Annotation of embedaddon/pcre/doc/pcreapi.3, revision 1.1.1.2
1.1 misho 1: .TH PCREAPI 3
2: .SH NAME
3: PCRE - Perl-compatible regular expressions
1.1.1.2 ! misho 4: .sp
! 5: .B #include <pcre.h>
! 6: .
! 7: .
1.1 misho 8: .SH "PCRE NATIVE API BASIC FUNCTIONS"
9: .rs
10: .sp
11: .SM
12: .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
13: .ti +5n
14: .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
15: .ti +5n
16: .B const unsigned char *\fItableptr\fP);
17: .PP
18: .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
19: .ti +5n
20: .B int *\fIerrorcodeptr\fP,
21: .ti +5n
22: .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
23: .ti +5n
24: .B const unsigned char *\fItableptr\fP);
25: .PP
26: .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
27: .ti +5n
28: .B const char **\fIerrptr\fP);
29: .PP
30: .B void pcre_free_study(pcre_extra *\fIextra\fP);
31: .PP
32: .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
33: .ti +5n
34: .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
35: .ti +5n
36: .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
37: .PP
38: .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
39: .ti +5n
40: .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
41: .ti +5n
42: .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
43: .ti +5n
44: .B int *\fIworkspace\fP, int \fIwscount\fP);
1.1.1.2 ! misho 45: .
! 46: .
! 47: .SH "PCRE NATIVE API STRING EXTRACTION FUNCTIONS"
! 48: .rs
! 49: .sp
1.1 misho 50: .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
51: .ti +5n
52: .B const char *\fIsubject\fP, int *\fIovector\fP,
53: .ti +5n
54: .B int \fIstringcount\fP, const char *\fIstringname\fP,
55: .ti +5n
56: .B char *\fIbuffer\fP, int \fIbuffersize\fP);
57: .PP
58: .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
59: .ti +5n
60: .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
61: .ti +5n
62: .B int \fIbuffersize\fP);
63: .PP
64: .B int pcre_get_named_substring(const pcre *\fIcode\fP,
65: .ti +5n
66: .B const char *\fIsubject\fP, int *\fIovector\fP,
67: .ti +5n
68: .B int \fIstringcount\fP, const char *\fIstringname\fP,
69: .ti +5n
70: .B const char **\fIstringptr\fP);
71: .PP
72: .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
73: .ti +5n
74: .B const char *\fIname\fP);
75: .PP
76: .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
77: .ti +5n
78: .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
79: .PP
80: .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
81: .ti +5n
82: .B int \fIstringcount\fP, int \fIstringnumber\fP,
83: .ti +5n
84: .B const char **\fIstringptr\fP);
85: .PP
86: .B int pcre_get_substring_list(const char *\fIsubject\fP,
87: .ti +5n
88: .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
89: .PP
90: .B void pcre_free_substring(const char *\fIstringptr\fP);
91: .PP
92: .B void pcre_free_substring_list(const char **\fIstringptr\fP);
1.1.1.2 ! misho 93: .
! 94: .
! 95: .SH "PCRE NATIVE API AUXILIARY FUNCTIONS"
! 96: .rs
! 97: .sp
! 98: .B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP);
! 99: .PP
! 100: .B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP);
! 101: .PP
! 102: .B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP,
! 103: .ti +5n
! 104: .B pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);
1.1 misho 105: .PP
106: .B const unsigned char *pcre_maketables(void);
107: .PP
108: .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
109: .ti +5n
110: .B int \fIwhat\fP, void *\fIwhere\fP);
111: .PP
112: .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
113: .PP
114: .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
115: .PP
1.1.1.2 ! misho 116: .B const char *pcre_version(void);
! 117: .PP
! 118: .B int pcre_pattern_to_host_byte_order(pcre *\fIcode\fP,
! 119: .ti +5n
! 120: .B pcre_extra *\fIextra\fP, const unsigned char *\fItables\fP);
1.1 misho 121: .
122: .
123: .SH "PCRE NATIVE API INDIRECTED FUNCTIONS"
124: .rs
125: .sp
126: .B void *(*pcre_malloc)(size_t);
127: .PP
128: .B void (*pcre_free)(void *);
129: .PP
130: .B void *(*pcre_stack_malloc)(size_t);
131: .PP
132: .B void (*pcre_stack_free)(void *);
133: .PP
134: .B int (*pcre_callout)(pcre_callout_block *);
135: .
136: .
1.1.1.2 ! misho 137: .SH "PCRE 8-BIT AND 16-BIT LIBRARIES"
! 138: .rs
! 139: .sp
! 140: From release 8.30, PCRE can be compiled as a library for handling 16-bit
! 141: character strings as well as, or instead of, the original library that handles
! 142: 8-bit character strings. To avoid too much complication, this document
! 143: describes the 8-bit versions of the functions, with only occasional references
! 144: to the 16-bit library.
! 145: .P
! 146: The 16-bit functions operate in the same way as their 8-bit counterparts; they
! 147: just use different data types for their arguments and results, and their names
! 148: start with \fBpcre16_\fP instead of \fBpcre_\fP. For every option that has UTF8
! 149: in its name (for example, PCRE_UTF8), there is a corresponding 16-bit name with
! 150: UTF8 replaced by UTF16. This facility is in fact just cosmetic; the 16-bit
! 151: option names define the same bit values.
! 152: .P
! 153: References to bytes and UTF-8 in this document should be read as references to
! 154: 16-bit data quantities and UTF-16 when using the 16-bit library, unless
! 155: specified otherwise. More details of the specific differences for the 16-bit
! 156: library are given in the
! 157: .\" HREF
! 158: \fBpcre16\fP
! 159: .\"
! 160: page.
! 161: .
! 162: .
1.1 misho 163: .SH "PCRE API OVERVIEW"
164: .rs
165: .sp
166: PCRE has its own native API, which is described in this document. There are
1.1.1.2 ! misho 167: also some wrapper functions (for the 8-bit library only) that correspond to the
! 168: POSIX regular expression API, but they do not give access to all the
! 169: functionality. They are described in the
1.1 misho 170: .\" HREF
171: \fBpcreposix\fP
172: .\"
173: documentation. Both of these APIs define a set of C function calls. A C++
1.1.1.2 ! misho 174: wrapper (again for the 8-bit library only) is also distributed with PCRE. It is
! 175: documented in the
1.1 misho 176: .\" HREF
177: \fBpcrecpp\fP
178: .\"
179: page.
180: .P
181: The native API C function prototypes are defined in the header file
1.1.1.2 ! misho 182: \fBpcre.h\fP, and on Unix-like systems the (8-bit) library itself is called
! 183: \fBlibpcre\fP. It can normally be accessed by adding \fB-lpcre\fP to the
! 184: command for linking an application that uses PCRE. The header file defines the
! 185: macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers
! 186: for the library. Applications can use these to include support for different
! 187: releases of PCRE.
1.1 misho 188: .P
189: In a Windows environment, if you want to statically link an application program
190: against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
191: including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
192: \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
193: \fB__declspec(dllimport)\fP, with unwanted results.
194: .P
195: The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
196: and \fBpcre_exec()\fP are used for compiling and matching regular expressions
197: in a Perl-compatible manner. A sample program that demonstrates the simplest
198: way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
199: source distribution. A listing of this program is given in the
200: .\" HREF
201: \fBpcredemo\fP
202: .\"
203: documentation, and the
204: .\" HREF
205: \fBpcresample\fP
206: .\"
207: documentation describes how to compile and run it.
208: .P
209: Just-in-time compiler support is an optional feature of PCRE that can be built
210: in appropriate hardware environments. It greatly speeds up the matching
211: performance of many patterns. Simple programs can easily request that it be
212: used if available, by setting an option that is ignored when it is not
213: relevant. More complicated programs might need to make use of the functions
214: \fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and
215: \fBpcre_assign_jit_stack()\fP in order to control the JIT code's memory usage.
216: These functions are discussed in the
217: .\" HREF
218: \fBpcrejit\fP
219: .\"
220: documentation.
221: .P
222: A second matching function, \fBpcre_dfa_exec()\fP, which is not
223: Perl-compatible, is also provided. This uses a different algorithm for the
224: matching. The alternative algorithm finds all possible matches (at a given
225: point in the subject), and scans the subject just once (unless there are
226: lookbehind assertions). However, this algorithm does not return captured
227: substrings. A description of the two matching algorithms and their advantages
228: and disadvantages is given in the
229: .\" HREF
230: \fBpcrematching\fP
231: .\"
232: documentation.
233: .P
234: In addition to the main compiling and matching functions, there are convenience
235: functions for extracting captured substrings from a subject string that is
236: matched by \fBpcre_exec()\fP. They are:
237: .sp
238: \fBpcre_copy_substring()\fP
239: \fBpcre_copy_named_substring()\fP
240: \fBpcre_get_substring()\fP
241: \fBpcre_get_named_substring()\fP
242: \fBpcre_get_substring_list()\fP
243: \fBpcre_get_stringnumber()\fP
244: \fBpcre_get_stringtable_entries()\fP
245: .sp
246: \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
247: provided, to free the memory used for extracted strings.
248: .P
249: The function \fBpcre_maketables()\fP is used to build a set of character tables
250: in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
251: or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
252: specialist use. Most commonly, no special tables are passed, in which case
253: internal tables that are generated when PCRE is built are used.
254: .P
255: The function \fBpcre_fullinfo()\fP is used to find out information about a
1.1.1.2 ! misho 256: compiled pattern. The function \fBpcre_version()\fP returns a pointer to a
! 257: string containing the version of PCRE and its date of release.
1.1 misho 258: .P
259: The function \fBpcre_refcount()\fP maintains a reference count in a data block
260: containing a compiled pattern. This is provided for the benefit of
261: object-oriented applications.
262: .P
263: The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
264: the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
265: respectively. PCRE calls the memory management functions via these variables,
266: so a calling program can replace them if it wishes to intercept the calls. This
267: should be done before calling any PCRE functions.
268: .P
269: The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
270: indirections to memory management functions. These special functions are used
271: only when PCRE is compiled to use the heap for remembering data, instead of
272: recursive function calls, when running the \fBpcre_exec()\fP function. See the
273: .\" HREF
274: \fBpcrebuild\fP
275: .\"
276: documentation for details of how to do this. It is a non-standard way of
277: building PCRE, for use in environments that have limited stacks. Because of the
278: greater use of memory management, it runs more slowly. Separate functions are
279: provided so that special-purpose external code can be used for this case. When
280: used, these functions are always called in a stack-like manner (last obtained,
281: first freed), and always for memory blocks of the same size. There is a
282: discussion about PCRE's stack usage in the
283: .\" HREF
284: \fBpcrestack\fP
285: .\"
286: documentation.
287: .P
288: The global variable \fBpcre_callout\fP initially contains NULL. It can be set
289: by the caller to a "callout" function, which PCRE will then call at specified
290: points during a matching operation. Details are given in the
291: .\" HREF
292: \fBpcrecallout\fP
293: .\"
294: documentation.
295: .
296: .
297: .\" HTML <a name="newlines"></a>
298: .SH NEWLINES
299: .rs
300: .sp
301: PCRE supports five different conventions for indicating line breaks in
302: strings: a single CR (carriage return) character, a single LF (linefeed)
303: character, the two-character sequence CRLF, any of the three preceding, or any
304: Unicode newline sequence. The Unicode newline sequences are the three just
305: mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
306: U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
307: (paragraph separator, U+2029).
308: .P
309: Each of the first three conventions is used by at least one operating system as
310: its standard newline sequence. When PCRE is built, a default can be specified.
311: The default default is LF, which is the Unix standard. When PCRE is run, the
312: default can be overridden, either when a pattern is compiled, or when it is
313: matched.
314: .P
315: At compile time, the newline convention can be specified by the \fIoptions\fP
316: argument of \fBpcre_compile()\fP, or it can be specified by special text at the
317: start of the pattern itself; this overrides any other settings. See the
318: .\" HREF
319: \fBpcrepattern\fP
320: .\"
321: page for details of the special character sequences.
322: .P
323: In the PCRE documentation the word "newline" is used to mean "the character or
324: pair of characters that indicate a line break". The choice of newline
325: convention affects the handling of the dot, circumflex, and dollar
326: metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
327: recognized line ending sequence, the match position advancement for a
328: non-anchored pattern. There is more detail about this in the
329: .\" HTML <a href="#execoptions">
330: .\" </a>
331: section on \fBpcre_exec()\fP options
332: .\"
333: below.
334: .P
335: The choice of newline convention does not affect the interpretation of
336: the \en or \er escape sequences, nor does it affect what \eR matches, which is
337: controlled in a similar way, but by separate options.
338: .
339: .
340: .SH MULTITHREADING
341: .rs
342: .sp
343: The PCRE functions can be used in multi-threading applications, with the
344: proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
345: \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
346: callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
347: .P
348: The compiled form of a regular expression is not altered during matching, so
349: the same compiled pattern can safely be used by several threads at once.
350: .P
351: If the just-in-time optimization feature is being used, it needs separate
352: memory stack areas for each thread. See the
353: .\" HREF
354: \fBpcrejit\fP
355: .\"
356: documentation for more details.
357: .
358: .
359: .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
360: .rs
361: .sp
362: The compiled form of a regular expression can be saved and re-used at a later
363: time, possibly by a different program, and even on a host other than the one on
364: which it was compiled. Details are given in the
365: .\" HREF
366: \fBpcreprecompile\fP
367: .\"
1.1.1.2 ! misho 368: documentation, which includes a description of the
! 369: \fBpcre_pattern_to_host_byte_order()\fP function. However, compiling a regular
! 370: expression with one version of PCRE for use with a different version is not
! 371: guaranteed to work and may cause crashes.
1.1 misho 372: .
373: .
374: .SH "CHECKING BUILD-TIME OPTIONS"
375: .rs
376: .sp
377: .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
378: .PP
379: The function \fBpcre_config()\fP makes it possible for a PCRE client to
380: discover which optional features have been compiled into the PCRE library. The
381: .\" HREF
382: \fBpcrebuild\fP
383: .\"
384: documentation has more details about these optional features.
385: .P
386: The first argument for \fBpcre_config()\fP is an integer, specifying which
387: information is required; the second argument is a pointer to a variable into
1.1.1.2 ! misho 388: which the information is placed. The returned value is zero on success, or the
! 389: negative error code PCRE_ERROR_BADOPTION if the value in the first argument is
! 390: not recognized. The following information is available:
1.1 misho 391: .sp
392: PCRE_CONFIG_UTF8
393: .sp
394: The output is an integer that is set to one if UTF-8 support is available;
1.1.1.2 ! misho 395: otherwise it is set to zero. If this option is given to the 16-bit version of
! 396: this function, \fBpcre16_config()\fP, the result is PCRE_ERROR_BADOPTION.
! 397: .sp
! 398: PCRE_CONFIG_UTF16
! 399: .sp
! 400: The output is an integer that is set to one if UTF-16 support is available;
! 401: otherwise it is set to zero. This value should normally be given to the 16-bit
! 402: version of this function, \fBpcre16_config()\fP. If it is given to the 8-bit
! 403: version of this function, the result is PCRE_ERROR_BADOPTION.
1.1 misho 404: .sp
405: PCRE_CONFIG_UNICODE_PROPERTIES
406: .sp
407: The output is an integer that is set to one if support for Unicode character
408: properties is available; otherwise it is set to zero.
409: .sp
410: PCRE_CONFIG_JIT
411: .sp
412: The output is an integer that is set to one if support for just-in-time
413: compiling is available; otherwise it is set to zero.
414: .sp
1.1.1.2 ! misho 415: PCRE_CONFIG_JITTARGET
! 416: .sp
! 417: The output is a pointer to a zero-terminated "const char *" string. If JIT
! 418: support is available, the string contains the name of the architecture for
! 419: which the JIT compiler is configured, for example "x86 32bit (little endian +
! 420: unaligned)". If JIT support is not available, the result is NULL.
! 421: .sp
1.1 misho 422: PCRE_CONFIG_NEWLINE
423: .sp
424: The output is an integer whose value specifies the default character sequence
425: that is recognized as meaning "newline". The four values that are supported
426: are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
427: Though they are derived from ASCII, the same values are returned in EBCDIC
428: environments. The default should normally correspond to the standard sequence
429: for your operating system.
430: .sp
431: PCRE_CONFIG_BSR
432: .sp
433: The output is an integer whose value indicates what character sequences the \eR
434: escape sequence matches by default. A value of 0 means that \eR matches any
435: Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
436: or CRLF. The default can be overridden when a pattern is compiled or matched.
437: .sp
438: PCRE_CONFIG_LINK_SIZE
439: .sp
440: The output is an integer that contains the number of bytes used for internal
1.1.1.2 ! misho 441: linkage in compiled regular expressions. For the 8-bit library, the value can
! 442: be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still
! 443: a number of bytes. The default value of 2 is sufficient for all but the most
! 444: massive patterns, since it allows the compiled pattern to be up to 64K in size.
! 445: Larger values allow larger regular expressions to be compiled, at the expense
! 446: of slower matching.
1.1 misho 447: .sp
448: PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
449: .sp
450: The output is an integer that contains the threshold above which the POSIX
451: interface uses \fBmalloc()\fP for output vectors. Further details are given in
452: the
453: .\" HREF
454: \fBpcreposix\fP
455: .\"
456: documentation.
457: .sp
458: PCRE_CONFIG_MATCH_LIMIT
459: .sp
460: The output is a long integer that gives the default limit for the number of
461: internal matching function calls in a \fBpcre_exec()\fP execution. Further
462: details are given with \fBpcre_exec()\fP below.
463: .sp
464: PCRE_CONFIG_MATCH_LIMIT_RECURSION
465: .sp
466: The output is a long integer that gives the default limit for the depth of
467: recursion when calling the internal matching function in a \fBpcre_exec()\fP
468: execution. Further details are given with \fBpcre_exec()\fP below.
469: .sp
470: PCRE_CONFIG_STACKRECURSE
471: .sp
472: The output is an integer that is set to one if internal recursion when running
473: \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
474: to remember their state. This is the usual way that PCRE is compiled. The
475: output is zero if PCRE was compiled to use blocks of data on the heap instead
476: of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
477: \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
478: avoiding the use of the stack.
479: .
480: .
481: .SH "COMPILING A PATTERN"
482: .rs
483: .sp
484: .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
485: .ti +5n
486: .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
487: .ti +5n
488: .B const unsigned char *\fItableptr\fP);
489: .sp
490: .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
491: .ti +5n
492: .B int *\fIerrorcodeptr\fP,
493: .ti +5n
494: .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
495: .ti +5n
496: .B const unsigned char *\fItableptr\fP);
497: .P
498: Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
499: called to compile a pattern into an internal form. The only difference between
500: the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
501: \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
502: too much repetition, we refer just to \fBpcre_compile()\fP below, but the
503: information applies equally to \fBpcre_compile2()\fP.
504: .P
505: The pattern is a C string terminated by a binary zero, and is passed in the
506: \fIpattern\fP argument. A pointer to a single block of memory that is obtained
507: via \fBpcre_malloc\fP is returned. This contains the compiled code and related
508: data. The \fBpcre\fP type is defined for the returned block; this is a typedef
509: for a structure whose contents are not externally defined. It is up to the
510: caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
511: .P
512: Although the compiled code of a PCRE regex is relocatable, that is, it does not
513: depend on memory location, the complete \fBpcre\fP data block is not
514: fully relocatable, because it may contain a copy of the \fItableptr\fP
515: argument, which is an address (see below).
516: .P
517: The \fIoptions\fP argument contains various bit settings that affect the
518: compilation. It should be zero if no options are required. The available
519: options are described below. Some of them (in particular, those that are
520: compatible with Perl, but some others as well) can also be set and unset from
521: within the pattern (see the detailed description in the
522: .\" HREF
523: \fBpcrepattern\fP
524: .\"
525: documentation). For those options that can be different in different parts of
526: the pattern, the contents of the \fIoptions\fP argument specifies their
527: settings at the start of compilation and execution. The PCRE_ANCHORED,
528: PCRE_BSR_\fIxxx\fP, PCRE_NEWLINE_\fIxxx\fP, PCRE_NO_UTF8_CHECK, and
529: PCRE_NO_START_OPT options can be set at the time of matching as well as at
530: compile time.
531: .P
532: If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
533: Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
534: NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
535: error message. This is a static string that is part of the library. You must
536: not try to free it. Normally, the offset from the start of the pattern to the
537: byte that was being processed when the error was discovered is placed in the
538: variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, an
539: immediate error is given). However, for an invalid UTF-8 string, the offset is
1.1.1.2 ! misho 540: that of the first byte of the failing character.
1.1 misho 541: .P
1.1.1.2 ! misho 542: Some errors are not detected until the whole pattern has been scanned; in these
! 543: cases, the offset passed back is the length of the pattern. Note that the
! 544: offset is in bytes, not characters, even in UTF-8 mode. It may sometimes point
! 545: into the middle of a UTF-8 character.
1.1 misho 546: .P
547: If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
548: \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
549: returned via this argument in the event of an error. This is in addition to the
550: textual error message. Error codes and messages are listed below.
551: .P
552: If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
553: character tables that are built when PCRE is compiled, using the default C
554: locale. Otherwise, \fItableptr\fP must be an address that is the result of a
555: call to \fBpcre_maketables()\fP. This value is stored with the compiled
556: pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
557: passed to it. For more discussion, see the section on locale support below.
558: .P
559: This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
560: .sp
561: pcre *re;
562: const char *error;
563: int erroffset;
564: re = pcre_compile(
565: "^A.*Z", /* the pattern */
566: 0, /* default options */
567: &error, /* for error message */
568: &erroffset, /* for error offset */
569: NULL); /* use default character tables */
570: .sp
571: The following names for option bits are defined in the \fBpcre.h\fP header
572: file:
573: .sp
574: PCRE_ANCHORED
575: .sp
576: If this bit is set, the pattern is forced to be "anchored", that is, it is
577: constrained to match only at the first matching point in the string that is
578: being searched (the "subject string"). This effect can also be achieved by
579: appropriate constructs in the pattern itself, which is the only way to do it in
580: Perl.
581: .sp
582: PCRE_AUTO_CALLOUT
583: .sp
584: If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
585: all with number 255, before each pattern item. For discussion of the callout
586: facility, see the
587: .\" HREF
588: \fBpcrecallout\fP
589: .\"
590: documentation.
591: .sp
592: PCRE_BSR_ANYCRLF
593: PCRE_BSR_UNICODE
594: .sp
595: These options (which are mutually exclusive) control what the \eR escape
596: sequence matches. The choice is either to match only CR, LF, or CRLF, or to
597: match any Unicode newline sequence. The default is specified when PCRE is
598: built. It can be overridden from within the pattern, or by setting an option
599: when a compiled pattern is matched.
600: .sp
601: PCRE_CASELESS
602: .sp
603: If this bit is set, letters in the pattern match both upper and lower case
604: letters. It is equivalent to Perl's /i option, and it can be changed within a
605: pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
606: concept of case for characters whose values are less than 128, so caseless
607: matching is always possible. For characters with higher values, the concept of
608: case is supported if PCRE is compiled with Unicode property support, but not
609: otherwise. If you want to use caseless matching for characters 128 and above,
610: you must ensure that PCRE is compiled with Unicode property support as well as
611: with UTF-8 support.
612: .sp
613: PCRE_DOLLAR_ENDONLY
614: .sp
615: If this bit is set, a dollar metacharacter in the pattern matches only at the
616: end of the subject string. Without this option, a dollar also matches
617: immediately before a newline at the end of the string (but not before any other
618: newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
619: There is no equivalent to this option in Perl, and no way to set it within a
620: pattern.
621: .sp
622: PCRE_DOTALL
623: .sp
624: If this bit is set, a dot metacharacter in the pattern matches a character of
625: any value, including one that indicates a newline. However, it only ever
626: matches one character, even if newlines are coded as CRLF. Without this option,
627: a dot does not match when the current position is at a newline. This option is
628: equivalent to Perl's /s option, and it can be changed within a pattern by a
629: (?s) option setting. A negative class such as [^a] always matches newline
630: characters, independent of the setting of this option.
631: .sp
632: PCRE_DUPNAMES
633: .sp
634: If this bit is set, names used to identify capturing subpatterns need not be
635: unique. This can be helpful for certain types of pattern when it is known that
636: only one instance of the named subpattern can ever be matched. There are more
637: details of named subpatterns below; see also the
638: .\" HREF
639: \fBpcrepattern\fP
640: .\"
641: documentation.
642: .sp
643: PCRE_EXTENDED
644: .sp
645: If this bit is set, whitespace data characters in the pattern are totally
646: ignored except when escaped or inside a character class. Whitespace does not
647: include the VT character (code 11). In addition, characters between an
648: unescaped # outside a character class and the next newline, inclusive, are also
649: ignored. This is equivalent to Perl's /x option, and it can be changed within a
650: pattern by a (?x) option setting.
651: .P
652: Which characters are interpreted as newlines is controlled by the options
653: passed to \fBpcre_compile()\fP or by a special sequence at the start of the
654: pattern, as described in the section entitled
655: .\" HTML <a href="pcrepattern.html#newlines">
656: .\" </a>
657: "Newline conventions"
658: .\"
659: in the \fBpcrepattern\fP documentation. Note that the end of this type of
660: comment is a literal newline sequence in the pattern; escape sequences that
661: happen to represent a newline do not count.
662: .P
663: This option makes it possible to include comments inside complicated patterns.
664: Note, however, that this applies only to data characters. Whitespace characters
665: may never appear within special character sequences in a pattern, for example
666: within the sequence (?( that introduces a conditional subpattern.
667: .sp
668: PCRE_EXTRA
669: .sp
670: This option was invented in order to turn on additional functionality of PCRE
671: that is incompatible with Perl, but it is currently of very little use. When
672: set, any backslash in a pattern that is followed by a letter that has no
673: special meaning causes an error, thus reserving these combinations for future
674: expansion. By default, as in Perl, a backslash followed by a letter with no
675: special meaning is treated as a literal. (Perl can, however, be persuaded to
676: give an error for this, by running it with the -w option.) There are at present
677: no other features controlled by this option. It can also be set by a (?X)
678: option setting within a pattern.
679: .sp
680: PCRE_FIRSTLINE
681: .sp
682: If this option is set, an unanchored pattern is required to match before or at
683: the first newline in the subject string, though the matched text may continue
684: over the newline.
685: .sp
686: PCRE_JAVASCRIPT_COMPAT
687: .sp
688: If this option is set, PCRE's behaviour is changed in some ways so that it is
689: compatible with JavaScript rather than Perl. The changes are as follows:
690: .P
691: (1) A lone closing square bracket in a pattern causes a compile-time error,
692: because this is illegal in JavaScript (by default it is treated as a data
693: character). Thus, the pattern AB]CD becomes illegal when this option is set.
694: .P
695: (2) At run time, a back reference to an unset subpattern group matches an empty
696: string (by default this causes the current matching alternative to fail). A
697: pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
698: an "a" in the subject), whereas it fails by default, for Perl compatibility.
699: .P
700: (3) \eU matches an upper case "U" character; by default \eU causes a compile
701: time error (Perl uses \eU to upper case subsequent characters).
702: .P
703: (4) \eu matches a lower case "u" character unless it is followed by four
704: hexadecimal digits, in which case the hexadecimal number defines the code point
705: to match. By default, \eu causes a compile time error (Perl uses it to upper
706: case the following character).
707: .P
708: (5) \ex matches a lower case "x" character unless it is followed by two
709: hexadecimal digits, in which case the hexadecimal number defines the code point
710: to match. By default, as in Perl, a hexadecimal number is always expected after
711: \ex, but it may have zero, one, or two digits (so, for example, \exz matches a
712: binary zero character followed by z).
713: .sp
714: PCRE_MULTILINE
715: .sp
716: By default, PCRE treats the subject string as consisting of a single line of
717: characters (even if it actually contains newlines). The "start of line"
718: metacharacter (^) matches only at the start of the string, while the "end of
719: line" metacharacter ($) matches only at the end of the string, or before a
720: terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
721: Perl.
722: .P
723: When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
724: match immediately following or immediately before internal newlines in the
725: subject string, respectively, as well as at the very start and end. This is
726: equivalent to Perl's /m option, and it can be changed within a pattern by a
727: (?m) option setting. If there are no newlines in a subject string, or no
728: occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
729: .sp
730: PCRE_NEWLINE_CR
731: PCRE_NEWLINE_LF
732: PCRE_NEWLINE_CRLF
733: PCRE_NEWLINE_ANYCRLF
734: PCRE_NEWLINE_ANY
735: .sp
736: These options override the default newline definition that was chosen when PCRE
737: was built. Setting the first or the second specifies that a newline is
738: indicated by a single character (CR or LF, respectively). Setting
739: PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
740: CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
741: preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
742: that any Unicode newline sequence should be recognized. The Unicode newline
743: sequences are the three just mentioned, plus the single characters VT (vertical
744: tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
1.1.1.2 ! misho 745: separator, U+2028), and PS (paragraph separator, U+2029). For the 8-bit
! 746: library, the last two are recognized only in UTF-8 mode.
1.1 misho 747: .P
748: The newline setting in the options word uses three bits that are treated
749: as a number, giving eight possibilities. Currently only six are used (default
750: plus the five values above). This means that if you set more than one newline
751: option, the combination may or may not be sensible. For example,
752: PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
753: other combinations may yield unused numbers and cause an error.
754: .P
755: The only time that a line break in a pattern is specially recognized when
756: compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
757: and so are ignored in this mode. Also, an unescaped # outside a character class
758: indicates a comment that lasts until after the next line break sequence. In
759: other circumstances, line break sequences in patterns are treated as literal
760: data.
761: .P
762: The newline option that is set at compile time becomes the default that is used
763: for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
764: .sp
765: PCRE_NO_AUTO_CAPTURE
766: .sp
767: If this option is set, it disables the use of numbered capturing parentheses in
768: the pattern. Any opening parenthesis that is not followed by ? behaves as if it
769: were followed by ?: but named parentheses can still be used for capturing (and
770: they acquire numbers in the usual way). There is no equivalent of this option
771: in Perl.
772: .sp
773: NO_START_OPTIMIZE
774: .sp
775: This is an option that acts at matching time; that is, it is really an option
776: for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
777: it is remembered with the compiled pattern and assumed at matching time. For
778: details see the discussion of PCRE_NO_START_OPTIMIZE
779: .\" HTML <a href="#execoptions">
780: .\" </a>
781: below.
782: .\"
783: .sp
784: PCRE_UCP
785: .sp
786: This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
787: \ew, and some of the POSIX character classes. By default, only ASCII characters
788: are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
789: classify characters. More details are given in the section on
790: .\" HTML <a href="pcre.html#genericchartypes">
791: .\" </a>
792: generic character types
793: .\"
794: in the
795: .\" HREF
796: \fBpcrepattern\fP
797: .\"
798: page. If you set PCRE_UCP, matching one of the items it affects takes much
799: longer. The option is available only if PCRE has been compiled with Unicode
800: property support.
801: .sp
802: PCRE_UNGREEDY
803: .sp
804: This option inverts the "greediness" of the quantifiers so that they are not
805: greedy by default, but become greedy if followed by "?". It is not compatible
806: with Perl. It can also be set by a (?U) option setting within the pattern.
807: .sp
808: PCRE_UTF8
809: .sp
810: This option causes PCRE to regard both the pattern and the subject as strings
1.1.1.2 ! misho 811: of UTF-8 characters instead of single-byte strings. However, it is available
! 812: only when PCRE is built to include UTF support. If not, the use of this option
! 813: provokes an error. Details of how this option changes the behaviour of PCRE are
! 814: given in the
1.1 misho 815: .\" HREF
816: \fBpcreunicode\fP
817: .\"
818: page.
819: .sp
820: PCRE_NO_UTF8_CHECK
821: .sp
1.1.1.2 ! misho 822: When PCRE_UTF8 is set, the validity of the pattern as a UTF-8
! 823: string is automatically checked. There is a discussion about the
! 824: .\" HTML <a href="pcreunicode.html#utf8strings">
1.1 misho 825: .\" </a>
826: validity of UTF-8 strings
827: .\"
1.1.1.2 ! misho 828: in the
1.1 misho 829: .\" HREF
1.1.1.2 ! misho 830: \fBpcreunicode\fP
1.1 misho 831: .\"
1.1.1.2 ! misho 832: page. If an invalid UTF-8 sequence is found, \fBpcre_compile()\fP returns an
! 833: error. If you already know that your pattern is valid, and you want to skip
! 834: this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option.
! 835: When it is set, the effect of passing an invalid UTF-8 string as a pattern is
! 836: undefined. It may cause your program to crash. Note that this option can also
! 837: be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress the
! 838: validity checking of subject strings.
1.1 misho 839: .
840: .
841: .SH "COMPILATION ERROR CODES"
842: .rs
843: .sp
844: The following table lists the error codes than may be returned by
845: \fBpcre_compile2()\fP, along with the error messages that may be returned by
1.1.1.2 ! misho 846: both compiling functions. Note that error messages are always 8-bit ASCII
! 847: strings, even in 16-bit mode. As PCRE has developed, some error codes have
! 848: fallen out of use. To avoid confusion, they have not been re-used.
1.1 misho 849: .sp
850: 0 no error
851: 1 \e at end of pattern
852: 2 \ec at end of pattern
853: 3 unrecognized character follows \e
854: 4 numbers out of order in {} quantifier
855: 5 number too big in {} quantifier
856: 6 missing terminating ] for character class
857: 7 invalid escape sequence in character class
858: 8 range out of order in character class
859: 9 nothing to repeat
860: 10 [this code is not in use]
861: 11 internal error: unexpected repeat
862: 12 unrecognized character after (? or (?-
863: 13 POSIX named classes are supported only within a class
864: 14 missing )
865: 15 reference to non-existent subpattern
866: 16 erroffset passed as NULL
867: 17 unknown option bit(s) set
868: 18 missing ) after comment
869: 19 [this code is not in use]
870: 20 regular expression is too large
871: 21 failed to get memory
872: 22 unmatched parentheses
873: 23 internal error: code overflow
874: 24 unrecognized character after (?<
875: 25 lookbehind assertion is not fixed length
876: 26 malformed number or name after (?(
877: 27 conditional group contains more than two branches
878: 28 assertion expected after (?(
879: 29 (?R or (?[+-]digits must be followed by )
880: 30 unknown POSIX class name
881: 31 POSIX collating elements are not supported
1.1.1.2 ! misho 882: 32 this version of PCRE is compiled without UTF support
1.1 misho 883: 33 [this code is not in use]
884: 34 character value in \ex{...} sequence is too large
885: 35 invalid condition (?(0)
886: 36 \eC not allowed in lookbehind assertion
887: 37 PCRE does not support \eL, \el, \eN{name}, \eU, or \eu
888: 38 number after (?C is > 255
889: 39 closing ) for (?C expected
890: 40 recursive call could loop indefinitely
891: 41 unrecognized character after (?P
892: 42 syntax error in subpattern name (missing terminator)
893: 43 two named subpatterns have the same name
1.1.1.2 ! misho 894: 44 invalid UTF-8 string (specifically UTF-8)
1.1 misho 895: 45 support for \eP, \ep, and \eX has not been compiled
896: 46 malformed \eP or \ep sequence
897: 47 unknown property name after \eP or \ep
898: 48 subpattern name is too long (maximum 32 characters)
899: 49 too many named subpatterns (maximum 10000)
900: 50 [this code is not in use]
1.1.1.2 ! misho 901: 51 octal value is greater than \e377 in 8-bit non-UTF-8 mode
1.1 misho 902: 52 internal error: overran compiling workspace
903: 53 internal error: previously-checked referenced subpattern
904: not found
905: 54 DEFINE group contains more than one branch
906: 55 repeating a DEFINE group is not allowed
907: 56 inconsistent NEWLINE options
908: 57 \eg is not followed by a braced, angle-bracketed, or quoted
909: name/number or by a plain number
910: 58 a numbered reference must not be zero
911: 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
912: 60 (*VERB) not recognized
913: 61 number is too big
914: 62 subpattern name expected
915: 63 digit expected after (?+
916: 64 ] is an invalid data character in JavaScript compatibility mode
917: 65 different names for subpatterns of the same number are
918: not allowed
919: 66 (*MARK) must have an argument
1.1.1.2 ! misho 920: 67 this version of PCRE is not compiled with Unicode property
! 921: support
1.1 misho 922: 68 \ec must be followed by an ASCII character
923: 69 \ek is not followed by a braced, angle-bracketed, or quoted name
1.1.1.2 ! misho 924: 70 internal error: unknown opcode in find_fixedlength()
! 925: 71 \eN is not supported in a class
! 926: 72 too many forward references
! 927: 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
! 928: 74 invalid UTF-16 string (specifically UTF-16)
1.1 misho 929: .sp
930: The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
931: be used if the limits were changed when PCRE was built.
932: .
933: .
934: .\" HTML <a name="studyingapattern"></a>
935: .SH "STUDYING A PATTERN"
936: .rs
937: .sp
938: .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
939: .ti +5n
940: .B const char **\fIerrptr\fP);
941: .PP
942: If a compiled pattern is going to be used several times, it is worth spending
943: more time analyzing it in order to speed up the time taken for matching. The
944: function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
945: argument. If studying the pattern produces additional information that will
946: help speed up matching, \fBpcre_study()\fP returns a pointer to a
947: \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
948: results of the study.
949: .P
950: The returned value from \fBpcre_study()\fP can be passed directly to
951: \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
952: also contains other fields that can be set by the caller before the block is
953: passed; these are described
954: .\" HTML <a href="#extradata">
955: .\" </a>
956: below
957: .\"
958: in the section on matching a pattern.
959: .P
960: If studying the pattern does not produce any useful information,
961: \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
962: wants to pass any of the other fields to \fBpcre_exec()\fP or
963: \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
964: .P
965: The second argument of \fBpcre_study()\fP contains option bits. There is only
966: one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-time
967: compiler is available, the pattern is further compiled into machine code that
968: executes much faster than the \fBpcre_exec()\fP matching function. If
969: the just-in-time compiler is not available, this option is ignored. All other
970: bits in the \fIoptions\fP argument must be zero.
971: .P
972: JIT compilation is a heavyweight optimization. It can take some time for
973: patterns to be analyzed, and for one-off matches and simple patterns the
974: benefit of faster execution might be offset by a much slower study time.
975: Not all patterns can be optimized by the JIT compiler. For those that cannot be
976: handled, matching automatically falls back to the \fBpcre_exec()\fP
977: interpreter. For more details, see the
978: .\" HREF
979: \fBpcrejit\fP
980: .\"
981: documentation.
982: .P
983: The third argument for \fBpcre_study()\fP is a pointer for an error message. If
984: studying succeeds (even if no data is returned), the variable it points to is
985: set to NULL. Otherwise it is set to point to a textual error message. This is a
986: static string that is part of the library. You must not try to free it. You
987: should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
988: sure that it has run successfully.
989: .P
990: When you are finished with a pattern, you can free the memory used for the
991: study data by calling \fBpcre_free_study()\fP. This function was added to the
992: API for release 8.20. For earlier versions, the memory could be freed with
993: \fBpcre_free()\fP, just like the pattern itself. This will still work in cases
994: where PCRE_STUDY_JIT_COMPILE is not used, but it is advisable to change to the
995: new function when convenient.
996: .P
997: This is a typical way in which \fBpcre_study\fP() is used (except that in a
998: real application there should be tests for errors):
999: .sp
1000: int rc;
1001: pcre *re;
1002: pcre_extra *sd;
1003: re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1004: sd = pcre_study(
1005: re, /* result of pcre_compile() */
1006: 0, /* no options */
1007: &error); /* set to NULL or points to a message */
1008: rc = pcre_exec( /* see below for details of pcre_exec() options */
1009: re, sd, "subject", 7, 0, 0, ovector, 30);
1010: ...
1011: pcre_free_study(sd);
1012: pcre_free(re);
1013: .sp
1014: Studying a pattern does two things: first, a lower bound for the length of
1015: subject string that is needed to match the pattern is computed. This does not
1016: mean that there are any strings of that length that match, but it does
1017: guarantee that no shorter strings match. The value is used by
1018: \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
1019: match strings that are shorter than the lower bound. You can find out the value
1020: in a calling program via the \fBpcre_fullinfo()\fP function.
1021: .P
1022: Studying a pattern is also useful for non-anchored patterns that do not have a
1023: single fixed starting character. A bitmap of possible starting bytes is
1024: created. This speeds up finding a position in the subject at which to start
1.1.1.2 ! misho 1025: matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256.)
1.1 misho 1026: .P
1027: These two optimizations apply to both \fBpcre_exec()\fP and
1028: \fBpcre_dfa_exec()\fP. However, they are not used by \fBpcre_exec()\fP if
1029: \fBpcre_study()\fP is called with the PCRE_STUDY_JIT_COMPILE option, and
1030: just-in-time compiling is successful. The optimizations can be disabled by
1031: setting the PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
1032: \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
1033: callouts or (*MARK) (which cannot be handled by the JIT compiler), and you want
1034: to make use of these facilities in cases where matching fails. See the
1035: discussion of PCRE_NO_START_OPTIMIZE
1036: .\" HTML <a href="#execoptions">
1037: .\" </a>
1038: below.
1039: .\"
1040: .
1041: .
1042: .\" HTML <a name="localesupport"></a>
1043: .SH "LOCALE SUPPORT"
1044: .rs
1045: .sp
1046: PCRE handles caseless matching, and determines whether characters are letters,
1047: digits, or whatever, by reference to a set of tables, indexed by character
1.1.1.2 ! misho 1048: value. When running in UTF-8 mode, this applies only to characters
! 1049: with codes less than 128. By default, higher-valued codes never match escapes
! 1050: such as \ew or \ed, but they can be tested with \ep if PCRE is built with
! 1051: Unicode character property support. Alternatively, the PCRE_UCP option can be
! 1052: set at compile time; this causes \ew and friends to use Unicode property
! 1053: support instead of built-in tables. The use of locales with Unicode is
! 1054: discouraged. If you are handling characters with codes greater than 128, you
! 1055: should either use UTF-8 and Unicode, or use locales, but not try to mix the
! 1056: two.
1.1 misho 1057: .P
1058: PCRE contains an internal set of tables that are used when the final argument
1059: of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
1060: Normally, the internal tables recognize only ASCII characters. However, when
1061: PCRE is built, it is possible to cause the internal tables to be rebuilt in the
1062: default "C" locale of the local system, which may cause them to be different.
1063: .P
1064: The internal tables can always be overridden by tables supplied by the
1065: application that calls PCRE. These may be created in a different locale from
1066: the default. As more and more applications change to using Unicode, the need
1067: for this locale support is expected to die away.
1068: .P
1069: External tables are built by calling the \fBpcre_maketables()\fP function,
1070: which has no arguments, in the relevant locale. The result can then be passed
1071: to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
1072: example, to build and use tables that are appropriate for the French locale
1073: (where accented characters with values greater than 128 are treated as letters),
1074: the following code could be used:
1075: .sp
1076: setlocale(LC_CTYPE, "fr_FR");
1077: tables = pcre_maketables();
1078: re = pcre_compile(..., tables);
1079: .sp
1080: The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
1081: are using Windows, the name for the French locale is "french".
1082: .P
1083: When \fBpcre_maketables()\fP runs, the tables are built in memory that is
1084: obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
1085: that the memory containing the tables remains available for as long as it is
1086: needed.
1087: .P
1088: The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
1089: pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
1090: and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
1091: pattern, compilation, studying and matching all happen in the same locale, but
1092: different patterns can be compiled in different locales.
1093: .P
1094: It is possible to pass a table pointer or NULL (indicating the use of the
1095: internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
1096: this facility could be used to match a pattern in a different locale from the
1097: one in which it was compiled. Passing table pointers at run time is discussed
1098: below in the section on matching a pattern.
1099: .
1100: .
1101: .\" HTML <a name="infoaboutpattern"></a>
1102: .SH "INFORMATION ABOUT A PATTERN"
1103: .rs
1104: .sp
1105: .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1106: .ti +5n
1107: .B int \fIwhat\fP, void *\fIwhere\fP);
1108: .PP
1109: The \fBpcre_fullinfo()\fP function returns information about a compiled
1.1.1.2 ! misho 1110: pattern. It replaces the \fBpcre_info()\fP function, which was removed from the
! 1111: library at version 8.30, after more than 10 years of obsolescence.
1.1 misho 1112: .P
1113: The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
1114: pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
1115: the pattern was not studied. The third argument specifies which piece of
1116: information is required, and the fourth argument is a pointer to a variable
1117: to receive the data. The yield of the function is zero for success, or one of
1118: the following negative numbers:
1119: .sp
1.1.1.2 ! misho 1120: PCRE_ERROR_NULL the argument \fIcode\fP was NULL
! 1121: the argument \fIwhere\fP was NULL
! 1122: PCRE_ERROR_BADMAGIC the "magic number" was not found
! 1123: PCRE_ERROR_BADENDIANNESS the pattern was compiled with different
! 1124: endianness
! 1125: PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
1.1 misho 1126: .sp
1127: The "magic number" is placed at the start of each compiled pattern as an simple
1.1.1.2 ! misho 1128: check against passing an arbitrary memory pointer. The endianness error can
! 1129: occur if a compiled pattern is saved and reloaded on a different host. Here is
! 1130: a typical call of \fBpcre_fullinfo()\fP, to obtain the length of the compiled
! 1131: pattern:
1.1 misho 1132: .sp
1133: int rc;
1134: size_t length;
1135: rc = pcre_fullinfo(
1136: re, /* result of pcre_compile() */
1137: sd, /* result of pcre_study(), or NULL */
1138: PCRE_INFO_SIZE, /* what is required */
1139: &length); /* where to put the data */
1140: .sp
1141: The possible values for the third argument are defined in \fBpcre.h\fP, and are
1142: as follows:
1143: .sp
1144: PCRE_INFO_BACKREFMAX
1145: .sp
1146: Return the number of the highest back reference in the pattern. The fourth
1147: argument should point to an \fBint\fP variable. Zero is returned if there are
1148: no back references.
1149: .sp
1150: PCRE_INFO_CAPTURECOUNT
1151: .sp
1152: Return the number of capturing subpatterns in the pattern. The fourth argument
1153: should point to an \fBint\fP variable.
1154: .sp
1155: PCRE_INFO_DEFAULT_TABLES
1156: .sp
1157: Return a pointer to the internal default character tables within PCRE. The
1158: fourth argument should point to an \fBunsigned char *\fP variable. This
1159: information call is provided for internal use by the \fBpcre_study()\fP
1160: function. External callers can cause PCRE to use its internal tables by passing
1161: a NULL table pointer.
1162: .sp
1163: PCRE_INFO_FIRSTBYTE
1164: .sp
1.1.1.2 ! misho 1165: Return information about the first data unit of any matched string, for a
! 1166: non-anchored pattern. (The name of this option refers to the 8-bit library,
! 1167: where data units are bytes.) The fourth argument should point to an \fBint\fP
! 1168: variable.
! 1169: .P
! 1170: If there is a fixed first value, for example, the letter "c" from a pattern
! 1171: such as (cat|cow|coyote), its value is returned. In the 8-bit library, the
! 1172: value is always less than 256; in the 16-bit library the value can be up to
! 1173: 0xffff.
1.1 misho 1174: .P
1.1.1.2 ! misho 1175: If there is no fixed first value, and if either
1.1 misho 1176: .sp
1177: (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1178: starts with "^", or
1179: .sp
1180: (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1181: (if it were set, the pattern would be anchored),
1182: .sp
1183: -1 is returned, indicating that the pattern matches only at the start of a
1184: subject string or after any newline within the string. Otherwise -2 is
1185: returned. For anchored patterns, -2 is returned.
1186: .sp
1187: PCRE_INFO_FIRSTTABLE
1188: .sp
1189: If the pattern was studied, and this resulted in the construction of a 256-bit
1.1.1.2 ! misho 1190: table indicating a fixed set of values for the first data unit in any matching
1.1 misho 1191: string, a pointer to the table is returned. Otherwise NULL is returned. The
1192: fourth argument should point to an \fBunsigned char *\fP variable.
1193: .sp
1194: PCRE_INFO_HASCRORLF
1195: .sp
1196: Return 1 if the pattern contains any explicit matches for CR or LF characters,
1197: otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1198: explicit match is either a literal CR or LF character, or \er or \en.
1199: .sp
1200: PCRE_INFO_JCHANGED
1201: .sp
1202: Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1203: 0. The fourth argument should point to an \fBint\fP variable. (?J) and
1204: (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1205: .sp
1206: PCRE_INFO_JIT
1207: .sp
1208: Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE option, and
1209: just-in-time compiling was successful. The fourth argument should point to an
1210: \fBint\fP variable. A return value of 0 means that JIT support is not available
1211: in this version of PCRE, or that the pattern was not studied with the
1212: PCRE_STUDY_JIT_COMPILE option, or that the JIT compiler could not handle this
1213: particular pattern. See the
1214: .\" HREF
1215: \fBpcrejit\fP
1216: .\"
1217: documentation for details of what can and cannot be handled.
1218: .sp
1219: PCRE_INFO_JITSIZE
1220: .sp
1221: If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1222: return the size of the JIT compiled code, otherwise return zero. The fourth
1223: argument should point to a \fBsize_t\fP variable.
1224: .sp
1225: PCRE_INFO_LASTLITERAL
1226: .sp
1.1.1.2 ! misho 1227: Return the value of the rightmost literal data unit that must exist in any
! 1228: matched string, other than at its start, if such a value has been recorded. The
! 1229: fourth argument should point to an \fBint\fP variable. If there is no such
! 1230: value, -1 is returned. For anchored patterns, a last literal value is recorded
! 1231: only if it follows something of variable length. For example, for the pattern
1.1 misho 1232: /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1233: is -1.
1234: .sp
1235: PCRE_INFO_MINLENGTH
1236: .sp
1237: If the pattern was studied and a minimum length for matching subject strings
1238: was computed, its value is returned. Otherwise the returned value is -1. The
1.1.1.2 ! misho 1239: value is a number of characters, which in UTF-8 mode may be different from the
! 1240: number of bytes. The fourth argument should point to an \fBint\fP variable. A
1.1 misho 1241: non-negative value is a lower bound to the length of any matching string. There
1242: may not be any strings of that length that do actually match, but every string
1243: that does match is at least that long.
1244: .sp
1245: PCRE_INFO_NAMECOUNT
1246: PCRE_INFO_NAMEENTRYSIZE
1247: PCRE_INFO_NAMETABLE
1248: .sp
1249: PCRE supports the use of named as well as numbered capturing parentheses. The
1250: names are just an additional way of identifying the parentheses, which still
1251: acquire numbers. Several convenience functions such as
1252: \fBpcre_get_named_substring()\fP are provided for extracting captured
1253: substrings by name. It is also possible to extract the data directly, by first
1254: converting the name to a number in order to access the correct pointers in the
1255: output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1256: you need to use the name-to-number map, which is described by these three
1257: values.
1258: .P
1259: The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1260: the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1261: entry; both of these return an \fBint\fP value. The entry size depends on the
1262: length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1.1.1.2 ! misho 1263: entry of the table. This is a pointer to \fBchar\fP in the 8-bit library, where
! 1264: the first two bytes of each entry are the number of the capturing parenthesis,
! 1265: most significant byte first. In the 16-bit library, the pointer points to
! 1266: 16-bit data units, the first of which contains the parenthesis number. The rest
! 1267: of the entry is the corresponding name, zero terminated.
1.1 misho 1268: .P
1269: The names are in alphabetical order. Duplicate names may appear if (?| is used
1270: to create multiple groups with the same number, as described in the
1271: .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1272: .\" </a>
1273: section on duplicate subpattern numbers
1274: .\"
1275: in the
1276: .\" HREF
1277: \fBpcrepattern\fP
1278: .\"
1279: page. Duplicate names for subpatterns with different numbers are permitted only
1280: if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1281: table in the order in which they were found in the pattern. In the absence of
1282: (?| this is the order of increasing number; when (?| is used this is not
1283: necessarily the case because later subpatterns may have lower numbers.
1284: .P
1285: As a simple example of the name/number table, consider the following pattern
1.1.1.2 ! misho 1286: after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white
! 1287: space - including newlines - is ignored):
1.1 misho 1288: .sp
1289: .\" JOIN
1290: (?<date> (?<year>(\ed\ed)?\ed\ed) -
1291: (?<month>\ed\ed) - (?<day>\ed\ed) )
1292: .sp
1293: There are four named subpatterns, so the table has four entries, and each entry
1294: in the table is eight bytes long. The table is as follows, with non-printing
1295: bytes shows in hexadecimal, and undefined bytes shown as ??:
1296: .sp
1297: 00 01 d a t e 00 ??
1298: 00 05 d a y 00 ?? ??
1299: 00 04 m o n t h 00
1300: 00 02 y e a r 00 ??
1301: .sp
1302: When writing code to extract data from named subpatterns using the
1303: name-to-number map, remember that the length of the entries is likely to be
1304: different for each compiled pattern.
1305: .sp
1306: PCRE_INFO_OKPARTIAL
1307: .sp
1308: Return 1 if the pattern can be used for partial matching with
1309: \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1310: \fBint\fP variable. From release 8.00, this always returns 1, because the
1311: restrictions that previously applied to partial matching have been lifted. The
1312: .\" HREF
1313: \fBpcrepartial\fP
1314: .\"
1315: documentation gives details of partial matching.
1316: .sp
1317: PCRE_INFO_OPTIONS
1318: .sp
1319: Return a copy of the options with which the pattern was compiled. The fourth
1320: argument should point to an \fBunsigned long int\fP variable. These option bits
1321: are those specified in the call to \fBpcre_compile()\fP, modified by any
1322: top-level option settings at the start of the pattern itself. In other words,
1323: they are the options that will be in force when matching starts. For example,
1324: if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1325: result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1326: .P
1327: A pattern is automatically anchored by PCRE if all of its top-level
1328: alternatives begin with one of the following:
1329: .sp
1330: ^ unless PCRE_MULTILINE is set
1331: \eA always
1332: \eG always
1333: .\" JOIN
1334: .* if PCRE_DOTALL is set and there are no back
1335: references to the subpattern in which .* appears
1336: .sp
1337: For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1338: \fBpcre_fullinfo()\fP.
1339: .sp
1340: PCRE_INFO_SIZE
1341: .sp
1.1.1.2 ! misho 1342: Return the size of the compiled pattern in bytes (for both libraries). The
! 1343: fourth argument should point to a \fBsize_t\fP variable. This value does not
! 1344: include the size of the \fBpcre\fP structure that is returned by
! 1345: \fBpcre_compile()\fP. The value that is passed as the argument to
! 1346: \fBpcre_malloc()\fP when \fBpcre_compile()\fP is getting memory in which to
! 1347: place the compiled data is the value returned by this option plus the size of
! 1348: the \fBpcre\fP structure. Studying a compiled pattern, with or without JIT,
! 1349: does not alter the value returned by this option.
1.1 misho 1350: .sp
1351: PCRE_INFO_STUDYSIZE
1352: .sp
1.1.1.2 ! misho 1353: Return the size in bytes of the data block pointed to by the \fIstudy_data\fP
! 1354: field in a \fBpcre_extra\fP block. If \fBpcre_extra\fP is NULL, or there is no
! 1355: study data, zero is returned. The fourth argument should point to a
! 1356: \fBsize_t\fP variable. The \fIstudy_data\fP field is set by \fBpcre_study()\fP
! 1357: to record information that will speed up matching (see the section entitled
1.1 misho 1358: .\" HTML <a href="#studyingapattern">
1359: .\" </a>
1360: "Studying a pattern"
1361: .\"
1362: above). The format of the \fIstudy_data\fP block is private, but its length
1363: is made available via this option so that it can be saved and restored (see the
1364: .\" HREF
1365: \fBpcreprecompile\fP
1366: .\"
1367: documentation for details).
1368: .
1369: .
1370: .SH "REFERENCE COUNTS"
1371: .rs
1372: .sp
1373: .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1374: .PP
1375: The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1376: data block that contains a compiled pattern. It is provided for the benefit of
1377: applications that operate in an object-oriented manner, where different parts
1378: of the application may be using the same compiled pattern, but you want to free
1379: the block when they are all done.
1380: .P
1381: When a pattern is compiled, the reference count field is initialized to zero.
1382: It is changed only by calling this function, whose action is to add the
1383: \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1384: function is the new value. However, the value of the count is constrained to
1385: lie between 0 and 65535, inclusive. If the new value is outside these limits,
1386: it is forced to the appropriate limit value.
1387: .P
1388: Except when it is zero, the reference count is not correctly preserved if a
1389: pattern is compiled on one host and then transferred to a host whose byte-order
1390: is different. (This seems a highly unlikely scenario.)
1391: .
1392: .
1393: .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1394: .rs
1395: .sp
1396: .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1397: .ti +5n
1398: .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1399: .ti +5n
1400: .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1401: .P
1402: The function \fBpcre_exec()\fP is called to match a subject string against a
1403: compiled pattern, which is passed in the \fIcode\fP argument. If the
1404: pattern was studied, the result of the study should be passed in the
1405: \fIextra\fP argument. You can call \fBpcre_exec()\fP with the same \fIcode\fP
1406: and \fIextra\fP arguments as many times as you like, in order to match
1407: different subject strings with the same pattern.
1408: .P
1409: This function is the main matching facility of the library, and it operates in
1410: a Perl-like manner. For specialist use there is also an alternative matching
1411: function, which is described
1412: .\" HTML <a href="#dfamatch">
1413: .\" </a>
1414: below
1415: .\"
1416: in the section about the \fBpcre_dfa_exec()\fP function.
1417: .P
1418: In most applications, the pattern will have been compiled (and optionally
1419: studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1420: possible to save compiled patterns and study data, and then use them later
1421: in different processes, possibly even on different hosts. For a discussion
1422: about this, see the
1423: .\" HREF
1424: \fBpcreprecompile\fP
1425: .\"
1426: documentation.
1427: .P
1428: Here is an example of a simple call to \fBpcre_exec()\fP:
1429: .sp
1430: int rc;
1431: int ovector[30];
1432: rc = pcre_exec(
1433: re, /* result of pcre_compile() */
1434: NULL, /* we didn't study the pattern */
1435: "some string", /* the subject string */
1436: 11, /* the length of the subject string */
1437: 0, /* start at offset 0 in the subject */
1438: 0, /* default options */
1439: ovector, /* vector of integers for substring information */
1440: 30); /* number of elements (NOT size in bytes) */
1441: .
1442: .
1443: .\" HTML <a name="extradata"></a>
1444: .SS "Extra data for \fBpcre_exec()\fR"
1445: .rs
1446: .sp
1447: If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1448: data block. The \fBpcre_study()\fP function returns such a block (when it
1449: doesn't return NULL), but you can also create one for yourself, and pass
1450: additional information in it. The \fBpcre_extra\fP block contains the following
1451: fields (not necessarily in this order):
1452: .sp
1453: unsigned long int \fIflags\fP;
1454: void *\fIstudy_data\fP;
1455: void *\fIexecutable_jit\fP;
1456: unsigned long int \fImatch_limit\fP;
1457: unsigned long int \fImatch_limit_recursion\fP;
1458: void *\fIcallout_data\fP;
1459: const unsigned char *\fItables\fP;
1460: unsigned char **\fImark\fP;
1461: .sp
1.1.1.2 ! misho 1462: In the 16-bit version of this structure, the \fImark\fP field has type
! 1463: "PCRE_UCHAR16 **".
! 1464: .P
1.1 misho 1465: The \fIflags\fP field is a bitmap that specifies which of the other fields
1466: are set. The flag bits are:
1467: .sp
1468: PCRE_EXTRA_STUDY_DATA
1469: PCRE_EXTRA_EXECUTABLE_JIT
1470: PCRE_EXTRA_MATCH_LIMIT
1471: PCRE_EXTRA_MATCH_LIMIT_RECURSION
1472: PCRE_EXTRA_CALLOUT_DATA
1473: PCRE_EXTRA_TABLES
1474: PCRE_EXTRA_MARK
1475: .sp
1476: Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes
1477: the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is
1478: returned by \fBpcre_study()\fP, together with the appropriate flag bits. You
1479: should not set these yourself, but you may add to the block by setting the
1480: other fields and their corresponding flag bits.
1481: .P
1482: The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1483: vast amount of resources when running patterns that are not going to match,
1484: but which have a very large number of possibilities in their search trees. The
1485: classic example is a pattern that uses nested unlimited repeats.
1486: .P
1487: Internally, \fBpcre_exec()\fP uses a function called \fBmatch()\fP, which it
1488: calls repeatedly (sometimes recursively). The limit set by \fImatch_limit\fP is
1489: imposed on the number of times this function is called during a match, which
1490: has the effect of limiting the amount of backtracking that can take place. For
1491: patterns that are not anchored, the count restarts from zero for each position
1492: in the subject string.
1493: .P
1494: When \fBpcre_exec()\fP is called with a pattern that was successfully studied
1495: with the PCRE_STUDY_JIT_COMPILE option, the way that the matching is executed
1496: is entirely different. However, there is still the possibility of runaway
1497: matching that goes on for a very long time, and so the \fImatch_limit\fP value
1498: is also used in this case (but in a different way) to limit how long the
1499: matching can continue.
1500: .P
1501: The default value for the limit can be set when PCRE is built; the default
1502: default is 10 million, which handles all but the most extreme cases. You can
1503: override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1504: block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1505: the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1506: PCRE_ERROR_MATCHLIMIT.
1507: .P
1508: The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1509: instead of limiting the total number of times that \fBmatch()\fP is called, it
1510: limits the depth of recursion. The recursion depth is a smaller number than the
1511: total number of calls, because not all calls to \fBmatch()\fP are recursive.
1512: This limit is of use only if it is set smaller than \fImatch_limit\fP.
1513: .P
1514: Limiting the recursion depth limits the amount of machine stack that can be
1515: used, or, when PCRE has been compiled to use memory on the heap instead of the
1516: stack, the amount of heap memory that can be used. This limit is not relevant,
1517: and is ignored, if the pattern was successfully studied with
1518: PCRE_STUDY_JIT_COMPILE.
1519: .P
1520: The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1521: built; the default default is the same value as the default for
1522: \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1523: with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1524: PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1525: is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1526: .P
1527: The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1528: and is described in the
1529: .\" HREF
1530: \fBpcrecallout\fP
1531: .\"
1532: documentation.
1533: .P
1534: The \fItables\fP field is used to pass a character tables pointer to
1535: \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1536: pattern. A non-NULL value is stored with the compiled pattern only if custom
1537: tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1538: If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1539: internal tables to be used. This facility is helpful when re-using patterns
1540: that have been saved after compiling with an external set of tables, because
1541: the external tables might be at a different address when \fBpcre_exec()\fP is
1542: called. See the
1543: .\" HREF
1544: \fBpcreprecompile\fP
1545: .\"
1546: documentation for a discussion of saving compiled patterns for later use.
1547: .P
1548: If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1.1.1.2 ! misho 1549: be set to point to a suitable variable. If the pattern contains any
1.1 misho 1550: backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1551: a name to pass back, a pointer to the name string (zero terminated) is placed
1552: in the variable pointed to by the \fImark\fP field. The names are within the
1553: compiled pattern; if you wish to retain such a name you must copy it before
1554: freeing the memory of a compiled pattern. If there is no name to pass back, the
1.1.1.2 ! misho 1555: variable pointed to by the \fImark\fP field is set to NULL. For details of the
1.1 misho 1556: backtracking control verbs, see the section entitled
1557: .\" HTML <a href="pcrepattern#backtrackcontrol">
1558: .\" </a>
1559: "Backtracking control"
1560: .\"
1561: in the
1562: .\" HREF
1563: \fBpcrepattern\fP
1564: .\"
1565: documentation.
1566: .
1567: .
1568: .\" HTML <a name="execoptions"></a>
1569: .SS "Option bits for \fBpcre_exec()\fP"
1570: .rs
1571: .sp
1572: The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1573: zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1574: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1575: PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1576: PCRE_PARTIAL_HARD.
1577: .P
1578: If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1579: the only supported options for JIT execution are PCRE_NO_UTF8_CHECK,
1580: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NOTEMPTY_ATSTART. Note in
1581: particular that partial matching is not supported. If an unsupported option is
1582: used, JIT execution is disabled and the normal interpretive code in
1583: \fBpcre_exec()\fP is run.
1584: .sp
1585: PCRE_ANCHORED
1586: .sp
1587: The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1588: matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1589: to be anchored by virtue of its contents, it cannot be made unachored at
1590: matching time.
1591: .sp
1592: PCRE_BSR_ANYCRLF
1593: PCRE_BSR_UNICODE
1594: .sp
1595: These options (which are mutually exclusive) control what the \eR escape
1596: sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1597: match any Unicode newline sequence. These options override the choice that was
1598: made or defaulted when the pattern was compiled.
1599: .sp
1600: PCRE_NEWLINE_CR
1601: PCRE_NEWLINE_LF
1602: PCRE_NEWLINE_CRLF
1603: PCRE_NEWLINE_ANYCRLF
1604: PCRE_NEWLINE_ANY
1605: .sp
1606: These options override the newline definition that was chosen or defaulted when
1607: the pattern was compiled. For details, see the description of
1608: \fBpcre_compile()\fP above. During matching, the newline choice affects the
1609: behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1610: the way the match position is advanced after a match failure for an unanchored
1611: pattern.
1612: .P
1613: When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1614: match attempt for an unanchored pattern fails when the current position is at a
1615: CRLF sequence, and the pattern contains no explicit matches for CR or LF
1616: characters, the match position is advanced by two characters instead of one, in
1617: other words, to after the CRLF.
1618: .P
1619: The above rule is a compromise that makes the most common cases work as
1620: expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1621: set), it does not match the string "\er\enA" because, after failing at the
1622: start, it skips both the CR and the LF before retrying. However, the pattern
1623: [\er\en]A does match that string, because it contains an explicit CR or LF
1624: reference, and so advances only by one character after the first failure.
1625: .P
1626: An explicit match for CR of LF is either a literal appearance of one of those
1627: characters, or one of the \er or \en escape sequences. Implicit matches such as
1628: [^X] do not count, nor does \es (which includes CR and LF in the characters
1629: that it matches).
1630: .P
1631: Notwithstanding the above, anomalous effects may still occur when CRLF is a
1632: valid newline sequence and explicit \er or \en escapes appear in the pattern.
1633: .sp
1634: PCRE_NOTBOL
1635: .sp
1636: This option specifies that first character of the subject string is not the
1637: beginning of a line, so the circumflex metacharacter should not match before
1638: it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1639: never to match. This option affects only the behaviour of the circumflex
1640: metacharacter. It does not affect \eA.
1641: .sp
1642: PCRE_NOTEOL
1643: .sp
1644: This option specifies that the end of the subject string is not the end of a
1645: line, so the dollar metacharacter should not match it nor (except in multiline
1646: mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1647: compile time) causes dollar never to match. This option affects only the
1648: behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1649: .sp
1650: PCRE_NOTEMPTY
1651: .sp
1652: An empty string is not considered to be a valid match if this option is set. If
1653: there are alternatives in the pattern, they are tried. If all the alternatives
1654: match the empty string, the entire match fails. For example, if the pattern
1655: .sp
1656: a?b?
1657: .sp
1658: is applied to a string not beginning with "a" or "b", it matches an empty
1659: string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1660: valid, so PCRE searches further into the string for occurrences of "a" or "b".
1661: .sp
1662: PCRE_NOTEMPTY_ATSTART
1663: .sp
1664: This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1665: the start of the subject is permitted. If the pattern is anchored, such a match
1666: can occur only if the pattern contains \eK.
1667: .P
1668: Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1669: does make a special case of a pattern match of the empty string within its
1670: \fBsplit()\fP function, and when using the /g modifier. It is possible to
1671: emulate Perl's behaviour after matching a null string by first trying the match
1672: again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1673: if that fails, by advancing the starting offset (see below) and trying an
1674: ordinary match again. There is some code that demonstrates how to do this in
1675: the
1676: .\" HREF
1677: \fBpcredemo\fP
1678: .\"
1679: sample program. In the most general case, you have to check to see if the
1680: newline convention recognizes CRLF as a newline, and if so, and the current
1681: character is CR followed by LF, advance the starting offset by two characters
1682: instead of one.
1683: .sp
1684: PCRE_NO_START_OPTIMIZE
1685: .sp
1686: There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1687: a match, in order to speed up the process. For example, if it is known that an
1688: unanchored match must start with a specific character, it searches the subject
1689: for that character, and fails immediately if it cannot find it, without
1690: actually running the main matching function. This means that a special item
1691: such as (*COMMIT) at the start of a pattern is not considered until after a
1692: suitable starting point for the match has been found. When callouts or (*MARK)
1693: items are in use, these "start-up" optimizations can cause them to be skipped
1694: if the pattern is never actually used. The start-up optimizations are in effect
1695: a pre-scan of the subject that takes place before the pattern is run.
1696: .P
1697: The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1698: causing performance to suffer, but ensuring that in cases where the result is
1699: "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1700: are considered at every possible starting position in the subject string. If
1701: PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1702: time.
1703: .P
1704: Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1705: Consider the pattern
1706: .sp
1707: (*COMMIT)ABC
1708: .sp
1709: When this is compiled, PCRE records the fact that a match must start with the
1710: character "A". Suppose the subject string is "DEFABC". The start-up
1711: optimization scans along the subject, finds "A" and runs the first match
1712: attempt from there. The (*COMMIT) item means that the pattern must match the
1713: current starting position, which in this case, it does. However, if the same
1714: match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1715: subject string does not happen. The first match attempt is run starting from
1716: "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1717: the overall result is "no match". If the pattern is studied, more start-up
1718: optimizations may be used. For example, a minimum length for the subject may be
1719: recorded. Consider the pattern
1720: .sp
1721: (*MARK:A)(X|Y)
1722: .sp
1723: The minimum length for a match is one character. If the subject is "ABC", there
1724: will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1725: If the pattern is studied, the final attempt does not take place, because PCRE
1726: knows that the subject is too short, and so the (*MARK) is never encountered.
1727: In this case, studying the pattern does not affect the overall match result,
1728: which is still "no match", but it does affect the auxiliary information that is
1729: returned.
1730: .sp
1731: PCRE_NO_UTF8_CHECK
1732: .sp
1733: When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1734: string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1735: The value of \fIstartoffset\fP is also checked to ensure that it points to the
1736: start of a UTF-8 character. There is a discussion about the validity of UTF-8
1737: strings in the
1738: .\" HREF
1.1.1.2 ! misho 1739: \fBpcreunicode\fP
1.1 misho 1740: .\"
1.1.1.2 ! misho 1741: page. If an invalid sequence of bytes is found, \fBpcre_exec()\fP returns the
! 1742: error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
! 1743: truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both
! 1744: cases, information about the precise nature of the error may also be returned
! 1745: (see the descriptions of these errors in the section entitled \fIError return
! 1746: values from\fP \fBpcre_exec()\fP
1.1 misho 1747: .\" HTML <a href="#errorlist">
1748: .\" </a>
1749: below).
1750: .\"
1751: If \fIstartoffset\fP contains a value that does not point to the start of a
1752: UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1753: returned.
1754: .P
1755: If you already know that your subject is valid, and you want to skip these
1756: checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1757: calling \fBpcre_exec()\fP. You might want to do this for the second and
1758: subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1759: all the matches in a single subject string. However, you should be sure that
1.1.1.2 ! misho 1760: the value of \fIstartoffset\fP points to the start of a character (or the end
! 1761: of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
! 1762: invalid string as a subject or an invalid value of \fIstartoffset\fP is
1.1 misho 1763: undefined. Your program may crash.
1764: .sp
1765: PCRE_PARTIAL_HARD
1766: PCRE_PARTIAL_SOFT
1767: .sp
1768: These options turn on the partial matching feature. For backwards
1769: compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1770: occurs if the end of the subject string is reached successfully, but there are
1771: not enough subject characters to complete the match. If this happens when
1772: PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1773: testing any remaining alternatives. Only if no complete match can be found is
1774: PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1775: PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1776: but only if no complete match can be found.
1777: .P
1778: If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1779: partial match is found, \fBpcre_exec()\fP immediately returns
1780: PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1781: when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1782: important that an alternative complete match.
1783: .P
1784: In both cases, the portion of the string that was inspected when the partial
1785: match was found is set as the first matching string. There is a more detailed
1786: discussion of partial and multi-segment matching, with examples, in the
1787: .\" HREF
1788: \fBpcrepartial\fP
1789: .\"
1790: documentation.
1791: .
1792: .
1793: .SS "The string to be matched by \fBpcre_exec()\fP"
1794: .rs
1795: .sp
1796: The subject string is passed to \fBpcre_exec()\fP as a pointer in
1.1.1.2 ! misho 1797: \fIsubject\fP, a length in bytes in \fIlength\fP, and a starting byte offset
1.1 misho 1798: in \fIstartoffset\fP. If this is negative or greater than the length of the
1799: subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1800: offset is zero, the search for a match starts at the beginning of the subject,
1801: and this is by far the most common case. In UTF-8 mode, the byte offset must
1802: point to the start of a UTF-8 character (or the end of the subject). Unlike the
1803: pattern string, the subject may contain binary zero bytes.
1804: .P
1805: A non-zero starting offset is useful when searching for another match in the
1806: same subject by calling \fBpcre_exec()\fP again after a previous success.
1807: Setting \fIstartoffset\fP differs from just passing over a shortened string and
1808: setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1809: lookbehind. For example, consider the pattern
1810: .sp
1811: \eBiss\eB
1812: .sp
1813: which finds occurrences of "iss" in the middle of words. (\eB matches only if
1814: the current position in the subject is not a word boundary.) When applied to
1815: the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1816: occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1817: subject, namely "issipi", it does not match, because \eB is always false at the
1818: start of the subject, which is deemed to be a word boundary. However, if
1819: \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1820: set to 4, it finds the second occurrence of "iss" because it is able to look
1821: behind the starting point to discover that it is preceded by a letter.
1822: .P
1823: Finding all the matches in a subject is tricky when the pattern can match an
1824: empty string. It is possible to emulate Perl's /g behaviour by first trying the
1825: match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1826: PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1827: and trying an ordinary match again. There is some code that demonstrates how to
1828: do this in the
1829: .\" HREF
1830: \fBpcredemo\fP
1831: .\"
1832: sample program. In the most general case, you have to check to see if the
1833: newline convention recognizes CRLF as a newline, and if so, and the current
1834: character is CR followed by LF, advance the starting offset by two characters
1835: instead of one.
1836: .P
1837: If a non-zero starting offset is passed when the pattern is anchored, one
1838: attempt to match at the given offset is made. This can only succeed if the
1839: pattern does not require the match to be at the start of the subject.
1840: .
1841: .
1842: .SS "How \fBpcre_exec()\fP returns captured substrings"
1843: .rs
1844: .sp
1845: In general, a pattern matches a certain portion of the subject, and in
1846: addition, further substrings from the subject may be picked out by parts of the
1847: pattern. Following the usage in Jeffrey Friedl's book, this is called
1848: "capturing" in what follows, and the phrase "capturing subpattern" is used for
1849: a fragment of a pattern that picks out a substring. PCRE supports several other
1850: kinds of parenthesized subpattern that do not cause substrings to be captured.
1851: .P
1852: Captured substrings are returned to the caller via a vector of integers whose
1853: address is passed in \fIovector\fP. The number of elements in the vector is
1854: passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1855: argument is NOT the size of \fIovector\fP in bytes.
1856: .P
1857: The first two-thirds of the vector is used to pass back captured substrings,
1858: each substring using a pair of integers. The remaining third of the vector is
1859: used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1860: and is not available for passing back information. The number passed in
1861: \fIovecsize\fP should always be a multiple of three. If it is not, it is
1862: rounded down.
1863: .P
1864: When a match is successful, information about captured substrings is returned
1865: in pairs of integers, starting at the beginning of \fIovector\fP, and
1866: continuing up to two-thirds of its length at the most. The first element of
1867: each pair is set to the byte offset of the first character in a substring, and
1868: the second is set to the byte offset of the first character after the end of a
1869: substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1870: mode. They are not character counts.
1871: .P
1872: The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1873: portion of the subject string matched by the entire pattern. The next pair is
1874: used for the first capturing subpattern, and so on. The value returned by
1875: \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1876: For example, if two substrings have been captured, the returned value is 3. If
1877: there are no capturing subpatterns, the return value from a successful match is
1878: 1, indicating that just the first pair of offsets has been set.
1879: .P
1880: If a capturing subpattern is matched repeatedly, it is the last portion of the
1881: string that it matched that is returned.
1882: .P
1883: If the vector is too small to hold all the captured substring offsets, it is
1884: used as far as possible (up to two-thirds of its length), and the function
1885: returns a value of zero. If neither the actual string matched not any captured
1886: substrings are of interest, \fBpcre_exec()\fP may be called with \fIovector\fP
1887: passed as NULL and \fIovecsize\fP as zero. However, if the pattern contains
1888: back references and the \fIovector\fP is not big enough to remember the related
1889: substrings, PCRE has to get additional memory for use during matching. Thus it
1890: is usually advisable to supply an \fIovector\fP of reasonable size.
1891: .P
1892: There are some cases where zero is returned (indicating vector overflow) when
1893: in fact the vector is exactly the right size for the final match. For example,
1894: consider the pattern
1895: .sp
1896: (a)(?:(b)c|bd)
1897: .sp
1898: If a vector of 6 elements (allowing for only 1 captured substring) is given
1899: with subject string "abd", \fBpcre_exec()\fP will try to set the second
1900: captured string, thereby recording a vector overflow, before failing to match
1901: "c" and backing up to try the second alternative. The zero return, however,
1902: does correctly indicate that the maximum number of slots (namely 2) have been
1903: filled. In similar cases where there is temporary overflow, but the final
1904: number of used slots is actually less than the maximum, a non-zero value is
1905: returned.
1906: .P
1907: The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1908: subpatterns there are in a compiled pattern. The smallest size for
1909: \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1910: the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1911: .P
1912: It is possible for capturing subpattern number \fIn+1\fP to match some part of
1913: the subject when subpattern \fIn\fP has not been used at all. For example, if
1914: the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1915: function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1916: happens, both values in the offset pairs corresponding to unused subpatterns
1917: are set to -1.
1918: .P
1919: Offset values that correspond to unused subpatterns at the end of the
1920: expression are also set to -1. For example, if the string "abc" is matched
1921: against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1922: return from the function is 2, because the highest used capturing subpattern
1923: number is 1, and the offsets for for the second and third capturing subpatterns
1924: (assuming the vector is large enough, of course) are set to -1.
1925: .P
1926: \fBNote\fP: Elements in the first two-thirds of \fIovector\fP that do not
1927: correspond to capturing parentheses in the pattern are never changed. That is,
1928: if a pattern contains \fIn\fP capturing parentheses, no more than
1929: \fIovector[0]\fP to \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other
1930: elements (in the first two-thirds) retain whatever values they previously had.
1931: .P
1932: Some convenience functions are provided for extracting the captured substrings
1933: as separate strings. These are described below.
1934: .
1935: .
1936: .\" HTML <a name="errorlist"></a>
1937: .SS "Error return values from \fBpcre_exec()\fP"
1938: .rs
1939: .sp
1940: If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1941: defined in the header file:
1942: .sp
1943: PCRE_ERROR_NOMATCH (-1)
1944: .sp
1945: The subject string did not match the pattern.
1946: .sp
1947: PCRE_ERROR_NULL (-2)
1948: .sp
1949: Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1950: NULL and \fIovecsize\fP was not zero.
1951: .sp
1952: PCRE_ERROR_BADOPTION (-3)
1953: .sp
1954: An unrecognized bit was set in the \fIoptions\fP argument.
1955: .sp
1956: PCRE_ERROR_BADMAGIC (-4)
1957: .sp
1958: PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1959: the case when it is passed a junk pointer and to detect when a pattern that was
1960: compiled in an environment of one endianness is run in an environment with the
1961: other endianness. This is the error that PCRE gives when the magic number is
1962: not present.
1963: .sp
1964: PCRE_ERROR_UNKNOWN_OPCODE (-5)
1965: .sp
1966: While running the pattern match, an unknown item was encountered in the
1967: compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1968: of the compiled pattern.
1969: .sp
1970: PCRE_ERROR_NOMEMORY (-6)
1971: .sp
1972: If a pattern contains back references, but the \fIovector\fP that is passed to
1973: \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1974: gets a block of memory at the start of matching to use for this purpose. If the
1975: call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1976: automatically freed at the end of matching.
1977: .P
1978: This error is also given if \fBpcre_stack_malloc()\fP fails in
1979: \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1980: \fB--disable-stack-for-recursion\fP.
1981: .sp
1982: PCRE_ERROR_NOSUBSTRING (-7)
1983: .sp
1984: This error is used by the \fBpcre_copy_substring()\fP,
1985: \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1986: below). It is never returned by \fBpcre_exec()\fP.
1987: .sp
1988: PCRE_ERROR_MATCHLIMIT (-8)
1989: .sp
1990: The backtracking limit, as specified by the \fImatch_limit\fP field in a
1991: \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1992: above.
1993: .sp
1994: PCRE_ERROR_CALLOUT (-9)
1995: .sp
1996: This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1997: use by callout functions that want to yield a distinctive error code. See the
1998: .\" HREF
1999: \fBpcrecallout\fP
2000: .\"
2001: documentation for details.
2002: .sp
2003: PCRE_ERROR_BADUTF8 (-10)
2004: .sp
2005: A string that contains an invalid UTF-8 byte sequence was passed as a subject,
2006: and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
2007: (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
2008: UTF-8 character is placed in the first element, and a reason code is placed in
2009: the second element. The reason codes are listed in the
2010: .\" HTML <a href="#badutf8reasons">
2011: .\" </a>
2012: following section.
2013: .\"
2014: For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
2015: truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
2016: PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2017: .sp
2018: PCRE_ERROR_BADUTF8_OFFSET (-11)
2019: .sp
2020: The UTF-8 byte sequence that was passed as a subject was checked and found to
2021: be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
2022: \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
2023: end of the subject.
2024: .sp
2025: PCRE_ERROR_PARTIAL (-12)
2026: .sp
2027: The subject string did not match, but it did match partially. See the
2028: .\" HREF
2029: \fBpcrepartial\fP
2030: .\"
2031: documentation for details of partial matching.
2032: .sp
2033: PCRE_ERROR_BADPARTIAL (-13)
2034: .sp
2035: This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
2036: option was used with a compiled pattern containing items that were not
2037: supported for partial matching. From release 8.00 onwards, there are no
2038: restrictions on partial matching.
2039: .sp
2040: PCRE_ERROR_INTERNAL (-14)
2041: .sp
2042: An unexpected internal error has occurred. This error could be caused by a bug
2043: in PCRE or by overwriting of the compiled pattern.
2044: .sp
2045: PCRE_ERROR_BADCOUNT (-15)
2046: .sp
2047: This error is given if the value of the \fIovecsize\fP argument is negative.
2048: .sp
2049: PCRE_ERROR_RECURSIONLIMIT (-21)
2050: .sp
2051: The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
2052: field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
2053: description above.
2054: .sp
2055: PCRE_ERROR_BADNEWLINE (-23)
2056: .sp
2057: An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
2058: .sp
2059: PCRE_ERROR_BADOFFSET (-24)
2060: .sp
2061: The value of \fIstartoffset\fP was negative or greater than the length of the
2062: subject, that is, the value in \fIlength\fP.
2063: .sp
2064: PCRE_ERROR_SHORTUTF8 (-25)
2065: .sp
2066: This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2067: ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2068: Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2069: fact sufficient to detect this case, but this special error code for
2070: PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2071: retained for backwards compatibility.
2072: .sp
2073: PCRE_ERROR_RECURSELOOP (-26)
2074: .sp
2075: This error is returned when \fBpcre_exec()\fP detects a recursion loop within
2076: the pattern. Specifically, it means that either the whole pattern or a
2077: subpattern has been called recursively for the second time at the same position
2078: in the subject string. Some simple patterns that might do this are detected and
2079: faulted at compile time, but more complicated cases, in particular mutual
2080: recursions between two different subpatterns, cannot be detected until run
2081: time.
2082: .sp
2083: PCRE_ERROR_JIT_STACKLIMIT (-27)
2084: .sp
2085: This error is returned when a pattern that was successfully studied using the
2086: PCRE_STUDY_JIT_COMPILE option is being matched, but the memory available for
2087: the just-in-time processing stack is not large enough. See the
2088: .\" HREF
2089: \fBpcrejit\fP
2090: .\"
2091: documentation for more details.
1.1.1.2 ! misho 2092: .sp
! 2093: PCRE_ERROR_BADMODE (-28)
! 2094: .sp
! 2095: This error is given if a pattern that was compiled by the 8-bit library is
! 2096: passed to a 16-bit library function, or vice versa.
! 2097: .sp
! 2098: PCRE_ERROR_BADENDIANNESS (-29)
! 2099: .sp
! 2100: This error is given if a pattern that was compiled and saved is reloaded on a
! 2101: host with different endianness. The utility function
! 2102: \fBpcre_pattern_to_host_byte_order()\fP can be used to convert such a pattern
! 2103: so that it runs on the new host.
1.1 misho 2104: .P
2105: Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
2106: .
2107: .
2108: .\" HTML <a name="badutf8reasons"></a>
2109: .SS "Reason codes for invalid UTF-8 strings"
2110: .rs
2111: .sp
1.1.1.2 ! misho 2112: This section applies only to the 8-bit library. The corresponding information
! 2113: for the 16-bit library is given in the
! 2114: .\" HREF
! 2115: \fBpcre16\fP
! 2116: .\"
! 2117: page.
! 2118: .P
1.1 misho 2119: When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
2120: PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
2121: least 2, the offset of the start of the invalid UTF-8 character is placed in
2122: the first output vector element (\fIovector[0]\fP) and a reason code is placed
2123: in the second element (\fIovector[1]\fP). The reason codes are given names in
2124: the \fBpcre.h\fP header file:
2125: .sp
2126: PCRE_UTF8_ERR1
2127: PCRE_UTF8_ERR2
2128: PCRE_UTF8_ERR3
2129: PCRE_UTF8_ERR4
2130: PCRE_UTF8_ERR5
2131: .sp
2132: The string ends with a truncated UTF-8 character; the code specifies how many
2133: bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2134: no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2135: allows for up to 6 bytes, and this is checked first; hence the possibility of
2136: 4 or 5 missing bytes.
2137: .sp
2138: PCRE_UTF8_ERR6
2139: PCRE_UTF8_ERR7
2140: PCRE_UTF8_ERR8
2141: PCRE_UTF8_ERR9
2142: PCRE_UTF8_ERR10
2143: .sp
2144: The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2145: character do not have the binary value 0b10 (that is, either the most
2146: significant bit is 0, or the next bit is 1).
2147: .sp
2148: PCRE_UTF8_ERR11
2149: PCRE_UTF8_ERR12
2150: .sp
2151: A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2152: these code points are excluded by RFC 3629.
2153: .sp
2154: PCRE_UTF8_ERR13
2155: .sp
2156: A 4-byte character has a value greater than 0x10fff; these code points are
2157: excluded by RFC 3629.
2158: .sp
2159: PCRE_UTF8_ERR14
2160: .sp
2161: A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2162: code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2163: from UTF-8.
2164: .sp
2165: PCRE_UTF8_ERR15
2166: PCRE_UTF8_ERR16
2167: PCRE_UTF8_ERR17
2168: PCRE_UTF8_ERR18
2169: PCRE_UTF8_ERR19
2170: .sp
2171: A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2172: value that can be represented by fewer bytes, which is invalid. For example,
2173: the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2174: one byte.
2175: .sp
2176: PCRE_UTF8_ERR20
2177: .sp
2178: The two most significant bits of the first byte of a character have the binary
2179: value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2180: byte can only validly occur as the second or subsequent byte of a multi-byte
2181: character.
2182: .sp
2183: PCRE_UTF8_ERR21
2184: .sp
2185: The first byte of a character has the value 0xfe or 0xff. These values can
2186: never occur in a valid UTF-8 string.
2187: .
2188: .
2189: .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
2190: .rs
2191: .sp
2192: .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2193: .ti +5n
2194: .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
2195: .ti +5n
2196: .B int \fIbuffersize\fP);
2197: .PP
2198: .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2199: .ti +5n
2200: .B int \fIstringcount\fP, int \fIstringnumber\fP,
2201: .ti +5n
2202: .B const char **\fIstringptr\fP);
2203: .PP
2204: .B int pcre_get_substring_list(const char *\fIsubject\fP,
2205: .ti +5n
2206: .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
2207: .PP
2208: Captured substrings can be accessed directly by using the offsets returned by
2209: \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
2210: \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
2211: \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
2212: as new, separate, zero-terminated strings. These functions identify substrings
2213: by number. The next section describes functions for extracting named
2214: substrings.
2215: .P
2216: A substring that contains a binary zero is correctly extracted and has a
2217: further zero added on the end, but the result is not, of course, a C string.
2218: However, you can process such a string by referring to the length that is
2219: returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
2220: Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
2221: for handling strings containing binary zeros, because the end of the final
2222: string is not independently indicated.
2223: .P
2224: The first three arguments are the same for all three of these functions:
2225: \fIsubject\fP is the subject string that has just been successfully matched,
2226: \fIovector\fP is a pointer to the vector of integer offsets that was passed to
2227: \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
2228: captured by the match, including the substring that matched the entire regular
2229: expression. This is the value returned by \fBpcre_exec()\fP if it is greater
2230: than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
2231: space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
2232: number of elements in the vector divided by three.
2233: .P
2234: The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
2235: extract a single substring, whose number is given as \fIstringnumber\fP. A
2236: value of zero extracts the substring that matched the entire pattern, whereas
2237: higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
2238: the string is placed in \fIbuffer\fP, whose length is given by
2239: \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
2240: obtained via \fBpcre_malloc\fP, and its address is returned via
2241: \fIstringptr\fP. The yield of the function is the length of the string, not
2242: including the terminating zero, or one of these error codes:
2243: .sp
2244: PCRE_ERROR_NOMEMORY (-6)
2245: .sp
2246: The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
2247: memory failed for \fBpcre_get_substring()\fP.
2248: .sp
2249: PCRE_ERROR_NOSUBSTRING (-7)
2250: .sp
2251: There is no substring whose number is \fIstringnumber\fP.
2252: .P
2253: The \fBpcre_get_substring_list()\fP function extracts all available substrings
2254: and builds a list of pointers to them. All this is done in a single block of
2255: memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
2256: is returned via \fIlistptr\fP, which is also the start of the list of string
2257: pointers. The end of the list is marked by a NULL pointer. The yield of the
2258: function is zero if all went well, or the error code
2259: .sp
2260: PCRE_ERROR_NOMEMORY (-6)
2261: .sp
2262: if the attempt to get the memory block failed.
2263: .P
2264: When any of these functions encounter a substring that is unset, which can
2265: happen when capturing subpattern number \fIn+1\fP matches some part of the
2266: subject, but subpattern \fIn\fP has not been used at all, they return an empty
2267: string. This can be distinguished from a genuine zero-length substring by
2268: inspecting the appropriate offset in \fIovector\fP, which is negative for unset
2269: substrings.
2270: .P
2271: The two convenience functions \fBpcre_free_substring()\fP and
2272: \fBpcre_free_substring_list()\fP can be used to free the memory returned by
2273: a previous call of \fBpcre_get_substring()\fP or
2274: \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
2275: the function pointed to by \fBpcre_free\fP, which of course could be called
2276: directly from a C program. However, PCRE is used in some situations where it is
2277: linked via a special interface to another programming language that cannot use
2278: \fBpcre_free\fP directly; it is for these cases that the functions are
2279: provided.
2280: .
2281: .
2282: .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
2283: .rs
2284: .sp
2285: .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
2286: .ti +5n
2287: .B const char *\fIname\fP);
2288: .PP
2289: .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
2290: .ti +5n
2291: .B const char *\fIsubject\fP, int *\fIovector\fP,
2292: .ti +5n
2293: .B int \fIstringcount\fP, const char *\fIstringname\fP,
2294: .ti +5n
2295: .B char *\fIbuffer\fP, int \fIbuffersize\fP);
2296: .PP
2297: .B int pcre_get_named_substring(const pcre *\fIcode\fP,
2298: .ti +5n
2299: .B const char *\fIsubject\fP, int *\fIovector\fP,
2300: .ti +5n
2301: .B int \fIstringcount\fP, const char *\fIstringname\fP,
2302: .ti +5n
2303: .B const char **\fIstringptr\fP);
2304: .PP
2305: To extract a substring by name, you first have to find associated number.
2306: For example, for this pattern
2307: .sp
2308: (a+)b(?<xxx>\ed+)...
2309: .sp
2310: the number of the subpattern called "xxx" is 2. If the name is known to be
2311: unique (PCRE_DUPNAMES was not set), you can find the number from the name by
2312: calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
2313: pattern, and the second is the name. The yield of the function is the
2314: subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2315: that name.
2316: .P
2317: Given the number, you can extract the substring directly, or use one of the
2318: functions described in the previous section. For convenience, there are also
2319: two functions that do the whole job.
2320: .P
2321: Most of the arguments of \fBpcre_copy_named_substring()\fP and
2322: \fBpcre_get_named_substring()\fP are the same as those for the similarly named
2323: functions that extract by number. As these are described in the previous
2324: section, they are not re-described here. There are just two differences:
2325: .P
2326: First, instead of a substring number, a substring name is given. Second, there
2327: is an extra argument, given at the start, which is a pointer to the compiled
2328: pattern. This is needed in order to gain access to the name-to-number
2329: translation table.
2330: .P
2331: These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
2332: then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
2333: appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
2334: the behaviour may not be what you want (see the next section).
2335: .P
2336: \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
2337: subpatterns with the same number, as described in the
2338: .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
2339: .\" </a>
2340: section on duplicate subpattern numbers
2341: .\"
2342: in the
2343: .\" HREF
2344: \fBpcrepattern\fP
2345: .\"
2346: page, you cannot use names to distinguish the different subpatterns, because
2347: names are not included in the compiled code. The matching process uses only
2348: numbers. For this reason, the use of different names for subpatterns of the
2349: same number causes an error at compile time.
2350: .
2351: .
2352: .SH "DUPLICATE SUBPATTERN NAMES"
2353: .rs
2354: .sp
2355: .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
2356: .ti +5n
2357: .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2358: .PP
2359: When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2360: are not required to be unique. (Duplicate names are always allowed for
2361: subpatterns with the same number, created by using the (?| feature. Indeed, if
2362: such subpatterns are named, they are required to use the same names.)
2363: .P
2364: Normally, patterns with duplicate names are such that in any one match, only
2365: one of the named subpatterns participates. An example is shown in the
2366: .\" HREF
2367: \fBpcrepattern\fP
2368: .\"
2369: documentation.
2370: .P
2371: When duplicates are present, \fBpcre_copy_named_substring()\fP and
2372: \fBpcre_get_named_substring()\fP return the first substring corresponding to
2373: the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2374: returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2375: returns one of the numbers that are associated with the name, but it is not
2376: defined which it is.
2377: .P
2378: If you want to get full details of all captured substrings for a given name,
2379: you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2380: argument is the compiled pattern, and the second is the name. The third and
2381: fourth are pointers to variables which are updated by the function. After it
2382: has run, they point to the first and last entries in the name-to-number table
2383: for the given name. The function itself returns the length of each entry, or
2384: PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2385: described above in the section entitled \fIInformation about a pattern\fP
2386: .\" HTML <a href="#infoaboutpattern">
2387: .\" </a>
2388: above.
2389: .\"
2390: Given all the relevant entries for the name, you can extract each of their
2391: numbers, and hence the captured data, if any.
2392: .
2393: .
2394: .SH "FINDING ALL POSSIBLE MATCHES"
2395: .rs
2396: .sp
2397: The traditional matching function uses a similar algorithm to Perl, which stops
2398: when it finds the first match, starting at a given point in the subject. If you
2399: want to find all possible matches, or the longest possible match, consider
2400: using the alternative matching function (see below) instead. If you cannot use
2401: the alternative function, but still need to find all possible matches, you
2402: can kludge it up by making use of the callout facility, which is described in
2403: the
2404: .\" HREF
2405: \fBpcrecallout\fP
2406: .\"
2407: documentation.
2408: .P
2409: What you have to do is to insert a callout right at the end of the pattern.
2410: When your callout function is called, extract and save the current matched
2411: substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2412: other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2413: will yield PCRE_ERROR_NOMATCH.
2414: .
2415: .
1.1.1.2 ! misho 2416: .SH "OBTAINING AN ESTIMATE OF STACK USAGE"
! 2417: .rs
! 2418: .sp
! 2419: Matching certain patterns using \fBpcre_exec()\fP can use a lot of process
! 2420: stack, which in certain environments can be rather limited in size. Some users
! 2421: find it helpful to have an estimate of the amount of stack that is used by
! 2422: \fBpcre_exec()\fP, to help them set recursion limits, as described in the
! 2423: .\" HREF
! 2424: \fBpcrestack\fP
! 2425: .\"
! 2426: documentation. The estimate that is output by \fBpcretest\fP when called with
! 2427: the \fB-m\fP and \fB-C\fP options is obtained by calling \fBpcre_exec\fP with
! 2428: the values NULL, NULL, NULL, -999, and -999 for its first five arguments.
! 2429: .P
! 2430: Normally, if its first argument is NULL, \fBpcre_exec()\fP immediately returns
! 2431: the negative error code PCRE_ERROR_NULL, but with this special combination of
! 2432: arguments, it returns instead a negative number whose absolute value is the
! 2433: approximate stack frame size in bytes. (A negative number is used so that it is
! 2434: clear that no match has happened.) The value is approximate because in some
! 2435: cases, recursive calls to \fBpcre_exec()\fP occur when there are one or two
! 2436: additional variables on the stack.
! 2437: .P
! 2438: If PCRE has been compiled to use the heap instead of the stack for recursion,
! 2439: the value returned is the size of each block that is obtained from the heap.
! 2440: .
! 2441: .
1.1 misho 2442: .\" HTML <a name="dfamatch"></a>
2443: .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
2444: .rs
2445: .sp
2446: .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2447: .ti +5n
2448: .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2449: .ti +5n
2450: .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2451: .ti +5n
2452: .B int *\fIworkspace\fP, int \fIwscount\fP);
2453: .P
2454: The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2455: a compiled pattern, using a matching algorithm that scans the subject string
2456: just once, and does not backtrack. This has different characteristics to the
2457: normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2458: patterns are not supported. Nevertheless, there are times when this kind of
2459: matching can be useful. For a discussion of the two matching algorithms, and a
2460: list of features that \fBpcre_dfa_exec()\fP does not support, see the
2461: .\" HREF
2462: \fBpcrematching\fP
2463: .\"
2464: documentation.
2465: .P
2466: The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2467: \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2468: different way, and this is described below. The other common arguments are used
2469: in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2470: here.
2471: .P
2472: The two additional arguments provide workspace for the function. The workspace
2473: vector should contain at least 20 elements. It is used for keeping track of
2474: multiple paths through the pattern tree. More workspace will be needed for
2475: patterns and subjects where there are a lot of potential matches.
2476: .P
2477: Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2478: .sp
2479: int rc;
2480: int ovector[10];
2481: int wspace[20];
2482: rc = pcre_dfa_exec(
2483: re, /* result of pcre_compile() */
2484: NULL, /* we didn't study the pattern */
2485: "some string", /* the subject string */
2486: 11, /* the length of the subject string */
2487: 0, /* start at offset 0 in the subject */
2488: 0, /* default options */
2489: ovector, /* vector of integers for substring information */
2490: 10, /* number of elements (NOT size in bytes) */
2491: wspace, /* working space vector */
2492: 20); /* number of elements (NOT size in bytes) */
2493: .
2494: .SS "Option bits for \fBpcre_dfa_exec()\fP"
2495: .rs
2496: .sp
2497: The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2498: zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2499: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2500: PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2501: PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2502: All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2503: so their description is not repeated here.
2504: .sp
2505: PCRE_PARTIAL_HARD
2506: PCRE_PARTIAL_SOFT
2507: .sp
2508: These have the same general effect as they do for \fBpcre_exec()\fP, but the
2509: details are slightly different. When PCRE_PARTIAL_HARD is set for
2510: \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2511: is reached and there is still at least one matching possibility that requires
2512: additional characters. This happens even if some complete matches have also
2513: been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2514: is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2515: there have been no complete matches, but there is still at least one matching
2516: possibility. The portion of the string that was inspected when the longest
2517: partial match was found is set as the first matching string in both cases.
2518: There is a more detailed discussion of partial and multi-segment matching, with
2519: examples, in the
2520: .\" HREF
2521: \fBpcrepartial\fP
2522: .\"
2523: documentation.
2524: .sp
2525: PCRE_DFA_SHORTEST
2526: .sp
2527: Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2528: soon as it has found one match. Because of the way the alternative algorithm
2529: works, this is necessarily the shortest possible match at the first possible
2530: matching point in the subject string.
2531: .sp
2532: PCRE_DFA_RESTART
2533: .sp
2534: When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2535: again, with additional subject characters, and have it continue with the same
2536: match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2537: \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2538: before because data about the match so far is left in them after a partial
2539: match. There is more discussion of this facility in the
2540: .\" HREF
2541: \fBpcrepartial\fP
2542: .\"
2543: documentation.
2544: .
2545: .
2546: .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2547: .rs
2548: .sp
2549: When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2550: substring in the subject. Note, however, that all the matches from one run of
2551: the function start at the same point in the subject. The shorter matches are
2552: all initial substrings of the longer matches. For example, if the pattern
2553: .sp
2554: <.*>
2555: .sp
2556: is matched against the string
2557: .sp
2558: This is <something> <something else> <something further> no more
2559: .sp
2560: the three matched strings are
2561: .sp
2562: <something>
2563: <something> <something else>
2564: <something> <something else> <something further>
2565: .sp
2566: On success, the yield of the function is a number greater than zero, which is
2567: the number of matched substrings. The substrings themselves are returned in
2568: \fIovector\fP. Each string uses two elements; the first is the offset to the
2569: start, and the second is the offset to the end. In fact, all the strings have
2570: the same start offset. (Space could have been saved by giving this only once,
2571: but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2572: returns data, even though the meaning of the strings is different.)
2573: .P
2574: The strings are returned in reverse order of length; that is, the longest
2575: matching string is given first. If there were too many matches to fit into
2576: \fIovector\fP, the yield of the function is zero, and the vector is filled with
2577: the longest matches. Unlike \fBpcre_exec()\fP, \fBpcre_dfa_exec()\fP can use
2578: the entire \fIovector\fP for returning matched strings.
2579: .
2580: .
2581: .SS "Error returns from \fBpcre_dfa_exec()\fP"
2582: .rs
2583: .sp
2584: The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2585: Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2586: described
2587: .\" HTML <a href="#errorlist">
2588: .\" </a>
2589: above.
2590: .\"
2591: There are in addition the following errors that are specific to
2592: \fBpcre_dfa_exec()\fP:
2593: .sp
2594: PCRE_ERROR_DFA_UITEM (-16)
2595: .sp
2596: This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2597: that it does not support, for instance, the use of \eC or a back reference.
2598: .sp
2599: PCRE_ERROR_DFA_UCOND (-17)
2600: .sp
2601: This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2602: uses a back reference for the condition, or a test for recursion in a specific
2603: group. These are not supported.
2604: .sp
2605: PCRE_ERROR_DFA_UMLIMIT (-18)
2606: .sp
2607: This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2608: block that contains a setting of the \fImatch_limit\fP or
2609: \fImatch_limit_recursion\fP fields. This is not supported (these fields are
2610: meaningless for DFA matching).
2611: .sp
2612: PCRE_ERROR_DFA_WSSIZE (-19)
2613: .sp
2614: This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2615: \fIworkspace\fP vector.
2616: .sp
2617: PCRE_ERROR_DFA_RECURSE (-20)
2618: .sp
2619: When a recursive subpattern is processed, the matching function calls itself
2620: recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2621: error is given if the output vector is not large enough. This should be
2622: extremely rare, as a vector of size 1000 is used.
2623: .
2624: .
2625: .SH "SEE ALSO"
2626: .rs
2627: .sp
1.1.1.2 ! misho 2628: \fBpcre16\fP(3), \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
1.1 misho 2629: \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
2630: \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
2631: .
2632: .
2633: .SH AUTHOR
2634: .rs
2635: .sp
2636: .nf
2637: Philip Hazel
2638: University Computing Service
2639: Cambridge CB2 3QH, England.
2640: .fi
2641: .
2642: .
2643: .SH REVISION
2644: .rs
2645: .sp
2646: .nf
1.1.1.2 ! misho 2647: Last updated: 21 January 2012
! 2648: Copyright (c) 1997-2012 University of Cambridge.
1.1 misho 2649: .fi
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