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3: <title>pcreapi specification</title>
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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>
17: <li><a name="TOC2" href="#SEC2">PCRE NATIVE API AUXILIARY FUNCTIONS</a>
18: <li><a name="TOC3" href="#SEC3">PCRE NATIVE API INDIRECTED FUNCTIONS</a>
19: <li><a name="TOC4" href="#SEC4">PCRE API OVERVIEW</a>
20: <li><a name="TOC5" href="#SEC5">NEWLINES</a>
21: <li><a name="TOC6" href="#SEC6">MULTITHREADING</a>
22: <li><a name="TOC7" href="#SEC7">SAVING PRECOMPILED PATTERNS FOR LATER USE</a>
23: <li><a name="TOC8" href="#SEC8">CHECKING BUILD-TIME OPTIONS</a>
24: <li><a name="TOC9" href="#SEC9">COMPILING A PATTERN</a>
25: <li><a name="TOC10" href="#SEC10">COMPILATION ERROR CODES</a>
26: <li><a name="TOC11" href="#SEC11">STUDYING A PATTERN</a>
27: <li><a name="TOC12" href="#SEC12">LOCALE SUPPORT</a>
28: <li><a name="TOC13" href="#SEC13">INFORMATION ABOUT A PATTERN</a>
29: <li><a name="TOC14" href="#SEC14">OBSOLETE INFO FUNCTION</a>
30: <li><a name="TOC15" href="#SEC15">REFERENCE COUNTS</a>
31: <li><a name="TOC16" href="#SEC16">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a>
32: <li><a name="TOC17" href="#SEC17">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a>
33: <li><a name="TOC18" href="#SEC18">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a>
34: <li><a name="TOC19" href="#SEC19">DUPLICATE SUBPATTERN NAMES</a>
35: <li><a name="TOC20" href="#SEC20">FINDING ALL POSSIBLE MATCHES</a>
36: <li><a name="TOC21" href="#SEC21">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a>
37: <li><a name="TOC22" href="#SEC22">SEE ALSO</a>
38: <li><a name="TOC23" href="#SEC23">AUTHOR</a>
39: <li><a name="TOC24" href="#SEC24">REVISION</a>
40: </ul>
41: <br><a name="SEC1" href="#TOC1">PCRE NATIVE API BASIC FUNCTIONS</a><br>
42: <P>
43: <b>#include <pcre.h></b>
44: </P>
45: <P>
46: <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
47: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
48: <b>const unsigned char *<i>tableptr</i>);</b>
49: </P>
50: <P>
51: <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
52: <b>int *<i>errorcodeptr</i>,</b>
53: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
54: <b>const unsigned char *<i>tableptr</i>);</b>
55: </P>
56: <P>
57: <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
58: <b>const char **<i>errptr</i>);</b>
59: </P>
60: <P>
61: <b>void pcre_free_study(pcre_extra *<i>extra</i>);</b>
62: </P>
63: <P>
64: <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
65: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
66: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
67: </P>
68: <br><a name="SEC2" href="#TOC1">PCRE NATIVE API AUXILIARY FUNCTIONS</a><br>
69: <P>
70: <b>pcre_jit_stack *pcre_jit_stack_alloc(int <i>startsize</i>, int <i>maxsize</i>);</b>
71: </P>
72: <P>
73: <b>void pcre_jit_stack_free(pcre_jit_stack *<i>stack</i>);</b>
74: </P>
75: <P>
76: <b>void pcre_assign_jit_stack(pcre_extra *<i>extra</i>,</b>
77: <b>pcre_jit_callback <i>callback</i>, void *<i>data</i>);</b>
78: </P>
79: <P>
80: <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
81: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
82: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
83: <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
84: </P>
85: <P>
86: <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
87: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
88: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
89: <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
90: </P>
91: <P>
92: <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
93: <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
94: <b>int <i>buffersize</i>);</b>
95: </P>
96: <P>
97: <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
98: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
99: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
100: <b>const char **<i>stringptr</i>);</b>
101: </P>
102: <P>
103: <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
104: <b>const char *<i>name</i>);</b>
105: </P>
106: <P>
107: <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
108: <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
109: </P>
110: <P>
111: <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
112: <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
113: <b>const char **<i>stringptr</i>);</b>
114: </P>
115: <P>
116: <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
117: <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
118: </P>
119: <P>
120: <b>void pcre_free_substring(const char *<i>stringptr</i>);</b>
121: </P>
122: <P>
123: <b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b>
124: </P>
125: <P>
126: <b>const unsigned char *pcre_maketables(void);</b>
127: </P>
128: <P>
129: <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
130: <b>int <i>what</i>, void *<i>where</i>);</b>
131: </P>
132: <P>
133: <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
134: <b>*<i>firstcharptr</i>);</b>
135: </P>
136: <P>
137: <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
138: </P>
139: <P>
140: <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
141: </P>
142: <P>
143: <b>char *pcre_version(void);</b>
144: </P>
145: <br><a name="SEC3" href="#TOC1">PCRE NATIVE API INDIRECTED FUNCTIONS</a><br>
146: <P>
147: <b>void *(*pcre_malloc)(size_t);</b>
148: </P>
149: <P>
150: <b>void (*pcre_free)(void *);</b>
151: </P>
152: <P>
153: <b>void *(*pcre_stack_malloc)(size_t);</b>
154: </P>
155: <P>
156: <b>void (*pcre_stack_free)(void *);</b>
157: </P>
158: <P>
159: <b>int (*pcre_callout)(pcre_callout_block *);</b>
160: </P>
161: <br><a name="SEC4" href="#TOC1">PCRE API OVERVIEW</a><br>
162: <P>
163: PCRE has its own native API, which is described in this document. There are
164: also some wrapper functions that correspond to the POSIX regular expression
165: API, but they do not give access to all the functionality. They are described
166: in the
167: <a href="pcreposix.html"><b>pcreposix</b></a>
168: documentation. Both of these APIs define a set of C function calls. A C++
169: wrapper is also distributed with PCRE. It is documented in the
170: <a href="pcrecpp.html"><b>pcrecpp</b></a>
171: page.
172: </P>
173: <P>
174: The native API C function prototypes are defined in the header file
175: <b>pcre.h</b>, and on Unix systems the library itself is called <b>libpcre</b>.
176: It can normally be accessed by adding <b>-lpcre</b> to the command for linking
177: an application that uses PCRE. The header file defines the macros PCRE_MAJOR
178: and PCRE_MINOR to contain the major and minor release numbers for the library.
179: Applications can use these to include support for different releases of PCRE.
180: </P>
181: <P>
182: In a Windows environment, if you want to statically link an application program
183: against a non-dll <b>pcre.a</b> file, you must define PCRE_STATIC before
184: including <b>pcre.h</b> or <b>pcrecpp.h</b>, because otherwise the
185: <b>pcre_malloc()</b> and <b>pcre_free()</b> exported functions will be declared
186: <b>__declspec(dllimport)</b>, with unwanted results.
187: </P>
188: <P>
189: The functions <b>pcre_compile()</b>, <b>pcre_compile2()</b>, <b>pcre_study()</b>,
190: and <b>pcre_exec()</b> are used for compiling and matching regular expressions
191: in a Perl-compatible manner. A sample program that demonstrates the simplest
192: way of using them is provided in the file called <i>pcredemo.c</i> in the PCRE
193: source distribution. A listing of this program is given in the
194: <a href="pcredemo.html"><b>pcredemo</b></a>
195: documentation, and the
196: <a href="pcresample.html"><b>pcresample</b></a>
197: documentation describes how to compile and run it.
198: </P>
199: <P>
200: Just-in-time compiler support is an optional feature of PCRE that can be built
201: in appropriate hardware environments. It greatly speeds up the matching
202: performance of many patterns. Simple programs can easily request that it be
203: used if available, by setting an option that is ignored when it is not
204: relevant. More complicated programs might need to make use of the functions
205: <b>pcre_jit_stack_alloc()</b>, <b>pcre_jit_stack_free()</b>, and
206: <b>pcre_assign_jit_stack()</b> in order to control the JIT code's memory usage.
207: These functions are discussed in the
208: <a href="pcrejit.html"><b>pcrejit</b></a>
209: documentation.
210: </P>
211: <P>
212: A second matching function, <b>pcre_dfa_exec()</b>, which is not
213: Perl-compatible, is also provided. This uses a different algorithm for the
214: matching. The alternative algorithm finds all possible matches (at a given
215: point in the subject), and scans the subject just once (unless there are
216: lookbehind assertions). However, this algorithm does not return captured
217: substrings. A description of the two matching algorithms and their advantages
218: and disadvantages is given in the
219: <a href="pcrematching.html"><b>pcrematching</b></a>
220: documentation.
221: </P>
222: <P>
223: In addition to the main compiling and matching functions, there are convenience
224: functions for extracting captured substrings from a subject string that is
225: matched by <b>pcre_exec()</b>. They are:
226: <pre>
227: <b>pcre_copy_substring()</b>
228: <b>pcre_copy_named_substring()</b>
229: <b>pcre_get_substring()</b>
230: <b>pcre_get_named_substring()</b>
231: <b>pcre_get_substring_list()</b>
232: <b>pcre_get_stringnumber()</b>
233: <b>pcre_get_stringtable_entries()</b>
234: </pre>
235: <b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also
236: provided, to free the memory used for extracted strings.
237: </P>
238: <P>
239: The function <b>pcre_maketables()</b> is used to build a set of character tables
240: in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>,
241: or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for
242: specialist use. Most commonly, no special tables are passed, in which case
243: internal tables that are generated when PCRE is built are used.
244: </P>
245: <P>
246: The function <b>pcre_fullinfo()</b> is used to find out information about a
247: compiled pattern; <b>pcre_info()</b> is an obsolete version that returns only
248: some of the available information, but is retained for backwards compatibility.
249: The function <b>pcre_version()</b> returns a pointer to a string containing the
250: version of PCRE and its date of release.
251: </P>
252: <P>
253: The function <b>pcre_refcount()</b> maintains a reference count in a data block
254: containing a compiled pattern. This is provided for the benefit of
255: object-oriented applications.
256: </P>
257: <P>
258: The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain
259: the entry points of the standard <b>malloc()</b> and <b>free()</b> functions,
260: respectively. PCRE calls the memory management functions via these variables,
261: so a calling program can replace them if it wishes to intercept the calls. This
262: should be done before calling any PCRE functions.
263: </P>
264: <P>
265: The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also
266: indirections to memory management functions. These special functions are used
267: only when PCRE is compiled to use the heap for remembering data, instead of
268: recursive function calls, when running the <b>pcre_exec()</b> function. See the
269: <a href="pcrebuild.html"><b>pcrebuild</b></a>
270: documentation for details of how to do this. It is a non-standard way of
271: building PCRE, for use in environments that have limited stacks. Because of the
272: greater use of memory management, it runs more slowly. Separate functions are
273: provided so that special-purpose external code can be used for this case. When
274: used, these functions are always called in a stack-like manner (last obtained,
275: first freed), and always for memory blocks of the same size. There is a
276: discussion about PCRE's stack usage in the
277: <a href="pcrestack.html"><b>pcrestack</b></a>
278: documentation.
279: </P>
280: <P>
281: The global variable <b>pcre_callout</b> initially contains NULL. It can be set
282: by the caller to a "callout" function, which PCRE will then call at specified
283: points during a matching operation. Details are given in the
284: <a href="pcrecallout.html"><b>pcrecallout</b></a>
285: documentation.
286: <a name="newlines"></a></P>
287: <br><a name="SEC5" href="#TOC1">NEWLINES</a><br>
288: <P>
289: PCRE supports five different conventions for indicating line breaks in
290: strings: a single CR (carriage return) character, a single LF (linefeed)
291: character, the two-character sequence CRLF, any of the three preceding, or any
292: Unicode newline sequence. The Unicode newline sequences are the three just
293: mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
294: U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
295: (paragraph separator, U+2029).
296: </P>
297: <P>
298: Each of the first three conventions is used by at least one operating system as
299: its standard newline sequence. When PCRE is built, a default can be specified.
300: The default default is LF, which is the Unix standard. When PCRE is run, the
301: default can be overridden, either when a pattern is compiled, or when it is
302: matched.
303: </P>
304: <P>
305: At compile time, the newline convention can be specified by the <i>options</i>
306: argument of <b>pcre_compile()</b>, or it can be specified by special text at the
307: start of the pattern itself; this overrides any other settings. See the
308: <a href="pcrepattern.html"><b>pcrepattern</b></a>
309: page for details of the special character sequences.
310: </P>
311: <P>
312: In the PCRE documentation the word "newline" is used to mean "the character or
313: pair of characters that indicate a line break". The choice of newline
314: convention affects the handling of the dot, circumflex, and dollar
315: metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
316: recognized line ending sequence, the match position advancement for a
317: non-anchored pattern. There is more detail about this in the
318: <a href="#execoptions">section on <b>pcre_exec()</b> options</a>
319: below.
320: </P>
321: <P>
322: The choice of newline convention does not affect the interpretation of
323: the \n or \r escape sequences, nor does it affect what \R matches, which is
324: controlled in a similar way, but by separate options.
325: </P>
326: <br><a name="SEC6" href="#TOC1">MULTITHREADING</a><br>
327: <P>
328: The PCRE functions can be used in multi-threading applications, with the
329: proviso that the memory management functions pointed to by <b>pcre_malloc</b>,
330: <b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the
331: callout function pointed to by <b>pcre_callout</b>, are shared by all threads.
332: </P>
333: <P>
334: The compiled form of a regular expression is not altered during matching, so
335: the same compiled pattern can safely be used by several threads at once.
336: </P>
337: <P>
338: If the just-in-time optimization feature is being used, it needs separate
339: memory stack areas for each thread. See the
340: <a href="pcrejit.html"><b>pcrejit</b></a>
341: documentation for more details.
342: </P>
343: <br><a name="SEC7" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br>
344: <P>
345: The compiled form of a regular expression can be saved and re-used at a later
346: time, possibly by a different program, and even on a host other than the one on
347: which it was compiled. Details are given in the
348: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
349: documentation. However, compiling a regular expression with one version of PCRE
350: for use with a different version is not guaranteed to work and may cause
351: crashes.
352: </P>
353: <br><a name="SEC8" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
354: <P>
355: <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
356: </P>
357: <P>
358: The function <b>pcre_config()</b> makes it possible for a PCRE client to
359: discover which optional features have been compiled into the PCRE library. The
360: <a href="pcrebuild.html"><b>pcrebuild</b></a>
361: documentation has more details about these optional features.
362: </P>
363: <P>
364: The first argument for <b>pcre_config()</b> is an integer, specifying which
365: information is required; the second argument is a pointer to a variable into
366: which the information is placed. The following information is available:
367: <pre>
368: PCRE_CONFIG_UTF8
369: </pre>
370: The output is an integer that is set to one if UTF-8 support is available;
371: otherwise it is set to zero.
372: <pre>
373: PCRE_CONFIG_UNICODE_PROPERTIES
374: </pre>
375: The output is an integer that is set to one if support for Unicode character
376: properties is available; otherwise it is set to zero.
377: <pre>
378: PCRE_CONFIG_JIT
379: </pre>
380: The output is an integer that is set to one if support for just-in-time
381: compiling is available; otherwise it is set to zero.
382: <pre>
383: PCRE_CONFIG_NEWLINE
384: </pre>
385: The output is an integer whose value specifies the default character sequence
386: that is recognized as meaning "newline". The four values that are supported
387: are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
388: Though they are derived from ASCII, the same values are returned in EBCDIC
389: environments. The default should normally correspond to the standard sequence
390: for your operating system.
391: <pre>
392: PCRE_CONFIG_BSR
393: </pre>
394: The output is an integer whose value indicates what character sequences the \R
395: escape sequence matches by default. A value of 0 means that \R matches any
396: Unicode line ending sequence; a value of 1 means that \R matches only CR, LF,
397: or CRLF. The default can be overridden when a pattern is compiled or matched.
398: <pre>
399: PCRE_CONFIG_LINK_SIZE
400: </pre>
401: The output is an integer that contains the number of bytes used for internal
402: linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
403: allow larger regular expressions to be compiled, at the expense of slower
404: matching. The default value of 2 is sufficient for all but the most massive
405: patterns, since it allows the compiled pattern to be up to 64K in size.
406: <pre>
407: PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
408: </pre>
409: The output is an integer that contains the threshold above which the POSIX
410: interface uses <b>malloc()</b> for output vectors. Further details are given in
411: the
412: <a href="pcreposix.html"><b>pcreposix</b></a>
413: documentation.
414: <pre>
415: PCRE_CONFIG_MATCH_LIMIT
416: </pre>
417: The output is a long integer that gives the default limit for the number of
418: internal matching function calls in a <b>pcre_exec()</b> execution. Further
419: details are given with <b>pcre_exec()</b> below.
420: <pre>
421: PCRE_CONFIG_MATCH_LIMIT_RECURSION
422: </pre>
423: The output is a long integer that gives the default limit for the depth of
424: recursion when calling the internal matching function in a <b>pcre_exec()</b>
425: execution. Further details are given with <b>pcre_exec()</b> below.
426: <pre>
427: PCRE_CONFIG_STACKRECURSE
428: </pre>
429: The output is an integer that is set to one if internal recursion when running
430: <b>pcre_exec()</b> is implemented by recursive function calls that use the stack
431: to remember their state. This is the usual way that PCRE is compiled. The
432: output is zero if PCRE was compiled to use blocks of data on the heap instead
433: of recursive function calls. In this case, <b>pcre_stack_malloc</b> and
434: <b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus
435: avoiding the use of the stack.
436: </P>
437: <br><a name="SEC9" href="#TOC1">COMPILING A PATTERN</a><br>
438: <P>
439: <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
440: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
441: <b>const unsigned char *<i>tableptr</i>);</b>
442: <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
443: <b>int *<i>errorcodeptr</i>,</b>
444: <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
445: <b>const unsigned char *<i>tableptr</i>);</b>
446: </P>
447: <P>
448: Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be
449: called to compile a pattern into an internal form. The only difference between
450: the two interfaces is that <b>pcre_compile2()</b> has an additional argument,
451: <i>errorcodeptr</i>, via which a numerical error code can be returned. To avoid
452: too much repetition, we refer just to <b>pcre_compile()</b> below, but the
453: information applies equally to <b>pcre_compile2()</b>.
454: </P>
455: <P>
456: The pattern is a C string terminated by a binary zero, and is passed in the
457: <i>pattern</i> argument. A pointer to a single block of memory that is obtained
458: via <b>pcre_malloc</b> is returned. This contains the compiled code and related
459: data. The <b>pcre</b> type is defined for the returned block; this is a typedef
460: for a structure whose contents are not externally defined. It is up to the
461: caller to free the memory (via <b>pcre_free</b>) when it is no longer required.
462: </P>
463: <P>
464: Although the compiled code of a PCRE regex is relocatable, that is, it does not
465: depend on memory location, the complete <b>pcre</b> data block is not
466: fully relocatable, because it may contain a copy of the <i>tableptr</i>
467: argument, which is an address (see below).
468: </P>
469: <P>
470: The <i>options</i> argument contains various bit settings that affect the
471: compilation. It should be zero if no options are required. The available
472: options are described below. Some of them (in particular, those that are
473: compatible with Perl, but some others as well) can also be set and unset from
474: within the pattern (see the detailed description in the
475: <a href="pcrepattern.html"><b>pcrepattern</b></a>
476: documentation). For those options that can be different in different parts of
477: the pattern, the contents of the <i>options</i> argument specifies their
478: settings at the start of compilation and execution. The PCRE_ANCHORED,
479: PCRE_BSR_<i>xxx</i>, PCRE_NEWLINE_<i>xxx</i>, PCRE_NO_UTF8_CHECK, and
480: PCRE_NO_START_OPT options can be set at the time of matching as well as at
481: compile time.
482: </P>
483: <P>
484: If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately.
485: Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns
486: NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual
487: error message. This is a static string that is part of the library. You must
488: not try to free it. Normally, the offset from the start of the pattern to the
489: byte that was being processed when the error was discovered is placed in the
490: variable pointed to by <i>erroffset</i>, which must not be NULL (if it is, an
491: immediate error is given). However, for an invalid UTF-8 string, the offset is
492: that of the first byte of the failing character. Also, some errors are not
493: detected until checks are carried out when the whole pattern has been scanned;
494: in these cases the offset passed back is the length of the pattern.
495: </P>
496: <P>
497: Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
498: sometimes point into the middle of a UTF-8 character.
499: </P>
500: <P>
501: If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
502: <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
503: returned via this argument in the event of an error. This is in addition to the
504: textual error message. Error codes and messages are listed below.
505: </P>
506: <P>
507: If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
508: character tables that are built when PCRE is compiled, using the default C
509: locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
510: call to <b>pcre_maketables()</b>. This value is stored with the compiled
511: pattern, and used again by <b>pcre_exec()</b>, unless another table pointer is
512: passed to it. For more discussion, see the section on locale support below.
513: </P>
514: <P>
515: This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
516: <pre>
517: pcre *re;
518: const char *error;
519: int erroffset;
520: re = pcre_compile(
521: "^A.*Z", /* the pattern */
522: 0, /* default options */
523: &error, /* for error message */
524: &erroffset, /* for error offset */
525: NULL); /* use default character tables */
526: </pre>
527: The following names for option bits are defined in the <b>pcre.h</b> header
528: file:
529: <pre>
530: PCRE_ANCHORED
531: </pre>
532: If this bit is set, the pattern is forced to be "anchored", that is, it is
533: constrained to match only at the first matching point in the string that is
534: being searched (the "subject string"). This effect can also be achieved by
535: appropriate constructs in the pattern itself, which is the only way to do it in
536: Perl.
537: <pre>
538: PCRE_AUTO_CALLOUT
539: </pre>
540: If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
541: all with number 255, before each pattern item. For discussion of the callout
542: facility, see the
543: <a href="pcrecallout.html"><b>pcrecallout</b></a>
544: documentation.
545: <pre>
546: PCRE_BSR_ANYCRLF
547: PCRE_BSR_UNICODE
548: </pre>
549: These options (which are mutually exclusive) control what the \R escape
550: sequence matches. The choice is either to match only CR, LF, or CRLF, or to
551: match any Unicode newline sequence. The default is specified when PCRE is
552: built. It can be overridden from within the pattern, or by setting an option
553: when a compiled pattern is matched.
554: <pre>
555: PCRE_CASELESS
556: </pre>
557: If this bit is set, letters in the pattern match both upper and lower case
558: letters. It is equivalent to Perl's /i option, and it can be changed within a
559: pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
560: concept of case for characters whose values are less than 128, so caseless
561: matching is always possible. For characters with higher values, the concept of
562: case is supported if PCRE is compiled with Unicode property support, but not
563: otherwise. If you want to use caseless matching for characters 128 and above,
564: you must ensure that PCRE is compiled with Unicode property support as well as
565: with UTF-8 support.
566: <pre>
567: PCRE_DOLLAR_ENDONLY
568: </pre>
569: If this bit is set, a dollar metacharacter in the pattern matches only at the
570: end of the subject string. Without this option, a dollar also matches
571: immediately before a newline at the end of the string (but not before any other
572: newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
573: There is no equivalent to this option in Perl, and no way to set it within a
574: pattern.
575: <pre>
576: PCRE_DOTALL
577: </pre>
578: If this bit is set, a dot metacharacter in the pattern matches a character of
579: any value, including one that indicates a newline. However, it only ever
580: matches one character, even if newlines are coded as CRLF. Without this option,
581: a dot does not match when the current position is at a newline. This option is
582: equivalent to Perl's /s option, and it can be changed within a pattern by a
583: (?s) option setting. A negative class such as [^a] always matches newline
584: characters, independent of the setting of this option.
585: <pre>
586: PCRE_DUPNAMES
587: </pre>
588: If this bit is set, names used to identify capturing subpatterns need not be
589: unique. This can be helpful for certain types of pattern when it is known that
590: only one instance of the named subpattern can ever be matched. There are more
591: details of named subpatterns below; see also the
592: <a href="pcrepattern.html"><b>pcrepattern</b></a>
593: documentation.
594: <pre>
595: PCRE_EXTENDED
596: </pre>
597: If this bit is set, whitespace data characters in the pattern are totally
598: ignored except when escaped or inside a character class. Whitespace does not
599: include the VT character (code 11). In addition, characters between an
600: unescaped # outside a character class and the next newline, inclusive, are also
601: ignored. This is equivalent to Perl's /x option, and it can be changed within a
602: pattern by a (?x) option setting.
603: </P>
604: <P>
605: Which characters are interpreted as newlines is controlled by the options
606: passed to <b>pcre_compile()</b> or by a special sequence at the start of the
607: pattern, as described in the section entitled
608: <a href="pcrepattern.html#newlines">"Newline conventions"</a>
609: in the <b>pcrepattern</b> documentation. Note that the end of this type of
610: comment is a literal newline sequence in the pattern; escape sequences that
611: happen to represent a newline do not count.
612: </P>
613: <P>
614: This option makes it possible to include comments inside complicated patterns.
615: Note, however, that this applies only to data characters. Whitespace characters
616: may never appear within special character sequences in a pattern, for example
617: within the sequence (?( that introduces a conditional subpattern.
618: <pre>
619: PCRE_EXTRA
620: </pre>
621: This option was invented in order to turn on additional functionality of PCRE
622: that is incompatible with Perl, but it is currently of very little use. When
623: set, any backslash in a pattern that is followed by a letter that has no
624: special meaning causes an error, thus reserving these combinations for future
625: expansion. By default, as in Perl, a backslash followed by a letter with no
626: special meaning is treated as a literal. (Perl can, however, be persuaded to
627: give an error for this, by running it with the -w option.) There are at present
628: no other features controlled by this option. It can also be set by a (?X)
629: option setting within a pattern.
630: <pre>
631: PCRE_FIRSTLINE
632: </pre>
633: If this option is set, an unanchored pattern is required to match before or at
634: the first newline in the subject string, though the matched text may continue
635: over the newline.
636: <pre>
637: PCRE_JAVASCRIPT_COMPAT
638: </pre>
639: If this option is set, PCRE's behaviour is changed in some ways so that it is
640: compatible with JavaScript rather than Perl. The changes are as follows:
641: </P>
642: <P>
643: (1) A lone closing square bracket in a pattern causes a compile-time error,
644: because this is illegal in JavaScript (by default it is treated as a data
645: character). Thus, the pattern AB]CD becomes illegal when this option is set.
646: </P>
647: <P>
648: (2) At run time, a back reference to an unset subpattern group matches an empty
649: string (by default this causes the current matching alternative to fail). A
650: pattern such as (\1)(a) succeeds when this option is set (assuming it can find
651: an "a" in the subject), whereas it fails by default, for Perl compatibility.
652: </P>
653: <P>
654: (3) \U matches an upper case "U" character; by default \U causes a compile
655: time error (Perl uses \U to upper case subsequent characters).
656: </P>
657: <P>
658: (4) \u matches a lower case "u" character unless it is followed by four
659: hexadecimal digits, in which case the hexadecimal number defines the code point
660: to match. By default, \u causes a compile time error (Perl uses it to upper
661: case the following character).
662: </P>
663: <P>
664: (5) \x matches a lower case "x" character unless it is followed by two
665: hexadecimal digits, in which case the hexadecimal number defines the code point
666: to match. By default, as in Perl, a hexadecimal number is always expected after
667: \x, but it may have zero, one, or two digits (so, for example, \xz matches a
668: binary zero character followed by z).
669: <pre>
670: PCRE_MULTILINE
671: </pre>
672: By default, PCRE treats the subject string as consisting of a single line of
673: characters (even if it actually contains newlines). The "start of line"
674: metacharacter (^) matches only at the start of the string, while the "end of
675: line" metacharacter ($) matches only at the end of the string, or before a
676: terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
677: Perl.
678: </P>
679: <P>
680: When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
681: match immediately following or immediately before internal newlines in the
682: subject string, respectively, as well as at the very start and end. This is
683: equivalent to Perl's /m option, and it can be changed within a pattern by a
684: (?m) option setting. If there are no newlines in a subject string, or no
685: occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
686: <pre>
687: PCRE_NEWLINE_CR
688: PCRE_NEWLINE_LF
689: PCRE_NEWLINE_CRLF
690: PCRE_NEWLINE_ANYCRLF
691: PCRE_NEWLINE_ANY
692: </pre>
693: These options override the default newline definition that was chosen when PCRE
694: was built. Setting the first or the second specifies that a newline is
695: indicated by a single character (CR or LF, respectively). Setting
696: PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
697: CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
698: preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
699: that any Unicode newline sequence should be recognized. The Unicode newline
700: sequences are the three just mentioned, plus the single characters VT (vertical
701: tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
702: separator, U+2028), and PS (paragraph separator, U+2029). The last two are
703: recognized only in UTF-8 mode.
704: </P>
705: <P>
706: The newline setting in the options word uses three bits that are treated
707: as a number, giving eight possibilities. Currently only six are used (default
708: plus the five values above). This means that if you set more than one newline
709: option, the combination may or may not be sensible. For example,
710: PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
711: other combinations may yield unused numbers and cause an error.
712: </P>
713: <P>
714: The only time that a line break in a pattern is specially recognized when
715: compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
716: and so are ignored in this mode. Also, an unescaped # outside a character class
717: indicates a comment that lasts until after the next line break sequence. In
718: other circumstances, line break sequences in patterns are treated as literal
719: data.
720: </P>
721: <P>
722: The newline option that is set at compile time becomes the default that is used
723: for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden.
724: <pre>
725: PCRE_NO_AUTO_CAPTURE
726: </pre>
727: If this option is set, it disables the use of numbered capturing parentheses in
728: the pattern. Any opening parenthesis that is not followed by ? behaves as if it
729: were followed by ?: but named parentheses can still be used for capturing (and
730: they acquire numbers in the usual way). There is no equivalent of this option
731: in Perl.
732: <pre>
733: NO_START_OPTIMIZE
734: </pre>
735: This is an option that acts at matching time; that is, it is really an option
736: for <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. If it is set at compile time,
737: it is remembered with the compiled pattern and assumed at matching time. For
738: details see the discussion of PCRE_NO_START_OPTIMIZE
739: <a href="#execoptions">below.</a>
740: <pre>
741: PCRE_UCP
742: </pre>
743: This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W,
744: \w, and some of the POSIX character classes. By default, only ASCII characters
745: are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
746: classify characters. More details are given in the section on
747: <a href="pcre.html#genericchartypes">generic character types</a>
748: in the
749: <a href="pcrepattern.html"><b>pcrepattern</b></a>
750: page. If you set PCRE_UCP, matching one of the items it affects takes much
751: longer. The option is available only if PCRE has been compiled with Unicode
752: property support.
753: <pre>
754: PCRE_UNGREEDY
755: </pre>
756: This option inverts the "greediness" of the quantifiers so that they are not
757: greedy by default, but become greedy if followed by "?". It is not compatible
758: with Perl. It can also be set by a (?U) option setting within the pattern.
759: <pre>
760: PCRE_UTF8
761: </pre>
762: This option causes PCRE to regard both the pattern and the subject as strings
763: of UTF-8 characters instead of single-byte character strings. However, it is
764: available only when PCRE is built to include UTF-8 support. If not, the use
765: of this option provokes an error. Details of how this option changes the
766: behaviour of PCRE are given in the
767: <a href="pcreunicode.html"><b>pcreunicode</b></a>
768: page.
769: <pre>
770: PCRE_NO_UTF8_CHECK
771: </pre>
772: When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
773: automatically checked. There is a discussion about the
774: <a href="pcre.html#utf8strings">validity of UTF-8 strings</a>
775: in the main
776: <a href="pcre.html"><b>pcre</b></a>
777: page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_compile()</b>
778: returns an error. If you already know that your pattern is valid, and you want
779: to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
780: option. When it is set, the effect of passing an invalid UTF-8 string as a
781: pattern is undefined. It may cause your program to crash. Note that this option
782: can also be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress
783: the UTF-8 validity checking of subject strings.
784: </P>
785: <br><a name="SEC10" href="#TOC1">COMPILATION ERROR CODES</a><br>
786: <P>
787: The following table lists the error codes than may be returned by
788: <b>pcre_compile2()</b>, along with the error messages that may be returned by
789: both compiling functions. As PCRE has developed, some error codes have fallen
790: out of use. To avoid confusion, they have not been re-used.
791: <pre>
792: 0 no error
793: 1 \ at end of pattern
794: 2 \c at end of pattern
795: 3 unrecognized character follows \
796: 4 numbers out of order in {} quantifier
797: 5 number too big in {} quantifier
798: 6 missing terminating ] for character class
799: 7 invalid escape sequence in character class
800: 8 range out of order in character class
801: 9 nothing to repeat
802: 10 [this code is not in use]
803: 11 internal error: unexpected repeat
804: 12 unrecognized character after (? or (?-
805: 13 POSIX named classes are supported only within a class
806: 14 missing )
807: 15 reference to non-existent subpattern
808: 16 erroffset passed as NULL
809: 17 unknown option bit(s) set
810: 18 missing ) after comment
811: 19 [this code is not in use]
812: 20 regular expression is too large
813: 21 failed to get memory
814: 22 unmatched parentheses
815: 23 internal error: code overflow
816: 24 unrecognized character after (?<
817: 25 lookbehind assertion is not fixed length
818: 26 malformed number or name after (?(
819: 27 conditional group contains more than two branches
820: 28 assertion expected after (?(
821: 29 (?R or (?[+-]digits must be followed by )
822: 30 unknown POSIX class name
823: 31 POSIX collating elements are not supported
824: 32 this version of PCRE is not compiled with PCRE_UTF8 support
825: 33 [this code is not in use]
826: 34 character value in \x{...} sequence is too large
827: 35 invalid condition (?(0)
828: 36 \C not allowed in lookbehind assertion
829: 37 PCRE does not support \L, \l, \N{name}, \U, or \u
830: 38 number after (?C is > 255
831: 39 closing ) for (?C expected
832: 40 recursive call could loop indefinitely
833: 41 unrecognized character after (?P
834: 42 syntax error in subpattern name (missing terminator)
835: 43 two named subpatterns have the same name
836: 44 invalid UTF-8 string
837: 45 support for \P, \p, and \X has not been compiled
838: 46 malformed \P or \p sequence
839: 47 unknown property name after \P or \p
840: 48 subpattern name is too long (maximum 32 characters)
841: 49 too many named subpatterns (maximum 10000)
842: 50 [this code is not in use]
843: 51 octal value is greater than \377 (not in UTF-8 mode)
844: 52 internal error: overran compiling workspace
845: 53 internal error: previously-checked referenced subpattern
846: not found
847: 54 DEFINE group contains more than one branch
848: 55 repeating a DEFINE group is not allowed
849: 56 inconsistent NEWLINE options
850: 57 \g is not followed by a braced, angle-bracketed, or quoted
851: name/number or by a plain number
852: 58 a numbered reference must not be zero
853: 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
854: 60 (*VERB) not recognized
855: 61 number is too big
856: 62 subpattern name expected
857: 63 digit expected after (?+
858: 64 ] is an invalid data character in JavaScript compatibility mode
859: 65 different names for subpatterns of the same number are
860: not allowed
861: 66 (*MARK) must have an argument
862: 67 this version of PCRE is not compiled with PCRE_UCP support
863: 68 \c must be followed by an ASCII character
864: 69 \k is not followed by a braced, angle-bracketed, or quoted name
865: </pre>
866: The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
867: be used if the limits were changed when PCRE was built.
868: <a name="studyingapattern"></a></P>
869: <br><a name="SEC11" href="#TOC1">STUDYING A PATTERN</a><br>
870: <P>
871: <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i></b>
872: <b>const char **<i>errptr</i>);</b>
873: </P>
874: <P>
875: If a compiled pattern is going to be used several times, it is worth spending
876: more time analyzing it in order to speed up the time taken for matching. The
877: function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
878: argument. If studying the pattern produces additional information that will
879: help speed up matching, <b>pcre_study()</b> returns a pointer to a
880: <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
881: results of the study.
882: </P>
883: <P>
884: The returned value from <b>pcre_study()</b> can be passed directly to
885: <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. However, a <b>pcre_extra</b> block
886: also contains other fields that can be set by the caller before the block is
887: passed; these are described
888: <a href="#extradata">below</a>
889: in the section on matching a pattern.
890: </P>
891: <P>
892: If studying the pattern does not produce any useful information,
893: <b>pcre_study()</b> returns NULL. In that circumstance, if the calling program
894: wants to pass any of the other fields to <b>pcre_exec()</b> or
895: <b>pcre_dfa_exec()</b>, it must set up its own <b>pcre_extra</b> block.
896: </P>
897: <P>
898: The second argument of <b>pcre_study()</b> contains option bits. There is only
899: one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-time
900: compiler is available, the pattern is further compiled into machine code that
901: executes much faster than the <b>pcre_exec()</b> matching function. If
902: the just-in-time compiler is not available, this option is ignored. All other
903: bits in the <i>options</i> argument must be zero.
904: </P>
905: <P>
906: JIT compilation is a heavyweight optimization. It can take some time for
907: patterns to be analyzed, and for one-off matches and simple patterns the
908: benefit of faster execution might be offset by a much slower study time.
909: Not all patterns can be optimized by the JIT compiler. For those that cannot be
910: handled, matching automatically falls back to the <b>pcre_exec()</b>
911: interpreter. For more details, see the
912: <a href="pcrejit.html"><b>pcrejit</b></a>
913: documentation.
914: </P>
915: <P>
916: The third argument for <b>pcre_study()</b> is a pointer for an error message. If
917: studying succeeds (even if no data is returned), the variable it points to is
918: set to NULL. Otherwise it is set to point to a textual error message. This is a
919: static string that is part of the library. You must not try to free it. You
920: should test the error pointer for NULL after calling <b>pcre_study()</b>, to be
921: sure that it has run successfully.
922: </P>
923: <P>
924: When you are finished with a pattern, you can free the memory used for the
925: study data by calling <b>pcre_free_study()</b>. This function was added to the
926: API for release 8.20. For earlier versions, the memory could be freed with
927: <b>pcre_free()</b>, just like the pattern itself. This will still work in cases
928: where PCRE_STUDY_JIT_COMPILE is not used, but it is advisable to change to the
929: new function when convenient.
930: </P>
931: <P>
932: This is a typical way in which <b>pcre_study</b>() is used (except that in a
933: real application there should be tests for errors):
934: <pre>
935: int rc;
936: pcre *re;
937: pcre_extra *sd;
938: re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
939: sd = pcre_study(
940: re, /* result of pcre_compile() */
941: 0, /* no options */
942: &error); /* set to NULL or points to a message */
943: rc = pcre_exec( /* see below for details of pcre_exec() options */
944: re, sd, "subject", 7, 0, 0, ovector, 30);
945: ...
946: pcre_free_study(sd);
947: pcre_free(re);
948: </pre>
949: Studying a pattern does two things: first, a lower bound for the length of
950: subject string that is needed to match the pattern is computed. This does not
951: mean that there are any strings of that length that match, but it does
952: guarantee that no shorter strings match. The value is used by
953: <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b> to avoid wasting time by trying to
954: match strings that are shorter than the lower bound. You can find out the value
955: in a calling program via the <b>pcre_fullinfo()</b> function.
956: </P>
957: <P>
958: Studying a pattern is also useful for non-anchored patterns that do not have a
959: single fixed starting character. A bitmap of possible starting bytes is
960: created. This speeds up finding a position in the subject at which to start
961: matching.
962: </P>
963: <P>
964: These two optimizations apply to both <b>pcre_exec()</b> and
965: <b>pcre_dfa_exec()</b>. However, they are not used by <b>pcre_exec()</b> if
966: <b>pcre_study()</b> is called with the PCRE_STUDY_JIT_COMPILE option, and
967: just-in-time compiling is successful. The optimizations can be disabled by
968: setting the PCRE_NO_START_OPTIMIZE option when calling <b>pcre_exec()</b> or
969: <b>pcre_dfa_exec()</b>. You might want to do this if your pattern contains
970: callouts or (*MARK) (which cannot be handled by the JIT compiler), and you want
971: to make use of these facilities in cases where matching fails. See the
972: discussion of PCRE_NO_START_OPTIMIZE
973: <a href="#execoptions">below.</a>
974: <a name="localesupport"></a></P>
975: <br><a name="SEC12" href="#TOC1">LOCALE SUPPORT</a><br>
976: <P>
977: PCRE handles caseless matching, and determines whether characters are letters,
978: digits, or whatever, by reference to a set of tables, indexed by character
979: value. When running in UTF-8 mode, this applies only to characters with codes
980: less than 128. By default, higher-valued codes never match escapes such as \w
981: or \d, but they can be tested with \p if PCRE is built with Unicode character
982: property support. Alternatively, the PCRE_UCP option can be set at compile
983: time; this causes \w and friends to use Unicode property support instead of
984: built-in tables. The use of locales with Unicode is discouraged. If you are
985: handling characters with codes greater than 128, you should either use UTF-8
986: and Unicode, or use locales, but not try to mix the two.
987: </P>
988: <P>
989: PCRE contains an internal set of tables that are used when the final argument
990: of <b>pcre_compile()</b> is NULL. These are sufficient for many applications.
991: Normally, the internal tables recognize only ASCII characters. However, when
992: PCRE is built, it is possible to cause the internal tables to be rebuilt in the
993: default "C" locale of the local system, which may cause them to be different.
994: </P>
995: <P>
996: The internal tables can always be overridden by tables supplied by the
997: application that calls PCRE. These may be created in a different locale from
998: the default. As more and more applications change to using Unicode, the need
999: for this locale support is expected to die away.
1000: </P>
1001: <P>
1002: External tables are built by calling the <b>pcre_maketables()</b> function,
1003: which has no arguments, in the relevant locale. The result can then be passed
1004: to <b>pcre_compile()</b> or <b>pcre_exec()</b> as often as necessary. For
1005: example, to build and use tables that are appropriate for the French locale
1006: (where accented characters with values greater than 128 are treated as letters),
1007: the following code could be used:
1008: <pre>
1009: setlocale(LC_CTYPE, "fr_FR");
1010: tables = pcre_maketables();
1011: re = pcre_compile(..., tables);
1012: </pre>
1013: The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
1014: are using Windows, the name for the French locale is "french".
1015: </P>
1016: <P>
1017: When <b>pcre_maketables()</b> runs, the tables are built in memory that is
1018: obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
1019: that the memory containing the tables remains available for as long as it is
1020: needed.
1021: </P>
1022: <P>
1023: The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
1024: pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
1025: and normally also by <b>pcre_exec()</b>. Thus, by default, for any single
1026: pattern, compilation, studying and matching all happen in the same locale, but
1027: different patterns can be compiled in different locales.
1028: </P>
1029: <P>
1030: It is possible to pass a table pointer or NULL (indicating the use of the
1031: internal tables) to <b>pcre_exec()</b>. Although not intended for this purpose,
1032: this facility could be used to match a pattern in a different locale from the
1033: one in which it was compiled. Passing table pointers at run time is discussed
1034: below in the section on matching a pattern.
1035: <a name="infoaboutpattern"></a></P>
1036: <br><a name="SEC13" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
1037: <P>
1038: <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1039: <b>int <i>what</i>, void *<i>where</i>);</b>
1040: </P>
1041: <P>
1042: The <b>pcre_fullinfo()</b> function returns information about a compiled
1043: pattern. It replaces the obsolete <b>pcre_info()</b> function, which is
1044: nevertheless retained for backwards compability (and is documented below).
1045: </P>
1046: <P>
1047: The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled
1048: pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if
1049: the pattern was not studied. The third argument specifies which piece of
1050: information is required, and the fourth argument is a pointer to a variable
1051: to receive the data. The yield of the function is zero for success, or one of
1052: the following negative numbers:
1053: <pre>
1054: PCRE_ERROR_NULL the argument <i>code</i> was NULL
1055: the argument <i>where</i> was NULL
1056: PCRE_ERROR_BADMAGIC the "magic number" was not found
1057: PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid
1058: </pre>
1059: The "magic number" is placed at the start of each compiled pattern as an simple
1060: check against passing an arbitrary memory pointer. Here is a typical call of
1061: <b>pcre_fullinfo()</b>, to obtain the length of the compiled pattern:
1062: <pre>
1063: int rc;
1064: size_t length;
1065: rc = pcre_fullinfo(
1066: re, /* result of pcre_compile() */
1067: sd, /* result of pcre_study(), or NULL */
1068: PCRE_INFO_SIZE, /* what is required */
1069: &length); /* where to put the data */
1070: </pre>
1071: The possible values for the third argument are defined in <b>pcre.h</b>, and are
1072: as follows:
1073: <pre>
1074: PCRE_INFO_BACKREFMAX
1075: </pre>
1076: Return the number of the highest back reference in the pattern. The fourth
1077: argument should point to an <b>int</b> variable. Zero is returned if there are
1078: no back references.
1079: <pre>
1080: PCRE_INFO_CAPTURECOUNT
1081: </pre>
1082: Return the number of capturing subpatterns in the pattern. The fourth argument
1083: should point to an <b>int</b> variable.
1084: <pre>
1085: PCRE_INFO_DEFAULT_TABLES
1086: </pre>
1087: Return a pointer to the internal default character tables within PCRE. The
1088: fourth argument should point to an <b>unsigned char *</b> variable. This
1089: information call is provided for internal use by the <b>pcre_study()</b>
1090: function. External callers can cause PCRE to use its internal tables by passing
1091: a NULL table pointer.
1092: <pre>
1093: PCRE_INFO_FIRSTBYTE
1094: </pre>
1095: Return information about the first byte of any matched string, for a
1096: non-anchored pattern. The fourth argument should point to an <b>int</b>
1097: variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
1098: still recognized for backwards compatibility.)
1099: </P>
1100: <P>
1101: If there is a fixed first byte, for example, from a pattern such as
1102: (cat|cow|coyote), its value is returned. Otherwise, if either
1103: <br>
1104: <br>
1105: (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1106: starts with "^", or
1107: <br>
1108: <br>
1109: (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1110: (if it were set, the pattern would be anchored),
1111: <br>
1112: <br>
1113: -1 is returned, indicating that the pattern matches only at the start of a
1114: subject string or after any newline within the string. Otherwise -2 is
1115: returned. For anchored patterns, -2 is returned.
1116: <pre>
1117: PCRE_INFO_FIRSTTABLE
1118: </pre>
1119: If the pattern was studied, and this resulted in the construction of a 256-bit
1120: table indicating a fixed set of bytes for the first byte in any matching
1121: string, a pointer to the table is returned. Otherwise NULL is returned. The
1122: fourth argument should point to an <b>unsigned char *</b> variable.
1123: <pre>
1124: PCRE_INFO_HASCRORLF
1125: </pre>
1126: Return 1 if the pattern contains any explicit matches for CR or LF characters,
1127: otherwise 0. The fourth argument should point to an <b>int</b> variable. An
1128: explicit match is either a literal CR or LF character, or \r or \n.
1129: <pre>
1130: PCRE_INFO_JCHANGED
1131: </pre>
1132: Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1133: 0. The fourth argument should point to an <b>int</b> variable. (?J) and
1134: (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1135: <pre>
1136: PCRE_INFO_JIT
1137: </pre>
1138: Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE option, and
1139: just-in-time compiling was successful. The fourth argument should point to an
1140: <b>int</b> variable. A return value of 0 means that JIT support is not available
1141: in this version of PCRE, or that the pattern was not studied with the
1142: PCRE_STUDY_JIT_COMPILE option, or that the JIT compiler could not handle this
1143: particular pattern. See the
1144: <a href="pcrejit.html"><b>pcrejit</b></a>
1145: documentation for details of what can and cannot be handled.
1146: <pre>
1147: PCRE_INFO_JITSIZE
1148: </pre>
1149: If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1150: return the size of the JIT compiled code, otherwise return zero. The fourth
1151: argument should point to a <b>size_t</b> variable.
1152: <pre>
1153: PCRE_INFO_LASTLITERAL
1154: </pre>
1155: Return the value of the rightmost literal byte that must exist in any matched
1156: string, other than at its start, if such a byte has been recorded. The fourth
1157: argument should point to an <b>int</b> variable. If there is no such byte, -1 is
1158: returned. For anchored patterns, a last literal byte is recorded only if it
1159: follows something of variable length. For example, for the pattern
1160: /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
1161: is -1.
1162: <pre>
1163: PCRE_INFO_MINLENGTH
1164: </pre>
1165: If the pattern was studied and a minimum length for matching subject strings
1166: was computed, its value is returned. Otherwise the returned value is -1. The
1167: value is a number of characters, not bytes (this may be relevant in UTF-8
1168: mode). The fourth argument should point to an <b>int</b> variable. A
1169: non-negative value is a lower bound to the length of any matching string. There
1170: may not be any strings of that length that do actually match, but every string
1171: that does match is at least that long.
1172: <pre>
1173: PCRE_INFO_NAMECOUNT
1174: PCRE_INFO_NAMEENTRYSIZE
1175: PCRE_INFO_NAMETABLE
1176: </pre>
1177: PCRE supports the use of named as well as numbered capturing parentheses. The
1178: names are just an additional way of identifying the parentheses, which still
1179: acquire numbers. Several convenience functions such as
1180: <b>pcre_get_named_substring()</b> are provided for extracting captured
1181: substrings by name. It is also possible to extract the data directly, by first
1182: converting the name to a number in order to access the correct pointers in the
1183: output vector (described with <b>pcre_exec()</b> below). To do the conversion,
1184: you need to use the name-to-number map, which is described by these three
1185: values.
1186: </P>
1187: <P>
1188: The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1189: the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1190: entry; both of these return an <b>int</b> value. The entry size depends on the
1191: length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1192: entry of the table (a pointer to <b>char</b>). The first two bytes of each entry
1193: are the number of the capturing parenthesis, most significant byte first. The
1194: rest of the entry is the corresponding name, zero terminated.
1195: </P>
1196: <P>
1197: The names are in alphabetical order. Duplicate names may appear if (?| is used
1198: to create multiple groups with the same number, as described in the
1199: <a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
1200: in the
1201: <a href="pcrepattern.html"><b>pcrepattern</b></a>
1202: page. Duplicate names for subpatterns with different numbers are permitted only
1203: if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1204: table in the order in which they were found in the pattern. In the absence of
1205: (?| this is the order of increasing number; when (?| is used this is not
1206: necessarily the case because later subpatterns may have lower numbers.
1207: </P>
1208: <P>
1209: As a simple example of the name/number table, consider the following pattern
1210: (assume PCRE_EXTENDED is set, so white space - including newlines - is
1211: ignored):
1212: <pre>
1213: (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) )
1214: </pre>
1215: There are four named subpatterns, so the table has four entries, and each entry
1216: in the table is eight bytes long. The table is as follows, with non-printing
1217: bytes shows in hexadecimal, and undefined bytes shown as ??:
1218: <pre>
1219: 00 01 d a t e 00 ??
1220: 00 05 d a y 00 ?? ??
1221: 00 04 m o n t h 00
1222: 00 02 y e a r 00 ??
1223: </pre>
1224: When writing code to extract data from named subpatterns using the
1225: name-to-number map, remember that the length of the entries is likely to be
1226: different for each compiled pattern.
1227: <pre>
1228: PCRE_INFO_OKPARTIAL
1229: </pre>
1230: Return 1 if the pattern can be used for partial matching with
1231: <b>pcre_exec()</b>, otherwise 0. The fourth argument should point to an
1232: <b>int</b> variable. From release 8.00, this always returns 1, because the
1233: restrictions that previously applied to partial matching have been lifted. The
1234: <a href="pcrepartial.html"><b>pcrepartial</b></a>
1235: documentation gives details of partial matching.
1236: <pre>
1237: PCRE_INFO_OPTIONS
1238: </pre>
1239: Return a copy of the options with which the pattern was compiled. The fourth
1240: argument should point to an <b>unsigned long int</b> variable. These option bits
1241: are those specified in the call to <b>pcre_compile()</b>, modified by any
1242: top-level option settings at the start of the pattern itself. In other words,
1243: they are the options that will be in force when matching starts. For example,
1244: if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1245: result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1246: </P>
1247: <P>
1248: A pattern is automatically anchored by PCRE if all of its top-level
1249: alternatives begin with one of the following:
1250: <pre>
1251: ^ unless PCRE_MULTILINE is set
1252: \A always
1253: \G always
1254: .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
1255: </pre>
1256: For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1257: <b>pcre_fullinfo()</b>.
1258: <pre>
1259: PCRE_INFO_SIZE
1260: </pre>
1261: Return the size of the compiled pattern. The fourth argument should point to a
1262: <b>size_t</b> variable. This value does not include the size of the <b>pcre</b>
1263: structure that is returned by <b>pcre_compile()</b>. The value that is passed as
1264: the argument to <b>pcre_malloc()</b> when <b>pcre_compile()</b> is getting memory
1265: in which to place the compiled data is the value returned by this option plus
1266: the size of the <b>pcre</b> structure. Studying a compiled pattern, with or
1267: without JIT, does not alter the value returned by this option.
1268: <pre>
1269: PCRE_INFO_STUDYSIZE
1270: </pre>
1271: Return the size of the data block pointed to by the <i>study_data</i> field in a
1272: <b>pcre_extra</b> block. If <b>pcre_extra</b> is NULL, or there is no study data,
1273: zero is returned. The fourth argument should point to a <b>size_t</b> variable.
1274: The <i>study_data</i> field is set by <b>pcre_study()</b> to record information
1275: that will speed up matching (see the section entitled
1276: <a href="#studyingapattern">"Studying a pattern"</a>
1277: above). The format of the <i>study_data</i> block is private, but its length
1278: is made available via this option so that it can be saved and restored (see the
1279: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1280: documentation for details).
1281: </P>
1282: <br><a name="SEC14" href="#TOC1">OBSOLETE INFO FUNCTION</a><br>
1283: <P>
1284: <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
1285: <b>*<i>firstcharptr</i>);</b>
1286: </P>
1287: <P>
1288: The <b>pcre_info()</b> function is now obsolete because its interface is too
1289: restrictive to return all the available data about a compiled pattern. New
1290: programs should use <b>pcre_fullinfo()</b> instead. The yield of
1291: <b>pcre_info()</b> is the number of capturing subpatterns, or one of the
1292: following negative numbers:
1293: <pre>
1294: PCRE_ERROR_NULL the argument <i>code</i> was NULL
1295: PCRE_ERROR_BADMAGIC the "magic number" was not found
1296: </pre>
1297: If the <i>optptr</i> argument is not NULL, a copy of the options with which the
1298: pattern was compiled is placed in the integer it points to (see
1299: PCRE_INFO_OPTIONS above).
1300: </P>
1301: <P>
1302: If the pattern is not anchored and the <i>firstcharptr</i> argument is not NULL,
1303: it is used to pass back information about the first character of any matched
1304: string (see PCRE_INFO_FIRSTBYTE above).
1305: </P>
1306: <br><a name="SEC15" href="#TOC1">REFERENCE COUNTS</a><br>
1307: <P>
1308: <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
1309: </P>
1310: <P>
1311: The <b>pcre_refcount()</b> function is used to maintain a reference count in the
1312: data block that contains a compiled pattern. It is provided for the benefit of
1313: applications that operate in an object-oriented manner, where different parts
1314: of the application may be using the same compiled pattern, but you want to free
1315: the block when they are all done.
1316: </P>
1317: <P>
1318: When a pattern is compiled, the reference count field is initialized to zero.
1319: It is changed only by calling this function, whose action is to add the
1320: <i>adjust</i> value (which may be positive or negative) to it. The yield of the
1321: function is the new value. However, the value of the count is constrained to
1322: lie between 0 and 65535, inclusive. If the new value is outside these limits,
1323: it is forced to the appropriate limit value.
1324: </P>
1325: <P>
1326: Except when it is zero, the reference count is not correctly preserved if a
1327: pattern is compiled on one host and then transferred to a host whose byte-order
1328: is different. (This seems a highly unlikely scenario.)
1329: </P>
1330: <br><a name="SEC16" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
1331: <P>
1332: <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
1333: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
1334: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
1335: </P>
1336: <P>
1337: The function <b>pcre_exec()</b> is called to match a subject string against a
1338: compiled pattern, which is passed in the <i>code</i> argument. If the
1339: pattern was studied, the result of the study should be passed in the
1340: <i>extra</i> argument. You can call <b>pcre_exec()</b> with the same <i>code</i>
1341: and <i>extra</i> arguments as many times as you like, in order to match
1342: different subject strings with the same pattern.
1343: </P>
1344: <P>
1345: This function is the main matching facility of the library, and it operates in
1346: a Perl-like manner. For specialist use there is also an alternative matching
1347: function, which is described
1348: <a href="#dfamatch">below</a>
1349: in the section about the <b>pcre_dfa_exec()</b> function.
1350: </P>
1351: <P>
1352: In most applications, the pattern will have been compiled (and optionally
1353: studied) in the same process that calls <b>pcre_exec()</b>. However, it is
1354: possible to save compiled patterns and study data, and then use them later
1355: in different processes, possibly even on different hosts. For a discussion
1356: about this, see the
1357: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1358: documentation.
1359: </P>
1360: <P>
1361: Here is an example of a simple call to <b>pcre_exec()</b>:
1362: <pre>
1363: int rc;
1364: int ovector[30];
1365: rc = pcre_exec(
1366: re, /* result of pcre_compile() */
1367: NULL, /* we didn't study the pattern */
1368: "some string", /* the subject string */
1369: 11, /* the length of the subject string */
1370: 0, /* start at offset 0 in the subject */
1371: 0, /* default options */
1372: ovector, /* vector of integers for substring information */
1373: 30); /* number of elements (NOT size in bytes) */
1374: <a name="extradata"></a></PRE>
1375: </P>
1376: <br><b>
1377: Extra data for <b>pcre_exec()</b>
1378: </b><br>
1379: <P>
1380: If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
1381: data block. The <b>pcre_study()</b> function returns such a block (when it
1382: doesn't return NULL), but you can also create one for yourself, and pass
1383: additional information in it. The <b>pcre_extra</b> block contains the following
1384: fields (not necessarily in this order):
1385: <pre>
1386: unsigned long int <i>flags</i>;
1387: void *<i>study_data</i>;
1388: void *<i>executable_jit</i>;
1389: unsigned long int <i>match_limit</i>;
1390: unsigned long int <i>match_limit_recursion</i>;
1391: void *<i>callout_data</i>;
1392: const unsigned char *<i>tables</i>;
1393: unsigned char **<i>mark</i>;
1394: </pre>
1395: The <i>flags</i> field is a bitmap that specifies which of the other fields
1396: are set. The flag bits are:
1397: <pre>
1398: PCRE_EXTRA_STUDY_DATA
1399: PCRE_EXTRA_EXECUTABLE_JIT
1400: PCRE_EXTRA_MATCH_LIMIT
1401: PCRE_EXTRA_MATCH_LIMIT_RECURSION
1402: PCRE_EXTRA_CALLOUT_DATA
1403: PCRE_EXTRA_TABLES
1404: PCRE_EXTRA_MARK
1405: </pre>
1406: Other flag bits should be set to zero. The <i>study_data</i> field and sometimes
1407: the <i>executable_jit</i> field are set in the <b>pcre_extra</b> block that is
1408: returned by <b>pcre_study()</b>, together with the appropriate flag bits. You
1409: should not set these yourself, but you may add to the block by setting the
1410: other fields and their corresponding flag bits.
1411: </P>
1412: <P>
1413: The <i>match_limit</i> field provides a means of preventing PCRE from using up a
1414: vast amount of resources when running patterns that are not going to match,
1415: but which have a very large number of possibilities in their search trees. The
1416: classic example is a pattern that uses nested unlimited repeats.
1417: </P>
1418: <P>
1419: Internally, <b>pcre_exec()</b> uses a function called <b>match()</b>, which it
1420: calls repeatedly (sometimes recursively). The limit set by <i>match_limit</i> is
1421: imposed on the number of times this function is called during a match, which
1422: has the effect of limiting the amount of backtracking that can take place. For
1423: patterns that are not anchored, the count restarts from zero for each position
1424: in the subject string.
1425: </P>
1426: <P>
1427: When <b>pcre_exec()</b> is called with a pattern that was successfully studied
1428: with the PCRE_STUDY_JIT_COMPILE option, the way that the matching is executed
1429: is entirely different. However, there is still the possibility of runaway
1430: matching that goes on for a very long time, and so the <i>match_limit</i> value
1431: is also used in this case (but in a different way) to limit how long the
1432: matching can continue.
1433: </P>
1434: <P>
1435: The default value for the limit can be set when PCRE is built; the default
1436: default is 10 million, which handles all but the most extreme cases. You can
1437: override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b>
1438: block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1439: the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns
1440: PCRE_ERROR_MATCHLIMIT.
1441: </P>
1442: <P>
1443: The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but
1444: instead of limiting the total number of times that <b>match()</b> is called, it
1445: limits the depth of recursion. The recursion depth is a smaller number than the
1446: total number of calls, because not all calls to <b>match()</b> are recursive.
1447: This limit is of use only if it is set smaller than <i>match_limit</i>.
1448: </P>
1449: <P>
1450: Limiting the recursion depth limits the amount of machine stack that can be
1451: used, or, when PCRE has been compiled to use memory on the heap instead of the
1452: stack, the amount of heap memory that can be used. This limit is not relevant,
1453: and is ignored, if the pattern was successfully studied with
1454: PCRE_STUDY_JIT_COMPILE.
1455: </P>
1456: <P>
1457: The default value for <i>match_limit_recursion</i> can be set when PCRE is
1458: built; the default default is the same value as the default for
1459: <i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b>
1460: with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and
1461: PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit
1462: is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT.
1463: </P>
1464: <P>
1465: The <i>callout_data</i> field is used in conjunction with the "callout" feature,
1466: and is described in the
1467: <a href="pcrecallout.html"><b>pcrecallout</b></a>
1468: documentation.
1469: </P>
1470: <P>
1471: The <i>tables</i> field is used to pass a character tables pointer to
1472: <b>pcre_exec()</b>; this overrides the value that is stored with the compiled
1473: pattern. A non-NULL value is stored with the compiled pattern only if custom
1474: tables were supplied to <b>pcre_compile()</b> via its <i>tableptr</i> argument.
1475: If NULL is passed to <b>pcre_exec()</b> using this mechanism, it forces PCRE's
1476: internal tables to be used. This facility is helpful when re-using patterns
1477: that have been saved after compiling with an external set of tables, because
1478: the external tables might be at a different address when <b>pcre_exec()</b> is
1479: called. See the
1480: <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
1481: documentation for a discussion of saving compiled patterns for later use.
1482: </P>
1483: <P>
1484: If PCRE_EXTRA_MARK is set in the <i>flags</i> field, the <i>mark</i> field must
1485: be set to point to a <b>char *</b> variable. If the pattern contains any
1486: backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1487: a name to pass back, a pointer to the name string (zero terminated) is placed
1488: in the variable pointed to by the <i>mark</i> field. The names are within the
1489: compiled pattern; if you wish to retain such a name you must copy it before
1490: freeing the memory of a compiled pattern. If there is no name to pass back, the
1491: variable pointed to by the <i>mark</i> field set to NULL. For details of the
1492: backtracking control verbs, see the section entitled
1493: <a href="pcrepattern#backtrackcontrol">"Backtracking control"</a>
1494: in the
1495: <a href="pcrepattern.html"><b>pcrepattern</b></a>
1496: documentation.
1497: <a name="execoptions"></a></P>
1498: <br><b>
1499: Option bits for <b>pcre_exec()</b>
1500: </b><br>
1501: <P>
1502: The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
1503: zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
1504: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1505: PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1506: PCRE_PARTIAL_HARD.
1507: </P>
1508: <P>
1509: If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1510: the only supported options for JIT execution are PCRE_NO_UTF8_CHECK,
1511: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NOTEMPTY_ATSTART. Note in
1512: particular that partial matching is not supported. If an unsupported option is
1513: used, JIT execution is disabled and the normal interpretive code in
1514: <b>pcre_exec()</b> is run.
1515: <pre>
1516: PCRE_ANCHORED
1517: </pre>
1518: The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
1519: matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1520: to be anchored by virtue of its contents, it cannot be made unachored at
1521: matching time.
1522: <pre>
1523: PCRE_BSR_ANYCRLF
1524: PCRE_BSR_UNICODE
1525: </pre>
1526: These options (which are mutually exclusive) control what the \R escape
1527: sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1528: match any Unicode newline sequence. These options override the choice that was
1529: made or defaulted when the pattern was compiled.
1530: <pre>
1531: PCRE_NEWLINE_CR
1532: PCRE_NEWLINE_LF
1533: PCRE_NEWLINE_CRLF
1534: PCRE_NEWLINE_ANYCRLF
1535: PCRE_NEWLINE_ANY
1536: </pre>
1537: These options override the newline definition that was chosen or defaulted when
1538: the pattern was compiled. For details, see the description of
1539: <b>pcre_compile()</b> above. During matching, the newline choice affects the
1540: behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1541: the way the match position is advanced after a match failure for an unanchored
1542: pattern.
1543: </P>
1544: <P>
1545: When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1546: match attempt for an unanchored pattern fails when the current position is at a
1547: CRLF sequence, and the pattern contains no explicit matches for CR or LF
1548: characters, the match position is advanced by two characters instead of one, in
1549: other words, to after the CRLF.
1550: </P>
1551: <P>
1552: The above rule is a compromise that makes the most common cases work as
1553: expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1554: set), it does not match the string "\r\nA" because, after failing at the
1555: start, it skips both the CR and the LF before retrying. However, the pattern
1556: [\r\n]A does match that string, because it contains an explicit CR or LF
1557: reference, and so advances only by one character after the first failure.
1558: </P>
1559: <P>
1560: An explicit match for CR of LF is either a literal appearance of one of those
1561: characters, or one of the \r or \n escape sequences. Implicit matches such as
1562: [^X] do not count, nor does \s (which includes CR and LF in the characters
1563: that it matches).
1564: </P>
1565: <P>
1566: Notwithstanding the above, anomalous effects may still occur when CRLF is a
1567: valid newline sequence and explicit \r or \n escapes appear in the pattern.
1568: <pre>
1569: PCRE_NOTBOL
1570: </pre>
1571: This option specifies that first character of the subject string is not the
1572: beginning of a line, so the circumflex metacharacter should not match before
1573: it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1574: never to match. This option affects only the behaviour of the circumflex
1575: metacharacter. It does not affect \A.
1576: <pre>
1577: PCRE_NOTEOL
1578: </pre>
1579: This option specifies that the end of the subject string is not the end of a
1580: line, so the dollar metacharacter should not match it nor (except in multiline
1581: mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1582: compile time) causes dollar never to match. This option affects only the
1583: behaviour of the dollar metacharacter. It does not affect \Z or \z.
1584: <pre>
1585: PCRE_NOTEMPTY
1586: </pre>
1587: An empty string is not considered to be a valid match if this option is set. If
1588: there are alternatives in the pattern, they are tried. If all the alternatives
1589: match the empty string, the entire match fails. For example, if the pattern
1590: <pre>
1591: a?b?
1592: </pre>
1593: is applied to a string not beginning with "a" or "b", it matches an empty
1594: string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1595: valid, so PCRE searches further into the string for occurrences of "a" or "b".
1596: <pre>
1597: PCRE_NOTEMPTY_ATSTART
1598: </pre>
1599: This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1600: the start of the subject is permitted. If the pattern is anchored, such a match
1601: can occur only if the pattern contains \K.
1602: </P>
1603: <P>
1604: Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1605: does make a special case of a pattern match of the empty string within its
1606: <b>split()</b> function, and when using the /g modifier. It is possible to
1607: emulate Perl's behaviour after matching a null string by first trying the match
1608: again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1609: if that fails, by advancing the starting offset (see below) and trying an
1610: ordinary match again. There is some code that demonstrates how to do this in
1611: the
1612: <a href="pcredemo.html"><b>pcredemo</b></a>
1613: sample program. In the most general case, you have to check to see if the
1614: newline convention recognizes CRLF as a newline, and if so, and the current
1615: character is CR followed by LF, advance the starting offset by two characters
1616: instead of one.
1617: <pre>
1618: PCRE_NO_START_OPTIMIZE
1619: </pre>
1620: There are a number of optimizations that <b>pcre_exec()</b> uses at the start of
1621: a match, in order to speed up the process. For example, if it is known that an
1622: unanchored match must start with a specific character, it searches the subject
1623: for that character, and fails immediately if it cannot find it, without
1624: actually running the main matching function. This means that a special item
1625: such as (*COMMIT) at the start of a pattern is not considered until after a
1626: suitable starting point for the match has been found. When callouts or (*MARK)
1627: items are in use, these "start-up" optimizations can cause them to be skipped
1628: if the pattern is never actually used. The start-up optimizations are in effect
1629: a pre-scan of the subject that takes place before the pattern is run.
1630: </P>
1631: <P>
1632: The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1633: causing performance to suffer, but ensuring that in cases where the result is
1634: "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1635: are considered at every possible starting position in the subject string. If
1636: PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1637: time.
1638: </P>
1639: <P>
1640: Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1641: Consider the pattern
1642: <pre>
1643: (*COMMIT)ABC
1644: </pre>
1645: When this is compiled, PCRE records the fact that a match must start with the
1646: character "A". Suppose the subject string is "DEFABC". The start-up
1647: optimization scans along the subject, finds "A" and runs the first match
1648: attempt from there. The (*COMMIT) item means that the pattern must match the
1649: current starting position, which in this case, it does. However, if the same
1650: match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1651: subject string does not happen. The first match attempt is run starting from
1652: "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1653: the overall result is "no match". If the pattern is studied, more start-up
1654: optimizations may be used. For example, a minimum length for the subject may be
1655: recorded. Consider the pattern
1656: <pre>
1657: (*MARK:A)(X|Y)
1658: </pre>
1659: The minimum length for a match is one character. If the subject is "ABC", there
1660: will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1661: If the pattern is studied, the final attempt does not take place, because PCRE
1662: knows that the subject is too short, and so the (*MARK) is never encountered.
1663: In this case, studying the pattern does not affect the overall match result,
1664: which is still "no match", but it does affect the auxiliary information that is
1665: returned.
1666: <pre>
1667: PCRE_NO_UTF8_CHECK
1668: </pre>
1669: When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1670: string is automatically checked when <b>pcre_exec()</b> is subsequently called.
1671: The value of <i>startoffset</i> is also checked to ensure that it points to the
1672: start of a UTF-8 character. There is a discussion about the validity of UTF-8
1673: strings in the
1674: <a href="pcre.html#utf8strings">section on UTF-8 support</a>
1675: in the main
1676: <a href="pcre.html"><b>pcre</b></a>
1677: page. If an invalid UTF-8 sequence of bytes is found, <b>pcre_exec()</b> returns
1678: the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
1679: a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
1680: both cases, information about the precise nature of the error may also be
1681: returned (see the descriptions of these errors in the section entitled \fIError
1682: return values from\fP <b>pcre_exec()</b>
1683: <a href="#errorlist">below).</a>
1684: If <i>startoffset</i> contains a value that does not point to the start of a
1685: UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1686: returned.
1687: </P>
1688: <P>
1689: If you already know that your subject is valid, and you want to skip these
1690: checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1691: calling <b>pcre_exec()</b>. You might want to do this for the second and
1692: subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find
1693: all the matches in a single subject string. However, you should be sure that
1694: the value of <i>startoffset</i> points to the start of a UTF-8 character (or the
1695: end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1696: invalid UTF-8 string as a subject or an invalid value of <i>startoffset</i> is
1697: undefined. Your program may crash.
1698: <pre>
1699: PCRE_PARTIAL_HARD
1700: PCRE_PARTIAL_SOFT
1701: </pre>
1702: These options turn on the partial matching feature. For backwards
1703: compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1704: occurs if the end of the subject string is reached successfully, but there are
1705: not enough subject characters to complete the match. If this happens when
1706: PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1707: testing any remaining alternatives. Only if no complete match can be found is
1708: PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1709: PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1710: but only if no complete match can be found.
1711: </P>
1712: <P>
1713: If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1714: partial match is found, <b>pcre_exec()</b> immediately returns
1715: PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1716: when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1717: important that an alternative complete match.
1718: </P>
1719: <P>
1720: In both cases, the portion of the string that was inspected when the partial
1721: match was found is set as the first matching string. There is a more detailed
1722: discussion of partial and multi-segment matching, with examples, in the
1723: <a href="pcrepartial.html"><b>pcrepartial</b></a>
1724: documentation.
1725: </P>
1726: <br><b>
1727: The string to be matched by <b>pcre_exec()</b>
1728: </b><br>
1729: <P>
1730: The subject string is passed to <b>pcre_exec()</b> as a pointer in
1731: <i>subject</i>, a length (in bytes) in <i>length</i>, and a starting byte offset
1732: in <i>startoffset</i>. If this is negative or greater than the length of the
1733: subject, <b>pcre_exec()</b> returns PCRE_ERROR_BADOFFSET. When the starting
1734: offset is zero, the search for a match starts at the beginning of the subject,
1735: and this is by far the most common case. In UTF-8 mode, the byte offset must
1736: point to the start of a UTF-8 character (or the end of the subject). Unlike the
1737: pattern string, the subject may contain binary zero bytes.
1738: </P>
1739: <P>
1740: A non-zero starting offset is useful when searching for another match in the
1741: same subject by calling <b>pcre_exec()</b> again after a previous success.
1742: Setting <i>startoffset</i> differs from just passing over a shortened string and
1743: setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1744: lookbehind. For example, consider the pattern
1745: <pre>
1746: \Biss\B
1747: </pre>
1748: which finds occurrences of "iss" in the middle of words. (\B matches only if
1749: the current position in the subject is not a word boundary.) When applied to
1750: the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
1751: occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the
1752: subject, namely "issipi", it does not match, because \B is always false at the
1753: start of the subject, which is deemed to be a word boundary. However, if
1754: <b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i>
1755: set to 4, it finds the second occurrence of "iss" because it is able to look
1756: behind the starting point to discover that it is preceded by a letter.
1757: </P>
1758: <P>
1759: Finding all the matches in a subject is tricky when the pattern can match an
1760: empty string. It is possible to emulate Perl's /g behaviour by first trying the
1761: match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1762: PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1763: and trying an ordinary match again. There is some code that demonstrates how to
1764: do this in the
1765: <a href="pcredemo.html"><b>pcredemo</b></a>
1766: sample program. In the most general case, you have to check to see if the
1767: newline convention recognizes CRLF as a newline, and if so, and the current
1768: character is CR followed by LF, advance the starting offset by two characters
1769: instead of one.
1770: </P>
1771: <P>
1772: If a non-zero starting offset is passed when the pattern is anchored, one
1773: attempt to match at the given offset is made. This can only succeed if the
1774: pattern does not require the match to be at the start of the subject.
1775: </P>
1776: <br><b>
1777: How <b>pcre_exec()</b> returns captured substrings
1778: </b><br>
1779: <P>
1780: In general, a pattern matches a certain portion of the subject, and in
1781: addition, further substrings from the subject may be picked out by parts of the
1782: pattern. Following the usage in Jeffrey Friedl's book, this is called
1783: "capturing" in what follows, and the phrase "capturing subpattern" is used for
1784: a fragment of a pattern that picks out a substring. PCRE supports several other
1785: kinds of parenthesized subpattern that do not cause substrings to be captured.
1786: </P>
1787: <P>
1788: Captured substrings are returned to the caller via a vector of integers whose
1789: address is passed in <i>ovector</i>. The number of elements in the vector is
1790: passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>: this
1791: argument is NOT the size of <i>ovector</i> in bytes.
1792: </P>
1793: <P>
1794: The first two-thirds of the vector is used to pass back captured substrings,
1795: each substring using a pair of integers. The remaining third of the vector is
1796: used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
1797: and is not available for passing back information. The number passed in
1798: <i>ovecsize</i> should always be a multiple of three. If it is not, it is
1799: rounded down.
1800: </P>
1801: <P>
1802: When a match is successful, information about captured substrings is returned
1803: in pairs of integers, starting at the beginning of <i>ovector</i>, and
1804: continuing up to two-thirds of its length at the most. The first element of
1805: each pair is set to the byte offset of the first character in a substring, and
1806: the second is set to the byte offset of the first character after the end of a
1807: substring. <b>Note</b>: these values are always byte offsets, even in UTF-8
1808: mode. They are not character counts.
1809: </P>
1810: <P>
1811: The first pair of integers, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the
1812: portion of the subject string matched by the entire pattern. The next pair is
1813: used for the first capturing subpattern, and so on. The value returned by
1814: <b>pcre_exec()</b> is one more than the highest numbered pair that has been set.
1815: For example, if two substrings have been captured, the returned value is 3. If
1816: there are no capturing subpatterns, the return value from a successful match is
1817: 1, indicating that just the first pair of offsets has been set.
1818: </P>
1819: <P>
1820: If a capturing subpattern is matched repeatedly, it is the last portion of the
1821: string that it matched that is returned.
1822: </P>
1823: <P>
1824: If the vector is too small to hold all the captured substring offsets, it is
1825: used as far as possible (up to two-thirds of its length), and the function
1826: returns a value of zero. If neither the actual string matched not any captured
1827: substrings are of interest, <b>pcre_exec()</b> may be called with <i>ovector</i>
1828: passed as NULL and <i>ovecsize</i> as zero. However, if the pattern contains
1829: back references and the <i>ovector</i> is not big enough to remember the related
1830: substrings, PCRE has to get additional memory for use during matching. Thus it
1831: is usually advisable to supply an <i>ovector</i> of reasonable size.
1832: </P>
1833: <P>
1834: There are some cases where zero is returned (indicating vector overflow) when
1835: in fact the vector is exactly the right size for the final match. For example,
1836: consider the pattern
1837: <pre>
1838: (a)(?:(b)c|bd)
1839: </pre>
1840: If a vector of 6 elements (allowing for only 1 captured substring) is given
1841: with subject string "abd", <b>pcre_exec()</b> will try to set the second
1842: captured string, thereby recording a vector overflow, before failing to match
1843: "c" and backing up to try the second alternative. The zero return, however,
1844: does correctly indicate that the maximum number of slots (namely 2) have been
1845: filled. In similar cases where there is temporary overflow, but the final
1846: number of used slots is actually less than the maximum, a non-zero value is
1847: returned.
1848: </P>
1849: <P>
1850: The <b>pcre_fullinfo()</b> function can be used to find out how many capturing
1851: subpatterns there are in a compiled pattern. The smallest size for
1852: <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
1853: the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
1854: </P>
1855: <P>
1856: It is possible for capturing subpattern number <i>n+1</i> to match some part of
1857: the subject when subpattern <i>n</i> has not been used at all. For example, if
1858: the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1859: function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1860: happens, both values in the offset pairs corresponding to unused subpatterns
1861: are set to -1.
1862: </P>
1863: <P>
1864: Offset values that correspond to unused subpatterns at the end of the
1865: expression are also set to -1. For example, if the string "abc" is matched
1866: against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1867: return from the function is 2, because the highest used capturing subpattern
1868: number is 1, and the offsets for for the second and third capturing subpatterns
1869: (assuming the vector is large enough, of course) are set to -1.
1870: </P>
1871: <P>
1872: <b>Note</b>: Elements in the first two-thirds of <i>ovector</i> that do not
1873: correspond to capturing parentheses in the pattern are never changed. That is,
1874: if a pattern contains <i>n</i> capturing parentheses, no more than
1875: <i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by <b>pcre_exec()</b>. The other
1876: elements (in the first two-thirds) retain whatever values they previously had.
1877: </P>
1878: <P>
1879: Some convenience functions are provided for extracting the captured substrings
1880: as separate strings. These are described below.
1881: <a name="errorlist"></a></P>
1882: <br><b>
1883: Error return values from <b>pcre_exec()</b>
1884: </b><br>
1885: <P>
1886: If <b>pcre_exec()</b> fails, it returns a negative number. The following are
1887: defined in the header file:
1888: <pre>
1889: PCRE_ERROR_NOMATCH (-1)
1890: </pre>
1891: The subject string did not match the pattern.
1892: <pre>
1893: PCRE_ERROR_NULL (-2)
1894: </pre>
1895: Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
1896: NULL and <i>ovecsize</i> was not zero.
1897: <pre>
1898: PCRE_ERROR_BADOPTION (-3)
1899: </pre>
1900: An unrecognized bit was set in the <i>options</i> argument.
1901: <pre>
1902: PCRE_ERROR_BADMAGIC (-4)
1903: </pre>
1904: PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1905: the case when it is passed a junk pointer and to detect when a pattern that was
1906: compiled in an environment of one endianness is run in an environment with the
1907: other endianness. This is the error that PCRE gives when the magic number is
1908: not present.
1909: <pre>
1910: PCRE_ERROR_UNKNOWN_OPCODE (-5)
1911: </pre>
1912: While running the pattern match, an unknown item was encountered in the
1913: compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1914: of the compiled pattern.
1915: <pre>
1916: PCRE_ERROR_NOMEMORY (-6)
1917: </pre>
1918: If a pattern contains back references, but the <i>ovector</i> that is passed to
1919: <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
1920: gets a block of memory at the start of matching to use for this purpose. If the
1921: call via <b>pcre_malloc()</b> fails, this error is given. The memory is
1922: automatically freed at the end of matching.
1923: </P>
1924: <P>
1925: This error is also given if <b>pcre_stack_malloc()</b> fails in
1926: <b>pcre_exec()</b>. This can happen only when PCRE has been compiled with
1927: <b>--disable-stack-for-recursion</b>.
1928: <pre>
1929: PCRE_ERROR_NOSUBSTRING (-7)
1930: </pre>
1931: This error is used by the <b>pcre_copy_substring()</b>,
1932: <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
1933: below). It is never returned by <b>pcre_exec()</b>.
1934: <pre>
1935: PCRE_ERROR_MATCHLIMIT (-8)
1936: </pre>
1937: The backtracking limit, as specified by the <i>match_limit</i> field in a
1938: <b>pcre_extra</b> structure (or defaulted) was reached. See the description
1939: above.
1940: <pre>
1941: PCRE_ERROR_CALLOUT (-9)
1942: </pre>
1943: This error is never generated by <b>pcre_exec()</b> itself. It is provided for
1944: use by callout functions that want to yield a distinctive error code. See the
1945: <a href="pcrecallout.html"><b>pcrecallout</b></a>
1946: documentation for details.
1947: <pre>
1948: PCRE_ERROR_BADUTF8 (-10)
1949: </pre>
1950: A string that contains an invalid UTF-8 byte sequence was passed as a subject,
1951: and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
1952: (<i>ovecsize</i>) is at least 2, the byte offset to the start of the the invalid
1953: UTF-8 character is placed in the first element, and a reason code is placed in
1954: the second element. The reason codes are listed in the
1955: <a href="#badutf8reasons">following section.</a>
1956: For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
1957: truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
1958: PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
1959: <pre>
1960: PCRE_ERROR_BADUTF8_OFFSET (-11)
1961: </pre>
1962: The UTF-8 byte sequence that was passed as a subject was checked and found to
1963: be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
1964: <i>startoffset</i> did not point to the beginning of a UTF-8 character or the
1965: end of the subject.
1966: <pre>
1967: PCRE_ERROR_PARTIAL (-12)
1968: </pre>
1969: The subject string did not match, but it did match partially. See the
1970: <a href="pcrepartial.html"><b>pcrepartial</b></a>
1971: documentation for details of partial matching.
1972: <pre>
1973: PCRE_ERROR_BADPARTIAL (-13)
1974: </pre>
1975: This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1976: option was used with a compiled pattern containing items that were not
1977: supported for partial matching. From release 8.00 onwards, there are no
1978: restrictions on partial matching.
1979: <pre>
1980: PCRE_ERROR_INTERNAL (-14)
1981: </pre>
1982: An unexpected internal error has occurred. This error could be caused by a bug
1983: in PCRE or by overwriting of the compiled pattern.
1984: <pre>
1985: PCRE_ERROR_BADCOUNT (-15)
1986: </pre>
1987: This error is given if the value of the <i>ovecsize</i> argument is negative.
1988: <pre>
1989: PCRE_ERROR_RECURSIONLIMIT (-21)
1990: </pre>
1991: The internal recursion limit, as specified by the <i>match_limit_recursion</i>
1992: field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
1993: description above.
1994: <pre>
1995: PCRE_ERROR_BADNEWLINE (-23)
1996: </pre>
1997: An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given.
1998: <pre>
1999: PCRE_ERROR_BADOFFSET (-24)
2000: </pre>
2001: The value of <i>startoffset</i> was negative or greater than the length of the
2002: subject, that is, the value in <i>length</i>.
2003: <pre>
2004: PCRE_ERROR_SHORTUTF8 (-25)
2005: </pre>
2006: This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2007: ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2008: Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2009: fact sufficient to detect this case, but this special error code for
2010: PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2011: retained for backwards compatibility.
2012: <pre>
2013: PCRE_ERROR_RECURSELOOP (-26)
2014: </pre>
2015: This error is returned when <b>pcre_exec()</b> detects a recursion loop within
2016: the pattern. Specifically, it means that either the whole pattern or a
2017: subpattern has been called recursively for the second time at the same position
2018: in the subject string. Some simple patterns that might do this are detected and
2019: faulted at compile time, but more complicated cases, in particular mutual
2020: recursions between two different subpatterns, cannot be detected until run
2021: time.
2022: <pre>
2023: PCRE_ERROR_JIT_STACKLIMIT (-27)
2024: </pre>
2025: This error is returned when a pattern that was successfully studied using the
2026: PCRE_STUDY_JIT_COMPILE option is being matched, but the memory available for
2027: the just-in-time processing stack is not large enough. See the
2028: <a href="pcrejit.html"><b>pcrejit</b></a>
2029: documentation for more details.
2030: </P>
2031: <P>
2032: Error numbers -16 to -20 and -22 are not used by <b>pcre_exec()</b>.
2033: <a name="badutf8reasons"></a></P>
2034: <br><b>
2035: Reason codes for invalid UTF-8 strings
2036: </b><br>
2037: <P>
2038: When <b>pcre_exec()</b> returns either PCRE_ERROR_BADUTF8 or
2039: PCRE_ERROR_SHORTUTF8, and the size of the output vector (<i>ovecsize</i>) is at
2040: least 2, the offset of the start of the invalid UTF-8 character is placed in
2041: the first output vector element (<i>ovector[0]</i>) and a reason code is placed
2042: in the second element (<i>ovector[1]</i>). The reason codes are given names in
2043: the <b>pcre.h</b> header file:
2044: <pre>
2045: PCRE_UTF8_ERR1
2046: PCRE_UTF8_ERR2
2047: PCRE_UTF8_ERR3
2048: PCRE_UTF8_ERR4
2049: PCRE_UTF8_ERR5
2050: </pre>
2051: The string ends with a truncated UTF-8 character; the code specifies how many
2052: bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2053: no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2054: allows for up to 6 bytes, and this is checked first; hence the possibility of
2055: 4 or 5 missing bytes.
2056: <pre>
2057: PCRE_UTF8_ERR6
2058: PCRE_UTF8_ERR7
2059: PCRE_UTF8_ERR8
2060: PCRE_UTF8_ERR9
2061: PCRE_UTF8_ERR10
2062: </pre>
2063: The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2064: character do not have the binary value 0b10 (that is, either the most
2065: significant bit is 0, or the next bit is 1).
2066: <pre>
2067: PCRE_UTF8_ERR11
2068: PCRE_UTF8_ERR12
2069: </pre>
2070: A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2071: these code points are excluded by RFC 3629.
2072: <pre>
2073: PCRE_UTF8_ERR13
2074: </pre>
2075: A 4-byte character has a value greater than 0x10fff; these code points are
2076: excluded by RFC 3629.
2077: <pre>
2078: PCRE_UTF8_ERR14
2079: </pre>
2080: A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2081: code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2082: from UTF-8.
2083: <pre>
2084: PCRE_UTF8_ERR15
2085: PCRE_UTF8_ERR16
2086: PCRE_UTF8_ERR17
2087: PCRE_UTF8_ERR18
2088: PCRE_UTF8_ERR19
2089: </pre>
2090: A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2091: value that can be represented by fewer bytes, which is invalid. For example,
2092: the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2093: one byte.
2094: <pre>
2095: PCRE_UTF8_ERR20
2096: </pre>
2097: The two most significant bits of the first byte of a character have the binary
2098: value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2099: byte can only validly occur as the second or subsequent byte of a multi-byte
2100: character.
2101: <pre>
2102: PCRE_UTF8_ERR21
2103: </pre>
2104: The first byte of a character has the value 0xfe or 0xff. These values can
2105: never occur in a valid UTF-8 string.
2106: </P>
2107: <br><a name="SEC17" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
2108: <P>
2109: <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
2110: <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
2111: <b>int <i>buffersize</i>);</b>
2112: </P>
2113: <P>
2114: <b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
2115: <b>int <i>stringcount</i>, int <i>stringnumber</i>,</b>
2116: <b>const char **<i>stringptr</i>);</b>
2117: </P>
2118: <P>
2119: <b>int pcre_get_substring_list(const char *<i>subject</i>,</b>
2120: <b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b>
2121: </P>
2122: <P>
2123: Captured substrings can be accessed directly by using the offsets returned by
2124: <b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions
2125: <b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and
2126: <b>pcre_get_substring_list()</b> are provided for extracting captured substrings
2127: as new, separate, zero-terminated strings. These functions identify substrings
2128: by number. The next section describes functions for extracting named
2129: substrings.
2130: </P>
2131: <P>
2132: A substring that contains a binary zero is correctly extracted and has a
2133: further zero added on the end, but the result is not, of course, a C string.
2134: However, you can process such a string by referring to the length that is
2135: returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>.
2136: Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate
2137: for handling strings containing binary zeros, because the end of the final
2138: string is not independently indicated.
2139: </P>
2140: <P>
2141: The first three arguments are the same for all three of these functions:
2142: <i>subject</i> is the subject string that has just been successfully matched,
2143: <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
2144: <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
2145: captured by the match, including the substring that matched the entire regular
2146: expression. This is the value returned by <b>pcre_exec()</b> if it is greater
2147: than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
2148: space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
2149: number of elements in the vector divided by three.
2150: </P>
2151: <P>
2152: The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
2153: extract a single substring, whose number is given as <i>stringnumber</i>. A
2154: value of zero extracts the substring that matched the entire pattern, whereas
2155: higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
2156: the string is placed in <i>buffer</i>, whose length is given by
2157: <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
2158: obtained via <b>pcre_malloc</b>, and its address is returned via
2159: <i>stringptr</i>. The yield of the function is the length of the string, not
2160: including the terminating zero, or one of these error codes:
2161: <pre>
2162: PCRE_ERROR_NOMEMORY (-6)
2163: </pre>
2164: The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
2165: memory failed for <b>pcre_get_substring()</b>.
2166: <pre>
2167: PCRE_ERROR_NOSUBSTRING (-7)
2168: </pre>
2169: There is no substring whose number is <i>stringnumber</i>.
2170: </P>
2171: <P>
2172: The <b>pcre_get_substring_list()</b> function extracts all available substrings
2173: and builds a list of pointers to them. All this is done in a single block of
2174: memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
2175: is returned via <i>listptr</i>, which is also the start of the list of string
2176: pointers. The end of the list is marked by a NULL pointer. The yield of the
2177: function is zero if all went well, or the error code
2178: <pre>
2179: PCRE_ERROR_NOMEMORY (-6)
2180: </pre>
2181: if the attempt to get the memory block failed.
2182: </P>
2183: <P>
2184: When any of these functions encounter a substring that is unset, which can
2185: happen when capturing subpattern number <i>n+1</i> matches some part of the
2186: subject, but subpattern <i>n</i> has not been used at all, they return an empty
2187: string. This can be distinguished from a genuine zero-length substring by
2188: inspecting the appropriate offset in <i>ovector</i>, which is negative for unset
2189: substrings.
2190: </P>
2191: <P>
2192: The two convenience functions <b>pcre_free_substring()</b> and
2193: <b>pcre_free_substring_list()</b> can be used to free the memory returned by
2194: a previous call of <b>pcre_get_substring()</b> or
2195: <b>pcre_get_substring_list()</b>, respectively. They do nothing more than call
2196: the function pointed to by <b>pcre_free</b>, which of course could be called
2197: directly from a C program. However, PCRE is used in some situations where it is
2198: linked via a special interface to another programming language that cannot use
2199: <b>pcre_free</b> directly; it is for these cases that the functions are
2200: provided.
2201: </P>
2202: <br><a name="SEC18" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
2203: <P>
2204: <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
2205: <b>const char *<i>name</i>);</b>
2206: </P>
2207: <P>
2208: <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
2209: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
2210: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
2211: <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
2212: </P>
2213: <P>
2214: <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
2215: <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
2216: <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
2217: <b>const char **<i>stringptr</i>);</b>
2218: </P>
2219: <P>
2220: To extract a substring by name, you first have to find associated number.
2221: For example, for this pattern
2222: <pre>
2223: (a+)b(?<xxx>\d+)...
2224: </pre>
2225: the number of the subpattern called "xxx" is 2. If the name is known to be
2226: unique (PCRE_DUPNAMES was not set), you can find the number from the name by
2227: calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled
2228: pattern, and the second is the name. The yield of the function is the
2229: subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2230: that name.
2231: </P>
2232: <P>
2233: Given the number, you can extract the substring directly, or use one of the
2234: functions described in the previous section. For convenience, there are also
2235: two functions that do the whole job.
2236: </P>
2237: <P>
2238: Most of the arguments of <b>pcre_copy_named_substring()</b> and
2239: <b>pcre_get_named_substring()</b> are the same as those for the similarly named
2240: functions that extract by number. As these are described in the previous
2241: section, they are not re-described here. There are just two differences:
2242: </P>
2243: <P>
2244: First, instead of a substring number, a substring name is given. Second, there
2245: is an extra argument, given at the start, which is a pointer to the compiled
2246: pattern. This is needed in order to gain access to the name-to-number
2247: translation table.
2248: </P>
2249: <P>
2250: These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they
2251: then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as
2252: appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names,
2253: the behaviour may not be what you want (see the next section).
2254: </P>
2255: <P>
2256: <b>Warning:</b> If the pattern uses the (?| feature to set up multiple
2257: subpatterns with the same number, as described in the
2258: <a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
2259: in the
2260: <a href="pcrepattern.html"><b>pcrepattern</b></a>
2261: page, you cannot use names to distinguish the different subpatterns, because
2262: names are not included in the compiled code. The matching process uses only
2263: numbers. For this reason, the use of different names for subpatterns of the
2264: same number causes an error at compile time.
2265: </P>
2266: <br><a name="SEC19" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
2267: <P>
2268: <b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b>
2269: <b>const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b>
2270: </P>
2271: <P>
2272: When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2273: are not required to be unique. (Duplicate names are always allowed for
2274: subpatterns with the same number, created by using the (?| feature. Indeed, if
2275: such subpatterns are named, they are required to use the same names.)
2276: </P>
2277: <P>
2278: Normally, patterns with duplicate names are such that in any one match, only
2279: one of the named subpatterns participates. An example is shown in the
2280: <a href="pcrepattern.html"><b>pcrepattern</b></a>
2281: documentation.
2282: </P>
2283: <P>
2284: When duplicates are present, <b>pcre_copy_named_substring()</b> and
2285: <b>pcre_get_named_substring()</b> return the first substring corresponding to
2286: the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2287: returned; no data is returned. The <b>pcre_get_stringnumber()</b> function
2288: returns one of the numbers that are associated with the name, but it is not
2289: defined which it is.
2290: </P>
2291: <P>
2292: If you want to get full details of all captured substrings for a given name,
2293: you must use the <b>pcre_get_stringtable_entries()</b> function. The first
2294: argument is the compiled pattern, and the second is the name. The third and
2295: fourth are pointers to variables which are updated by the function. After it
2296: has run, they point to the first and last entries in the name-to-number table
2297: for the given name. The function itself returns the length of each entry, or
2298: PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2299: described above in the section entitled <i>Information about a pattern</i>
2300: <a href="#infoaboutpattern">above.</a>
2301: Given all the relevant entries for the name, you can extract each of their
2302: numbers, and hence the captured data, if any.
2303: </P>
2304: <br><a name="SEC20" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
2305: <P>
2306: The traditional matching function uses a similar algorithm to Perl, which stops
2307: when it finds the first match, starting at a given point in the subject. If you
2308: want to find all possible matches, or the longest possible match, consider
2309: using the alternative matching function (see below) instead. If you cannot use
2310: the alternative function, but still need to find all possible matches, you
2311: can kludge it up by making use of the callout facility, which is described in
2312: the
2313: <a href="pcrecallout.html"><b>pcrecallout</b></a>
2314: documentation.
2315: </P>
2316: <P>
2317: What you have to do is to insert a callout right at the end of the pattern.
2318: When your callout function is called, extract and save the current matched
2319: substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
2320: other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
2321: will yield PCRE_ERROR_NOMATCH.
2322: <a name="dfamatch"></a></P>
2323: <br><a name="SEC21" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
2324: <P>
2325: <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
2326: <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
2327: <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
2328: <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
2329: </P>
2330: <P>
2331: The function <b>pcre_dfa_exec()</b> is called to match a subject string against
2332: a compiled pattern, using a matching algorithm that scans the subject string
2333: just once, and does not backtrack. This has different characteristics to the
2334: normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2335: patterns are not supported. Nevertheless, there are times when this kind of
2336: matching can be useful. For a discussion of the two matching algorithms, and a
2337: list of features that <b>pcre_dfa_exec()</b> does not support, see the
2338: <a href="pcrematching.html"><b>pcrematching</b></a>
2339: documentation.
2340: </P>
2341: <P>
2342: The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
2343: <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
2344: different way, and this is described below. The other common arguments are used
2345: in the same way as for <b>pcre_exec()</b>, so their description is not repeated
2346: here.
2347: </P>
2348: <P>
2349: The two additional arguments provide workspace for the function. The workspace
2350: vector should contain at least 20 elements. It is used for keeping track of
2351: multiple paths through the pattern tree. More workspace will be needed for
2352: patterns and subjects where there are a lot of potential matches.
2353: </P>
2354: <P>
2355: Here is an example of a simple call to <b>pcre_dfa_exec()</b>:
2356: <pre>
2357: int rc;
2358: int ovector[10];
2359: int wspace[20];
2360: rc = pcre_dfa_exec(
2361: re, /* result of pcre_compile() */
2362: NULL, /* we didn't study the pattern */
2363: "some string", /* the subject string */
2364: 11, /* the length of the subject string */
2365: 0, /* start at offset 0 in the subject */
2366: 0, /* default options */
2367: ovector, /* vector of integers for substring information */
2368: 10, /* number of elements (NOT size in bytes) */
2369: wspace, /* working space vector */
2370: 20); /* number of elements (NOT size in bytes) */
2371: </PRE>
2372: </P>
2373: <br><b>
2374: Option bits for <b>pcre_dfa_exec()</b>
2375: </b><br>
2376: <P>
2377: The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
2378: zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>,
2379: PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2380: PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2381: PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2382: All but the last four of these are exactly the same as for <b>pcre_exec()</b>,
2383: so their description is not repeated here.
2384: <pre>
2385: PCRE_PARTIAL_HARD
2386: PCRE_PARTIAL_SOFT
2387: </pre>
2388: These have the same general effect as they do for <b>pcre_exec()</b>, but the
2389: details are slightly different. When PCRE_PARTIAL_HARD is set for
2390: <b>pcre_dfa_exec()</b>, it returns PCRE_ERROR_PARTIAL if the end of the subject
2391: is reached and there is still at least one matching possibility that requires
2392: additional characters. This happens even if some complete matches have also
2393: been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2394: is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2395: there have been no complete matches, but there is still at least one matching
2396: possibility. The portion of the string that was inspected when the longest
2397: partial match was found is set as the first matching string in both cases.
2398: There is a more detailed discussion of partial and multi-segment matching, with
2399: examples, in the
2400: <a href="pcrepartial.html"><b>pcrepartial</b></a>
2401: documentation.
2402: <pre>
2403: PCRE_DFA_SHORTEST
2404: </pre>
2405: Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2406: soon as it has found one match. Because of the way the alternative algorithm
2407: works, this is necessarily the shortest possible match at the first possible
2408: matching point in the subject string.
2409: <pre>
2410: PCRE_DFA_RESTART
2411: </pre>
2412: When <b>pcre_dfa_exec()</b> returns a partial match, it is possible to call it
2413: again, with additional subject characters, and have it continue with the same
2414: match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2415: <i>workspace</i> and <i>wscount</i> options must reference the same vector as
2416: before because data about the match so far is left in them after a partial
2417: match. There is more discussion of this facility in the
2418: <a href="pcrepartial.html"><b>pcrepartial</b></a>
2419: documentation.
2420: </P>
2421: <br><b>
2422: Successful returns from <b>pcre_dfa_exec()</b>
2423: </b><br>
2424: <P>
2425: When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
2426: substring in the subject. Note, however, that all the matches from one run of
2427: the function start at the same point in the subject. The shorter matches are
2428: all initial substrings of the longer matches. For example, if the pattern
2429: <pre>
2430: <.*>
2431: </pre>
2432: is matched against the string
2433: <pre>
2434: This is <something> <something else> <something further> no more
2435: </pre>
2436: the three matched strings are
2437: <pre>
2438: <something>
2439: <something> <something else>
2440: <something> <something else> <something further>
2441: </pre>
2442: On success, the yield of the function is a number greater than zero, which is
2443: the number of matched substrings. The substrings themselves are returned in
2444: <i>ovector</i>. Each string uses two elements; the first is the offset to the
2445: start, and the second is the offset to the end. In fact, all the strings have
2446: the same start offset. (Space could have been saved by giving this only once,
2447: but it was decided to retain some compatibility with the way <b>pcre_exec()</b>
2448: returns data, even though the meaning of the strings is different.)
2449: </P>
2450: <P>
2451: The strings are returned in reverse order of length; that is, the longest
2452: matching string is given first. If there were too many matches to fit into
2453: <i>ovector</i>, the yield of the function is zero, and the vector is filled with
2454: the longest matches. Unlike <b>pcre_exec()</b>, <b>pcre_dfa_exec()</b> can use
2455: the entire <i>ovector</i> for returning matched strings.
2456: </P>
2457: <br><b>
2458: Error returns from <b>pcre_dfa_exec()</b>
2459: </b><br>
2460: <P>
2461: The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
2462: Many of the errors are the same as for <b>pcre_exec()</b>, and these are
2463: described
2464: <a href="#errorlist">above.</a>
2465: There are in addition the following errors that are specific to
2466: <b>pcre_dfa_exec()</b>:
2467: <pre>
2468: PCRE_ERROR_DFA_UITEM (-16)
2469: </pre>
2470: This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
2471: that it does not support, for instance, the use of \C or a back reference.
2472: <pre>
2473: PCRE_ERROR_DFA_UCOND (-17)
2474: </pre>
2475: This return is given if <b>pcre_dfa_exec()</b> encounters a condition item that
2476: uses a back reference for the condition, or a test for recursion in a specific
2477: group. These are not supported.
2478: <pre>
2479: PCRE_ERROR_DFA_UMLIMIT (-18)
2480: </pre>
2481: This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
2482: block that contains a setting of the <i>match_limit</i> or
2483: <i>match_limit_recursion</i> fields. This is not supported (these fields are
2484: meaningless for DFA matching).
2485: <pre>
2486: PCRE_ERROR_DFA_WSSIZE (-19)
2487: </pre>
2488: This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
2489: <i>workspace</i> vector.
2490: <pre>
2491: PCRE_ERROR_DFA_RECURSE (-20)
2492: </pre>
2493: When a recursive subpattern is processed, the matching function calls itself
2494: recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
2495: error is given if the output vector is not large enough. This should be
2496: extremely rare, as a vector of size 1000 is used.
2497: </P>
2498: <br><a name="SEC22" href="#TOC1">SEE ALSO</a><br>
2499: <P>
2500: <b>pcrebuild</b>(3), <b>pcrecallout</b>(3), <b>pcrecpp(3)</b>(3),
2501: <b>pcrematching</b>(3), <b>pcrepartial</b>(3), <b>pcreposix</b>(3),
2502: <b>pcreprecompile</b>(3), <b>pcresample</b>(3), <b>pcrestack</b>(3).
2503: </P>
2504: <br><a name="SEC23" href="#TOC1">AUTHOR</a><br>
2505: <P>
2506: Philip Hazel
2507: <br>
2508: University Computing Service
2509: <br>
2510: Cambridge CB2 3QH, England.
2511: <br>
2512: </P>
2513: <br><a name="SEC24" href="#TOC1">REVISION</a><br>
2514: <P>
2515: Last updated: 02 December 2011
2516: <br>
2517: Copyright © 1997-2011 University of Cambridge.
2518: <br>
2519: <p>
2520: Return to the <a href="index.html">PCRE index page</a>.
2521: </p>
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