Annotation of embedaddon/pcre/doc/html/pcreapi.html, revision 1.1.1.2
1.1 misho 1: <html>
2: <head>
3: <title>pcreapi specification</title>
4: </head>
5: <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6: <h1>pcreapi man page</h1>
7: <p>
8: Return to the <a href="index.html">PCRE index page</a>.
9: </p>
10: <p>
11: This page is part of the PCRE HTML documentation. It was generated automatically
12: from the original man page. If there is any nonsense in it, please consult the
13: man page, in case the conversion went wrong.
14: <br>
15: <ul>
16: <li><a name="TOC1" href="#SEC1">PCRE NATIVE API BASIC FUNCTIONS</a>
1.1.1.2 ! misho 17: <li><a name="TOC2" href="#SEC2">PCRE NATIVE API STRING EXTRACTION FUNCTIONS</a>
! 18: <li><a name="TOC3" href="#SEC3">PCRE NATIVE API AUXILIARY FUNCTIONS</a>
! 19: <li><a name="TOC4" href="#SEC4">PCRE NATIVE API INDIRECTED FUNCTIONS</a>
! 20: <li><a name="TOC5" href="#SEC5">PCRE 8-BIT AND 16-BIT LIBRARIES</a>
! 21: <li><a name="TOC6" href="#SEC6">PCRE API OVERVIEW</a>
! 22: <li><a name="TOC7" href="#SEC7">NEWLINES</a>
! 23: <li><a name="TOC8" href="#SEC8">MULTITHREADING</a>
! 24: <li><a name="TOC9" href="#SEC9">SAVING PRECOMPILED PATTERNS FOR LATER USE</a>
! 25: <li><a name="TOC10" href="#SEC10">CHECKING BUILD-TIME OPTIONS</a>
! 26: <li><a name="TOC11" href="#SEC11">COMPILING A PATTERN</a>
! 27: <li><a name="TOC12" href="#SEC12">COMPILATION ERROR CODES</a>
! 28: <li><a name="TOC13" href="#SEC13">STUDYING A PATTERN</a>
! 29: <li><a name="TOC14" href="#SEC14">LOCALE SUPPORT</a>
! 30: <li><a name="TOC15" href="#SEC15">INFORMATION ABOUT A PATTERN</a>
! 31: <li><a name="TOC16" href="#SEC16">REFERENCE COUNTS</a>
! 32: <li><a name="TOC17" href="#SEC17">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a>
! 33: <li><a name="TOC18" href="#SEC18">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a>
! 34: <li><a name="TOC19" href="#SEC19">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a>
! 35: <li><a name="TOC20" href="#SEC20">DUPLICATE SUBPATTERN NAMES</a>
! 36: <li><a name="TOC21" href="#SEC21">FINDING ALL POSSIBLE MATCHES</a>
! 37: <li><a name="TOC22" href="#SEC22">OBTAINING AN ESTIMATE OF STACK USAGE</a>
! 38: <li><a name="TOC23" href="#SEC23">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a>
! 39: <li><a name="TOC24" href="#SEC24">SEE ALSO</a>
! 40: <li><a name="TOC25" href="#SEC25">AUTHOR</a>
! 41: <li><a name="TOC26" href="#SEC26">REVISION</a>
1.1 misho 42: </ul>
43: <P>
44: <b>#include <pcre.h></b>
45: </P>
1.1.1.2 ! misho 46: <br><a name="SEC1" href="#TOC1">PCRE NATIVE API BASIC FUNCTIONS</a><br>
1.1 misho 47: <P>
48: <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
49: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
50: <b>const unsigned char *<i>tableptr</i>);</b>
51: </P>
52: <P>
53: <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
54: <b>int *<i>errorcodeptr</i>,</b>
55: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
56: <b>const unsigned char *<i>tableptr</i>);</b>
57: </P>
58: <P>
59: <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
60: <b>const char **<i>errptr</i>);</b>
61: </P>
62: <P>
63: <b>void pcre_free_study(pcre_extra *<i>extra</i>);</b>
64: </P>
65: <P>
66: <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
67: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
68: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
69: </P>
70: <P>
71: <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
72: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
73: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
74: <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
75: </P>
1.1.1.2 ! misho 76: <br><a name="SEC2" href="#TOC1">PCRE NATIVE API STRING EXTRACTION FUNCTIONS</a><br>
1.1 misho 77: <P>
78: <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
79: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
80: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
81: <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
82: </P>
83: <P>
84: <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
85: <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
86: <b>int <i>buffersize</i>);</b>
87: </P>
88: <P>
89: <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
90: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
91: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
92: <b>const char **<i>stringptr</i>);</b>
93: </P>
94: <P>
95: <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
96: <b>const char *<i>name</i>);</b>
97: </P>
98: <P>
99: <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
100: <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
101: </P>
102: <P>
103: <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
104: <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
105: <b>const char **<i>stringptr</i>);</b>
106: </P>
107: <P>
108: <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
109: <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
110: </P>
111: <P>
112: <b>void pcre_free_substring(const char *<i>stringptr</i>);</b>
113: </P>
114: <P>
115: <b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b>
116: </P>
1.1.1.2 ! misho 117: <br><a name="SEC3" href="#TOC1">PCRE NATIVE API AUXILIARY FUNCTIONS</a><br>
! 118: <P>
! 119: <b>pcre_jit_stack *pcre_jit_stack_alloc(int <i>startsize</i>, int <i>maxsize</i>);</b>
! 120: </P>
! 121: <P>
! 122: <b>void pcre_jit_stack_free(pcre_jit_stack *<i>stack</i>);</b>
! 123: </P>
! 124: <P>
! 125: <b>void pcre_assign_jit_stack(pcre_extra *<i>extra</i>,</b>
! 126: <b>pcre_jit_callback <i>callback</i>, void *<i>data</i>);</b>
! 127: </P>
1.1 misho 128: <P>
129: <b>const unsigned char *pcre_maketables(void);</b>
130: </P>
131: <P>
132: <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
133: <b>int <i>what</i>, void *<i>where</i>);</b>
134: </P>
135: <P>
136: <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
137: </P>
138: <P>
139: <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
140: </P>
141: <P>
1.1.1.2 ! misho 142: <b>const char *pcre_version(void);</b>
1.1 misho 143: </P>
1.1.1.2 ! misho 144: <P>
! 145: <b>int pcre_pattern_to_host_byte_order(pcre *<i>code</i>,</b>
! 146: <b>pcre_extra *<i>extra</i>, const unsigned char *<i>tables</i>);</b>
! 147: </P>
! 148: <br><a name="SEC4" href="#TOC1">PCRE NATIVE API INDIRECTED FUNCTIONS</a><br>
1.1 misho 149: <P>
150: <b>void *(*pcre_malloc)(size_t);</b>
151: </P>
152: <P>
153: <b>void (*pcre_free)(void *);</b>
154: </P>
155: <P>
156: <b>void *(*pcre_stack_malloc)(size_t);</b>
157: </P>
158: <P>
159: <b>void (*pcre_stack_free)(void *);</b>
160: </P>
161: <P>
162: <b>int (*pcre_callout)(pcre_callout_block *);</b>
163: </P>
1.1.1.2 ! misho 164: <br><a name="SEC5" href="#TOC1">PCRE 8-BIT AND 16-BIT LIBRARIES</a><br>
! 165: <P>
! 166: From release 8.30, PCRE can be compiled as a library for handling 16-bit
! 167: character strings as well as, or instead of, the original library that handles
! 168: 8-bit character strings. To avoid too much complication, this document
! 169: describes the 8-bit versions of the functions, with only occasional references
! 170: to the 16-bit library.
! 171: </P>
! 172: <P>
! 173: The 16-bit functions operate in the same way as their 8-bit counterparts; they
! 174: just use different data types for their arguments and results, and their names
! 175: start with <b>pcre16_</b> instead of <b>pcre_</b>. For every option that has UTF8
! 176: in its name (for example, PCRE_UTF8), there is a corresponding 16-bit name with
! 177: UTF8 replaced by UTF16. This facility is in fact just cosmetic; the 16-bit
! 178: option names define the same bit values.
! 179: </P>
! 180: <P>
! 181: References to bytes and UTF-8 in this document should be read as references to
! 182: 16-bit data quantities and UTF-16 when using the 16-bit library, unless
! 183: specified otherwise. More details of the specific differences for the 16-bit
! 184: library are given in the
! 185: <a href="pcre16.html"><b>pcre16</b></a>
! 186: page.
! 187: </P>
! 188: <br><a name="SEC6" href="#TOC1">PCRE API OVERVIEW</a><br>
1.1 misho 189: <P>
190: PCRE has its own native API, which is described in this document. There are
1.1.1.2 ! misho 191: also some wrapper functions (for the 8-bit library only) that correspond to the
! 192: POSIX regular expression API, but they do not give access to all the
! 193: functionality. They are described in the
1.1 misho 194: <a href="pcreposix.html"><b>pcreposix</b></a>
195: documentation. Both of these APIs define a set of C function calls. A C++
1.1.1.2 ! misho 196: wrapper (again for the 8-bit library only) is also distributed with PCRE. It is
! 197: documented in the
1.1 misho 198: <a href="pcrecpp.html"><b>pcrecpp</b></a>
199: page.
200: </P>
201: <P>
202: The native API C function prototypes are defined in the header file
1.1.1.2 ! misho 203: <b>pcre.h</b>, and on Unix-like systems the (8-bit) library itself is called
! 204: <b>libpcre</b>. It can normally be accessed by adding <b>-lpcre</b> to the
! 205: command for linking an application that uses PCRE. The header file defines the
! 206: macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers
! 207: for the library. Applications can use these to include support for different
! 208: releases of PCRE.
1.1 misho 209: </P>
210: <P>
211: In a Windows environment, if you want to statically link an application program
212: against a non-dll <b>pcre.a</b> file, you must define PCRE_STATIC before
213: including <b>pcre.h</b> or <b>pcrecpp.h</b>, because otherwise the
214: <b>pcre_malloc()</b> and <b>pcre_free()</b> exported functions will be declared
215: <b>__declspec(dllimport)</b>, with unwanted results.
216: </P>
217: <P>
218: The functions <b>pcre_compile()</b>, <b>pcre_compile2()</b>, <b>pcre_study()</b>,
219: and <b>pcre_exec()</b> are used for compiling and matching regular expressions
220: in a Perl-compatible manner. A sample program that demonstrates the simplest
221: way of using them is provided in the file called <i>pcredemo.c</i> in the PCRE
222: source distribution. A listing of this program is given in the
223: <a href="pcredemo.html"><b>pcredemo</b></a>
224: documentation, and the
225: <a href="pcresample.html"><b>pcresample</b></a>
226: documentation describes how to compile and run it.
227: </P>
228: <P>
229: Just-in-time compiler support is an optional feature of PCRE that can be built
230: in appropriate hardware environments. It greatly speeds up the matching
231: performance of many patterns. Simple programs can easily request that it be
232: used if available, by setting an option that is ignored when it is not
233: relevant. More complicated programs might need to make use of the functions
234: <b>pcre_jit_stack_alloc()</b>, <b>pcre_jit_stack_free()</b>, and
235: <b>pcre_assign_jit_stack()</b> in order to control the JIT code's memory usage.
236: These functions are discussed in the
237: <a href="pcrejit.html"><b>pcrejit</b></a>
238: documentation.
239: </P>
240: <P>
241: A second matching function, <b>pcre_dfa_exec()</b>, which is not
242: Perl-compatible, is also provided. This uses a different algorithm for the
243: matching. The alternative algorithm finds all possible matches (at a given
244: point in the subject), and scans the subject just once (unless there are
245: lookbehind assertions). However, this algorithm does not return captured
246: substrings. A description of the two matching algorithms and their advantages
247: and disadvantages is given in the
248: <a href="pcrematching.html"><b>pcrematching</b></a>
249: documentation.
250: </P>
251: <P>
252: In addition to the main compiling and matching functions, there are convenience
253: functions for extracting captured substrings from a subject string that is
254: matched by <b>pcre_exec()</b>. They are:
255: <pre>
256: <b>pcre_copy_substring()</b>
257: <b>pcre_copy_named_substring()</b>
258: <b>pcre_get_substring()</b>
259: <b>pcre_get_named_substring()</b>
260: <b>pcre_get_substring_list()</b>
261: <b>pcre_get_stringnumber()</b>
262: <b>pcre_get_stringtable_entries()</b>
263: </pre>
264: <b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also
265: provided, to free the memory used for extracted strings.
266: </P>
267: <P>
268: The function <b>pcre_maketables()</b> is used to build a set of character tables
269: in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>,
270: or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for
271: specialist use. Most commonly, no special tables are passed, in which case
272: internal tables that are generated when PCRE is built are used.
273: </P>
274: <P>
275: The function <b>pcre_fullinfo()</b> is used to find out information about a
1.1.1.2 ! misho 276: compiled pattern. The function <b>pcre_version()</b> returns a pointer to a
! 277: string containing the version of PCRE and its date of release.
1.1 misho 278: </P>
279: <P>
280: The function <b>pcre_refcount()</b> maintains a reference count in a data block
281: containing a compiled pattern. This is provided for the benefit of
282: object-oriented applications.
283: </P>
284: <P>
285: The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain
286: the entry points of the standard <b>malloc()</b> and <b>free()</b> functions,
287: respectively. PCRE calls the memory management functions via these variables,
288: so a calling program can replace them if it wishes to intercept the calls. This
289: should be done before calling any PCRE functions.
290: </P>
291: <P>
292: The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also
293: indirections to memory management functions. These special functions are used
294: only when PCRE is compiled to use the heap for remembering data, instead of
295: recursive function calls, when running the <b>pcre_exec()</b> function. See the
296: <a href="pcrebuild.html"><b>pcrebuild</b></a>
297: documentation for details of how to do this. It is a non-standard way of
298: building PCRE, for use in environments that have limited stacks. Because of the
299: greater use of memory management, it runs more slowly. Separate functions are
300: provided so that special-purpose external code can be used for this case. When
301: used, these functions are always called in a stack-like manner (last obtained,
302: first freed), and always for memory blocks of the same size. There is a
303: discussion about PCRE's stack usage in the
304: <a href="pcrestack.html"><b>pcrestack</b></a>
305: documentation.
306: </P>
307: <P>
308: The global variable <b>pcre_callout</b> initially contains NULL. It can be set
309: by the caller to a "callout" function, which PCRE will then call at specified
310: points during a matching operation. Details are given in the
311: <a href="pcrecallout.html"><b>pcrecallout</b></a>
312: documentation.
313: <a name="newlines"></a></P>
1.1.1.2 ! misho 314: <br><a name="SEC7" href="#TOC1">NEWLINES</a><br>
1.1 misho 315: <P>
316: PCRE supports five different conventions for indicating line breaks in
317: strings: a single CR (carriage return) character, a single LF (linefeed)
318: character, the two-character sequence CRLF, any of the three preceding, or any
319: Unicode newline sequence. The Unicode newline sequences are the three just
320: mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
321: U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
322: (paragraph separator, U+2029).
323: </P>
324: <P>
325: Each of the first three conventions is used by at least one operating system as
326: its standard newline sequence. When PCRE is built, a default can be specified.
327: The default default is LF, which is the Unix standard. When PCRE is run, the
328: default can be overridden, either when a pattern is compiled, or when it is
329: matched.
330: </P>
331: <P>
332: At compile time, the newline convention can be specified by the <i>options</i>
333: argument of <b>pcre_compile()</b>, or it can be specified by special text at the
334: start of the pattern itself; this overrides any other settings. See the
335: <a href="pcrepattern.html"><b>pcrepattern</b></a>
336: page for details of the special character sequences.
337: </P>
338: <P>
339: In the PCRE documentation the word "newline" is used to mean "the character or
340: pair of characters that indicate a line break". The choice of newline
341: convention affects the handling of the dot, circumflex, and dollar
342: metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
343: recognized line ending sequence, the match position advancement for a
344: non-anchored pattern. There is more detail about this in the
345: <a href="#execoptions">section on <b>pcre_exec()</b> options</a>
346: below.
347: </P>
348: <P>
349: The choice of newline convention does not affect the interpretation of
350: the \n or \r escape sequences, nor does it affect what \R matches, which is
351: controlled in a similar way, but by separate options.
352: </P>
1.1.1.2 ! misho 353: <br><a name="SEC8" href="#TOC1">MULTITHREADING</a><br>
1.1 misho 354: <P>
355: The PCRE functions can be used in multi-threading applications, with the
356: proviso that the memory management functions pointed to by <b>pcre_malloc</b>,
357: <b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the
358: callout function pointed to by <b>pcre_callout</b>, are shared by all threads.
359: </P>
360: <P>
361: The compiled form of a regular expression is not altered during matching, so
362: the same compiled pattern can safely be used by several threads at once.
363: </P>
364: <P>
365: If the just-in-time optimization feature is being used, it needs separate
366: memory stack areas for each thread. See the
367: <a href="pcrejit.html"><b>pcrejit</b></a>
368: documentation for more details.
369: </P>
1.1.1.2 ! misho 370: <br><a name="SEC9" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br>
1.1 misho 371: <P>
372: The compiled form of a regular expression can be saved and re-used at a later
373: time, possibly by a different program, and even on a host other than the one on
374: which it was compiled. Details are given in the
375: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1.1.1.2 ! misho 376: documentation, which includes a description of the
! 377: <b>pcre_pattern_to_host_byte_order()</b> function. However, compiling a regular
! 378: expression with one version of PCRE for use with a different version is not
! 379: guaranteed to work and may cause crashes.
1.1 misho 380: </P>
1.1.1.2 ! misho 381: <br><a name="SEC10" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
1.1 misho 382: <P>
383: <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
384: </P>
385: <P>
386: The function <b>pcre_config()</b> makes it possible for a PCRE client to
387: discover which optional features have been compiled into the PCRE library. The
388: <a href="pcrebuild.html"><b>pcrebuild</b></a>
389: documentation has more details about these optional features.
390: </P>
391: <P>
392: The first argument for <b>pcre_config()</b> is an integer, specifying which
393: information is required; the second argument is a pointer to a variable into
1.1.1.2 ! misho 394: which the information is placed. The returned value is zero on success, or the
! 395: negative error code PCRE_ERROR_BADOPTION if the value in the first argument is
! 396: not recognized. The following information is available:
1.1 misho 397: <pre>
398: PCRE_CONFIG_UTF8
399: </pre>
400: The output is an integer that is set to one if UTF-8 support is available;
1.1.1.2 ! misho 401: otherwise it is set to zero. If this option is given to the 16-bit version of
! 402: this function, <b>pcre16_config()</b>, the result is PCRE_ERROR_BADOPTION.
! 403: <pre>
! 404: PCRE_CONFIG_UTF16
! 405: </pre>
! 406: The output is an integer that is set to one if UTF-16 support is available;
! 407: otherwise it is set to zero. This value should normally be given to the 16-bit
! 408: version of this function, <b>pcre16_config()</b>. If it is given to the 8-bit
! 409: version of this function, the result is PCRE_ERROR_BADOPTION.
1.1 misho 410: <pre>
411: PCRE_CONFIG_UNICODE_PROPERTIES
412: </pre>
413: The output is an integer that is set to one if support for Unicode character
414: properties is available; otherwise it is set to zero.
415: <pre>
416: PCRE_CONFIG_JIT
417: </pre>
418: The output is an integer that is set to one if support for just-in-time
419: compiling is available; otherwise it is set to zero.
420: <pre>
1.1.1.2 ! misho 421: PCRE_CONFIG_JITTARGET
! 422: </pre>
! 423: The output is a pointer to a zero-terminated "const char *" string. If JIT
! 424: support is available, the string contains the name of the architecture for
! 425: which the JIT compiler is configured, for example "x86 32bit (little endian +
! 426: unaligned)". If JIT support is not available, the result is NULL.
! 427: <pre>
1.1 misho 428: PCRE_CONFIG_NEWLINE
429: </pre>
430: The output is an integer whose value specifies the default character sequence
431: that is recognized as meaning "newline". The four values that are supported
432: are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
433: Though they are derived from ASCII, the same values are returned in EBCDIC
434: environments. The default should normally correspond to the standard sequence
435: for your operating system.
436: <pre>
437: PCRE_CONFIG_BSR
438: </pre>
439: The output is an integer whose value indicates what character sequences the \R
440: escape sequence matches by default. A value of 0 means that \R matches any
441: Unicode line ending sequence; a value of 1 means that \R matches only CR, LF,
442: or CRLF. The default can be overridden when a pattern is compiled or matched.
443: <pre>
444: PCRE_CONFIG_LINK_SIZE
445: </pre>
446: The output is an integer that contains the number of bytes used for internal
1.1.1.2 ! misho 447: linkage in compiled regular expressions. For the 8-bit library, the value can
! 448: be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still
! 449: a number of bytes. The default value of 2 is sufficient for all but the most
! 450: massive patterns, since it allows the compiled pattern to be up to 64K in size.
! 451: Larger values allow larger regular expressions to be compiled, at the expense
! 452: of slower matching.
1.1 misho 453: <pre>
454: PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
455: </pre>
456: The output is an integer that contains the threshold above which the POSIX
457: interface uses <b>malloc()</b> for output vectors. Further details are given in
458: the
459: <a href="pcreposix.html"><b>pcreposix</b></a>
460: documentation.
461: <pre>
462: PCRE_CONFIG_MATCH_LIMIT
463: </pre>
464: The output is a long integer that gives the default limit for the number of
465: internal matching function calls in a <b>pcre_exec()</b> execution. Further
466: details are given with <b>pcre_exec()</b> below.
467: <pre>
468: PCRE_CONFIG_MATCH_LIMIT_RECURSION
469: </pre>
470: The output is a long integer that gives the default limit for the depth of
471: recursion when calling the internal matching function in a <b>pcre_exec()</b>
472: execution. Further details are given with <b>pcre_exec()</b> below.
473: <pre>
474: PCRE_CONFIG_STACKRECURSE
475: </pre>
476: The output is an integer that is set to one if internal recursion when running
477: <b>pcre_exec()</b> is implemented by recursive function calls that use the stack
478: to remember their state. This is the usual way that PCRE is compiled. The
479: output is zero if PCRE was compiled to use blocks of data on the heap instead
480: of recursive function calls. In this case, <b>pcre_stack_malloc</b> and
481: <b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus
482: avoiding the use of the stack.
483: </P>
1.1.1.2 ! misho 484: <br><a name="SEC11" href="#TOC1">COMPILING A PATTERN</a><br>
1.1 misho 485: <P>
486: <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
487: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
488: <b>const unsigned char *<i>tableptr</i>);</b>
489: <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
490: <b>int *<i>errorcodeptr</i>,</b>
491: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
492: <b>const unsigned char *<i>tableptr</i>);</b>
493: </P>
494: <P>
495: Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be
496: called to compile a pattern into an internal form. The only difference between
497: the two interfaces is that <b>pcre_compile2()</b> has an additional argument,
498: <i>errorcodeptr</i>, via which a numerical error code can be returned. To avoid
499: too much repetition, we refer just to <b>pcre_compile()</b> below, but the
500: information applies equally to <b>pcre_compile2()</b>.
501: </P>
502: <P>
503: The pattern is a C string terminated by a binary zero, and is passed in the
504: <i>pattern</i> argument. A pointer to a single block of memory that is obtained
505: via <b>pcre_malloc</b> is returned. This contains the compiled code and related
506: data. The <b>pcre</b> type is defined for the returned block; this is a typedef
507: for a structure whose contents are not externally defined. It is up to the
508: caller to free the memory (via <b>pcre_free</b>) when it is no longer required.
509: </P>
510: <P>
511: Although the compiled code of a PCRE regex is relocatable, that is, it does not
512: depend on memory location, the complete <b>pcre</b> data block is not
513: fully relocatable, because it may contain a copy of the <i>tableptr</i>
514: argument, which is an address (see below).
515: </P>
516: <P>
517: The <i>options</i> 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: <a href="pcrepattern.html"><b>pcrepattern</b></a>
523: documentation). For those options that can be different in different parts of
524: the pattern, the contents of the <i>options</i> argument specifies their
525: settings at the start of compilation and execution. The PCRE_ANCHORED,
526: PCRE_BSR_<i>xxx</i>, PCRE_NEWLINE_<i>xxx</i>, PCRE_NO_UTF8_CHECK, and
527: PCRE_NO_START_OPT options can be set at the time of matching as well as at
528: compile time.
529: </P>
530: <P>
531: If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately.
532: Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns
533: NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual
534: error message. This is a static string that is part of the library. You must
535: not try to free it. Normally, the offset from the start of the pattern to the
536: byte that was being processed when the error was discovered is placed in the
537: variable pointed to by <i>erroffset</i>, which must not be NULL (if it is, an
538: immediate error is given). However, for an invalid UTF-8 string, the offset is
1.1.1.2 ! misho 539: that of the first byte of the failing character.
1.1 misho 540: </P>
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: <P>
548: If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
549: <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
550: returned via this argument in the event of an error. This is in addition to the
551: textual error message. Error codes and messages are listed below.
552: </P>
553: <P>
554: If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
555: character tables that are built when PCRE is compiled, using the default C
556: locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
557: call to <b>pcre_maketables()</b>. This value is stored with the compiled
558: pattern, and used again by <b>pcre_exec()</b>, unless another table pointer is
559: passed to it. For more discussion, see the section on locale support below.
560: </P>
561: <P>
562: This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
563: <pre>
564: pcre *re;
565: const char *error;
566: int erroffset;
567: re = pcre_compile(
568: "^A.*Z", /* the pattern */
569: 0, /* default options */
570: &error, /* for error message */
571: &erroffset, /* for error offset */
572: NULL); /* use default character tables */
573: </pre>
574: The following names for option bits are defined in the <b>pcre.h</b> header
575: file:
576: <pre>
577: PCRE_ANCHORED
578: </pre>
579: If this bit is set, the pattern is forced to be "anchored", that is, it is
580: constrained to match only at the first matching point in the string that is
581: being searched (the "subject string"). This effect can also be achieved by
582: appropriate constructs in the pattern itself, which is the only way to do it in
583: Perl.
584: <pre>
585: PCRE_AUTO_CALLOUT
586: </pre>
587: If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
588: all with number 255, before each pattern item. For discussion of the callout
589: facility, see the
590: <a href="pcrecallout.html"><b>pcrecallout</b></a>
591: documentation.
592: <pre>
593: PCRE_BSR_ANYCRLF
594: PCRE_BSR_UNICODE
595: </pre>
596: These options (which are mutually exclusive) control what the \R escape
597: sequence matches. The choice is either to match only CR, LF, or CRLF, or to
598: match any Unicode newline sequence. The default is specified when PCRE is
599: built. It can be overridden from within the pattern, or by setting an option
600: when a compiled pattern is matched.
601: <pre>
602: PCRE_CASELESS
603: </pre>
604: If this bit is set, letters in the pattern match both upper and lower case
605: letters. It is equivalent to Perl's /i option, and it can be changed within a
606: pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
607: concept of case for characters whose values are less than 128, so caseless
608: matching is always possible. For characters with higher values, the concept of
609: case is supported if PCRE is compiled with Unicode property support, but not
610: otherwise. If you want to use caseless matching for characters 128 and above,
611: you must ensure that PCRE is compiled with Unicode property support as well as
612: with UTF-8 support.
613: <pre>
614: PCRE_DOLLAR_ENDONLY
615: </pre>
616: If this bit is set, a dollar metacharacter in the pattern matches only at the
617: end of the subject string. Without this option, a dollar also matches
618: immediately before a newline at the end of the string (but not before any other
619: newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
620: There is no equivalent to this option in Perl, and no way to set it within a
621: pattern.
622: <pre>
623: PCRE_DOTALL
624: </pre>
625: If this bit is set, a dot metacharacter in the pattern matches a character of
626: any value, including one that indicates a newline. However, it only ever
627: matches one character, even if newlines are coded as CRLF. Without this option,
628: a dot does not match when the current position is at a newline. This option is
629: equivalent to Perl's /s option, and it can be changed within a pattern by a
630: (?s) option setting. A negative class such as [^a] always matches newline
631: characters, independent of the setting of this option.
632: <pre>
633: PCRE_DUPNAMES
634: </pre>
635: If this bit is set, names used to identify capturing subpatterns need not be
636: unique. This can be helpful for certain types of pattern when it is known that
637: only one instance of the named subpattern can ever be matched. There are more
638: details of named subpatterns below; see also the
639: <a href="pcrepattern.html"><b>pcrepattern</b></a>
640: documentation.
641: <pre>
642: PCRE_EXTENDED
643: </pre>
644: If this bit is set, whitespace data characters in the pattern are totally
645: ignored except when escaped or inside a character class. Whitespace does not
646: include the VT character (code 11). In addition, characters between an
647: unescaped # outside a character class and the next newline, inclusive, are also
648: ignored. This is equivalent to Perl's /x option, and it can be changed within a
649: pattern by a (?x) option setting.
650: </P>
651: <P>
652: Which characters are interpreted as newlines is controlled by the options
653: passed to <b>pcre_compile()</b> or by a special sequence at the start of the
654: pattern, as described in the section entitled
655: <a href="pcrepattern.html#newlines">"Newline conventions"</a>
656: in the <b>pcrepattern</b> documentation. Note that the end of this type of
657: comment is a literal newline sequence in the pattern; escape sequences that
658: happen to represent a newline do not count.
659: </P>
660: <P>
661: This option makes it possible to include comments inside complicated patterns.
662: Note, however, that this applies only to data characters. Whitespace characters
663: may never appear within special character sequences in a pattern, for example
664: within the sequence (?( that introduces a conditional subpattern.
665: <pre>
666: PCRE_EXTRA
667: </pre>
668: This option was invented in order to turn on additional functionality of PCRE
669: that is incompatible with Perl, but it is currently of very little use. When
670: set, any backslash in a pattern that is followed by a letter that has no
671: special meaning causes an error, thus reserving these combinations for future
672: expansion. By default, as in Perl, a backslash followed by a letter with no
673: special meaning is treated as a literal. (Perl can, however, be persuaded to
674: give an error for this, by running it with the -w option.) There are at present
675: no other features controlled by this option. It can also be set by a (?X)
676: option setting within a pattern.
677: <pre>
678: PCRE_FIRSTLINE
679: </pre>
680: If this option is set, an unanchored pattern is required to match before or at
681: the first newline in the subject string, though the matched text may continue
682: over the newline.
683: <pre>
684: PCRE_JAVASCRIPT_COMPAT
685: </pre>
686: If this option is set, PCRE's behaviour is changed in some ways so that it is
687: compatible with JavaScript rather than Perl. The changes are as follows:
688: </P>
689: <P>
690: (1) A lone closing square bracket in a pattern causes a compile-time error,
691: because this is illegal in JavaScript (by default it is treated as a data
692: character). Thus, the pattern AB]CD becomes illegal when this option is set.
693: </P>
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 (\1)(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: <P>
701: (3) \U matches an upper case "U" character; by default \U causes a compile
702: time error (Perl uses \U to upper case subsequent characters).
703: </P>
704: <P>
705: (4) \u matches a lower case "u" character unless it is followed by four
706: hexadecimal digits, in which case the hexadecimal number defines the code point
707: to match. By default, \u causes a compile time error (Perl uses it to upper
708: case the following character).
709: </P>
710: <P>
711: (5) \x matches a lower case "x" character unless it is followed by two
712: hexadecimal digits, in which case the hexadecimal number defines the code point
713: to match. By default, as in Perl, a hexadecimal number is always expected after
714: \x, but it may have zero, one, or two digits (so, for example, \xz matches a
715: binary zero character followed by z).
716: <pre>
717: PCRE_MULTILINE
718: </pre>
719: By default, PCRE treats the subject string as consisting of a single line of
720: characters (even if it actually contains newlines). The "start of line"
721: metacharacter (^) matches only at the start of the string, while the "end of
722: line" metacharacter ($) matches only at the end of the string, or before a
723: terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
724: Perl.
725: </P>
726: <P>
727: When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
728: match immediately following or immediately before internal newlines in the
729: subject string, respectively, as well as at the very start and end. This is
730: equivalent to Perl's /m option, and it can be changed within a pattern by a
731: (?m) option setting. If there are no newlines in a subject string, or no
732: occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
733: <pre>
734: PCRE_NEWLINE_CR
735: PCRE_NEWLINE_LF
736: PCRE_NEWLINE_CRLF
737: PCRE_NEWLINE_ANYCRLF
738: PCRE_NEWLINE_ANY
739: </pre>
740: These options override the default newline definition that was chosen when PCRE
741: was built. Setting the first or the second specifies that a newline is
742: indicated by a single character (CR or LF, respectively). Setting
743: PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
744: CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
745: preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
746: that any Unicode newline sequence should be recognized. The Unicode newline
747: sequences are the three just mentioned, plus the single characters VT (vertical
748: tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
1.1.1.2 ! misho 749: separator, U+2028), and PS (paragraph separator, U+2029). For the 8-bit
! 750: library, the last two are recognized only in UTF-8 mode.
1.1 misho 751: </P>
752: <P>
753: The newline setting in the options word uses three bits that are treated
754: as a number, giving eight possibilities. Currently only six are used (default
755: plus the five values above). This means that if you set more than one newline
756: option, the combination may or may not be sensible. For example,
757: PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
758: other combinations may yield unused numbers and cause an error.
759: </P>
760: <P>
761: The only time that a line break in a pattern is specially recognized when
762: compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
763: and so are ignored in this mode. Also, an unescaped # outside a character class
764: indicates a comment that lasts until after the next line break sequence. In
765: other circumstances, line break sequences in patterns are treated as literal
766: data.
767: </P>
768: <P>
769: The newline option that is set at compile time becomes the default that is used
770: for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden.
771: <pre>
772: PCRE_NO_AUTO_CAPTURE
773: </pre>
774: If this option is set, it disables the use of numbered capturing parentheses in
775: the pattern. Any opening parenthesis that is not followed by ? behaves as if it
776: were followed by ?: but named parentheses can still be used for capturing (and
777: they acquire numbers in the usual way). There is no equivalent of this option
778: in Perl.
779: <pre>
780: NO_START_OPTIMIZE
781: </pre>
782: This is an option that acts at matching time; that is, it is really an option
783: for <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. If it is set at compile time,
784: it is remembered with the compiled pattern and assumed at matching time. For
785: details see the discussion of PCRE_NO_START_OPTIMIZE
786: <a href="#execoptions">below.</a>
787: <pre>
788: PCRE_UCP
789: </pre>
790: This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W,
791: \w, and some of the POSIX character classes. By default, only ASCII characters
792: are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
793: classify characters. More details are given in the section on
794: <a href="pcre.html#genericchartypes">generic character types</a>
795: in the
796: <a href="pcrepattern.html"><b>pcrepattern</b></a>
797: page. If you set PCRE_UCP, matching one of the items it affects takes much
798: longer. The option is available only if PCRE has been compiled with Unicode
799: property support.
800: <pre>
801: PCRE_UNGREEDY
802: </pre>
803: This option inverts the "greediness" of the quantifiers so that they are not
804: greedy by default, but become greedy if followed by "?". It is not compatible
805: with Perl. It can also be set by a (?U) option setting within the pattern.
806: <pre>
807: PCRE_UTF8
808: </pre>
809: This option causes PCRE to regard both the pattern and the subject as strings
1.1.1.2 ! misho 810: of UTF-8 characters instead of single-byte strings. However, it is available
! 811: only when PCRE is built to include UTF support. If not, the use of this option
! 812: provokes an error. Details of how this option changes the behaviour of PCRE are
! 813: given in the
1.1 misho 814: <a href="pcreunicode.html"><b>pcreunicode</b></a>
815: page.
816: <pre>
817: PCRE_NO_UTF8_CHECK
818: </pre>
1.1.1.2 ! misho 819: When PCRE_UTF8 is set, the validity of the pattern as a UTF-8
! 820: string is automatically checked. There is a discussion about the
! 821: <a href="pcreunicode.html#utf8strings">validity of UTF-8 strings</a>
! 822: in the
! 823: <a href="pcreunicode.html"><b>pcreunicode</b></a>
! 824: page. If an invalid UTF-8 sequence is found, <b>pcre_compile()</b> returns an
! 825: error. If you already know that your pattern is valid, and you want to skip
! 826: this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option.
! 827: When it is set, the effect of passing an invalid UTF-8 string as a pattern is
! 828: undefined. It may cause your program to crash. Note that this option can also
! 829: be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress the
! 830: validity checking of subject strings.
1.1 misho 831: </P>
1.1.1.2 ! misho 832: <br><a name="SEC12" href="#TOC1">COMPILATION ERROR CODES</a><br>
1.1 misho 833: <P>
834: The following table lists the error codes than may be returned by
835: <b>pcre_compile2()</b>, along with the error messages that may be returned by
1.1.1.2 ! misho 836: both compiling functions. Note that error messages are always 8-bit ASCII
! 837: strings, even in 16-bit mode. As PCRE has developed, some error codes have
! 838: fallen out of use. To avoid confusion, they have not been re-used.
1.1 misho 839: <pre>
840: 0 no error
841: 1 \ at end of pattern
842: 2 \c at end of pattern
843: 3 unrecognized character follows \
844: 4 numbers out of order in {} quantifier
845: 5 number too big in {} quantifier
846: 6 missing terminating ] for character class
847: 7 invalid escape sequence in character class
848: 8 range out of order in character class
849: 9 nothing to repeat
850: 10 [this code is not in use]
851: 11 internal error: unexpected repeat
852: 12 unrecognized character after (? or (?-
853: 13 POSIX named classes are supported only within a class
854: 14 missing )
855: 15 reference to non-existent subpattern
856: 16 erroffset passed as NULL
857: 17 unknown option bit(s) set
858: 18 missing ) after comment
859: 19 [this code is not in use]
860: 20 regular expression is too large
861: 21 failed to get memory
862: 22 unmatched parentheses
863: 23 internal error: code overflow
864: 24 unrecognized character after (?<
865: 25 lookbehind assertion is not fixed length
866: 26 malformed number or name after (?(
867: 27 conditional group contains more than two branches
868: 28 assertion expected after (?(
869: 29 (?R or (?[+-]digits must be followed by )
870: 30 unknown POSIX class name
871: 31 POSIX collating elements are not supported
1.1.1.2 ! misho 872: 32 this version of PCRE is compiled without UTF support
1.1 misho 873: 33 [this code is not in use]
874: 34 character value in \x{...} sequence is too large
875: 35 invalid condition (?(0)
876: 36 \C not allowed in lookbehind assertion
877: 37 PCRE does not support \L, \l, \N{name}, \U, or \u
878: 38 number after (?C is > 255
879: 39 closing ) for (?C expected
880: 40 recursive call could loop indefinitely
881: 41 unrecognized character after (?P
882: 42 syntax error in subpattern name (missing terminator)
883: 43 two named subpatterns have the same name
1.1.1.2 ! misho 884: 44 invalid UTF-8 string (specifically UTF-8)
1.1 misho 885: 45 support for \P, \p, and \X has not been compiled
886: 46 malformed \P or \p sequence
887: 47 unknown property name after \P or \p
888: 48 subpattern name is too long (maximum 32 characters)
889: 49 too many named subpatterns (maximum 10000)
890: 50 [this code is not in use]
1.1.1.2 ! misho 891: 51 octal value is greater than \377 in 8-bit non-UTF-8 mode
1.1 misho 892: 52 internal error: overran compiling workspace
893: 53 internal error: previously-checked referenced subpattern
894: not found
895: 54 DEFINE group contains more than one branch
896: 55 repeating a DEFINE group is not allowed
897: 56 inconsistent NEWLINE options
898: 57 \g is not followed by a braced, angle-bracketed, or quoted
899: name/number or by a plain number
900: 58 a numbered reference must not be zero
901: 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
902: 60 (*VERB) not recognized
903: 61 number is too big
904: 62 subpattern name expected
905: 63 digit expected after (?+
906: 64 ] is an invalid data character in JavaScript compatibility mode
907: 65 different names for subpatterns of the same number are
908: not allowed
909: 66 (*MARK) must have an argument
1.1.1.2 ! misho 910: 67 this version of PCRE is not compiled with Unicode property
! 911: support
1.1 misho 912: 68 \c must be followed by an ASCII character
913: 69 \k is not followed by a braced, angle-bracketed, or quoted name
1.1.1.2 ! misho 914: 70 internal error: unknown opcode in find_fixedlength()
! 915: 71 \N is not supported in a class
! 916: 72 too many forward references
! 917: 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
! 918: 74 invalid UTF-16 string (specifically UTF-16)
1.1 misho 919: </pre>
920: The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
921: be used if the limits were changed when PCRE was built.
922: <a name="studyingapattern"></a></P>
1.1.1.2 ! misho 923: <br><a name="SEC13" href="#TOC1">STUDYING A PATTERN</a><br>
1.1 misho 924: <P>
925: <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i></b>
926: <b>const char **<i>errptr</i>);</b>
927: </P>
928: <P>
929: If a compiled pattern is going to be used several times, it is worth spending
930: more time analyzing it in order to speed up the time taken for matching. The
931: function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
932: argument. If studying the pattern produces additional information that will
933: help speed up matching, <b>pcre_study()</b> returns a pointer to a
934: <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
935: results of the study.
936: </P>
937: <P>
938: The returned value from <b>pcre_study()</b> can be passed directly to
939: <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. However, a <b>pcre_extra</b> block
940: also contains other fields that can be set by the caller before the block is
941: passed; these are described
942: <a href="#extradata">below</a>
943: in the section on matching a pattern.
944: </P>
945: <P>
946: If studying the pattern does not produce any useful information,
947: <b>pcre_study()</b> returns NULL. In that circumstance, if the calling program
948: wants to pass any of the other fields to <b>pcre_exec()</b> or
949: <b>pcre_dfa_exec()</b>, it must set up its own <b>pcre_extra</b> block.
950: </P>
951: <P>
952: The second argument of <b>pcre_study()</b> contains option bits. There is only
953: one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-time
954: compiler is available, the pattern is further compiled into machine code that
955: executes much faster than the <b>pcre_exec()</b> matching function. If
956: the just-in-time compiler is not available, this option is ignored. All other
957: bits in the <i>options</i> argument must be zero.
958: </P>
959: <P>
960: JIT compilation is a heavyweight optimization. It can take some time for
961: patterns to be analyzed, and for one-off matches and simple patterns the
962: benefit of faster execution might be offset by a much slower study time.
963: Not all patterns can be optimized by the JIT compiler. For those that cannot be
964: handled, matching automatically falls back to the <b>pcre_exec()</b>
965: interpreter. For more details, see the
966: <a href="pcrejit.html"><b>pcrejit</b></a>
967: documentation.
968: </P>
969: <P>
970: The third argument for <b>pcre_study()</b> is a pointer for an error message. If
971: studying succeeds (even if no data is returned), the variable it points to is
972: set to NULL. Otherwise it is set to point to a textual error message. This is a
973: static string that is part of the library. You must not try to free it. You
974: should test the error pointer for NULL after calling <b>pcre_study()</b>, to be
975: sure that it has run successfully.
976: </P>
977: <P>
978: When you are finished with a pattern, you can free the memory used for the
979: study data by calling <b>pcre_free_study()</b>. This function was added to the
980: API for release 8.20. For earlier versions, the memory could be freed with
981: <b>pcre_free()</b>, just like the pattern itself. This will still work in cases
982: where PCRE_STUDY_JIT_COMPILE is not used, but it is advisable to change to the
983: new function when convenient.
984: </P>
985: <P>
986: This is a typical way in which <b>pcre_study</b>() is used (except that in a
987: real application there should be tests for errors):
988: <pre>
989: int rc;
990: pcre *re;
991: pcre_extra *sd;
992: re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
993: sd = pcre_study(
994: re, /* result of pcre_compile() */
995: 0, /* no options */
996: &error); /* set to NULL or points to a message */
997: rc = pcre_exec( /* see below for details of pcre_exec() options */
998: re, sd, "subject", 7, 0, 0, ovector, 30);
999: ...
1000: pcre_free_study(sd);
1001: pcre_free(re);
1002: </pre>
1003: Studying a pattern does two things: first, a lower bound for the length of
1004: subject string that is needed to match the pattern is computed. This does not
1005: mean that there are any strings of that length that match, but it does
1006: guarantee that no shorter strings match. The value is used by
1007: <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b> to avoid wasting time by trying to
1008: match strings that are shorter than the lower bound. You can find out the value
1009: in a calling program via the <b>pcre_fullinfo()</b> function.
1010: </P>
1011: <P>
1012: Studying a pattern is also useful for non-anchored patterns that do not have a
1013: single fixed starting character. A bitmap of possible starting bytes is
1014: created. This speeds up finding a position in the subject at which to start
1.1.1.2 ! misho 1015: matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256.)
1.1 misho 1016: </P>
1017: <P>
1018: These two optimizations apply to both <b>pcre_exec()</b> and
1019: <b>pcre_dfa_exec()</b>. However, they are not used by <b>pcre_exec()</b> if
1020: <b>pcre_study()</b> is called with the PCRE_STUDY_JIT_COMPILE option, and
1021: just-in-time compiling is successful. The optimizations can be disabled by
1022: setting the PCRE_NO_START_OPTIMIZE option when calling <b>pcre_exec()</b> or
1023: <b>pcre_dfa_exec()</b>. You might want to do this if your pattern contains
1024: callouts or (*MARK) (which cannot be handled by the JIT compiler), and you want
1025: to make use of these facilities in cases where matching fails. See the
1026: discussion of PCRE_NO_START_OPTIMIZE
1027: <a href="#execoptions">below.</a>
1028: <a name="localesupport"></a></P>
1.1.1.2 ! misho 1029: <br><a name="SEC14" href="#TOC1">LOCALE SUPPORT</a><br>
1.1 misho 1030: <P>
1031: PCRE handles caseless matching, and determines whether characters are letters,
1032: digits, or whatever, by reference to a set of tables, indexed by character
1.1.1.2 ! misho 1033: value. When running in UTF-8 mode, this applies only to characters
! 1034: with codes less than 128. By default, higher-valued codes never match escapes
! 1035: such as \w or \d, but they can be tested with \p if PCRE is built with
! 1036: Unicode character property support. Alternatively, the PCRE_UCP option can be
! 1037: set at compile time; this causes \w and friends to use Unicode property
! 1038: support instead of built-in tables. The use of locales with Unicode is
! 1039: discouraged. If you are handling characters with codes greater than 128, you
! 1040: should either use UTF-8 and Unicode, or use locales, but not try to mix the
! 1041: two.
1.1 misho 1042: </P>
1043: <P>
1044: PCRE contains an internal set of tables that are used when the final argument
1045: of <b>pcre_compile()</b> is NULL. These are sufficient for many applications.
1046: Normally, the internal tables recognize only ASCII characters. However, when
1047: PCRE is built, it is possible to cause the internal tables to be rebuilt in the
1048: default "C" locale of the local system, which may cause them to be different.
1049: </P>
1050: <P>
1051: The internal tables can always be overridden by tables supplied by the
1052: application that calls PCRE. These may be created in a different locale from
1053: the default. As more and more applications change to using Unicode, the need
1054: for this locale support is expected to die away.
1055: </P>
1056: <P>
1057: External tables are built by calling the <b>pcre_maketables()</b> function,
1058: which has no arguments, in the relevant locale. The result can then be passed
1059: to <b>pcre_compile()</b> or <b>pcre_exec()</b> as often as necessary. For
1060: example, to build and use tables that are appropriate for the French locale
1061: (where accented characters with values greater than 128 are treated as letters),
1062: the following code could be used:
1063: <pre>
1064: setlocale(LC_CTYPE, "fr_FR");
1065: tables = pcre_maketables();
1066: re = pcre_compile(..., tables);
1067: </pre>
1068: The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
1069: are using Windows, the name for the French locale is "french".
1070: </P>
1071: <P>
1072: When <b>pcre_maketables()</b> runs, the tables are built in memory that is
1073: obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
1074: that the memory containing the tables remains available for as long as it is
1075: needed.
1076: </P>
1077: <P>
1078: The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
1079: pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
1080: and normally also by <b>pcre_exec()</b>. Thus, by default, for any single
1081: pattern, compilation, studying and matching all happen in the same locale, but
1082: different patterns can be compiled in different locales.
1083: </P>
1084: <P>
1085: It is possible to pass a table pointer or NULL (indicating the use of the
1086: internal tables) to <b>pcre_exec()</b>. Although not intended for this purpose,
1087: this facility could be used to match a pattern in a different locale from the
1088: one in which it was compiled. Passing table pointers at run time is discussed
1089: below in the section on matching a pattern.
1090: <a name="infoaboutpattern"></a></P>
1.1.1.2 ! misho 1091: <br><a name="SEC15" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
1.1 misho 1092: <P>
1093: <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1094: <b>int <i>what</i>, void *<i>where</i>);</b>
1095: </P>
1096: <P>
1097: The <b>pcre_fullinfo()</b> function returns information about a compiled
1.1.1.2 ! misho 1098: pattern. It replaces the <b>pcre_info()</b> function, which was removed from the
! 1099: library at version 8.30, after more than 10 years of obsolescence.
1.1 misho 1100: </P>
1101: <P>
1102: The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled
1103: pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if
1104: the pattern was not studied. The third argument specifies which piece of
1105: information is required, and the fourth argument is a pointer to a variable
1106: to receive the data. The yield of the function is zero for success, or one of
1107: the following negative numbers:
1108: <pre>
1.1.1.2 ! misho 1109: PCRE_ERROR_NULL the argument <i>code</i> was NULL
! 1110: the argument <i>where</i> was NULL
! 1111: PCRE_ERROR_BADMAGIC the "magic number" was not found
! 1112: PCRE_ERROR_BADENDIANNESS the pattern was compiled with different
! 1113: endianness
! 1114: PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid
1.1 misho 1115: </pre>
1116: The "magic number" is placed at the start of each compiled pattern as an simple
1.1.1.2 ! misho 1117: check against passing an arbitrary memory pointer. The endianness error can
! 1118: occur if a compiled pattern is saved and reloaded on a different host. Here is
! 1119: a typical call of <b>pcre_fullinfo()</b>, to obtain the length of the compiled
! 1120: pattern:
1.1 misho 1121: <pre>
1122: int rc;
1123: size_t length;
1124: rc = pcre_fullinfo(
1125: re, /* result of pcre_compile() */
1126: sd, /* result of pcre_study(), or NULL */
1127: PCRE_INFO_SIZE, /* what is required */
1128: &length); /* where to put the data */
1129: </pre>
1130: The possible values for the third argument are defined in <b>pcre.h</b>, and are
1131: as follows:
1132: <pre>
1133: PCRE_INFO_BACKREFMAX
1134: </pre>
1135: Return the number of the highest back reference in the pattern. The fourth
1136: argument should point to an <b>int</b> variable. Zero is returned if there are
1137: no back references.
1138: <pre>
1139: PCRE_INFO_CAPTURECOUNT
1140: </pre>
1141: Return the number of capturing subpatterns in the pattern. The fourth argument
1142: should point to an <b>int</b> variable.
1143: <pre>
1144: PCRE_INFO_DEFAULT_TABLES
1145: </pre>
1146: Return a pointer to the internal default character tables within PCRE. The
1147: fourth argument should point to an <b>unsigned char *</b> variable. This
1148: information call is provided for internal use by the <b>pcre_study()</b>
1149: function. External callers can cause PCRE to use its internal tables by passing
1150: a NULL table pointer.
1151: <pre>
1152: PCRE_INFO_FIRSTBYTE
1153: </pre>
1.1.1.2 ! misho 1154: Return information about the first data unit of any matched string, for a
! 1155: non-anchored pattern. (The name of this option refers to the 8-bit library,
! 1156: where data units are bytes.) The fourth argument should point to an <b>int</b>
! 1157: variable.
! 1158: </P>
! 1159: <P>
! 1160: If there is a fixed first value, for example, the letter "c" from a pattern
! 1161: such as (cat|cow|coyote), its value is returned. In the 8-bit library, the
! 1162: value is always less than 256; in the 16-bit library the value can be up to
! 1163: 0xffff.
1.1 misho 1164: </P>
1165: <P>
1.1.1.2 ! misho 1166: If there is no fixed first value, and if either
1.1 misho 1167: <br>
1168: <br>
1169: (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1170: starts with "^", or
1171: <br>
1172: <br>
1173: (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1174: (if it were set, the pattern would be anchored),
1175: <br>
1176: <br>
1177: -1 is returned, indicating that the pattern matches only at the start of a
1178: subject string or after any newline within the string. Otherwise -2 is
1179: returned. For anchored patterns, -2 is returned.
1180: <pre>
1181: PCRE_INFO_FIRSTTABLE
1182: </pre>
1183: If the pattern was studied, and this resulted in the construction of a 256-bit
1.1.1.2 ! misho 1184: table indicating a fixed set of values for the first data unit in any matching
1.1 misho 1185: string, a pointer to the table is returned. Otherwise NULL is returned. The
1186: fourth argument should point to an <b>unsigned char *</b> variable.
1187: <pre>
1188: PCRE_INFO_HASCRORLF
1189: </pre>
1190: Return 1 if the pattern contains any explicit matches for CR or LF characters,
1191: otherwise 0. The fourth argument should point to an <b>int</b> variable. An
1192: explicit match is either a literal CR or LF character, or \r or \n.
1193: <pre>
1194: PCRE_INFO_JCHANGED
1195: </pre>
1196: Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1197: 0. The fourth argument should point to an <b>int</b> variable. (?J) and
1198: (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1199: <pre>
1200: PCRE_INFO_JIT
1201: </pre>
1202: Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE option, and
1203: just-in-time compiling was successful. The fourth argument should point to an
1204: <b>int</b> variable. A return value of 0 means that JIT support is not available
1205: in this version of PCRE, or that the pattern was not studied with the
1206: PCRE_STUDY_JIT_COMPILE option, or that the JIT compiler could not handle this
1207: particular pattern. See the
1208: <a href="pcrejit.html"><b>pcrejit</b></a>
1209: documentation for details of what can and cannot be handled.
1210: <pre>
1211: PCRE_INFO_JITSIZE
1212: </pre>
1213: If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1214: return the size of the JIT compiled code, otherwise return zero. The fourth
1215: argument should point to a <b>size_t</b> variable.
1216: <pre>
1217: PCRE_INFO_LASTLITERAL
1218: </pre>
1.1.1.2 ! misho 1219: Return the value of the rightmost literal data unit that must exist in any
! 1220: matched string, other than at its start, if such a value has been recorded. The
! 1221: fourth argument should point to an <b>int</b> variable. If there is no such
! 1222: value, -1 is returned. For anchored patterns, a last literal value is recorded
! 1223: only if it follows something of variable length. For example, for the pattern
1.1 misho 1224: /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
1225: is -1.
1226: <pre>
1227: PCRE_INFO_MINLENGTH
1228: </pre>
1229: If the pattern was studied and a minimum length for matching subject strings
1230: was computed, its value is returned. Otherwise the returned value is -1. The
1.1.1.2 ! misho 1231: value is a number of characters, which in UTF-8 mode may be different from the
! 1232: number of bytes. The fourth argument should point to an <b>int</b> variable. A
1.1 misho 1233: non-negative value is a lower bound to the length of any matching string. There
1234: may not be any strings of that length that do actually match, but every string
1235: that does match is at least that long.
1236: <pre>
1237: PCRE_INFO_NAMECOUNT
1238: PCRE_INFO_NAMEENTRYSIZE
1239: PCRE_INFO_NAMETABLE
1240: </pre>
1241: PCRE supports the use of named as well as numbered capturing parentheses. The
1242: names are just an additional way of identifying the parentheses, which still
1243: acquire numbers. Several convenience functions such as
1244: <b>pcre_get_named_substring()</b> are provided for extracting captured
1245: substrings by name. It is also possible to extract the data directly, by first
1246: converting the name to a number in order to access the correct pointers in the
1247: output vector (described with <b>pcre_exec()</b> below). To do the conversion,
1248: you need to use the name-to-number map, which is described by these three
1249: values.
1250: </P>
1251: <P>
1252: The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1253: the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1254: entry; both of these return an <b>int</b> value. The entry size depends on the
1255: length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1.1.1.2 ! misho 1256: entry of the table. This is a pointer to <b>char</b> in the 8-bit library, where
! 1257: the first two bytes of each entry are the number of the capturing parenthesis,
! 1258: most significant byte first. In the 16-bit library, the pointer points to
! 1259: 16-bit data units, the first of which contains the parenthesis number. The rest
! 1260: of the entry is the corresponding name, zero terminated.
1.1 misho 1261: </P>
1262: <P>
1263: The names are in alphabetical order. Duplicate names may appear if (?| is used
1264: to create multiple groups with the same number, as described in the
1265: <a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
1266: in the
1267: <a href="pcrepattern.html"><b>pcrepattern</b></a>
1268: page. Duplicate names for subpatterns with different numbers are permitted only
1269: if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1270: table in the order in which they were found in the pattern. In the absence of
1271: (?| this is the order of increasing number; when (?| is used this is not
1272: necessarily the case because later subpatterns may have lower numbers.
1273: </P>
1274: <P>
1275: As a simple example of the name/number table, consider the following pattern
1.1.1.2 ! misho 1276: after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white
! 1277: space - including newlines - is ignored):
1.1 misho 1278: <pre>
1279: (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) )
1280: </pre>
1281: There are four named subpatterns, so the table has four entries, and each entry
1282: in the table is eight bytes long. The table is as follows, with non-printing
1283: bytes shows in hexadecimal, and undefined bytes shown as ??:
1284: <pre>
1285: 00 01 d a t e 00 ??
1286: 00 05 d a y 00 ?? ??
1287: 00 04 m o n t h 00
1288: 00 02 y e a r 00 ??
1289: </pre>
1290: When writing code to extract data from named subpatterns using the
1291: name-to-number map, remember that the length of the entries is likely to be
1292: different for each compiled pattern.
1293: <pre>
1294: PCRE_INFO_OKPARTIAL
1295: </pre>
1296: Return 1 if the pattern can be used for partial matching with
1297: <b>pcre_exec()</b>, otherwise 0. The fourth argument should point to an
1298: <b>int</b> variable. From release 8.00, this always returns 1, because the
1299: restrictions that previously applied to partial matching have been lifted. The
1300: <a href="pcrepartial.html"><b>pcrepartial</b></a>
1301: documentation gives details of partial matching.
1302: <pre>
1303: PCRE_INFO_OPTIONS
1304: </pre>
1305: Return a copy of the options with which the pattern was compiled. The fourth
1306: argument should point to an <b>unsigned long int</b> variable. These option bits
1307: are those specified in the call to <b>pcre_compile()</b>, modified by any
1308: top-level option settings at the start of the pattern itself. In other words,
1309: they are the options that will be in force when matching starts. For example,
1310: if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1311: result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1312: </P>
1313: <P>
1314: A pattern is automatically anchored by PCRE if all of its top-level
1315: alternatives begin with one of the following:
1316: <pre>
1317: ^ unless PCRE_MULTILINE is set
1318: \A always
1319: \G always
1320: .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
1321: </pre>
1322: For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1323: <b>pcre_fullinfo()</b>.
1324: <pre>
1325: PCRE_INFO_SIZE
1326: </pre>
1.1.1.2 ! misho 1327: Return the size of the compiled pattern in bytes (for both libraries). The
! 1328: fourth argument should point to a <b>size_t</b> variable. This value does not
! 1329: include the size of the <b>pcre</b> structure that is returned by
! 1330: <b>pcre_compile()</b>. The value that is passed as the argument to
! 1331: <b>pcre_malloc()</b> when <b>pcre_compile()</b> is getting memory in which to
! 1332: place the compiled data is the value returned by this option plus the size of
! 1333: the <b>pcre</b> structure. Studying a compiled pattern, with or without JIT,
! 1334: does not alter the value returned by this option.
1.1 misho 1335: <pre>
1336: PCRE_INFO_STUDYSIZE
1337: </pre>
1.1.1.2 ! misho 1338: Return the size in bytes of the data block pointed to by the <i>study_data</i>
! 1339: field in a <b>pcre_extra</b> block. If <b>pcre_extra</b> is NULL, or there is no
! 1340: study data, zero is returned. The fourth argument should point to a
! 1341: <b>size_t</b> variable. The <i>study_data</i> field is set by <b>pcre_study()</b>
! 1342: to record information that will speed up matching (see the section entitled
1.1 misho 1343: <a href="#studyingapattern">"Studying a pattern"</a>
1344: above). The format of the <i>study_data</i> block is private, but its length
1345: is made available via this option so that it can be saved and restored (see the
1346: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1347: documentation for details).
1348: </P>
1.1.1.2 ! misho 1349: <br><a name="SEC16" href="#TOC1">REFERENCE COUNTS</a><br>
1.1 misho 1350: <P>
1351: <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
1352: </P>
1353: <P>
1354: The <b>pcre_refcount()</b> function is used to maintain a reference count in the
1355: data block that contains a compiled pattern. It is provided for the benefit of
1356: applications that operate in an object-oriented manner, where different parts
1357: of the application may be using the same compiled pattern, but you want to free
1358: the block when they are all done.
1359: </P>
1360: <P>
1361: When a pattern is compiled, the reference count field is initialized to zero.
1362: It is changed only by calling this function, whose action is to add the
1363: <i>adjust</i> value (which may be positive or negative) to it. The yield of the
1364: function is the new value. However, the value of the count is constrained to
1365: lie between 0 and 65535, inclusive. If the new value is outside these limits,
1366: it is forced to the appropriate limit value.
1367: </P>
1368: <P>
1369: Except when it is zero, the reference count is not correctly preserved if a
1370: pattern is compiled on one host and then transferred to a host whose byte-order
1371: is different. (This seems a highly unlikely scenario.)
1372: </P>
1.1.1.2 ! misho 1373: <br><a name="SEC17" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
1.1 misho 1374: <P>
1375: <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1376: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1377: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
1378: </P>
1379: <P>
1380: The function <b>pcre_exec()</b> is called to match a subject string against a
1381: compiled pattern, which is passed in the <i>code</i> argument. If the
1382: pattern was studied, the result of the study should be passed in the
1383: <i>extra</i> argument. You can call <b>pcre_exec()</b> with the same <i>code</i>
1384: and <i>extra</i> arguments as many times as you like, in order to match
1385: different subject strings with the same pattern.
1386: </P>
1387: <P>
1388: This function is the main matching facility of the library, and it operates in
1389: a Perl-like manner. For specialist use there is also an alternative matching
1390: function, which is described
1391: <a href="#dfamatch">below</a>
1392: in the section about the <b>pcre_dfa_exec()</b> function.
1393: </P>
1394: <P>
1395: In most applications, the pattern will have been compiled (and optionally
1396: studied) in the same process that calls <b>pcre_exec()</b>. However, it is
1397: possible to save compiled patterns and study data, and then use them later
1398: in different processes, possibly even on different hosts. For a discussion
1399: about this, see the
1400: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1401: documentation.
1402: </P>
1403: <P>
1404: Here is an example of a simple call to <b>pcre_exec()</b>:
1405: <pre>
1406: int rc;
1407: int ovector[30];
1408: rc = pcre_exec(
1409: re, /* result of pcre_compile() */
1410: NULL, /* we didn't study the pattern */
1411: "some string", /* the subject string */
1412: 11, /* the length of the subject string */
1413: 0, /* start at offset 0 in the subject */
1414: 0, /* default options */
1415: ovector, /* vector of integers for substring information */
1416: 30); /* number of elements (NOT size in bytes) */
1417: <a name="extradata"></a></PRE>
1418: </P>
1419: <br><b>
1420: Extra data for <b>pcre_exec()</b>
1421: </b><br>
1422: <P>
1423: If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
1424: data block. The <b>pcre_study()</b> function returns such a block (when it
1425: doesn't return NULL), but you can also create one for yourself, and pass
1426: additional information in it. The <b>pcre_extra</b> block contains the following
1427: fields (not necessarily in this order):
1428: <pre>
1429: unsigned long int <i>flags</i>;
1430: void *<i>study_data</i>;
1431: void *<i>executable_jit</i>;
1432: unsigned long int <i>match_limit</i>;
1433: unsigned long int <i>match_limit_recursion</i>;
1434: void *<i>callout_data</i>;
1435: const unsigned char *<i>tables</i>;
1436: unsigned char **<i>mark</i>;
1437: </pre>
1.1.1.2 ! misho 1438: In the 16-bit version of this structure, the <i>mark</i> field has type
! 1439: "PCRE_UCHAR16 **".
! 1440: </P>
! 1441: <P>
1.1 misho 1442: The <i>flags</i> field is a bitmap that specifies which of the other fields
1443: are set. The flag bits are:
1444: <pre>
1445: PCRE_EXTRA_STUDY_DATA
1446: PCRE_EXTRA_EXECUTABLE_JIT
1447: PCRE_EXTRA_MATCH_LIMIT
1448: PCRE_EXTRA_MATCH_LIMIT_RECURSION
1449: PCRE_EXTRA_CALLOUT_DATA
1450: PCRE_EXTRA_TABLES
1451: PCRE_EXTRA_MARK
1452: </pre>
1453: Other flag bits should be set to zero. The <i>study_data</i> field and sometimes
1454: the <i>executable_jit</i> field are set in the <b>pcre_extra</b> block that is
1455: returned by <b>pcre_study()</b>, together with the appropriate flag bits. You
1456: should not set these yourself, but you may add to the block by setting the
1457: other fields and their corresponding flag bits.
1458: </P>
1459: <P>
1460: The <i>match_limit</i> field provides a means of preventing PCRE from using up a
1461: vast amount of resources when running patterns that are not going to match,
1462: but which have a very large number of possibilities in their search trees. The
1463: classic example is a pattern that uses nested unlimited repeats.
1464: </P>
1465: <P>
1466: Internally, <b>pcre_exec()</b> uses a function called <b>match()</b>, which it
1467: calls repeatedly (sometimes recursively). The limit set by <i>match_limit</i> is
1468: imposed on the number of times this function is called during a match, which
1469: has the effect of limiting the amount of backtracking that can take place. For
1470: patterns that are not anchored, the count restarts from zero for each position
1471: in the subject string.
1472: </P>
1473: <P>
1474: When <b>pcre_exec()</b> is called with a pattern that was successfully studied
1475: with the PCRE_STUDY_JIT_COMPILE option, the way that the matching is executed
1476: is entirely different. However, there is still the possibility of runaway
1477: matching that goes on for a very long time, and so the <i>match_limit</i> value
1478: is also used in this case (but in a different way) to limit how long the
1479: matching can continue.
1480: </P>
1481: <P>
1482: The default value for the limit can be set when PCRE is built; the default
1483: default is 10 million, which handles all but the most extreme cases. You can
1484: override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b>
1485: block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1486: the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns
1487: PCRE_ERROR_MATCHLIMIT.
1488: </P>
1489: <P>
1490: The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but
1491: instead of limiting the total number of times that <b>match()</b> is called, it
1492: limits the depth of recursion. The recursion depth is a smaller number than the
1493: total number of calls, because not all calls to <b>match()</b> are recursive.
1494: This limit is of use only if it is set smaller than <i>match_limit</i>.
1495: </P>
1496: <P>
1497: Limiting the recursion depth limits the amount of machine stack that can be
1498: used, or, when PCRE has been compiled to use memory on the heap instead of the
1499: stack, the amount of heap memory that can be used. This limit is not relevant,
1500: and is ignored, if the pattern was successfully studied with
1501: PCRE_STUDY_JIT_COMPILE.
1502: </P>
1503: <P>
1504: The default value for <i>match_limit_recursion</i> can be set when PCRE is
1505: built; the default default is the same value as the default for
1506: <i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b>
1507: with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and
1508: PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit
1509: is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT.
1510: </P>
1511: <P>
1512: The <i>callout_data</i> field is used in conjunction with the "callout" feature,
1513: and is described in the
1514: <a href="pcrecallout.html"><b>pcrecallout</b></a>
1515: documentation.
1516: </P>
1517: <P>
1518: The <i>tables</i> field is used to pass a character tables pointer to
1519: <b>pcre_exec()</b>; this overrides the value that is stored with the compiled
1520: pattern. A non-NULL value is stored with the compiled pattern only if custom
1521: tables were supplied to <b>pcre_compile()</b> via its <i>tableptr</i> argument.
1522: If NULL is passed to <b>pcre_exec()</b> using this mechanism, it forces PCRE's
1523: internal tables to be used. This facility is helpful when re-using patterns
1524: that have been saved after compiling with an external set of tables, because
1525: the external tables might be at a different address when <b>pcre_exec()</b> is
1526: called. See the
1527: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1528: documentation for a discussion of saving compiled patterns for later use.
1529: </P>
1530: <P>
1531: If PCRE_EXTRA_MARK is set in the <i>flags</i> field, the <i>mark</i> field must
1.1.1.2 ! misho 1532: be set to point to a suitable variable. If the pattern contains any
1.1 misho 1533: backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1534: a name to pass back, a pointer to the name string (zero terminated) is placed
1535: in the variable pointed to by the <i>mark</i> field. The names are within the
1536: compiled pattern; if you wish to retain such a name you must copy it before
1537: freeing the memory of a compiled pattern. If there is no name to pass back, the
1.1.1.2 ! misho 1538: variable pointed to by the <i>mark</i> field is set to NULL. For details of the
1.1 misho 1539: backtracking control verbs, see the section entitled
1540: <a href="pcrepattern#backtrackcontrol">"Backtracking control"</a>
1541: in the
1542: <a href="pcrepattern.html"><b>pcrepattern</b></a>
1543: documentation.
1544: <a name="execoptions"></a></P>
1545: <br><b>
1546: Option bits for <b>pcre_exec()</b>
1547: </b><br>
1548: <P>
1549: The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
1550: zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1551: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1552: PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1553: PCRE_PARTIAL_HARD.
1554: </P>
1555: <P>
1556: If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1557: the only supported options for JIT execution are PCRE_NO_UTF8_CHECK,
1558: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NOTEMPTY_ATSTART. Note in
1559: particular that partial matching is not supported. If an unsupported option is
1560: used, JIT execution is disabled and the normal interpretive code in
1561: <b>pcre_exec()</b> is run.
1562: <pre>
1563: PCRE_ANCHORED
1564: </pre>
1565: The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
1566: matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1567: to be anchored by virtue of its contents, it cannot be made unachored at
1568: matching time.
1569: <pre>
1570: PCRE_BSR_ANYCRLF
1571: PCRE_BSR_UNICODE
1572: </pre>
1573: These options (which are mutually exclusive) control what the \R escape
1574: sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1575: match any Unicode newline sequence. These options override the choice that was
1576: made or defaulted when the pattern was compiled.
1577: <pre>
1578: PCRE_NEWLINE_CR
1579: PCRE_NEWLINE_LF
1580: PCRE_NEWLINE_CRLF
1581: PCRE_NEWLINE_ANYCRLF
1582: PCRE_NEWLINE_ANY
1583: </pre>
1584: These options override the newline definition that was chosen or defaulted when
1585: the pattern was compiled. For details, see the description of
1586: <b>pcre_compile()</b> above. During matching, the newline choice affects the
1587: behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1588: the way the match position is advanced after a match failure for an unanchored
1589: pattern.
1590: </P>
1591: <P>
1592: When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1593: match attempt for an unanchored pattern fails when the current position is at a
1594: CRLF sequence, and the pattern contains no explicit matches for CR or LF
1595: characters, the match position is advanced by two characters instead of one, in
1596: other words, to after the CRLF.
1597: </P>
1598: <P>
1599: The above rule is a compromise that makes the most common cases work as
1600: expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1601: set), it does not match the string "\r\nA" because, after failing at the
1602: start, it skips both the CR and the LF before retrying. However, the pattern
1603: [\r\n]A does match that string, because it contains an explicit CR or LF
1604: reference, and so advances only by one character after the first failure.
1605: </P>
1606: <P>
1607: An explicit match for CR of LF is either a literal appearance of one of those
1608: characters, or one of the \r or \n escape sequences. Implicit matches such as
1609: [^X] do not count, nor does \s (which includes CR and LF in the characters
1610: that it matches).
1611: </P>
1612: <P>
1613: Notwithstanding the above, anomalous effects may still occur when CRLF is a
1614: valid newline sequence and explicit \r or \n escapes appear in the pattern.
1615: <pre>
1616: PCRE_NOTBOL
1617: </pre>
1618: This option specifies that first character of the subject string is not the
1619: beginning of a line, so the circumflex metacharacter should not match before
1620: it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1621: never to match. This option affects only the behaviour of the circumflex
1622: metacharacter. It does not affect \A.
1623: <pre>
1624: PCRE_NOTEOL
1625: </pre>
1626: This option specifies that the end of the subject string is not the end of a
1627: line, so the dollar metacharacter should not match it nor (except in multiline
1628: mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1629: compile time) causes dollar never to match. This option affects only the
1630: behaviour of the dollar metacharacter. It does not affect \Z or \z.
1631: <pre>
1632: PCRE_NOTEMPTY
1633: </pre>
1634: An empty string is not considered to be a valid match if this option is set. If
1635: there are alternatives in the pattern, they are tried. If all the alternatives
1636: match the empty string, the entire match fails. For example, if the pattern
1637: <pre>
1638: a?b?
1639: </pre>
1640: is applied to a string not beginning with "a" or "b", it matches an empty
1641: string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1642: valid, so PCRE searches further into the string for occurrences of "a" or "b".
1643: <pre>
1644: PCRE_NOTEMPTY_ATSTART
1645: </pre>
1646: This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1647: the start of the subject is permitted. If the pattern is anchored, such a match
1648: can occur only if the pattern contains \K.
1649: </P>
1650: <P>
1651: Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1652: does make a special case of a pattern match of the empty string within its
1653: <b>split()</b> function, and when using the /g modifier. It is possible to
1654: emulate Perl's behaviour after matching a null string by first trying the match
1655: again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1656: if that fails, by advancing the starting offset (see below) and trying an
1657: ordinary match again. There is some code that demonstrates how to do this in
1658: the
1659: <a href="pcredemo.html"><b>pcredemo</b></a>
1660: sample program. In the most general case, you have to check to see if the
1661: newline convention recognizes CRLF as a newline, and if so, and the current
1662: character is CR followed by LF, advance the starting offset by two characters
1663: instead of one.
1664: <pre>
1665: PCRE_NO_START_OPTIMIZE
1666: </pre>
1667: There are a number of optimizations that <b>pcre_exec()</b> uses at the start of
1668: a match, in order to speed up the process. For example, if it is known that an
1669: unanchored match must start with a specific character, it searches the subject
1670: for that character, and fails immediately if it cannot find it, without
1671: actually running the main matching function. This means that a special item
1672: such as (*COMMIT) at the start of a pattern is not considered until after a
1673: suitable starting point for the match has been found. When callouts or (*MARK)
1674: items are in use, these "start-up" optimizations can cause them to be skipped
1675: if the pattern is never actually used. The start-up optimizations are in effect
1676: a pre-scan of the subject that takes place before the pattern is run.
1677: </P>
1678: <P>
1679: The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1680: causing performance to suffer, but ensuring that in cases where the result is
1681: "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1682: are considered at every possible starting position in the subject string. If
1683: PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1684: time.
1685: </P>
1686: <P>
1687: Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1688: Consider the pattern
1689: <pre>
1690: (*COMMIT)ABC
1691: </pre>
1692: When this is compiled, PCRE records the fact that a match must start with the
1693: character "A". Suppose the subject string is "DEFABC". The start-up
1694: optimization scans along the subject, finds "A" and runs the first match
1695: attempt from there. The (*COMMIT) item means that the pattern must match the
1696: current starting position, which in this case, it does. However, if the same
1697: match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1698: subject string does not happen. The first match attempt is run starting from
1699: "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1700: the overall result is "no match". If the pattern is studied, more start-up
1701: optimizations may be used. For example, a minimum length for the subject may be
1702: recorded. Consider the pattern
1703: <pre>
1704: (*MARK:A)(X|Y)
1705: </pre>
1706: The minimum length for a match is one character. If the subject is "ABC", there
1707: will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1708: If the pattern is studied, the final attempt does not take place, because PCRE
1709: knows that the subject is too short, and so the (*MARK) is never encountered.
1710: In this case, studying the pattern does not affect the overall match result,
1711: which is still "no match", but it does affect the auxiliary information that is
1712: returned.
1713: <pre>
1714: PCRE_NO_UTF8_CHECK
1715: </pre>
1716: When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1717: string is automatically checked when <b>pcre_exec()</b> is subsequently called.
1718: The value of <i>startoffset</i> is also checked to ensure that it points to the
1719: start of a UTF-8 character. There is a discussion about the validity of UTF-8
1720: strings in the
1.1.1.2 ! misho 1721: <a href="pcreunicode.html"><b>pcreunicode</b></a>
! 1722: page. If an invalid sequence of bytes is found, <b>pcre_exec()</b> returns the
! 1723: error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
! 1724: truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both
! 1725: cases, information about the precise nature of the error may also be returned
! 1726: (see the descriptions of these errors in the section entitled \fIError return
! 1727: values from\fP <b>pcre_exec()</b>
1.1 misho 1728: <a href="#errorlist">below).</a>
1729: If <i>startoffset</i> contains a value that does not point to the start of a
1730: UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1731: returned.
1732: </P>
1733: <P>
1734: If you already know that your subject is valid, and you want to skip these
1735: checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1736: calling <b>pcre_exec()</b>. You might want to do this for the second and
1737: subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find
1738: all the matches in a single subject string. However, you should be sure that
1.1.1.2 ! misho 1739: the value of <i>startoffset</i> points to the start of a character (or the end
! 1740: of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
! 1741: invalid string as a subject or an invalid value of <i>startoffset</i> is
1.1 misho 1742: undefined. Your program may crash.
1743: <pre>
1744: PCRE_PARTIAL_HARD
1745: PCRE_PARTIAL_SOFT
1746: </pre>
1747: These options turn on the partial matching feature. For backwards
1748: compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1749: occurs if the end of the subject string is reached successfully, but there are
1750: not enough subject characters to complete the match. If this happens when
1751: PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1752: testing any remaining alternatives. Only if no complete match can be found is
1753: PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1754: PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1755: but only if no complete match can be found.
1756: </P>
1757: <P>
1758: If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1759: partial match is found, <b>pcre_exec()</b> immediately returns
1760: PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1761: when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1762: important that an alternative complete match.
1763: </P>
1764: <P>
1765: In both cases, the portion of the string that was inspected when the partial
1766: match was found is set as the first matching string. There is a more detailed
1767: discussion of partial and multi-segment matching, with examples, in the
1768: <a href="pcrepartial.html"><b>pcrepartial</b></a>
1769: documentation.
1770: </P>
1771: <br><b>
1772: The string to be matched by <b>pcre_exec()</b>
1773: </b><br>
1774: <P>
1775: The subject string is passed to <b>pcre_exec()</b> as a pointer in
1.1.1.2 ! misho 1776: <i>subject</i>, a length in bytes in <i>length</i>, and a starting byte offset
1.1 misho 1777: in <i>startoffset</i>. If this is negative or greater than the length of the
1778: subject, <b>pcre_exec()</b> returns PCRE_ERROR_BADOFFSET. When the starting
1779: offset is zero, the search for a match starts at the beginning of the subject,
1780: and this is by far the most common case. In UTF-8 mode, the byte offset must
1781: point to the start of a UTF-8 character (or the end of the subject). Unlike the
1782: pattern string, the subject may contain binary zero bytes.
1783: </P>
1784: <P>
1785: A non-zero starting offset is useful when searching for another match in the
1786: same subject by calling <b>pcre_exec()</b> again after a previous success.
1787: Setting <i>startoffset</i> differs from just passing over a shortened string and
1788: setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1789: lookbehind. For example, consider the pattern
1790: <pre>
1791: \Biss\B
1792: </pre>
1793: which finds occurrences of "iss" in the middle of words. (\B matches only if
1794: the current position in the subject is not a word boundary.) When applied to
1795: the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
1796: occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the
1797: subject, namely "issipi", it does not match, because \B is always false at the
1798: start of the subject, which is deemed to be a word boundary. However, if
1799: <b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i>
1800: set to 4, it finds the second occurrence of "iss" because it is able to look
1801: behind the starting point to discover that it is preceded by a letter.
1802: </P>
1803: <P>
1804: Finding all the matches in a subject is tricky when the pattern can match an
1805: empty string. It is possible to emulate Perl's /g behaviour by first trying the
1806: match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1807: PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1808: and trying an ordinary match again. There is some code that demonstrates how to
1809: do this in the
1810: <a href="pcredemo.html"><b>pcredemo</b></a>
1811: sample program. In the most general case, you have to check to see if the
1812: newline convention recognizes CRLF as a newline, and if so, and the current
1813: character is CR followed by LF, advance the starting offset by two characters
1814: instead of one.
1815: </P>
1816: <P>
1817: If a non-zero starting offset is passed when the pattern is anchored, one
1818: attempt to match at the given offset is made. This can only succeed if the
1819: pattern does not require the match to be at the start of the subject.
1820: </P>
1821: <br><b>
1822: How <b>pcre_exec()</b> returns captured substrings
1823: </b><br>
1824: <P>
1825: In general, a pattern matches a certain portion of the subject, and in
1826: addition, further substrings from the subject may be picked out by parts of the
1827: pattern. Following the usage in Jeffrey Friedl's book, this is called
1828: "capturing" in what follows, and the phrase "capturing subpattern" is used for
1829: a fragment of a pattern that picks out a substring. PCRE supports several other
1830: kinds of parenthesized subpattern that do not cause substrings to be captured.
1831: </P>
1832: <P>
1833: Captured substrings are returned to the caller via a vector of integers whose
1834: address is passed in <i>ovector</i>. The number of elements in the vector is
1835: passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>: this
1836: argument is NOT the size of <i>ovector</i> in bytes.
1837: </P>
1838: <P>
1839: The first two-thirds of the vector is used to pass back captured substrings,
1840: each substring using a pair of integers. The remaining third of the vector is
1841: used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
1842: and is not available for passing back information. The number passed in
1843: <i>ovecsize</i> should always be a multiple of three. If it is not, it is
1844: rounded down.
1845: </P>
1846: <P>
1847: When a match is successful, information about captured substrings is returned
1848: in pairs of integers, starting at the beginning of <i>ovector</i>, and
1849: continuing up to two-thirds of its length at the most. The first element of
1850: each pair is set to the byte offset of the first character in a substring, and
1851: the second is set to the byte offset of the first character after the end of a
1852: substring. <b>Note</b>: these values are always byte offsets, even in UTF-8
1853: mode. They are not character counts.
1854: </P>
1855: <P>
1856: The first pair of integers, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the
1857: portion of the subject string matched by the entire pattern. The next pair is
1858: used for the first capturing subpattern, and so on. The value returned by
1859: <b>pcre_exec()</b> is one more than the highest numbered pair that has been set.
1860: For example, if two substrings have been captured, the returned value is 3. If
1861: there are no capturing subpatterns, the return value from a successful match is
1862: 1, indicating that just the first pair of offsets has been set.
1863: </P>
1864: <P>
1865: If a capturing subpattern is matched repeatedly, it is the last portion of the
1866: string that it matched that is returned.
1867: </P>
1868: <P>
1869: If the vector is too small to hold all the captured substring offsets, it is
1870: used as far as possible (up to two-thirds of its length), and the function
1871: returns a value of zero. If neither the actual string matched not any captured
1872: substrings are of interest, <b>pcre_exec()</b> may be called with <i>ovector</i>
1873: passed as NULL and <i>ovecsize</i> as zero. However, if the pattern contains
1874: back references and the <i>ovector</i> is not big enough to remember the related
1875: substrings, PCRE has to get additional memory for use during matching. Thus it
1876: is usually advisable to supply an <i>ovector</i> of reasonable size.
1877: </P>
1878: <P>
1879: There are some cases where zero is returned (indicating vector overflow) when
1880: in fact the vector is exactly the right size for the final match. For example,
1881: consider the pattern
1882: <pre>
1883: (a)(?:(b)c|bd)
1884: </pre>
1885: If a vector of 6 elements (allowing for only 1 captured substring) is given
1886: with subject string "abd", <b>pcre_exec()</b> will try to set the second
1887: captured string, thereby recording a vector overflow, before failing to match
1888: "c" and backing up to try the second alternative. The zero return, however,
1889: does correctly indicate that the maximum number of slots (namely 2) have been
1890: filled. In similar cases where there is temporary overflow, but the final
1891: number of used slots is actually less than the maximum, a non-zero value is
1892: returned.
1893: </P>
1894: <P>
1895: The <b>pcre_fullinfo()</b> function can be used to find out how many capturing
1896: subpatterns there are in a compiled pattern. The smallest size for
1897: <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
1898: the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
1899: </P>
1900: <P>
1901: It is possible for capturing subpattern number <i>n+1</i> to match some part of
1902: the subject when subpattern <i>n</i> has not been used at all. For example, if
1903: the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1904: function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1905: happens, both values in the offset pairs corresponding to unused subpatterns
1906: are set to -1.
1907: </P>
1908: <P>
1909: Offset values that correspond to unused subpatterns at the end of the
1910: expression are also set to -1. For example, if the string "abc" is matched
1911: against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1912: return from the function is 2, because the highest used capturing subpattern
1913: number is 1, and the offsets for for the second and third capturing subpatterns
1914: (assuming the vector is large enough, of course) are set to -1.
1915: </P>
1916: <P>
1917: <b>Note</b>: Elements in the first two-thirds of <i>ovector</i> that do not
1918: correspond to capturing parentheses in the pattern are never changed. That is,
1919: if a pattern contains <i>n</i> capturing parentheses, no more than
1920: <i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by <b>pcre_exec()</b>. The other
1921: elements (in the first two-thirds) retain whatever values they previously had.
1922: </P>
1923: <P>
1924: Some convenience functions are provided for extracting the captured substrings
1925: as separate strings. These are described below.
1926: <a name="errorlist"></a></P>
1927: <br><b>
1928: Error return values from <b>pcre_exec()</b>
1929: </b><br>
1930: <P>
1931: If <b>pcre_exec()</b> fails, it returns a negative number. The following are
1932: defined in the header file:
1933: <pre>
1934: PCRE_ERROR_NOMATCH (-1)
1935: </pre>
1936: The subject string did not match the pattern.
1937: <pre>
1938: PCRE_ERROR_NULL (-2)
1939: </pre>
1940: Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
1941: NULL and <i>ovecsize</i> was not zero.
1942: <pre>
1943: PCRE_ERROR_BADOPTION (-3)
1944: </pre>
1945: An unrecognized bit was set in the <i>options</i> argument.
1946: <pre>
1947: PCRE_ERROR_BADMAGIC (-4)
1948: </pre>
1949: PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1950: the case when it is passed a junk pointer and to detect when a pattern that was
1951: compiled in an environment of one endianness is run in an environment with the
1952: other endianness. This is the error that PCRE gives when the magic number is
1953: not present.
1954: <pre>
1955: PCRE_ERROR_UNKNOWN_OPCODE (-5)
1956: </pre>
1957: While running the pattern match, an unknown item was encountered in the
1958: compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1959: of the compiled pattern.
1960: <pre>
1961: PCRE_ERROR_NOMEMORY (-6)
1962: </pre>
1963: If a pattern contains back references, but the <i>ovector</i> that is passed to
1964: <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
1965: gets a block of memory at the start of matching to use for this purpose. If the
1966: call via <b>pcre_malloc()</b> fails, this error is given. The memory is
1967: automatically freed at the end of matching.
1968: </P>
1969: <P>
1970: This error is also given if <b>pcre_stack_malloc()</b> fails in
1971: <b>pcre_exec()</b>. This can happen only when PCRE has been compiled with
1972: <b>--disable-stack-for-recursion</b>.
1973: <pre>
1974: PCRE_ERROR_NOSUBSTRING (-7)
1975: </pre>
1976: This error is used by the <b>pcre_copy_substring()</b>,
1977: <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
1978: below). It is never returned by <b>pcre_exec()</b>.
1979: <pre>
1980: PCRE_ERROR_MATCHLIMIT (-8)
1981: </pre>
1982: The backtracking limit, as specified by the <i>match_limit</i> field in a
1983: <b>pcre_extra</b> structure (or defaulted) was reached. See the description
1984: above.
1985: <pre>
1986: PCRE_ERROR_CALLOUT (-9)
1987: </pre>
1988: This error is never generated by <b>pcre_exec()</b> itself. It is provided for
1989: use by callout functions that want to yield a distinctive error code. See the
1990: <a href="pcrecallout.html"><b>pcrecallout</b></a>
1991: documentation for details.
1992: <pre>
1993: PCRE_ERROR_BADUTF8 (-10)
1994: </pre>
1995: A string that contains an invalid UTF-8 byte sequence was passed as a subject,
1996: and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
1997: (<i>ovecsize</i>) is at least 2, the byte offset to the start of the the invalid
1998: UTF-8 character is placed in the first element, and a reason code is placed in
1999: the second element. The reason codes are listed in the
2000: <a href="#badutf8reasons">following section.</a>
2001: For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
2002: truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
2003: PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2004: <pre>
2005: PCRE_ERROR_BADUTF8_OFFSET (-11)
2006: </pre>
2007: The UTF-8 byte sequence that was passed as a subject was checked and found to
2008: be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
2009: <i>startoffset</i> did not point to the beginning of a UTF-8 character or the
2010: end of the subject.
2011: <pre>
2012: PCRE_ERROR_PARTIAL (-12)
2013: </pre>
2014: The subject string did not match, but it did match partially. See the
2015: <a href="pcrepartial.html"><b>pcrepartial</b></a>
2016: documentation for details of partial matching.
2017: <pre>
2018: PCRE_ERROR_BADPARTIAL (-13)
2019: </pre>
2020: This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
2021: option was used with a compiled pattern containing items that were not
2022: supported for partial matching. From release 8.00 onwards, there are no
2023: restrictions on partial matching.
2024: <pre>
2025: PCRE_ERROR_INTERNAL (-14)
2026: </pre>
2027: An unexpected internal error has occurred. This error could be caused by a bug
2028: in PCRE or by overwriting of the compiled pattern.
2029: <pre>
2030: PCRE_ERROR_BADCOUNT (-15)
2031: </pre>
2032: This error is given if the value of the <i>ovecsize</i> argument is negative.
2033: <pre>
2034: PCRE_ERROR_RECURSIONLIMIT (-21)
2035: </pre>
2036: The internal recursion limit, as specified by the <i>match_limit_recursion</i>
2037: field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
2038: description above.
2039: <pre>
2040: PCRE_ERROR_BADNEWLINE (-23)
2041: </pre>
2042: An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given.
2043: <pre>
2044: PCRE_ERROR_BADOFFSET (-24)
2045: </pre>
2046: The value of <i>startoffset</i> was negative or greater than the length of the
2047: subject, that is, the value in <i>length</i>.
2048: <pre>
2049: PCRE_ERROR_SHORTUTF8 (-25)
2050: </pre>
2051: This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2052: ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2053: Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2054: fact sufficient to detect this case, but this special error code for
2055: PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2056: retained for backwards compatibility.
2057: <pre>
2058: PCRE_ERROR_RECURSELOOP (-26)
2059: </pre>
2060: This error is returned when <b>pcre_exec()</b> detects a recursion loop within
2061: the pattern. Specifically, it means that either the whole pattern or a
2062: subpattern has been called recursively for the second time at the same position
2063: in the subject string. Some simple patterns that might do this are detected and
2064: faulted at compile time, but more complicated cases, in particular mutual
2065: recursions between two different subpatterns, cannot be detected until run
2066: time.
2067: <pre>
2068: PCRE_ERROR_JIT_STACKLIMIT (-27)
2069: </pre>
2070: This error is returned when a pattern that was successfully studied using the
2071: PCRE_STUDY_JIT_COMPILE option is being matched, but the memory available for
2072: the just-in-time processing stack is not large enough. See the
2073: <a href="pcrejit.html"><b>pcrejit</b></a>
2074: documentation for more details.
1.1.1.2 ! misho 2075: <pre>
! 2076: PCRE_ERROR_BADMODE (-28)
! 2077: </pre>
! 2078: This error is given if a pattern that was compiled by the 8-bit library is
! 2079: passed to a 16-bit library function, or vice versa.
! 2080: <pre>
! 2081: PCRE_ERROR_BADENDIANNESS (-29)
! 2082: </pre>
! 2083: This error is given if a pattern that was compiled and saved is reloaded on a
! 2084: host with different endianness. The utility function
! 2085: <b>pcre_pattern_to_host_byte_order()</b> can be used to convert such a pattern
! 2086: so that it runs on the new host.
1.1 misho 2087: </P>
2088: <P>
2089: Error numbers -16 to -20 and -22 are not used by <b>pcre_exec()</b>.
2090: <a name="badutf8reasons"></a></P>
2091: <br><b>
2092: Reason codes for invalid UTF-8 strings
2093: </b><br>
2094: <P>
1.1.1.2 ! misho 2095: This section applies only to the 8-bit library. The corresponding information
! 2096: for the 16-bit library is given in the
! 2097: <a href="pcre16.html"><b>pcre16</b></a>
! 2098: page.
! 2099: </P>
! 2100: <P>
1.1 misho 2101: When <b>pcre_exec()</b> returns either PCRE_ERROR_BADUTF8 or
2102: PCRE_ERROR_SHORTUTF8, and the size of the output vector (<i>ovecsize</i>) is at
2103: least 2, the offset of the start of the invalid UTF-8 character is placed in
2104: the first output vector element (<i>ovector[0]</i>) and a reason code is placed
2105: in the second element (<i>ovector[1]</i>). The reason codes are given names in
2106: the <b>pcre.h</b> header file:
2107: <pre>
2108: PCRE_UTF8_ERR1
2109: PCRE_UTF8_ERR2
2110: PCRE_UTF8_ERR3
2111: PCRE_UTF8_ERR4
2112: PCRE_UTF8_ERR5
2113: </pre>
2114: The string ends with a truncated UTF-8 character; the code specifies how many
2115: bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2116: no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2117: allows for up to 6 bytes, and this is checked first; hence the possibility of
2118: 4 or 5 missing bytes.
2119: <pre>
2120: PCRE_UTF8_ERR6
2121: PCRE_UTF8_ERR7
2122: PCRE_UTF8_ERR8
2123: PCRE_UTF8_ERR9
2124: PCRE_UTF8_ERR10
2125: </pre>
2126: The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2127: character do not have the binary value 0b10 (that is, either the most
2128: significant bit is 0, or the next bit is 1).
2129: <pre>
2130: PCRE_UTF8_ERR11
2131: PCRE_UTF8_ERR12
2132: </pre>
2133: A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2134: these code points are excluded by RFC 3629.
2135: <pre>
2136: PCRE_UTF8_ERR13
2137: </pre>
2138: A 4-byte character has a value greater than 0x10fff; these code points are
2139: excluded by RFC 3629.
2140: <pre>
2141: PCRE_UTF8_ERR14
2142: </pre>
2143: A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2144: code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2145: from UTF-8.
2146: <pre>
2147: PCRE_UTF8_ERR15
2148: PCRE_UTF8_ERR16
2149: PCRE_UTF8_ERR17
2150: PCRE_UTF8_ERR18
2151: PCRE_UTF8_ERR19
2152: </pre>
2153: A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2154: value that can be represented by fewer bytes, which is invalid. For example,
2155: the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2156: one byte.
2157: <pre>
2158: PCRE_UTF8_ERR20
2159: </pre>
2160: The two most significant bits of the first byte of a character have the binary
2161: value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2162: byte can only validly occur as the second or subsequent byte of a multi-byte
2163: character.
2164: <pre>
2165: PCRE_UTF8_ERR21
2166: </pre>
2167: The first byte of a character has the value 0xfe or 0xff. These values can
2168: never occur in a valid UTF-8 string.
2169: </P>
1.1.1.2 ! misho 2170: <br><a name="SEC18" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
1.1 misho 2171: <P>
2172: <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
2173: <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
2174: <b>int <i>buffersize</i>);</b>
2175: </P>
2176: <P>
2177: <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
2178: <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
2179: <b>const char **<i>stringptr</i>);</b>
2180: </P>
2181: <P>
2182: <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
2183: <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
2184: </P>
2185: <P>
2186: Captured substrings can be accessed directly by using the offsets returned by
2187: <b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions
2188: <b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and
2189: <b>pcre_get_substring_list()</b> are provided for extracting captured substrings
2190: as new, separate, zero-terminated strings. These functions identify substrings
2191: by number. The next section describes functions for extracting named
2192: substrings.
2193: </P>
2194: <P>
2195: A substring that contains a binary zero is correctly extracted and has a
2196: further zero added on the end, but the result is not, of course, a C string.
2197: However, you can process such a string by referring to the length that is
2198: returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>.
2199: Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate
2200: for handling strings containing binary zeros, because the end of the final
2201: string is not independently indicated.
2202: </P>
2203: <P>
2204: The first three arguments are the same for all three of these functions:
2205: <i>subject</i> is the subject string that has just been successfully matched,
2206: <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
2207: <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
2208: captured by the match, including the substring that matched the entire regular
2209: expression. This is the value returned by <b>pcre_exec()</b> if it is greater
2210: than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
2211: space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
2212: number of elements in the vector divided by three.
2213: </P>
2214: <P>
2215: The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
2216: extract a single substring, whose number is given as <i>stringnumber</i>. A
2217: value of zero extracts the substring that matched the entire pattern, whereas
2218: higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
2219: the string is placed in <i>buffer</i>, whose length is given by
2220: <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
2221: obtained via <b>pcre_malloc</b>, and its address is returned via
2222: <i>stringptr</i>. The yield of the function is the length of the string, not
2223: including the terminating zero, or one of these error codes:
2224: <pre>
2225: PCRE_ERROR_NOMEMORY (-6)
2226: </pre>
2227: The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
2228: memory failed for <b>pcre_get_substring()</b>.
2229: <pre>
2230: PCRE_ERROR_NOSUBSTRING (-7)
2231: </pre>
2232: There is no substring whose number is <i>stringnumber</i>.
2233: </P>
2234: <P>
2235: The <b>pcre_get_substring_list()</b> function extracts all available substrings
2236: and builds a list of pointers to them. All this is done in a single block of
2237: memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
2238: is returned via <i>listptr</i>, which is also the start of the list of string
2239: pointers. The end of the list is marked by a NULL pointer. The yield of the
2240: function is zero if all went well, or the error code
2241: <pre>
2242: PCRE_ERROR_NOMEMORY (-6)
2243: </pre>
2244: if the attempt to get the memory block failed.
2245: </P>
2246: <P>
2247: When any of these functions encounter a substring that is unset, which can
2248: happen when capturing subpattern number <i>n+1</i> matches some part of the
2249: subject, but subpattern <i>n</i> has not been used at all, they return an empty
2250: string. This can be distinguished from a genuine zero-length substring by
2251: inspecting the appropriate offset in <i>ovector</i>, which is negative for unset
2252: substrings.
2253: </P>
2254: <P>
2255: The two convenience functions <b>pcre_free_substring()</b> and
2256: <b>pcre_free_substring_list()</b> can be used to free the memory returned by
2257: a previous call of <b>pcre_get_substring()</b> or
2258: <b>pcre_get_substring_list()</b>, respectively. They do nothing more than call
2259: the function pointed to by <b>pcre_free</b>, which of course could be called
2260: directly from a C program. However, PCRE is used in some situations where it is
2261: linked via a special interface to another programming language that cannot use
2262: <b>pcre_free</b> directly; it is for these cases that the functions are
2263: provided.
2264: </P>
1.1.1.2 ! misho 2265: <br><a name="SEC19" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
1.1 misho 2266: <P>
2267: <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
2268: <b>const char *<i>name</i>);</b>
2269: </P>
2270: <P>
2271: <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
2272: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
2273: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
2274: <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
2275: </P>
2276: <P>
2277: <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
2278: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
2279: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
2280: <b>const char **<i>stringptr</i>);</b>
2281: </P>
2282: <P>
2283: To extract a substring by name, you first have to find associated number.
2284: For example, for this pattern
2285: <pre>
2286: (a+)b(?<xxx>\d+)...
2287: </pre>
2288: the number of the subpattern called "xxx" is 2. If the name is known to be
2289: unique (PCRE_DUPNAMES was not set), you can find the number from the name by
2290: calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled
2291: pattern, and the second is the name. The yield of the function is the
2292: subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2293: that name.
2294: </P>
2295: <P>
2296: Given the number, you can extract the substring directly, or use one of the
2297: functions described in the previous section. For convenience, there are also
2298: two functions that do the whole job.
2299: </P>
2300: <P>
2301: Most of the arguments of <b>pcre_copy_named_substring()</b> and
2302: <b>pcre_get_named_substring()</b> are the same as those for the similarly named
2303: functions that extract by number. As these are described in the previous
2304: section, they are not re-described here. There are just two differences:
2305: </P>
2306: <P>
2307: First, instead of a substring number, a substring name is given. Second, there
2308: is an extra argument, given at the start, which is a pointer to the compiled
2309: pattern. This is needed in order to gain access to the name-to-number
2310: translation table.
2311: </P>
2312: <P>
2313: These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they
2314: then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as
2315: appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names,
2316: the behaviour may not be what you want (see the next section).
2317: </P>
2318: <P>
2319: <b>Warning:</b> If the pattern uses the (?| feature to set up multiple
2320: subpatterns with the same number, as described in the
2321: <a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
2322: in the
2323: <a href="pcrepattern.html"><b>pcrepattern</b></a>
2324: page, you cannot use names to distinguish the different subpatterns, because
2325: names are not included in the compiled code. The matching process uses only
2326: numbers. For this reason, the use of different names for subpatterns of the
2327: same number causes an error at compile time.
2328: </P>
1.1.1.2 ! misho 2329: <br><a name="SEC20" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
1.1 misho 2330: <P>
2331: <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
2332: <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
2333: </P>
2334: <P>
2335: When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2336: are not required to be unique. (Duplicate names are always allowed for
2337: subpatterns with the same number, created by using the (?| feature. Indeed, if
2338: such subpatterns are named, they are required to use the same names.)
2339: </P>
2340: <P>
2341: Normally, patterns with duplicate names are such that in any one match, only
2342: one of the named subpatterns participates. An example is shown in the
2343: <a href="pcrepattern.html"><b>pcrepattern</b></a>
2344: documentation.
2345: </P>
2346: <P>
2347: When duplicates are present, <b>pcre_copy_named_substring()</b> and
2348: <b>pcre_get_named_substring()</b> return the first substring corresponding to
2349: the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2350: returned; no data is returned. The <b>pcre_get_stringnumber()</b> function
2351: returns one of the numbers that are associated with the name, but it is not
2352: defined which it is.
2353: </P>
2354: <P>
2355: If you want to get full details of all captured substrings for a given name,
2356: you must use the <b>pcre_get_stringtable_entries()</b> function. The first
2357: argument is the compiled pattern, and the second is the name. The third and
2358: fourth are pointers to variables which are updated by the function. After it
2359: has run, they point to the first and last entries in the name-to-number table
2360: for the given name. The function itself returns the length of each entry, or
2361: PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2362: described above in the section entitled <i>Information about a pattern</i>
2363: <a href="#infoaboutpattern">above.</a>
2364: Given all the relevant entries for the name, you can extract each of their
2365: numbers, and hence the captured data, if any.
2366: </P>
1.1.1.2 ! misho 2367: <br><a name="SEC21" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
1.1 misho 2368: <P>
2369: The traditional matching function uses a similar algorithm to Perl, which stops
2370: when it finds the first match, starting at a given point in the subject. If you
2371: want to find all possible matches, or the longest possible match, consider
2372: using the alternative matching function (see below) instead. If you cannot use
2373: the alternative function, but still need to find all possible matches, you
2374: can kludge it up by making use of the callout facility, which is described in
2375: the
2376: <a href="pcrecallout.html"><b>pcrecallout</b></a>
2377: documentation.
2378: </P>
2379: <P>
2380: What you have to do is to insert a callout right at the end of the pattern.
2381: When your callout function is called, extract and save the current matched
2382: substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
2383: other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
2384: will yield PCRE_ERROR_NOMATCH.
1.1.1.2 ! misho 2385: </P>
! 2386: <br><a name="SEC22" href="#TOC1">OBTAINING AN ESTIMATE OF STACK USAGE</a><br>
! 2387: <P>
! 2388: Matching certain patterns using <b>pcre_exec()</b> can use a lot of process
! 2389: stack, which in certain environments can be rather limited in size. Some users
! 2390: find it helpful to have an estimate of the amount of stack that is used by
! 2391: <b>pcre_exec()</b>, to help them set recursion limits, as described in the
! 2392: <a href="pcrestack.html"><b>pcrestack</b></a>
! 2393: documentation. The estimate that is output by <b>pcretest</b> when called with
! 2394: the <b>-m</b> and <b>-C</b> options is obtained by calling <b>pcre_exec</b> with
! 2395: the values NULL, NULL, NULL, -999, and -999 for its first five arguments.
! 2396: </P>
! 2397: <P>
! 2398: Normally, if its first argument is NULL, <b>pcre_exec()</b> immediately returns
! 2399: the negative error code PCRE_ERROR_NULL, but with this special combination of
! 2400: arguments, it returns instead a negative number whose absolute value is the
! 2401: approximate stack frame size in bytes. (A negative number is used so that it is
! 2402: clear that no match has happened.) The value is approximate because in some
! 2403: cases, recursive calls to <b>pcre_exec()</b> occur when there are one or two
! 2404: additional variables on the stack.
! 2405: </P>
! 2406: <P>
! 2407: If PCRE has been compiled to use the heap instead of the stack for recursion,
! 2408: the value returned is the size of each block that is obtained from the heap.
1.1 misho 2409: <a name="dfamatch"></a></P>
1.1.1.2 ! misho 2410: <br><a name="SEC23" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
1.1 misho 2411: <P>
2412: <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
2413: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
2414: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
2415: <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
2416: </P>
2417: <P>
2418: The function <b>pcre_dfa_exec()</b> is called to match a subject string against
2419: a compiled pattern, using a matching algorithm that scans the subject string
2420: just once, and does not backtrack. This has different characteristics to the
2421: normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2422: patterns are not supported. Nevertheless, there are times when this kind of
2423: matching can be useful. For a discussion of the two matching algorithms, and a
2424: list of features that <b>pcre_dfa_exec()</b> does not support, see the
2425: <a href="pcrematching.html"><b>pcrematching</b></a>
2426: documentation.
2427: </P>
2428: <P>
2429: The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
2430: <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
2431: different way, and this is described below. The other common arguments are used
2432: in the same way as for <b>pcre_exec()</b>, so their description is not repeated
2433: here.
2434: </P>
2435: <P>
2436: The two additional arguments provide workspace for the function. The workspace
2437: vector should contain at least 20 elements. It is used for keeping track of
2438: multiple paths through the pattern tree. More workspace will be needed for
2439: patterns and subjects where there are a lot of potential matches.
2440: </P>
2441: <P>
2442: Here is an example of a simple call to <b>pcre_dfa_exec()</b>:
2443: <pre>
2444: int rc;
2445: int ovector[10];
2446: int wspace[20];
2447: rc = pcre_dfa_exec(
2448: re, /* result of pcre_compile() */
2449: NULL, /* we didn't study the pattern */
2450: "some string", /* the subject string */
2451: 11, /* the length of the subject string */
2452: 0, /* start at offset 0 in the subject */
2453: 0, /* default options */
2454: ovector, /* vector of integers for substring information */
2455: 10, /* number of elements (NOT size in bytes) */
2456: wspace, /* working space vector */
2457: 20); /* number of elements (NOT size in bytes) */
2458: </PRE>
2459: </P>
2460: <br><b>
2461: Option bits for <b>pcre_dfa_exec()</b>
2462: </b><br>
2463: <P>
2464: The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
2465: zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
2466: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2467: PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2468: PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2469: All but the last four of these are exactly the same as for <b>pcre_exec()</b>,
2470: so their description is not repeated here.
2471: <pre>
2472: PCRE_PARTIAL_HARD
2473: PCRE_PARTIAL_SOFT
2474: </pre>
2475: These have the same general effect as they do for <b>pcre_exec()</b>, but the
2476: details are slightly different. When PCRE_PARTIAL_HARD is set for
2477: <b>pcre_dfa_exec()</b>, it returns PCRE_ERROR_PARTIAL if the end of the subject
2478: is reached and there is still at least one matching possibility that requires
2479: additional characters. This happens even if some complete matches have also
2480: been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2481: is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2482: there have been no complete matches, but there is still at least one matching
2483: possibility. The portion of the string that was inspected when the longest
2484: partial match was found is set as the first matching string in both cases.
2485: There is a more detailed discussion of partial and multi-segment matching, with
2486: examples, in the
2487: <a href="pcrepartial.html"><b>pcrepartial</b></a>
2488: documentation.
2489: <pre>
2490: PCRE_DFA_SHORTEST
2491: </pre>
2492: Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2493: soon as it has found one match. Because of the way the alternative algorithm
2494: works, this is necessarily the shortest possible match at the first possible
2495: matching point in the subject string.
2496: <pre>
2497: PCRE_DFA_RESTART
2498: </pre>
2499: When <b>pcre_dfa_exec()</b> returns a partial match, it is possible to call it
2500: again, with additional subject characters, and have it continue with the same
2501: match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2502: <i>workspace</i> and <i>wscount</i> options must reference the same vector as
2503: before because data about the match so far is left in them after a partial
2504: match. There is more discussion of this facility in the
2505: <a href="pcrepartial.html"><b>pcrepartial</b></a>
2506: documentation.
2507: </P>
2508: <br><b>
2509: Successful returns from <b>pcre_dfa_exec()</b>
2510: </b><br>
2511: <P>
2512: When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
2513: substring in the subject. Note, however, that all the matches from one run of
2514: the function start at the same point in the subject. The shorter matches are
2515: all initial substrings of the longer matches. For example, if the pattern
2516: <pre>
2517: <.*>
2518: </pre>
2519: is matched against the string
2520: <pre>
2521: This is <something> <something else> <something further> no more
2522: </pre>
2523: the three matched strings are
2524: <pre>
2525: <something>
2526: <something> <something else>
2527: <something> <something else> <something further>
2528: </pre>
2529: On success, the yield of the function is a number greater than zero, which is
2530: the number of matched substrings. The substrings themselves are returned in
2531: <i>ovector</i>. Each string uses two elements; the first is the offset to the
2532: start, and the second is the offset to the end. In fact, all the strings have
2533: the same start offset. (Space could have been saved by giving this only once,
2534: but it was decided to retain some compatibility with the way <b>pcre_exec()</b>
2535: returns data, even though the meaning of the strings is different.)
2536: </P>
2537: <P>
2538: The strings are returned in reverse order of length; that is, the longest
2539: matching string is given first. If there were too many matches to fit into
2540: <i>ovector</i>, the yield of the function is zero, and the vector is filled with
2541: the longest matches. Unlike <b>pcre_exec()</b>, <b>pcre_dfa_exec()</b> can use
2542: the entire <i>ovector</i> for returning matched strings.
2543: </P>
2544: <br><b>
2545: Error returns from <b>pcre_dfa_exec()</b>
2546: </b><br>
2547: <P>
2548: The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
2549: Many of the errors are the same as for <b>pcre_exec()</b>, and these are
2550: described
2551: <a href="#errorlist">above.</a>
2552: There are in addition the following errors that are specific to
2553: <b>pcre_dfa_exec()</b>:
2554: <pre>
2555: PCRE_ERROR_DFA_UITEM (-16)
2556: </pre>
2557: This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
2558: that it does not support, for instance, the use of \C or a back reference.
2559: <pre>
2560: PCRE_ERROR_DFA_UCOND (-17)
2561: </pre>
2562: This return is given if <b>pcre_dfa_exec()</b> encounters a condition item that
2563: uses a back reference for the condition, or a test for recursion in a specific
2564: group. These are not supported.
2565: <pre>
2566: PCRE_ERROR_DFA_UMLIMIT (-18)
2567: </pre>
2568: This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
2569: block that contains a setting of the <i>match_limit</i> or
2570: <i>match_limit_recursion</i> fields. This is not supported (these fields are
2571: meaningless for DFA matching).
2572: <pre>
2573: PCRE_ERROR_DFA_WSSIZE (-19)
2574: </pre>
2575: This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
2576: <i>workspace</i> vector.
2577: <pre>
2578: PCRE_ERROR_DFA_RECURSE (-20)
2579: </pre>
2580: When a recursive subpattern is processed, the matching function calls itself
2581: recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
2582: error is given if the output vector is not large enough. This should be
2583: extremely rare, as a vector of size 1000 is used.
2584: </P>
1.1.1.2 ! misho 2585: <br><a name="SEC24" href="#TOC1">SEE ALSO</a><br>
1.1 misho 2586: <P>
1.1.1.2 ! misho 2587: <b>pcre16</b>(3), <b>pcrebuild</b>(3), <b>pcrecallout</b>(3), <b>pcrecpp(3)</b>(3),
1.1 misho 2588: <b>pcrematching</b>(3), <b>pcrepartial</b>(3), <b>pcreposix</b>(3),
2589: <b>pcreprecompile</b>(3), <b>pcresample</b>(3), <b>pcrestack</b>(3).
2590: </P>
1.1.1.2 ! misho 2591: <br><a name="SEC25" href="#TOC1">AUTHOR</a><br>
1.1 misho 2592: <P>
2593: Philip Hazel
2594: <br>
2595: University Computing Service
2596: <br>
2597: Cambridge CB2 3QH, England.
2598: <br>
2599: </P>
1.1.1.2 ! misho 2600: <br><a name="SEC26" href="#TOC1">REVISION</a><br>
1.1 misho 2601: <P>
1.1.1.2 ! misho 2602: Last updated: 21 January 2012
1.1 misho 2603: <br>
1.1.1.2 ! misho 2604: Copyright © 1997-2012 University of Cambridge.
1.1 misho 2605: <br>
2606: <p>
2607: Return to the <a href="index.html">PCRE index page</a>.
2608: </p>
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