--- embedaddon/pcre/doc/pcre.txt 2012/02/21 23:50:25 1.1.1.2 +++ embedaddon/pcre/doc/pcre.txt 2013/07/22 08:25:56 1.1.1.4 @@ -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 6.2.0. 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 @@ -367,12 +412,14 @@ OPTION NAMES There are two new general option names, PCRE_UTF16 and PCRE_NO_UTF16_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. + define the same bits in the options word. There is a discussion about + the validity of UTF-16 strings in the pcreunicode page. - 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. + 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 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 @@ -413,7 +460,7 @@ ERROR NAMES 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 @@ -436,12 +483,14 @@ TESTING 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. + 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. + 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 16-BIT MODE @@ -460,73 +509,423 @@ AUTHOR REVISION - Last updated: 08 January 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 char **errptr, int *erroffset, + 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 @@ -546,48 +945,49 @@ 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 runtime - option). It is not possible to support both EBCDIC and UTF-8 codes in - the same version of the library. Consequently, --enable-utf and + 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 --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. @@ -597,9 +997,9 @@ 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 @@ -610,14 +1010,14 @@ 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 @@ -629,40 +1029,40 @@ 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 @@ -672,115 +1072,132 @@ 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 runtime 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 + 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 @@ -842,9 +1259,77 @@ 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 @@ -856,32 +1341,34 @@ 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 @@ -1010,10 +1497,10 @@ THE ALTERNATIVE MATCHING ALGORITHM 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. + 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 @@ -1068,9 +1555,10 @@ REVISION ------------------------------------------------------------------------------ -PCREAPI(3) PCREAPI(3) +PCREAPI(3) Library Functions Manual PCREAPI(3) + NAME PCRE - Perl-compatible regular expressions @@ -1139,6 +1627,11 @@ 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); @@ -1174,70 +1667,76 @@ 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 @@ -1310,7 +1809,7 @@ NEWLINES feed) character, the two-character sequence CRLF, any of the three pre- ceding, or any Unicode newline sequence. The Unicode newline sequences are the three just mentioned, plus the single characters VT (vertical - tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line + tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS (paragraph separator, U+2029). Each of the first three conventions is used by at least one operating @@ -1383,21 +1882,30 @@ 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 @@ -1407,39 +1915,42 @@ 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 @@ -1511,23 +2022,25 @@ COMPILING A PATTERN 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_OPT options can be set at the time of matching as well as - at compile time. + 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 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 + 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 - string, the offset is that of the first byte of the failing character. + 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. + 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 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 @@ -1624,8 +2137,8 @@ COMPILING A PATTERN PCRE_EXTENDED - If this bit is set, whitespace data characters in the pattern are - totally ignored except when escaped or inside a character class. White- + 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 @@ -1641,7 +2154,7 @@ COMPILING A PATTERN This option makes it possible to include comments inside complicated patterns. Note, however, that this applies only to data characters. - Whitespace characters may never appear within special character + White space characters may never appear within special character sequences in a pattern, for example within the sequence (?( that intro- duces a conditional subpattern. @@ -1697,21 +2210,33 @@ COMPILING A PATTERN 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 - newlines in the subject string, respectively, as well as at the very - start and end. This is equivalent to Perl's /m option, and it can be + When PCRE_MULTILINE it is set, the "start of line" and "end of line" + constructs match immediately following or immediately before internal + newlines in the subject string, respectively, as well as at the very + start and end. This is equivalent to Perl's /m option, and it can be changed within a pattern by a (?m) option setting. If there are no new- - lines in a subject string, or no occurrences of ^ or $ in 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 @@ -1725,25 +2250,34 @@ COMPILING A PATTERN 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 (formfeed, - 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. + recognized. - The newline setting in the options word uses three bits that are + 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 - more than one newline option, the combination may or may not be sensi- + used (default plus the five values above). This means that if you set + more than one newline option, the combination may or may not be sensi- ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to - PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers and + PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers and cause an error. - The only time that a line break in a pattern is specially recognized - when compiling is when PCRE_EXTENDED is set. CR and LF are whitespace - characters, and so are ignored in this mode. Also, an unescaped # out- - side a character class indicates a comment that lasts until after the - next line break sequence. In other circumstances, line break sequences + The only time that a line break in a pattern is specially recognized + when compiling is when PCRE_EXTENDED is set. CR and LF are white space + characters, and so are ignored in this mode. Also, an unescaped # out- + side a character class indicates a comment that lasts until after the + next line break sequence. In other circumstances, line break sequences in patterns are treated as literal data. The newline option that is set at compile time becomes the default that @@ -1752,18 +2286,19 @@ COMPILING A PATTERN PCRE_NO_AUTO_CAPTURE If this option is set, it disables the use of numbered capturing paren- - theses in the pattern. Any opening parenthesis that is not followed by - ? behaves as if it were followed by ?: but named parentheses can still - be used for capturing (and they acquire numbers in the usual way). + theses in the pattern. Any opening parenthesis that is not followed by + ? behaves as if it were followed by ?: but named parentheses can still + 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_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. + 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. 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 @@ -1802,7 +2337,9 @@ COMPILING A PATTERN 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. + 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 @@ -1810,9 +2347,9 @@ 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. + 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 @@ -1876,7 +2413,7 @@ 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 (?+ @@ -1893,6 +2430,9 @@ COMPILATION ERROR CODES 72 too many forward references 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff) 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) 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. @@ -1917,17 +2457,27 @@ STUDYING A PATTERN 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. + 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 is only - one option: PCRE_STUDY_JIT_COMPILE. If this is 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() matching - function. If the just-in-time compiler is not available, this option is - ignored. All other bits in the options argument must be zero. + 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 + 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 @@ -1947,8 +2497,8 @@ STUDYING A PATTERN 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 PCRE_STUDY_JIT_COMPILE is not used, but it is - advisable to change to the new function when convenient. + 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 real application there should be tests for errors): @@ -1970,28 +2520,34 @@ 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 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(). - However, they are not used by pcre_exec() if pcre_study() is called - with the PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling is - successful. The optimizations can be disabled by setting the - PCRE_NO_START_OPTIMIZE option when calling pcre_exec() or - pcre_dfa_exec(). You might want to do this if your pattern contains - callouts or (*MARK) (which cannot be handled by the JIT compiler), and - you want to make use of these facilities in cases where matching fails. - See the discussion of PCRE_NO_START_OPTIMIZE below. + 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. + 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 @@ -2072,6 +2628,7 @@ 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- @@ -2118,21 +2675,27 @@ INFORMATION ABOUT A PATTERN 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. + 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 - (a) the pattern was compiled with the PCRE_MULTILINE option, and every + (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), - -1 is returned, indicating that the pattern matches only at the start - of a subject string or after any newline within the string. Otherwise + -1 is returned, indicating that the pattern matches only at the start + 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 @@ -2156,19 +2719,19 @@ INFORMATION ABOUT A PATTERN PCRE_INFO_JIT - Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE - option, 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 the PCRE_STUDY_JIT_COMPILE option, or that the JIT - compiler could not handle this particular pattern. See the pcrejit doc- - umentation for details of what can and cannot be handled. + 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 + and cannot be handled. PCRE_INFO_JITSIZE - If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE - option, return the size of the JIT compiled code, otherwise return - zero. The fourth argument should point to a size_t variable. + 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 @@ -2180,61 +2743,88 @@ INFORMATION ABOUT A PATTERN 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 the character, this value + is deprecated; instead the PCRE_INFO_REQUIREDCHARFLAGS and + PCRE_INFO_REQUIREDCHAR values should be used. + + 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 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 - 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 + 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 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 least that long. PCRE_INFO_NAMECOUNT PCRE_INFO_NAMEENTRYSIZE PCRE_INFO_NAMETABLE - PCRE supports the use of named as well as numbered capturing parenthe- - ses. The names are just an additional way of identifying the parenthe- + PCRE supports the use of named as well as numbered capturing parenthe- + ses. The names are just an additional way of identifying the parenthe- ses, which still acquire numbers. Several convenience functions such as - pcre_get_named_substring() are provided for extracting captured sub- - strings by name. It is also possible to extract the data directly, by - first converting the name to a number in order to access the correct + pcre_get_named_substring() are provided for extracting captured sub- + strings by name. It is also possible to extract the data directly, by + first converting the name to a number in order to access the correct pointers in the output vector (described with pcre_exec() below). To do - the conversion, you need to use the name-to-number map, which is + the conversion, you need to use the name-to-number map, which is described by these three values. The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size - of each entry; both of these return an int value. The entry size - depends on the length of the longest name. PCRE_INFO_NAMETABLE returns + of each entry; both of these return an int value. The entry size + depends on the length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first entry of the table. This is a pointer to char in 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. + 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. 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 (?| + 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; + 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. - 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 ??: @@ -2243,31 +2833,31 @@ 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 @@ -2279,30 +2869,103 @@ 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, if PCRE_INFO_FIRSTCHARACTER- + FLAGS returned 1; otherwise returns 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. + + 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), + + -1 is returned, indicating that the pattern matches only at the start + of a subject string or after any newline within the string. Otherwise + -2 is returned. For anchored patterns, -2 is returned. + + 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); @@ -2383,50 +3046,62 @@ 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 a bitmap that specifies which of the other fields - are set. The flag bits are: + In the 32-bit version of this structure, the mark field has type + "PCRE_UCHAR32 **". - PCRE_EXTRA_STUDY_DATA + The flags field is used to specify which of the other fields are set. + The flag bits are: + + PCRE_EXTRA_CALLOUT_DATA PCRE_EXTRA_EXECUTABLE_JIT + PCRE_EXTRA_MARK PCRE_EXTRA_MATCH_LIMIT PCRE_EXTRA_MATCH_LIMIT_RECURSION - PCRE_EXTRA_CALLOUT_DATA + PCRE_EXTRA_STUDY_DATA PCRE_EXTRA_TABLES - PCRE_EXTRA_MARK - 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 - the other fields and their corresponding flag bits. + 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 the PCRE_STUDY_JIT_COMPILE 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 matching can continue. + 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 @@ -2436,8 +3111,8 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION Limiting the recursion depth limits the amount of machine stack that can be used, or, when PCRE has been compiled to use memory on the heap instead of the stack, the amount of heap memory that can be used. This - limit is not relevant, and is ignored, if the pattern was successfully - studied with PCRE_STUDY_JIT_COMPILE. + limit is not relevant, and is ignored, when matching is done using JIT + compiled code. The default value for match_limit_recursion can be set when PCRE is built; the default default is the same value as the default for @@ -2446,60 +3121,69 @@ 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- + 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- + 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. - 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, + 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_SOFT, and - PCRE_PARTIAL_HARD. + 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 the PCRE_STUDY_JIT_COMPILE - option, the only supported options for JIT execution are - PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and - PCRE_NOTEMPTY_ATSTART. Note in particular that partial matching is not - supported. If an unsupported option is used, JIT execution is disabled - and the normal interpretive code in pcre_exec() is run. + 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 + 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 @@ -2508,107 +3192,110 @@ 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. + 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 @@ -2642,66 +3329,72 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8 string is automatically checked when pcre_exec() is subsequently - called. The value of startoffset is also checked to ensure that it - points to the start of a UTF-8 character. There is a discussion about - the validity of UTF-8 strings in the pcreunicode page. If an invalid - sequence of bytes is found, pcre_exec() returns the error + called. The entire string is checked before any other processing takes + place. The value of startoffset is also checked to ensure that it + points to the start of a UTF-8 character. There is a discussion about + the validity of UTF-8 strings in the pcreunicode page. If an invalid + sequence of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In - both cases, information about the precise nature of the error may also - be returned (see the descriptions of these errors in the section enti- - tled Error return values from pcre_exec() below). If startoffset con- + both cases, information about the precise nature of the error may also + be returned (see the descriptions of these errors in the section enti- + tled Error return values from pcre_exec() below). If startoffset con- tains a value that does not point to the start of a UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned. - If you already know that your subject is valid, and you want to skip - these checks for performance reasons, you can set the - PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might want to - do this for the second and subsequent calls to pcre_exec() if you are - making repeated calls to find all the matches in a single subject - string. However, you should be sure that the value of startoffset - points to the start of a character (or the end of the subject). When + If you already know that your subject is valid, and you want to skip + these checks for performance reasons, you can set the + PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might want to + do this for the second and subsequent calls to pcre_exec() if you are + making repeated calls to find all the matches in a single subject + string. However, you should be sure that the value of startoffset + 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 + subject or an invalid value of startoffset is undefined. Your program may crash. PCRE_PARTIAL_HARD PCRE_PARTIAL_SOFT - These options turn on the partial matching feature. For backwards com- - patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial - match occurs if the end of the subject string is reached successfully, - but there are not enough subject characters to complete the match. If + These options turn on the partial matching feature. For backwards com- + patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial + match occurs if the end of the subject string is reached successfully, + but there are not enough subject characters to complete the match. If this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, - matching continues by testing any remaining alternatives. Only if no - complete match can be found is PCRE_ERROR_PARTIAL returned instead of - PCRE_ERROR_NOMATCH. In other words, PCRE_PARTIAL_SOFT says that the - caller is prepared to handle a partial match, but only if no complete + matching continues by testing any remaining alternatives. Only if no + complete match can be found is PCRE_ERROR_PARTIAL returned instead of + PCRE_ERROR_NOMATCH. In other words, PCRE_PARTIAL_SOFT says that the + caller is prepared to handle a partial match, but only if no complete match can be found. - If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this - case, if a partial match is found, pcre_exec() immediately returns - PCRE_ERROR_PARTIAL, without considering any other alternatives. In - other words, when PCRE_PARTIAL_HARD is set, a partial match is consid- + If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this + case, if a partial match is found, pcre_exec() immediately returns + PCRE_ERROR_PARTIAL, without considering any other alternatives. In + other words, when PCRE_PARTIAL_HARD is set, a partial match is consid- ered to be more important that an alternative complete match. - In both cases, the portion of the string that was inspected when the + In both cases, the portion of the string that was inspected when the partial match was found is set as the first matching string. There is a - more detailed discussion of partial and multi-segment matching, with + more detailed discussion of partial and multi-segment matching, with examples, in the pcrepartial documentation. 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, - 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. + The subject string is passed to pcre_exec() as a pointer in subject, a + 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 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 @@ -2762,10 +3455,12 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION 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. + 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 @@ -2782,7 +3477,7 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION 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 - not any captured substrings are of interest, pcre_exec() may be called + 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 @@ -2973,34 +3668,49 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_ERROR_JIT_STACKLIMIT (-27) This error is returned when a pattern that was successfully studied - using the PCRE_STUDY_JIT_COMPILE option is being matched, but the mem- - ory available for the just-in-time processing stack is not large - enough. See the pcrejit documentation for more details. + 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) + 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) + 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 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 and -22 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. + 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 - offset of the start of the invalid UTF-8 character is placed in the + UTF8, and the size of the output vector (ovecsize) is at least 2, the + offset of the start of the invalid UTF-8 character is placed in the first output vector element (ovector[0]) and a reason code is placed in - the second element (ovector[1]). The reason codes are given names in + the second element (ovector[1]). The reason codes are given names in the pcre.h header file: PCRE_UTF8_ERR1 @@ -3009,10 +3719,10 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_UTF8_ERR4 PCRE_UTF8_ERR5 - The string ends with a truncated UTF-8 character; the code specifies - how many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 - characters to be no longer than 4 bytes, the encoding scheme (origi- - nally defined by RFC 2279) allows for up to 6 bytes, and this is + The string ends with a truncated UTF-8 character; the code specifies + how many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 + characters to be no longer than 4 bytes, the encoding scheme (origi- + nally defined by RFC 2279) allows for up to 6 bytes, and this is checked first; hence the possibility of 4 or 5 missing bytes. PCRE_UTF8_ERR6 @@ -3022,24 +3732,24 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_UTF8_ERR10 The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of - the character do not have the binary value 0b10 (that is, either the + the character do not have the binary value 0b10 (that is, either the most significant bit is 0, or the next bit is 1). PCRE_UTF8_ERR11 PCRE_UTF8_ERR12 - A character that is valid by the RFC 2279 rules is either 5 or 6 bytes + A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long; these code points are excluded by RFC 3629. PCRE_UTF8_ERR13 - A 4-byte character has a value greater than 0x10fff; these code points + A 4-byte character has a value greater than 0x10fff; these code points are excluded by RFC 3629. PCRE_UTF8_ERR14 - A 3-byte character has a value in the range 0xd800 to 0xdfff; this - range of code points are reserved by RFC 3629 for use with UTF-16, and + A 3-byte character has a value in the range 0xd800 to 0xdfff; this + range of code points are reserved by RFC 3629 for use with UTF-16, and so are excluded from UTF-8. PCRE_UTF8_ERR15 @@ -3048,24 +3758,31 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE_UTF8_ERR18 PCRE_UTF8_ERR19 - A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes - for a value that can be represented by fewer bytes, which is invalid. - For example, the two bytes 0xc0, 0xae give the value 0x2e, whose cor- + A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes + for a value that can be represented by fewer bytes, which is invalid. + For example, the two bytes 0xc0, 0xae give the value 0x2e, whose cor- rect coding uses just one byte. PCRE_UTF8_ERR20 The two most significant bits of the first byte of a character have the - binary value 0b10 (that is, the most significant bit is 1 and the sec- - ond is 0). Such a byte can only validly occur as the second or subse- + binary value 0b10 (that is, the most significant bit is 1 and the sec- + ond is 0). Such a byte can only validly occur as the second or subse- quent byte of a multi-byte character. PCRE_UTF8_ERR21 - The first byte of a character has the value 0xfe or 0xff. These values + 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, @@ -3452,12 +4169,19 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION This error is given if the output vector is not large enough. This should be extremely rare, as a vector of size 1000 is used. + PCRE_ERROR_DFA_BADRESTART (-30) + When pcre_dfa_exec() is called with the PCRE_DFA_RESTART option, some + plausibility checks are made on the contents of the workspace, which + should contain data about the previous partial match. If any of these + checks fail, this error is given. + + 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 @@ -3469,30 +4193,37 @@ AUTHOR REVISION - Last updated: 21 January 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 12 May 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 @@ -3514,17 +4245,23 @@ 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 command has an option that sets automatic call- + outs; when it is used, the output indicates how the pattern is matched. + This is useful information when you are trying to optimize the perfor- + mance of a particular pattern. + + MISSING CALLOUTS You should be aware that, because of optimizations in the way PCRE @@ -3552,16 +4289,18 @@ MISSING CALLOUTS 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: + 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; @@ -3572,52 +4311,56 @@ 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 - version number will change again in future if additional fields are + 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 + version number will change again in future if additional fields are added, but the intention is never to remove any of the existing fields. - The callout_number field contains the number of the callout, as com- - piled into the pattern (that is, the number after ?C for manual call- + The callout_number field contains the number of the callout, as com- + piled into the pattern (that is, the number after ?C for manual call- outs, and 255 for automatically generated callouts). - 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 - extract substrings that have been matched so far, in the same way as - for extracting substrings after a match has completed. For the DFA + 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 + 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. The subject and subject_length fields contain copies of the values that were passed to the matching function. - The start_match field normally contains the offset within the subject - at which the current match attempt started. However, if the escape - sequence \K has been encountered, this value is changed to reflect the - modified starting point. If the pattern is not anchored, the callout + The start_match field normally contains the offset within the subject + at which the current match attempt started. However, if the escape + sequence \K has been encountered, this value is changed to reflect the + modified starting point. If the pattern is not anchored, the callout function may be called several times from the same point in the pattern for different starting points in the subject. - The current_position field contains the offset within the subject of + 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. + The capture_last field contains the number of the most recently cap- + 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. + 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 structure. It contains the offset to the next item to be matched in the @@ -3635,12 +4378,12 @@ THE CALLOUT INTERFACE 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. + 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 @@ -3668,18 +4411,18 @@ AUTHOR REVISION - Last updated: 08 Janurary 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 03 March 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 @@ -3698,10 +4441,8 @@ 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- @@ -3727,15 +4468,10 @@ 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 @@ -3745,48 +4481,69 @@ 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 (*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. + 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)|(?\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 and POSIX character classes to use Unicode + properties. PCRE uses these non-standard, non-Perl properties inter- + nally when PCRE_UCP is set. However, 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, - formfeed, or carriage return, and any other character that has the Z + 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. + 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 @@ -4543,76 +5405,81 @@ 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 @@ -4673,15 +5540,17 @@ 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 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- @@ -4732,7 +5601,7 @@ SQUARE BRACKETS AND CHARACTER CLASSES 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 + 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. @@ -4940,10 +5809,13 @@ 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 @@ -4955,18 +5827,18 @@ 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)) @@ -4974,12 +5846,12 @@ 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)) @@ -4987,37 +5859,37 @@ 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. @@ -5025,58 +5897,58 @@ 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 + 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. - 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: @@ -5086,38 +5958,38 @@ 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- + 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. + 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. Warning: You cannot use different names to distinguish between two sub- - patterns with the same number because PCRE uses only the numbers when + 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 + 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. REPETITION - Repetition is specified by quantifiers, which can follow any of the + Repetition is specified by quantifiers, which can follow any of the following items: a literal data character @@ -5131,17 +6003,17 @@ REPETITION a parenthesized subpattern (including assertions) a subroutine call to a subpattern (recursive or otherwise) - The general repetition quantifier specifies a minimum and maximum num- - ber of permitted matches, by giving the two numbers in curly brackets - (braces), separated by a comma. The numbers must be less than 65536, + The general repetition quantifier specifies a minimum and maximum num- + ber of permitted matches, by giving the two numbers in curly brackets + (braces), separated by a comma. The numbers must be less than 65536, and the first must be less than or equal to the second. For example: z{2,4} - matches "zz", "zzz", or "zzzz". A closing brace on its own is not a - special character. If the second number is omitted, but the comma is - present, there is no upper limit; if the second number and the comma - are both omitted, the quantifier specifies an exact number of required + matches "zz", "zzz", or "zzzz". A closing brace on its own is not a + special character. If the second number is omitted, but the comma is + present, there is no upper limit; if the second number and the comma + are both omitted, the quantifier specifies an exact number of required matches. Thus [aeiou]{3,} @@ -5150,16 +6022,17 @@ REPETITION \d{8} - matches exactly 8 digits. An opening curly bracket that appears in a - position where a quantifier is not allowed, or one that does not match - the syntax of a quantifier, is taken as a literal character. For exam- + matches exactly 8 digits. An opening curly bracket that appears in a + position where a quantifier is not allowed, or one that does not match + the syntax of a quantifier, is taken as a literal character. For exam- ple, {,6} is not a quantifier, but a literal string of four characters. In UTF modes, quantifiers apply to characters rather than to individual - data units. Thus, for example, \x{100}{2} matches two characters, each + 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- @@ -5243,7 +6116,7 @@ REPETITION 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: @@ -5253,14 +6126,23 @@ REPETITION 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 (tweedle[dume]{3}\s*)+ has matched "tweedledum tweedledee" the value of the captured substring - is "tweedledee". However, if there are nested capturing subpatterns, - the corresponding captured values may have been set in previous itera- + is "tweedledee". However, if there are nested capturing subpatterns, + the corresponding captured values may have been set in previous itera- tions. For example, after /(a|(b))+/ @@ -5270,53 +6152,53 @@ REPETITION ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS - With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy") - repetition, failure of what follows normally causes the repeated item - to be re-evaluated to see if a different number of repeats allows the - rest of the pattern to match. Sometimes it is useful to prevent this, - either to change the nature of the match, or to cause it fail earlier - than it otherwise might, when the author of the pattern knows there is + With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy") + repetition, failure of what follows normally causes the repeated item + to be re-evaluated to see if a different number of repeats allows the + rest of the pattern to match. Sometimes it is useful to prevent this, + either to change the nature of the match, or to cause it fail earlier + than it otherwise might, when the author of the pattern knows there is no point in carrying on. - Consider, for example, the pattern \d+foo when applied to the subject + Consider, for example, the pattern \d+foo when applied to the subject line 123456bar After matching all 6 digits and then failing to match "foo", the normal - action of the matcher is to try again with only 5 digits matching the - \d+ item, and then with 4, and so on, before ultimately failing. - "Atomic grouping" (a term taken from Jeffrey Friedl's book) provides - the means for specifying that once a subpattern has matched, it is not + action of the matcher is to try again with only 5 digits matching the + \d+ item, and then with 4, and so on, before ultimately failing. + "Atomic grouping" (a term taken from Jeffrey Friedl's book) provides + the means for specifying that once a subpattern has matched, it is not to be re-evaluated in this way. - If we use atomic grouping for the previous example, the matcher gives - up immediately on failing to match "foo" the first time. The notation + If we use atomic grouping for the previous example, the matcher gives + up immediately on failing to match "foo" the first time. The notation is a kind of special parenthesis, starting with (?> as in this example: (?>\d+)foo - This kind of parenthesis "locks up" the part of the pattern it con- - tains once it has matched, and a failure further into the pattern is - prevented from backtracking into it. Backtracking past it to previous + This kind of parenthesis "locks up" the part of the pattern it con- + tains once it has matched, and a failure further into the pattern is + prevented from backtracking into it. Backtracking past it to previous items, however, works as normal. - An alternative description is that a subpattern of this type matches - the string of characters that an identical standalone pattern would + An alternative description is that a subpattern of this type matches + the string of characters that an identical standalone pattern would match, if anchored at the current point in the subject string. Atomic grouping subpatterns are not capturing subpatterns. Simple cases such as the above example can be thought of as a maximizing repeat that - must swallow everything it can. So, while both \d+ and \d+? are pre- - pared to adjust the number of digits they match in order to make the + must swallow everything it can. So, while both \d+ and \d+? are pre- + pared to adjust the number of digits they match in order to make the rest of the pattern match, (?>\d+) can only match an entire sequence of digits. - Atomic groups in general can of course contain arbitrarily complicated - subpatterns, and can be nested. However, when the subpattern for an + Atomic groups in general can of course contain arbitrarily complicated + subpatterns, and can be nested. However, when the subpattern for an atomic group is just a single repeated item, as in the example above, a - simpler notation, called a "possessive quantifier" can be used. This - consists of an additional + character following a quantifier. Using + simpler notation, called a "possessive quantifier" can be used. This + consists of an additional + character following a quantifier. Using this notation, the previous example can be rewritten as \d++foo @@ -5326,45 +6208,45 @@ ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS (abc|xyz){2,3}+ - Possessive quantifiers are always greedy; the setting of the + Possessive quantifiers are always greedy; the setting of the PCRE_UNGREEDY option is ignored. They are a convenient notation for the - simpler forms of atomic group. However, there is no difference in the - meaning of a possessive quantifier and the equivalent atomic group, - though there may be a performance difference; possessive quantifiers + simpler forms of atomic group. However, there is no difference in the + meaning of a possessive quantifier and the equivalent atomic group, + though there may be a performance difference; possessive quantifiers should be slightly faster. - The possessive quantifier syntax is an extension to the Perl 5.8 syn- - tax. Jeffrey Friedl originated the idea (and the name) in the first + The possessive quantifier syntax is an extension to the Perl 5.8 syn- + tax. Jeffrey Friedl originated the idea (and the name) in the first edition of his book. Mike McCloskey liked it, so implemented it when he - built Sun's Java package, and PCRE copied it from there. It ultimately + built Sun's Java package, and PCRE copied it from there. It ultimately found its way into Perl at release 5.10. PCRE has an optimization that automatically "possessifies" certain sim- - ple pattern constructs. For example, the sequence A+B is treated as - A++B because there is no point in backtracking into a sequence of A's + ple pattern constructs. For example, the sequence A+B is treated as + A++B because there is no point in backtracking into a sequence of A's when B must follow. - When a pattern contains an unlimited repeat inside a subpattern that - can itself be repeated an unlimited number of times, the use of an - atomic group is the only way to avoid some failing matches taking a + When a pattern contains an unlimited repeat inside a subpattern that + can itself be repeated an unlimited number of times, the use of an + atomic group is the only way to avoid some failing matches taking a very long time indeed. The pattern (\D+|<\d+>)*[!?] - matches an unlimited number of substrings that either consist of non- - digits, or digits enclosed in <>, followed by either ! or ?. When it + matches an unlimited number of substrings that either consist of non- + digits, or digits enclosed in <>, followed by either ! or ?. When it matches, it runs quickly. However, if it is applied to aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa - it takes a long time before reporting failure. This is because the - string can be divided between the internal \D+ repeat and the external - * repeat in a large number of ways, and all have to be tried. (The - example uses [!?] rather than a single character at the end, because - both PCRE and Perl have an optimization that allows for fast failure - when a single character is used. They remember the last single charac- - ter that is required for a match, and fail early if it is not present - in the string.) If the pattern is changed so that it uses an atomic + it takes a long time before reporting failure. This is because the + string can be divided between the internal \D+ repeat and the external + * repeat in a large number of ways, and all have to be tried. (The + example uses [!?] rather than a single character at the end, because + both PCRE and Perl have an optimization that allows for fast failure + when a single character is used. They remember the last single charac- + ter that is required for a match, and fail early if it is not present + in the string.) If the pattern is changed so that it uses an atomic group, like this: ((?>\D+)|<\d+>)*[!?] @@ -5376,28 +6258,28 @@ BACK REFERENCES Outside a character class, a backslash followed by a digit greater than 0 (and possibly further digits) is a back reference to a capturing sub- - pattern earlier (that is, to its left) in the pattern, provided there + pattern earlier (that is, to its left) in the pattern, provided there have been that many previous capturing left parentheses. However, if the decimal number following the backslash is less than 10, - it is always taken as a back reference, and causes an error only if - there are not that many capturing left parentheses in the entire pat- - tern. In other words, the parentheses that are referenced need not be - to the left of the reference for numbers less than 10. A "forward back - reference" of this type can make sense when a repetition is involved - and the subpattern to the right has participated in an earlier itera- + it is always taken as a back reference, and causes an error only if + there are not that many capturing left parentheses in the entire pat- + tern. In other words, the parentheses that are referenced need not be + to the left of the reference for numbers less than 10. A "forward back + reference" of this type can make sense when a repetition is involved + and the subpattern to the right has participated in an earlier itera- tion. - It is not possible to have a numerical "forward back reference" to a - subpattern whose number is 10 or more using this syntax because a - sequence such as \50 is interpreted as a character defined in octal. + It is not possible to have a numerical "forward back reference" to a + subpattern whose number is 10 or more using this syntax because a + sequence such as \50 is interpreted as a character defined in octal. See the subsection entitled "Non-printing characters" above for further - details of the handling of digits following a backslash. There is no - such problem when named parentheses are used. A back reference to any + details of the handling of digits following a backslash. There is no + such problem when named parentheses are used. A back reference to any subpattern is possible using named parentheses (see below). - Another way of avoiding the ambiguity inherent in the use of digits - following a backslash is to use the \g escape sequence. This escape + Another way of avoiding the ambiguity inherent in the use of digits + following a backslash is to use the \g escape sequence. This escape must be followed by an unsigned number or a negative number, optionally enclosed in braces. These examples are all identical: @@ -5405,7 +6287,7 @@ BACK REFERENCES (ring), \g1 (ring), \g{1} - An unsigned number specifies an absolute reference without the ambigu- + An unsigned number specifies an absolute reference without the ambigu- ity that is present in the older syntax. It is also useful when literal digits follow the reference. A negative number is a relative reference. Consider this example: @@ -5414,33 +6296,33 @@ BACK REFERENCES The sequence \g{-1} is a reference to the most recently started captur- ing subpattern before \g, that is, is it equivalent to \2 in this exam- - ple. Similarly, \g{-2} would be equivalent to \1. The use of relative - references can be helpful in long patterns, and also in patterns that - are created by joining together fragments that contain references + ple. Similarly, \g{-2} would be equivalent to \1. The use of relative + references can be helpful in long patterns, and also in patterns that + are created by joining together fragments that contain references within themselves. - A back reference matches whatever actually matched the capturing sub- - pattern in the current subject string, rather than anything matching + A back reference matches whatever actually matched the capturing sub- + pattern in the current subject string, rather than anything matching the subpattern itself (see "Subpatterns as subroutines" below for a way of doing that). So the pattern (sens|respons)e and \1ibility - matches "sense and sensibility" and "response and responsibility", but - not "sense and responsibility". If caseful matching is in force at the - time of the back reference, the case of letters is relevant. For exam- + matches "sense and sensibility" and "response and responsibility", but + not "sense and responsibility". If caseful matching is in force at the + time of the back reference, the case of letters is relevant. For exam- ple, ((?i)rah)\s+\1 - matches "rah rah" and "RAH RAH", but not "RAH rah", even though the + matches "rah rah" and "RAH RAH", but not "RAH rah", even though the original capturing subpattern is matched caselessly. - There are several different ways of writing back references to named - subpatterns. The .NET syntax \k{name} and the Perl syntax \k or - \k'name' are supported, as is the Python syntax (?P=name). Perl 5.10's + There are several different ways of writing back references to named + subpatterns. The .NET syntax \k{name} and the Perl syntax \k or + \k'name' are supported, as is the Python syntax (?P=name). Perl 5.10's unified back reference syntax, in which \g can be used for both numeric - and named references, is also supported. We could rewrite the above + and named references, is also supported. We could rewrite the above example in any of the following ways: (?(?i)rah)\s+\k @@ -5448,66 +6330,67 @@ BACK REFERENCES (?P(?i)rah)\s+(?P=p1) (?(?i)rah)\s+\g{p1} - A subpattern that is referenced by name may appear in the pattern + A subpattern that is referenced by name may appear in the pattern before or after the reference. - There may be more than one back reference to the same subpattern. If a - subpattern has not actually been used in a particular match, any back + There may be more than one back reference to the same subpattern. If a + subpattern has not actually been used in a particular match, any back references to it always fail by default. For example, the pattern (a|(bc))\2 - always fails if it starts to match "a" rather than "bc". However, if + always fails if it starts to match "a" rather than "bc". However, if the PCRE_JAVASCRIPT_COMPAT option is set at compile time, a back refer- ence to an unset value matches an empty string. - Because there may be many capturing parentheses in a pattern, all dig- - its following a backslash are taken as part of a potential back refer- - ence number. If the pattern continues with a digit character, some - delimiter must be used to terminate the back reference. If the - PCRE_EXTENDED option is set, this can be whitespace. Otherwise, the \g{ - syntax or an empty comment (see "Comments" below) can be used. + Because there may be many capturing parentheses in a pattern, all dig- + its following a backslash are taken as part of a potential back refer- + ence number. If the pattern continues with a digit character, some + delimiter must be used to terminate the back reference. If the + PCRE_EXTENDED option is set, this can be white space. Otherwise, the + \g{ syntax or an empty comment (see "Comments" below) can be used. Recursive back references - A back reference that occurs inside the parentheses to which it refers - fails when the subpattern is first used, so, for example, (a\1) never - matches. However, such references can be useful inside repeated sub- + A back reference that occurs inside the parentheses to which it refers + fails when the subpattern is first used, so, for example, (a\1) never + matches. However, such references can be useful inside repeated sub- patterns. For example, the pattern (a|b\1)+ matches any number of "a"s and also "aba", "ababbaa" etc. At each iter- - ation of the subpattern, the back reference matches the character - string corresponding to the previous iteration. In order for this to - work, the pattern must be such that the first iteration does not need - to match the back reference. This can be done using alternation, as in + ation of the subpattern, the back reference matches the character + string corresponding to the previous iteration. In order for this to + work, the pattern must be such that the first iteration does not need + to match the back reference. This can be done using alternation, as in the example above, or by a quantifier with a minimum of zero. - Back references of this type cause the group that they reference to be - treated as an atomic group. Once the whole group has been matched, a - subsequent matching failure cannot cause backtracking into the middle + Back references of this type cause the group that they reference to be + treated as an atomic group. Once the whole group has been matched, a + subsequent matching failure cannot cause backtracking into the middle of the group. ASSERTIONS - An assertion is a test on the characters following or preceding the - current matching point that does not actually consume any characters. - The simple assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are + An assertion is a test on the characters following or preceding the + current matching point that does not actually consume any characters. + The simple assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are described above. - More complicated assertions are coded as subpatterns. There are two - kinds: those that look ahead of the current position in the subject - string, and those that look behind it. An assertion subpattern is - matched in the normal way, except that it does not cause the current + More complicated assertions are coded as subpatterns. There are two + kinds: those that look ahead of the current position in the subject + string, and those that look behind it. An assertion subpattern is + matched in the normal way, except that it does not cause the current matching position to be changed. - Assertion subpatterns are not capturing subpatterns. If such an asser- - 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. + Assertion subpatterns are not capturing subpatterns. If such an asser- + 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. (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 @@ -5778,7 +6661,7 @@ CONDITIONAL SUBPATTERNS DEFINE is that it can be used to define subroutines that can be refer- enced from elsewhere. (The use of subroutines is described below.) For example, a pattern to match an IPv4 address such as "192.168.23.245" - could be written like this (ignore whitespace and line breaks): + could be written like this (ignore white space and line breaks): (?(DEFINE) (? 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) ) \b (?&byte) (\.(?&byte)){3} \b @@ -6122,126 +7005,140 @@ 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 + (?(?C9)(?=a)abc|def) + + Note that this applies only to assertion conditions, not to other types + of condition. + + 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. BACKTRACKING CONTROL - 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. + 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, 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 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, 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. + 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. - 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 is dif- - ferent in some cases. + The behaviour of these verbs in repeated groups, assertions, and in + subpatterns called as subroutines (whether or not recursively) is docu- + mented below. - 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 - any sequence of characters that does not include a closing parenthesis. - 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. + 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 @@ -6256,53 +7153,67 @@ 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 - match attempt that started at the letter "X". 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. + 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 + 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: @@ -6322,67 +7233,81 @@ 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 @@ -6397,7 +7322,7 @@ 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: @@ -6421,22 +7346,84 @@ 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) + cases 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 @@ -6448,18 +7435,18 @@ AUTHOR REVISION - Last updated: 09 January 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 26 April 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- @@ -6478,7 +7465,7 @@ CHARACTERS \a alarm, that is, the BEL character (hex 07) \cx "control-x", where x is any ASCII character \e escape (hex 1B) - \f formfeed (hex 0C) + \f form feed (hex 0C) \n newline (hex 0A) \r carriage return (hex 0D) \t tab (hex 09) @@ -6494,19 +7481,19 @@ CHARACTER TYPES \C one data unit, even in UTF mode (best avoided) \d a decimal digit \D a character that is not a decimal digit - \h a horizontal whitespace character - \H a character that is not a horizontal whitespace character + \h a horizontal white space character + \H a character that is not a horizontal white space character \N a character that is not a newline \p{xx} a character with the xx property \P{xx} a character without the xx property \R a newline sequence - \s a whitespace character - \S a character that is not a whitespace character - \v a vertical whitespace character - \V a character that is not a vertical whitespace character + \s a white space character + \S a character that is not a white space character + \v a vertical white space character + \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 @@ -6566,25 +7553,29 @@ 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 + Xuc Univerally-named character: one that can be + represented by a Universal Character Name Xwd Perl word: property Xan or underscore SCRIPT NAMES FOR \p AND \P - Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille, - Buginese, Buhid, Canadian_Aboriginal, Carian, Cham, Cherokee, Common, - Coptic, Cuneiform, Cypriot, Cyrillic, Deseret, Devanagari, Egyp- - tian_Hieroglyphs, Ethiopic, Georgian, Glagolitic, Gothic, Greek, - Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hiragana, Impe- - rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian, - Javanese, Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao, - Latin, Lepcha, Limbu, Linear_B, Lisu, Lycian, Lydian, Malayalam, - Meetei_Mayek, 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, Samaritan, Saurashtra, Shavian, - Sinhala, Sundanese, Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, - Tai_Tham, Tai_Viet, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, - Ugaritic, Vai, Yi. + 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, + Yi. CHARACTER CLASSES @@ -6605,7 +7596,7 @@ CHARACTER CLASSES lower lower case letter print printing, including space punct printing, excluding alphanumeric - space whitespace + space white space upper upper case letter word same as \w xdigit hexadecimal digit @@ -6695,9 +7686,13 @@ OPTION SETTING 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) @@ -6786,7 +7781,7 @@ 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 @@ -6824,115 +7819,113 @@ AUTHOR REVISION - Last updated: 10 January 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 26 April 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. From release 7.3 of PCRE, the check is according the + 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 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. + 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 - first byte of the failing character. The runtime functions pcre_exec() + 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 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_UTF8_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-8 codes. In this case, it does not - diagnose an invalid UTF-8 string. + 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 @@ -6944,7 +7937,7 @@ UNICODE PROPERTY SUPPORT 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 runtime functions + 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. @@ -6954,15 +7947,39 @@ UNICODE PROPERTY SUPPORT 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. + 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_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-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- @@ -6972,45 +7989,44 @@ UNICODE PROPERTY SUPPORT 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. + 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 + 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 - PCRE recognizes as digits, spaces, or word characters remain the same - set as in non-UTF mode, all with values less than 256. This remains - true even when PCRE is built to include Unicode property support, + PCRE recognizes as digits, spaces, or word characters remain the same + set as in non-UTF mode, all with values less than 256. This remains + true even when PCRE is built to include Unicode property support, because to do otherwise would slow down PCRE in many common cases. Note - in particular that this applies to \b and \B, because they are defined + in particular that this applies to \b and \B, because they are defined in terms of \w and \W. If you really want to test for a wider sense of, - say, "digit", you can use explicit Unicode property tests such as + say, "digit", you can use explicit Unicode property tests such as \p{Nd}. Alternatively, if you set the PCRE_UCP option, the way that the - character escapes work is changed so that Unicode properties are used + character escapes work is changed so that Unicode properties are used to determine which characters match. There are more details in the sec- tion on generic character types in the pcrepattern documentation. - 7. Similarly, characters that match the POSIX named character classes + 7. Similarly, characters that match the POSIX named character classes are all low-valued characters, unless the PCRE_UCP option is set. - 8. However, the horizontal and vertical whitespace matching escapes - (\h, \H, \v, and \V) do match all the appropriate Unicode characters, + 8. However, the horizontal and vertical white space matching escapes + (\h, \H, \v, and \V) do match all the appropriate Unicode characters, whether or not PCRE_UCP is set. - 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. + 9. Case-insensitive matching applies only to characters whose values + are less than 128, unless PCRE is built with Unicode property support. + 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 @@ -7022,18 +8038,18 @@ AUTHOR REVISION - Last updated: 13 January 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 @@ -7051,13 +8067,15 @@ 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 @@ -7071,17 +8089,18 @@ 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) - The Power PC support is designated as experimental because it has not - been fully tested. If --enable-jit is set on an unsupported platform, - compilation fails. + If --enable-jit is set on an unsupported platform, compilation fails. A program that is linked with PCRE 8.20 or later can tell if JIT sup- 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 ordinary PCRE - 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 @@ -7099,17 +8118,18 @@ 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 @@ -7118,30 +8138,51 @@ 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 + 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 + 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" below. - If JIT support is not available, PCRE_STUDY_JIT_COMPILE is ignored, and - no JIT data is set up. Otherwise, the compiled pattern is passed to the - JIT compiler, which turns it into machine code that executes much - faster than the normal interpretive code. When pcre_exec() is passed a - pcre_extra block containing a pointer to JIT code, it obeys that - instead of the normal code. The result is identical, but the code runs - much faster. + 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 + 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. + 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, or the JIT compiler was not able to handle - the pattern. + 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 many times as you like for matching different subject strings. @@ -7149,86 +8190,78 @@ 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_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and - PCRE_NOTEMPTY_ATSTART. Note in particular that partial matching is not - supported. + 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 - (*COMMIT) ) - (*MARK) ) - (*PRUNE) ) the backtracking control verbs - (*SKIP) ) - (*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 - PCRE_STUDY_JIT_COMPILE. There are three cases for the values of the + 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: (1) If callback is NULL and data is NULL, an internal 32K block @@ -7237,26 +8270,38 @@ CONTROLLING THE JIT STACK (2) If callback is NULL and data is not NULL, data must be a valid JIT stack, the result of calling pcre_jit_stack_alloc(). - (3) If callback not NULL, it must point to a function that is called - with data as an argument at the start of matching, in order to - set up a JIT stack. If the result is NULL, the internal 32K stack - is used; otherwise the return value must be a valid JIT stack, - the result of calling pcre_jit_stack_alloc(). + (3) If callback is not NULL, it must point to a function that is + called with data as an argument at the start of matching, in + order to set up a JIT stack. If the return from the callback + function is NULL, the internal 32K stack is used; otherwise the + return value must be a valid JIT stack, the result of calling + pcre_jit_stack_alloc(). - You may safely assign the same JIT stack to more than one pattern, as - long as they are all matched sequentially in the same thread. In a mul- - tithread application, each thread must use its own JIT stack. + 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 + interpreter. - Strictly speaking, even more is allowed. You can assign the same 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 inef- - ficient solution, and not recommended. + 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 + application is thread-safe. - This is a suggestion for how a typical multithreaded program might - operate: + 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 + up non-default JIT stacks might operate: + During thread initalization thread_local_var = pcre_jit_stack_alloc(...) @@ -7269,7 +8314,7 @@ CONTROLLING THE JIT STACK 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. + result of a successful study with PCRE_STUDY_JIT_COMPILE etc. JIT STACK FAQ @@ -7320,8 +8365,8 @@ JIT STACK FAQ 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. + 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 @@ -7329,7 +8374,7 @@ JIT STACK FAQ 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 + 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. @@ -7364,6 +8409,34 @@ 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) @@ -7378,18 +8451,18 @@ AUTHOR REVISION - Last updated: 08 January 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- @@ -7422,11 +8495,20 @@ PARTIAL MATCHING IN PCRE matching function. If both options are set, PCRE_PARTIAL_HARD takes precedence. - Setting a partial matching option disables the use of any just-in-time - code that was set up by studying the compiled pattern with the - PCRE_STUDY_JIT_COMPILE option. It also disables two of PCRE's standard - optimizations. PCRE remembers the last literal data unit in a pattern, - and abandons matching immediately if it is not present in the subject + If you want to use partial matching with just-in-time optimized code, + 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 + + PCRE_STUDY_JIT_COMPILE should also be set if you are going to run non- + partial matches on the same pattern. If the appropriate JIT study mode + has not been set for a match, the interpretive matching code is used. + + Setting a partial matching option disables two of PCRE's standard opti- + mizations. PCRE remembers the last literal data unit in a pattern, and + abandons matching immediately if it is not present in the subject string. This optimization cannot be used for a subject string that might match only partially. If the pattern was studied, PCRE knows the minimum length of a matching string, and does not bother to run the @@ -7434,180 +8516,185 @@ 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$/ @@ -7623,24 +8710,24 @@ EXAMPLE OF PARTIAL MATCHING USING PCRETEST data> j\P No match - The first data string is matched completely, so pcretest shows the - matched substrings. The remaining four strings do not match the com- + The first data string is matched completely, so pcretest shows the + matched substrings. The remaining four strings do not match the com- plete pattern, but the first two are partial matches. Similar output is obtained if DFA matching is used. - If the escape sequence \P is present more than once in a pcretest data + If the escape sequence \P is present more than once in a pcretest data line, the PCRE_PARTIAL_HARD option is set for the match. -MULTI-SEGMENT MATCHING WITH pcre_dfa_exec() OR pcre16_dfa_exec() +MULTI-SEGMENT MATCHING WITH pcre_dfa_exec() OR pcre[16|32]_dfa_exec() - When a partial match has been found using a DFA matching function, it - is possible to continue the match by providing additional subject data - and calling the function again with the same compiled regular expres- - sion, this time setting the PCRE_DFA_RESTART option. You must pass the + When a partial match has been found using a DFA matching function, it + is possible to continue the match by providing additional subject data + and calling the function again with the same compiled regular expres- + sion, this time setting the PCRE_DFA_RESTART option. You must pass the same working space as before, because this is where details of the pre- - vious partial match are stored. Here is an example using pcretest, - using the \R escape sequence to set the PCRE_DFA_RESTART option (\D + vious partial match are stored. Here is an example using pcretest, + using the \R escape sequence to set the PCRE_DFA_RESTART option (\D specifies the use of the DFA matching function): re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/ @@ -7649,48 +8736,48 @@ 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 + 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. + 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 @@ -7699,28 +8786,66 @@ ISSUES WITH MULTI-SEGMENT MATCHING whichever matching function is used. 1. If the pattern contains a test for the beginning of a line, you need - to pass the PCRE_NOTBOL option when the subject string for any call - does start at the beginning of a line. There is also a PCRE_NOTEOL + to pass the PCRE_NOTBOL option when the subject string for any call + does start at the beginning of a line. There is also a PCRE_NOTEOL option, but in practice when doing multi-segment matching you should be using PCRE_PARTIAL_HARD, which includes the effect of PCRE_NOTEOL. - 2. Lookbehind assertions at the start of a pattern are catered for in - the offsets that are returned for a partial match. However, in theory, - a lookbehind assertion later in the pattern could require even earlier - characters to be inspected, and it might not have been reached when a - partial match occurs. This is probably an extremely unlikely case; you - could guard against it to a certain extent by always including extra - characters at the start. + 2. Lookbehind assertions that have already been obeyed are catered for + in the offsets that are returned for a partial match. However a lookbe- + 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 + 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. 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 + 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/ + data> ab\P + 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 + 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 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)?/ @@ -7734,18 +8859,18 @@ 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)?/ @@ -7756,26 +8881,26 @@ ISSUES WITH MULTI-SEGMENT MATCHING data> gsb\R\P\P\D Partial match: gsb - 4. Patterns that contain alternatives at the top level which do not all - start with the same pattern item may not work as expected when + 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 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/ @@ -7785,10 +8910,10 @@ 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. @@ -7801,18 +8926,18 @@ AUTHOR REVISION - Last updated: 21 January 2012 - Copyright (c) 1997-2012 University of Cambridge. + Last updated: 20 February 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 @@ -7826,10 +8951,10 @@ 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 @@ -7839,13 +8964,13 @@ 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; @@ -7880,30 +9005,30 @@ 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. If you did not provide custom character tables when the pattern was compiled, the pointer in the compiled pattern is NULL, which causes the @@ -7911,10 +9036,10 @@ RE-USING A PRECOMPILED PATTERN 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. @@ -7936,18 +9061,18 @@ AUTHOR REVISION - Last updated: 10 January 2012 + Last updated: 24 June 2012 Copyright (c) 1997-2012 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- @@ -8007,30 +9132,30 @@ 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, @@ -8106,18 +9231,18 @@ 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 OF POSIX API #include @@ -8139,49 +9264,50 @@ 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 @@ -8195,58 +9321,58 @@ 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. @@ -8254,9 +9380,9 @@ 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 @@ -8278,19 +9404,19 @@ 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 @@ -8312,17 +9438,17 @@ 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 @@ -8330,34 +9456,34 @@ 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. @@ -8375,13 +9501,13 @@ REVISION ------------------------------------------------------------------------------ -PCRECPP(3) PCRECPP(3) +PCRECPP(3) Library Functions Manual PCRECPP(3) + NAME PCRE - Perl-compatible regular expressions. - SYNOPSIS OF C++ WRAPPER #include @@ -8393,13 +9519,14 @@ 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 @@ -8413,10 +9540,10 @@ 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. @@ -8442,7 +9569,7 @@ 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) @@ -8450,7 +9577,7 @@ 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; @@ -8465,41 +9592,41 @@ 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: @@ -8514,13 +9641,13 @@ 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: @@ -8539,9 +9666,9 @@ 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 @@ -8551,20 +9678,20 @@ PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE PCRE_DOTALL dot matches newlines /s PCRE_DOLLAR_ENDONLY $ matches only at end N/A PCRE_EXTRA strict escape parsing N/A - PCRE_EXTENDED ignore whitespaces /x + PCRE_EXTENDED ignore white spaces /x PCRE_UTF8 handles UTF8 chars built-in 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() @@ -8574,18 +9701,18 @@ 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: @@ -8594,8 +9721,8 @@ 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, @@ -8609,15 +9736,15 @@ 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$", @@ -8629,10 +9756,10 @@ 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. @@ -8646,11 +9773,11 @@ 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) @@ -8659,10 +9786,10 @@ 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: @@ -8677,30 +9804,30 @@ 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. @@ -8717,13 +9844,13 @@ 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 @@ -8803,27 +9930,28 @@ 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 never in practice be relevant. 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. + units (bytes for the 8-bit library, 32-bit units for the 32-bit + library, and 32-bit units for the 32-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 + 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. @@ -8831,18 +9959,22 @@ SIZE AND OTHER LIMITATIONS can be no more than 65535 capturing subpatterns. There is a limit to the number of forward references to subsequent sub- - patterns of around 200,000. Repeated forward references with fixed - upper limits, for example, (?2){0,100} when subpattern number 2 is to - the right, are included in the count. There is no limit to the number + patterns of around 200,000. Repeated forward references with fixed + upper limits, for example, (?2){0,100} when subpattern number 2 is to + the right, are included in the count. There is no limit to the number of backward references. The maximum length of name for a named subpattern is 32 characters, and the maximum number of named subpatterns is 10000. - The maximum length of a subject string is the largest positive number - that an integer variable can hold. However, when using the traditional + 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 and + 32-bit library. + + The maximum length of a subject string is the largest positive number + that an integer variable can hold. However, when using the traditional matching function, PCRE uses recursion to handle subpatterns and indef- - inite repetition. This means that the available stack space may limit + inite repetition. This means that the available stack space may limit the size of a subject string that can be processed by certain patterns. For a discussion of stack issues, see the pcrestack documentation. @@ -8856,21 +9988,21 @@ AUTHOR REVISION - Last updated: 08 January 2012 + Last updated: 04 May 2012 Copyright (c) 1997-2012 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 @@ -8886,110 +10018,111 @@ 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 "