the same start offset. (Space could have + been saved by giving this only once, but it was decided to retain some + compatibility with the way pcre_exec() returns data, even though the meaning of the strings is different.) The strings are returned in reverse order of length; that is, the long- - est matching string is given first. If there were too many matches to - fit into ovector, the yield of the function is zero, and the vector is - filled with the longest matches. Unlike pcre_exec(), pcre_dfa_exec() + est matching string is given first. If there were too many matches to + fit into ovector, the yield of the function is zero, and the vector is + filled with the longest matches. Unlike pcre_exec(), pcre_dfa_exec() can use the entire ovector for returning matched strings. + NOTE: PCRE's "auto-possessification" optimization usually applies to + character repeats at the end of a pattern (as well as internally). For + example, the pattern "a\d+" is compiled as if it were "a\d++" because + there is no point even considering the possibility of backtracking into + the repeated digits. For DFA matching, this means that only one possi- + ble match is found. If you really do want multiple matches in such + cases, either use an ungreedy repeat ("a\d+?") or set the + PCRE_NO_AUTO_POSSESS option when compiling. + Error returns from pcre_dfa_exec() The pcre_dfa_exec() function returns a negative number when it fails. @@ -3480,9 +4234,9 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION SEE ALSO - pcre16(3), pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematch- - ing(3), pcrepartial(3), pcreposix(3), pcreprecompile(3), pcresample(3), - pcrestack(3). + pcre16(3), pcre32(3), pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), + pcrematching(3), pcrepartial(3), pcreposix(3), pcreprecompile(3), pcre- + sample(3), pcrestack(3). AUTHOR @@ -3494,30 +4248,37 @@ AUTHOR REVISION - Last updated: 17 June 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 12 November 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCRECALLOUT(3) PCRECALLOUT(3) +PCRECALLOUT(3) Library Functions Manual PCRECALLOUT(3) + NAME PCRE - Perl-compatible regular expressions +SYNOPSIS -PCRE CALLOUTS + #include int (*pcre_callout)(pcre_callout_block *); int (*pcre16_callout)(pcre16_callout_block *); + int (*pcre32_callout)(pcre32_callout_block *); + + +DESCRIPTION + PCRE provides a feature called "callout", which is a means of temporar- ily passing control to the caller of PCRE in the middle of pattern matching. The caller of PCRE provides an external function by putting its entry point in the global variable pcre_callout (pcre16_callout for - the 16-bit library). By default, this variable contains NULL, which - disables all calling out. + the 16-bit library, pcre32_callout for the 32-bit library). By default, + this variable contains NULL, which disables all calling out. Within a regular expression, (?C) indicates the points at which the external function is to be called. Different callout points can be @@ -3539,54 +4300,96 @@ PCRE CALLOUTS (?C255)A(?C255)((?C255)\d{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255) Notice that there is a callout before and after each parenthesis and - alternation bar. Automatic callouts can be used for tracking the - progress of pattern matching. The pcretest command has an option that - sets automatic callouts; when it is used, the output indicates how the - pattern is matched. This is useful information when you are trying to - optimize the performance of a particular pattern. + alternation bar. If the pattern contains a conditional group whose con- + dition is an assertion, an automatic callout is inserted immediately + before the condition. Such a callout may also be inserted explicitly, + for example: - The use of callouts in a pattern makes it ineligible for optimization - by the just-in-time compiler. Studying such a pattern with the - PCRE_STUDY_JIT_COMPILE option always fails. + (?(?C9)(?=a)ab|de) + This applies only to assertion conditions (because they are themselves + independent groups). + Automatic callouts can be used for tracking the progress of pattern + matching. The pcretest program has a pattern qualifier (/C) that sets + automatic callouts; when it is used, the output indicates how the pat- + tern is being matched. This is useful information when you are trying + to optimize the performance of a particular pattern. + + MISSING CALLOUTS - You should be aware that, because of optimizations in the way PCRE - matches patterns by default, callouts sometimes do not happen. For - example, if the pattern is + You should be aware that, because of optimizations in the way PCRE com- + piles and matches patterns, callouts sometimes do not happen exactly as + you might expect. + At compile time, PCRE "auto-possessifies" repeated items when it knows + that what follows cannot be part of the repeat. For example, a+[bc] is + compiled as if it were a++[bc]. The pcretest output when this pattern + is anchored and then applied with automatic callouts to the string + "aaaa" is: + + --->aaaa + +0 ^ ^ + +1 ^ a+ + +3 ^ ^ [bc] + No match + + This indicates that when matching [bc] fails, there is no backtracking + into a+ and therefore the callouts that would be taken for the back- + tracks do not occur. You can disable the auto-possessify feature by + passing PCRE_NO_AUTO_POSSESS to pcre_compile(), or starting the pattern + with (*NO_AUTO_POSSESS). If this is done in pcretest (using the /O + qualifier), the output changes to this: + + --->aaaa + +0 ^ ^ + +1 ^ a+ + +3 ^ ^ [bc] + +3 ^ ^ [bc] + +3 ^ ^ [bc] + +3 ^^ [bc] + No match + + This time, when matching [bc] fails, the matcher backtracks into a+ and + tries again, repeatedly, until a+ itself fails. + + Other optimizations that provide fast "no match" results also affect + callouts. For example, if the pattern is + ab(?C4)cd PCRE knows that any matching string must contain the letter "d". If the - subject string is "abyz", the lack of "d" means that matching doesn't - ever start, and the callout is never reached. However, with "abyd", + subject string is "abyz", the lack of "d" means that matching doesn't + ever start, and the callout is never reached. However, with "abyd", though the result is still no match, the callout is obeyed. - If the pattern is studied, PCRE knows the minimum length of a matching - string, and will immediately give a "no match" return without actually - running a match if the subject is not long enough, or, for unanchored + If the pattern is studied, PCRE knows the minimum length of a matching + string, and will immediately give a "no match" return without actually + running a match if the subject is not long enough, or, for unanchored patterns, if it has been scanned far enough. - You can disable these optimizations by passing the PCRE_NO_START_OPTI- - MIZE option to the matching function, or by starting the pattern with - (*NO_START_OPT). This slows down the matching process, but does ensure + You can disable these optimizations by passing the PCRE_NO_START_OPTI- + MIZE option to the matching function, or by starting the pattern with + (*NO_START_OPT). This slows down the matching process, but does ensure that callouts such as the example above are obeyed. THE CALLOUT INTERFACE - During matching, when PCRE reaches a callout point, the external func- - tion defined by pcre_callout or pcre16_callout is called (if it is - set). This applies to both normal and DFA matching. The only argument - to the callout function is a pointer to a pcre_callout or pcre16_call- - out block. These structures contains the following fields: + During matching, when PCRE reaches a callout point, the external func- + tion defined by pcre_callout or pcre[16|32]_callout is called (if it is + set). This applies to both normal and DFA matching. The only argument + to the callout function is a pointer to a pcre_callout or + pcre[16|32]_callout block. These structures contains the following + fields: int version; int callout_number; int *offset_vector; const char *subject; (8-bit version) PCRE_SPTR16 subject; (16-bit version) + PCRE_SPTR32 subject; (32-bit version) int subject_length; int start_match; int current_position; @@ -3597,6 +4400,7 @@ THE CALLOUT INTERFACE int next_item_length; const unsigned char *mark; (8-bit version) const PCRE_UCHAR16 *mark; (16-bit version) + const PCRE_UCHAR32 *mark; (32-bit version) The version field is an integer containing the version number of the block format. The initial version was 0; the current version is 2. The @@ -3609,7 +4413,7 @@ THE CALLOUT INTERFACE The offset_vector field is a pointer to the vector of offsets that was passed by the caller to the matching function. When pcre_exec() or - pcre16_exec() is used, the contents can be inspected, in order to + pcre[16|32]_exec() is used, the contents can be inspected, in order to extract substrings that have been matched so far, in the same way as for extracting substrings after a match has completed. For the DFA matching functions, this field is not useful. @@ -3627,60 +4431,63 @@ THE CALLOUT INTERFACE The current_position field contains the offset within the subject of the current match pointer. - When the pcre_exec() or pcre16_exec() is used, the capture_top field - contains one more than the number of the highest numbered captured sub- - string so far. If no substrings have been captured, the value of cap- - ture_top is one. This is always the case when the DFA functions are - used, because they do not support captured substrings. + When the pcre_exec() or pcre[16|32]_exec() is used, the capture_top + field contains one more than the number of the highest numbered cap- + tured substring so far. If no substrings have been captured, the value + of capture_top is one. This is always the case when the DFA functions + are used, because they do not support captured substrings. The capture_last field contains the number of the most recently cap- - tured substring. If no substrings have been captured, its value is -1. - This is always the case for the DFA matching functions. + tured substring. However, when a recursion exits, the value reverts to + what it was outside the recursion, as do the values of all captured + substrings. If no substrings have been captured, the value of cap- + ture_last is -1. This is always the case for the DFA matching func- + tions. - The callout_data field contains a value that is passed to a matching - function specifically so that it can be passed back in callouts. It is - passed in the callout_data field of a pcre_extra or pcre16_extra data - structure. If no such data was passed, the value of callout_data in a - callout block is NULL. There is a description of the pcre_extra struc- - ture in the pcreapi documentation. + The callout_data field contains a value that is passed to a matching + function specifically so that it can be passed back in callouts. It is + passed in the callout_data field of a pcre_extra or pcre[16|32]_extra + data structure. If no such data was passed, the value of callout_data + in a callout block is NULL. There is a description of the pcre_extra + structure in the pcreapi documentation. - The pattern_position field is present from version 1 of the callout + The pattern_position field is present from version 1 of the callout structure. It contains the offset to the next item to be matched in the pattern string. - The next_item_length field is present from version 1 of the callout + The next_item_length field is present from version 1 of the callout structure. It contains the length of the next item to be matched in the - pattern string. When the callout immediately precedes an alternation - bar, a closing parenthesis, or the end of the pattern, the length is - zero. When the callout precedes an opening parenthesis, the length is + pattern string. When the callout immediately precedes an alternation + bar, a closing parenthesis, or the end of the pattern, the length is + zero. When the callout precedes an opening parenthesis, the length is that of the entire subpattern. - The pattern_position and next_item_length fields are intended to help - in distinguishing between different automatic callouts, which all have + The pattern_position and next_item_length fields are intended to help + in distinguishing between different automatic callouts, which all have the same callout number. However, they are set for all callouts. - The mark field is present from version 2 of the callout structure. In - callouts from pcre_exec() or pcre16_exec() it contains a pointer to the - zero-terminated name of the most recently passed (*MARK), (*PRUNE), or - (*THEN) item in the match, or NULL if no such items have been passed. - Instances of (*PRUNE) or (*THEN) without a name do not obliterate a - previous (*MARK). In callouts from the DFA matching functions this - field always contains NULL. + The mark field is present from version 2 of the callout structure. In + callouts from pcre_exec() or pcre[16|32]_exec() it contains a pointer + to the zero-terminated name of the most recently passed (*MARK), + (*PRUNE), or (*THEN) item in the match, or NULL if no such items have + been passed. Instances of (*PRUNE) or (*THEN) without a name do not + obliterate a previous (*MARK). In callouts from the DFA matching func- + tions this field always contains NULL. RETURN VALUES - The external callout function returns an integer to PCRE. If the value - is zero, matching proceeds as normal. If the value is greater than - zero, matching fails at the current point, but the testing of other + The external callout function returns an integer to PCRE. If the value + is zero, matching proceeds as normal. If the value is greater than + zero, matching fails at the current point, but the testing of other matching possibilities goes ahead, just as if a lookahead assertion had - failed. If the value is less than zero, the match is abandoned, the + failed. If the value is less than zero, the match is abandoned, the matching function returns the negative value. - Negative values should normally be chosen from the set of + Negative values should normally be chosen from the set of PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan- - dard "no match" failure. The error number PCRE_ERROR_CALLOUT is - reserved for use by callout functions; it will never be used by PCRE + dard "no match" failure. The error number PCRE_ERROR_CALLOUT is + reserved for use by callout functions; it will never be used by PCRE itself. @@ -3693,18 +4500,18 @@ AUTHOR REVISION - Last updated: 08 Janurary 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 12 November 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCRECOMPAT(3) PCRECOMPAT(3) +PCRECOMPAT(3) Library Functions Manual PCRECOMPAT(3) + NAME PCRE - Perl-compatible regular expressions - DIFFERENCES BETWEEN PCRE AND PERL This document describes the differences in the ways that PCRE and Perl @@ -3723,10 +4530,8 @@ DIFFERENCES BETWEEN PCRE AND PERL 3. Capturing subpatterns that occur inside negative lookahead asser- tions are counted, but their entries in the offsets vector are never - set. Perl sets its numerical variables from any such patterns that are - matched before the assertion fails to match something (thereby succeed- - ing), but only if the negative lookahead assertion contains just one - branch. + set. Perl sometimes (but not always) sets its numerical variables from + inside negative assertions. 4. Though binary zero characters are supported in the subject string, they are not allowed in a pattern string because it is passed as a nor- @@ -3752,15 +4557,10 @@ DIFFERENCES BETWEEN PCRE AND PERL tion of Unicode characters, there is no need to implement the somewhat messy concept of surrogates." - 7. PCRE implements a simpler version of \X than Perl, which changed to - make \X match what Unicode calls an "extended grapheme cluster". This - is more complicated than an extended Unicode sequence, which is what - PCRE matches. - - 8. PCRE does support the \Q...\E escape for quoting substrings. Charac- - ters in between are treated as literals. This is slightly different - from Perl in that $ and @ are also handled as literals inside the - quotes. In Perl, they cause variable interpolation (but of course PCRE + 7. PCRE does support the \Q...\E escape for quoting substrings. Charac- + ters in between are treated as literals. This is slightly different + from Perl in that $ and @ are also handled as literals inside the + quotes. In Perl, they cause variable interpolation (but of course PCRE does not have variables). Note the following examples: Pattern PCRE matches Perl matches @@ -3770,56 +4570,75 @@ DIFFERENCES BETWEEN PCRE AND PERL \Qabc\$xyz\E abc\$xyz abc\$xyz \Qabc\E\$\Qxyz\E abc$xyz abc$xyz - The \Q...\E sequence is recognized both inside and outside character + The \Q...\E sequence is recognized both inside and outside character classes. - 9. Fairly obviously, PCRE does not support the (?{code}) and (??{code}) - constructions. However, there is support for recursive patterns. This - is not available in Perl 5.8, but it is in Perl 5.10. Also, the PCRE - "callout" feature allows an external function to be called during pat- + 8. Fairly obviously, PCRE does not support the (?{code}) and (??{code}) + constructions. However, there is support for recursive patterns. This + is not available in Perl 5.8, but it is in Perl 5.10. Also, the PCRE + "callout" feature allows an external function to be called during pat- tern matching. See the pcrecallout documentation for details. - 10. Subpatterns that are called as subroutines (whether or not recur- - sively) are always treated as atomic groups in PCRE. This is like - Python, but unlike Perl. Captured values that are set outside a sub- - routine call can be reference from inside in PCRE, but not in Perl. + 9. Subpatterns that are called as subroutines (whether or not recur- + sively) are always treated as atomic groups in PCRE. This is like + Python, but unlike Perl. Captured values that are set outside a sub- + routine call can be reference from inside in PCRE, but not in Perl. There is a discussion that explains these differences in more detail in the section on recursion differences from Perl in the pcrepattern page. - 11. If any of the backtracking control verbs are used in an assertion - or in a subpattern that is called as a subroutine (whether or not - recursively), their effect is confined to that subpattern; it does not - extend to the surrounding pattern. This is not always the case in Perl. - In particular, if (*THEN) is present in a group that is called as a - subroutine, its action is limited to that group, even if the group does - not contain any | characters. There is one exception to this: the name - from a *(MARK), (*PRUNE), or (*THEN) that is encountered in a success- - ful positive assertion is passed back when a match succeeds (compare - capturing parentheses in assertions). Note that such subpatterns are - processed as anchored at the point where they are tested. + 10. If any of the backtracking control verbs are used in a subpattern + that is called as a subroutine (whether or not recursively), their + effect is confined to that subpattern; it does not extend to the sur- + rounding pattern. This is not always the case in Perl. In particular, + if (*THEN) is present in a group that is called as a subroutine, its + action is limited to that group, even if the group does not contain any + | characters. Note that such subpatterns are processed as anchored at + the point where they are tested. - 12. There are some differences that are concerned with the settings of - captured strings when part of a pattern is repeated. For example, - matching "aba" against the pattern /^(a(b)?)+$/ in Perl leaves $2 + 11. If a pattern contains more than one backtracking control verb, the + first one that is backtracked onto acts. For example, in the pattern + A(*COMMIT)B(*PRUNE)C a failure in B triggers (*COMMIT), but a failure + in C triggers (*PRUNE). Perl's behaviour is more complex; in many cases + it is the same as PCRE, but there are examples where it differs. + + 12. Most backtracking verbs in assertions have their normal actions. + They are not confined to the assertion. + + 13. There are some differences that are concerned with the settings of + captured strings when part of a pattern is repeated. For example, + matching "aba" against the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE it is set to "b". - 13. PCRE's handling of duplicate subpattern numbers and duplicate sub- + 14. PCRE's handling of duplicate subpattern numbers and duplicate sub- pattern names is not as general as Perl's. This is a consequence of the fact the PCRE works internally just with numbers, using an external ta- - ble to translate between numbers and names. In particular, a pattern - such as (?|(?A)|(?A)|(?\r\n|\n|\x0b|\f|\r|\x85) - This is an example of an "atomic group", details of which are given + This is an example of an "atomic group", details of which are given below. This particular group matches either the two-character sequence - CR followed by LF, or one of the single characters LF (linefeed, - U+000A), VT (vertical tab, U+000B), FF (form feed, U+000C), CR (car- - riage return, U+000D), or NEL (next line, U+0085). The two-character + CR followed by LF, or one of the single characters LF (linefeed, + U+000A), VT (vertical tab, U+000B), FF (form feed, U+000C), CR (car- + riage return, U+000D), or NEL (next line, U+0085). The two-character sequence is treated as a single unit that cannot be split. - In other modes, two additional characters whose codepoints are greater + In other modes, two additional characters whose codepoints are greater than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa- - rator, U+2029). Unicode character property support is not needed for + rator, U+2029). Unicode character property support is not needed for these characters to be recognized. It is possible to restrict \R to match only CR, LF, or CRLF (instead of - the complete set of Unicode line endings) by setting the option + the complete set of Unicode line endings) by setting the option PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched. (BSR is an abbrevation for "backslash R".) This can be made the default - when PCRE is built; if this is the case, the other behaviour can be - requested via the PCRE_BSR_UNICODE option. It is also possible to - specify these settings by starting a pattern string with one of the + when PCRE is built; if this is the case, the other behaviour can be + requested via the PCRE_BSR_UNICODE option. It is also possible to + specify these settings by starting a pattern string with one of the following sequences: (*BSR_ANYCRLF) CR, LF, or CRLF only (*BSR_UNICODE) any Unicode newline sequence These override the default and the options given to the compiling func- - tion, but they can themselves be overridden by options given to a - matching function. Note that these special settings, which are not - Perl-compatible, are recognized only at the very start of a pattern, - and that they must be in upper case. If more than one of them is - present, the last one is used. They can be combined with a change of + tion, but they can themselves be overridden by options given to a + matching function. Note that these special settings, which are not + Perl-compatible, are recognized only at the very start of a pattern, + and that they must be in upper case. If more than one of them is + present, the last one is used. They can be combined with a change of newline convention; for example, a pattern can start with: (*ANY)(*BSR_ANYCRLF) - They can also be combined with the (*UTF8), (*UTF16), or (*UCP) special - sequences. Inside a character class, \R is treated as an unrecognized - escape sequence, and so matches the letter "R" by default, but causes - an error if PCRE_EXTRA is set. + They can also be combined with the (*UTF8), (*UTF16), (*UTF32), (*UTF) + or (*UCP) special sequences. Inside a character class, \R is treated as + an unrecognized escape sequence, and so matches the letter "R" by + default, but causes an error if PCRE_EXTRA is set. Unicode character properties When PCRE is built with Unicode character property support, three addi- - tional escape sequences that match characters with specific properties - are available. When in 8-bit non-UTF-8 mode, these sequences are of - course limited to testing characters whose codepoints are less than + tional escape sequences that match characters with specific properties + are available. When in 8-bit non-UTF-8 mode, these sequences are of + course limited to testing characters whose codepoints are less than 256, but they do work in this mode. The extra escape sequences are: \p{xx} a character with the xx property \P{xx} a character without the xx property - \X an extended Unicode sequence + \X a Unicode extended grapheme cluster - The property names represented by xx above are limited to the Unicode + The property names represented by xx above are limited to the Unicode script names, the general category properties, "Any", which matches any - character (including newline), and some special PCRE properties - (described in the next section). Other Perl properties such as "InMu- - sicalSymbols" are not currently supported by PCRE. Note that \P{Any} + character (including newline), and some special PCRE properties + (described in the next section). Other Perl properties such as "InMu- + sicalSymbols" are not currently supported by PCRE. Note that \P{Any} does not match any characters, so always causes a match failure. Sets of Unicode characters are defined as belonging to certain scripts. - A character from one of these sets can be matched using a script name. + A character from one of these sets can be matched using a script name. For example: \p{Greek} \P{Han} - Those that are not part of an identified script are lumped together as + Those that are not part of an identified script are lumped together as "Common". The current list of scripts is: - Arabic, Armenian, Avestan, Balinese, Bamum, Batak, Bengali, Bopomofo, - Brahmi, Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Chakma, - Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot, Cyrillic, Deseret, - Devanagari, Egyptian_Hieroglyphs, Ethiopic, Georgian, Glagolitic, - Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira- - gana, Imperial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscrip- - tional_Parthian, Javanese, Kaithi, Kannada, Katakana, Kayah_Li, - Kharoshthi, Khmer, Lao, Latin, Lepcha, Limbu, Linear_B, Lisu, Lycian, + Arabic, Armenian, Avestan, Balinese, Bamum, Batak, Bengali, Bopomofo, + Brahmi, Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Chakma, + Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot, Cyrillic, Deseret, + Devanagari, Egyptian_Hieroglyphs, Ethiopic, Georgian, Glagolitic, + Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira- + gana, Imperial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscrip- + tional_Parthian, Javanese, Kaithi, Kannada, Katakana, Kayah_Li, + Kharoshthi, Khmer, Lao, Latin, Lepcha, Limbu, Linear_B, Lisu, Lycian, Lydian, Malayalam, Mandaic, Meetei_Mayek, Meroitic_Cursive, - Meroitic_Hieroglyphs, Miao, Mongolian, Myanmar, New_Tai_Lue, Nko, - Ogham, Old_Italic, Old_Persian, Old_South_Arabian, Old_Turkic, - Ol_Chiki, Oriya, Osmanya, Phags_Pa, Phoenician, Rejang, Runic, Samari- - tan, Saurashtra, Sharada, Shavian, Sinhala, Sora_Sompeng, Sundanese, - Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tai_Tham, Tai_Viet, - Takri, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Vai, + Meroitic_Hieroglyphs, Miao, Mongolian, Myanmar, New_Tai_Lue, Nko, + Ogham, Old_Italic, Old_Persian, Old_South_Arabian, Old_Turkic, + Ol_Chiki, Oriya, Osmanya, Phags_Pa, Phoenician, Rejang, Runic, Samari- + tan, Saurashtra, Sharada, Shavian, Sinhala, Sora_Sompeng, Sundanese, + Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tai_Tham, Tai_Viet, + Takri, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Vai, Yi. Each character has exactly one Unicode general category property, spec- - ified by a two-letter abbreviation. For compatibility with Perl, nega- - tion can be specified by including a circumflex between the opening - brace and the property name. For example, \p{^Lu} is the same as + ified by a two-letter abbreviation. For compatibility with Perl, nega- + tion can be specified by including a circumflex between the opening + brace and the property name. For example, \p{^Lu} is the same as \P{Lu}. If only one letter is specified with \p or \P, it includes all the gen- - eral category properties that start with that letter. In this case, in - the absence of negation, the curly brackets in the escape sequence are + eral category properties that start with that letter. In this case, in + the absence of negation, the curly brackets in the escape sequence are optional; these two examples have the same effect: \p{L} @@ -4478,98 +5386,138 @@ BACKSLASH Zp Paragraph separator Zs Space separator - The special property L& is also supported: it matches a character that - has the Lu, Ll, or Lt property, in other words, a letter that is not + The special property L& is also supported: it matches a character that + has the Lu, Ll, or Lt property, in other words, a letter that is not classified as a modifier or "other". - The Cs (Surrogate) property applies only to characters in the range - U+D800 to U+DFFF. Such characters are not valid in Unicode strings and - so cannot be tested by PCRE, unless UTF validity checking has been - turned off (see the discussion of PCRE_NO_UTF8_CHECK and - PCRE_NO_UTF16_CHECK in the pcreapi page). Perl does not support the Cs - property. + The Cs (Surrogate) property applies only to characters in the range + U+D800 to U+DFFF. Such characters are not valid in Unicode strings and + so cannot be tested by PCRE, unless UTF validity checking has been + turned off (see the discussion of PCRE_NO_UTF8_CHECK, + PCRE_NO_UTF16_CHECK and PCRE_NO_UTF32_CHECK in the pcreapi page). Perl + does not support the Cs property. - The long synonyms for property names that Perl supports (such as - \p{Letter}) are not supported by PCRE, nor is it permitted to prefix + The long synonyms for property names that Perl supports (such as + \p{Letter}) are not supported by PCRE, nor is it permitted to prefix any of these properties with "Is". No character that is in the Unicode table has the Cn (unassigned) prop- erty. Instead, this property is assumed for any code point that is not in the Unicode table. - Specifying caseless matching does not affect these escape sequences. - For example, \p{Lu} always matches only upper case letters. + Specifying caseless matching does not affect these escape sequences. + For example, \p{Lu} always matches only upper case letters. This is + different from the behaviour of current versions of Perl. - The \X escape matches any number of Unicode characters that form an - extended Unicode sequence. \X is equivalent to + Matching characters by Unicode property is not fast, because PCRE has + to do a multistage table lookup in order to find a character's prop- + erty. That is why the traditional escape sequences such as \d and \w do + not use Unicode properties in PCRE by default, though you can make them + do so by setting the PCRE_UCP option or by starting the pattern with + (*UCP). + Extended grapheme clusters + + The \X escape matches any number of Unicode characters that form an + "extended grapheme cluster", and treats the sequence as an atomic group + (see below). Up to and including release 8.31, PCRE matched an ear- + lier, simpler definition that was equivalent to + (?>\PM\pM*) - That is, it matches a character without the "mark" property, followed - by zero or more characters with the "mark" property, and treats the - sequence as an atomic group (see below). Characters with the "mark" - property are typically accents that affect the preceding character. - None of them have codepoints less than 256, so in 8-bit non-UTF-8 mode - \X matches any one character. + That is, it matched a character without the "mark" property, followed + by zero or more characters with the "mark" property. Characters with + the "mark" property are typically non-spacing accents that affect the + preceding character. - Note that recent versions of Perl have changed \X to match what Unicode - calls an "extended grapheme cluster", which has a more complicated def- - inition. + This simple definition was extended in Unicode to include more compli- + cated kinds of composite character by giving each character a grapheme + breaking property, and creating rules that use these properties to + define the boundaries of extended grapheme clusters. In releases of + PCRE later than 8.31, \X matches one of these clusters. - Matching characters by Unicode property is not fast, because PCRE has - to search a structure that contains data for over fifteen thousand - characters. That is why the traditional escape sequences such as \d and - \w do not use Unicode properties in PCRE by default, though you can - make them do so by setting the PCRE_UCP option or by starting the pat- - tern with (*UCP). + \X always matches at least one character. Then it decides whether to + add additional characters according to the following rules for ending a + cluster: + 1. End at the end of the subject string. + + 2. Do not end between CR and LF; otherwise end after any control char- + acter. + + 3. Do not break Hangul (a Korean script) syllable sequences. Hangul + characters are of five types: L, V, T, LV, and LVT. An L character may + be followed by an L, V, LV, or LVT character; an LV or V character may + be followed by a V or T character; an LVT or T character may be follwed + only by a T character. + + 4. Do not end before extending characters or spacing marks. Characters + with the "mark" property always have the "extend" grapheme breaking + property. + + 5. Do not end after prepend characters. + + 6. Otherwise, end the cluster. + PCRE's additional properties - As well as the standard Unicode properties described in the previous - section, PCRE supports four more that make it possible to convert tra- - ditional escape sequences such as \w and \s and POSIX character classes - to use Unicode properties. PCRE uses these non-standard, non-Perl prop- - erties internally when PCRE_UCP is set. They are: + As well as the standard Unicode properties described above, PCRE sup- + ports four more that make it possible to convert traditional escape + sequences such as \w and \s to use Unicode properties. PCRE uses these + non-standard, non-Perl properties internally when PCRE_UCP is set. How- + ever, they may also be used explicitly. These properties are: Xan Any alphanumeric character Xps Any POSIX space character Xsp Any Perl space character Xwd Any Perl "word" character - Xan matches characters that have either the L (letter) or the N (num- - ber) property. Xps matches the characters tab, linefeed, vertical tab, - form feed, or carriage return, and any other character that has the Z - (separator) property. Xsp is the same as Xps, except that vertical tab - is excluded. Xwd matches the same characters as Xan, plus underscore. + Xan matches characters that have either the L (letter) or the N (num- + ber) property. Xps matches the characters tab, linefeed, vertical tab, + form feed, or carriage return, and any other character that has the Z + (separator) property. Xsp is the same as Xps; it used to exclude ver- + tical tab, for Perl compatibility, but Perl changed, and so PCRE fol- + lowed at release 8.34. Xwd matches the same characters as Xan, plus + underscore. + There is another non-standard property, Xuc, which matches any charac- + ter that can be represented by a Universal Character Name in C++ and + other programming languages. These are the characters $, @, ` (grave + accent), and all characters with Unicode code points greater than or + equal to U+00A0, except for the surrogates U+D800 to U+DFFF. Note that + most base (ASCII) characters are excluded. (Universal Character Names + are of the form \uHHHH or \UHHHHHHHH where H is a hexadecimal digit. + Note that the Xuc property does not match these sequences but the char- + acters that they represent.) + Resetting the match start - The escape sequence \K causes any previously matched characters not to + The escape sequence \K causes any previously matched characters not to be included in the final matched sequence. For example, the pattern: foo\Kbar - matches "foobar", but reports that it has matched "bar". This feature - is similar to a lookbehind assertion (described below). However, in - this case, the part of the subject before the real match does not have - to be of fixed length, as lookbehind assertions do. The use of \K does - not interfere with the setting of captured substrings. For example, + matches "foobar", but reports that it has matched "bar". This feature + is similar to a lookbehind assertion (described below). However, in + this case, the part of the subject before the real match does not have + to be of fixed length, as lookbehind assertions do. The use of \K does + not interfere with the setting of captured substrings. For example, when the pattern (foo)\Kbar matches "foobar", the first substring is still set to "foo". - Perl documents that the use of \K within assertions is "not well - defined". In PCRE, \K is acted upon when it occurs inside positive + Perl documents that the use of \K within assertions is "not well + defined". In PCRE, \K is acted upon when it occurs inside positive assertions, but is ignored in negative assertions. Simple assertions - The final use of backslash is for certain simple assertions. An asser- - tion specifies a condition that has to be met at a particular point in - a match, without consuming any characters from the subject string. The - use of subpatterns for more complicated assertions is described below. + The final use of backslash is for certain simple assertions. An asser- + tion specifies a condition that has to be met at a particular point in + a match, without consuming any characters from the subject string. The + use of subpatterns for more complicated assertions is described below. The backslashed assertions are: \b matches at a word boundary @@ -4580,76 +5528,81 @@ BACKSLASH \z matches only at the end of the subject \G matches at the first matching position in the subject - Inside a character class, \b has a different meaning; it matches the - backspace character. If any other of these assertions appears in a - character class, by default it matches the corresponding literal char- + Inside a character class, \b has a different meaning; it matches the + backspace character. If any other of these assertions appears in a + character class, by default it matches the corresponding literal char- acter (for example, \B matches the letter B). However, if the - PCRE_EXTRA option is set, an "invalid escape sequence" error is gener- + PCRE_EXTRA option is set, an "invalid escape sequence" error is gener- ated instead. - A word boundary is a position in the subject string where the current - character and the previous character do not both match \w or \W (i.e. - one matches \w and the other matches \W), or the start or end of the - string if the first or last character matches \w, respectively. In a - UTF mode, the meanings of \w and \W can be changed by setting the - PCRE_UCP option. When this is done, it also affects \b and \B. Neither - PCRE nor Perl has a separate "start of word" or "end of word" metase- - quence. However, whatever follows \b normally determines which it is. + A word boundary is a position in the subject string where the current + character and the previous character do not both match \w or \W (i.e. + one matches \w and the other matches \W), or the start or end of the + string if the first or last character matches \w, respectively. In a + UTF mode, the meanings of \w and \W can be changed by setting the + PCRE_UCP option. When this is done, it also affects \b and \B. Neither + PCRE nor Perl has a separate "start of word" or "end of word" metase- + quence. However, whatever follows \b normally determines which it is. For example, the fragment \ba matches "a" at the start of a word. - The \A, \Z, and \z assertions differ from the traditional circumflex + The \A, \Z, and \z assertions differ from the traditional circumflex and dollar (described in the next section) in that they only ever match - at the very start and end of the subject string, whatever options are - set. Thus, they are independent of multiline mode. These three asser- + at the very start and end of the subject string, whatever options are + set. Thus, they are independent of multiline mode. These three asser- tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which - affect only the behaviour of the circumflex and dollar metacharacters. - However, if the startoffset argument of pcre_exec() is non-zero, indi- + affect only the behaviour of the circumflex and dollar metacharacters. + However, if the startoffset argument of pcre_exec() is non-zero, indi- cating that matching is to start at a point other than the beginning of - the subject, \A can never match. The difference between \Z and \z is + the subject, \A can never match. The difference between \Z and \z is that \Z matches before a newline at the end of the string as well as at the very end, whereas \z matches only at the end. - The \G assertion is true only when the current matching position is at - the start point of the match, as specified by the startoffset argument - of pcre_exec(). It differs from \A when the value of startoffset is - non-zero. By calling pcre_exec() multiple times with appropriate argu- + The \G assertion is true only when the current matching position is at + the start point of the match, as specified by the startoffset argument + of pcre_exec(). It differs from \A when the value of startoffset is + non-zero. By calling pcre_exec() multiple times with appropriate argu- ments, you can mimic Perl's /g option, and it is in this kind of imple- mentation where \G can be useful. - Note, however, that PCRE's interpretation of \G, as the start of the + Note, however, that PCRE's interpretation of \G, as the start of the current match, is subtly different from Perl's, which defines it as the - end of the previous match. In Perl, these can be different when the - previously matched string was empty. Because PCRE does just one match + end of the previous match. In Perl, these can be different when the + previously matched string was empty. Because PCRE does just one match at a time, it cannot reproduce this behaviour. - If all the alternatives of a pattern begin with \G, the expression is + If all the alternatives of a pattern begin with \G, the expression is anchored to the starting match position, and the "anchored" flag is set in the compiled regular expression. CIRCUMFLEX AND DOLLAR + The circumflex and dollar metacharacters are zero-width assertions. + That is, they test for a particular condition being true without con- + suming any characters from the subject string. + Outside a character class, in the default matching mode, the circumflex - character is an assertion that is true only if the current matching - point is at the start of the subject string. If the startoffset argu- - ment of pcre_exec() is non-zero, circumflex can never match if the - PCRE_MULTILINE option is unset. Inside a character class, circumflex + character is an assertion that is true only if the current matching + point is at the start of the subject string. If the startoffset argu- + ment of pcre_exec() is non-zero, circumflex can never match if the + PCRE_MULTILINE option is unset. Inside a character class, circumflex has an entirely different meaning (see below). - Circumflex need not be the first character of the pattern if a number - of alternatives are involved, but it should be the first thing in each - alternative in which it appears if the pattern is ever to match that - branch. If all possible alternatives start with a circumflex, that is, - if the pattern is constrained to match only at the start of the sub- - ject, it is said to be an "anchored" pattern. (There are also other + Circumflex need not be the first character of the pattern if a number + of alternatives are involved, but it should be the first thing in each + alternative in which it appears if the pattern is ever to match that + branch. If all possible alternatives start with a circumflex, that is, + if the pattern is constrained to match only at the start of the sub- + ject, it is said to be an "anchored" pattern. (There are also other constructs that can cause a pattern to be anchored.) - A dollar character is an assertion that is true only if the current - matching point is at the end of the subject string, or immediately - before a newline at the end of the string (by default). Dollar need not - be the last character of the pattern if a number of alternatives are - involved, but it should be the last item in any branch in which it - appears. Dollar has no special meaning in a character class. + The dollar character is an assertion that is true only if the current + matching point is at the end of the subject string, or immediately + before a newline at the end of the string (by default). Note, however, + that it does not actually match the newline. Dollar need not be the + last character of the pattern if a number of alternatives are involved, + but it should be the last item in any branch in which it appears. Dol- + lar has no special meaning in a character class. The meaning of dollar can be changed so that it matches only at the very end of the string, by setting the PCRE_DOLLAR_ENDONLY option at @@ -4710,25 +5663,26 @@ MATCHING A SINGLE DATA UNIT Outside a character class, the escape sequence \C matches any one data unit, whether or not a UTF mode is set. In the 8-bit library, one data - unit is one byte; in the 16-bit library it is a 16-bit unit. Unlike a - dot, \C always matches line-ending characters. The feature is provided - in Perl in order to match individual bytes in UTF-8 mode, but it is - unclear how it can usefully be used. Because \C breaks up characters - into individual data units, matching one unit with \C in a UTF mode - means that the rest of the string may start with a malformed UTF char- - acter. This has undefined results, because PCRE assumes that it is - dealing with valid UTF strings (and by default it checks this at the - start of processing unless the PCRE_NO_UTF8_CHECK or - PCRE_NO_UTF16_CHECK option is used). + unit is one byte; in the 16-bit library it is a 16-bit unit; in the + 32-bit library it is a 32-bit unit. Unlike a dot, \C always matches + line-ending characters. The feature is provided in Perl in order to + match individual bytes in UTF-8 mode, but it is unclear how it can use- + fully be used. Because \C breaks up characters into individual data + units, matching one unit with \C in a UTF mode means that the rest of + the string may start with a malformed UTF character. This has undefined + results, because PCRE assumes that it is dealing with valid UTF strings + (and by default it checks this at the start of processing unless the + PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK or PCRE_NO_UTF32_CHECK option + is used). - PCRE does not allow \C to appear in lookbehind assertions (described - below) in a UTF mode, because this would make it impossible to calcu- + PCRE does not allow \C to appear in lookbehind assertions (described + below) in a UTF mode, because this would make it impossible to calcu- late the length of the lookbehind. In general, the \C escape sequence is best avoided. However, one way of - using it that avoids the problem of malformed UTF characters is to use - a lookahead to check the length of the next character, as in this pat- - tern, which could be used with a UTF-8 string (ignore white space and + using it that avoids the problem of malformed UTF characters is to use + a lookahead to check the length of the next character, as in this pat- + tern, which could be used with a UTF-8 string (ignore white space and line breaks): (?| (?=[\x00-\x7f])(\C) | @@ -4736,11 +5690,11 @@ MATCHING A SINGLE DATA UNIT (?=[\x{800}-\x{ffff}])(\C)(\C)(\C) | (?=[\x{10000}-\x{1fffff}])(\C)(\C)(\C)(\C)) - A group that starts with (?| resets the capturing parentheses numbers - in each alternative (see "Duplicate Subpattern Numbers" below). The - assertions at the start of each branch check the next UTF-8 character - for values whose encoding uses 1, 2, 3, or 4 bytes, respectively. The - character's individual bytes are then captured by the appropriate num- + A group that starts with (?| resets the capturing parentheses numbers + in each alternative (see "Duplicate Subpattern Numbers" below). The + assertions at the start of each branch check the next UTF-8 character + for values whose encoding uses 1, 2, 3, or 4 bytes, respectively. The + character's individual bytes are then captured by the appropriate num- ber of groups. @@ -4750,64 +5704,71 @@ SQUARE BRACKETS AND CHARACTER CLASSES closing square bracket. A closing square bracket on its own is not spe- cial by default. However, if the PCRE_JAVASCRIPT_COMPAT option is set, a lone closing square bracket causes a compile-time error. If a closing - square bracket is required as a member of the class, it should be the - first data character in the class (after an initial circumflex, if + square bracket is required as a member of the class, it should be the + first data character in the class (after an initial circumflex, if present) or escaped with a backslash. - A character class matches a single character in the subject. In a UTF - mode, the character may be more than one data unit long. A matched + A character class matches a single character in the subject. In a UTF + mode, the character may be more than one data unit long. A matched character must be in the set of characters defined by the class, unless - the first character in the class definition is a circumflex, in which + the first character in the class definition is a circumflex, in which case the subject character must not be in the set defined by the class. - If a circumflex is actually required as a member of the class, ensure + If a circumflex is actually required as a member of the class, ensure it is not the first character, or escape it with a backslash. - For example, the character class [aeiou] matches any lower case vowel, - while [^aeiou] matches any character that is not a lower case vowel. + For example, the character class [aeiou] matches any lower case vowel, + while [^aeiou] matches any character that is not a lower case vowel. Note that a circumflex is just a convenient notation for specifying the - characters that are in the class by enumerating those that are not. A - class that starts with a circumflex is not an assertion; it still con- - sumes a character from the subject string, and therefore it fails if + characters that are in the class by enumerating those that are not. A + class that starts with a circumflex is not an assertion; it still con- + sumes a character from the subject string, and therefore it fails if the current pointer is at the end of the string. - In UTF-8 (UTF-16) mode, characters with values greater than 255 - (0xffff) can be included in a class as a literal string of data units, + In UTF-8 (UTF-16, UTF-32) mode, characters with values greater than 255 + (0xffff) can be included in a class as a literal string of data units, or by using the \x{ escaping mechanism. - When caseless matching is set, any letters in a class represent both - their upper case and lower case versions, so for example, a caseless - [aeiou] matches "A" as well as "a", and a caseless [^aeiou] does not - match "A", whereas a caseful version would. In a UTF mode, PCRE always - understands the concept of case for characters whose values are less - than 128, so caseless matching is always possible. For characters with - higher values, the concept of case is supported if PCRE is compiled - with Unicode property support, but not otherwise. If you want to use - caseless matching in a UTF mode for characters 128 and above, you must - ensure that PCRE is compiled with Unicode property support as well as + When caseless matching is set, any letters in a class represent both + their upper case and lower case versions, so for example, a caseless + [aeiou] matches "A" as well as "a", and a caseless [^aeiou] does not + match "A", whereas a caseful version would. In a UTF mode, PCRE always + understands the concept of case for characters whose values are less + than 128, so caseless matching is always possible. For characters with + higher values, the concept of case is supported if PCRE is compiled + with Unicode property support, but not otherwise. If you want to use + caseless matching in a UTF mode for characters 128 and above, you must + ensure that PCRE is compiled with Unicode property support as well as with UTF support. - Characters that might indicate line breaks are never treated in any - special way when matching character classes, whatever line-ending - sequence is in use, and whatever setting of the PCRE_DOTALL and + Characters that might indicate line breaks are never treated in any + special way when matching character classes, whatever line-ending + sequence is in use, and whatever setting of the PCRE_DOTALL and PCRE_MULTILINE options is used. A class such as [^a] always matches one of these characters. - The minus (hyphen) character can be used to specify a range of charac- - ters in a character class. For example, [d-m] matches any letter - between d and m, inclusive. If a minus character is required in a - class, it must be escaped with a backslash or appear in a position - where it cannot be interpreted as indicating a range, typically as the - first or last character in the class. + The minus (hyphen) character can be used to specify a range of charac- + ters in a character class. For example, [d-m] matches any letter + between d and m, inclusive. If a minus character is required in a + class, it must be escaped with a backslash or appear in a position + where it cannot be interpreted as indicating a range, typically as the + first or last character in the class, or immediately after a range. For + example, [b-d-z] matches letters in the range b to d, a hyphen charac- + ter, or z. It is not possible to have the literal character "]" as the end charac- - ter of a range. A pattern such as [W-]46] is interpreted as a class of - two characters ("W" and "-") followed by a literal string "46]", so it - would match "W46]" or "-46]". However, if the "]" is escaped with a - backslash it is interpreted as the end of range, so [W-\]46] is inter- - preted as a class containing a range followed by two other characters. - The octal or hexadecimal representation of "]" can also be used to end + ter of a range. A pattern such as [W-]46] is interpreted as a class of + two characters ("W" and "-") followed by a literal string "46]", so it + would match "W46]" or "-46]". However, if the "]" is escaped with a + backslash it is interpreted as the end of range, so [W-\]46] is inter- + preted as a class containing a range followed by two other characters. + The octal or hexadecimal representation of "]" can also be used to end a range. + An error is generated if a POSIX character class (see below) or an + escape sequence other than one that defines a single character appears + at a point where a range ending character is expected. For example, + [z-\xff] is valid, but [A-\d] and [A-[:digit:]] are not. + Ranges operate in the collating sequence of character values. They can also be used for characters specified numerically, for example [\000-\037]. Ranges can include any characters that are valid for the @@ -4844,15 +5805,16 @@ SQUARE BRACKETS AND CHARACTER CLASSES The only metacharacters that are recognized in character classes are backslash, hyphen (only where it can be interpreted as specifying a range), circumflex (only at the start), opening square bracket (only - when it can be interpreted as introducing a POSIX class name - see the - next section), and the terminating closing square bracket. However, - escaping other non-alphanumeric characters does no harm. + when it can be interpreted as introducing a POSIX class name, or for a + special compatibility feature - see the next two sections), and the + terminating closing square bracket. However, escaping other non- + alphanumeric characters does no harm. POSIX CHARACTER CLASSES Perl supports the POSIX notation for character classes. This uses names - enclosed by [: and :] within the enclosing square brackets. PCRE also + enclosed by [: and :] within the enclosing square brackets. PCRE also supports this notation. For example, [01[:alpha:]%] @@ -4870,15 +5832,18 @@ POSIX CHARACTER CLASSES lower lower case letters print printing characters, including space punct printing characters, excluding letters and digits and space - space white space (not quite the same as \s) + space white space (the same as \s from PCRE 8.34) upper upper case letters word "word" characters (same as \w) xdigit hexadecimal digits - The "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13), - and space (32). Notice that this list includes the VT character (code - 11). This makes "space" different to \s, which does not include VT (for - Perl compatibility). + The default "space" characters are HT (9), LF (10), VT (11), FF (12), + CR (13), and space (32). If locale-specific matching is taking place, + the list of space characters may be different; there may be fewer or + more of them. "Space" used to be different to \s, which did not include + VT, for Perl compatibility. However, Perl changed at release 5.18, and + PCRE followed at release 8.34. "Space" and \s now match the same set + of characters. The name "word" is a Perl extension, and "blank" is a GNU extension from Perl 5.8. Another Perl extension is negation, which is indicated @@ -4890,11 +5855,11 @@ POSIX CHARACTER CLASSES POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not supported, and an error is given if they are encountered. - By default, in UTF modes, characters with values greater than 128 do - not match any of the POSIX character classes. However, if the PCRE_UCP - option is passed to pcre_compile(), some of the classes are changed so - that Unicode character properties are used. This is achieved by replac- - ing the POSIX classes by other sequences, as follows: + By default, characters with values greater than 128 do not match any of + the POSIX character classes. However, if the PCRE_UCP option is passed + to pcre_compile(), some of the classes are changed so that Unicode + character properties are used. This is achieved by replacing certain + POSIX classes by other sequences, as follows: [:alnum:] becomes \p{Xan} [:alpha:] becomes \p{L} @@ -4905,11 +5870,50 @@ POSIX CHARACTER CLASSES [:upper:] becomes \p{Lu} [:word:] becomes \p{Xwd} - Negated versions, such as [:^alpha:] use \P instead of \p. The other - POSIX classes are unchanged, and match only characters with code points - less than 128. + Negated versions, such as [:^alpha:] use \P instead of \p. Three other + POSIX classes are handled specially in UCP mode: + [:graph:] This matches characters that have glyphs that mark the page + when printed. In Unicode property terms, it matches all char- + acters with the L, M, N, P, S, or Cf properties, except for: + U+061C Arabic Letter Mark + U+180E Mongolian Vowel Separator + U+2066 - U+2069 Various "isolate"s + + + [:print:] This matches the same characters as [:graph:] plus space + characters that are not controls, that is, characters with + the Zs property. + + [:punct:] This matches all characters that have the Unicode P (punctua- + tion) property, plus those characters whose code points are + less than 128 that have the S (Symbol) property. + + The other POSIX classes are unchanged, and match only characters with + code points less than 128. + + +COMPATIBILITY FEATURE FOR WORD BOUNDARIES + + In the POSIX.2 compliant library that was included in 4.4BSD Unix, the + ugly syntax [[:<:]] and [[:>:]] is used for matching "start of word" + and "end of word". PCRE treats these items as follows: + + [[:<:]] is converted to \b(?=\w) + [[:>:]] is converted to \b(?<=\w) + + Only these exact character sequences are recognized. A sequence such as + [a[:<:]b] provokes error for an unrecognized POSIX class name. This + support is not compatible with Perl. It is provided to help migrations + from other environments, and is best not used in any new patterns. Note + that \b matches at the start and the end of a word (see "Simple asser- + tions" above), and in a Perl-style pattern the preceding or following + character normally shows which is wanted, without the need for the + assertions that are used above in order to give exactly the POSIX be- + haviour. + + VERTICAL BAR Vertical bar characters are used to separate alternative patterns. For @@ -4978,10 +5982,13 @@ INTERNAL OPTION SETTING some cases the pattern can contain special leading sequences such as (*CRLF) to override what the application has set or what has been defaulted. Details are given in the section entitled "Newline - sequences" above. There are also the (*UTF8), (*UTF16), and (*UCP) - leading sequences that can be used to set UTF and Unicode property - modes; they are equivalent to setting the PCRE_UTF8, PCRE_UTF16, and - the PCRE_UCP options, respectively. + sequences" above. There are also the (*UTF8), (*UTF16),(*UTF32), and + (*UCP) leading sequences that can be used to set UTF and Unicode prop- + erty modes; they are equivalent to setting the PCRE_UTF8, PCRE_UTF16, + PCRE_UTF32 and the PCRE_UCP options, respectively. The (*UTF) sequence + is a generic version that can be used with any of the libraries. How- + ever, the application can set the PCRE_NEVER_UTF option, which locks + out the use of the (*UTF) sequences. SUBPATTERNS @@ -4993,18 +6000,18 @@ SUBPATTERNS cat(aract|erpillar|) - matches "cataract", "caterpillar", or "cat". Without the parentheses, + matches "cataract", "caterpillar", or "cat". Without the parentheses, it would match "cataract", "erpillar" or an empty string. - 2. It sets up the subpattern as a capturing subpattern. This means - that, when the whole pattern matches, that portion of the subject + 2. It sets up the subpattern as a capturing subpattern. This means + that, when the whole pattern matches, that portion of the subject string that matched the subpattern is passed back to the caller via the - ovector argument of the matching function. (This applies only to the - traditional matching functions; the DFA matching functions do not sup- + ovector argument of the matching function. (This applies only to the + traditional matching functions; the DFA matching functions do not sup- port capturing.) Opening parentheses are counted from left to right (starting from 1) to - obtain numbers for the capturing subpatterns. For example, if the + obtain numbers for the capturing subpatterns. For example, if the string "the red king" is matched against the pattern the ((red|white) (king|queen)) @@ -5012,12 +6019,12 @@ SUBPATTERNS the captured substrings are "red king", "red", and "king", and are num- bered 1, 2, and 3, respectively. - The fact that plain parentheses fulfil two functions is not always - helpful. There are often times when a grouping subpattern is required - without a capturing requirement. If an opening parenthesis is followed - by a question mark and a colon, the subpattern does not do any captur- - ing, and is not counted when computing the number of any subsequent - capturing subpatterns. For example, if the string "the white queen" is + The fact that plain parentheses fulfil two functions is not always + helpful. There are often times when a grouping subpattern is required + without a capturing requirement. If an opening parenthesis is followed + by a question mark and a colon, the subpattern does not do any captur- + ing, and is not counted when computing the number of any subsequent + capturing subpatterns. For example, if the string "the white queen" is matched against the pattern the ((?:red|white) (king|queen)) @@ -5025,37 +6032,37 @@ SUBPATTERNS the captured substrings are "white queen" and "queen", and are numbered 1 and 2. The maximum number of capturing subpatterns is 65535. - As a convenient shorthand, if any option settings are required at the - start of a non-capturing subpattern, the option letters may appear + As a convenient shorthand, if any option settings are required at the + start of a non-capturing subpattern, the option letters may appear between the "?" and the ":". Thus the two patterns (?i:saturday|sunday) (?:(?i)saturday|sunday) match exactly the same set of strings. Because alternative branches are - tried from left to right, and options are not reset until the end of - the subpattern is reached, an option setting in one branch does affect - subsequent branches, so the above patterns match "SUNDAY" as well as + tried from left to right, and options are not reset until the end of + the subpattern is reached, an option setting in one branch does affect + subsequent branches, so the above patterns match "SUNDAY" as well as "Saturday". DUPLICATE SUBPATTERN NUMBERS Perl 5.10 introduced a feature whereby each alternative in a subpattern - uses the same numbers for its capturing parentheses. Such a subpattern - starts with (?| and is itself a non-capturing subpattern. For example, + uses the same numbers for its capturing parentheses. Such a subpattern + starts with (?| and is itself a non-capturing subpattern. For example, consider this pattern: (?|(Sat)ur|(Sun))day - Because the two alternatives are inside a (?| group, both sets of cap- - turing parentheses are numbered one. Thus, when the pattern matches, - you can look at captured substring number one, whichever alternative - matched. This construct is useful when you want to capture part, but + Because the two alternatives are inside a (?| group, both sets of cap- + turing parentheses are numbered one. Thus, when the pattern matches, + you can look at captured substring number one, whichever alternative + matched. This construct is useful when you want to capture part, but not all, of one of a number of alternatives. Inside a (?| group, paren- - theses are numbered as usual, but the number is reset at the start of - each branch. The numbers of any capturing parentheses that follow the - subpattern start after the highest number used in any branch. The fol- + theses are numbered as usual, but the number is reset at the start of + each branch. The numbers of any capturing parentheses that follow the + subpattern start after the highest number used in any branch. The fol- lowing example is taken from the Perl documentation. The numbers under- neath show in which buffer the captured content will be stored. @@ -5063,58 +6070,58 @@ DUPLICATE SUBPATTERN NUMBERS / ( a ) (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x # 1 2 2 3 2 3 4 - A back reference to a numbered subpattern uses the most recent value - that is set for that number by any subpattern. The following pattern + A back reference to a numbered subpattern uses the most recent value + that is set for that number by any subpattern. The following pattern matches "abcabc" or "defdef": /(?|(abc)|(def))\1/ - In contrast, a subroutine call to a numbered subpattern always refers - to the first one in the pattern with the given number. The following + In contrast, a subroutine call to a numbered subpattern always refers + to the first one in the pattern with the given number. The following pattern matches "abcabc" or "defabc": /(?|(abc)|(def))(?1)/ - If a condition test for a subpattern's having matched refers to a non- - unique number, the test is true if any of the subpatterns of that num- + If a condition test for a subpattern's having matched refers to a non- + unique number, the test is true if any of the subpatterns of that num- ber have matched. - An alternative approach to using this "branch reset" feature is to use + An alternative approach to using this "branch reset" feature is to use duplicate named subpatterns, as described in the next section. NAMED SUBPATTERNS - Identifying capturing parentheses by number is simple, but it can be - very hard to keep track of the numbers in complicated regular expres- - sions. Furthermore, if an expression is modified, the numbers may - change. To help with this difficulty, PCRE supports the naming of sub- + Identifying capturing parentheses by number is simple, but it can be + very hard to keep track of the numbers in complicated regular expres- + sions. Furthermore, if an expression is modified, the numbers may + change. To help with this difficulty, PCRE supports the naming of sub- patterns. This feature was not added to Perl until release 5.10. Python - had the feature earlier, and PCRE introduced it at release 4.0, using - the Python syntax. PCRE now supports both the Perl and the Python syn- - tax. Perl allows identically numbered subpatterns to have different + had the feature earlier, and PCRE introduced it at release 4.0, using + the Python syntax. PCRE now supports both the Perl and the Python syn- + tax. Perl allows identically numbered subpatterns to have different names, but PCRE does not. - In PCRE, a subpattern can be named in one of three ways: (?...) - or (?'name'...) as in Perl, or (?P...) as in Python. References - to capturing parentheses from other parts of the pattern, such as back - references, recursion, and conditions, can be made by name as well as + In PCRE, a subpattern can be named in one of three ways: (?...) + or (?'name'...) as in Perl, or (?P...) as in Python. References + to capturing parentheses from other parts of the pattern, such as back + references, recursion, and conditions, can be made by name as well as by number. - Names consist of up to 32 alphanumeric characters and underscores. - Named capturing parentheses are still allocated numbers as well as - names, exactly as if the names were not present. The PCRE API provides - function calls for extracting the name-to-number translation table from - a compiled pattern. There is also a convenience function for extracting - a captured substring by name. + Names consist of up to 32 alphanumeric characters and underscores, but + must start with a non-digit. Named capturing parentheses are still + allocated numbers as well as names, exactly as if the names were not + present. The PCRE API provides function calls for extracting the name- + to-number translation table from a compiled pattern. There is also a + convenience function for extracting a captured substring by name. - By default, a name must be unique within a pattern, but it is possible + By default, a name must be unique within a pattern, but it is possible to relax this constraint by setting the PCRE_DUPNAMES option at compile - time. (Duplicate names are also always permitted for subpatterns with - the same number, set up as described in the previous section.) Dupli- - cate names can be useful for patterns where only one instance of the - named parentheses can match. Suppose you want to match the name of a - weekday, either as a 3-letter abbreviation or as the full name, and in + time. (Duplicate names are also always permitted for subpatterns with + the same number, set up as described in the previous section.) Dupli- + cate names can be useful for patterns where only one instance of the + named parentheses can match. Suppose you want to match the name of a + weekday, either as a 3-letter abbreviation or as the full name, and in both cases you want to extract the abbreviation. This pattern (ignoring the line breaks) does the job: @@ -5124,33 +6131,43 @@ NAMED SUBPATTERNS (?Thu)(?:rsday)?| (?Sat)(?:urday)? - There are five capturing substrings, but only one is ever set after a + There are five capturing substrings, but only one is ever set after a match. (An alternative way of solving this problem is to use a "branch reset" subpattern, as described in the previous section.) - The convenience function for extracting the data by name returns the - substring for the first (and in this example, the only) subpattern of - that name that matched. This saves searching to find which numbered + The convenience function for extracting the data by name returns the + substring for the first (and in this example, the only) subpattern of + that name that matched. This saves searching to find which numbered subpattern it was. - If you make a back reference to a non-unique named subpattern from - elsewhere in the pattern, the one that corresponds to the first occur- - rence of the name is used. In the absence of duplicate numbers (see the - previous section) this is the one with the lowest number. If you use a - named reference in a condition test (see the section about conditions - below), either to check whether a subpattern has matched, or to check - for recursion, all subpatterns with the same name are tested. If the - condition is true for any one of them, the overall condition is true. - This is the same behaviour as testing by number. For further details of - the interfaces for handling named subpatterns, see the pcreapi documen- - tation. + If you make a back reference to a non-unique named subpattern from + elsewhere in the pattern, the subpatterns to which the name refers are + checked in the order in which they appear in the overall pattern. The + first one that is set is used for the reference. For example, this pat- + tern matches both "foofoo" and "barbar" but not "foobar" or "barfoo": + (?:(?foo)|(?bar))\k + + + If you make a subroutine call to a non-unique named subpattern, the one + that corresponds to the first occurrence of the name is used. In the + absence of duplicate numbers (see the previous section) this is the one + with the lowest number. + + If you use a named reference in a condition test (see the section about + conditions below), either to check whether a subpattern has matched, or + to check for recursion, all subpatterns with the same name are tested. + If the condition is true for any one of them, the overall condition is + true. This is the same behaviour as testing by number. For further + details of the interfaces for handling named subpatterns, see the + pcreapi documentation. + Warning: You cannot use different names to distinguish between two sub- patterns with the same number because PCRE uses only the numbers when matching. For this reason, an error is given at compile time if differ- ent names are given to subpatterns with the same number. However, you - can give the same name to subpatterns with the same number, even when - PCRE_DUPNAMES is not set. + can always give the same name to subpatterns with the same number, even + when PCRE_DUPNAMES is not set. REPETITION @@ -5196,41 +6213,42 @@ REPETITION In UTF modes, quantifiers apply to characters rather than to individual data units. Thus, for example, \x{100}{2} matches two characters, each of which is represented by a two-byte sequence in a UTF-8 string. Simi- - larly, \X{3} matches three Unicode extended sequences, each of which - may be several data units long (and they may be of different lengths). + larly, \X{3} matches three Unicode extended grapheme clusters, each of + which may be several data units long (and they may be of different + lengths). The quantifier {0} is permitted, causing the expression to behave as if the previous item and the quantifier were not present. This may be use- - ful for subpatterns that are referenced as subroutines from elsewhere + ful for subpatterns that are referenced as subroutines from elsewhere in the pattern (but see also the section entitled "Defining subpatterns - for use by reference only" below). Items other than subpatterns that + for use by reference only" below). Items other than subpatterns that have a {0} quantifier are omitted from the compiled pattern. - For convenience, the three most common quantifiers have single-charac- + For convenience, the three most common quantifiers have single-charac- ter abbreviations: * is equivalent to {0,} + is equivalent to {1,} ? is equivalent to {0,1} - It is possible to construct infinite loops by following a subpattern + It is possible to construct infinite loops by following a subpattern that can match no characters with a quantifier that has no upper limit, for example: (a?)* Earlier versions of Perl and PCRE used to give an error at compile time - for such patterns. However, because there are cases where this can be - useful, such patterns are now accepted, but if any repetition of the - subpattern does in fact match no characters, the loop is forcibly bro- + for such patterns. However, because there are cases where this can be + useful, such patterns are now accepted, but if any repetition of the + subpattern does in fact match no characters, the loop is forcibly bro- ken. - By default, the quantifiers are "greedy", that is, they match as much - as possible (up to the maximum number of permitted times), without - causing the rest of the pattern to fail. The classic example of where + By default, the quantifiers are "greedy", that is, they match as much + as possible (up to the maximum number of permitted times), without + causing the rest of the pattern to fail. The classic example of where this gives problems is in trying to match comments in C programs. These - appear between /* and */ and within the comment, individual * and / - characters may appear. An attempt to match C comments by applying the + appear between /* and */ and within the comment, individual * and / + characters may appear. An attempt to match C comments by applying the pattern /\*.*\*/ @@ -5239,19 +6257,19 @@ REPETITION /* first comment */ not comment /* second comment */ - fails, because it matches the entire string owing to the greediness of + fails, because it matches the entire string owing to the greediness of the .* item. - However, if a quantifier is followed by a question mark, it ceases to + However, if a quantifier is followed by a question mark, it ceases to be greedy, and instead matches the minimum number of times possible, so the pattern /\*.*?\*/ - does the right thing with the C comments. The meaning of the various - quantifiers is not otherwise changed, just the preferred number of - matches. Do not confuse this use of question mark with its use as a - quantifier in its own right. Because it has two uses, it can sometimes + does the right thing with the C comments. The meaning of the various + quantifiers is not otherwise changed, just the preferred number of + matches. Do not confuse this use of question mark with its use as a + quantifier in its own right. Because it has two uses, it can sometimes appear doubled, as in \d??\d @@ -5259,38 +6277,47 @@ REPETITION which matches one digit by preference, but can match two if that is the only way the rest of the pattern matches. - If the PCRE_UNGREEDY option is set (an option that is not available in - Perl), the quantifiers are not greedy by default, but individual ones - can be made greedy by following them with a question mark. In other + If the PCRE_UNGREEDY option is set (an option that is not available in + Perl), the quantifiers are not greedy by default, but individual ones + can be made greedy by following them with a question mark. In other words, it inverts the default behaviour. - When a parenthesized subpattern is quantified with a minimum repeat - count that is greater than 1 or with a limited maximum, more memory is - required for the compiled pattern, in proportion to the size of the + When a parenthesized subpattern is quantified with a minimum repeat + count that is greater than 1 or with a limited maximum, more memory is + required for the compiled pattern, in proportion to the size of the minimum or maximum. If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv- - alent to Perl's /s) is set, thus allowing the dot to match newlines, - the pattern is implicitly anchored, because whatever follows will be - tried against every character position in the subject string, so there - is no point in retrying the overall match at any position after the - first. PCRE normally treats such a pattern as though it were preceded + alent to Perl's /s) is set, thus allowing the dot to match newlines, + the pattern is implicitly anchored, because whatever follows will be + tried against every character position in the subject string, so there + is no point in retrying the overall match at any position after the + first. PCRE normally treats such a pattern as though it were preceded by \A. - In cases where it is known that the subject string contains no new- - lines, it is worth setting PCRE_DOTALL in order to obtain this opti- + In cases where it is known that the subject string contains no new- + lines, it is worth setting PCRE_DOTALL in order to obtain this opti- mization, or alternatively using ^ to indicate anchoring explicitly. - However, there is one situation where the optimization cannot be used. + However, there are some cases where the optimization cannot be used. When .* is inside capturing parentheses that are the subject of a back reference elsewhere in the pattern, a match at the start may fail where a later one succeeds. Consider, for example: (.*)abc\1 - If the subject is "xyz123abc123" the match point is the fourth charac- + If the subject is "xyz123abc123" the match point is the fourth charac- ter. For this reason, such a pattern is not implicitly anchored. + Another case where implicit anchoring is not applied is when the lead- + ing .* is inside an atomic group. Once again, a match at the start may + fail where a later one succeeds. Consider this pattern: + + (?>.*?a)b + + It matches "ab" in the subject "aab". The use of the backtracking con- + trol verbs (*PRUNE) and (*SKIP) also disable this optimization. + When a capturing subpattern is repeated, the value captured is the sub- string that matched the final iteration. For example, after @@ -5545,24 +6572,25 @@ ASSERTIONS tion contains capturing subpatterns within it, these are counted for the purposes of numbering the capturing subpatterns in the whole pat- tern. However, substring capturing is carried out only for positive - assertions, because it does not make sense for negative assertions. + assertions. (Perl sometimes, but not always, does do capturing in nega- + tive assertions.) - For compatibility with Perl, assertion subpatterns may be repeated; - though it makes no sense to assert the same thing several times, the - side effect of capturing parentheses may occasionally be useful. In + For compatibility with Perl, assertion subpatterns may be repeated; + though it makes no sense to assert the same thing several times, the + side effect of capturing parentheses may occasionally be useful. In practice, there only three cases: - (1) If the quantifier is {0}, the assertion is never obeyed during - matching. However, it may contain internal capturing parenthesized + (1) If the quantifier is {0}, the assertion is never obeyed during + matching. However, it may contain internal capturing parenthesized groups that are called from elsewhere via the subroutine mechanism. - (2) If quantifier is {0,n} where n is greater than zero, it is treated - as if it were {0,1}. At run time, the rest of the pattern match is + (2) If quantifier is {0,n} where n is greater than zero, it is treated + as if it were {0,1}. At run time, the rest of the pattern match is tried with and without the assertion, the order depending on the greed- iness of the quantifier. - (3) If the minimum repetition is greater than zero, the quantifier is - ignored. The assertion is obeyed just once when encountered during + (3) If the minimum repetition is greater than zero, the quantifier is + ignored. The assertion is obeyed just once when encountered during matching. Lookahead assertions @@ -5572,38 +6600,38 @@ ASSERTIONS \w+(?=;) - matches a word followed by a semicolon, but does not include the semi- + matches a word followed by a semicolon, but does not include the semi- colon in the match, and foo(?!bar) - matches any occurrence of "foo" that is not followed by "bar". Note + matches any occurrence of "foo" that is not followed by "bar". Note that the apparently similar pattern (?!foo)bar - does not find an occurrence of "bar" that is preceded by something - other than "foo"; it finds any occurrence of "bar" whatsoever, because + does not find an occurrence of "bar" that is preceded by something + other than "foo"; it finds any occurrence of "bar" whatsoever, because the assertion (?!foo) is always true when the next three characters are "bar". A lookbehind assertion is needed to achieve the other effect. If you want to force a matching failure at some point in a pattern, the - most convenient way to do it is with (?!) because an empty string - always matches, so an assertion that requires there not to be an empty + most convenient way to do it is with (?!) because an empty string + always matches, so an assertion that requires there not to be an empty string must always fail. The backtracking control verb (*FAIL) or (*F) is a synonym for (?!). Lookbehind assertions - Lookbehind assertions start with (?<= for positive assertions and (?)...) or (?('name')...) to test for a - used subpattern by name. For compatibility with earlier versions of - PCRE, which had this facility before Perl, the syntax (?(name)...) is - also recognized. However, there is a possible ambiguity with this syn- - tax, because subpattern names may consist entirely of digits. PCRE - looks first for a named subpattern; if it cannot find one and the name - consists entirely of digits, PCRE looks for a subpattern of that num- - ber, which must be greater than zero. Using subpattern names that con- - sist entirely of digits is not recommended. + Perl uses the syntax (?()...) or (?('name')...) to test for a + used subpattern by name. For compatibility with earlier versions of + PCRE, which had this facility before Perl, the syntax (?(name)...) is + also recognized. Rewriting the above example to use a named subpattern gives this: @@ -6160,131 +7183,145 @@ CALLOUTS PCRE provides a similar feature, but of course it cannot obey arbitrary Perl code. The feature is called "callout". The caller of PCRE provides an external function by putting its entry point in the global variable - pcre_callout (8-bit library) or pcre16_callout (16-bit library). By - default, this variable contains NULL, which disables all calling out. + pcre_callout (8-bit library) or pcre[16|32]_callout (16-bit or 32-bit + library). By default, this variable contains NULL, which disables all + calling out. - Within a regular expression, (?C) indicates the points at which the - external function is to be called. If you want to identify different - callout points, you can put a number less than 256 after the letter C. - The default value is zero. For example, this pattern has two callout + Within a regular expression, (?C) indicates the points at which the + external function is to be called. If you want to identify different + callout points, you can put a number less than 256 after the letter C. + The default value is zero. For example, this pattern has two callout points: (?C1)abc(?C2)def - If the PCRE_AUTO_CALLOUT flag is passed to a compiling function, call- - outs are automatically installed before each item in the pattern. They - are all numbered 255. + If the PCRE_AUTO_CALLOUT flag is passed to a compiling function, call- + outs are automatically installed before each item in the pattern. They + are all numbered 255. If there is a conditional group in the pattern + whose condition is an assertion, an additional callout is inserted just + before the condition. An explicit callout may also be set at this posi- + tion, as in this example: - During matching, when PCRE reaches a callout point, the external func- - tion is called. It is provided with the number of the callout, the - position in the pattern, and, optionally, one item of data originally - supplied by the caller of the matching function. The callout function - may cause matching to proceed, to backtrack, or to fail altogether. A - complete description of the interface to the callout function is given - in the pcrecallout documentation. + (?(?C9)(?=a)abc|def) + Note that this applies only to assertion conditions, not to other types + of condition. -BACKTRACKING CONTROL + During matching, when PCRE reaches a callout point, the external func- + tion is called. It is provided with the number of the callout, the + position in the pattern, and, optionally, one item of data originally + supplied by the caller of the matching function. The callout function + may cause matching to proceed, to backtrack, or to fail altogether. - Perl 5.10 introduced a number of "Special Backtracking Control Verbs", - which are described in the Perl documentation as "experimental and sub- - ject to change or removal in a future version of Perl". It goes on to - say: "Their usage in production code should be noted to avoid problems - during upgrades." The same remarks apply to the PCRE features described - in this section. + By default, PCRE implements a number of optimizations at compile time + and matching time, and one side-effect is that sometimes callouts are + skipped. If you need all possible callouts to happen, you need to set + options that disable the relevant optimizations. More details, and a + complete description of the interface to the callout function, are + given in the pcrecallout documentation. - Since these verbs are specifically related to backtracking, most of - them can be used only when the pattern is to be matched using one of - the traditional matching functions, which use a backtracking algorithm. - With the exception of (*FAIL), which behaves like a failing negative - assertion, they cause an error if encountered by a DFA matching func- - tion. - If any of these verbs are used in an assertion or in a subpattern that - is called as a subroutine (whether or not recursively), their effect is - confined to that subpattern; it does not extend to the surrounding pat- - tern, with one exception: the name from a *(MARK), (*PRUNE), or (*THEN) - that is encountered in a successful positive assertion is passed back - when a match succeeds (compare capturing parentheses in assertions). - Note that such subpatterns are processed as anchored at the point where - they are tested. Note also that Perl's treatment of subroutines and - assertions is different in some cases. +BACKTRACKING CONTROL - The new verbs make use of what was previously invalid syntax: an open- + Perl 5.10 introduced a number of "Special Backtracking Control Verbs", + which are still described in the Perl documentation as "experimental + and subject to change or removal in a future version of Perl". It goes + on to say: "Their usage in production code should be noted to avoid + problems during upgrades." The same remarks apply to the PCRE features + described in this section. + + The new verbs make use of what was previously invalid syntax: an open- ing parenthesis followed by an asterisk. They are generally of the form - (*VERB) or (*VERB:NAME). Some may take either form, with differing be- - haviour, depending on whether or not an argument is present. A name is + (*VERB) or (*VERB:NAME). Some may take either form, possibly behaving + differently depending on whether or not a name is present. A name is any sequence of characters that does not include a closing parenthesis. The maximum length of name is 255 in the 8-bit library and 65535 in the - 16-bit library. If the name is empty, that is, if the closing parenthe- - sis immediately follows the colon, the effect is as if the colon were - not there. Any number of these verbs may occur in a pattern. + 16-bit and 32-bit libraries. If the name is empty, that is, if the + closing parenthesis immediately follows the colon, the effect is as if + the colon were not there. Any number of these verbs may occur in a + pattern. + Since these verbs are specifically related to backtracking, most of + them can be used only when the pattern is to be matched using one of + the traditional matching functions, because these use a backtracking + algorithm. With the exception of (*FAIL), which behaves like a failing + negative assertion, the backtracking control verbs cause an error if + encountered by a DFA matching function. + + The behaviour of these verbs in repeated groups, assertions, and in + subpatterns called as subroutines (whether or not recursively) is docu- + mented below. + Optimizations that affect backtracking verbs - PCRE contains some optimizations that are used to speed up matching by + PCRE contains some optimizations that are used to speed up matching by running some checks at the start of each match attempt. For example, it - may know the minimum length of matching subject, or that a particular - character must be present. When one of these optimizations suppresses - the running of a match, any included backtracking verbs will not, of + may know the minimum length of matching subject, or that a particular + character must be present. When one of these optimizations bypasses the + running of a match, any included backtracking verbs will not, of course, be processed. You can suppress the start-of-match optimizations - by setting the PCRE_NO_START_OPTIMIZE option when calling pcre_com- + by setting the PCRE_NO_START_OPTIMIZE option when calling pcre_com- pile() or pcre_exec(), or by starting the pattern with (*NO_START_OPT). There is more discussion of this option in the section entitled "Option bits for pcre_exec()" in the pcreapi documentation. - Experiments with Perl suggest that it too has similar optimizations, + Experiments with Perl suggest that it too has similar optimizations, sometimes leading to anomalous results. Verbs that act immediately - The following verbs act as soon as they are encountered. They may not + The following verbs act as soon as they are encountered. They may not be followed by a name. (*ACCEPT) - This verb causes the match to end successfully, skipping the remainder - of the pattern. However, when it is inside a subpattern that is called - as a subroutine, only that subpattern is ended successfully. Matching - then continues at the outer level. If (*ACCEPT) is inside capturing - parentheses, the data so far is captured. For example: + This verb causes the match to end successfully, skipping the remainder + of the pattern. However, when it is inside a subpattern that is called + as a subroutine, only that subpattern is ended successfully. Matching + then continues at the outer level. If (*ACCEPT) in triggered in a posi- + tive assertion, the assertion succeeds; in a negative assertion, the + assertion fails. + If (*ACCEPT) is inside capturing parentheses, the data so far is cap- + tured. For example: + A((?:A|B(*ACCEPT)|C)D) - This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap- + This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap- tured by the outer parentheses. (*FAIL) or (*F) - This verb causes a matching failure, forcing backtracking to occur. It - is equivalent to (?!) but easier to read. The Perl documentation notes - that it is probably useful only when combined with (?{}) or (??{}). - Those are, of course, Perl features that are not present in PCRE. The - nearest equivalent is the callout feature, as for example in this pat- + This verb causes a matching failure, forcing backtracking to occur. It + is equivalent to (?!) but easier to read. The Perl documentation notes + that it is probably useful only when combined with (?{}) or (??{}). + Those are, of course, Perl features that are not present in PCRE. The + nearest equivalent is the callout feature, as for example in this pat- tern: a+(?C)(*FAIL) - A match with the string "aaaa" always fails, but the callout is taken + A match with the string "aaaa" always fails, but the callout is taken before each backtrack happens (in this example, 10 times). Recording which path was taken - There is one verb whose main purpose is to track how a match was - arrived at, though it also has a secondary use in conjunction with + There is one verb whose main purpose is to track how a match was + arrived at, though it also has a secondary use in conjunction with advancing the match starting point (see (*SKIP) below). (*MARK:NAME) or (*:NAME) - A name is always required with this verb. There may be as many - instances of (*MARK) as you like in a pattern, and their names do not + A name is always required with this verb. There may be as many + instances of (*MARK) as you like in a pattern, and their names do not have to be unique. - When a match succeeds, the name of the last-encountered (*MARK) on the - matching path is passed back to the caller as described in the section - entitled "Extra data for pcre_exec()" in the pcreapi documentation. - Here is an example of pcretest output, where the /K modifier requests - the retrieval and outputting of (*MARK) data: + When a match succeeds, the name of the last-encountered (*MARK:NAME), + (*PRUNE:NAME), or (*THEN:NAME) on the matching path is passed back to + the caller as described in the section entitled "Extra data for + pcre_exec()" in the pcreapi documentation. Here is an example of + pcretest output, where the /K modifier requests the retrieval and out- + putting of (*MARK) data: re> /X(*MARK:A)Y|X(*MARK:B)Z/K data> XY @@ -6299,57 +7336,67 @@ BACKTRACKING CONTROL efficient way of obtaining this information than putting each alterna- tive in its own capturing parentheses. - If (*MARK) is encountered in a positive assertion, its name is recorded - and passed back if it is the last-encountered. This does not happen for - negative assertions. + If a verb with a name is encountered in a positive assertion that is + true, the name is recorded and passed back if it is the last-encoun- + tered. This does not happen for negative assertions or failing positive + assertions. - After a partial match or a failed match, the name of the last encoun- - tered (*MARK) in the entire match process is returned. For example: + After a partial match or a failed match, the last encountered name in + the entire match process is returned. For example: re> /X(*MARK:A)Y|X(*MARK:B)Z/K data> XP No match, mark = B - Note that in this unanchored example the mark is retained from the + Note that in this unanchored example the mark is retained from the match attempt that started at the letter "X" in the subject. Subsequent match attempts starting at "P" and then with an empty string do not get as far as the (*MARK) item, but nevertheless do not reset it. - If you are interested in (*MARK) values after failed matches, you - should probably set the PCRE_NO_START_OPTIMIZE option (see above) to + If you are interested in (*MARK) values after failed matches, you + should probably set the PCRE_NO_START_OPTIMIZE option (see above) to ensure that the match is always attempted. Verbs that act after backtracking The following verbs do nothing when they are encountered. Matching con- - tinues with what follows, but if there is no subsequent match, causing - a backtrack to the verb, a failure is forced. That is, backtracking - cannot pass to the left of the verb. However, when one of these verbs - appears inside an atomic group, its effect is confined to that group, - because once the group has been matched, there is never any backtrack- - ing into it. In this situation, backtracking can "jump back" to the - left of the entire atomic group. (Remember also, as stated above, that - this localization also applies in subroutine calls and assertions.) + tinues with what follows, but if there is no subsequent match, causing + a backtrack to the verb, a failure is forced. That is, backtracking + cannot pass to the left of the verb. However, when one of these verbs + appears inside an atomic group or an assertion that is true, its effect + is confined to that group, because once the group has been matched, + there is never any backtracking into it. In this situation, backtrack- + ing can "jump back" to the left of the entire atomic group or asser- + tion. (Remember also, as stated above, that this localization also + applies in subroutine calls.) These verbs differ in exactly what kind of failure occurs when back- - tracking reaches them. + tracking reaches them. The behaviour described below is what happens + when the verb is not in a subroutine or an assertion. Subsequent sec- + tions cover these special cases. (*COMMIT) This verb, which may not be followed by a name, causes the whole match - to fail outright if the rest of the pattern does not match. Even if the - pattern is unanchored, no further attempts to find a match by advancing - the starting point take place. Once (*COMMIT) has been passed, - pcre_exec() is committed to finding a match at the current starting - point, or not at all. For example: + to fail outright if there is a later matching failure that causes back- + tracking to reach it. Even if the pattern is unanchored, no further + attempts to find a match by advancing the starting point take place. If + (*COMMIT) is the only backtracking verb that is encountered, once it + has been passed pcre_exec() is committed to finding a match at the cur- + rent starting point, or not at all. For example: a+(*COMMIT)b - This matches "xxaab" but not "aacaab". It can be thought of as a kind + This matches "xxaab" but not "aacaab". It can be thought of as a kind of dynamic anchor, or "I've started, so I must finish." The name of the - most recently passed (*MARK) in the path is passed back when (*COMMIT) + most recently passed (*MARK) in the path is passed back when (*COMMIT) forces a match failure. + If there is more than one backtracking verb in a pattern, a different + one that follows (*COMMIT) may be triggered first, so merely passing + (*COMMIT) during a match does not always guarantee that a match must be + at this starting point. + Note that (*COMMIT) at the start of a pattern is not the same as an anchor, unless PCRE's start-of-match optimizations are turned off, as shown in this pcretest example: @@ -6369,67 +7416,81 @@ BACKTRACKING CONTROL (*PRUNE) or (*PRUNE:NAME) This verb causes the match to fail at the current starting position in - the subject if the rest of the pattern does not match. If the pattern - is unanchored, the normal "bumpalong" advance to the next starting - character then happens. Backtracking can occur as usual to the left of - (*PRUNE), before it is reached, or when matching to the right of - (*PRUNE), but if there is no match to the right, backtracking cannot - cross (*PRUNE). In simple cases, the use of (*PRUNE) is just an alter- - native to an atomic group or possessive quantifier, but there are some - uses of (*PRUNE) that cannot be expressed in any other way. The behav- - iour of (*PRUNE:NAME) is the same as (*MARK:NAME)(*PRUNE). In an - anchored pattern (*PRUNE) has the same effect as (*COMMIT). + the subject if there is a later matching failure that causes backtrack- + ing to reach it. If the pattern is unanchored, the normal "bumpalong" + advance to the next starting character then happens. Backtracking can + occur as usual to the left of (*PRUNE), before it is reached, or when + matching to the right of (*PRUNE), but if there is no match to the + right, backtracking cannot cross (*PRUNE). In simple cases, the use of + (*PRUNE) is just an alternative to an atomic group or possessive quan- + tifier, but there are some uses of (*PRUNE) that cannot be expressed in + any other way. In an anchored pattern (*PRUNE) has the same effect as + (*COMMIT). + The behaviour of (*PRUNE:NAME) is the not the same as + (*MARK:NAME)(*PRUNE). It is like (*MARK:NAME) in that the name is + remembered for passing back to the caller. However, (*SKIP:NAME) + searches only for names set with (*MARK). + (*SKIP) - This verb, when given without a name, is like (*PRUNE), except that if - the pattern is unanchored, the "bumpalong" advance is not to the next + This verb, when given without a name, is like (*PRUNE), except that if + the pattern is unanchored, the "bumpalong" advance is not to the next character, but to the position in the subject where (*SKIP) was encoun- - tered. (*SKIP) signifies that whatever text was matched leading up to + tered. (*SKIP) signifies that whatever text was matched leading up to it cannot be part of a successful match. Consider: a+(*SKIP)b - If the subject is "aaaac...", after the first match attempt fails - (starting at the first character in the string), the starting point + If the subject is "aaaac...", after the first match attempt fails + (starting at the first character in the string), the starting point skips on to start the next attempt at "c". Note that a possessive quan- - tifer does not have the same effect as this example; although it would - suppress backtracking during the first match attempt, the second - attempt would start at the second character instead of skipping on to + tifer does not have the same effect as this example; although it would + suppress backtracking during the first match attempt, the second + attempt would start at the second character instead of skipping on to "c". (*SKIP:NAME) - When (*SKIP) has an associated name, its behaviour is modified. If the - following pattern fails to match, the previous path through the pattern - is searched for the most recent (*MARK) that has the same name. If one - is found, the "bumpalong" advance is to the subject position that cor- - responds to that (*MARK) instead of to where (*SKIP) was encountered. - If no (*MARK) with a matching name is found, the (*SKIP) is ignored. + When (*SKIP) has an associated name, its behaviour is modified. When it + is triggered, the previous path through the pattern is searched for the + most recent (*MARK) that has the same name. If one is found, the + "bumpalong" advance is to the subject position that corresponds to that + (*MARK) instead of to where (*SKIP) was encountered. If no (*MARK) with + a matching name is found, the (*SKIP) is ignored. + Note that (*SKIP:NAME) searches only for names set by (*MARK:NAME). It + ignores names that are set by (*PRUNE:NAME) or (*THEN:NAME). + (*THEN) or (*THEN:NAME) - This verb causes a skip to the next innermost alternative if the rest - of the pattern does not match. That is, it cancels pending backtrack- - ing, but only within the current alternative. Its name comes from the - observation that it can be used for a pattern-based if-then-else block: + This verb causes a skip to the next innermost alternative when back- + tracking reaches it. That is, it cancels any further backtracking + within the current alternative. Its name comes from the observation + that it can be used for a pattern-based if-then-else block: ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ... If the COND1 pattern matches, FOO is tried (and possibly further items after the end of the group if FOO succeeds); on failure, the matcher skips to the second alternative and tries COND2, without backtracking - into COND1. The behaviour of (*THEN:NAME) is exactly the same as - (*MARK:NAME)(*THEN). If (*THEN) is not inside an alternation, it acts - like (*PRUNE). + into COND1. If that succeeds and BAR fails, COND3 is tried. If subse- + quently BAZ fails, there are no more alternatives, so there is a back- + track to whatever came before the entire group. If (*THEN) is not + inside an alternation, it acts like (*PRUNE). - Note that a subpattern that does not contain a | character is just a - part of the enclosing alternative; it is not a nested alternation with - only one alternative. The effect of (*THEN) extends beyond such a sub- - pattern to the enclosing alternative. Consider this pattern, where A, - B, etc. are complex pattern fragments that do not contain any | charac- - ters at this level: + The behaviour of (*THEN:NAME) is the not the same as + (*MARK:NAME)(*THEN). It is like (*MARK:NAME) in that the name is + remembered for passing back to the caller. However, (*SKIP:NAME) + searches only for names set with (*MARK). + A subpattern that does not contain a | character is just a part of the + enclosing alternative; it is not a nested alternation with only one + alternative. The effect of (*THEN) extends beyond such a subpattern to + the enclosing alternative. Consider this pattern, where A, B, etc. are + complex pattern fragments that do not contain any | characters at this + level: + A (B(*THEN)C) | D If A and B are matched, but there is a failure in C, matching does not @@ -6444,7 +7505,7 @@ BACKTRACKING CONTROL tern to fail because there are no more alternatives to try. In this case, matching does now backtrack into A. - Note also that a conditional subpattern is not considered as having two + Note that a conditional subpattern is not considered as having two alternatives, because only one is ever used. In other words, the | character in a conditional subpattern has a different meaning. Ignoring white space, consider: @@ -6468,22 +7529,84 @@ BACKTRACKING CONTROL the advance may be more than one character. (*COMMIT) is the strongest, causing the entire match to fail. - If more than one such verb is present in a pattern, the "strongest" one - wins. For example, consider this pattern, where A, B, etc. are complex - pattern fragments: + More than one backtracking verb - (A(*COMMIT)B(*THEN)C|D) + If more than one backtracking verb is present in a pattern, the one + that is backtracked onto first acts. For example, consider this pat- + tern, where A, B, etc. are complex pattern fragments: - Once A has matched, PCRE is committed to this match, at the current - starting position. If subsequently B matches, but C does not, the nor- - mal (*THEN) action of trying the next alternative (that is, D) does not - happen because (*COMMIT) overrides. + (A(*COMMIT)B(*THEN)C|ABD) + If A matches but B fails, the backtrack to (*COMMIT) causes the entire + match to fail. However, if A and B match, but C fails, the backtrack to + (*THEN) causes the next alternative (ABD) to be tried. This behaviour + is consistent, but is not always the same as Perl's. It means that if + two or more backtracking verbs appear in succession, all the the last + of them has no effect. Consider this example: + ...(*COMMIT)(*PRUNE)... + + If there is a matching failure to the right, backtracking onto (*PRUNE) + causes it to be triggered, and its action is taken. There can never be + a backtrack onto (*COMMIT). + + Backtracking verbs in repeated groups + + PCRE differs from Perl in its handling of backtracking verbs in + repeated groups. For example, consider: + + /(a(*COMMIT)b)+ac/ + + If the subject is "abac", Perl matches, but PCRE fails because the + (*COMMIT) in the second repeat of the group acts. + + Backtracking verbs in assertions + + (*FAIL) in an assertion has its normal effect: it forces an immediate + backtrack. + + (*ACCEPT) in a positive assertion causes the assertion to succeed with- + out any further processing. In a negative assertion, (*ACCEPT) causes + the assertion to fail without any further processing. + + The other backtracking verbs are not treated specially if they appear + in a positive assertion. In particular, (*THEN) skips to the next + alternative in the innermost enclosing group that has alternations, + whether or not this is within the assertion. + + Negative assertions are, however, different, in order to ensure that + changing a positive assertion into a negative assertion changes its + result. Backtracking into (*COMMIT), (*SKIP), or (*PRUNE) causes a neg- + ative assertion to be true, without considering any further alternative + branches in the assertion. Backtracking into (*THEN) causes it to skip + to the next enclosing alternative within the assertion (the normal be- + haviour), but if the assertion does not have such an alternative, + (*THEN) behaves like (*PRUNE). + + Backtracking verbs in subroutines + + These behaviours occur whether or not the subpattern is called recur- + sively. Perl's treatment of subroutines is different in some cases. + + (*FAIL) in a subpattern called as a subroutine has its normal effect: + it forces an immediate backtrack. + + (*ACCEPT) in a subpattern called as a subroutine causes the subroutine + match to succeed without any further processing. Matching then contin- + ues after the subroutine call. + + (*COMMIT), (*SKIP), and (*PRUNE) in a subpattern called as a subroutine + cause the subroutine match to fail. + + (*THEN) skips to the next alternative in the innermost enclosing group + within the subpattern that has alternatives. If there is no such group + within the subpattern, (*THEN) causes the subroutine match to fail. + + SEE ALSO pcreapi(3), pcrecallout(3), pcrematching(3), pcresyntax(3), pcre(3), - pcre16(3). + pcre16(3), pcre32(3). AUTHOR @@ -6495,18 +7618,18 @@ AUTHOR REVISION - Last updated: 17 June 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 03 December 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCRESYNTAX(3) PCRESYNTAX(3) +PCRESYNTAX(3) Library Functions Manual PCRESYNTAX(3) + NAME PCRE - Perl-compatible regular expressions - PCRE REGULAR EXPRESSION SYNTAX SUMMARY The full syntax and semantics of the regular expressions that are sup- @@ -6529,11 +7652,16 @@ CHARACTERS \n newline (hex 0A) \r carriage return (hex 0D) \t tab (hex 09) + \0dd character with octal code 0dd \ddd character with octal code ddd, or backreference + \o{ddd..} character with octal code ddd.. \xhh character with hex code hh \x{hhh..} character with hex code hhh.. + Note that \0dd is always an octal code, and that \8 and \9 are the lit- + eral characters "8" and "9". + CHARACTER TYPES . any character except newline; @@ -6553,11 +7681,14 @@ CHARACTER TYPES \V a character that is not a vertical white space character \w a "word" character \W a "non-word" character - \X an extended Unicode sequence + \X a Unicode extended grapheme cluster - In PCRE, by default, \d, \D, \s, \S, \w, and \W recognize only ASCII - characters, even in a UTF mode. However, this can be changed by setting - the PCRE_UCP option. + By default, \d, \s, and \w match only ASCII characters, even in UTF-8 + mode or in the 16- bit and 32-bit libraries. However, if locale-spe- + cific matching is happening, \s and \w may also match characters with + code points in the range 128-255. If the PCRE_UCP option is set, the + behaviour of these escape sequences is changed to use Unicode proper- + ties and they match many more characters. GENERAL CATEGORY PROPERTIES FOR \p and \P @@ -6612,27 +7743,32 @@ PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P Xan Alphanumeric: union of properties L and N Xps POSIX space: property Z or tab, NL, VT, FF, CR - Xsp Perl space: property Z or tab, NL, FF, CR + Xsp Perl space: property Z or tab, NL, VT, FF, CR + Xuc Univerally-named character: one that can be + represented by a Universal Character Name Xwd Perl word: property Xan or underscore + Perl and POSIX space are now the same. Perl added VT to its space char- + acter set at release 5.18 and PCRE changed at release 8.34. + SCRIPT NAMES FOR \p AND \P - Arabic, Armenian, Avestan, Balinese, Bamum, Batak, Bengali, Bopomofo, - Brahmi, Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Chakma, - Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot, Cyrillic, Deseret, - Devanagari, Egyptian_Hieroglyphs, Ethiopic, Georgian, Glagolitic, - Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira- - gana, Imperial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscrip- - tional_Parthian, Javanese, Kaithi, Kannada, Katakana, Kayah_Li, - Kharoshthi, Khmer, Lao, Latin, Lepcha, Limbu, Linear_B, Lisu, Lycian, + Arabic, Armenian, Avestan, Balinese, Bamum, Batak, Bengali, Bopomofo, + Brahmi, Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Chakma, + Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot, Cyrillic, Deseret, + Devanagari, Egyptian_Hieroglyphs, Ethiopic, Georgian, Glagolitic, + Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira- + gana, Imperial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscrip- + tional_Parthian, Javanese, Kaithi, Kannada, Katakana, Kayah_Li, + Kharoshthi, Khmer, Lao, Latin, Lepcha, Limbu, Linear_B, Lisu, Lycian, Lydian, Malayalam, Mandaic, Meetei_Mayek, Meroitic_Cursive, - Meroitic_Hieroglyphs, Miao, Mongolian, Myanmar, New_Tai_Lue, Nko, - Ogham, Old_Italic, Old_Persian, Old_South_Arabian, Old_Turkic, - Ol_Chiki, Oriya, Osmanya, Phags_Pa, Phoenician, Rejang, Runic, Samari- - tan, Saurashtra, Sharada, Shavian, Sinhala, Sora_Sompeng, Sundanese, - Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tai_Tham, Tai_Viet, - Takri, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Vai, + Meroitic_Hieroglyphs, Miao, Mongolian, Myanmar, New_Tai_Lue, Nko, + Ogham, Old_Italic, Old_Persian, Old_South_Arabian, Old_Turkic, + Ol_Chiki, Oriya, Osmanya, Phags_Pa, Phoenician, Rejang, Runic, Samari- + tan, Saurashtra, Sharada, Shavian, Sinhala, Sora_Sompeng, Sundanese, + Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tai_Tham, Tai_Viet, + Takri, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Vai, Yi. @@ -6659,8 +7795,8 @@ CHARACTER CLASSES word same as \w xdigit hexadecimal digit - In PCRE, POSIX character set names recognize only ASCII characters by - default, but some of them use Unicode properties if PCRE_UCP is set. + In PCRE, POSIX character set names recognize only ASCII characters by + default, but some of them use Unicode properties if PCRE_UCP is set. You can use \Q...\E inside a character class. @@ -6741,15 +7877,22 @@ OPTION SETTING (?x) extended (ignore white space) (?-...) unset option(s) - The following are recognized only at the start of a pattern or after + The following are recognized only at the start of a pattern or after one of the newline-setting options with similar syntax: + (*LIMIT_MATCH=d) set the match limit to d (decimal number) + (*LIMIT_RECURSION=d) set the recursion limit to d (decimal number) (*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE) (*UTF8) set UTF-8 mode: 8-bit library (PCRE_UTF8) (*UTF16) set UTF-16 mode: 16-bit library (PCRE_UTF16) + (*UTF32) set UTF-32 mode: 32-bit library (PCRE_UTF32) + (*UTF) set appropriate UTF mode for the library in use (*UCP) set PCRE_UCP (use Unicode properties for \d etc) + Note that LIMIT_MATCH and LIMIT_RECURSION can only reduce the value of + the limits set by the caller of pcre_exec(), not increase them. + LOOKAHEAD AND LOOKBEHIND ASSERTIONS (?=...) positive look ahead @@ -6835,7 +7978,7 @@ BACKTRACKING CONTROL NEWLINE CONVENTIONS These are recognized only at the very start of the pattern or after a - (*BSR_...), (*UTF8), (*UTF16) or (*UCP) option. + (*BSR_...), (*UTF8), (*UTF16), (*UTF32) or (*UCP) option. (*CR) carriage return only (*LF) linefeed only @@ -6873,165 +8016,185 @@ AUTHOR REVISION - Last updated: 10 January 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 12 November 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCREUNICODE(3) PCREUNICODE(3) +PCREUNICODE(3) Library Functions Manual PCREUNICODE(3) + NAME PCRE - Perl-compatible regular expressions +UTF-8, UTF-16, UTF-32, AND UNICODE PROPERTY SUPPORT -UTF-8, UTF-16, AND UNICODE PROPERTY SUPPORT + As well as UTF-8 support, PCRE also supports UTF-16 (from release 8.30) + and UTF-32 (from release 8.32), by means of two additional libraries. + They can be built as well as, or instead of, the 8-bit library. - From Release 8.30, in addition to its previous UTF-8 support, PCRE also - supports UTF-16 by means of a separate 16-bit library. This can be - built as well as, or instead of, the 8-bit library. - UTF-8 SUPPORT In order process UTF-8 strings, you must build PCRE's 8-bit library with UTF support, and, in addition, you must call pcre_compile() with the PCRE_UTF8 option flag, or the pattern must start with the sequence - (*UTF8). When either of these is the case, both the pattern and any - subject strings that are matched against it are treated as UTF-8 - strings instead of strings of 1-byte characters. + (*UTF8) or (*UTF). When either of these is the case, both the pattern + and any subject strings that are matched against it are treated as + UTF-8 strings instead of strings of individual 1-byte characters. -UTF-16 SUPPORT +UTF-16 AND UTF-32 SUPPORT - In order process UTF-16 strings, you must build PCRE's 16-bit library - with UTF support, and, in addition, you must call pcre16_compile() with - the PCRE_UTF16 option flag, or the pattern must start with the sequence - (*UTF16). When either of these is the case, both the pattern and any - subject strings that are matched against it are treated as UTF-16 - strings instead of strings of 16-bit characters. + In order process UTF-16 or UTF-32 strings, you must build PCRE's 16-bit + or 32-bit library with UTF support, and, in addition, you must call + pcre16_compile() or pcre32_compile() with the PCRE_UTF16 or PCRE_UTF32 + option flag, as appropriate. Alternatively, the pattern must start with + the sequence (*UTF16), (*UTF32), as appropriate, or (*UTF), which can + be used with either library. When UTF mode is set, both the pattern and + any subject strings that are matched against it are treated as UTF-16 + or UTF-32 strings instead of strings of individual 16-bit or 32-bit + characters. UTF SUPPORT OVERHEAD - If you compile PCRE with UTF support, but do not use it at run time, - the library will be a bit bigger, but the additional run time overhead - is limited to testing the PCRE_UTF8/16 flag occasionally, so should not - be very big. + If you compile PCRE with UTF support, but do not use it at run time, + the library will be a bit bigger, but the additional run time overhead + is limited to testing the PCRE_UTF[8|16|32] flag occasionally, so + should not be very big. UNICODE PROPERTY SUPPORT If PCRE is built with Unicode character property support (which implies - UTF support), the escape sequences \p{..}, \P{..}, and \X can be used. - The available properties that can be tested are limited to the general - category properties such as Lu for an upper case letter or Nd for a + UTF support), the escape sequences \p{..}, \P{..}, and \X can be used. + The available properties that can be tested are limited to the general + category properties such as Lu for an upper case letter or Nd for a decimal number, the Unicode script names such as Arabic or Han, and the - derived properties Any and L&. A full list is given in the pcrepattern - documentation. Only the short names for properties are supported. For - example, \p{L} matches a letter. Its Perl synonym, \p{Letter}, is not - supported. Furthermore, in Perl, many properties may optionally be - prefixed by "Is", for compatibility with Perl 5.6. PCRE does not sup- - port this. + derived properties Any and L&. Full lists is given in the pcrepattern + and pcresyntax documentation. Only the short names for properties are + supported. For example, \p{L} matches a letter. Its Perl synonym, + \p{Letter}, is not supported. Furthermore, in Perl, many properties + may optionally be prefixed by "Is", for compatibility with Perl 5.6. + PCRE does not support this. Validity of UTF-8 strings - When you set the PCRE_UTF8 flag, the byte strings passed as patterns + When you set the PCRE_UTF8 flag, the byte strings passed as patterns and subjects are (by default) checked for validity on entry to the rel- evant functions. The entire string is checked before any other process- - ing takes place. From release 7.3 of PCRE, the check is according the + ing takes place. From release 7.3 of PCRE, the check is according the rules of RFC 3629, which are themselves derived from the Unicode speci- - fication. Earlier releases of PCRE followed the rules of RFC 2279, - which allows the full range of 31-bit values (0 to 0x7FFFFFFF). The - current check allows only values in the range U+0 to U+10FFFF, exclud- - ing U+D800 to U+DFFF. + fication. Earlier releases of PCRE followed the rules of RFC 2279, + which allows the full range of 31-bit values (0 to 0x7FFFFFFF). The + current check allows only values in the range U+0 to U+10FFFF, exclud- + ing the surrogate area. (From release 8.33 the so-called "non-charac- + ter" code points are no longer excluded because Unicode corrigendum #9 + makes it clear that they should not be.) - The excluded code points are the "Surrogate Area" of Unicode. They are - reserved for use by UTF-16, where they are used in pairs to encode - codepoints with values greater than 0xFFFF. The code points that are - encoded by UTF-16 pairs are available independently in the UTF-8 encod- - ing. (In other words, the whole surrogate thing is a fudge for UTF-16 - which unfortunately messes up UTF-8.) + Characters in the "Surrogate Area" of Unicode are reserved for use by + UTF-16, where they are used in pairs to encode codepoints with values + greater than 0xFFFF. The code points that are encoded by UTF-16 pairs + are available independently in the UTF-8 and UTF-32 encodings. (In + other words, the whole surrogate thing is a fudge for UTF-16 which + unfortunately messes up UTF-8 and UTF-32.) If an invalid UTF-8 string is passed to PCRE, an error return is given. - At compile time, the only additional information is the offset to the + At compile time, the only additional information is the offset to the first byte of the failing character. The run-time functions pcre_exec() - and pcre_dfa_exec() also pass back this information, as well as a more - detailed reason code if the caller has provided memory in which to do + and pcre_dfa_exec() also pass back this information, as well as a more + detailed reason code if the caller has provided memory in which to do this. - In some situations, you may already know that your strings are valid, - and therefore want to skip these checks in order to improve perfor- - mance, for example in the case of a long subject string that is being - scanned repeatedly with different patterns. If you set the - PCRE_NO_UTF8_CHECK flag at compile time or at run time, PCRE assumes - that the pattern or subject it is given (respectively) contains only - valid UTF-8 codes. In this case, it does not diagnose an invalid UTF-8 - string. + In some situations, you may already know that your strings are valid, + and therefore want to skip these checks in order to improve perfor- + mance, for example in the case of a long subject string that is being + scanned repeatedly. If you set the PCRE_NO_UTF8_CHECK flag at compile + time or at run time, PCRE assumes that the pattern or subject it is + given (respectively) contains only valid UTF-8 codes. In this case, it + does not diagnose an invalid UTF-8 string. - If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, - what happens depends on why the string is invalid. If the string con- - forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a - string of characters in the range 0 to 0x7FFFFFFF by pcre_dfa_exec() - and the interpreted version of pcre_exec(). In other words, apart from - the initial validity test, these functions (when in UTF-8 mode) handle - strings according to the more liberal rules of RFC 2279. However, the - just-in-time (JIT) optimization for pcre_exec() supports only RFC 3629. - If you are using JIT optimization, or if the string does not even con- - form to RFC 2279, the result is undefined. Your program may crash. + Note that passing PCRE_NO_UTF8_CHECK to pcre_compile() just disables + the check for the pattern; it does not also apply to subject strings. + If you want to disable the check for a subject string you must pass + this option to pcre_exec() or pcre_dfa_exec(). - If you want to process strings of values in the full range 0 to - 0x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you can - set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in - this situation, you will have to apply your own validity check, and - avoid the use of JIT optimization. + If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, the + result is undefined and your program may crash. Validity of UTF-16 strings When you set the PCRE_UTF16 flag, the strings of 16-bit data units that are passed as patterns and subjects are (by default) checked for valid- - ity on entry to the relevant functions. Values other than those in the + ity on entry to the relevant functions. Values other than those in the surrogate range U+D800 to U+DFFF are independent code points. Values in the surrogate range must be used in pairs in the correct manner. - If an invalid UTF-16 string is passed to PCRE, an error return is - given. At compile time, the only additional information is the offset + If an invalid UTF-16 string is passed to PCRE, an error return is + given. At compile time, the only additional information is the offset to the first data unit of the failing character. The run-time functions pcre16_exec() and pcre16_dfa_exec() also pass back this information, as + well as a more detailed reason code if the caller has provided memory + in which to do this. + + In some situations, you may already know that your strings are valid, + and therefore want to skip these checks in order to improve perfor- + mance. If you set the PCRE_NO_UTF16_CHECK flag at compile time or at + run time, PCRE assumes that the pattern or subject it is given (respec- + tively) contains only valid UTF-16 sequences. In this case, it does not + diagnose an invalid UTF-16 string. However, if an invalid string is + passed, the result is undefined. + + Validity of UTF-32 strings + + When you set the PCRE_UTF32 flag, the strings of 32-bit data units that + are passed as patterns and subjects are (by default) checked for valid- + ity on entry to the relevant functions. This check allows only values + in the range U+0 to U+10FFFF, excluding the surrogate area U+D800 to + U+DFFF. + + If an invalid UTF-32 string is passed to PCRE, an error return is + given. At compile time, the only additional information is the offset + to the first data unit of the failing character. The run-time functions + pcre32_exec() and pcre32_dfa_exec() also pass back this information, as well as a more detailed reason code if the caller has provided memory in which to do this. In some situations, you may already know that your strings are valid, and therefore want to skip these checks in order to improve perfor- - mance. If you set the PCRE_NO_UTF16_CHECK flag at compile time or at + mance. If you set the PCRE_NO_UTF32_CHECK flag at compile time or at run time, PCRE assumes that the pattern or subject it is given (respec- - tively) contains only valid UTF-16 sequences. In this case, it does not - diagnose an invalid UTF-16 string. + tively) contains only valid UTF-32 sequences. In this case, it does not + diagnose an invalid UTF-32 string. However, if an invalid string is + passed, the result is undefined. General comments about UTF modes - 1. Codepoints less than 256 can be specified by either braced or - unbraced hexadecimal escape sequences (for example, \x{b3} or \xb3). - Larger values have to use braced sequences. + 1. Codepoints less than 256 can be specified in patterns by either + braced or unbraced hexadecimal escape sequences (for example, \x{b3} or + \xb3). Larger values have to use braced sequences. - 2. Octal numbers up to \777 are recognized, and in UTF-8 mode, they + 2. Octal numbers up to \777 are recognized, and in UTF-8 mode they match two-byte characters for values greater than \177. 3. Repeat quantifiers apply to complete UTF characters, not to individ- ual data units, for example: \x{100}{3}. - 4. The dot metacharacter matches one UTF character instead of a single + 4. The dot metacharacter matches one UTF character instead of a single data unit. - 5. The escape sequence \C can be used to match a single byte in UTF-8 - mode, or a single 16-bit data unit in UTF-16 mode, but its use can lead - to some strange effects because it breaks up multi-unit characters (see - the description of \C in the pcrepattern documentation). The use of \C - is not supported in the alternative matching function - pcre[16]_dfa_exec(), nor is it supported in UTF mode by the JIT opti- - mization of pcre[16]_exec(). If JIT optimization is requested for a UTF - pattern that contains \C, it will not succeed, and so the matching will - be carried out by the normal interpretive function. + 5. The escape sequence \C can be used to match a single byte in UTF-8 + mode, or a single 16-bit data unit in UTF-16 mode, or a single 32-bit + data unit in UTF-32 mode, but its use can lead to some strange effects + because it breaks up multi-unit characters (see the description of \C + in the pcrepattern documentation). The use of \C is not supported in + the alternative matching function pcre[16|32]_dfa_exec(), nor is it + supported in UTF mode by the JIT optimization of pcre[16|32]_exec(). If + JIT optimization is requested for a UTF pattern that contains \C, it + will not succeed, and so the matching will be carried out by the normal + interpretive function. 6. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly test characters of any code value, but, by default, the characters that @@ -7056,13 +8219,11 @@ UNICODE PROPERTY SUPPORT 9. Case-insensitive matching applies only to characters whose values are less than 128, unless PCRE is built with Unicode property support. - Even when Unicode property support is available, PCRE still uses its - own character tables when checking the case of low-valued characters, - so as not to degrade performance. The Unicode property information is - used only for characters with higher values. Furthermore, PCRE supports - case-insensitive matching only when there is a one-to-one mapping - between a letter's cases. There are a small number of many-to-one map- - pings in Unicode; these are not supported by PCRE. + A few Unicode characters such as Greek sigma have more than two code- + points that are case-equivalent. Up to and including PCRE release 8.31, + only one-to-one case mappings were supported, but later releases (with + Unicode property support) do treat as case-equivalent all versions of + characters such as Greek sigma. AUTHOR @@ -7074,18 +8235,18 @@ AUTHOR REVISION - Last updated: 14 April 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 27 February 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCREJIT(3) PCREJIT(3) +PCREJIT(3) Library Functions Manual PCREJIT(3) + NAME PCRE - Perl-compatible regular expressions - PCRE JUST-IN-TIME COMPILER SUPPORT Just-in-time compiling is a heavyweight optimization that can greatly @@ -7103,13 +8264,15 @@ PCRE JUST-IN-TIME COMPILER SUPPORT used. The code for this support was written by Zoltan Herczeg. -8-BIT and 16-BIT SUPPORT +8-BIT, 16-BIT AND 32-BIT SUPPORT - JIT support is available for both the 8-bit and 16-bit PCRE libraries. - To keep this documentation simple, only the 8-bit interface is - described in what follows. If you are using the 16-bit library, substi- - tute the 16-bit functions and 16-bit structures (for example, - pcre16_jit_stack instead of pcre_jit_stack). + JIT support is available for all of the 8-bit, 16-bit and 32-bit PCRE + libraries. To keep this documentation simple, only the 8-bit interface + is described in what follows. If you are using the 16-bit library, sub- + stitute the 16-bit functions and 16-bit structures (for example, + pcre16_jit_stack instead of pcre_jit_stack). If you are using the + 32-bit library, substitute the 32-bit functions and 32-bit structures + (for example, pcre32_jit_stack instead of pcre_jit_stack). AVAILABILITY OF JIT SUPPORT @@ -7123,6 +8286,7 @@ AVAILABILITY OF JIT SUPPORT Intel x86 32-bit and 64-bit MIPS 32-bit Power PC 32-bit and 64-bit + SPARC 32-bit (experimental) If --enable-jit is set on an unsupported platform, compilation fails. @@ -7130,8 +8294,10 @@ AVAILABILITY OF JIT SUPPORT port is available by calling pcre_config() with the PCRE_CONFIG_JIT option. The result is 1 when JIT is available, and 0 otherwise. How- ever, a simple program does not need to check this in order to use JIT. - The API is implemented in a way that falls back to the interpretive - code if JIT is not available. + The normal API is implemented in a way that falls back to the interpre- + tive code if JIT is not available. For programs that need the best pos- + sible performance, there is also a "fast path" API that is JIT-spe- + cific. If your program may sometimes be linked with versions of PCRE that are older than 8.20, but you want to use JIT when it is available, you can @@ -7149,17 +8315,18 @@ SIMPLE USE OF JIT pcre_exec(). (2) Use pcre_free_study() to free the pcre_extra block when it is - no longer needed, instead of just freeing it yourself. This - ensures that any JIT data is also freed. + no longer needed, instead of just freeing it yourself. This + ensures that + any JIT data is also freed. - For a program that may be linked with pre-8.20 versions of PCRE, you + For a program that may be linked with pre-8.20 versions of PCRE, you can insert #ifndef PCRE_STUDY_JIT_COMPILE #define PCRE_STUDY_JIT_COMPILE 0 #endif - so that no option is passed to pcre_study(), and then use something + so that no option is passed to pcre_study(), and then use something like this to free the study data: #ifdef PCRE_CONFIG_JIT @@ -7168,50 +8335,50 @@ SIMPLE USE OF JIT pcre_free(study_ptr); #endif - PCRE_STUDY_JIT_COMPILE requests the JIT compiler to generate code for - complete matches. If you want to run partial matches using the - PCRE_PARTIAL_HARD or PCRE_PARTIAL_SOFT options of pcre_exec(), you - should set one or both of the following options in addition to, or + PCRE_STUDY_JIT_COMPILE requests the JIT compiler to generate code for + complete matches. If you want to run partial matches using the + PCRE_PARTIAL_HARD or PCRE_PARTIAL_SOFT options of pcre_exec(), you + should set one or both of the following options in addition to, or instead of, PCRE_STUDY_JIT_COMPILE when you call pcre_study(): PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE - The JIT compiler generates different optimized code for each of the - three modes (normal, soft partial, hard partial). When pcre_exec() is - called, the appropriate code is run if it is available. Otherwise, the + The JIT compiler generates different optimized code for each of the + three modes (normal, soft partial, hard partial). When pcre_exec() is + called, the appropriate code is run if it is available. Otherwise, the pattern is matched using interpretive code. - In some circumstances you may need to call additional functions. These - are described in the section entitled "Controlling the JIT stack" + In some circumstances you may need to call additional functions. These + are described in the section entitled "Controlling the JIT stack" below. - If JIT support is not available, PCRE_STUDY_JIT_COMPILE etc. are + If JIT support is not available, PCRE_STUDY_JIT_COMPILE etc. are ignored, and no JIT data is created. Otherwise, the compiled pattern is - passed to the JIT compiler, which turns it into machine code that exe- - cutes much faster than the normal interpretive code. When pcre_exec() - is passed a pcre_extra block containing a pointer to JIT code of the - appropriate mode (normal or hard/soft partial), it obeys that code - instead of running the interpreter. The result is identical, but the + passed to the JIT compiler, which turns it into machine code that exe- + cutes much faster than the normal interpretive code. When pcre_exec() + is passed a pcre_extra block containing a pointer to JIT code of the + appropriate mode (normal or hard/soft partial), it obeys that code + instead of running the interpreter. The result is identical, but the compiled JIT code runs much faster. - There are some pcre_exec() options that are not supported for JIT exe- - cution. There are also some pattern items that JIT cannot handle. - Details are given below. In both cases, execution automatically falls - back to the interpretive code. If you want to know whether JIT was - actually used for a particular match, you should arrange for a JIT - callback function to be set up as described in the section entitled - "Controlling the JIT stack" below, even if you do not need to supply a - non-default JIT stack. Such a callback function is called whenever JIT - code is about to be obeyed. If the execution options are not right for + There are some pcre_exec() options that are not supported for JIT exe- + cution. There are also some pattern items that JIT cannot handle. + Details are given below. In both cases, execution automatically falls + back to the interpretive code. If you want to know whether JIT was + actually used for a particular match, you should arrange for a JIT + callback function to be set up as described in the section entitled + "Controlling the JIT stack" below, even if you do not need to supply a + non-default JIT stack. Such a callback function is called whenever JIT + code is about to be obeyed. If the execution options are not right for JIT execution, the callback function is not obeyed. - If the JIT compiler finds an unsupported item, no JIT data is gener- - ated. You can find out if JIT execution is available after studying a - pattern by calling pcre_fullinfo() with the PCRE_INFO_JIT option. A - result of 1 means that JIT compilation was successful. A result of 0 + If the JIT compiler finds an unsupported item, no JIT data is gener- + ated. You can find out if JIT execution is available after studying a + pattern by calling pcre_fullinfo() with the PCRE_INFO_JIT option. A + result of 1 means that JIT compilation was successful. A result of 0 means that JIT support is not available, or the pattern was not studied - with PCRE_STUDY_JIT_COMPILE etc., or the JIT compiler was not able to + with PCRE_STUDY_JIT_COMPILE etc., or the JIT compiler was not able to handle the pattern. Once a pattern has been studied, with or without JIT, it can be used as @@ -7220,83 +8387,77 @@ SIMPLE USE OF JIT UNSUPPORTED OPTIONS AND PATTERN ITEMS - The only pcre_exec() options that are supported for JIT execution are - PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, - PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PAR- - TIAL_SOFT. + The only pcre_exec() options that are supported for JIT execution are + PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK, PCRE_NO_UTF32_CHECK, PCRE_NOT- + BOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, PCRE_PAR- + TIAL_HARD, and PCRE_PARTIAL_SOFT. - The unsupported pattern items are: + The only unsupported pattern items are \C (match a single data unit) + when running in a UTF mode, and a callout immediately before an asser- + tion condition in a conditional group. - \C match a single byte; not supported in UTF-8 mode - (?Cn) callouts - (*PRUNE) ) - (*SKIP) ) backtracking control verbs - (*THEN) ) - Support for some of these may be added in future. - - RETURN VALUES FROM JIT EXECUTION - When a pattern is matched using JIT execution, the return values are - the same as those given by the interpretive pcre_exec() code, with the - addition of one new error code: PCRE_ERROR_JIT_STACKLIMIT. This means - that the memory used for the JIT stack was insufficient. See "Control- + When a pattern is matched using JIT execution, the return values are + the same as those given by the interpretive pcre_exec() code, with the + addition of one new error code: PCRE_ERROR_JIT_STACKLIMIT. This means + that the memory used for the JIT stack was insufficient. See "Control- ling the JIT stack" below for a discussion of JIT stack usage. For com- - patibility with the interpretive pcre_exec() code, no more than two- - thirds of the ovector argument is used for passing back captured sub- + patibility with the interpretive pcre_exec() code, no more than two- + thirds of the ovector argument is used for passing back captured sub- strings. - The error code PCRE_ERROR_MATCHLIMIT is returned by the JIT code if - searching a very large pattern tree goes on for too long, as it is in - the same circumstance when JIT is not used, but the details of exactly - what is counted are not the same. The PCRE_ERROR_RECURSIONLIMIT error + The error code PCRE_ERROR_MATCHLIMIT is returned by the JIT code if + searching a very large pattern tree goes on for too long, as it is in + the same circumstance when JIT is not used, but the details of exactly + what is counted are not the same. The PCRE_ERROR_RECURSIONLIMIT error code is never returned by JIT execution. SAVING AND RESTORING COMPILED PATTERNS - The code that is generated by the JIT compiler is architecture-spe- - cific, and is also position dependent. For those reasons it cannot be - saved (in a file or database) and restored later like the bytecode and - other data of a compiled pattern. Saving and restoring compiled pat- - terns is not something many people do. More detail about this facility - is given in the pcreprecompile documentation. It should be possible to - run pcre_study() on a saved and restored pattern, and thereby recreate - the JIT data, but because JIT compilation uses significant resources, - it is probably not worth doing this; you might as well recompile the + The code that is generated by the JIT compiler is architecture-spe- + cific, and is also position dependent. For those reasons it cannot be + saved (in a file or database) and restored later like the bytecode and + other data of a compiled pattern. Saving and restoring compiled pat- + terns is not something many people do. More detail about this facility + is given in the pcreprecompile documentation. It should be possible to + run pcre_study() on a saved and restored pattern, and thereby recreate + the JIT data, but because JIT compilation uses significant resources, + it is probably not worth doing this; you might as well recompile the original pattern. CONTROLLING THE JIT STACK When the compiled JIT code runs, it needs a block of memory to use as a - stack. By default, it uses 32K on the machine stack. However, some - large or complicated patterns need more than this. The error - PCRE_ERROR_JIT_STACKLIMIT is given when there is not enough stack. - Three functions are provided for managing blocks of memory for use as - JIT stacks. There is further discussion about the use of JIT stacks in + stack. By default, it uses 32K on the machine stack. However, some + large or complicated patterns need more than this. The error + PCRE_ERROR_JIT_STACKLIMIT is given when there is not enough stack. + Three functions are provided for managing blocks of memory for use as + JIT stacks. There is further discussion about the use of JIT stacks in the section entitled "JIT stack FAQ" below. - The pcre_jit_stack_alloc() function creates a JIT stack. Its arguments - are a starting size and a maximum size, and it returns a pointer to an - opaque structure of type pcre_jit_stack, or NULL if there is an error. - The pcre_jit_stack_free() function can be used to free a stack that is - no longer needed. (For the technically minded: the address space is + The pcre_jit_stack_alloc() function creates a JIT stack. Its arguments + are a starting size and a maximum size, and it returns a pointer to an + opaque structure of type pcre_jit_stack, or NULL if there is an error. + The pcre_jit_stack_free() function can be used to free a stack that is + no longer needed. (For the technically minded: the address space is allocated by mmap or VirtualAlloc.) - JIT uses far less memory for recursion than the interpretive code, and - a maximum stack size of 512K to 1M should be more than enough for any + JIT uses far less memory for recursion than the interpretive code, and + a maximum stack size of 512K to 1M should be more than enough for any pattern. - The pcre_assign_jit_stack() function specifies which stack JIT code + The pcre_assign_jit_stack() function specifies which stack JIT code should use. Its arguments are as follows: pcre_extra *extra pcre_jit_callback callback void *data - The extra argument must be the result of studying a pattern with + The extra argument must be the result of studying a pattern with PCRE_STUDY_JIT_COMPILE etc. There are three cases for the values of the other two options: @@ -7313,29 +8474,29 @@ CONTROLLING THE JIT STACK return value must be a valid JIT stack, the result of calling pcre_jit_stack_alloc(). - A callback function is obeyed whenever JIT code is about to be run; it - is not obeyed when pcre_exec() is called with options that are incom- + A callback function is obeyed whenever JIT code is about to be run; it + is not obeyed when pcre_exec() is called with options that are incom- patible for JIT execution. A callback function can therefore be used to - determine whether a match operation was executed by JIT or by the + determine whether a match operation was executed by JIT or by the interpreter. You may safely use the same JIT stack for more than one pattern (either - by assigning directly or by callback), as long as the patterns are all - matched sequentially in the same thread. In a multithread application, - if you do not specify a JIT stack, or if you assign or pass back NULL - from a callback, that is thread-safe, because each thread has its own - machine stack. However, if you assign or pass back a non-NULL JIT - stack, this must be a different stack for each thread so that the + by assigning directly or by callback), as long as the patterns are all + matched sequentially in the same thread. In a multithread application, + if you do not specify a JIT stack, or if you assign or pass back NULL + from a callback, that is thread-safe, because each thread has its own + machine stack. However, if you assign or pass back a non-NULL JIT + stack, this must be a different stack for each thread so that the application is thread-safe. - Strictly speaking, even more is allowed. You can assign the same non- - NULL stack to any number of patterns as long as they are not used for - matching by multiple threads at the same time. For example, you can - assign the same stack to all compiled patterns, and use a global mutex - in the callback to wait until the stack is available for use. However, + Strictly speaking, even more is allowed. You can assign the same non- + NULL stack to any number of patterns as long as they are not used for + matching by multiple threads at the same time. For example, you can + assign the same stack to all compiled patterns, and use a global mutex + in the callback to wait until the stack is available for use. However, this is an inefficient solution, and not recommended. - This is a suggestion for how a multithreaded program that needs to set + This is a suggestion for how a multithreaded program that needs to set up non-default JIT stacks might operate: During thread initalization @@ -7347,9 +8508,9 @@ CONTROLLING THE JIT STACK Use a one-line callback function return thread_local_var - All the functions described in this section do nothing if JIT is not - available, and pcre_assign_jit_stack() does nothing unless the extra - argument is non-NULL and points to a pcre_extra block that is the + All the functions described in this section do nothing if JIT is not + available, and pcre_assign_jit_stack() does nothing unless the extra + argument is non-NULL and points to a pcre_extra block that is the result of a successful study with PCRE_STUDY_JIT_COMPILE etc. @@ -7357,73 +8518,73 @@ JIT STACK FAQ (1) Why do we need JIT stacks? - PCRE (and JIT) is a recursive, depth-first engine, so it needs a stack - where the local data of the current node is pushed before checking its + PCRE (and JIT) is a recursive, depth-first engine, so it needs a stack + where the local data of the current node is pushed before checking its child nodes. Allocating real machine stack on some platforms is diffi- cult. For example, the stack chain needs to be updated every time if we - extend the stack on PowerPC. Although it is possible, its updating + extend the stack on PowerPC. Although it is possible, its updating time overhead decreases performance. So we do the recursion in memory. (2) Why don't we simply allocate blocks of memory with malloc()? - Modern operating systems have a nice feature: they can reserve an + Modern operating systems have a nice feature: they can reserve an address space instead of allocating memory. We can safely allocate mem- - ory pages inside this address space, so the stack could grow without + ory pages inside this address space, so the stack could grow without moving memory data (this is important because of pointers). Thus we can - allocate 1M address space, and use only a single memory page (usually - 4K) if that is enough. However, we can still grow up to 1M anytime if + allocate 1M address space, and use only a single memory page (usually + 4K) if that is enough. However, we can still grow up to 1M anytime if needed. (3) Who "owns" a JIT stack? The owner of the stack is the user program, not the JIT studied pattern - or anything else. The user program must ensure that if a stack is used - by pcre_exec(), (that is, it is assigned to the pattern currently run- + or anything else. The user program must ensure that if a stack is used + by pcre_exec(), (that is, it is assigned to the pattern currently run- ning), that stack must not be used by any other threads (to avoid over- writing the same memory area). The best practice for multithreaded pro- - grams is to allocate a stack for each thread, and return this stack + grams is to allocate a stack for each thread, and return this stack through the JIT callback function. (4) When should a JIT stack be freed? You can free a JIT stack at any time, as long as it will not be used by - pcre_exec() again. When you assign the stack to a pattern, only a - pointer is set. There is no reference counting or any other magic. You - can free the patterns and stacks in any order, anytime. Just do not - call pcre_exec() with a pattern pointing to an already freed stack, as - that will cause SEGFAULT. (Also, do not free a stack currently used by - pcre_exec() in another thread). You can also replace the stack for a - pattern at any time. You can even free the previous stack before + pcre_exec() again. When you assign the stack to a pattern, only a + pointer is set. There is no reference counting or any other magic. You + can free the patterns and stacks in any order, anytime. Just do not + call pcre_exec() with a pattern pointing to an already freed stack, as + that will cause SEGFAULT. (Also, do not free a stack currently used by + pcre_exec() in another thread). You can also replace the stack for a + pattern at any time. You can even free the previous stack before assigning a replacement. - (5) Should I allocate/free a stack every time before/after calling + (5) Should I allocate/free a stack every time before/after calling pcre_exec()? - No, because this is too costly in terms of resources. However, you - could implement some clever idea which release the stack if it is not - used in let's say two minutes. The JIT callback can help to achive this - without keeping a list of the currently JIT studied patterns. + No, because this is too costly in terms of resources. However, you + could implement some clever idea which release the stack if it is not + used in let's say two minutes. The JIT callback can help to achieve + this without keeping a list of the currently JIT studied patterns. - (6) OK, the stack is for long term memory allocation. But what happens - if a pattern causes stack overflow with a stack of 1M? Is that 1M kept + (6) OK, the stack is for long term memory allocation. But what happens + if a pattern causes stack overflow with a stack of 1M? Is that 1M kept until the stack is freed? - Especially on embedded sytems, it might be a good idea to release mem- - ory sometimes without freeing the stack. There is no API for this at - the moment. Probably a function call which returns with the currently - allocated memory for any stack and another which allows releasing mem- + Especially on embedded sytems, it might be a good idea to release mem- + ory sometimes without freeing the stack. There is no API for this at + the moment. Probably a function call which returns with the currently + allocated memory for any stack and another which allows releasing mem- ory (shrinking the stack) would be a good idea if someone needs this. (7) This is too much of a headache. Isn't there any better solution for JIT stack handling? - No, thanks to Windows. If POSIX threads were used everywhere, we could + No, thanks to Windows. If POSIX threads were used everywhere, we could throw out this complicated API. EXAMPLE CODE - This is a single-threaded example that specifies a JIT stack without + This is a single-threaded example that specifies a JIT stack without using a callback. int rc; @@ -7445,6 +8606,34 @@ EXAMPLE CODE pcre_jit_stack_free(jit_stack); +JIT FAST PATH API + + Because the API described above falls back to interpreted execution + when JIT is not available, it is convenient for programs that are writ- + ten for general use in many environments. However, calling JIT via + pcre_exec() does have a performance impact. Programs that are written + for use where JIT is known to be available, and which need the best + possible performance, can instead use a "fast path" API to call JIT + execution directly instead of calling pcre_exec() (obviously only for + patterns that have been successfully studied by JIT). + + The fast path function is called pcre_jit_exec(), and it takes exactly + the same arguments as pcre_exec(), plus one additional argument that + must point to a JIT stack. The JIT stack arrangements described above + do not apply. The return values are the same as for pcre_exec(). + + When you call pcre_exec(), as well as testing for invalid options, a + number of other sanity checks are performed on the arguments. For exam- + ple, if the subject pointer is NULL, or its length is negative, an + immediate error is given. Also, unless PCRE_NO_UTF[8|16|32] is set, a + UTF subject string is tested for validity. In the interests of speed, + these checks do not happen on the JIT fast path, and if invalid data is + passed, the result is undefined. + + Bypassing the sanity checks and the pcre_exec() wrapping can give + speedups of more than 10%. + + SEE ALSO pcreapi(3) @@ -7459,18 +8648,18 @@ AUTHOR REVISION - Last updated: 04 May 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 17 March 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCREPARTIAL(3) PCREPARTIAL(3) +PCREPARTIAL(3) Library Functions Manual PCREPARTIAL(3) + NAME PCRE - Perl-compatible regular expressions - PARTIAL MATCHING IN PCRE In normal use of PCRE, if the subject string that is passed to a match- @@ -7504,8 +8693,8 @@ PARTIAL MATCHING IN PCRE precedence. If you want to use partial matching with just-in-time optimized code, - you must call pcre_study() or pcre16_study() with one or both of these - options: + you must call pcre_study(), pcre16_study() or pcre32_study() with one + or both of these options: PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE @@ -7524,180 +8713,185 @@ PARTIAL MATCHING IN PCRE abled for partial matching. -PARTIAL MATCHING USING pcre_exec() OR pcre16_exec() +PARTIAL MATCHING USING pcre_exec() OR pcre[16|32]_exec() - A partial match occurs during a call to pcre_exec() or pcre16_exec() - when the end of the subject string is reached successfully, but match- - ing cannot continue because more characters are needed. However, at - least one character in the subject must have been inspected. This char- - acter need not form part of the final matched string; lookbehind asser- - tions and the \K escape sequence provide ways of inspecting characters - before the start of a matched substring. The requirement for inspecting - at least one character exists because an empty string can always be - matched; without such a restriction there would always be a partial - match of an empty string at the end of the subject. + A partial match occurs during a call to pcre_exec() or + pcre[16|32]_exec() when the end of the subject string is reached suc- + cessfully, but matching cannot continue because more characters are + needed. However, at least one character in the subject must have been + inspected. This character need not form part of the final matched + string; lookbehind assertions and the \K escape sequence provide ways + of inspecting characters before the start of a matched substring. The + requirement for inspecting at least one character exists because an + empty string can always be matched; without such a restriction there + would always be a partial match of an empty string at the end of the + subject. - If there are at least two slots in the offsets vector when a partial - match is returned, the first slot is set to the offset of the earliest + If there are at least two slots in the offsets vector when a partial + match is returned, the first slot is set to the offset of the earliest character that was inspected. For convenience, the second offset points to the end of the subject so that a substring can easily be identified. + If there are at least three slots in the offsets vector, the third slot + is set to the offset of the character where matching started. - For the majority of patterns, the first offset identifies the start of - the partially matched string. However, for patterns that contain look- - behind assertions, or \K, or begin with \b or \B, earlier characters - have been inspected while carrying out the match. For example: + For the majority of patterns, the contents of the first and third slots + will be the same. However, for patterns that contain lookbehind asser- + tions, or begin with \b or \B, characters before the one where matching + started may have been inspected while carrying out the match. For exam- + ple, consider this pattern: /(?<=abc)123/ This pattern matches "123", but only if it is preceded by "abc". If the - subject string is "xyzabc12", the offsets after a partial match are for - the substring "abc12", because all these characters are needed if - another match is tried with extra characters added to the subject. + subject string is "xyzabc12", the first two offsets after a partial + match are for the substring "abc12", because all these characters were + inspected. However, the third offset is set to 6, because that is the + offset where matching began. What happens when a partial match is identified depends on which of the two partial matching options are set. - PCRE_PARTIAL_SOFT WITH pcre_exec() OR pcre16_exec() + PCRE_PARTIAL_SOFT WITH pcre_exec() OR pcre[16|32]_exec() - If PCRE_PARTIAL_SOFT is set when pcre_exec() or pcre16_exec() identi- - fies a partial match, the partial match is remembered, but matching - continues as normal, and other alternatives in the pattern are tried. - If no complete match can be found, PCRE_ERROR_PARTIAL is returned - instead of PCRE_ERROR_NOMATCH. + If PCRE_PARTIAL_SOFT is set when pcre_exec() or pcre[16|32]_exec() + identifies a partial match, the partial match is remembered, but match- + ing continues as normal, and other alternatives in the pattern are + tried. If no complete match can be found, PCRE_ERROR_PARTIAL is + returned instead of PCRE_ERROR_NOMATCH. - This option is "soft" because it prefers a complete match over a par- - tial match. All the various matching items in a pattern behave as if - the subject string is potentially complete. For example, \z, \Z, and $ - match at the end of the subject, as normal, and for \b and \B the end + This option is "soft" because it prefers a complete match over a par- + tial match. All the various matching items in a pattern behave as if + the subject string is potentially complete. For example, \z, \Z, and $ + match at the end of the subject, as normal, and for \b and \B the end of the subject is treated as a non-alphanumeric. - If there is more than one partial match, the first one that was found + If there is more than one partial match, the first one that was found provides the data that is returned. Consider this pattern: /123\w+X|dogY/ - If this is matched against the subject string "abc123dog", both alter- - natives fail to match, but the end of the subject is reached during - matching, so PCRE_ERROR_PARTIAL is returned. The offsets are set to 3 - and 9, identifying "123dog" as the first partial match that was found. - (In this example, there are two partial matches, because "dog" on its + If this is matched against the subject string "abc123dog", both alter- + natives fail to match, but the end of the subject is reached during + matching, so PCRE_ERROR_PARTIAL is returned. The offsets are set to 3 + and 9, identifying "123dog" as the first partial match that was found. + (In this example, there are two partial matches, because "dog" on its own partially matches the second alternative.) - PCRE_PARTIAL_HARD WITH pcre_exec() OR pcre16_exec() + PCRE_PARTIAL_HARD WITH pcre_exec() OR pcre[16|32]_exec() - If PCRE_PARTIAL_HARD is set for pcre_exec() or pcre16_exec(), - PCRE_ERROR_PARTIAL is returned as soon as a partial match is found, + If PCRE_PARTIAL_HARD is set for pcre_exec() or pcre[16|32]_exec(), + PCRE_ERROR_PARTIAL is returned as soon as a partial match is found, without continuing to search for possible complete matches. This option is "hard" because it prefers an earlier partial match over a later com- - plete match. For this reason, the assumption is made that the end of - the supplied subject string may not be the true end of the available + plete match. For this reason, the assumption is made that the end of + the supplied subject string may not be the true end of the available data, and so, if \z, \Z, \b, \B, or $ are encountered at the end of the - subject, the result is PCRE_ERROR_PARTIAL, provided that at least one + subject, the result is PCRE_ERROR_PARTIAL, provided that at least one character in the subject has been inspected. Setting PCRE_PARTIAL_HARD also affects the way UTF-8 and UTF-16 subject - strings are checked for validity. Normally, an invalid sequence causes - the error PCRE_ERROR_BADUTF8 or PCRE_ERROR_BADUTF16. However, in the - special case of a truncated character at the end of the subject, - PCRE_ERROR_SHORTUTF8 or PCRE_ERROR_SHORTUTF16 is returned when + strings are checked for validity. Normally, an invalid sequence causes + the error PCRE_ERROR_BADUTF8 or PCRE_ERROR_BADUTF16. However, in the + special case of a truncated character at the end of the subject, + PCRE_ERROR_SHORTUTF8 or PCRE_ERROR_SHORTUTF16 is returned when PCRE_PARTIAL_HARD is set. Comparing hard and soft partial matching - The difference between the two partial matching options can be illus- + The difference between the two partial matching options can be illus- trated by a pattern such as: /dog(sbody)?/ - This matches either "dog" or "dogsbody", greedily (that is, it prefers - the longer string if possible). If it is matched against the string - "dog" with PCRE_PARTIAL_SOFT, it yields a complete match for "dog". + This matches either "dog" or "dogsbody", greedily (that is, it prefers + the longer string if possible). If it is matched against the string + "dog" with PCRE_PARTIAL_SOFT, it yields a complete match for "dog". However, if PCRE_PARTIAL_HARD is set, the result is PCRE_ERROR_PARTIAL. - On the other hand, if the pattern is made ungreedy the result is dif- + On the other hand, if the pattern is made ungreedy the result is dif- ferent: /dog(sbody)??/ - In this case the result is always a complete match because that is - found first, and matching never continues after finding a complete + In this case the result is always a complete match because that is + found first, and matching never continues after finding a complete match. It might be easier to follow this explanation by thinking of the two patterns like this: /dog(sbody)?/ is the same as /dogsbody|dog/ /dog(sbody)??/ is the same as /dog|dogsbody/ - The second pattern will never match "dogsbody", because it will always + The second pattern will never match "dogsbody", because it will always find the shorter match first. -PARTIAL MATCHING USING pcre_dfa_exec() OR pcre16_dfa_exec() +PARTIAL MATCHING USING pcre_dfa_exec() OR pcre[16|32]_dfa_exec() The DFA functions move along the subject string character by character, - without backtracking, searching for all possible matches simultane- - ously. If the end of the subject is reached before the end of the pat- - tern, there is the possibility of a partial match, again provided that + without backtracking, searching for all possible matches simultane- + ously. If the end of the subject is reached before the end of the pat- + tern, there is the possibility of a partial match, again provided that at least one character has been inspected. - When PCRE_PARTIAL_SOFT is set, PCRE_ERROR_PARTIAL is returned only if - there have been no complete matches. Otherwise, the complete matches - are returned. However, if PCRE_PARTIAL_HARD is set, a partial match - takes precedence over any complete matches. The portion of the string - that was inspected when the longest partial match was found is set as + When PCRE_PARTIAL_SOFT is set, PCRE_ERROR_PARTIAL is returned only if + there have been no complete matches. Otherwise, the complete matches + are returned. However, if PCRE_PARTIAL_HARD is set, a partial match + takes precedence over any complete matches. The portion of the string + that was inspected when the longest partial match was found is set as the first matching string, provided there are at least two slots in the offsets vector. - Because the DFA functions always search for all possible matches, and - there is no difference between greedy and ungreedy repetition, their - behaviour is different from the standard functions when PCRE_PAR- - TIAL_HARD is set. Consider the string "dog" matched against the + Because the DFA functions always search for all possible matches, and + there is no difference between greedy and ungreedy repetition, their + behaviour is different from the standard functions when PCRE_PAR- + TIAL_HARD is set. Consider the string "dog" matched against the ungreedy pattern shown above: /dog(sbody)??/ - Whereas the standard functions stop as soon as they find the complete - match for "dog", the DFA functions also find the partial match for + Whereas the standard functions stop as soon as they find the complete + match for "dog", the DFA functions also find the partial match for "dogsbody", and so return that when PCRE_PARTIAL_HARD is set. PARTIAL MATCHING AND WORD BOUNDARIES - If a pattern ends with one of sequences \b or \B, which test for word - boundaries, partial matching with PCRE_PARTIAL_SOFT can give counter- + If a pattern ends with one of sequences \b or \B, which test for word + boundaries, partial matching with PCRE_PARTIAL_SOFT can give counter- intuitive results. Consider this pattern: /\bcat\b/ This matches "cat", provided there is a word boundary at either end. If the subject string is "the cat", the comparison of the final "t" with a - following character cannot take place, so a partial match is found. - However, normal matching carries on, and \b matches at the end of the - subject when the last character is a letter, so a complete match is - found. The result, therefore, is not PCRE_ERROR_PARTIAL. Using - PCRE_PARTIAL_HARD in this case does yield PCRE_ERROR_PARTIAL, because + following character cannot take place, so a partial match is found. + However, normal matching carries on, and \b matches at the end of the + subject when the last character is a letter, so a complete match is + found. The result, therefore, is not PCRE_ERROR_PARTIAL. Using + PCRE_PARTIAL_HARD in this case does yield PCRE_ERROR_PARTIAL, because then the partial match takes precedence. FORMERLY RESTRICTED PATTERNS For releases of PCRE prior to 8.00, because of the way certain internal - optimizations were implemented in the pcre_exec() function, the - PCRE_PARTIAL option (predecessor of PCRE_PARTIAL_SOFT) could not be - used with all patterns. From release 8.00 onwards, the restrictions no - longer apply, and partial matching with can be requested for any pat- + optimizations were implemented in the pcre_exec() function, the + PCRE_PARTIAL option (predecessor of PCRE_PARTIAL_SOFT) could not be + used with all patterns. From release 8.00 onwards, the restrictions no + longer apply, and partial matching with can be requested for any pat- tern. Items that were formerly restricted were repeated single characters and - repeated metasequences. If PCRE_PARTIAL was set for a pattern that did - not conform to the restrictions, pcre_exec() returned the error code - PCRE_ERROR_BADPARTIAL (-13). This error code is no longer in use. The - PCRE_INFO_OKPARTIAL call to pcre_fullinfo() to find out if a compiled + repeated metasequences. If PCRE_PARTIAL was set for a pattern that did + not conform to the restrictions, pcre_exec() returned the error code + PCRE_ERROR_BADPARTIAL (-13). This error code is no longer in use. The + PCRE_INFO_OKPARTIAL call to pcre_fullinfo() to find out if a compiled pattern can be used for partial matching now always returns 1. EXAMPLE OF PARTIAL MATCHING USING PCRETEST - If the escape sequence \P is present in a pcretest data line, the - PCRE_PARTIAL_SOFT option is used for the match. Here is a run of + If the escape sequence \P is present in a pcretest data line, the + PCRE_PARTIAL_SOFT option is used for the match. Here is a run of pcretest that uses the date example quoted above: re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/ @@ -7713,24 +8907,24 @@ EXAMPLE OF PARTIAL MATCHING USING PCRETEST data> j\P No match - The first data string is matched completely, so pcretest shows the - matched substrings. The remaining four strings do not match the com- + The first data string is matched completely, so pcretest shows the + matched substrings. The remaining four strings do not match the com- plete pattern, but the first two are partial matches. Similar output is obtained if DFA matching is used. - If the escape sequence \P is present more than once in a pcretest data + If the escape sequence \P is present more than once in a pcretest data line, the PCRE_PARTIAL_HARD option is set for the match. -MULTI-SEGMENT MATCHING WITH pcre_dfa_exec() OR pcre16_dfa_exec() +MULTI-SEGMENT MATCHING WITH pcre_dfa_exec() OR pcre[16|32]_dfa_exec() - When a partial match has been found using a DFA matching function, it - is possible to continue the match by providing additional subject data - and calling the function again with the same compiled regular expres- - sion, this time setting the PCRE_DFA_RESTART option. You must pass the + When a partial match has been found using a DFA matching function, it + is possible to continue the match by providing additional subject data + and calling the function again with the same compiled regular expres- + sion, this time setting the PCRE_DFA_RESTART option. You must pass the same working space as before, because this is where details of the pre- - vious partial match are stored. Here is an example using pcretest, - using the \R escape sequence to set the PCRE_DFA_RESTART option (\D + vious partial match are stored. Here is an example using pcretest, + using the \R escape sequence to set the PCRE_DFA_RESTART option (\D specifies the use of the DFA matching function): re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/ @@ -7739,49 +8933,58 @@ MULTI-SEGMENT MATCHING WITH pcre_dfa_exec() OR pcre16_ data> n05\R\D 0: n05 - The first call has "23ja" as the subject, and requests partial match- - ing; the second call has "n05" as the subject for the continued - (restarted) match. Notice that when the match is complete, only the - last part is shown; PCRE does not retain the previously partially- - matched string. It is up to the calling program to do that if it needs + The first call has "23ja" as the subject, and requests partial match- + ing; the second call has "n05" as the subject for the continued + (restarted) match. Notice that when the match is complete, only the + last part is shown; PCRE does not retain the previously partially- + matched string. It is up to the calling program to do that if it needs to. - You can set the PCRE_PARTIAL_SOFT or PCRE_PARTIAL_HARD options with - PCRE_DFA_RESTART to continue partial matching over multiple segments. - This facility can be used to pass very long subject strings to the DFA + That means that, for an unanchored pattern, if a continued match fails, + it is not possible to try again at a new starting point. All this + facility is capable of doing is continuing with the previous match + attempt. In the previous example, if the second set of data is "ug23" + the result is no match, even though there would be a match for "aug23" + if the entire string were given at once. Depending on the application, + this may or may not be what you want. The only way to allow for start- + ing again at the next character is to retain the matched part of the + subject and try a new complete match. + + You can set the PCRE_PARTIAL_SOFT or PCRE_PARTIAL_HARD options with + PCRE_DFA_RESTART to continue partial matching over multiple segments. + This facility can be used to pass very long subject strings to the DFA matching functions. -MULTI-SEGMENT MATCHING WITH pcre_exec() OR pcre16_exec() +MULTI-SEGMENT MATCHING WITH pcre_exec() OR pcre[16|32]_exec() - From release 8.00, the standard matching functions can also be used to + From release 8.00, the standard matching functions can also be used to do multi-segment matching. Unlike the DFA functions, it is not possible - to restart the previous match with a new segment of data. Instead, new + to restart the previous match with a new segment of data. Instead, new data must be added to the previous subject string, and the entire match - re-run, starting from the point where the partial match occurred. Ear- + re-run, starting from the point where the partial match occurred. Ear- lier data can be discarded. - It is best to use PCRE_PARTIAL_HARD in this situation, because it does - not treat the end of a segment as the end of the subject when matching - \z, \Z, \b, \B, and $. Consider an unanchored pattern that matches + It is best to use PCRE_PARTIAL_HARD in this situation, because it does + not treat the end of a segment as the end of the subject when matching + \z, \Z, \b, \B, and $. Consider an unanchored pattern that matches dates: re> /\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d/ data> The date is 23ja\P\P Partial match: 23ja - At this stage, an application could discard the text preceding "23ja", - add on text from the next segment, and call the matching function - again. Unlike the DFA matching functions, the entire matching string - must always be available, and the complete matching process occurs for + At this stage, an application could discard the text preceding "23ja", + add on text from the next segment, and call the matching function + again. Unlike the DFA matching functions, the entire matching string + must always be available, and the complete matching process occurs for each call, so more memory and more processing time is needed. - Note: If the pattern contains lookbehind assertions, or \K, or starts + Note: If the pattern contains lookbehind assertions, or \K, or starts with \b or \B, the string that is returned for a partial match includes - characters that precede the partially matched string itself, because - these must be retained when adding on more characters for a subsequent - matching attempt. However, in some cases you may need to retain even - earlier characters, as discussed in the next section. + characters that precede the start of what would be returned for a com- + plete match, because it contains all the characters that were inspected + during the partial match. ISSUES WITH MULTI-SEGMENT MATCHING @@ -7800,15 +9003,36 @@ ISSUES WITH MULTI-SEGMENT MATCHING hind assertion later in the pattern could require even earlier charac- ters to be inspected. You can handle this case by using the PCRE_INFO_MAXLOOKBEHIND option of the pcre_fullinfo() or - pcre16_fullinfo() functions to obtain the length of the largest lookbe- - hind in the pattern. This length is given in characters, not bytes. If - you always retain at least that many characters before the partially - matched string, all should be well. (Of course, near the start of the - subject, fewer characters may be present; in that case all characters - should be retained.) + pcre[16|32]_fullinfo() functions to obtain the length of the longest + lookbehind in the pattern. This length is given in characters, not + bytes. If you always retain at least that many characters before the + partially matched string, all should be well. (Of course, near the + start of the subject, fewer characters may be present; in that case all + characters should be retained.) - 3. Because a partial match must always contain at least one character, - what might be considered a partial match of an empty string actually + From release 8.33, there is a more accurate way of deciding which char- + acters to retain. Instead of subtracting the length of the longest + lookbehind from the earliest inspected character (offsets[0]), the + match start position (offsets[2]) should be used, and the next match + attempt started at the offsets[2] character by setting the startoffset + argument of pcre_exec() or pcre_dfa_exec(). + + For example, if the pattern "(?<=123)abc" is partially matched against + the string "xx123a", the three offset values returned are 2, 6, and 5. + This indicates that the matching process that gave a partial match + started at offset 5, but the characters "123a" were all inspected. The + maximum lookbehind for that pattern is 3, so taking that away from 5 + shows that we need only keep "123a", and the next match attempt can be + started at offset 3 (that is, at "a") when further characters have been + added. When the match start is not the earliest inspected character, + pcretest shows it explicitly: + + re> "(?<=123)abc" + data> xx123a\P\P + Partial match at offset 5: 123a + + 3. Because a partial match must always contain at least one character, + what might be considered a partial match of an empty string actually gives a "no match" result. For example: re> /c(?<=abc)x/ @@ -7816,19 +9040,19 @@ ISSUES WITH MULTI-SEGMENT MATCHING No match If the next segment begins "cx", a match should be found, but this will - only happen if characters from the previous segment are retained. For - this reason, a "no match" result should be interpreted as "partial + only happen if characters from the previous segment are retained. For + this reason, a "no match" result should be interpreted as "partial match of an empty string" when the pattern contains lookbehinds. - 4. Matching a subject string that is split into multiple segments may - not always produce exactly the same result as matching over one single - long string, especially when PCRE_PARTIAL_SOFT is used. The section - "Partial Matching and Word Boundaries" above describes an issue that - arises if the pattern ends with \b or \B. Another kind of difference - may occur when there are multiple matching possibilities, because (for - PCRE_PARTIAL_SOFT) a partial match result is given only when there are + 4. Matching a subject string that is split into multiple segments may + not always produce exactly the same result as matching over one single + long string, especially when PCRE_PARTIAL_SOFT is used. The section + "Partial Matching and Word Boundaries" above describes an issue that + arises if the pattern ends with \b or \B. Another kind of difference + may occur when there are multiple matching possibilities, because (for + PCRE_PARTIAL_SOFT) a partial match result is given only when there are no completed matches. This means that as soon as the shortest match has - been found, continuation to a new subject segment is no longer possi- + been found, continuation to a new subject segment is no longer possi- ble. Consider again this pcretest example: re> /dog(sbody)?/ @@ -7842,18 +9066,18 @@ ISSUES WITH MULTI-SEGMENT MATCHING 0: dogsbody 1: dog - The first data line passes the string "dogsb" to a standard matching - function, setting the PCRE_PARTIAL_SOFT option. Although the string is - a partial match for "dogsbody", the result is not PCRE_ERROR_PARTIAL, - because the shorter string "dog" is a complete match. Similarly, when - the subject is presented to a DFA matching function in several parts - ("do" and "gsb" being the first two) the match stops when "dog" has - been found, and it is not possible to continue. On the other hand, if - "dogsbody" is presented as a single string, a DFA matching function + The first data line passes the string "dogsb" to a standard matching + function, setting the PCRE_PARTIAL_SOFT option. Although the string is + a partial match for "dogsbody", the result is not PCRE_ERROR_PARTIAL, + because the shorter string "dog" is a complete match. Similarly, when + the subject is presented to a DFA matching function in several parts + ("do" and "gsb" being the first two) the match stops when "dog" has + been found, and it is not possible to continue. On the other hand, if + "dogsbody" is presented as a single string, a DFA matching function finds both matches. - Because of these problems, it is best to use PCRE_PARTIAL_HARD when - matching multi-segment data. The example above then behaves differ- + Because of these problems, it is best to use PCRE_PARTIAL_HARD when + matching multi-segment data. The example above then behaves differ- ently: re> /dog(sbody)?/ @@ -7865,25 +9089,25 @@ ISSUES WITH MULTI-SEGMENT MATCHING Partial match: gsb 5. Patterns that contain alternatives at the top level which do not all - start with the same pattern item may not work as expected when + start with the same pattern item may not work as expected when PCRE_DFA_RESTART is used. For example, consider this pattern: 1234|3789 - If the first part of the subject is "ABC123", a partial match of the - first alternative is found at offset 3. There is no partial match for + If the first part of the subject is "ABC123", a partial match of the + first alternative is found at offset 3. There is no partial match for the second alternative, because such a match does not start at the same - point in the subject string. Attempting to continue with the string - "7890" does not yield a match because only those alternatives that - match at one point in the subject are remembered. The problem arises - because the start of the second alternative matches within the first - alternative. There is no problem with anchored patterns or patterns + point in the subject string. Attempting to continue with the string + "7890" does not yield a match because only those alternatives that + match at one point in the subject are remembered. The problem arises + because the start of the second alternative matches within the first + alternative. There is no problem with anchored patterns or patterns such as: 1234|ABCD - where no string can be a partial match for both alternatives. This is - not a problem if a standard matching function is used, because the + where no string can be a partial match for both alternatives. This is + not a problem if a standard matching function is used, because the entire match has to be rerun each time: re> /1234|3789/ @@ -7893,10 +9117,10 @@ ISSUES WITH MULTI-SEGMENT MATCHING 0: 3789 Of course, instead of using PCRE_DFA_RESTART, the same technique of re- - running the entire match can also be used with the DFA matching func- - tions. Another possibility is to work with two buffers. If a partial - match at offset n in the first buffer is followed by "no match" when - PCRE_DFA_RESTART is used on the second buffer, you can then try a new + running the entire match can also be used with the DFA matching func- + tions. Another possibility is to work with two buffers. If a partial + match at offset n in the first buffer is followed by "no match" when + PCRE_DFA_RESTART is used on the second buffer, you can then try a new match starting at offset n+1 in the first buffer. @@ -7909,18 +9133,18 @@ AUTHOR REVISION - Last updated: 24 February 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 02 July 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCREPRECOMPILE(3) PCREPRECOMPILE(3) +PCREPRECOMPILE(3) Library Functions Manual PCREPRECOMPILE(3) + NAME PCRE - Perl-compatible regular expressions - SAVING AND RE-USING PRECOMPILED PCRE PATTERNS If you are running an application that uses a large number of regular @@ -7934,10 +9158,10 @@ SAVING AND RE-USING PRECOMPILED PCRE PATTERNS If you save compiled patterns to a file, you can copy them to a differ- ent host and run them there. If the two hosts have different endianness - (byte order), you should run the pcre[16]_pattern_to_host_byte_order() - function on the new host before trying to match the pattern. The match- - ing functions return PCRE_ERROR_BADENDIANNESS if they detect a pattern - with the wrong endianness. + (byte order), you should run the pcre[16|32]_pat- + tern_to_host_byte_order() function on the new host before trying to + match the pattern. The matching functions return PCRE_ERROR_BADENDIAN- + NESS if they detect a pattern with the wrong endianness. Compiling regular expressions with one version of PCRE for use with a different version is not guaranteed to work and may cause crashes, and @@ -7947,13 +9171,13 @@ SAVING AND RE-USING PRECOMPILED PCRE PATTERNS SAVING A COMPILED PATTERN - The value returned by pcre[16]_compile() points to a single block of + The value returned by pcre[16|32]_compile() points to a single block of memory that holds the compiled pattern and associated data. You can - find the length of this block in bytes by calling pcre[16]_fullinfo() - with an argument of PCRE_INFO_SIZE. You can then save the data in any - appropriate manner. Here is sample code for the 8-bit library that com- - piles a pattern and writes it to a file. It assumes that the variable - fd refers to a file that is open for output: + find the length of this block in bytes by calling + pcre[16|32]_fullinfo() with an argument of PCRE_INFO_SIZE. You can then + save the data in any appropriate manner. Here is sample code for the + 8-bit library that compiles a pattern and writes it to a file. It + assumes that the variable fd refers to a file that is open for output: int erroroffset, rc, size; char *error; @@ -7988,41 +9212,45 @@ SAVING A COMPILED PATTERN the PCRE_STUDY_JIT_COMPILE was used, the just-in-time data that is cre- ated cannot be saved because it is too dependent on the current envi- ronment. When studying generates additional information, - pcre[16]_study() returns a pointer to a pcre[16]_extra data block. Its - format is defined in the section on matching a pattern in the pcreapi - documentation. The study_data field points to the binary study data, - and this is what you must save (not the pcre[16]_extra block itself). - The length of the study data can be obtained by calling - pcre[16]_fullinfo() with an argument of PCRE_INFO_STUDYSIZE. Remember - to check that pcre[16]_study() did return a non-NULL value before try- - ing to save the study data. + pcre[16|32]_study() returns a pointer to a pcre[16|32]_extra data + block. Its format is defined in the section on matching a pattern in + the pcreapi documentation. The study_data field points to the binary + study data, and this is what you must save (not the pcre[16|32]_extra + block itself). The length of the study data can be obtained by calling + pcre[16|32]_fullinfo() with an argument of PCRE_INFO_STUDYSIZE. Remem- + ber to check that pcre[16|32]_study() did return a non-NULL value + before trying to save the study data. RE-USING A PRECOMPILED PATTERN Re-using a precompiled pattern is straightforward. Having reloaded it - into main memory, called pcre[16]_pattern_to_host_byte_order() if nec- - essary, you pass its pointer to pcre[16]_exec() or pcre[16]_dfa_exec() - in the usual way. + into main memory, called pcre[16|32]_pattern_to_host_byte_order() if + necessary, you pass its pointer to pcre[16|32]_exec() or + pcre[16|32]_dfa_exec() in the usual way. However, if you passed a pointer to custom character tables when the - pattern was compiled (the tableptr argument of pcre[16]_compile()), you - must now pass a similar pointer to pcre[16]_exec() or - pcre[16]_dfa_exec(), because the value saved with the compiled pattern - will obviously be nonsense. A field in a pcre[16]_extra() block is used - to pass this data, as described in the section on matching a pattern in - the pcreapi documentation. + pattern was compiled (the tableptr argument of pcre[16|32]_compile()), + you must now pass a similar pointer to pcre[16|32]_exec() or + pcre[16|32]_dfa_exec(), because the value saved with the compiled pat- + tern will obviously be nonsense. A field in a pcre[16|32]_extra() block + is used to pass this data, as described in the section on matching a + pattern in the pcreapi documentation. + Warning: The tables that pcre_exec() and pcre_dfa_exec() use must be + the same as those that were used when the pattern was compiled. If this + is not the case, the behaviour is undefined. + If you did not provide custom character tables when the pattern was compiled, the pointer in the compiled pattern is NULL, which causes the matching functions to use PCRE's internal tables. Thus, you do not need to take any special action at run time in this case. If you saved study data with the compiled pattern, you need to create - your own pcre[16]_extra data block and set the study_data field to + your own pcre[16|32]_extra data block and set the study_data field to point to the reloaded study data. You must also set the PCRE_EXTRA_STUDY_DATA bit in the flags field to indicate that study - data is present. Then pass the pcre[16]_extra block to the matching + data is present. Then pass the pcre[16|32]_extra block to the matching function in the usual way. If the pattern was studied for just-in-time optimization, that data cannot be saved, and so is lost by a save/restore cycle. @@ -8044,18 +9272,18 @@ AUTHOR REVISION - Last updated: 10 January 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 12 November 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCREPERFORM(3) PCREPERFORM(3) +PCREPERFORM(3) Library Functions Manual PCREPERFORM(3) + NAME PCRE - Perl-compatible regular expressions - PCRE PERFORMANCE Two aspects of performance are discussed below: memory usage and pro- @@ -8115,30 +9343,30 @@ COMPILED PATTERN MEMORY USAGE STACK USAGE AT RUN TIME - When pcre_exec() or pcre16_exec() is used for matching, certain kinds - of pattern can cause it to use large amounts of the process stack. In - some environments the default process stack is quite small, and if it - runs out the result is often SIGSEGV. This issue is probably the most - frequently raised problem with PCRE. Rewriting your pattern can often - help. The pcrestack documentation discusses this issue in detail. + When pcre_exec() or pcre[16|32]_exec() is used for matching, certain + kinds of pattern can cause it to use large amounts of the process + stack. In some environments the default process stack is quite small, + and if it runs out the result is often SIGSEGV. This issue is probably + the most frequently raised problem with PCRE. Rewriting your pattern + can often help. The pcrestack documentation discusses this issue in + detail. PROCESSING TIME - Certain items in regular expression patterns are processed more effi- + Certain items in regular expression patterns are processed more effi- ciently than others. It is more efficient to use a character class like - [aeiou] than a set of single-character alternatives such as - (a|e|i|o|u). In general, the simplest construction that provides the + [aeiou] than a set of single-character alternatives such as + (a|e|i|o|u). In general, the simplest construction that provides the required behaviour is usually the most efficient. Jeffrey Friedl's book - contains a lot of useful general discussion about optimizing regular - expressions for efficient performance. This document contains a few + contains a lot of useful general discussion about optimizing regular + expressions for efficient performance. This document contains a few observations about PCRE. - Using Unicode character properties (the \p, \P, and \X escapes) is - slow, because PCRE has to scan a structure that contains data for over - fifteen thousand characters whenever it needs a character's property. - If you can find an alternative pattern that does not use character - properties, it will probably be faster. + Using Unicode character properties (the \p, \P, and \X escapes) is + slow, because PCRE has to use a multi-stage table lookup whenever it + needs a character's property. If you can find an alternative pattern + that does not use character properties, it will probably be faster. By default, the escape sequences \b, \d, \s, and \w, and the POSIX character classes such as [:alpha:] do not use Unicode properties, @@ -8214,20 +9442,20 @@ AUTHOR REVISION - Last updated: 09 January 2012 + Last updated: 25 August 2012 Copyright (c) 1997-2012 University of Cambridge. ------------------------------------------------------------------------------ -PCREPOSIX(3) PCREPOSIX(3) +PCREPOSIX(3) Library Functions Manual PCREPOSIX(3) + NAME PCRE - Perl-compatible regular expressions. +SYNOPSIS -SYNOPSIS OF POSIX API - #include int regcomp(regex_t *preg, const char *pattern, @@ -8235,8 +9463,7 @@ SYNOPSIS OF POSIX API int regexec(regex_t *preg, const char *string, size_t nmatch, regmatch_t pmatch[], int eflags); - - size_t regerror(int errcode, const regex_t *preg, + size_t regerror(int errcode, const regex_t *preg, char *errbuf, size_t errbuf_size); void regfree(regex_t *preg); @@ -8247,49 +9474,50 @@ DESCRIPTION This set of functions provides a POSIX-style API for the PCRE regular expression 8-bit library. See the pcreapi documentation for a descrip- tion of PCRE's native API, which contains much additional functional- - ity. There is no POSIX-style wrapper for PCRE's 16-bit library. + ity. There is no POSIX-style wrapper for PCRE's 16-bit and 32-bit + library. The functions described here are just wrapper functions that ultimately call the PCRE native API. Their prototypes are defined in the - pcreposix.h header file, and on Unix systems the library itself is - called pcreposix.a, so can be accessed by adding -lpcreposix to the - command for linking an application that uses them. Because the POSIX + pcreposix.h header file, and on Unix systems the library itself is + called pcreposix.a, so can be accessed by adding -lpcreposix to the + command for linking an application that uses them. Because the POSIX functions call the native ones, it is also necessary to add -lpcre. - I have implemented only those POSIX option bits that can be reasonably - mapped to PCRE native options. In addition, the option REG_EXTENDED is - defined with the value zero. This has no effect, but since programs - that are written to the POSIX interface often use it, this makes it - easier to slot in PCRE as a replacement library. Other POSIX options + I have implemented only those POSIX option bits that can be reasonably + mapped to PCRE native options. In addition, the option REG_EXTENDED is + defined with the value zero. This has no effect, but since programs + that are written to the POSIX interface often use it, this makes it + easier to slot in PCRE as a replacement library. Other POSIX options are not even defined. - There are also some other options that are not defined by POSIX. These + There are also some other options that are not defined by POSIX. These have been added at the request of users who want to make use of certain PCRE-specific features via the POSIX calling interface. - When PCRE is called via these functions, it is only the API that is - POSIX-like in style. The syntax and semantics of the regular expres- - sions themselves are still those of Perl, subject to the setting of - various PCRE options, as described below. "POSIX-like in style" means - that the API approximates to the POSIX definition; it is not fully - POSIX-compatible, and in multi-byte encoding domains it is probably + When PCRE is called via these functions, it is only the API that is + POSIX-like in style. The syntax and semantics of the regular expres- + sions themselves are still those of Perl, subject to the setting of + various PCRE options, as described below. "POSIX-like in style" means + that the API approximates to the POSIX definition; it is not fully + POSIX-compatible, and in multi-byte encoding domains it is probably even less compatible. - The header for these functions is supplied as pcreposix.h to avoid any - potential clash with other POSIX libraries. It can, of course, be + The header for these functions is supplied as pcreposix.h to avoid any + potential clash with other POSIX libraries. It can, of course, be renamed or aliased as regex.h, which is the "correct" name. It provides - two structure types, regex_t for compiled internal forms, and reg- - match_t for returning captured substrings. It also defines some con- - stants whose names start with "REG_"; these are used for setting + two structure types, regex_t for compiled internal forms, and reg- + match_t for returning captured substrings. It also defines some con- + stants whose names start with "REG_"; these are used for setting options and identifying error codes. COMPILING A PATTERN - The function regcomp() is called to compile a pattern into an internal - form. The pattern is a C string terminated by a binary zero, and is - passed in the argument pattern. The preg argument is a pointer to a - regex_t structure that is used as a base for storing information about + The function regcomp() is called to compile a pattern into an internal + form. The pattern is a C string terminated by a binary zero, and is + passed in the argument pattern. The preg argument is a pointer to a + regex_t structure that is used as a base for storing information about the compiled regular expression. The argument cflags is either zero, or contains one or more of the bits @@ -8303,58 +9531,58 @@ COMPILING A PATTERN REG_ICASE - The PCRE_CASELESS option is set when the regular expression is passed + The PCRE_CASELESS option is set when the regular expression is passed for compilation to the native function. REG_NEWLINE - The PCRE_MULTILINE option is set when the regular expression is passed - for compilation to the native function. Note that this does not mimic - the defined POSIX behaviour for REG_NEWLINE (see the following sec- + The PCRE_MULTILINE option is set when the regular expression is passed + for compilation to the native function. Note that this does not mimic + the defined POSIX behaviour for REG_NEWLINE (see the following sec- tion). REG_NOSUB - The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is + The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is passed for compilation to the native function. In addition, when a pat- - tern that is compiled with this flag is passed to regexec() for match- - ing, the nmatch and pmatch arguments are ignored, and no captured + tern that is compiled with this flag is passed to regexec() for match- + ing, the nmatch and pmatch arguments are ignored, and no captured strings are returned. REG_UCP - The PCRE_UCP option is set when the regular expression is passed for - compilation to the native function. This causes PCRE to use Unicode - properties when matchine \d, \w, etc., instead of just recognizing + The PCRE_UCP option is set when the regular expression is passed for + compilation to the native function. This causes PCRE to use Unicode + properties when matchine \d, \w, etc., instead of just recognizing ASCII values. Note that REG_UTF8 is not part of the POSIX standard. REG_UNGREEDY - The PCRE_UNGREEDY option is set when the regular expression is passed - for compilation to the native function. Note that REG_UNGREEDY is not + The PCRE_UNGREEDY option is set when the regular expression is passed + for compilation to the native function. Note that REG_UNGREEDY is not part of the POSIX standard. REG_UTF8 - The PCRE_UTF8 option is set when the regular expression is passed for - compilation to the native function. This causes the pattern itself and - all data strings used for matching it to be treated as UTF-8 strings. + The PCRE_UTF8 option is set when the regular expression is passed for + compilation to the native function. This causes the pattern itself and + all data strings used for matching it to be treated as UTF-8 strings. Note that REG_UTF8 is not part of the POSIX standard. - In the absence of these flags, no options are passed to the native - function. This means the the regex is compiled with PCRE default - semantics. In particular, the way it handles newline characters in the - subject string is the Perl way, not the POSIX way. Note that setting - PCRE_MULTILINE has only some of the effects specified for REG_NEWLINE. - It does not affect the way newlines are matched by . (they are not) or + In the absence of these flags, no options are passed to the native + function. This means the the regex is compiled with PCRE default + semantics. In particular, the way it handles newline characters in the + subject string is the Perl way, not the POSIX way. Note that setting + PCRE_MULTILINE has only some of the effects specified for REG_NEWLINE. + It does not affect the way newlines are matched by . (they are not) or by a negative class such as [^a] (they are). - The yield of regcomp() is zero on success, and non-zero otherwise. The + The yield of regcomp() is zero on success, and non-zero otherwise. The preg structure is filled in on success, and one member of the structure - is public: re_nsub contains the number of capturing subpatterns in the + is public: re_nsub contains the number of capturing subpatterns in the regular expression. Various error codes are defined in the header file. - NOTE: If the yield of regcomp() is non-zero, you must not attempt to + NOTE: If the yield of regcomp() is non-zero, you must not attempt to use the contents of the preg structure. If, for example, you pass it to regexec(), the result is undefined and your program is likely to crash. @@ -8362,9 +9590,9 @@ COMPILING A PATTERN MATCHING NEWLINE CHARACTERS This area is not simple, because POSIX and Perl take different views of - things. It is not possible to get PCRE to obey POSIX semantics, but - then PCRE was never intended to be a POSIX engine. The following table - lists the different possibilities for matching newline characters in + things. It is not possible to get PCRE to obey POSIX semantics, but + then PCRE was never intended to be a POSIX engine. The following table + lists the different possibilities for matching newline characters in PCRE: Default Change with @@ -8386,19 +9614,19 @@ MATCHING NEWLINE CHARACTERS ^ matches \n in middle no REG_NEWLINE PCRE's behaviour is the same as Perl's, except that there is no equiva- - lent for PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is + lent for PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is no way to stop newline from matching [^a]. - The default POSIX newline handling can be obtained by setting - PCRE_DOTALL and PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE + The default POSIX newline handling can be obtained by setting + PCRE_DOTALL and PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE behave exactly as for the REG_NEWLINE action. MATCHING A PATTERN - The function regexec() is called to match a compiled pattern preg - against a given string, which is by default terminated by a zero byte - (but see REG_STARTEND below), subject to the options in eflags. These + The function regexec() is called to match a compiled pattern preg + against a given string, which is by default terminated by a zero byte + (but see REG_STARTEND below), subject to the options in eflags. These can be: REG_NOTBOL @@ -8420,17 +9648,17 @@ MATCHING A PATTERN REG_STARTEND - The string is considered to start at string + pmatch[0].rm_so and to - have a terminating NUL located at string + pmatch[0].rm_eo (there need - not actually be a NUL at that location), regardless of the value of - nmatch. This is a BSD extension, compatible with but not specified by - IEEE Standard 1003.2 (POSIX.2), and should be used with caution in + The string is considered to start at string + pmatch[0].rm_so and to + have a terminating NUL located at string + pmatch[0].rm_eo (there need + not actually be a NUL at that location), regardless of the value of + nmatch. This is a BSD extension, compatible with but not specified by + IEEE Standard 1003.2 (POSIX.2), and should be used with caution in software intended to be portable to other systems. Note that a non-zero rm_so does not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not how it is matched. - If the pattern was compiled with the REG_NOSUB flag, no data about any - matched strings is returned. The nmatch and pmatch arguments of + If the pattern was compiled with the REG_NOSUB flag, no data about any + matched strings is returned. The nmatch and pmatch arguments of regexec() are ignored. If the value of nmatch is zero, or if the value pmatch is NULL, no data @@ -8438,34 +9666,34 @@ MATCHING A PATTERN Otherwise,the portion of the string that was matched, and also any cap- tured substrings, are returned via the pmatch argument, which points to - an array of nmatch structures of type regmatch_t, containing the mem- - bers rm_so and rm_eo. These contain the offset to the first character - of each substring and the offset to the first character after the end - of each substring, respectively. The 0th element of the vector relates - to the entire portion of string that was matched; subsequent elements - relate to the capturing subpatterns of the regular expression. Unused + an array of nmatch structures of type regmatch_t, containing the mem- + bers rm_so and rm_eo. These contain the offset to the first character + of each substring and the offset to the first character after the end + of each substring, respectively. The 0th element of the vector relates + to the entire portion of string that was matched; subsequent elements + relate to the capturing subpatterns of the regular expression. Unused entries in the array have both structure members set to -1. - A successful match yields a zero return; various error codes are - defined in the header file, of which REG_NOMATCH is the "expected" + A successful match yields a zero return; various error codes are + defined in the header file, of which REG_NOMATCH is the "expected" failure code. ERROR MESSAGES The regerror() function maps a non-zero errorcode from either regcomp() - or regexec() to a printable message. If preg is not NULL, the error + or regexec() to a printable message. If preg is not NULL, the error should have arisen from the use of that structure. A message terminated - by a binary zero is placed in errbuf. The length of the message, - including the zero, is limited to errbuf_size. The yield of the func- + by a binary zero is placed in errbuf. The length of the message, + including the zero, is limited to errbuf_size. The yield of the func- tion is the size of buffer needed to hold the whole message. MEMORY USAGE - Compiling a regular expression causes memory to be allocated and asso- - ciated with the preg structure. The function regfree() frees all such - memory, after which preg may no longer be used as a compiled expres- + Compiling a regular expression causes memory to be allocated and asso- + ciated with the preg structure. The function regfree() frees all such + memory, after which preg may no longer be used as a compiled expres- sion. @@ -8483,13 +9711,13 @@ REVISION ------------------------------------------------------------------------------ -PCRECPP(3) PCRECPP(3) +PCRECPP(3) Library Functions Manual PCRECPP(3) + NAME PCRE - Perl-compatible regular expressions. - SYNOPSIS OF C++ WRAPPER #include @@ -8501,13 +9729,14 @@ DESCRIPTION functionality was added by Giuseppe Maxia. This brief man page was con- structed from the notes in the pcrecpp.h file, which should be con- sulted for further details. Note that the C++ wrapper supports only the - original 8-bit PCRE library. There is no 16-bit support at present. + original 8-bit PCRE library. There is no 16-bit or 32-bit support at + present. MATCHING INTERFACE - The "FullMatch" operation checks that supplied text matches a supplied - pattern exactly. If pointer arguments are supplied, it copies matched + The "FullMatch" operation checks that supplied text matches a supplied + pattern exactly. If pointer arguments are supplied, it copies matched sub-strings that match sub-patterns into them. Example: successful match @@ -8521,10 +9750,10 @@ MATCHING INTERFACE Example: creating a temporary RE object: pcrecpp::RE("h.*o").FullMatch("hello"); - You can pass in a "const char*" or a "string" for "text". The examples - below tend to use a const char*. You can, as in the different examples - above, store the RE object explicitly in a variable or use a temporary - RE object. The examples below use one mode or the other arbitrarily. + You can pass in a "const char*" or a "string" for "text". The examples + below tend to use a const char*. You can, as in the different examples + above, store the RE object explicitly in a variable or use a temporary + RE object. The examples below use one mode or the other arbitrarily. Either could correctly be used for any of these examples. You must supply extra pointer arguments to extract matched subpieces. @@ -8550,7 +9779,7 @@ MATCHING INTERFACE Example: fails because string cannot be stored in integer !pcrecpp::RE("(.*)").FullMatch("ruby", &i); - The provided pointer arguments can be pointers to any scalar numeric + The provided pointer arguments can be pointers to any scalar numeric type, or one of: string (matched piece is copied to string) @@ -8558,7 +9787,7 @@ MATCHING INTERFACE T (where "bool T::ParseFrom(const char*, int)" exists) NULL (the corresponding matched sub-pattern is not copied) - The function returns true iff all of the following conditions are sat- + The function returns true iff all of the following conditions are sat- isfied: a. "text" matches "pattern" exactly; @@ -8573,41 +9802,41 @@ MATCHING INTERFACE number of sub-patterns, "i"th captured sub-pattern is ignored. - CAVEAT: An optional sub-pattern that does not exist in the matched - string is assigned the empty string. Therefore, the following will + CAVEAT: An optional sub-pattern that does not exist in the matched + string is assigned the empty string. Therefore, the following will return false (because the empty string is not a valid number): int number; pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number); - The matching interface supports at most 16 arguments per call. If you - need more, consider using the more general interface + The matching interface supports at most 16 arguments per call. If you + need more, consider using the more general interface pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch. - NOTE: Do not use no_arg, which is used internally to mark the end of a - list of optional arguments, as a placeholder for missing arguments, as + NOTE: Do not use no_arg, which is used internally to mark the end of a + list of optional arguments, as a placeholder for missing arguments, as this can lead to segfaults. QUOTING METACHARACTERS - You can use the "QuoteMeta" operation to insert backslashes before all - potentially meaningful characters in a string. The returned string, + You can use the "QuoteMeta" operation to insert backslashes before all + potentially meaningful characters in a string. The returned string, used as a regular expression, will exactly match the original string. Example: string quoted = RE::QuoteMeta(unquoted); - Note that it's legal to escape a character even if it has no special - meaning in a regular expression -- so this function does that. (This - also makes it identical to the perl function of the same name; see - "perldoc -f quotemeta".) For example, "1.5-2.0?" becomes + Note that it's legal to escape a character even if it has no special + meaning in a regular expression -- so this function does that. (This + also makes it identical to the perl function of the same name; see + "perldoc -f quotemeta".) For example, "1.5-2.0?" becomes "1\.5\-2\.0\?". PARTIAL MATCHES - You can use the "PartialMatch" operation when you want the pattern to + You can use the "PartialMatch" operation when you want the pattern to match any substring of the text. Example: simple search for a string: @@ -8622,13 +9851,13 @@ PARTIAL MATCHES UTF-8 AND THE MATCHING INTERFACE - By default, pattern and text are plain text, one byte per character. - The UTF8 flag, passed to the constructor, causes both pattern and + By default, pattern and text are plain text, one byte per character. + The UTF8 flag, passed to the constructor, causes both pattern and string to be treated as UTF-8 text, still a byte stream but potentially - multiple bytes per character. In practice, the text is likelier to be - UTF-8 than the pattern, but the match returned may depend on the UTF8 - flag, so always use it when matching UTF8 text. For example, "." will - match one byte normally but with UTF8 set may match up to three bytes + multiple bytes per character. In practice, the text is likelier to be + UTF-8 than the pattern, but the match returned may depend on the UTF8 + flag, so always use it when matching UTF8 text. For example, "." will + match one byte normally but with UTF8 set may match up to three bytes of a multi-byte character. Example: @@ -8647,9 +9876,9 @@ UTF-8 AND THE MATCHING INTERFACE PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE - PCRE defines some modifiers to change the behavior of the regular - expression engine. The C++ wrapper defines an auxiliary class, - RE_Options, as a vehicle to pass such modifiers to a RE class. Cur- + PCRE defines some modifiers to change the behavior of the regular + expression engine. The C++ wrapper defines an auxiliary class, + RE_Options, as a vehicle to pass such modifiers to a RE class. Cur- rently, the following modifiers are supported: modifier description Perl corresponding @@ -8664,15 +9893,15 @@ PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE PCRE_UNGREEDY reverses * and *? N/A PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*) - (*) Both Perl and PCRE allow non capturing parentheses by means of the - "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not cap- + (*) Both Perl and PCRE allow non capturing parentheses by means of the + "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not cap- ture, while (ab|cd) does. - For a full account on how each modifier works, please check the PCRE + For a full account on how each modifier works, please check the PCRE API reference page. - For each modifier, there are two member functions whose name is made - out of the modifier in lowercase, without the "PCRE_" prefix. For + For each modifier, there are two member functions whose name is made + out of the modifier in lowercase, without the "PCRE_" prefix. For instance, PCRE_CASELESS is handled by bool caseless() @@ -8682,18 +9911,18 @@ PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE RE_Options & set_caseless(bool) which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can - be accessed through the set_match_limit() and match_limit() member - functions. Setting match_limit to a non-zero value will limit the exe- - cution of pcre to keep it from doing bad things like blowing the stack - or taking an eternity to return a result. A value of 5000 is good - enough to stop stack blowup in a 2MB thread stack. Setting match_limit - to zero disables match limiting. Alternatively, you can call - match_limit_recursion() which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to - limit how much PCRE recurses. match_limit() limits the number of + be accessed through the set_match_limit() and match_limit() member + functions. Setting match_limit to a non-zero value will limit the exe- + cution of pcre to keep it from doing bad things like blowing the stack + or taking an eternity to return a result. A value of 5000 is good + enough to stop stack blowup in a 2MB thread stack. Setting match_limit + to zero disables match limiting. Alternatively, you can call + match_limit_recursion() which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to + limit how much PCRE recurses. match_limit() limits the number of matches PCRE does; match_limit_recursion() limits the depth of internal recursion, and therefore the amount of stack that is used. - Normally, to pass one or more modifiers to a RE class, you declare a + Normally, to pass one or more modifiers to a RE class, you declare a RE_Options object, set the appropriate options, and pass this object to a RE constructor. Example: @@ -8702,8 +9931,8 @@ PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE if (RE("HELLO", opt).PartialMatch("hello world")) ... RE_options has two constructors. The default constructor takes no argu- - ments and creates a set of flags that are off by default. The optional - parameter option_flags is to facilitate transfer of legacy code from C + ments and creates a set of flags that are off by default. The optional + parameter option_flags is to facilitate transfer of legacy code from C programs. This lets you do RE(pattern, @@ -8717,15 +9946,15 @@ PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE If you are going to pass one of the most used modifiers, there are some convenience functions that return a RE_Options class with the appropri- - ate modifier already set: CASELESS(), UTF8(), MULTILINE(), DOTALL(), + ate modifier already set: CASELESS(), UTF8(), MULTILINE(), DOTALL(), and EXTENDED(). - If you need to set several options at once, and you don't want to go - through the pains of declaring a RE_Options object and setting several - options, there is a parallel method that give you such ability on the - fly. You can concatenate several set_xxxxx() member functions, since - each of them returns a reference to its class object. For example, to - pass PCRE_CASELESS, PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one + If you need to set several options at once, and you don't want to go + through the pains of declaring a RE_Options object and setting several + options, there is a parallel method that give you such ability on the + fly. You can concatenate several set_xxxxx() member functions, since + each of them returns a reference to its class object. For example, to + pass PCRE_CASELESS, PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write: RE(" ^ xyz \\s+ .* blah$", @@ -8737,10 +9966,10 @@ PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE SCANNING TEXT INCREMENTALLY - The "Consume" operation may be useful if you want to repeatedly match + The "Consume" operation may be useful if you want to repeatedly match regular expressions at the front of a string and skip over them as they - match. This requires use of the "StringPiece" type, which represents a - sub-range of a real string. Like RE, StringPiece is defined in the + match. This requires use of the "StringPiece" type, which represents a + sub-range of a real string. Like RE, StringPiece is defined in the pcrecpp namespace. Example: read lines of the form "var = value" from a string. @@ -8754,11 +9983,11 @@ SCANNING TEXT INCREMENTALLY ...; } - Each successful call to "Consume" will set "var/value", and also + Each successful call to "Consume" will set "var/value", and also advance "input" so it points past the matched text. - The "FindAndConsume" operation is similar to "Consume" but does not - anchor your match at the beginning of the string. For example, you + The "FindAndConsume" operation is similar to "Consume" but does not + anchor your match at the beginning of the string. For example, you could extract all words from a string by repeatedly calling pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word) @@ -8767,10 +9996,10 @@ SCANNING TEXT INCREMENTALLY PARSING HEX/OCTAL/C-RADIX NUMBERS By default, if you pass a pointer to a numeric value, the corresponding - text is interpreted as a base-10 number. You can instead wrap the + text is interpreted as a base-10 number. You can instead wrap the pointer with a call to one of the operators Hex(), Octal(), or CRadix() - to interpret the text in another base. The CRadix operator interprets - C-style "0" (base-8) and "0x" (base-16) prefixes, but defaults to + to interpret the text in another base. The CRadix operator interprets + C-style "0" (base-8) and "0x" (base-16) prefixes, but defaults to base-10. Example: @@ -8785,30 +10014,30 @@ PARSING HEX/OCTAL/C-RADIX NUMBERS REPLACING PARTS OF STRINGS - You can replace the first match of "pattern" in "str" with "rewrite". - Within "rewrite", backslash-escaped digits (\1 to \9) can be used to - insert text matching corresponding parenthesized group from the pat- + You can replace the first match of "pattern" in "str" with "rewrite". + Within "rewrite", backslash-escaped digits (\1 to \9) can be used to + insert text matching corresponding parenthesized group from the pat- tern. \0 in "rewrite" refers to the entire matching text. For example: string s = "yabba dabba doo"; pcrecpp::RE("b+").Replace("d", &s); - will leave "s" containing "yada dabba doo". The result is true if the + will leave "s" containing "yada dabba doo". The result is true if the pattern matches and a replacement occurs, false otherwise. - GlobalReplace is like Replace except that it replaces all occurrences - of the pattern in the string with the rewrite. Replacements are not + GlobalReplace is like Replace except that it replaces all occurrences + of the pattern in the string with the rewrite. Replacements are not subject to re-matching. For example: string s = "yabba dabba doo"; pcrecpp::RE("b+").GlobalReplace("d", &s); - will leave "s" containing "yada dada doo". It returns the number of + will leave "s" containing "yada dada doo". It returns the number of replacements made. - Extract is like Replace, except that if the pattern matches, "rewrite" - is copied into "out" (an additional argument) with substitutions. The - non-matching portions of "text" are ignored. Returns true iff a match + Extract is like Replace, except that if the pattern matches, "rewrite" + is copied into "out" (an additional argument) with substitutions. The + non-matching portions of "text" are ignored. Returns true iff a match occurred and the extraction happened successfully; if no match occurs, the string is left unaffected. @@ -8825,13 +10054,13 @@ REVISION ------------------------------------------------------------------------------ -PCRESAMPLE(3) PCRESAMPLE(3) +PCRESAMPLE(3) Library Functions Manual PCRESAMPLE(3) + NAME PCRE - Perl-compatible regular expressions - PCRE SAMPLE PROGRAM A simple, complete demonstration program, to get you started with using @@ -8911,13 +10140,13 @@ REVISION Last updated: 10 January 2012 Copyright (c) 1997-2012 University of Cambridge. ------------------------------------------------------------------------------ -PCRELIMITS(3) PCRELIMITS(3) +PCRELIMITS(3) Library Functions Manual PCRELIMITS(3) + NAME PCRE - Perl-compatible regular expressions - SIZE AND OTHER LIMITATIONS There are some size limitations in PCRE but it is hoped that they will @@ -8925,18 +10154,24 @@ SIZE AND OTHER LIMITATIONS The maximum length of a compiled pattern is approximately 64K data units (bytes for the 8-bit library, 16-bit units for the 16-bit - library) if PCRE is compiled with the default internal linkage size of - 2 bytes. If you want to process regular expressions that are truly - enormous, you can compile PCRE with an internal linkage size of 3 or 4 - (when building the 16-bit library, 3 is rounded up to 4). See the - README file in the source distribution and the pcrebuild documentation - for details. In these cases the limit is substantially larger. How- - ever, the speed of execution is slower. + library, and 32-bit units for the 32-bit library) if PCRE is compiled + with the default internal linkage size, which is 2 bytes for the 8-bit + and 16-bit libraries, and 4 bytes for the 32-bit library. If you want + to process regular expressions that are truly enormous, you can compile + PCRE with an internal linkage size of 3 or 4 (when building the 16-bit + or 32-bit library, 3 is rounded up to 4). See the README file in the + source distribution and the pcrebuild documentation for details. In + these cases the limit is substantially larger. However, the speed of + execution is slower. All values in repeating quantifiers must be less than 65536. There is no limit to the number of parenthesized subpatterns, but there - can be no more than 65535 capturing subpatterns. + can be no more than 65535 capturing subpatterns. There is, however, a + limit to the depth of nesting of parenthesized subpatterns of all + kinds. This is imposed in order to limit the amount of system stack + used at compile time. The limit can be specified when PCRE is built; + the default is 250. There is a limit to the number of forward references to subsequent sub- patterns of around 200,000. Repeated forward references with fixed @@ -8948,8 +10183,8 @@ SIZE AND OTHER LIMITATIONS the maximum number of named subpatterns is 10000. The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or - (*THEN) verb is 255 for the 8-bit library and 65535 for the 16-bit - library. + (*THEN) verb is 255 for the 8-bit library and 65535 for the 16-bit and + 32-bit libraries. The maximum length of a subject string is the largest positive number that an integer variable can hold. However, when using the traditional @@ -8968,21 +10203,21 @@ AUTHOR REVISION - Last updated: 04 May 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 05 November 2013 + Copyright (c) 1997-2013 University of Cambridge. ------------------------------------------------------------------------------ -PCRESTACK(3) PCRESTACK(3) +PCRESTACK(3) Library Functions Manual PCRESTACK(3) + NAME PCRE - Perl-compatible regular expressions - PCRE DISCUSSION OF STACK USAGE - When you call pcre[16]_exec(), it makes use of an internal function + When you call pcre[16|32]_exec(), it makes use of an internal function called match(). This calls itself recursively at branch points in the pattern, in order to remember the state of the match so that it can back up and try a different alternative if the first one fails. As @@ -8998,110 +10233,111 @@ PCRE DISCUSSION OF STACK USAGE result of the current call (a "tail recursion"), the function is just restarted instead. - The above comments apply when pcre[16]_exec() is run in its normal + The above comments apply when pcre[16|32]_exec() is run in its normal interpretive manner. If the pattern was studied with the PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling was success- - ful, and the options passed to pcre[16]_exec() were not incompatible, - the matching process uses the JIT-compiled code instead of the match() - function. In this case, the memory requirements are handled entirely - differently. See the pcrejit documentation for details. + ful, and the options passed to pcre[16|32]_exec() were not incompati- + ble, the matching process uses the JIT-compiled code instead of the + match() function. In this case, the memory requirements are handled + entirely differently. See the pcrejit documentation for details. - The pcre[16]_dfa_exec() function operates in an entirely different way, - and uses recursion only when there is a regular expression recursion or - subroutine call in the pattern. This includes the processing of asser- - tion and "once-only" subpatterns, which are handled like subroutine - calls. Normally, these are never very deep, and the limit on the com- - plexity of pcre[16]_dfa_exec() is controlled by the amount of workspace - it is given. However, it is possible to write patterns with runaway - infinite recursions; such patterns will cause pcre[16]_dfa_exec() to - run out of stack. At present, there is no protection against this. + The pcre[16|32]_dfa_exec() function operates in an entirely different + way, and uses recursion only when there is a regular expression recur- + sion or subroutine call in the pattern. This includes the processing of + assertion and "once-only" subpatterns, which are handled like subrou- + tine calls. Normally, these are never very deep, and the limit on the + complexity of pcre[16|32]_dfa_exec() is controlled by the amount of + workspace it is given. However, it is possible to write patterns with + runaway infinite recursions; such patterns will cause + pcre[16|32]_dfa_exec() to run out of stack. At present, there is no + protection against this. - The comments that follow do NOT apply to pcre[16]_dfa_exec(); they are - relevant only for pcre[16]_exec() without the JIT optimization. + The comments that follow do NOT apply to pcre[16|32]_dfa_exec(); they + are relevant only for pcre[16|32]_exec() without the JIT optimization. - Reducing pcre[16]_exec()'s stack usage + Reducing pcre[16|32]_exec()'s stack usage - Each time that match() is actually called recursively, it uses memory - from the process stack. For certain kinds of pattern and data, very - large amounts of stack may be needed, despite the recognition of "tail - recursion". You can often reduce the amount of recursion, and there- - fore the amount of stack used, by modifying the pattern that is being + Each time that match() is actually called recursively, it uses memory + from the process stack. For certain kinds of pattern and data, very + large amounts of stack may be needed, despite the recognition of "tail + recursion". You can often reduce the amount of recursion, and there- + fore the amount of stack used, by modifying the pattern that is being matched. Consider, for example, this pattern: ([^<]|<(?!inet))+ - It matches from wherever it starts until it encounters "