Annotation of embedaddon/pcre/doc/html/pcreapi.html, revision 1.1.1.5
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>
1.1.1.4 misho 20: <li><a name="TOC5" href="#SEC5">PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a>
1.1.1.2 misho 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>
1.1.1.5 ! misho 49: <b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
! 50: <b> const unsigned char *<i>tableptr</i>);</b>
! 51: <br>
! 52: <br>
1.1 misho 53: <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
1.1.1.5 ! misho 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: <br>
! 58: <br>
1.1 misho 59: <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
1.1.1.5 ! misho 60: <b> const char **<i>errptr</i>);</b>
! 61: <br>
! 62: <br>
1.1 misho 63: <b>void pcre_free_study(pcre_extra *<i>extra</i>);</b>
1.1.1.5 ! misho 64: <br>
! 65: <br>
1.1 misho 66: <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1.1.1.5 ! misho 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: <br>
! 70: <br>
1.1 misho 71: <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1.1.1.5 ! misho 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>
1.1 misho 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>
1.1.1.5 ! misho 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: <br>
! 83: <br>
1.1 misho 84: <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1.1.1.5 ! misho 85: <b> int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
! 86: <b> int <i>buffersize</i>);</b>
! 87: <br>
! 88: <br>
1.1 misho 89: <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
1.1.1.5 ! misho 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: <br>
! 94: <br>
1.1 misho 95: <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
1.1.1.5 ! misho 96: <b> const char *<i>name</i>);</b>
! 97: <br>
! 98: <br>
1.1 misho 99: <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
1.1.1.5 ! misho 100: <b> const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
! 101: <br>
! 102: <br>
1.1 misho 103: <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1.1.1.5 ! misho 104: <b> int <i>stringcount</i>, int <i>stringnumber</i>,</b>
! 105: <b> const char **<i>stringptr</i>);</b>
! 106: <br>
! 107: <br>
1.1 misho 108: <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
1.1.1.5 ! misho 109: <b> int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
! 110: <br>
! 111: <br>
1.1 misho 112: <b>void pcre_free_substring(const char *<i>stringptr</i>);</b>
1.1.1.5 ! misho 113: <br>
! 114: <br>
1.1 misho 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>
1.1.1.4 misho 119: <b>int pcre_jit_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1.1.1.5 ! misho 120: <b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
! 121: <b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
! 122: <b> pcre_jit_stack *<i>jstack</i>);</b>
! 123: <br>
! 124: <br>
1.1.1.2 misho 125: <b>pcre_jit_stack *pcre_jit_stack_alloc(int <i>startsize</i>, int <i>maxsize</i>);</b>
1.1.1.5 ! misho 126: <br>
! 127: <br>
1.1.1.2 misho 128: <b>void pcre_jit_stack_free(pcre_jit_stack *<i>stack</i>);</b>
1.1.1.5 ! misho 129: <br>
! 130: <br>
1.1.1.2 misho 131: <b>void pcre_assign_jit_stack(pcre_extra *<i>extra</i>,</b>
1.1.1.5 ! misho 132: <b> pcre_jit_callback <i>callback</i>, void *<i>data</i>);</b>
! 133: <br>
! 134: <br>
1.1 misho 135: <b>const unsigned char *pcre_maketables(void);</b>
1.1.1.5 ! misho 136: <br>
! 137: <br>
1.1 misho 138: <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1.1.1.5 ! misho 139: <b> int <i>what</i>, void *<i>where</i>);</b>
! 140: <br>
! 141: <br>
1.1 misho 142: <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
1.1.1.5 ! misho 143: <br>
! 144: <br>
1.1 misho 145: <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
1.1.1.5 ! misho 146: <br>
! 147: <br>
1.1.1.2 misho 148: <b>const char *pcre_version(void);</b>
1.1.1.5 ! misho 149: <br>
! 150: <br>
1.1.1.2 misho 151: <b>int pcre_pattern_to_host_byte_order(pcre *<i>code</i>,</b>
1.1.1.5 ! misho 152: <b> pcre_extra *<i>extra</i>, const unsigned char *<i>tables</i>);</b>
1.1.1.2 misho 153: </P>
154: <br><a name="SEC4" href="#TOC1">PCRE NATIVE API INDIRECTED FUNCTIONS</a><br>
1.1 misho 155: <P>
156: <b>void *(*pcre_malloc)(size_t);</b>
1.1.1.5 ! misho 157: <br>
! 158: <br>
1.1 misho 159: <b>void (*pcre_free)(void *);</b>
1.1.1.5 ! misho 160: <br>
! 161: <br>
1.1 misho 162: <b>void *(*pcre_stack_malloc)(size_t);</b>
1.1.1.5 ! misho 163: <br>
! 164: <br>
1.1 misho 165: <b>void (*pcre_stack_free)(void *);</b>
1.1.1.5 ! misho 166: <br>
! 167: <br>
1.1 misho 168: <b>int (*pcre_callout)(pcre_callout_block *);</b>
169: </P>
1.1.1.4 misho 170: <br><a name="SEC5" href="#TOC1">PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a><br>
1.1.1.2 misho 171: <P>
1.1.1.4 misho 172: As well as support for 8-bit character strings, PCRE also supports 16-bit
173: strings (from release 8.30) and 32-bit strings (from release 8.32), by means of
174: two additional libraries. They can be built as well as, or instead of, the
175: 8-bit library. To avoid too much complication, this document describes the
176: 8-bit versions of the functions, with only occasional references to the 16-bit
177: and 32-bit libraries.
178: </P>
179: <P>
180: The 16-bit and 32-bit functions operate in the same way as their 8-bit
181: counterparts; they just use different data types for their arguments and
182: results, and their names start with <b>pcre16_</b> or <b>pcre32_</b> instead of
183: <b>pcre_</b>. For every option that has UTF8 in its name (for example,
184: PCRE_UTF8), there are corresponding 16-bit and 32-bit names with UTF8 replaced
185: by UTF16 or UTF32, respectively. This facility is in fact just cosmetic; the
186: 16-bit and 32-bit option names define the same bit values.
1.1.1.2 misho 187: </P>
188: <P>
189: References to bytes and UTF-8 in this document should be read as references to
1.1.1.4 misho 190: 16-bit data units and UTF-16 when using the 16-bit library, or 32-bit data
191: units and UTF-32 when using the 32-bit library, unless specified otherwise.
192: More details of the specific differences for the 16-bit and 32-bit libraries
193: are given in the
1.1.1.2 misho 194: <a href="pcre16.html"><b>pcre16</b></a>
1.1.1.4 misho 195: and
196: <a href="pcre32.html"><b>pcre32</b></a>
197: pages.
1.1.1.2 misho 198: </P>
199: <br><a name="SEC6" href="#TOC1">PCRE API OVERVIEW</a><br>
1.1 misho 200: <P>
201: PCRE has its own native API, which is described in this document. There are
1.1.1.2 misho 202: also some wrapper functions (for the 8-bit library only) that correspond to the
203: POSIX regular expression API, but they do not give access to all the
204: functionality. They are described in the
1.1 misho 205: <a href="pcreposix.html"><b>pcreposix</b></a>
206: documentation. Both of these APIs define a set of C function calls. A C++
1.1.1.2 misho 207: wrapper (again for the 8-bit library only) is also distributed with PCRE. It is
208: documented in the
1.1 misho 209: <a href="pcrecpp.html"><b>pcrecpp</b></a>
210: page.
211: </P>
212: <P>
213: The native API C function prototypes are defined in the header file
1.1.1.2 misho 214: <b>pcre.h</b>, and on Unix-like systems the (8-bit) library itself is called
215: <b>libpcre</b>. It can normally be accessed by adding <b>-lpcre</b> to the
216: command for linking an application that uses PCRE. The header file defines the
217: macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers
218: for the library. Applications can use these to include support for different
219: releases of PCRE.
1.1 misho 220: </P>
221: <P>
222: In a Windows environment, if you want to statically link an application program
223: against a non-dll <b>pcre.a</b> file, you must define PCRE_STATIC before
224: including <b>pcre.h</b> or <b>pcrecpp.h</b>, because otherwise the
225: <b>pcre_malloc()</b> and <b>pcre_free()</b> exported functions will be declared
226: <b>__declspec(dllimport)</b>, with unwanted results.
227: </P>
228: <P>
229: The functions <b>pcre_compile()</b>, <b>pcre_compile2()</b>, <b>pcre_study()</b>,
230: and <b>pcre_exec()</b> are used for compiling and matching regular expressions
231: in a Perl-compatible manner. A sample program that demonstrates the simplest
232: way of using them is provided in the file called <i>pcredemo.c</i> in the PCRE
233: source distribution. A listing of this program is given in the
234: <a href="pcredemo.html"><b>pcredemo</b></a>
235: documentation, and the
236: <a href="pcresample.html"><b>pcresample</b></a>
237: documentation describes how to compile and run it.
238: </P>
239: <P>
240: Just-in-time compiler support is an optional feature of PCRE that can be built
241: in appropriate hardware environments. It greatly speeds up the matching
242: performance of many patterns. Simple programs can easily request that it be
243: used if available, by setting an option that is ignored when it is not
244: relevant. More complicated programs might need to make use of the functions
245: <b>pcre_jit_stack_alloc()</b>, <b>pcre_jit_stack_free()</b>, and
246: <b>pcre_assign_jit_stack()</b> in order to control the JIT code's memory usage.
1.1.1.4 misho 247: </P>
248: <P>
249: From release 8.32 there is also a direct interface for JIT execution, which
250: gives improved performance. The JIT-specific functions are discussed in the
1.1 misho 251: <a href="pcrejit.html"><b>pcrejit</b></a>
252: documentation.
253: </P>
254: <P>
255: A second matching function, <b>pcre_dfa_exec()</b>, which is not
256: Perl-compatible, is also provided. This uses a different algorithm for the
257: matching. The alternative algorithm finds all possible matches (at a given
258: point in the subject), and scans the subject just once (unless there are
259: lookbehind assertions). However, this algorithm does not return captured
260: substrings. A description of the two matching algorithms and their advantages
261: and disadvantages is given in the
262: <a href="pcrematching.html"><b>pcrematching</b></a>
263: documentation.
264: </P>
265: <P>
266: In addition to the main compiling and matching functions, there are convenience
267: functions for extracting captured substrings from a subject string that is
268: matched by <b>pcre_exec()</b>. They are:
269: <pre>
270: <b>pcre_copy_substring()</b>
271: <b>pcre_copy_named_substring()</b>
272: <b>pcre_get_substring()</b>
273: <b>pcre_get_named_substring()</b>
274: <b>pcre_get_substring_list()</b>
275: <b>pcre_get_stringnumber()</b>
276: <b>pcre_get_stringtable_entries()</b>
277: </pre>
278: <b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also
279: provided, to free the memory used for extracted strings.
280: </P>
281: <P>
282: The function <b>pcre_maketables()</b> is used to build a set of character tables
283: in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>,
284: or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for
285: specialist use. Most commonly, no special tables are passed, in which case
286: internal tables that are generated when PCRE is built are used.
287: </P>
288: <P>
289: The function <b>pcre_fullinfo()</b> is used to find out information about a
1.1.1.2 misho 290: compiled pattern. The function <b>pcre_version()</b> returns a pointer to a
291: string containing the version of PCRE and its date of release.
1.1 misho 292: </P>
293: <P>
294: The function <b>pcre_refcount()</b> maintains a reference count in a data block
295: containing a compiled pattern. This is provided for the benefit of
296: object-oriented applications.
297: </P>
298: <P>
299: The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain
300: the entry points of the standard <b>malloc()</b> and <b>free()</b> functions,
301: respectively. PCRE calls the memory management functions via these variables,
302: so a calling program can replace them if it wishes to intercept the calls. This
303: should be done before calling any PCRE functions.
304: </P>
305: <P>
306: The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also
307: indirections to memory management functions. These special functions are used
308: only when PCRE is compiled to use the heap for remembering data, instead of
309: recursive function calls, when running the <b>pcre_exec()</b> function. See the
310: <a href="pcrebuild.html"><b>pcrebuild</b></a>
311: documentation for details of how to do this. It is a non-standard way of
312: building PCRE, for use in environments that have limited stacks. Because of the
313: greater use of memory management, it runs more slowly. Separate functions are
314: provided so that special-purpose external code can be used for this case. When
315: used, these functions are always called in a stack-like manner (last obtained,
316: first freed), and always for memory blocks of the same size. There is a
317: discussion about PCRE's stack usage in the
318: <a href="pcrestack.html"><b>pcrestack</b></a>
319: documentation.
320: </P>
321: <P>
322: The global variable <b>pcre_callout</b> initially contains NULL. It can be set
323: by the caller to a "callout" function, which PCRE will then call at specified
324: points during a matching operation. Details are given in the
325: <a href="pcrecallout.html"><b>pcrecallout</b></a>
326: documentation.
327: <a name="newlines"></a></P>
1.1.1.2 misho 328: <br><a name="SEC7" href="#TOC1">NEWLINES</a><br>
1.1 misho 329: <P>
330: PCRE supports five different conventions for indicating line breaks in
331: strings: a single CR (carriage return) character, a single LF (linefeed)
332: character, the two-character sequence CRLF, any of the three preceding, or any
333: Unicode newline sequence. The Unicode newline sequences are the three just
1.1.1.3 misho 334: mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed,
1.1 misho 335: U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
336: (paragraph separator, U+2029).
337: </P>
338: <P>
339: Each of the first three conventions is used by at least one operating system as
340: its standard newline sequence. When PCRE is built, a default can be specified.
341: The default default is LF, which is the Unix standard. When PCRE is run, the
342: default can be overridden, either when a pattern is compiled, or when it is
343: matched.
344: </P>
345: <P>
346: At compile time, the newline convention can be specified by the <i>options</i>
347: argument of <b>pcre_compile()</b>, or it can be specified by special text at the
348: start of the pattern itself; this overrides any other settings. See the
349: <a href="pcrepattern.html"><b>pcrepattern</b></a>
350: page for details of the special character sequences.
351: </P>
352: <P>
353: In the PCRE documentation the word "newline" is used to mean "the character or
354: pair of characters that indicate a line break". The choice of newline
355: convention affects the handling of the dot, circumflex, and dollar
356: metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
357: recognized line ending sequence, the match position advancement for a
358: non-anchored pattern. There is more detail about this in the
359: <a href="#execoptions">section on <b>pcre_exec()</b> options</a>
360: below.
361: </P>
362: <P>
363: The choice of newline convention does not affect the interpretation of
364: the \n or \r escape sequences, nor does it affect what \R matches, which is
365: controlled in a similar way, but by separate options.
366: </P>
1.1.1.2 misho 367: <br><a name="SEC8" href="#TOC1">MULTITHREADING</a><br>
1.1 misho 368: <P>
369: The PCRE functions can be used in multi-threading applications, with the
370: proviso that the memory management functions pointed to by <b>pcre_malloc</b>,
371: <b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the
372: callout function pointed to by <b>pcre_callout</b>, are shared by all threads.
373: </P>
374: <P>
375: The compiled form of a regular expression is not altered during matching, so
376: the same compiled pattern can safely be used by several threads at once.
377: </P>
378: <P>
379: If the just-in-time optimization feature is being used, it needs separate
380: memory stack areas for each thread. See the
381: <a href="pcrejit.html"><b>pcrejit</b></a>
382: documentation for more details.
383: </P>
1.1.1.2 misho 384: <br><a name="SEC9" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br>
1.1 misho 385: <P>
386: The compiled form of a regular expression can be saved and re-used at a later
387: time, possibly by a different program, and even on a host other than the one on
388: which it was compiled. Details are given in the
389: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1.1.1.2 misho 390: documentation, which includes a description of the
391: <b>pcre_pattern_to_host_byte_order()</b> function. However, compiling a regular
392: expression with one version of PCRE for use with a different version is not
393: guaranteed to work and may cause crashes.
1.1 misho 394: </P>
1.1.1.2 misho 395: <br><a name="SEC10" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
1.1 misho 396: <P>
397: <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
398: </P>
399: <P>
400: The function <b>pcre_config()</b> makes it possible for a PCRE client to
401: discover which optional features have been compiled into the PCRE library. The
402: <a href="pcrebuild.html"><b>pcrebuild</b></a>
403: documentation has more details about these optional features.
404: </P>
405: <P>
406: The first argument for <b>pcre_config()</b> is an integer, specifying which
407: information is required; the second argument is a pointer to a variable into
1.1.1.2 misho 408: which the information is placed. The returned value is zero on success, or the
409: negative error code PCRE_ERROR_BADOPTION if the value in the first argument is
410: not recognized. The following information is available:
1.1 misho 411: <pre>
412: PCRE_CONFIG_UTF8
413: </pre>
414: The output is an integer that is set to one if UTF-8 support is available;
1.1.1.4 misho 415: otherwise it is set to zero. This value should normally be given to the 8-bit
416: version of this function, <b>pcre_config()</b>. If it is given to the 16-bit
417: or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION.
1.1.1.2 misho 418: <pre>
419: PCRE_CONFIG_UTF16
420: </pre>
421: The output is an integer that is set to one if UTF-16 support is available;
422: otherwise it is set to zero. This value should normally be given to the 16-bit
423: version of this function, <b>pcre16_config()</b>. If it is given to the 8-bit
1.1.1.4 misho 424: or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION.
425: <pre>
426: PCRE_CONFIG_UTF32
427: </pre>
428: The output is an integer that is set to one if UTF-32 support is available;
429: otherwise it is set to zero. This value should normally be given to the 32-bit
430: version of this function, <b>pcre32_config()</b>. If it is given to the 8-bit
431: or 16-bit version of this function, the result is PCRE_ERROR_BADOPTION.
1.1 misho 432: <pre>
433: PCRE_CONFIG_UNICODE_PROPERTIES
434: </pre>
435: The output is an integer that is set to one if support for Unicode character
436: properties is available; otherwise it is set to zero.
437: <pre>
438: PCRE_CONFIG_JIT
439: </pre>
440: The output is an integer that is set to one if support for just-in-time
441: compiling is available; otherwise it is set to zero.
442: <pre>
1.1.1.2 misho 443: PCRE_CONFIG_JITTARGET
444: </pre>
445: The output is a pointer to a zero-terminated "const char *" string. If JIT
446: support is available, the string contains the name of the architecture for
447: which the JIT compiler is configured, for example "x86 32bit (little endian +
448: unaligned)". If JIT support is not available, the result is NULL.
449: <pre>
1.1 misho 450: PCRE_CONFIG_NEWLINE
451: </pre>
452: The output is an integer whose value specifies the default character sequence
1.1.1.4 misho 453: that is recognized as meaning "newline". The values that are supported in
454: ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for
455: ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, ANYCRLF, and ANY yield the
456: same values. However, the value for LF is normally 21, though some EBCDIC
457: environments use 37. The corresponding values for CRLF are 3349 and 3365. The
458: default should normally correspond to the standard sequence for your operating
459: system.
1.1 misho 460: <pre>
461: PCRE_CONFIG_BSR
462: </pre>
463: The output is an integer whose value indicates what character sequences the \R
464: escape sequence matches by default. A value of 0 means that \R matches any
465: Unicode line ending sequence; a value of 1 means that \R matches only CR, LF,
466: or CRLF. The default can be overridden when a pattern is compiled or matched.
467: <pre>
468: PCRE_CONFIG_LINK_SIZE
469: </pre>
470: The output is an integer that contains the number of bytes used for internal
1.1.1.2 misho 471: linkage in compiled regular expressions. For the 8-bit library, the value can
472: be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still
1.1.1.4 misho 473: a number of bytes. For the 32-bit library, the value is either 2 or 4 and is
474: still a number of bytes. The default value of 2 is sufficient for all but the
475: most massive patterns, since it allows the compiled pattern to be up to 64K in
476: size. Larger values allow larger regular expressions to be compiled, at the
477: expense of slower matching.
1.1 misho 478: <pre>
479: PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
480: </pre>
481: The output is an integer that contains the threshold above which the POSIX
482: interface uses <b>malloc()</b> for output vectors. Further details are given in
483: the
484: <a href="pcreposix.html"><b>pcreposix</b></a>
485: documentation.
486: <pre>
1.1.1.5 ! misho 487: PCRE_CONFIG_PARENS_LIMIT
! 488: </pre>
! 489: The output is a long integer that gives the maximum depth of nesting of
! 490: parentheses (of any kind) in a pattern. This limit is imposed to cap the amount
! 491: of system stack used when a pattern is compiled. It is specified when PCRE is
! 492: built; the default is 250.
! 493: <pre>
1.1 misho 494: PCRE_CONFIG_MATCH_LIMIT
495: </pre>
496: The output is a long integer that gives the default limit for the number of
497: internal matching function calls in a <b>pcre_exec()</b> execution. Further
498: details are given with <b>pcre_exec()</b> below.
499: <pre>
500: PCRE_CONFIG_MATCH_LIMIT_RECURSION
501: </pre>
502: The output is a long integer that gives the default limit for the depth of
503: recursion when calling the internal matching function in a <b>pcre_exec()</b>
504: execution. Further details are given with <b>pcre_exec()</b> below.
505: <pre>
506: PCRE_CONFIG_STACKRECURSE
507: </pre>
508: The output is an integer that is set to one if internal recursion when running
509: <b>pcre_exec()</b> is implemented by recursive function calls that use the stack
510: to remember their state. This is the usual way that PCRE is compiled. The
511: output is zero if PCRE was compiled to use blocks of data on the heap instead
512: of recursive function calls. In this case, <b>pcre_stack_malloc</b> and
513: <b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus
514: avoiding the use of the stack.
515: </P>
1.1.1.2 misho 516: <br><a name="SEC11" href="#TOC1">COMPILING A PATTERN</a><br>
1.1 misho 517: <P>
518: <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
1.1.1.5 ! misho 519: <b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
! 520: <b> const unsigned char *<i>tableptr</i>);</b>
! 521: <br>
! 522: <br>
1.1 misho 523: <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
1.1.1.5 ! misho 524: <b> int *<i>errorcodeptr</i>,</b>
! 525: <b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
! 526: <b> const unsigned char *<i>tableptr</i>);</b>
1.1 misho 527: </P>
528: <P>
529: Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be
530: called to compile a pattern into an internal form. The only difference between
531: the two interfaces is that <b>pcre_compile2()</b> has an additional argument,
532: <i>errorcodeptr</i>, via which a numerical error code can be returned. To avoid
533: too much repetition, we refer just to <b>pcre_compile()</b> below, but the
534: information applies equally to <b>pcre_compile2()</b>.
535: </P>
536: <P>
537: The pattern is a C string terminated by a binary zero, and is passed in the
538: <i>pattern</i> argument. A pointer to a single block of memory that is obtained
539: via <b>pcre_malloc</b> is returned. This contains the compiled code and related
540: data. The <b>pcre</b> type is defined for the returned block; this is a typedef
541: for a structure whose contents are not externally defined. It is up to the
542: caller to free the memory (via <b>pcre_free</b>) when it is no longer required.
543: </P>
544: <P>
545: Although the compiled code of a PCRE regex is relocatable, that is, it does not
546: depend on memory location, the complete <b>pcre</b> data block is not
547: fully relocatable, because it may contain a copy of the <i>tableptr</i>
548: argument, which is an address (see below).
549: </P>
550: <P>
551: The <i>options</i> argument contains various bit settings that affect the
552: compilation. It should be zero if no options are required. The available
553: options are described below. Some of them (in particular, those that are
554: compatible with Perl, but some others as well) can also be set and unset from
555: within the pattern (see the detailed description in the
556: <a href="pcrepattern.html"><b>pcrepattern</b></a>
557: documentation). For those options that can be different in different parts of
558: the pattern, the contents of the <i>options</i> argument specifies their
559: settings at the start of compilation and execution. The PCRE_ANCHORED,
560: PCRE_BSR_<i>xxx</i>, PCRE_NEWLINE_<i>xxx</i>, PCRE_NO_UTF8_CHECK, and
1.1.1.3 misho 561: PCRE_NO_START_OPTIMIZE options can be set at the time of matching as well as at
1.1 misho 562: compile time.
563: </P>
564: <P>
565: If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately.
566: Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns
567: NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual
568: error message. This is a static string that is part of the library. You must
569: not try to free it. Normally, the offset from the start of the pattern to the
1.1.1.4 misho 570: data unit that was being processed when the error was discovered is placed in
571: the variable pointed to by <i>erroffset</i>, which must not be NULL (if it is,
572: an immediate error is given). However, for an invalid UTF-8 or UTF-16 string,
573: the offset is that of the first data unit of the failing character.
1.1 misho 574: </P>
575: <P>
1.1.1.2 misho 576: Some errors are not detected until the whole pattern has been scanned; in these
577: cases, the offset passed back is the length of the pattern. Note that the
1.1.1.4 misho 578: offset is in data units, not characters, even in a UTF mode. It may sometimes
579: point into the middle of a UTF-8 or UTF-16 character.
1.1 misho 580: </P>
581: <P>
582: If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
583: <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
584: returned via this argument in the event of an error. This is in addition to the
585: textual error message. Error codes and messages are listed below.
586: </P>
587: <P>
588: If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
589: character tables that are built when PCRE is compiled, using the default C
590: locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
591: call to <b>pcre_maketables()</b>. This value is stored with the compiled
1.1.1.5 ! misho 592: pattern, and used again by <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b> when the
! 593: pattern is matched. For more discussion, see the section on locale support
! 594: below.
1.1 misho 595: </P>
596: <P>
597: This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
598: <pre>
599: pcre *re;
600: const char *error;
601: int erroffset;
602: re = pcre_compile(
603: "^A.*Z", /* the pattern */
604: 0, /* default options */
605: &error, /* for error message */
606: &erroffset, /* for error offset */
607: NULL); /* use default character tables */
608: </pre>
609: The following names for option bits are defined in the <b>pcre.h</b> header
610: file:
611: <pre>
612: PCRE_ANCHORED
613: </pre>
614: If this bit is set, the pattern is forced to be "anchored", that is, it is
615: constrained to match only at the first matching point in the string that is
616: being searched (the "subject string"). This effect can also be achieved by
617: appropriate constructs in the pattern itself, which is the only way to do it in
618: Perl.
619: <pre>
620: PCRE_AUTO_CALLOUT
621: </pre>
622: If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
623: all with number 255, before each pattern item. For discussion of the callout
624: facility, see the
625: <a href="pcrecallout.html"><b>pcrecallout</b></a>
626: documentation.
627: <pre>
628: PCRE_BSR_ANYCRLF
629: PCRE_BSR_UNICODE
630: </pre>
631: These options (which are mutually exclusive) control what the \R escape
632: sequence matches. The choice is either to match only CR, LF, or CRLF, or to
633: match any Unicode newline sequence. The default is specified when PCRE is
634: built. It can be overridden from within the pattern, or by setting an option
635: when a compiled pattern is matched.
636: <pre>
637: PCRE_CASELESS
638: </pre>
639: If this bit is set, letters in the pattern match both upper and lower case
640: letters. It is equivalent to Perl's /i option, and it can be changed within a
641: pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
642: concept of case for characters whose values are less than 128, so caseless
643: matching is always possible. For characters with higher values, the concept of
644: case is supported if PCRE is compiled with Unicode property support, but not
645: otherwise. If you want to use caseless matching for characters 128 and above,
646: you must ensure that PCRE is compiled with Unicode property support as well as
647: with UTF-8 support.
648: <pre>
649: PCRE_DOLLAR_ENDONLY
650: </pre>
651: If this bit is set, a dollar metacharacter in the pattern matches only at the
652: end of the subject string. Without this option, a dollar also matches
653: immediately before a newline at the end of the string (but not before any other
654: newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
655: There is no equivalent to this option in Perl, and no way to set it within a
656: pattern.
657: <pre>
658: PCRE_DOTALL
659: </pre>
660: If this bit is set, a dot metacharacter in the pattern matches a character of
661: any value, including one that indicates a newline. However, it only ever
662: matches one character, even if newlines are coded as CRLF. Without this option,
663: a dot does not match when the current position is at a newline. This option is
664: equivalent to Perl's /s option, and it can be changed within a pattern by a
665: (?s) option setting. A negative class such as [^a] always matches newline
666: characters, independent of the setting of this option.
667: <pre>
668: PCRE_DUPNAMES
669: </pre>
670: If this bit is set, names used to identify capturing subpatterns need not be
671: unique. This can be helpful for certain types of pattern when it is known that
672: only one instance of the named subpattern can ever be matched. There are more
673: details of named subpatterns below; see also the
674: <a href="pcrepattern.html"><b>pcrepattern</b></a>
675: documentation.
676: <pre>
677: PCRE_EXTENDED
678: </pre>
1.1.1.5 ! misho 679: If this bit is set, most white space characters in the pattern are totally
! 680: ignored except when escaped or inside a character class. However, white space
! 681: is not allowed within sequences such as (?> that introduce various
! 682: parenthesized subpatterns, nor within a numerical quantifier such as {1,3}.
! 683: However, ignorable white space is permitted between an item and a following
! 684: quantifier and between a quantifier and a following + that indicates
! 685: possessiveness.
! 686: </P>
! 687: <P>
! 688: White space did not used to include the VT character (code 11), because Perl
! 689: did not treat this character as white space. However, Perl changed at release
! 690: 5.18, so PCRE followed at release 8.34, and VT is now treated as white space.
! 691: </P>
! 692: <P>
! 693: PCRE_EXTENDED also causes characters between an unescaped # outside a character
! 694: class and the next newline, inclusive, to be ignored. PCRE_EXTENDED is
! 695: equivalent to Perl's /x option, and it can be changed within a pattern by a
! 696: (?x) option setting.
1.1 misho 697: </P>
698: <P>
699: Which characters are interpreted as newlines is controlled by the options
700: passed to <b>pcre_compile()</b> or by a special sequence at the start of the
701: pattern, as described in the section entitled
702: <a href="pcrepattern.html#newlines">"Newline conventions"</a>
703: in the <b>pcrepattern</b> documentation. Note that the end of this type of
704: comment is a literal newline sequence in the pattern; escape sequences that
705: happen to represent a newline do not count.
706: </P>
707: <P>
708: This option makes it possible to include comments inside complicated patterns.
1.1.1.3 misho 709: Note, however, that this applies only to data characters. White space characters
1.1 misho 710: may never appear within special character sequences in a pattern, for example
711: within the sequence (?( that introduces a conditional subpattern.
712: <pre>
713: PCRE_EXTRA
714: </pre>
715: This option was invented in order to turn on additional functionality of PCRE
716: that is incompatible with Perl, but it is currently of very little use. When
717: set, any backslash in a pattern that is followed by a letter that has no
718: special meaning causes an error, thus reserving these combinations for future
719: expansion. By default, as in Perl, a backslash followed by a letter with no
720: special meaning is treated as a literal. (Perl can, however, be persuaded to
721: give an error for this, by running it with the -w option.) There are at present
722: no other features controlled by this option. It can also be set by a (?X)
723: option setting within a pattern.
724: <pre>
725: PCRE_FIRSTLINE
726: </pre>
727: If this option is set, an unanchored pattern is required to match before or at
728: the first newline in the subject string, though the matched text may continue
729: over the newline.
730: <pre>
731: PCRE_JAVASCRIPT_COMPAT
732: </pre>
733: If this option is set, PCRE's behaviour is changed in some ways so that it is
734: compatible with JavaScript rather than Perl. The changes are as follows:
735: </P>
736: <P>
737: (1) A lone closing square bracket in a pattern causes a compile-time error,
738: because this is illegal in JavaScript (by default it is treated as a data
739: character). Thus, the pattern AB]CD becomes illegal when this option is set.
740: </P>
741: <P>
742: (2) At run time, a back reference to an unset subpattern group matches an empty
743: string (by default this causes the current matching alternative to fail). A
744: pattern such as (\1)(a) succeeds when this option is set (assuming it can find
745: an "a" in the subject), whereas it fails by default, for Perl compatibility.
746: </P>
747: <P>
748: (3) \U matches an upper case "U" character; by default \U causes a compile
749: time error (Perl uses \U to upper case subsequent characters).
750: </P>
751: <P>
752: (4) \u matches a lower case "u" character unless it is followed by four
753: hexadecimal digits, in which case the hexadecimal number defines the code point
754: to match. By default, \u causes a compile time error (Perl uses it to upper
755: case the following character).
756: </P>
757: <P>
758: (5) \x matches a lower case "x" character unless it is followed by two
759: hexadecimal digits, in which case the hexadecimal number defines the code point
760: to match. By default, as in Perl, a hexadecimal number is always expected after
761: \x, but it may have zero, one, or two digits (so, for example, \xz matches a
762: binary zero character followed by z).
763: <pre>
764: PCRE_MULTILINE
765: </pre>
1.1.1.4 misho 766: By default, for the purposes of matching "start of line" and "end of line",
767: PCRE treats the subject string as consisting of a single line of characters,
768: even if it actually contains newlines. The "start of line" metacharacter (^)
769: matches only at the start of the string, and the "end of line" metacharacter
770: ($) matches only at the end of the string, or before a terminating newline
771: (except when PCRE_DOLLAR_ENDONLY is set). Note, however, that unless
772: PCRE_DOTALL is set, the "any character" metacharacter (.) does not match at a
773: newline. This behaviour (for ^, $, and dot) is the same as Perl.
1.1 misho 774: </P>
775: <P>
776: When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
777: match immediately following or immediately before internal newlines in the
778: subject string, respectively, as well as at the very start and end. This is
779: equivalent to Perl's /m option, and it can be changed within a pattern by a
780: (?m) option setting. If there are no newlines in a subject string, or no
781: occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
782: <pre>
1.1.1.4 misho 783: PCRE_NEVER_UTF
784: </pre>
785: This option locks out interpretation of the pattern as UTF-8 (or UTF-16 or
786: UTF-32 in the 16-bit and 32-bit libraries). In particular, it prevents the
787: creator of the pattern from switching to UTF interpretation by starting the
788: pattern with (*UTF). This may be useful in applications that process patterns
789: from external sources. The combination of PCRE_UTF8 and PCRE_NEVER_UTF also
790: causes an error.
791: <pre>
1.1 misho 792: PCRE_NEWLINE_CR
793: PCRE_NEWLINE_LF
794: PCRE_NEWLINE_CRLF
795: PCRE_NEWLINE_ANYCRLF
796: PCRE_NEWLINE_ANY
797: </pre>
798: These options override the default newline definition that was chosen when PCRE
799: was built. Setting the first or the second specifies that a newline is
800: indicated by a single character (CR or LF, respectively). Setting
801: PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
802: CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
803: preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
1.1.1.4 misho 804: that any Unicode newline sequence should be recognized.
805: </P>
806: <P>
807: In an ASCII/Unicode environment, the Unicode newline sequences are the three
808: just mentioned, plus the single characters VT (vertical tab, U+000B), FF (form
809: feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
810: (paragraph separator, U+2029). For the 8-bit library, the last two are
811: recognized only in UTF-8 mode.
812: </P>
813: <P>
814: When PCRE is compiled to run in an EBCDIC (mainframe) environment, the code for
815: CR is 0x0d, the same as ASCII. However, the character code for LF is normally
816: 0x15, though in some EBCDIC environments 0x25 is used. Whichever of these is
817: not LF is made to correspond to Unicode's NEL character. EBCDIC codes are all
818: less than 256. For more details, see the
819: <a href="pcrebuild.html"><b>pcrebuild</b></a>
820: documentation.
1.1 misho 821: </P>
822: <P>
823: The newline setting in the options word uses three bits that are treated
824: as a number, giving eight possibilities. Currently only six are used (default
825: plus the five values above). This means that if you set more than one newline
826: option, the combination may or may not be sensible. For example,
827: PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
828: other combinations may yield unused numbers and cause an error.
829: </P>
830: <P>
831: The only time that a line break in a pattern is specially recognized when
1.1.1.3 misho 832: compiling is when PCRE_EXTENDED is set. CR and LF are white space characters,
1.1 misho 833: and so are ignored in this mode. Also, an unescaped # outside a character class
834: indicates a comment that lasts until after the next line break sequence. In
835: other circumstances, line break sequences in patterns are treated as literal
836: data.
837: </P>
838: <P>
839: The newline option that is set at compile time becomes the default that is used
840: for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden.
841: <pre>
842: PCRE_NO_AUTO_CAPTURE
843: </pre>
844: If this option is set, it disables the use of numbered capturing parentheses in
845: the pattern. Any opening parenthesis that is not followed by ? behaves as if it
846: were followed by ?: but named parentheses can still be used for capturing (and
847: they acquire numbers in the usual way). There is no equivalent of this option
848: in Perl.
849: <pre>
1.1.1.5 ! misho 850: PCRE_NO_AUTO_POSSESS
! 851: </pre>
! 852: If this option is set, it disables "auto-possessification". This is an
! 853: optimization that, for example, turns a+b into a++b in order to avoid
! 854: backtracks into a+ that can never be successful. However, if callouts are in
! 855: use, auto-possessification means that some of them are never taken. You can set
! 856: this option if you want the matching functions to do a full unoptimized search
! 857: and run all the callouts, but it is mainly provided for testing purposes.
! 858: <pre>
1.1.1.4 misho 859: PCRE_NO_START_OPTIMIZE
1.1 misho 860: </pre>
861: This is an option that acts at matching time; that is, it is really an option
862: for <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. If it is set at compile time,
1.1.1.4 misho 863: it is remembered with the compiled pattern and assumed at matching time. This
864: is necessary if you want to use JIT execution, because the JIT compiler needs
865: to know whether or not this option is set. For details see the discussion of
866: PCRE_NO_START_OPTIMIZE
1.1 misho 867: <a href="#execoptions">below.</a>
868: <pre>
869: PCRE_UCP
870: </pre>
871: This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W,
872: \w, and some of the POSIX character classes. By default, only ASCII characters
873: are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
874: classify characters. More details are given in the section on
875: <a href="pcre.html#genericchartypes">generic character types</a>
876: in the
877: <a href="pcrepattern.html"><b>pcrepattern</b></a>
878: page. If you set PCRE_UCP, matching one of the items it affects takes much
879: longer. The option is available only if PCRE has been compiled with Unicode
880: property support.
881: <pre>
882: PCRE_UNGREEDY
883: </pre>
884: This option inverts the "greediness" of the quantifiers so that they are not
885: greedy by default, but become greedy if followed by "?". It is not compatible
886: with Perl. It can also be set by a (?U) option setting within the pattern.
887: <pre>
888: PCRE_UTF8
889: </pre>
890: This option causes PCRE to regard both the pattern and the subject as strings
1.1.1.2 misho 891: of UTF-8 characters instead of single-byte strings. However, it is available
892: only when PCRE is built to include UTF support. If not, the use of this option
893: provokes an error. Details of how this option changes the behaviour of PCRE are
894: given in the
1.1 misho 895: <a href="pcreunicode.html"><b>pcreunicode</b></a>
896: page.
897: <pre>
898: PCRE_NO_UTF8_CHECK
899: </pre>
1.1.1.4 misho 900: When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
901: automatically checked. There is a discussion about the
1.1.1.2 misho 902: <a href="pcreunicode.html#utf8strings">validity of UTF-8 strings</a>
903: in the
904: <a href="pcreunicode.html"><b>pcreunicode</b></a>
905: page. If an invalid UTF-8 sequence is found, <b>pcre_compile()</b> returns an
906: error. If you already know that your pattern is valid, and you want to skip
907: this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option.
908: When it is set, the effect of passing an invalid UTF-8 string as a pattern is
1.1.1.5 ! misho 909: undefined. It may cause your program to crash or loop. Note that this option
! 910: can also be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress
! 911: the validity checking of subject strings only. If the same string is being
! 912: matched many times, the option can be safely set for the second and subsequent
1.1.1.4 misho 913: matchings to improve performance.
1.1 misho 914: </P>
1.1.1.2 misho 915: <br><a name="SEC12" href="#TOC1">COMPILATION ERROR CODES</a><br>
1.1 misho 916: <P>
917: The following table lists the error codes than may be returned by
918: <b>pcre_compile2()</b>, along with the error messages that may be returned by
1.1.1.2 misho 919: both compiling functions. Note that error messages are always 8-bit ASCII
1.1.1.4 misho 920: strings, even in 16-bit or 32-bit mode. As PCRE has developed, some error codes
921: have fallen out of use. To avoid confusion, they have not been re-used.
1.1 misho 922: <pre>
923: 0 no error
924: 1 \ at end of pattern
925: 2 \c at end of pattern
926: 3 unrecognized character follows \
927: 4 numbers out of order in {} quantifier
928: 5 number too big in {} quantifier
929: 6 missing terminating ] for character class
930: 7 invalid escape sequence in character class
931: 8 range out of order in character class
932: 9 nothing to repeat
933: 10 [this code is not in use]
934: 11 internal error: unexpected repeat
935: 12 unrecognized character after (? or (?-
936: 13 POSIX named classes are supported only within a class
937: 14 missing )
938: 15 reference to non-existent subpattern
939: 16 erroffset passed as NULL
940: 17 unknown option bit(s) set
941: 18 missing ) after comment
942: 19 [this code is not in use]
943: 20 regular expression is too large
944: 21 failed to get memory
945: 22 unmatched parentheses
946: 23 internal error: code overflow
947: 24 unrecognized character after (?<
948: 25 lookbehind assertion is not fixed length
949: 26 malformed number or name after (?(
950: 27 conditional group contains more than two branches
951: 28 assertion expected after (?(
952: 29 (?R or (?[+-]digits must be followed by )
953: 30 unknown POSIX class name
954: 31 POSIX collating elements are not supported
1.1.1.2 misho 955: 32 this version of PCRE is compiled without UTF support
1.1 misho 956: 33 [this code is not in use]
1.1.1.5 ! misho 957: 34 character value in \x{} or \o{} is too large
1.1 misho 958: 35 invalid condition (?(0)
959: 36 \C not allowed in lookbehind assertion
960: 37 PCRE does not support \L, \l, \N{name}, \U, or \u
961: 38 number after (?C is > 255
962: 39 closing ) for (?C expected
963: 40 recursive call could loop indefinitely
964: 41 unrecognized character after (?P
965: 42 syntax error in subpattern name (missing terminator)
966: 43 two named subpatterns have the same name
1.1.1.2 misho 967: 44 invalid UTF-8 string (specifically UTF-8)
1.1 misho 968: 45 support for \P, \p, and \X has not been compiled
969: 46 malformed \P or \p sequence
970: 47 unknown property name after \P or \p
971: 48 subpattern name is too long (maximum 32 characters)
972: 49 too many named subpatterns (maximum 10000)
973: 50 [this code is not in use]
1.1.1.2 misho 974: 51 octal value is greater than \377 in 8-bit non-UTF-8 mode
1.1 misho 975: 52 internal error: overran compiling workspace
976: 53 internal error: previously-checked referenced subpattern
977: not found
978: 54 DEFINE group contains more than one branch
979: 55 repeating a DEFINE group is not allowed
980: 56 inconsistent NEWLINE options
981: 57 \g is not followed by a braced, angle-bracketed, or quoted
982: name/number or by a plain number
983: 58 a numbered reference must not be zero
984: 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1.1.1.4 misho 985: 60 (*VERB) not recognized or malformed
1.1 misho 986: 61 number is too big
987: 62 subpattern name expected
988: 63 digit expected after (?+
989: 64 ] is an invalid data character in JavaScript compatibility mode
990: 65 different names for subpatterns of the same number are
991: not allowed
992: 66 (*MARK) must have an argument
1.1.1.2 misho 993: 67 this version of PCRE is not compiled with Unicode property
994: support
1.1 misho 995: 68 \c must be followed by an ASCII character
996: 69 \k is not followed by a braced, angle-bracketed, or quoted name
1.1.1.2 misho 997: 70 internal error: unknown opcode in find_fixedlength()
998: 71 \N is not supported in a class
999: 72 too many forward references
1000: 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
1001: 74 invalid UTF-16 string (specifically UTF-16)
1.1.1.3 misho 1002: 75 name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
1003: 76 character value in \u.... sequence is too large
1.1.1.4 misho 1004: 77 invalid UTF-32 string (specifically UTF-32)
1.1.1.5 ! misho 1005: 78 setting UTF is disabled by the application
! 1006: 79 non-hex character in \x{} (closing brace missing?)
! 1007: 80 non-octal character in \o{} (closing brace missing?)
! 1008: 81 missing opening brace after \o
! 1009: 82 parentheses are too deeply nested
! 1010: 83 invalid range in character class
1.1 misho 1011: </pre>
1012: The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
1013: be used if the limits were changed when PCRE was built.
1014: <a name="studyingapattern"></a></P>
1.1.1.2 misho 1015: <br><a name="SEC13" href="#TOC1">STUDYING A PATTERN</a><br>
1.1 misho 1016: <P>
1.1.1.5 ! misho 1017: <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
! 1018: <b> const char **<i>errptr</i>);</b>
1.1 misho 1019: </P>
1020: <P>
1021: If a compiled pattern is going to be used several times, it is worth spending
1022: more time analyzing it in order to speed up the time taken for matching. The
1023: function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
1024: argument. If studying the pattern produces additional information that will
1025: help speed up matching, <b>pcre_study()</b> returns a pointer to a
1026: <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
1027: results of the study.
1028: </P>
1029: <P>
1030: The returned value from <b>pcre_study()</b> can be passed directly to
1031: <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. However, a <b>pcre_extra</b> block
1032: also contains other fields that can be set by the caller before the block is
1033: passed; these are described
1034: <a href="#extradata">below</a>
1035: in the section on matching a pattern.
1036: </P>
1037: <P>
1038: If studying the pattern does not produce any useful information,
1.1.1.4 misho 1039: <b>pcre_study()</b> returns NULL by default. In that circumstance, if the
1040: calling program wants to pass any of the other fields to <b>pcre_exec()</b> or
1041: <b>pcre_dfa_exec()</b>, it must set up its own <b>pcre_extra</b> block. However,
1042: if <b>pcre_study()</b> is called with the PCRE_STUDY_EXTRA_NEEDED option, it
1043: returns a <b>pcre_extra</b> block even if studying did not find any additional
1044: information. It may still return NULL, however, if an error occurs in
1045: <b>pcre_study()</b>.
1.1 misho 1046: </P>
1047: <P>
1.1.1.3 misho 1048: The second argument of <b>pcre_study()</b> contains option bits. There are three
1.1.1.4 misho 1049: further options in addition to PCRE_STUDY_EXTRA_NEEDED:
1.1.1.3 misho 1050: <pre>
1051: PCRE_STUDY_JIT_COMPILE
1052: PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
1053: PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
1054: </pre>
1055: If any of these are set, and the just-in-time compiler is available, the
1056: pattern is further compiled into machine code that executes much faster than
1057: the <b>pcre_exec()</b> interpretive matching function. If the just-in-time
1.1.1.4 misho 1058: compiler is not available, these options are ignored. All undefined bits in the
1.1.1.3 misho 1059: <i>options</i> argument must be zero.
1.1 misho 1060: </P>
1061: <P>
1062: JIT compilation is a heavyweight optimization. It can take some time for
1063: patterns to be analyzed, and for one-off matches and simple patterns the
1064: benefit of faster execution might be offset by a much slower study time.
1065: Not all patterns can be optimized by the JIT compiler. For those that cannot be
1066: handled, matching automatically falls back to the <b>pcre_exec()</b>
1067: interpreter. For more details, see the
1068: <a href="pcrejit.html"><b>pcrejit</b></a>
1069: documentation.
1070: </P>
1071: <P>
1072: The third argument for <b>pcre_study()</b> is a pointer for an error message. If
1073: studying succeeds (even if no data is returned), the variable it points to is
1074: set to NULL. Otherwise it is set to point to a textual error message. This is a
1075: static string that is part of the library. You must not try to free it. You
1076: should test the error pointer for NULL after calling <b>pcre_study()</b>, to be
1077: sure that it has run successfully.
1078: </P>
1079: <P>
1080: When you are finished with a pattern, you can free the memory used for the
1081: study data by calling <b>pcre_free_study()</b>. This function was added to the
1082: API for release 8.20. For earlier versions, the memory could be freed with
1083: <b>pcre_free()</b>, just like the pattern itself. This will still work in cases
1.1.1.3 misho 1084: where JIT optimization is not used, but it is advisable to change to the new
1085: function when convenient.
1.1 misho 1086: </P>
1087: <P>
1088: This is a typical way in which <b>pcre_study</b>() is used (except that in a
1089: real application there should be tests for errors):
1090: <pre>
1091: int rc;
1092: pcre *re;
1093: pcre_extra *sd;
1094: re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1095: sd = pcre_study(
1096: re, /* result of pcre_compile() */
1097: 0, /* no options */
1098: &error); /* set to NULL or points to a message */
1099: rc = pcre_exec( /* see below for details of pcre_exec() options */
1100: re, sd, "subject", 7, 0, 0, ovector, 30);
1101: ...
1102: pcre_free_study(sd);
1103: pcre_free(re);
1104: </pre>
1105: Studying a pattern does two things: first, a lower bound for the length of
1106: subject string that is needed to match the pattern is computed. This does not
1107: mean that there are any strings of that length that match, but it does
1.1.1.4 misho 1108: guarantee that no shorter strings match. The value is used to avoid wasting
1109: time by trying to match strings that are shorter than the lower bound. You can
1110: find out the value in a calling program via the <b>pcre_fullinfo()</b> function.
1.1 misho 1111: </P>
1112: <P>
1113: Studying a pattern is also useful for non-anchored patterns that do not have a
1114: single fixed starting character. A bitmap of possible starting bytes is
1115: created. This speeds up finding a position in the subject at which to start
1.1.1.4 misho 1116: matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256.
1117: In 32-bit mode, the bitmap is used for 32-bit values less than 256.)
1.1 misho 1118: </P>
1119: <P>
1120: These two optimizations apply to both <b>pcre_exec()</b> and
1.1.1.3 misho 1121: <b>pcre_dfa_exec()</b>, and the information is also used by the JIT compiler.
1.1.1.4 misho 1122: The optimizations can be disabled by setting the PCRE_NO_START_OPTIMIZE option.
1123: You might want to do this if your pattern contains callouts or (*MARK) and you
1124: want to make use of these facilities in cases where matching fails.
1125: </P>
1126: <P>
1127: PCRE_NO_START_OPTIMIZE can be specified at either compile time or execution
1128: time. However, if PCRE_NO_START_OPTIMIZE is passed to <b>pcre_exec()</b>, (that
1129: is, after any JIT compilation has happened) JIT execution is disabled. For JIT
1130: execution to work with PCRE_NO_START_OPTIMIZE, the option must be set at
1131: compile time.
1132: </P>
1133: <P>
1134: There is a longer discussion of PCRE_NO_START_OPTIMIZE
1.1 misho 1135: <a href="#execoptions">below.</a>
1136: <a name="localesupport"></a></P>
1.1.1.2 misho 1137: <br><a name="SEC14" href="#TOC1">LOCALE SUPPORT</a><br>
1.1 misho 1138: <P>
1139: PCRE handles caseless matching, and determines whether characters are letters,
1140: digits, or whatever, by reference to a set of tables, indexed by character
1.1.1.5 ! misho 1141: code point. When running in UTF-8 mode, or in the 16- or 32-bit libraries, this
! 1142: applies only to characters with code points less than 256. By default,
! 1143: higher-valued code points never match escapes such as \w or \d. However, if
! 1144: PCRE is built with Unicode property support, all characters can be tested with
! 1145: \p and \P, or, alternatively, the PCRE_UCP option can be set when a pattern
! 1146: is compiled; this causes \w and friends to use Unicode property support
! 1147: instead of the built-in tables.
! 1148: </P>
! 1149: <P>
! 1150: The use of locales with Unicode is discouraged. If you are handling characters
! 1151: with code points greater than 128, you should either use Unicode support, or
! 1152: use locales, but not try to mix the two.
1.1 misho 1153: </P>
1154: <P>
1155: PCRE contains an internal set of tables that are used when the final argument
1156: of <b>pcre_compile()</b> is NULL. These are sufficient for many applications.
1157: Normally, the internal tables recognize only ASCII characters. However, when
1158: PCRE is built, it is possible to cause the internal tables to be rebuilt in the
1159: default "C" locale of the local system, which may cause them to be different.
1160: </P>
1161: <P>
1162: The internal tables can always be overridden by tables supplied by the
1163: application that calls PCRE. These may be created in a different locale from
1164: the default. As more and more applications change to using Unicode, the need
1165: for this locale support is expected to die away.
1166: </P>
1167: <P>
1168: External tables are built by calling the <b>pcre_maketables()</b> function,
1169: which has no arguments, in the relevant locale. The result can then be passed
1.1.1.5 ! misho 1170: to <b>pcre_compile()</b> as often as necessary. For example, to build and use
! 1171: tables that are appropriate for the French locale (where accented characters
! 1172: with values greater than 128 are treated as letters), the following code could
! 1173: be used:
1.1 misho 1174: <pre>
1175: setlocale(LC_CTYPE, "fr_FR");
1176: tables = pcre_maketables();
1177: re = pcre_compile(..., tables);
1178: </pre>
1179: The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
1180: are using Windows, the name for the French locale is "french".
1181: </P>
1182: <P>
1183: When <b>pcre_maketables()</b> runs, the tables are built in memory that is
1184: obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
1185: that the memory containing the tables remains available for as long as it is
1186: needed.
1187: </P>
1188: <P>
1189: The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
1190: pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
1.1.1.5 ! misho 1191: and also by <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>. Thus, for any single
1.1 misho 1192: pattern, compilation, studying and matching all happen in the same locale, but
1.1.1.5 ! misho 1193: different patterns can be processed in different locales.
1.1 misho 1194: </P>
1195: <P>
1196: It is possible to pass a table pointer or NULL (indicating the use of the
1.1.1.5 ! misho 1197: internal tables) to <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b> (see the
! 1198: discussion below in the section on matching a pattern). This facility is
! 1199: provided for use with pre-compiled patterns that have been saved and reloaded.
! 1200: Character tables are not saved with patterns, so if a non-standard table was
! 1201: used at compile time, it must be provided again when the reloaded pattern is
! 1202: matched. Attempting to use this facility to match a pattern in a different
! 1203: locale from the one in which it was compiled is likely to lead to anomalous
! 1204: (usually incorrect) results.
1.1 misho 1205: <a name="infoaboutpattern"></a></P>
1.1.1.2 misho 1206: <br><a name="SEC15" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
1.1 misho 1207: <P>
1208: <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1.1.1.5 ! misho 1209: <b> int <i>what</i>, void *<i>where</i>);</b>
1.1 misho 1210: </P>
1211: <P>
1212: The <b>pcre_fullinfo()</b> function returns information about a compiled
1.1.1.2 misho 1213: pattern. It replaces the <b>pcre_info()</b> function, which was removed from the
1214: library at version 8.30, after more than 10 years of obsolescence.
1.1 misho 1215: </P>
1216: <P>
1217: The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled
1218: pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if
1219: the pattern was not studied. The third argument specifies which piece of
1220: information is required, and the fourth argument is a pointer to a variable
1221: to receive the data. The yield of the function is zero for success, or one of
1222: the following negative numbers:
1223: <pre>
1.1.1.2 misho 1224: PCRE_ERROR_NULL the argument <i>code</i> was NULL
1225: the argument <i>where</i> was NULL
1226: PCRE_ERROR_BADMAGIC the "magic number" was not found
1227: PCRE_ERROR_BADENDIANNESS the pattern was compiled with different
1228: endianness
1229: PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid
1.1.1.4 misho 1230: PCRE_ERROR_UNSET the requested field is not set
1.1 misho 1231: </pre>
1232: The "magic number" is placed at the start of each compiled pattern as an simple
1.1.1.2 misho 1233: check against passing an arbitrary memory pointer. The endianness error can
1234: occur if a compiled pattern is saved and reloaded on a different host. Here is
1235: a typical call of <b>pcre_fullinfo()</b>, to obtain the length of the compiled
1236: pattern:
1.1 misho 1237: <pre>
1238: int rc;
1239: size_t length;
1240: rc = pcre_fullinfo(
1241: re, /* result of pcre_compile() */
1242: sd, /* result of pcre_study(), or NULL */
1243: PCRE_INFO_SIZE, /* what is required */
1244: &length); /* where to put the data */
1245: </pre>
1246: The possible values for the third argument are defined in <b>pcre.h</b>, and are
1247: as follows:
1248: <pre>
1249: PCRE_INFO_BACKREFMAX
1250: </pre>
1251: Return the number of the highest back reference in the pattern. The fourth
1252: argument should point to an <b>int</b> variable. Zero is returned if there are
1253: no back references.
1254: <pre>
1255: PCRE_INFO_CAPTURECOUNT
1256: </pre>
1257: Return the number of capturing subpatterns in the pattern. The fourth argument
1258: should point to an <b>int</b> variable.
1259: <pre>
1260: PCRE_INFO_DEFAULT_TABLES
1261: </pre>
1262: Return a pointer to the internal default character tables within PCRE. The
1263: fourth argument should point to an <b>unsigned char *</b> variable. This
1264: information call is provided for internal use by the <b>pcre_study()</b>
1265: function. External callers can cause PCRE to use its internal tables by passing
1266: a NULL table pointer.
1267: <pre>
1268: PCRE_INFO_FIRSTBYTE
1269: </pre>
1.1.1.2 misho 1270: Return information about the first data unit of any matched string, for a
1271: non-anchored pattern. (The name of this option refers to the 8-bit library,
1272: where data units are bytes.) The fourth argument should point to an <b>int</b>
1273: variable.
1274: </P>
1275: <P>
1276: If there is a fixed first value, for example, the letter "c" from a pattern
1277: such as (cat|cow|coyote), its value is returned. In the 8-bit library, the
1.1.1.4 misho 1278: value is always less than 256. In the 16-bit library the value can be up to
1279: 0xffff. In the 32-bit library the value can be up to 0x10ffff.
1.1 misho 1280: </P>
1281: <P>
1.1.1.2 misho 1282: If there is no fixed first value, and if either
1.1 misho 1283: <br>
1284: <br>
1285: (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1286: starts with "^", or
1287: <br>
1288: <br>
1289: (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1290: (if it were set, the pattern would be anchored),
1291: <br>
1292: <br>
1293: -1 is returned, indicating that the pattern matches only at the start of a
1294: subject string or after any newline within the string. Otherwise -2 is
1295: returned. For anchored patterns, -2 is returned.
1.1.1.4 misho 1296: </P>
1297: <P>
1298: Since for the 32-bit library using the non-UTF-32 mode, this function is unable
1299: to return the full 32-bit range of the character, this value is deprecated;
1300: instead the PCRE_INFO_FIRSTCHARACTERFLAGS and PCRE_INFO_FIRSTCHARACTER values
1301: should be used.
1.1 misho 1302: <pre>
1303: PCRE_INFO_FIRSTTABLE
1304: </pre>
1305: If the pattern was studied, and this resulted in the construction of a 256-bit
1.1.1.2 misho 1306: table indicating a fixed set of values for the first data unit in any matching
1.1 misho 1307: string, a pointer to the table is returned. Otherwise NULL is returned. The
1308: fourth argument should point to an <b>unsigned char *</b> variable.
1309: <pre>
1310: PCRE_INFO_HASCRORLF
1311: </pre>
1312: Return 1 if the pattern contains any explicit matches for CR or LF characters,
1313: otherwise 0. The fourth argument should point to an <b>int</b> variable. An
1314: explicit match is either a literal CR or LF character, or \r or \n.
1315: <pre>
1316: PCRE_INFO_JCHANGED
1317: </pre>
1318: Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1319: 0. The fourth argument should point to an <b>int</b> variable. (?J) and
1320: (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1321: <pre>
1322: PCRE_INFO_JIT
1323: </pre>
1.1.1.3 misho 1324: Return 1 if the pattern was studied with one of the JIT options, and
1.1 misho 1325: just-in-time compiling was successful. The fourth argument should point to an
1326: <b>int</b> variable. A return value of 0 means that JIT support is not available
1.1.1.3 misho 1327: in this version of PCRE, or that the pattern was not studied with a JIT option,
1328: or that the JIT compiler could not handle this particular pattern. See the
1.1 misho 1329: <a href="pcrejit.html"><b>pcrejit</b></a>
1330: documentation for details of what can and cannot be handled.
1331: <pre>
1332: PCRE_INFO_JITSIZE
1333: </pre>
1.1.1.3 misho 1334: If the pattern was successfully studied with a JIT option, return the size of
1335: the JIT compiled code, otherwise return zero. The fourth argument should point
1336: to a <b>size_t</b> variable.
1.1 misho 1337: <pre>
1338: PCRE_INFO_LASTLITERAL
1339: </pre>
1.1.1.2 misho 1340: Return the value of the rightmost literal data unit that must exist in any
1341: matched string, other than at its start, if such a value has been recorded. The
1342: fourth argument should point to an <b>int</b> variable. If there is no such
1343: value, -1 is returned. For anchored patterns, a last literal value is recorded
1344: only if it follows something of variable length. For example, for the pattern
1.1 misho 1345: /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
1346: is -1.
1.1.1.4 misho 1347: </P>
1348: <P>
1349: Since for the 32-bit library using the non-UTF-32 mode, this function is unable
1.1.1.5 ! misho 1350: to return the full 32-bit range of characters, this value is deprecated;
1.1.1.4 misho 1351: instead the PCRE_INFO_REQUIREDCHARFLAGS and PCRE_INFO_REQUIREDCHAR values should
1352: be used.
1353: <pre>
1.1.1.5 ! misho 1354: PCRE_INFO_MATCH_EMPTY
! 1355: </pre>
! 1356: Return 1 if the pattern can match an empty string, otherwise 0. The fourth
! 1357: argument should point to an <b>int</b> variable.
! 1358: <pre>
1.1.1.4 misho 1359: PCRE_INFO_MATCHLIMIT
1360: </pre>
1361: If the pattern set a match limit by including an item of the form
1362: (*LIMIT_MATCH=nnnn) at the start, the value is returned. The fourth argument
1363: should point to an unsigned 32-bit integer. If no such value has been set, the
1364: call to <b>pcre_fullinfo()</b> returns the error PCRE_ERROR_UNSET.
1.1 misho 1365: <pre>
1.1.1.3 misho 1366: PCRE_INFO_MAXLOOKBEHIND
1367: </pre>
1.1.1.4 misho 1368: Return the number of characters (NB not data units) in the longest lookbehind
1369: assertion in the pattern. This information is useful when doing multi-segment
1370: matching using the partial matching facilities. Note that the simple assertions
1371: \b and \B require a one-character lookbehind. \A also registers a
1372: one-character lookbehind, though it does not actually inspect the previous
1373: character. This is to ensure that at least one character from the old segment
1374: is retained when a new segment is processed. Otherwise, if there are no
1375: lookbehinds in the pattern, \A might match incorrectly at the start of a new
1376: segment.
1.1.1.3 misho 1377: <pre>
1.1 misho 1378: PCRE_INFO_MINLENGTH
1379: </pre>
1380: If the pattern was studied and a minimum length for matching subject strings
1381: was computed, its value is returned. Otherwise the returned value is -1. The
1.1.1.4 misho 1382: value is a number of characters, which in UTF mode may be different from the
1383: number of data units. The fourth argument should point to an <b>int</b>
1384: variable. A non-negative value is a lower bound to the length of any matching
1385: string. There may not be any strings of that length that do actually match, but
1386: every string that does match is at least that long.
1.1 misho 1387: <pre>
1388: PCRE_INFO_NAMECOUNT
1389: PCRE_INFO_NAMEENTRYSIZE
1390: PCRE_INFO_NAMETABLE
1391: </pre>
1392: PCRE supports the use of named as well as numbered capturing parentheses. The
1393: names are just an additional way of identifying the parentheses, which still
1394: acquire numbers. Several convenience functions such as
1395: <b>pcre_get_named_substring()</b> are provided for extracting captured
1396: substrings by name. It is also possible to extract the data directly, by first
1397: converting the name to a number in order to access the correct pointers in the
1398: output vector (described with <b>pcre_exec()</b> below). To do the conversion,
1399: you need to use the name-to-number map, which is described by these three
1400: values.
1401: </P>
1402: <P>
1403: The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1404: the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1405: entry; both of these return an <b>int</b> value. The entry size depends on the
1406: length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1.1.1.2 misho 1407: entry of the table. This is a pointer to <b>char</b> in the 8-bit library, where
1408: the first two bytes of each entry are the number of the capturing parenthesis,
1409: most significant byte first. In the 16-bit library, the pointer points to
1.1.1.4 misho 1410: 16-bit data units, the first of which contains the parenthesis number. In the
1411: 32-bit library, the pointer points to 32-bit data units, the first of which
1412: contains the parenthesis number. The rest of the entry is the corresponding
1413: name, zero terminated.
1.1 misho 1414: </P>
1415: <P>
1.1.1.5 ! misho 1416: The names are in alphabetical order. If (?| is used to create multiple groups
! 1417: with the same number, as described in the
1.1 misho 1418: <a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
1419: in the
1420: <a href="pcrepattern.html"><b>pcrepattern</b></a>
1.1.1.5 ! misho 1421: page, the groups may be given the same name, but there is only one entry in the
! 1422: table. Different names for groups of the same number are not permitted.
! 1423: Duplicate names for subpatterns with different numbers are permitted,
! 1424: but only if PCRE_DUPNAMES is set. They appear in the table in the order in
! 1425: which they were found in the pattern. In the absence of (?| this is the order
! 1426: of increasing number; when (?| is used this is not necessarily the case because
! 1427: later subpatterns may have lower numbers.
1.1 misho 1428: </P>
1429: <P>
1430: As a simple example of the name/number table, consider the following pattern
1.1.1.2 misho 1431: after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white
1432: space - including newlines - is ignored):
1.1 misho 1433: <pre>
1434: (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) )
1435: </pre>
1436: There are four named subpatterns, so the table has four entries, and each entry
1437: in the table is eight bytes long. The table is as follows, with non-printing
1438: bytes shows in hexadecimal, and undefined bytes shown as ??:
1439: <pre>
1440: 00 01 d a t e 00 ??
1441: 00 05 d a y 00 ?? ??
1442: 00 04 m o n t h 00
1443: 00 02 y e a r 00 ??
1444: </pre>
1445: When writing code to extract data from named subpatterns using the
1446: name-to-number map, remember that the length of the entries is likely to be
1447: different for each compiled pattern.
1448: <pre>
1449: PCRE_INFO_OKPARTIAL
1450: </pre>
1451: Return 1 if the pattern can be used for partial matching with
1452: <b>pcre_exec()</b>, otherwise 0. The fourth argument should point to an
1453: <b>int</b> variable. From release 8.00, this always returns 1, because the
1454: restrictions that previously applied to partial matching have been lifted. The
1455: <a href="pcrepartial.html"><b>pcrepartial</b></a>
1456: documentation gives details of partial matching.
1457: <pre>
1458: PCRE_INFO_OPTIONS
1459: </pre>
1460: Return a copy of the options with which the pattern was compiled. The fourth
1461: argument should point to an <b>unsigned long int</b> variable. These option bits
1462: are those specified in the call to <b>pcre_compile()</b>, modified by any
1463: top-level option settings at the start of the pattern itself. In other words,
1464: they are the options that will be in force when matching starts. For example,
1465: if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1466: result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1467: </P>
1468: <P>
1469: A pattern is automatically anchored by PCRE if all of its top-level
1470: alternatives begin with one of the following:
1471: <pre>
1472: ^ unless PCRE_MULTILINE is set
1473: \A always
1474: \G always
1475: .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
1476: </pre>
1477: For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1478: <b>pcre_fullinfo()</b>.
1479: <pre>
1.1.1.4 misho 1480: PCRE_INFO_RECURSIONLIMIT
1481: </pre>
1482: If the pattern set a recursion limit by including an item of the form
1483: (*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth
1484: argument should point to an unsigned 32-bit integer. If no such value has been
1485: set, the call to <b>pcre_fullinfo()</b> returns the error PCRE_ERROR_UNSET.
1486: <pre>
1.1 misho 1487: PCRE_INFO_SIZE
1488: </pre>
1.1.1.4 misho 1489: Return the size of the compiled pattern in bytes (for all three libraries). The
1.1.1.2 misho 1490: fourth argument should point to a <b>size_t</b> variable. This value does not
1491: include the size of the <b>pcre</b> structure that is returned by
1492: <b>pcre_compile()</b>. The value that is passed as the argument to
1493: <b>pcre_malloc()</b> when <b>pcre_compile()</b> is getting memory in which to
1494: place the compiled data is the value returned by this option plus the size of
1495: the <b>pcre</b> structure. Studying a compiled pattern, with or without JIT,
1496: does not alter the value returned by this option.
1.1 misho 1497: <pre>
1498: PCRE_INFO_STUDYSIZE
1499: </pre>
1.1.1.4 misho 1500: Return the size in bytes (for all three libraries) of the data block pointed to
1501: by the <i>study_data</i> field in a <b>pcre_extra</b> block. If <b>pcre_extra</b>
1502: is NULL, or there is no study data, zero is returned. The fourth argument
1503: should point to a <b>size_t</b> variable. The <i>study_data</i> field is set by
1504: <b>pcre_study()</b> to record information that will speed up matching (see the
1505: section entitled
1.1 misho 1506: <a href="#studyingapattern">"Studying a pattern"</a>
1507: above). The format of the <i>study_data</i> block is private, but its length
1508: is made available via this option so that it can be saved and restored (see the
1509: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1510: documentation for details).
1.1.1.4 misho 1511: <pre>
1512: PCRE_INFO_FIRSTCHARACTERFLAGS
1513: </pre>
1514: Return information about the first data unit of any matched string, for a
1515: non-anchored pattern. The fourth argument should point to an <b>int</b>
1516: variable.
1517: </P>
1518: <P>
1519: If there is a fixed first value, for example, the letter "c" from a pattern
1520: such as (cat|cow|coyote), 1 is returned, and the character value can be
1521: retrieved using PCRE_INFO_FIRSTCHARACTER.
1522: </P>
1523: <P>
1524: If there is no fixed first value, and if either
1525: <br>
1526: <br>
1527: (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1528: starts with "^", or
1529: <br>
1530: <br>
1531: (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1532: (if it were set, the pattern would be anchored),
1533: <br>
1534: <br>
1535: 2 is returned, indicating that the pattern matches only at the start of a
1536: subject string or after any newline within the string. Otherwise 0 is
1537: returned. For anchored patterns, 0 is returned.
1538: <pre>
1539: PCRE_INFO_FIRSTCHARACTER
1540: </pre>
1.1.1.5 ! misho 1541: Return the fixed first character value in the situation where
! 1542: PCRE_INFO_FIRSTCHARACTERFLAGS returns 1; otherwise return 0. The fourth
! 1543: argument should point to an <b>uint_t</b> variable.
1.1.1.4 misho 1544: </P>
1545: <P>
1546: In the 8-bit library, the value is always less than 256. In the 16-bit library
1547: the value can be up to 0xffff. In the 32-bit library in UTF-32 mode the value
1548: can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32 mode.
1549: <pre>
1550: PCRE_INFO_REQUIREDCHARFLAGS
1551: </pre>
1552: Returns 1 if there is a rightmost literal data unit that must exist in any
1553: matched string, other than at its start. The fourth argument should point to
1554: an <b>int</b> variable. If there is no such value, 0 is returned. If returning
1555: 1, the character value itself can be retrieved using PCRE_INFO_REQUIREDCHAR.
1556: </P>
1557: <P>
1558: For anchored patterns, a last literal value is recorded only if it follows
1559: something of variable length. For example, for the pattern /^a\d+z\d+/ the
1560: returned value 1 (with "z" returned from PCRE_INFO_REQUIREDCHAR), but for
1561: /^a\dz\d/ the returned value is 0.
1562: <pre>
1563: PCRE_INFO_REQUIREDCHAR
1564: </pre>
1565: Return the value of the rightmost literal data unit that must exist in any
1566: matched string, other than at its start, if such a value has been recorded. The
1567: fourth argument should point to an <b>uint32_t</b> variable. If there is no such
1568: value, 0 is returned.
1.1 misho 1569: </P>
1.1.1.2 misho 1570: <br><a name="SEC16" href="#TOC1">REFERENCE COUNTS</a><br>
1.1 misho 1571: <P>
1572: <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
1573: </P>
1574: <P>
1575: The <b>pcre_refcount()</b> function is used to maintain a reference count in the
1576: data block that contains a compiled pattern. It is provided for the benefit of
1577: applications that operate in an object-oriented manner, where different parts
1578: of the application may be using the same compiled pattern, but you want to free
1579: the block when they are all done.
1580: </P>
1581: <P>
1582: When a pattern is compiled, the reference count field is initialized to zero.
1583: It is changed only by calling this function, whose action is to add the
1584: <i>adjust</i> value (which may be positive or negative) to it. The yield of the
1585: function is the new value. However, the value of the count is constrained to
1586: lie between 0 and 65535, inclusive. If the new value is outside these limits,
1587: it is forced to the appropriate limit value.
1588: </P>
1589: <P>
1590: Except when it is zero, the reference count is not correctly preserved if a
1591: pattern is compiled on one host and then transferred to a host whose byte-order
1592: is different. (This seems a highly unlikely scenario.)
1593: </P>
1.1.1.2 misho 1594: <br><a name="SEC17" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
1.1 misho 1595: <P>
1596: <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1.1.1.5 ! misho 1597: <b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
! 1598: <b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
1.1 misho 1599: </P>
1600: <P>
1601: The function <b>pcre_exec()</b> is called to match a subject string against a
1602: compiled pattern, which is passed in the <i>code</i> argument. If the
1603: pattern was studied, the result of the study should be passed in the
1604: <i>extra</i> argument. You can call <b>pcre_exec()</b> with the same <i>code</i>
1605: and <i>extra</i> arguments as many times as you like, in order to match
1606: different subject strings with the same pattern.
1607: </P>
1608: <P>
1609: This function is the main matching facility of the library, and it operates in
1610: a Perl-like manner. For specialist use there is also an alternative matching
1611: function, which is described
1612: <a href="#dfamatch">below</a>
1613: in the section about the <b>pcre_dfa_exec()</b> function.
1614: </P>
1615: <P>
1616: In most applications, the pattern will have been compiled (and optionally
1617: studied) in the same process that calls <b>pcre_exec()</b>. However, it is
1618: possible to save compiled patterns and study data, and then use them later
1619: in different processes, possibly even on different hosts. For a discussion
1620: about this, see the
1621: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1622: documentation.
1623: </P>
1624: <P>
1625: Here is an example of a simple call to <b>pcre_exec()</b>:
1626: <pre>
1627: int rc;
1628: int ovector[30];
1629: rc = pcre_exec(
1630: re, /* result of pcre_compile() */
1631: NULL, /* we didn't study the pattern */
1632: "some string", /* the subject string */
1633: 11, /* the length of the subject string */
1634: 0, /* start at offset 0 in the subject */
1635: 0, /* default options */
1636: ovector, /* vector of integers for substring information */
1637: 30); /* number of elements (NOT size in bytes) */
1638: <a name="extradata"></a></PRE>
1639: </P>
1640: <br><b>
1641: Extra data for <b>pcre_exec()</b>
1642: </b><br>
1643: <P>
1644: If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
1645: data block. The <b>pcre_study()</b> function returns such a block (when it
1646: doesn't return NULL), but you can also create one for yourself, and pass
1647: additional information in it. The <b>pcre_extra</b> block contains the following
1648: fields (not necessarily in this order):
1649: <pre>
1650: unsigned long int <i>flags</i>;
1651: void *<i>study_data</i>;
1652: void *<i>executable_jit</i>;
1653: unsigned long int <i>match_limit</i>;
1654: unsigned long int <i>match_limit_recursion</i>;
1655: void *<i>callout_data</i>;
1656: const unsigned char *<i>tables</i>;
1657: unsigned char **<i>mark</i>;
1658: </pre>
1.1.1.2 misho 1659: In the 16-bit version of this structure, the <i>mark</i> field has type
1660: "PCRE_UCHAR16 **".
1.1.1.4 misho 1661: <br>
1662: <br>
1663: In the 32-bit version of this structure, the <i>mark</i> field has type
1664: "PCRE_UCHAR32 **".
1.1.1.2 misho 1665: </P>
1666: <P>
1.1.1.3 misho 1667: The <i>flags</i> field is used to specify which of the other fields are set. The
1668: flag bits are:
1.1 misho 1669: <pre>
1.1.1.3 misho 1670: PCRE_EXTRA_CALLOUT_DATA
1.1 misho 1671: PCRE_EXTRA_EXECUTABLE_JIT
1.1.1.3 misho 1672: PCRE_EXTRA_MARK
1.1 misho 1673: PCRE_EXTRA_MATCH_LIMIT
1674: PCRE_EXTRA_MATCH_LIMIT_RECURSION
1.1.1.3 misho 1675: PCRE_EXTRA_STUDY_DATA
1.1 misho 1676: PCRE_EXTRA_TABLES
1677: </pre>
1678: Other flag bits should be set to zero. The <i>study_data</i> field and sometimes
1679: the <i>executable_jit</i> field are set in the <b>pcre_extra</b> block that is
1680: returned by <b>pcre_study()</b>, together with the appropriate flag bits. You
1.1.1.3 misho 1681: should not set these yourself, but you may add to the block by setting other
1682: fields and their corresponding flag bits.
1.1 misho 1683: </P>
1684: <P>
1685: The <i>match_limit</i> field provides a means of preventing PCRE from using up a
1686: vast amount of resources when running patterns that are not going to match,
1687: but which have a very large number of possibilities in their search trees. The
1688: classic example is a pattern that uses nested unlimited repeats.
1689: </P>
1690: <P>
1691: Internally, <b>pcre_exec()</b> uses a function called <b>match()</b>, which it
1692: calls repeatedly (sometimes recursively). The limit set by <i>match_limit</i> is
1693: imposed on the number of times this function is called during a match, which
1694: has the effect of limiting the amount of backtracking that can take place. For
1695: patterns that are not anchored, the count restarts from zero for each position
1696: in the subject string.
1697: </P>
1698: <P>
1699: When <b>pcre_exec()</b> is called with a pattern that was successfully studied
1.1.1.3 misho 1700: with a JIT option, the way that the matching is executed is entirely different.
1701: However, there is still the possibility of runaway matching that goes on for a
1702: very long time, and so the <i>match_limit</i> value is also used in this case
1703: (but in a different way) to limit how long the matching can continue.
1.1 misho 1704: </P>
1705: <P>
1706: The default value for the limit can be set when PCRE is built; the default
1707: default is 10 million, which handles all but the most extreme cases. You can
1708: override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b>
1709: block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1710: the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns
1711: PCRE_ERROR_MATCHLIMIT.
1712: </P>
1713: <P>
1.1.1.4 misho 1714: A value for the match limit may also be supplied by an item at the start of a
1715: pattern of the form
1716: <pre>
1717: (*LIMIT_MATCH=d)
1718: </pre>
1719: where d is a decimal number. However, such a setting is ignored unless d is
1720: less than the limit set by the caller of <b>pcre_exec()</b> or, if no such limit
1721: is set, less than the default.
1722: </P>
1723: <P>
1.1 misho 1724: The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but
1725: instead of limiting the total number of times that <b>match()</b> is called, it
1726: limits the depth of recursion. The recursion depth is a smaller number than the
1727: total number of calls, because not all calls to <b>match()</b> are recursive.
1728: This limit is of use only if it is set smaller than <i>match_limit</i>.
1729: </P>
1730: <P>
1731: Limiting the recursion depth limits the amount of machine stack that can be
1732: used, or, when PCRE has been compiled to use memory on the heap instead of the
1733: stack, the amount of heap memory that can be used. This limit is not relevant,
1.1.1.3 misho 1734: and is ignored, when matching is done using JIT compiled code.
1.1 misho 1735: </P>
1736: <P>
1737: The default value for <i>match_limit_recursion</i> can be set when PCRE is
1738: built; the default default is the same value as the default for
1739: <i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b>
1740: with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and
1741: PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit
1742: is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT.
1743: </P>
1744: <P>
1.1.1.4 misho 1745: A value for the recursion limit may also be supplied by an item at the start of
1746: a pattern of the form
1747: <pre>
1748: (*LIMIT_RECURSION=d)
1749: </pre>
1750: where d is a decimal number. However, such a setting is ignored unless d is
1751: less than the limit set by the caller of <b>pcre_exec()</b> or, if no such limit
1752: is set, less than the default.
1753: </P>
1754: <P>
1.1 misho 1755: The <i>callout_data</i> field is used in conjunction with the "callout" feature,
1756: and is described in the
1757: <a href="pcrecallout.html"><b>pcrecallout</b></a>
1758: documentation.
1759: </P>
1760: <P>
1.1.1.5 ! misho 1761: The <i>tables</i> field is provided for use with patterns that have been
! 1762: pre-compiled using custom character tables, saved to disc or elsewhere, and
! 1763: then reloaded, because the tables that were used to compile a pattern are not
! 1764: saved with it. See the
1.1 misho 1765: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1.1.1.5 ! misho 1766: documentation for a discussion of saving compiled patterns for later use. If
! 1767: NULL is passed using this mechanism, it forces PCRE's internal tables to be
! 1768: used.
! 1769: </P>
! 1770: <P>
! 1771: <b>Warning:</b> The tables that <b>pcre_exec()</b> uses must be the same as those
! 1772: that were used when the pattern was compiled. If this is not the case, the
! 1773: behaviour of <b>pcre_exec()</b> is undefined. Therefore, when a pattern is
! 1774: compiled and matched in the same process, this field should never be set. In
! 1775: this (the most common) case, the correct table pointer is automatically passed
! 1776: with the compiled pattern from <b>pcre_compile()</b> to <b>pcre_exec()</b>.
1.1 misho 1777: </P>
1778: <P>
1779: If PCRE_EXTRA_MARK is set in the <i>flags</i> field, the <i>mark</i> field must
1.1.1.2 misho 1780: be set to point to a suitable variable. If the pattern contains any
1.1 misho 1781: backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1782: a name to pass back, a pointer to the name string (zero terminated) is placed
1783: in the variable pointed to by the <i>mark</i> field. The names are within the
1784: compiled pattern; if you wish to retain such a name you must copy it before
1785: freeing the memory of a compiled pattern. If there is no name to pass back, the
1.1.1.2 misho 1786: variable pointed to by the <i>mark</i> field is set to NULL. For details of the
1.1 misho 1787: backtracking control verbs, see the section entitled
1788: <a href="pcrepattern#backtrackcontrol">"Backtracking control"</a>
1789: in the
1790: <a href="pcrepattern.html"><b>pcrepattern</b></a>
1791: documentation.
1792: <a name="execoptions"></a></P>
1793: <br><b>
1794: Option bits for <b>pcre_exec()</b>
1795: </b><br>
1796: <P>
1797: The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
1798: zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1799: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1.1.1.3 misho 1800: PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and
1801: PCRE_PARTIAL_SOFT.
1.1 misho 1802: </P>
1803: <P>
1.1.1.3 misho 1804: If the pattern was successfully studied with one of the just-in-time (JIT)
1805: compile options, the only supported options for JIT execution are
1806: PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,
1807: PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an
1808: unsupported option is used, JIT execution is disabled and the normal
1809: interpretive code in <b>pcre_exec()</b> is run.
1.1 misho 1810: <pre>
1811: PCRE_ANCHORED
1812: </pre>
1813: The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
1814: matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1815: to be anchored by virtue of its contents, it cannot be made unachored at
1816: matching time.
1817: <pre>
1818: PCRE_BSR_ANYCRLF
1819: PCRE_BSR_UNICODE
1820: </pre>
1821: These options (which are mutually exclusive) control what the \R escape
1822: sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1823: match any Unicode newline sequence. These options override the choice that was
1824: made or defaulted when the pattern was compiled.
1825: <pre>
1826: PCRE_NEWLINE_CR
1827: PCRE_NEWLINE_LF
1828: PCRE_NEWLINE_CRLF
1829: PCRE_NEWLINE_ANYCRLF
1830: PCRE_NEWLINE_ANY
1831: </pre>
1832: These options override the newline definition that was chosen or defaulted when
1833: the pattern was compiled. For details, see the description of
1834: <b>pcre_compile()</b> above. During matching, the newline choice affects the
1835: behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1836: the way the match position is advanced after a match failure for an unanchored
1837: pattern.
1838: </P>
1839: <P>
1840: When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1841: match attempt for an unanchored pattern fails when the current position is at a
1842: CRLF sequence, and the pattern contains no explicit matches for CR or LF
1843: characters, the match position is advanced by two characters instead of one, in
1844: other words, to after the CRLF.
1845: </P>
1846: <P>
1847: The above rule is a compromise that makes the most common cases work as
1848: expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1849: set), it does not match the string "\r\nA" because, after failing at the
1850: start, it skips both the CR and the LF before retrying. However, the pattern
1851: [\r\n]A does match that string, because it contains an explicit CR or LF
1852: reference, and so advances only by one character after the first failure.
1853: </P>
1854: <P>
1855: An explicit match for CR of LF is either a literal appearance of one of those
1856: characters, or one of the \r or \n escape sequences. Implicit matches such as
1857: [^X] do not count, nor does \s (which includes CR and LF in the characters
1858: that it matches).
1859: </P>
1860: <P>
1861: Notwithstanding the above, anomalous effects may still occur when CRLF is a
1862: valid newline sequence and explicit \r or \n escapes appear in the pattern.
1863: <pre>
1864: PCRE_NOTBOL
1865: </pre>
1866: This option specifies that first character of the subject string is not the
1867: beginning of a line, so the circumflex metacharacter should not match before
1868: it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1869: never to match. This option affects only the behaviour of the circumflex
1870: metacharacter. It does not affect \A.
1871: <pre>
1872: PCRE_NOTEOL
1873: </pre>
1874: This option specifies that the end of the subject string is not the end of a
1875: line, so the dollar metacharacter should not match it nor (except in multiline
1876: mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1877: compile time) causes dollar never to match. This option affects only the
1878: behaviour of the dollar metacharacter. It does not affect \Z or \z.
1879: <pre>
1880: PCRE_NOTEMPTY
1881: </pre>
1882: An empty string is not considered to be a valid match if this option is set. If
1883: there are alternatives in the pattern, they are tried. If all the alternatives
1884: match the empty string, the entire match fails. For example, if the pattern
1885: <pre>
1886: a?b?
1887: </pre>
1888: is applied to a string not beginning with "a" or "b", it matches an empty
1889: string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1890: valid, so PCRE searches further into the string for occurrences of "a" or "b".
1891: <pre>
1892: PCRE_NOTEMPTY_ATSTART
1893: </pre>
1894: This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1895: the start of the subject is permitted. If the pattern is anchored, such a match
1896: can occur only if the pattern contains \K.
1897: </P>
1898: <P>
1899: Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1900: does make a special case of a pattern match of the empty string within its
1901: <b>split()</b> function, and when using the /g modifier. It is possible to
1902: emulate Perl's behaviour after matching a null string by first trying the match
1903: again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1904: if that fails, by advancing the starting offset (see below) and trying an
1905: ordinary match again. There is some code that demonstrates how to do this in
1906: the
1907: <a href="pcredemo.html"><b>pcredemo</b></a>
1908: sample program. In the most general case, you have to check to see if the
1909: newline convention recognizes CRLF as a newline, and if so, and the current
1910: character is CR followed by LF, advance the starting offset by two characters
1911: instead of one.
1912: <pre>
1913: PCRE_NO_START_OPTIMIZE
1914: </pre>
1915: There are a number of optimizations that <b>pcre_exec()</b> uses at the start of
1916: a match, in order to speed up the process. For example, if it is known that an
1917: unanchored match must start with a specific character, it searches the subject
1918: for that character, and fails immediately if it cannot find it, without
1919: actually running the main matching function. This means that a special item
1920: such as (*COMMIT) at the start of a pattern is not considered until after a
1.1.1.4 misho 1921: suitable starting point for the match has been found. Also, when callouts or
1922: (*MARK) items are in use, these "start-up" optimizations can cause them to be
1923: skipped if the pattern is never actually used. The start-up optimizations are
1924: in effect a pre-scan of the subject that takes place before the pattern is run.
1.1 misho 1925: </P>
1926: <P>
1927: The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1928: causing performance to suffer, but ensuring that in cases where the result is
1929: "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1930: are considered at every possible starting position in the subject string. If
1931: PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1.1.1.4 misho 1932: time. The use of PCRE_NO_START_OPTIMIZE at matching time (that is, passing it
1933: to <b>pcre_exec()</b>) disables JIT execution; in this situation, matching is
1934: always done using interpretively.
1.1 misho 1935: </P>
1936: <P>
1937: Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1938: Consider the pattern
1939: <pre>
1940: (*COMMIT)ABC
1941: </pre>
1942: When this is compiled, PCRE records the fact that a match must start with the
1943: character "A". Suppose the subject string is "DEFABC". The start-up
1944: optimization scans along the subject, finds "A" and runs the first match
1945: attempt from there. The (*COMMIT) item means that the pattern must match the
1946: current starting position, which in this case, it does. However, if the same
1947: match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1948: subject string does not happen. The first match attempt is run starting from
1949: "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1950: the overall result is "no match". If the pattern is studied, more start-up
1951: optimizations may be used. For example, a minimum length for the subject may be
1952: recorded. Consider the pattern
1953: <pre>
1954: (*MARK:A)(X|Y)
1955: </pre>
1956: The minimum length for a match is one character. If the subject is "ABC", there
1957: will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1958: If the pattern is studied, the final attempt does not take place, because PCRE
1959: knows that the subject is too short, and so the (*MARK) is never encountered.
1960: In this case, studying the pattern does not affect the overall match result,
1961: which is still "no match", but it does affect the auxiliary information that is
1962: returned.
1963: <pre>
1964: PCRE_NO_UTF8_CHECK
1965: </pre>
1966: When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1967: string is automatically checked when <b>pcre_exec()</b> is subsequently called.
1.1.1.3 misho 1968: The entire string is checked before any other processing takes place. The value
1969: of <i>startoffset</i> is also checked to ensure that it points to the start of a
1970: UTF-8 character. There is a discussion about the
1971: <a href="pcreunicode.html#utf8strings">validity of UTF-8 strings</a>
1972: in the
1.1.1.2 misho 1973: <a href="pcreunicode.html"><b>pcreunicode</b></a>
1974: page. If an invalid sequence of bytes is found, <b>pcre_exec()</b> returns the
1975: error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
1976: truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both
1977: cases, information about the precise nature of the error may also be returned
1978: (see the descriptions of these errors in the section entitled \fIError return
1979: values from\fP <b>pcre_exec()</b>
1.1 misho 1980: <a href="#errorlist">below).</a>
1981: If <i>startoffset</i> contains a value that does not point to the start of a
1982: UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1983: returned.
1984: </P>
1985: <P>
1986: If you already know that your subject is valid, and you want to skip these
1987: checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1988: calling <b>pcre_exec()</b>. You might want to do this for the second and
1989: subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find
1990: all the matches in a single subject string. However, you should be sure that
1.1.1.2 misho 1991: the value of <i>startoffset</i> points to the start of a character (or the end
1992: of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1993: invalid string as a subject or an invalid value of <i>startoffset</i> is
1.1.1.5 ! misho 1994: undefined. Your program may crash or loop.
1.1 misho 1995: <pre>
1996: PCRE_PARTIAL_HARD
1997: PCRE_PARTIAL_SOFT
1998: </pre>
1999: These options turn on the partial matching feature. For backwards
2000: compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
2001: occurs if the end of the subject string is reached successfully, but there are
2002: not enough subject characters to complete the match. If this happens when
2003: PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
2004: testing any remaining alternatives. Only if no complete match can be found is
2005: PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
2006: PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
2007: but only if no complete match can be found.
2008: </P>
2009: <P>
2010: If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
2011: partial match is found, <b>pcre_exec()</b> immediately returns
2012: PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
2013: when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
2014: important that an alternative complete match.
2015: </P>
2016: <P>
2017: In both cases, the portion of the string that was inspected when the partial
2018: match was found is set as the first matching string. There is a more detailed
2019: discussion of partial and multi-segment matching, with examples, in the
2020: <a href="pcrepartial.html"><b>pcrepartial</b></a>
2021: documentation.
2022: </P>
2023: <br><b>
2024: The string to be matched by <b>pcre_exec()</b>
2025: </b><br>
2026: <P>
2027: The subject string is passed to <b>pcre_exec()</b> as a pointer in
1.1.1.4 misho 2028: <i>subject</i>, a length in <i>length</i>, and a starting offset in
2029: <i>startoffset</i>. The units for <i>length</i> and <i>startoffset</i> are bytes
2030: for the 8-bit library, 16-bit data items for the 16-bit library, and 32-bit
2031: data items for the 32-bit library.
2032: </P>
2033: <P>
2034: If <i>startoffset</i> is negative or greater than the length of the subject,
2035: <b>pcre_exec()</b> returns PCRE_ERROR_BADOFFSET. When the starting offset is
2036: zero, the search for a match starts at the beginning of the subject, and this
2037: is by far the most common case. In UTF-8 or UTF-16 mode, the offset must point
2038: to the start of a character, or the end of the subject (in UTF-32 mode, one
2039: data unit equals one character, so all offsets are valid). Unlike the pattern
2040: string, the subject may contain binary zeroes.
1.1 misho 2041: </P>
2042: <P>
2043: A non-zero starting offset is useful when searching for another match in the
2044: same subject by calling <b>pcre_exec()</b> again after a previous success.
2045: Setting <i>startoffset</i> differs from just passing over a shortened string and
2046: setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
2047: lookbehind. For example, consider the pattern
2048: <pre>
2049: \Biss\B
2050: </pre>
2051: which finds occurrences of "iss" in the middle of words. (\B matches only if
2052: the current position in the subject is not a word boundary.) When applied to
2053: the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
2054: occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the
2055: subject, namely "issipi", it does not match, because \B is always false at the
2056: start of the subject, which is deemed to be a word boundary. However, if
2057: <b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i>
2058: set to 4, it finds the second occurrence of "iss" because it is able to look
2059: behind the starting point to discover that it is preceded by a letter.
2060: </P>
2061: <P>
2062: Finding all the matches in a subject is tricky when the pattern can match an
2063: empty string. It is possible to emulate Perl's /g behaviour by first trying the
2064: match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
2065: PCRE_ANCHORED options, and then if that fails, advancing the starting offset
2066: and trying an ordinary match again. There is some code that demonstrates how to
2067: do this in the
2068: <a href="pcredemo.html"><b>pcredemo</b></a>
2069: sample program. In the most general case, you have to check to see if the
2070: newline convention recognizes CRLF as a newline, and if so, and the current
2071: character is CR followed by LF, advance the starting offset by two characters
2072: instead of one.
2073: </P>
2074: <P>
2075: If a non-zero starting offset is passed when the pattern is anchored, one
2076: attempt to match at the given offset is made. This can only succeed if the
2077: pattern does not require the match to be at the start of the subject.
2078: </P>
2079: <br><b>
2080: How <b>pcre_exec()</b> returns captured substrings
2081: </b><br>
2082: <P>
2083: In general, a pattern matches a certain portion of the subject, and in
2084: addition, further substrings from the subject may be picked out by parts of the
2085: pattern. Following the usage in Jeffrey Friedl's book, this is called
2086: "capturing" in what follows, and the phrase "capturing subpattern" is used for
2087: a fragment of a pattern that picks out a substring. PCRE supports several other
2088: kinds of parenthesized subpattern that do not cause substrings to be captured.
2089: </P>
2090: <P>
2091: Captured substrings are returned to the caller via a vector of integers whose
2092: address is passed in <i>ovector</i>. The number of elements in the vector is
2093: passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>: this
2094: argument is NOT the size of <i>ovector</i> in bytes.
2095: </P>
2096: <P>
2097: The first two-thirds of the vector is used to pass back captured substrings,
2098: each substring using a pair of integers. The remaining third of the vector is
2099: used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
2100: and is not available for passing back information. The number passed in
2101: <i>ovecsize</i> should always be a multiple of three. If it is not, it is
2102: rounded down.
2103: </P>
2104: <P>
2105: When a match is successful, information about captured substrings is returned
2106: in pairs of integers, starting at the beginning of <i>ovector</i>, and
2107: continuing up to two-thirds of its length at the most. The first element of
1.1.1.4 misho 2108: each pair is set to the offset of the first character in a substring, and the
2109: second is set to the offset of the first character after the end of a
2110: substring. These values are always data unit offsets, even in UTF mode. They
2111: are byte offsets in the 8-bit library, 16-bit data item offsets in the 16-bit
2112: library, and 32-bit data item offsets in the 32-bit library. <b>Note</b>: they
2113: are not character counts.
1.1 misho 2114: </P>
2115: <P>
2116: The first pair of integers, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the
2117: portion of the subject string matched by the entire pattern. The next pair is
2118: used for the first capturing subpattern, and so on. The value returned by
2119: <b>pcre_exec()</b> is one more than the highest numbered pair that has been set.
2120: For example, if two substrings have been captured, the returned value is 3. If
2121: there are no capturing subpatterns, the return value from a successful match is
2122: 1, indicating that just the first pair of offsets has been set.
2123: </P>
2124: <P>
2125: If a capturing subpattern is matched repeatedly, it is the last portion of the
2126: string that it matched that is returned.
2127: </P>
2128: <P>
2129: If the vector is too small to hold all the captured substring offsets, it is
2130: used as far as possible (up to two-thirds of its length), and the function
1.1.1.3 misho 2131: returns a value of zero. If neither the actual string matched nor any captured
1.1 misho 2132: substrings are of interest, <b>pcre_exec()</b> may be called with <i>ovector</i>
2133: passed as NULL and <i>ovecsize</i> as zero. However, if the pattern contains
2134: back references and the <i>ovector</i> is not big enough to remember the related
2135: substrings, PCRE has to get additional memory for use during matching. Thus it
2136: is usually advisable to supply an <i>ovector</i> of reasonable size.
2137: </P>
2138: <P>
2139: There are some cases where zero is returned (indicating vector overflow) when
2140: in fact the vector is exactly the right size for the final match. For example,
2141: consider the pattern
2142: <pre>
2143: (a)(?:(b)c|bd)
2144: </pre>
2145: If a vector of 6 elements (allowing for only 1 captured substring) is given
2146: with subject string "abd", <b>pcre_exec()</b> will try to set the second
2147: captured string, thereby recording a vector overflow, before failing to match
2148: "c" and backing up to try the second alternative. The zero return, however,
2149: does correctly indicate that the maximum number of slots (namely 2) have been
2150: filled. In similar cases where there is temporary overflow, but the final
2151: number of used slots is actually less than the maximum, a non-zero value is
2152: returned.
2153: </P>
2154: <P>
2155: The <b>pcre_fullinfo()</b> function can be used to find out how many capturing
2156: subpatterns there are in a compiled pattern. The smallest size for
2157: <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
2158: the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
2159: </P>
2160: <P>
2161: It is possible for capturing subpattern number <i>n+1</i> to match some part of
2162: the subject when subpattern <i>n</i> has not been used at all. For example, if
2163: the string "abc" is matched against the pattern (a|(z))(bc) the return from the
2164: function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
2165: happens, both values in the offset pairs corresponding to unused subpatterns
2166: are set to -1.
2167: </P>
2168: <P>
2169: Offset values that correspond to unused subpatterns at the end of the
2170: expression are also set to -1. For example, if the string "abc" is matched
2171: against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
2172: return from the function is 2, because the highest used capturing subpattern
2173: number is 1, and the offsets for for the second and third capturing subpatterns
2174: (assuming the vector is large enough, of course) are set to -1.
2175: </P>
2176: <P>
2177: <b>Note</b>: Elements in the first two-thirds of <i>ovector</i> that do not
2178: correspond to capturing parentheses in the pattern are never changed. That is,
2179: if a pattern contains <i>n</i> capturing parentheses, no more than
2180: <i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by <b>pcre_exec()</b>. The other
2181: elements (in the first two-thirds) retain whatever values they previously had.
2182: </P>
2183: <P>
2184: Some convenience functions are provided for extracting the captured substrings
2185: as separate strings. These are described below.
2186: <a name="errorlist"></a></P>
2187: <br><b>
2188: Error return values from <b>pcre_exec()</b>
2189: </b><br>
2190: <P>
2191: If <b>pcre_exec()</b> fails, it returns a negative number. The following are
2192: defined in the header file:
2193: <pre>
2194: PCRE_ERROR_NOMATCH (-1)
2195: </pre>
2196: The subject string did not match the pattern.
2197: <pre>
2198: PCRE_ERROR_NULL (-2)
2199: </pre>
2200: Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
2201: NULL and <i>ovecsize</i> was not zero.
2202: <pre>
2203: PCRE_ERROR_BADOPTION (-3)
2204: </pre>
2205: An unrecognized bit was set in the <i>options</i> argument.
2206: <pre>
2207: PCRE_ERROR_BADMAGIC (-4)
2208: </pre>
2209: PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
2210: the case when it is passed a junk pointer and to detect when a pattern that was
2211: compiled in an environment of one endianness is run in an environment with the
2212: other endianness. This is the error that PCRE gives when the magic number is
2213: not present.
2214: <pre>
2215: PCRE_ERROR_UNKNOWN_OPCODE (-5)
2216: </pre>
2217: While running the pattern match, an unknown item was encountered in the
2218: compiled pattern. This error could be caused by a bug in PCRE or by overwriting
2219: of the compiled pattern.
2220: <pre>
2221: PCRE_ERROR_NOMEMORY (-6)
2222: </pre>
2223: If a pattern contains back references, but the <i>ovector</i> that is passed to
2224: <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
2225: gets a block of memory at the start of matching to use for this purpose. If the
2226: call via <b>pcre_malloc()</b> fails, this error is given. The memory is
2227: automatically freed at the end of matching.
2228: </P>
2229: <P>
2230: This error is also given if <b>pcre_stack_malloc()</b> fails in
2231: <b>pcre_exec()</b>. This can happen only when PCRE has been compiled with
2232: <b>--disable-stack-for-recursion</b>.
2233: <pre>
2234: PCRE_ERROR_NOSUBSTRING (-7)
2235: </pre>
2236: This error is used by the <b>pcre_copy_substring()</b>,
2237: <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
2238: below). It is never returned by <b>pcre_exec()</b>.
2239: <pre>
2240: PCRE_ERROR_MATCHLIMIT (-8)
2241: </pre>
2242: The backtracking limit, as specified by the <i>match_limit</i> field in a
2243: <b>pcre_extra</b> structure (or defaulted) was reached. See the description
2244: above.
2245: <pre>
2246: PCRE_ERROR_CALLOUT (-9)
2247: </pre>
2248: This error is never generated by <b>pcre_exec()</b> itself. It is provided for
2249: use by callout functions that want to yield a distinctive error code. See the
2250: <a href="pcrecallout.html"><b>pcrecallout</b></a>
2251: documentation for details.
2252: <pre>
2253: PCRE_ERROR_BADUTF8 (-10)
2254: </pre>
2255: A string that contains an invalid UTF-8 byte sequence was passed as a subject,
2256: and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
2257: (<i>ovecsize</i>) is at least 2, the byte offset to the start of the the invalid
2258: UTF-8 character is placed in the first element, and a reason code is placed in
2259: the second element. The reason codes are listed in the
2260: <a href="#badutf8reasons">following section.</a>
2261: For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
2262: truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
2263: PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2264: <pre>
2265: PCRE_ERROR_BADUTF8_OFFSET (-11)
2266: </pre>
2267: The UTF-8 byte sequence that was passed as a subject was checked and found to
2268: be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
2269: <i>startoffset</i> did not point to the beginning of a UTF-8 character or the
2270: end of the subject.
2271: <pre>
2272: PCRE_ERROR_PARTIAL (-12)
2273: </pre>
2274: The subject string did not match, but it did match partially. See the
2275: <a href="pcrepartial.html"><b>pcrepartial</b></a>
2276: documentation for details of partial matching.
2277: <pre>
2278: PCRE_ERROR_BADPARTIAL (-13)
2279: </pre>
2280: This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
2281: option was used with a compiled pattern containing items that were not
2282: supported for partial matching. From release 8.00 onwards, there are no
2283: restrictions on partial matching.
2284: <pre>
2285: PCRE_ERROR_INTERNAL (-14)
2286: </pre>
2287: An unexpected internal error has occurred. This error could be caused by a bug
2288: in PCRE or by overwriting of the compiled pattern.
2289: <pre>
2290: PCRE_ERROR_BADCOUNT (-15)
2291: </pre>
2292: This error is given if the value of the <i>ovecsize</i> argument is negative.
2293: <pre>
2294: PCRE_ERROR_RECURSIONLIMIT (-21)
2295: </pre>
2296: The internal recursion limit, as specified by the <i>match_limit_recursion</i>
2297: field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
2298: description above.
2299: <pre>
2300: PCRE_ERROR_BADNEWLINE (-23)
2301: </pre>
2302: An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given.
2303: <pre>
2304: PCRE_ERROR_BADOFFSET (-24)
2305: </pre>
2306: The value of <i>startoffset</i> was negative or greater than the length of the
2307: subject, that is, the value in <i>length</i>.
2308: <pre>
2309: PCRE_ERROR_SHORTUTF8 (-25)
2310: </pre>
2311: This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2312: ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2313: Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2314: fact sufficient to detect this case, but this special error code for
2315: PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2316: retained for backwards compatibility.
2317: <pre>
2318: PCRE_ERROR_RECURSELOOP (-26)
2319: </pre>
2320: This error is returned when <b>pcre_exec()</b> detects a recursion loop within
2321: the pattern. Specifically, it means that either the whole pattern or a
2322: subpattern has been called recursively for the second time at the same position
2323: in the subject string. Some simple patterns that might do this are detected and
2324: faulted at compile time, but more complicated cases, in particular mutual
2325: recursions between two different subpatterns, cannot be detected until run
2326: time.
2327: <pre>
2328: PCRE_ERROR_JIT_STACKLIMIT (-27)
2329: </pre>
1.1.1.3 misho 2330: This error is returned when a pattern that was successfully studied using a
2331: JIT compile option is being matched, but the memory available for the
2332: just-in-time processing stack is not large enough. See the
1.1 misho 2333: <a href="pcrejit.html"><b>pcrejit</b></a>
2334: documentation for more details.
1.1.1.2 misho 2335: <pre>
1.1.1.3 misho 2336: PCRE_ERROR_BADMODE (-28)
1.1.1.2 misho 2337: </pre>
2338: This error is given if a pattern that was compiled by the 8-bit library is
1.1.1.4 misho 2339: passed to a 16-bit or 32-bit library function, or vice versa.
1.1.1.2 misho 2340: <pre>
1.1.1.3 misho 2341: PCRE_ERROR_BADENDIANNESS (-29)
1.1.1.2 misho 2342: </pre>
2343: This error is given if a pattern that was compiled and saved is reloaded on a
2344: host with different endianness. The utility function
2345: <b>pcre_pattern_to_host_byte_order()</b> can be used to convert such a pattern
2346: so that it runs on the new host.
1.1.1.4 misho 2347: <pre>
2348: PCRE_ERROR_JIT_BADOPTION
2349: </pre>
2350: This error is returned when a pattern that was successfully studied using a JIT
2351: compile option is being matched, but the matching mode (partial or complete
2352: match) does not correspond to any JIT compilation mode. When the JIT fast path
2353: function is used, this error may be also given for invalid options. See the
2354: <a href="pcrejit.html"><b>pcrejit</b></a>
2355: documentation for more details.
2356: <pre>
2357: PCRE_ERROR_BADLENGTH (-32)
2358: </pre>
2359: This error is given if <b>pcre_exec()</b> is called with a negative value for
2360: the <i>length</i> argument.
1.1 misho 2361: </P>
2362: <P>
1.1.1.4 misho 2363: Error numbers -16 to -20, -22, and 30 are not used by <b>pcre_exec()</b>.
1.1 misho 2364: <a name="badutf8reasons"></a></P>
2365: <br><b>
2366: Reason codes for invalid UTF-8 strings
2367: </b><br>
2368: <P>
1.1.1.2 misho 2369: This section applies only to the 8-bit library. The corresponding information
1.1.1.4 misho 2370: for the 16-bit and 32-bit libraries is given in the
1.1.1.2 misho 2371: <a href="pcre16.html"><b>pcre16</b></a>
1.1.1.4 misho 2372: and
2373: <a href="pcre32.html"><b>pcre32</b></a>
2374: pages.
1.1.1.2 misho 2375: </P>
2376: <P>
1.1 misho 2377: When <b>pcre_exec()</b> returns either PCRE_ERROR_BADUTF8 or
2378: PCRE_ERROR_SHORTUTF8, and the size of the output vector (<i>ovecsize</i>) is at
2379: least 2, the offset of the start of the invalid UTF-8 character is placed in
2380: the first output vector element (<i>ovector[0]</i>) and a reason code is placed
2381: in the second element (<i>ovector[1]</i>). The reason codes are given names in
2382: the <b>pcre.h</b> header file:
2383: <pre>
2384: PCRE_UTF8_ERR1
2385: PCRE_UTF8_ERR2
2386: PCRE_UTF8_ERR3
2387: PCRE_UTF8_ERR4
2388: PCRE_UTF8_ERR5
2389: </pre>
2390: The string ends with a truncated UTF-8 character; the code specifies how many
2391: bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2392: no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2393: allows for up to 6 bytes, and this is checked first; hence the possibility of
2394: 4 or 5 missing bytes.
2395: <pre>
2396: PCRE_UTF8_ERR6
2397: PCRE_UTF8_ERR7
2398: PCRE_UTF8_ERR8
2399: PCRE_UTF8_ERR9
2400: PCRE_UTF8_ERR10
2401: </pre>
2402: The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2403: character do not have the binary value 0b10 (that is, either the most
2404: significant bit is 0, or the next bit is 1).
2405: <pre>
2406: PCRE_UTF8_ERR11
2407: PCRE_UTF8_ERR12
2408: </pre>
2409: A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2410: these code points are excluded by RFC 3629.
2411: <pre>
2412: PCRE_UTF8_ERR13
2413: </pre>
2414: A 4-byte character has a value greater than 0x10fff; these code points are
2415: excluded by RFC 3629.
2416: <pre>
2417: PCRE_UTF8_ERR14
2418: </pre>
2419: A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2420: code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2421: from UTF-8.
2422: <pre>
2423: PCRE_UTF8_ERR15
2424: PCRE_UTF8_ERR16
2425: PCRE_UTF8_ERR17
2426: PCRE_UTF8_ERR18
2427: PCRE_UTF8_ERR19
2428: </pre>
2429: A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2430: value that can be represented by fewer bytes, which is invalid. For example,
2431: the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2432: one byte.
2433: <pre>
2434: PCRE_UTF8_ERR20
2435: </pre>
2436: The two most significant bits of the first byte of a character have the binary
2437: value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2438: byte can only validly occur as the second or subsequent byte of a multi-byte
2439: character.
2440: <pre>
2441: PCRE_UTF8_ERR21
2442: </pre>
2443: The first byte of a character has the value 0xfe or 0xff. These values can
2444: never occur in a valid UTF-8 string.
1.1.1.4 misho 2445: <pre>
2446: PCRE_UTF8_ERR22
2447: </pre>
2448: This error code was formerly used when the presence of a so-called
2449: "non-character" caused an error. Unicode corrigendum #9 makes it clear that
2450: such characters should not cause a string to be rejected, and so this code is
2451: no longer in use and is never returned.
1.1 misho 2452: </P>
1.1.1.2 misho 2453: <br><a name="SEC18" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
1.1 misho 2454: <P>
2455: <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1.1.1.5 ! misho 2456: <b> int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
! 2457: <b> int <i>buffersize</i>);</b>
! 2458: <br>
! 2459: <br>
1.1 misho 2460: <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
1.1.1.5 ! misho 2461: <b> int <i>stringcount</i>, int <i>stringnumber</i>,</b>
! 2462: <b> const char **<i>stringptr</i>);</b>
! 2463: <br>
! 2464: <br>
1.1 misho 2465: <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
1.1.1.5 ! misho 2466: <b> int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
1.1 misho 2467: </P>
2468: <P>
2469: Captured substrings can be accessed directly by using the offsets returned by
2470: <b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions
2471: <b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and
2472: <b>pcre_get_substring_list()</b> are provided for extracting captured substrings
2473: as new, separate, zero-terminated strings. These functions identify substrings
2474: by number. The next section describes functions for extracting named
2475: substrings.
2476: </P>
2477: <P>
2478: A substring that contains a binary zero is correctly extracted and has a
2479: further zero added on the end, but the result is not, of course, a C string.
2480: However, you can process such a string by referring to the length that is
2481: returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>.
2482: Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate
2483: for handling strings containing binary zeros, because the end of the final
2484: string is not independently indicated.
2485: </P>
2486: <P>
2487: The first three arguments are the same for all three of these functions:
2488: <i>subject</i> is the subject string that has just been successfully matched,
2489: <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
2490: <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
2491: captured by the match, including the substring that matched the entire regular
2492: expression. This is the value returned by <b>pcre_exec()</b> if it is greater
2493: than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
2494: space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
2495: number of elements in the vector divided by three.
2496: </P>
2497: <P>
2498: The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
2499: extract a single substring, whose number is given as <i>stringnumber</i>. A
2500: value of zero extracts the substring that matched the entire pattern, whereas
2501: higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
2502: the string is placed in <i>buffer</i>, whose length is given by
2503: <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
2504: obtained via <b>pcre_malloc</b>, and its address is returned via
2505: <i>stringptr</i>. The yield of the function is the length of the string, not
2506: including the terminating zero, or one of these error codes:
2507: <pre>
2508: PCRE_ERROR_NOMEMORY (-6)
2509: </pre>
2510: The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
2511: memory failed for <b>pcre_get_substring()</b>.
2512: <pre>
2513: PCRE_ERROR_NOSUBSTRING (-7)
2514: </pre>
2515: There is no substring whose number is <i>stringnumber</i>.
2516: </P>
2517: <P>
2518: The <b>pcre_get_substring_list()</b> function extracts all available substrings
2519: and builds a list of pointers to them. All this is done in a single block of
2520: memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
2521: is returned via <i>listptr</i>, which is also the start of the list of string
2522: pointers. The end of the list is marked by a NULL pointer. The yield of the
2523: function is zero if all went well, or the error code
2524: <pre>
2525: PCRE_ERROR_NOMEMORY (-6)
2526: </pre>
2527: if the attempt to get the memory block failed.
2528: </P>
2529: <P>
2530: When any of these functions encounter a substring that is unset, which can
2531: happen when capturing subpattern number <i>n+1</i> matches some part of the
2532: subject, but subpattern <i>n</i> has not been used at all, they return an empty
2533: string. This can be distinguished from a genuine zero-length substring by
2534: inspecting the appropriate offset in <i>ovector</i>, which is negative for unset
2535: substrings.
2536: </P>
2537: <P>
2538: The two convenience functions <b>pcre_free_substring()</b> and
2539: <b>pcre_free_substring_list()</b> can be used to free the memory returned by
2540: a previous call of <b>pcre_get_substring()</b> or
2541: <b>pcre_get_substring_list()</b>, respectively. They do nothing more than call
2542: the function pointed to by <b>pcre_free</b>, which of course could be called
2543: directly from a C program. However, PCRE is used in some situations where it is
2544: linked via a special interface to another programming language that cannot use
2545: <b>pcre_free</b> directly; it is for these cases that the functions are
2546: provided.
2547: </P>
1.1.1.2 misho 2548: <br><a name="SEC19" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
1.1 misho 2549: <P>
2550: <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
1.1.1.5 ! misho 2551: <b> const char *<i>name</i>);</b>
! 2552: <br>
! 2553: <br>
1.1 misho 2554: <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
1.1.1.5 ! misho 2555: <b> const char *<i>subject</i>, int *<i>ovector</i>,</b>
! 2556: <b> int <i>stringcount</i>, const char *<i>stringname</i>,</b>
! 2557: <b> char *<i>buffer</i>, int <i>buffersize</i>);</b>
! 2558: <br>
! 2559: <br>
1.1 misho 2560: <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
1.1.1.5 ! misho 2561: <b> const char *<i>subject</i>, int *<i>ovector</i>,</b>
! 2562: <b> int <i>stringcount</i>, const char *<i>stringname</i>,</b>
! 2563: <b> const char **<i>stringptr</i>);</b>
1.1 misho 2564: </P>
2565: <P>
2566: To extract a substring by name, you first have to find associated number.
2567: For example, for this pattern
2568: <pre>
2569: (a+)b(?<xxx>\d+)...
2570: </pre>
2571: the number of the subpattern called "xxx" is 2. If the name is known to be
2572: unique (PCRE_DUPNAMES was not set), you can find the number from the name by
2573: calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled
2574: pattern, and the second is the name. The yield of the function is the
2575: subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2576: that name.
2577: </P>
2578: <P>
2579: Given the number, you can extract the substring directly, or use one of the
2580: functions described in the previous section. For convenience, there are also
2581: two functions that do the whole job.
2582: </P>
2583: <P>
2584: Most of the arguments of <b>pcre_copy_named_substring()</b> and
2585: <b>pcre_get_named_substring()</b> are the same as those for the similarly named
2586: functions that extract by number. As these are described in the previous
2587: section, they are not re-described here. There are just two differences:
2588: </P>
2589: <P>
2590: First, instead of a substring number, a substring name is given. Second, there
2591: is an extra argument, given at the start, which is a pointer to the compiled
2592: pattern. This is needed in order to gain access to the name-to-number
2593: translation table.
2594: </P>
2595: <P>
2596: These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they
2597: then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as
2598: appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names,
2599: the behaviour may not be what you want (see the next section).
2600: </P>
2601: <P>
2602: <b>Warning:</b> If the pattern uses the (?| feature to set up multiple
2603: subpatterns with the same number, as described in the
2604: <a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
2605: in the
2606: <a href="pcrepattern.html"><b>pcrepattern</b></a>
2607: page, you cannot use names to distinguish the different subpatterns, because
2608: names are not included in the compiled code. The matching process uses only
2609: numbers. For this reason, the use of different names for subpatterns of the
2610: same number causes an error at compile time.
2611: </P>
1.1.1.2 misho 2612: <br><a name="SEC20" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
1.1 misho 2613: <P>
2614: <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
1.1.1.5 ! misho 2615: <b> const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
1.1 misho 2616: </P>
2617: <P>
2618: When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2619: are not required to be unique. (Duplicate names are always allowed for
2620: subpatterns with the same number, created by using the (?| feature. Indeed, if
2621: such subpatterns are named, they are required to use the same names.)
2622: </P>
2623: <P>
2624: Normally, patterns with duplicate names are such that in any one match, only
2625: one of the named subpatterns participates. An example is shown in the
2626: <a href="pcrepattern.html"><b>pcrepattern</b></a>
2627: documentation.
2628: </P>
2629: <P>
2630: When duplicates are present, <b>pcre_copy_named_substring()</b> and
2631: <b>pcre_get_named_substring()</b> return the first substring corresponding to
2632: the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2633: returned; no data is returned. The <b>pcre_get_stringnumber()</b> function
2634: returns one of the numbers that are associated with the name, but it is not
2635: defined which it is.
2636: </P>
2637: <P>
2638: If you want to get full details of all captured substrings for a given name,
2639: you must use the <b>pcre_get_stringtable_entries()</b> function. The first
2640: argument is the compiled pattern, and the second is the name. The third and
2641: fourth are pointers to variables which are updated by the function. After it
2642: has run, they point to the first and last entries in the name-to-number table
2643: for the given name. The function itself returns the length of each entry, or
2644: PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2645: described above in the section entitled <i>Information about a pattern</i>
2646: <a href="#infoaboutpattern">above.</a>
2647: Given all the relevant entries for the name, you can extract each of their
2648: numbers, and hence the captured data, if any.
2649: </P>
1.1.1.2 misho 2650: <br><a name="SEC21" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
1.1 misho 2651: <P>
2652: The traditional matching function uses a similar algorithm to Perl, which stops
2653: when it finds the first match, starting at a given point in the subject. If you
2654: want to find all possible matches, or the longest possible match, consider
2655: using the alternative matching function (see below) instead. If you cannot use
2656: the alternative function, but still need to find all possible matches, you
2657: can kludge it up by making use of the callout facility, which is described in
2658: the
2659: <a href="pcrecallout.html"><b>pcrecallout</b></a>
2660: documentation.
2661: </P>
2662: <P>
2663: What you have to do is to insert a callout right at the end of the pattern.
2664: When your callout function is called, extract and save the current matched
2665: substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
2666: other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
2667: will yield PCRE_ERROR_NOMATCH.
1.1.1.2 misho 2668: </P>
2669: <br><a name="SEC22" href="#TOC1">OBTAINING AN ESTIMATE OF STACK USAGE</a><br>
2670: <P>
2671: Matching certain patterns using <b>pcre_exec()</b> can use a lot of process
2672: stack, which in certain environments can be rather limited in size. Some users
2673: find it helpful to have an estimate of the amount of stack that is used by
2674: <b>pcre_exec()</b>, to help them set recursion limits, as described in the
2675: <a href="pcrestack.html"><b>pcrestack</b></a>
2676: documentation. The estimate that is output by <b>pcretest</b> when called with
2677: the <b>-m</b> and <b>-C</b> options is obtained by calling <b>pcre_exec</b> with
2678: the values NULL, NULL, NULL, -999, and -999 for its first five arguments.
2679: </P>
2680: <P>
2681: Normally, if its first argument is NULL, <b>pcre_exec()</b> immediately returns
2682: the negative error code PCRE_ERROR_NULL, but with this special combination of
2683: arguments, it returns instead a negative number whose absolute value is the
2684: approximate stack frame size in bytes. (A negative number is used so that it is
2685: clear that no match has happened.) The value is approximate because in some
2686: cases, recursive calls to <b>pcre_exec()</b> occur when there are one or two
2687: additional variables on the stack.
2688: </P>
2689: <P>
2690: If PCRE has been compiled to use the heap instead of the stack for recursion,
2691: the value returned is the size of each block that is obtained from the heap.
1.1 misho 2692: <a name="dfamatch"></a></P>
1.1.1.2 misho 2693: <br><a name="SEC23" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
1.1 misho 2694: <P>
2695: <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1.1.1.5 ! misho 2696: <b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
! 2697: <b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
! 2698: <b> int *<i>workspace</i>, int <i>wscount</i>);</b>
1.1 misho 2699: </P>
2700: <P>
2701: The function <b>pcre_dfa_exec()</b> is called to match a subject string against
2702: a compiled pattern, using a matching algorithm that scans the subject string
2703: just once, and does not backtrack. This has different characteristics to the
2704: normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2705: patterns are not supported. Nevertheless, there are times when this kind of
2706: matching can be useful. For a discussion of the two matching algorithms, and a
2707: list of features that <b>pcre_dfa_exec()</b> does not support, see the
2708: <a href="pcrematching.html"><b>pcrematching</b></a>
2709: documentation.
2710: </P>
2711: <P>
2712: The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
2713: <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
2714: different way, and this is described below. The other common arguments are used
2715: in the same way as for <b>pcre_exec()</b>, so their description is not repeated
2716: here.
2717: </P>
2718: <P>
2719: The two additional arguments provide workspace for the function. The workspace
2720: vector should contain at least 20 elements. It is used for keeping track of
2721: multiple paths through the pattern tree. More workspace will be needed for
2722: patterns and subjects where there are a lot of potential matches.
2723: </P>
2724: <P>
2725: Here is an example of a simple call to <b>pcre_dfa_exec()</b>:
2726: <pre>
2727: int rc;
2728: int ovector[10];
2729: int wspace[20];
2730: rc = pcre_dfa_exec(
2731: re, /* result of pcre_compile() */
2732: NULL, /* we didn't study the pattern */
2733: "some string", /* the subject string */
2734: 11, /* the length of the subject string */
2735: 0, /* start at offset 0 in the subject */
2736: 0, /* default options */
2737: ovector, /* vector of integers for substring information */
2738: 10, /* number of elements (NOT size in bytes) */
2739: wspace, /* working space vector */
2740: 20); /* number of elements (NOT size in bytes) */
2741: </PRE>
2742: </P>
2743: <br><b>
2744: Option bits for <b>pcre_dfa_exec()</b>
2745: </b><br>
2746: <P>
2747: The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
2748: zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
2749: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2750: PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2751: PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2752: All but the last four of these are exactly the same as for <b>pcre_exec()</b>,
2753: so their description is not repeated here.
2754: <pre>
2755: PCRE_PARTIAL_HARD
2756: PCRE_PARTIAL_SOFT
2757: </pre>
2758: These have the same general effect as they do for <b>pcre_exec()</b>, but the
2759: details are slightly different. When PCRE_PARTIAL_HARD is set for
2760: <b>pcre_dfa_exec()</b>, it returns PCRE_ERROR_PARTIAL if the end of the subject
2761: is reached and there is still at least one matching possibility that requires
2762: additional characters. This happens even if some complete matches have also
2763: been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2764: is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2765: there have been no complete matches, but there is still at least one matching
2766: possibility. The portion of the string that was inspected when the longest
2767: partial match was found is set as the first matching string in both cases.
2768: There is a more detailed discussion of partial and multi-segment matching, with
2769: examples, in the
2770: <a href="pcrepartial.html"><b>pcrepartial</b></a>
2771: documentation.
2772: <pre>
2773: PCRE_DFA_SHORTEST
2774: </pre>
2775: Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2776: soon as it has found one match. Because of the way the alternative algorithm
2777: works, this is necessarily the shortest possible match at the first possible
2778: matching point in the subject string.
2779: <pre>
2780: PCRE_DFA_RESTART
2781: </pre>
2782: When <b>pcre_dfa_exec()</b> returns a partial match, it is possible to call it
2783: again, with additional subject characters, and have it continue with the same
2784: match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2785: <i>workspace</i> and <i>wscount</i> options must reference the same vector as
2786: before because data about the match so far is left in them after a partial
2787: match. There is more discussion of this facility in the
2788: <a href="pcrepartial.html"><b>pcrepartial</b></a>
2789: documentation.
2790: </P>
2791: <br><b>
2792: Successful returns from <b>pcre_dfa_exec()</b>
2793: </b><br>
2794: <P>
2795: When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
2796: substring in the subject. Note, however, that all the matches from one run of
2797: the function start at the same point in the subject. The shorter matches are
2798: all initial substrings of the longer matches. For example, if the pattern
2799: <pre>
2800: <.*>
2801: </pre>
2802: is matched against the string
2803: <pre>
2804: This is <something> <something else> <something further> no more
2805: </pre>
2806: the three matched strings are
2807: <pre>
2808: <something>
2809: <something> <something else>
2810: <something> <something else> <something further>
2811: </pre>
2812: On success, the yield of the function is a number greater than zero, which is
2813: the number of matched substrings. The substrings themselves are returned in
2814: <i>ovector</i>. Each string uses two elements; the first is the offset to the
2815: start, and the second is the offset to the end. In fact, all the strings have
2816: the same start offset. (Space could have been saved by giving this only once,
2817: but it was decided to retain some compatibility with the way <b>pcre_exec()</b>
2818: returns data, even though the meaning of the strings is different.)
2819: </P>
2820: <P>
2821: The strings are returned in reverse order of length; that is, the longest
2822: matching string is given first. If there were too many matches to fit into
2823: <i>ovector</i>, the yield of the function is zero, and the vector is filled with
2824: the longest matches. Unlike <b>pcre_exec()</b>, <b>pcre_dfa_exec()</b> can use
2825: the entire <i>ovector</i> for returning matched strings.
2826: </P>
1.1.1.5 ! misho 2827: <P>
! 2828: NOTE: PCRE's "auto-possessification" optimization usually applies to character
! 2829: repeats at the end of a pattern (as well as internally). For example, the
! 2830: pattern "a\d+" is compiled as if it were "a\d++" because there is no point
! 2831: even considering the possibility of backtracking into the repeated digits. For
! 2832: DFA matching, this means that only one possible match is found. If you really
! 2833: do want multiple matches in such cases, either use an ungreedy repeat
! 2834: ("a\d+?") or set the PCRE_NO_AUTO_POSSESS option when compiling.
! 2835: </P>
1.1 misho 2836: <br><b>
2837: Error returns from <b>pcre_dfa_exec()</b>
2838: </b><br>
2839: <P>
2840: The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
2841: Many of the errors are the same as for <b>pcre_exec()</b>, and these are
2842: described
2843: <a href="#errorlist">above.</a>
2844: There are in addition the following errors that are specific to
2845: <b>pcre_dfa_exec()</b>:
2846: <pre>
2847: PCRE_ERROR_DFA_UITEM (-16)
2848: </pre>
2849: This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
2850: that it does not support, for instance, the use of \C or a back reference.
2851: <pre>
2852: PCRE_ERROR_DFA_UCOND (-17)
2853: </pre>
2854: This return is given if <b>pcre_dfa_exec()</b> encounters a condition item that
2855: uses a back reference for the condition, or a test for recursion in a specific
2856: group. These are not supported.
2857: <pre>
2858: PCRE_ERROR_DFA_UMLIMIT (-18)
2859: </pre>
2860: This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
2861: block that contains a setting of the <i>match_limit</i> or
2862: <i>match_limit_recursion</i> fields. This is not supported (these fields are
2863: meaningless for DFA matching).
2864: <pre>
2865: PCRE_ERROR_DFA_WSSIZE (-19)
2866: </pre>
2867: This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
2868: <i>workspace</i> vector.
2869: <pre>
2870: PCRE_ERROR_DFA_RECURSE (-20)
2871: </pre>
2872: When a recursive subpattern is processed, the matching function calls itself
2873: recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
2874: error is given if the output vector is not large enough. This should be
2875: extremely rare, as a vector of size 1000 is used.
1.1.1.3 misho 2876: <pre>
2877: PCRE_ERROR_DFA_BADRESTART (-30)
2878: </pre>
2879: When <b>pcre_dfa_exec()</b> is called with the <b>PCRE_DFA_RESTART</b> option,
2880: some plausibility checks are made on the contents of the workspace, which
2881: should contain data about the previous partial match. If any of these checks
2882: fail, this error is given.
1.1 misho 2883: </P>
1.1.1.2 misho 2884: <br><a name="SEC24" href="#TOC1">SEE ALSO</a><br>
1.1 misho 2885: <P>
1.1.1.4 misho 2886: <b>pcre16</b>(3), <b>pcre32</b>(3), <b>pcrebuild</b>(3), <b>pcrecallout</b>(3),
2887: <b>pcrecpp(3)</b>(3), <b>pcrematching</b>(3), <b>pcrepartial</b>(3),
2888: <b>pcreposix</b>(3), <b>pcreprecompile</b>(3), <b>pcresample</b>(3),
2889: <b>pcrestack</b>(3).
1.1 misho 2890: </P>
1.1.1.2 misho 2891: <br><a name="SEC25" href="#TOC1">AUTHOR</a><br>
1.1 misho 2892: <P>
2893: Philip Hazel
2894: <br>
2895: University Computing Service
2896: <br>
2897: Cambridge CB2 3QH, England.
2898: <br>
2899: </P>
1.1.1.2 misho 2900: <br><a name="SEC26" href="#TOC1">REVISION</a><br>
1.1 misho 2901: <P>
1.1.1.5 ! misho 2902: Last updated: 12 November 2013
1.1 misho 2903: <br>
1.1.1.4 misho 2904: Copyright © 1997-2013 University of Cambridge.
1.1 misho 2905: <br>
2906: <p>
2907: Return to the <a href="index.html">PCRE index page</a>.
2908: </p>
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