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2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few differences. (Certain features that appeared in Python and         just  a few differences. Some features that appeared in Python and PCRE
23         PCRE before they appeared in Perl are also available using  the  Python         before they appeared in Perl are also available using the  Python  syn-
24         syntax.)         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25           items, and there is an option for requesting some  minor  changes  that
26         The  current  implementation of PCRE (release 7.x) corresponds approxi-         give better JavaScript compatibility.
27         mately with Perl 5.10, including support for UTF-8 encoded strings  and  
28         Unicode general category properties. However, UTF-8 and Unicode support         Starting with release 8.30, it is possible to compile two separate PCRE
29         has to be explicitly enabled; it is not the default. The Unicode tables         libraries:  the  original,  which  supports  8-bit  character   strings
30         correspond to Unicode release 5.0.0.         (including  UTF-8  strings),  and a second library that supports 16-bit
31           character strings (including UTF-16 strings). The build process  allows
32           either  one  or both to be built. The majority of the work to make this
33           possible was done by Zoltan Herczeg.
34    
35           The two libraries contain identical sets of functions, except that  the
36           names  in  the  16-bit  library start with pcre16_ instead of pcre_. To
37           avoid over-complication and reduce the documentation maintenance  load,
38           most of the documentation describes the 8-bit library, with the differ-
39           ences for the 16-bit library described separately in the  pcre16  page.
40           References  to  functions or structures of the form pcre[16]_xxx should
41           be  read  as  meaning  "pcre_xxx  when  using  the  8-bit  library  and
42           pcre16_xxx when using the 16-bit library".
43    
44           The  current implementation of PCRE corresponds approximately with Perl
45           5.12, including support for UTF-8/16 encoded strings and  Unicode  gen-
46           eral  category properties. However, UTF-8/16 and Unicode support has to
47           be explicitly enabled; it is not the default. The Unicode tables corre-
48           spond to Unicode release 6.0.0.
49    
50         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
51         alternative matching function that matches the same  compiled  patterns         alternative function that matches the same compiled patterns in a  dif-
52         in  a different way. In certain circumstances, the alternative function         ferent way. In certain circumstances, the alternative function has some
53         has some advantages. For a discussion of the two  matching  algorithms,         advantages.  For a discussion of the two matching algorithms,  see  the
54         see the pcrematching page.         pcrematching page.
55    
56         PCRE  is  written  in C and released as a C library. A number of people         PCRE  is  written  in C and released as a C library. A number of people
57         have written wrappers and interfaces of various kinds.  In  particular,         have written wrappers and interfaces of various kinds.  In  particular,
58         Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now         Google  Inc.   have  provided a comprehensive C++ wrapper for the 8-bit
59         included as part of the PCRE distribution. The pcrecpp page has details         library. This is now included as part of  the  PCRE  distribution.  The
60         of  this  interface.  Other  people's contributions can be found in the         pcrecpp  page  has  details of this interface. Other people's contribu-
61         Contrib directory at the primary FTP site, which is:         tions can be found in the Contrib directory at the  primary  FTP  site,
62           which is:
63    
64         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
65    
66         Details of exactly which Perl regular expression features are  and  are         Details  of  exactly which Perl regular expression features are and are
67         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
68         tern and pcrecompat pages. There is a syntax summary in the  pcresyntax         tern  and pcrecompat pages. There is a syntax summary in the pcresyntax
69         page.         page.
70    
71         Some  features  of  PCRE can be included, excluded, or changed when the         Some features of PCRE can be included, excluded, or  changed  when  the
72         library is built. The pcre_config() function makes it  possible  for  a         library  is  built.  The pcre_config() function makes it possible for a
73         client  to  discover  which  features are available. The features them-         client to discover which features are  available.  The  features  them-
74         selves are described in the pcrebuild page. Documentation about  build-         selves  are described in the pcrebuild page. Documentation about build-
75         ing  PCRE for various operating systems can be found in the README file         ing PCRE for various operating systems can be found in the  README  and
76         in the source distribution.         NON-UNIX-USE files in the source distribution.
77    
78         The library contains a number of undocumented  internal  functions  and         The  libraries contains a number of undocumented internal functions and
79         data  tables  that  are  used by more than one of the exported external         data tables that are used by more than one  of  the  exported  external
80         functions, but which are not intended  for  use  by  external  callers.         functions,  but  which  are  not  intended for use by external callers.
81         Their  names  all begin with "_pcre_", which hopefully will not provoke         Their names all begin with "_pcre_" or "_pcre16_", which hopefully will
82         any name clashes. In some environments, it is possible to control which         not  provoke  any name clashes. In some environments, it is possible to
83         external  symbols  are  exported when a shared library is built, and in         control which external symbols are exported when a  shared  library  is
84         these cases the undocumented symbols are not exported.         built, and in these cases the undocumented symbols are not exported.
85    
86    
87  USER DOCUMENTATION  USER DOCUMENTATION
88    
89         The user documentation for PCRE comprises a number  of  different  sec-         The  user  documentation  for PCRE comprises a number of different sec-
90         tions.  In the "man" format, each of these is a separate "man page". In         tions. In the "man" format, each of these is a separate "man page".  In
91         the HTML format, each is a separate page, linked from the  index  page.         the  HTML  format, each is a separate page, linked from the index page.
92         In  the  plain text format, all the sections are concatenated, for ease         In the plain text format, all the sections, except  the  pcredemo  sec-
93         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
94           lows:
95    
96           pcre              this document           pcre              this document
97             pcre16            details of the 16-bit library
98           pcre-config       show PCRE installation configuration information           pcre-config       show PCRE installation configuration information
99           pcreapi           details of PCRE's native C API           pcreapi           details of PCRE's native C API
100           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
101           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
102           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
103           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper for the 8-bit library
104           pcregrep          description of the pcregrep command           pcredemo          a demonstration C program that uses PCRE
105             pcregrep          description of the pcregrep command (8-bit only)
106             pcrejit           discussion of the just-in-time optimization support
107             pcrelimits        details of size and other limits
108           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
109           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
110           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
111                               regular expressions                               regular expressions
          pcresyntax        quick syntax reference  
112           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
113           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API for the 8-bit library
114           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
115           pcresample        discussion of the sample program           pcresample        discussion of the pcredemo program
116           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
117             pcresyntax        quick syntax reference
118           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
119             pcreunicode       discussion of Unicode and UTF-8/16 support
120    
121         In  addition,  in the "man" and HTML formats, there is a short page for         In addition, in the "man" and HTML formats, there is a short  page  for
122         each C library function, listing its arguments and results.         each 8-bit C library function, listing its arguments and results.
123    
124    
125  LIMITATIONS  AUTHOR
126    
127         There are some size limitations in PCRE but it is hoped that they  will         Philip Hazel
128         never in practice be relevant.         University Computing Service
129           Cambridge CB2 3QH, England.
130    
131         The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE         Putting  an actual email address here seems to have been a spam magnet,
132         is compiled with the default internal linkage size of 2. If you want to         so I've taken it away. If you want to email me, use  my  two  initials,
133         process  regular  expressions  that are truly enormous, you can compile         followed by the two digits 10, at the domain cam.ac.uk.
        PCRE with an internal linkage size of 3 or 4 (see the  README  file  in  
        the  source  distribution and the pcrebuild documentation for details).  
        In these cases the limit is substantially larger.  However,  the  speed  
        of execution is slower.  
134    
        All values in repeating quantifiers must be less than 65536.  
135    
136         There is no limit to the number of parenthesized subpatterns, but there  REVISION
        can be no more than 65535 capturing subpatterns.  
137    
138         The maximum length of name for a named subpattern is 32 characters, and         Last updated: 10 January 2012
139         the maximum number of named subpatterns is 10000.         Copyright (c) 1997-2012 University of Cambridge.
140    ------------------------------------------------------------------------------
141    
142    
143    PCRE(3)                                                                PCRE(3)
144    
        The  maximum  length of a subject string is the largest positive number  
        that an integer variable can hold. However, when using the  traditional  
        matching function, PCRE uses recursion to handle subpatterns and indef-  
        inite repetition.  This means that the available stack space may  limit  
        the size of a subject string that can be processed by certain patterns.  
        For a discussion of stack issues, see the pcrestack documentation.  
145    
146    NAME
147           PCRE - Perl-compatible regular expressions
148    
149  UTF-8 AND UNICODE PROPERTY SUPPORT         #include <pcre.h>
150    
        From release 3.3, PCRE has  had  some  support  for  character  strings  
        encoded  in the UTF-8 format. For release 4.0 this was greatly extended  
        to cover most common requirements, and in release 5.0  additional  sup-  
        port for Unicode general category properties was added.  
   
        In  order  process  UTF-8 strings, you must build PCRE to include UTF-8  
        support in the code, and, in addition,  you  must  call  pcre_compile()  
        with  the PCRE_UTF8 option flag. When you do this, both the pattern and  
        any subject strings that are matched against it are  treated  as  UTF-8  
        strings instead of just strings of bytes.  
151    
152         If  you compile PCRE with UTF-8 support, but do not use it at run time,  PCRE 16-BIT API BASIC FUNCTIONS
        the library will be a bit bigger, but the additional run time  overhead  
        is limited to testing the PCRE_UTF8 flag occasionally, so should not be  
        very big.  
153    
154         If PCRE is built with Unicode character property support (which implies         pcre16 *pcre16_compile(PCRE_SPTR16 pattern, int options,
155         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-              const char **errptr, int *erroffset,
156         ported.  The available properties that can be tested are limited to the              const unsigned char *tableptr);
157         general  category  properties such as Lu for an upper case letter or Nd  
158         for a decimal number, the Unicode script names such as Arabic  or  Han,         pcre16 *pcre16_compile2(PCRE_SPTR16 pattern, int options,
159         and  the  derived  properties  Any  and L&. A full list is given in the              int *errorcodeptr,
160         pcrepattern documentation. Only the short names for properties are sup-              const char **errptr, int *erroffset,
161         ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-              const unsigned char *tableptr);
162         ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may  
163         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE         pcre16_extra *pcre16_study(const pcre16 *code, int options,
164         does not support this.              const char **errptr);
165    
166         The following comments apply when PCRE is running in UTF-8 mode:         void pcre16_free_study(pcre16_extra *extra);
167    
168         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and         int pcre16_exec(const pcre16 *code, const pcre16_extra *extra,
169         subjects  are  checked for validity on entry to the relevant functions.              PCRE_SPTR16 subject, int length, int startoffset,
170         If an invalid UTF-8 string is passed, an error return is given. In some              int options, int *ovector, int ovecsize);
171         situations,  you  may  already  know  that  your strings are valid, and  
172         therefore want to skip these checks in order to improve performance. If         int pcre16_dfa_exec(const pcre16 *code, const pcre16_extra *extra,
173         you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,              PCRE_SPTR16 subject, int length, int startoffset,
174         PCRE assumes that the pattern or subject  it  is  given  (respectively)              int options, int *ovector, int ovecsize,
175         contains  only valid UTF-8 codes. In this case, it does not diagnose an              int *workspace, int wscount);
176         invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when  
177         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may  
178         crash.  PCRE 16-BIT API STRING EXTRACTION FUNCTIONS
179    
180         2. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a         int pcre16_copy_named_substring(const pcre16 *code,
181         two-byte UTF-8 character if the value is greater than 127.              PCRE_SPTR16 subject, int *ovector,
182                int stringcount, PCRE_SPTR16 stringname,
183         3.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8              PCRE_UCHAR16 *buffer, int buffersize);
184         characters for values greater than \177.  
185           int pcre16_copy_substring(PCRE_SPTR16 subject, int *ovector,
186         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-              int stringcount, int stringnumber, PCRE_UCHAR16 *buffer,
187         vidual bytes, for example: \x{100}{3}.              int buffersize);
188    
189         5.  The dot metacharacter matches one UTF-8 character instead of a sin-         int pcre16_get_named_substring(const pcre16 *code,
190         gle byte.              PCRE_SPTR16 subject, int *ovector,
191                int stringcount, PCRE_SPTR16 stringname,
192         6. The escape sequence \C can be used to match a single byte  in  UTF-8              PCRE_SPTR16 *stringptr);
193         mode,  but  its  use can lead to some strange effects. This facility is  
194         not available in the alternative matching function, pcre_dfa_exec().         int pcre16_get_stringnumber(const pcre16 *code,
195                PCRE_SPTR16 name);
196         7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly  
197         test  characters of any code value, but the characters that PCRE recog-         int pcre16_get_stringtable_entries(const pcre16 *code,
198         nizes as digits, spaces, or word characters  remain  the  same  set  as              PCRE_SPTR16 name, PCRE_UCHAR16 **first, PCRE_UCHAR16 **last);
199         before, all with values less than 256. This remains true even when PCRE  
200         includes Unicode property support, because to do otherwise  would  slow         int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector,
201         down  PCRE in many common cases. If you really want to test for a wider              int stringcount, int stringnumber,
202         sense of, say, "digit", you must use Unicode  property  tests  such  as              PCRE_SPTR16 *stringptr);
203         \p{Nd}.  
204           int pcre16_get_substring_list(PCRE_SPTR16 subject,
205         8.  Similarly,  characters that match the POSIX named character classes              int *ovector, int stringcount, PCRE_SPTR16 **listptr);
206         are all low-valued characters.  
207           void pcre16_free_substring(PCRE_SPTR16 stringptr);
208         9. However, the Perl 5.10 horizontal and vertical  whitespace  matching  
209         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-         void pcre16_free_substring_list(PCRE_SPTR16 *stringptr);
210         acters.  
211    
212         10. Case-insensitive matching applies only to characters  whose  values  PCRE 16-BIT API AUXILIARY FUNCTIONS
213         are  less than 128, unless PCRE is built with Unicode property support.  
214         Even when Unicode property support is available, PCRE  still  uses  its         pcre16_jit_stack *pcre16_jit_stack_alloc(int startsize, int maxsize);
215         own  character  tables when checking the case of low-valued characters,  
216         so as not to degrade performance.  The Unicode property information  is         void pcre16_jit_stack_free(pcre16_jit_stack *stack);
217         used only for characters with higher values. Even when Unicode property  
218         support is available, PCRE supports case-insensitive matching only when         void pcre16_assign_jit_stack(pcre16_extra *extra,
219         there  is  a  one-to-one  mapping between a letter's cases. There are a              pcre16_jit_callback callback, void *data);
220         small number of many-to-one mappings in Unicode;  these  are  not  sup-  
221         ported by PCRE.         const unsigned char *pcre16_maketables(void);
222    
223           int pcre16_fullinfo(const pcre16 *code, const pcre16_extra *extra,
224                int what, void *where);
225    
226           int pcre16_refcount(pcre16 *code, int adjust);
227    
228           int pcre16_config(int what, void *where);
229    
230           const char *pcre16_version(void);
231    
232           int pcre16_pattern_to_host_byte_order(pcre16 *code,
233                pcre16_extra *extra, const unsigned char *tables);
234    
235    
236    PCRE 16-BIT API INDIRECTED FUNCTIONS
237    
238           void *(*pcre16_malloc)(size_t);
239    
240           void (*pcre16_free)(void *);
241    
242           void *(*pcre16_stack_malloc)(size_t);
243    
244           void (*pcre16_stack_free)(void *);
245    
246           int (*pcre16_callout)(pcre16_callout_block *);
247    
248    
249    PCRE 16-BIT API 16-BIT-ONLY FUNCTION
250    
251           int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *output,
252                PCRE_SPTR16 input, int length, int *byte_order,
253                int keep_boms);
254    
255    
256    THE PCRE 16-BIT LIBRARY
257    
258           Starting  with  release  8.30, it is possible to compile a PCRE library
259           that supports 16-bit character strings, including  UTF-16  strings,  as
260           well  as  or instead of the original 8-bit library. The majority of the
261           work to make  this  possible  was  done  by  Zoltan  Herczeg.  The  two
262           libraries contain identical sets of functions, used in exactly the same
263           way. Only the names of the functions and the data types of their  argu-
264           ments  and results are different. To avoid over-complication and reduce
265           the documentation maintenance load,  most  of  the  PCRE  documentation
266           describes  the  8-bit  library,  with only occasional references to the
267           16-bit library. This page describes what is different when you use  the
268           16-bit library.
269    
270           WARNING:  A  single  application can be linked with both libraries, but
271           you must take care when processing any particular pattern to use  func-
272           tions  from  just one library. For example, if you want to study a pat-
273           tern that was compiled with  pcre16_compile(),  you  must  do  so  with
274           pcre16_study(), not pcre_study(), and you must free the study data with
275           pcre16_free_study().
276    
277    
278    THE HEADER FILE
279    
280           There is only one header file, pcre.h. It contains prototypes  for  all
281           the  functions  in  both  libraries,  as  well as definitions of flags,
282           structures, error codes, etc.
283    
284    
285    THE LIBRARY NAME
286    
287           In Unix-like systems, the 16-bit library is called libpcre16,  and  can
288           normally  be  accesss  by adding -lpcre16 to the command for linking an
289           application that uses PCRE.
290    
291    
292    STRING TYPES
293    
294           In the 8-bit library, strings are passed to PCRE library  functions  as
295           vectors  of  bytes  with  the  C  type "char *". In the 16-bit library,
296           strings are passed as vectors of unsigned 16-bit quantities. The  macro
297           PCRE_UCHAR16  specifies  an  appropriate  data type, and PCRE_SPTR16 is
298           defined as "const PCRE_UCHAR16 *". In very  many  environments,  "short
299           int" is a 16-bit data type. When PCRE is built, it defines PCRE_UCHAR16
300           as "short int", but checks that it really is a 16-bit data type. If  it
301           is not, the build fails with an error message telling the maintainer to
302           modify the definition appropriately.
303    
304    
305    STRUCTURE TYPES
306    
307           The types of the opaque structures that are used  for  compiled  16-bit
308           patterns  and  JIT stacks are pcre16 and pcre16_jit_stack respectively.
309           The  type  of  the  user-accessible  structure  that  is  returned   by
310           pcre16_study()  is  pcre16_extra, and the type of the structure that is
311           used for passing data to a callout  function  is  pcre16_callout_block.
312           These structures contain the same fields, with the same names, as their
313           8-bit counterparts. The only difference is that pointers  to  character
314           strings are 16-bit instead of 8-bit types.
315    
316    
317    16-BIT FUNCTIONS
318    
319           For  every function in the 8-bit library there is a corresponding func-
320           tion in the 16-bit library with a name that starts with pcre16_ instead
321           of  pcre_.  The  prototypes are listed above. In addition, there is one
322           extra function, pcre16_utf16_to_host_byte_order(). This  is  a  utility
323           function  that converts a UTF-16 character string to host byte order if
324           necessary. The other 16-bit  functions  expect  the  strings  they  are
325           passed to be in host byte order.
326    
327           The input and output arguments of pcre16_utf16_to_host_byte_order() may
328           point to the same address, that is, conversion in place  is  supported.
329           The output buffer must be at least as long as the input.
330    
331           The  length  argument  specifies the number of 16-bit data units in the
332           input string; a negative value specifies a zero-terminated string.
333    
334           If byte_order is NULL, it is assumed that the string starts off in host
335           byte  order. This may be changed by byte-order marks (BOMs) anywhere in
336           the string (commonly as the first character).
337    
338           If byte_order is not NULL, a non-zero value of the integer to which  it
339           points  means  that  the input starts off in host byte order, otherwise
340           the opposite order is assumed. Again, BOMs in  the  string  can  change
341           this. The final byte order is passed back at the end of processing.
342    
343           If  keep_boms  is  not  zero,  byte-order  mark characters (0xfeff) are
344           copied into the output string. Otherwise they are discarded.
345    
346           The result of the function is the number of 16-bit  units  placed  into
347           the  output  buffer,  including  the  zero terminator if the string was
348           zero-terminated.
349    
350    
351    SUBJECT STRING OFFSETS
352    
353           The offsets within subject strings that are returned  by  the  matching
354           functions are in 16-bit units rather than bytes.
355    
356    
357    NAMED SUBPATTERNS
358    
359           The  name-to-number translation table that is maintained for named sub-
360           patterns uses 16-bit characters.  The  pcre16_get_stringtable_entries()
361           function returns the length of each entry in the table as the number of
362           16-bit data units.
363    
364    
365    OPTION NAMES
366    
367           There   are   two   new   general   option   names,   PCRE_UTF16    and
368           PCRE_NO_UTF16_CHECK,     which     correspond    to    PCRE_UTF8    and
369           PCRE_NO_UTF8_CHECK in the 8-bit library. In  fact,  these  new  options
370           define the same bits in the options word.
371    
372           For  the  pcre16_config() function there is an option PCRE_CONFIG_UTF16
373           that returns 1 if UTF-16 support is configured, otherwise  0.  If  this
374           option  is given to pcre_config(), or if the PCRE_CONFIG_UTF8 option is
375           given to pcre16_config(), the result is the PCRE_ERROR_BADOPTION error.
376    
377    
378    CHARACTER CODES
379    
380           In 16-bit mode, when  PCRE_UTF16  is  not  set,  character  values  are
381           treated in the same way as in 8-bit, non UTF-8 mode, except, of course,
382           that they can range from 0 to 0xffff instead of 0  to  0xff.  Character
383           types  for characters less than 0xff can therefore be influenced by the
384           locale in the same way as before.  Characters greater  than  0xff  have
385           only one case, and no "type" (such as letter or digit).
386    
387           In  UTF-16  mode,  the  character  code  is  Unicode, in the range 0 to
388           0x10ffff, with the exception of values in the range  0xd800  to  0xdfff
389           because  those  are "surrogate" values that are used in pairs to encode
390           values greater than 0xffff.
391    
392           A UTF-16 string can indicate its endianness by special code knows as  a
393           byte-order mark (BOM). The PCRE functions do not handle this, expecting
394           strings  to  be  in  host  byte  order.  A  utility   function   called
395           pcre16_utf16_to_host_byte_order()  is  provided  to help with this (see
396           above).
397    
398    
399    ERROR NAMES
400    
401           The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16  corre-
402           spond  to  their  8-bit  counterparts.  The error PCRE_ERROR_BADMODE is
403           given when a compiled pattern is passed to a  function  that  processes
404           patterns  in  the  other  mode, for example, if a pattern compiled with
405           pcre_compile() is passed to pcre16_exec().
406    
407           There are new error codes whose names  begin  with  PCRE_UTF16_ERR  for
408           invalid  UTF-16  strings,  corresponding to the PCRE_UTF8_ERR codes for
409           UTF-8 strings that are described in the section entitled "Reason  codes
410           for  invalid UTF-8 strings" in the main pcreapi page. The UTF-16 errors
411           are:
412    
413             PCRE_UTF16_ERR1  Missing low surrogate at end of string
414             PCRE_UTF16_ERR2  Invalid low surrogate follows high surrogate
415             PCRE_UTF16_ERR3  Isolated low surrogate
416             PCRE_UTF16_ERR4  Invalid character 0xfffe
417    
418    
419    ERROR TEXTS
420    
421           If there is an error while compiling a pattern, the error text that  is
422           passed  back by pcre16_compile() or pcre16_compile2() is still an 8-bit
423           character string, zero-terminated.
424    
425    
426    CALLOUTS
427    
428           The subject and mark fields in the callout block that is  passed  to  a
429           callout function point to 16-bit vectors.
430    
431    
432    TESTING
433    
434           The  pcretest  program continues to operate with 8-bit input and output
435           files, but it can be used for testing the 16-bit library. If it is  run
436           with the command line option -16, patterns and subject strings are con-
437           verted from 8-bit to 16-bit before being passed to PCRE, and the 16-bit
438           library  functions  are used instead of the 8-bit ones. Returned 16-bit
439           strings are converted to 8-bit for output. If the 8-bit library was not
440           compiled, pcretest defaults to 16-bit and the -16 option is ignored.
441    
442           When  PCRE  is  being built, the RunTest script that is called by "make
443           check" uses the pcretest -C option to discover which of the  8-bit  and
444           16-bit libraries has been built, and runs the tests appropriately.
445    
446    
447    NOT SUPPORTED IN 16-BIT MODE
448    
449           Not all the features of the 8-bit library are available with the 16-bit
450           library. The C++ and POSIX wrapper functions  support  only  the  8-bit
451           library, and the pcregrep program is at present 8-bit only.
452    
453    
454  AUTHOR  AUTHOR
# Line 219  AUTHOR Line 457  AUTHOR
457         University Computing Service         University Computing Service
458         Cambridge CB2 3QH, England.         Cambridge CB2 3QH, England.
459    
        Putting  an actual email address here seems to have been a spam magnet,  
        so I've taken it away. If you want to email me, use  my  two  initials,  
        followed by the two digits 10, at the domain cam.ac.uk.  
   
460    
461  REVISION  REVISION
462    
463         Last updated: 06 August 2007         Last updated: 08 January 2012
464         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
465  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
466    
467    
468  PCREBUILD(3)                                                      PCREBUILD(3)  PCREBUILD(3)                                                      PCREBUILD(3)
469    
470    
# Line 241  NAME Line 475  NAME
475  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
476    
477         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
478         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
479         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
480         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
481         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
482         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
483           instead of configure to build PCRE.
484    
485           There  is  a  lot more information about building PCRE in non-Unix-like
486           environments in the file called NON_UNIX_USE, which is part of the PCRE
487           distribution.  You  should consult this file as well as the README file
488           if you are building in a non-Unix-like environment.
489    
490           The complete list of options for configure (which includes the standard
491           ones  such  as  the  selection  of  the  installation directory) can be
492           obtained by running
493    
494           ./configure --help           ./configure --help
495    
# Line 257  PCRE BUILD-TIME OPTIONS Line 501  PCRE BUILD-TIME OPTIONS
501         is not described.         is not described.
502    
503    
504    BUILDING 8-BIT and 16-BIT LIBRARIES
505    
506           By  default,  a  library  called libpcre is built, containing functions
507           that take string arguments contained in vectors  of  bytes,  either  as
508           single-byte  characters,  or interpreted as UTF-8 strings. You can also
509           build a separate library, called libpcre16, in which strings  are  con-
510           tained  in  vectors of 16-bit data units and interpreted either as sin-
511           gle-unit characters or UTF-16 strings, by adding
512    
513             --enable-pcre16
514    
515           to the configure command. If you do not want the 8-bit library, add
516    
517             --disable-pcre8
518    
519           as well. At least one of the two libraries must be built. Note that the
520           C++  and  POSIX wrappers are for the 8-bit library only, and that pcre-
521           grep is an 8-bit program. None of these are built if  you  select  only
522           the 16-bit library.
523    
524    
525    BUILDING SHARED AND STATIC LIBRARIES
526    
527           The  PCRE building process uses libtool to build both shared and static
528           Unix libraries by default. You can suppress one of these by adding  one
529           of
530    
531             --disable-shared
532             --disable-static
533    
534           to the configure command, as required.
535    
536    
537  C++ SUPPORT  C++ SUPPORT
538    
539         By default, the configure script will search for a C++ compiler and C++         By  default,  if the 8-bit library is being built, the configure script
540         header files. If it finds them, it automatically builds the C++ wrapper         will search for a C++ compiler and C++ header files. If it finds  them,
541         library for PCRE. You can disable this by adding         it  automatically  builds  the C++ wrapper library (which supports only
542           8-bit strings). You can disable this by adding
543    
544           --disable-cpp           --disable-cpp
545    
546         to the configure command.         to the configure command.
547    
548    
549  UTF-8 SUPPORT  UTF-8 and UTF-16 SUPPORT
550    
551         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF Unicode character strings, add
552    
553           --enable-utf8           --enable-utf
554    
555         to  the  configure  command.  Of  itself, this does not make PCRE treat         to the configure command.  This  setting  applies  to  both  libraries,
556         strings as UTF-8. As well as compiling PCRE with this option, you  also         adding support for UTF-8 to the 8-bit library and support for UTF-16 to
557         have  have to set the PCRE_UTF8 option when you call the pcre_compile()         the 16-bit library. There are no separate options  for  enabling  UTF-8
558         function.         and  UTF-16  independently because that would allow ridiculous settings
559           such as  requesting  UTF-16  support  while  building  only  the  8-bit
560           library.  It  is not possible to build one library with UTF support and
561           the other without in the same configuration. (For backwards compatibil-
562           ity, --enable-utf8 is a synonym of --enable-utf.)
563    
564           Of  itself,  this  setting does not make PCRE treat strings as UTF-8 or
565           UTF-16. As well as compiling PCRE with this option, you also have  have
566           to set the PCRE_UTF8 or PCRE_UTF16 option when you call one of the pat-
567           tern compiling functions.
568    
569           If you set --enable-utf when compiling in an EBCDIC  environment,  PCRE
570           expects its input to be either ASCII or UTF-8 (depending on the runtime
571           option). It is not possible to support both EBCDIC and UTF-8  codes  in
572           the  same  version  of  the  library.  Consequently,  --enable-utf  and
573           --enable-ebcdic are mutually exclusive.
574    
575    
576  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
577    
578         UTF-8 support allows PCRE to process character values greater than  255         UTF support allows the libraries to process character codepoints up  to
579         in  the  strings that it handles. On its own, however, it does not pro-         0x10ffff  in the strings that they handle. On its own, however, it does
580         vide any facilities for accessing the properties of such characters. If         not provide any facilities for accessing the properties of such charac-
581         you  want  to  be able to use the pattern escapes \P, \p, and \X, which         ters. If you want to be able to use the pattern escapes \P, \p, and \X,
582         refer to Unicode character properties, you must add         which refer to Unicode character properties, you must add
583    
584           --enable-unicode-properties           --enable-unicode-properties
585    
586         to the configure command. This implies UTF-8 support, even if you  have         to the configure command. This implies UTF support, even  if  you  have
587         not explicitly requested it.         not explicitly requested it.
588    
589         Including  Unicode  property  support  adds around 30K of tables to the         Including  Unicode  property  support  adds around 30K of tables to the
# Line 298  UNICODE CHARACTER PROPERTY SUPPORT Line 591  UNICODE CHARACTER PROPERTY SUPPORT
591         are supported. Details are given in the pcrepattern documentation.         are supported. Details are given in the pcrepattern documentation.
592    
593    
594    JUST-IN-TIME COMPILER SUPPORT
595    
596           Just-in-time compiler support is included in the build by specifying
597    
598             --enable-jit
599    
600           This  support  is available only for certain hardware architectures. If
601           this option is set for an  unsupported  architecture,  a  compile  time
602           error  occurs.   See  the pcrejit documentation for a discussion of JIT
603           usage. When JIT support is enabled, pcregrep automatically makes use of
604           it, unless you add
605    
606             --disable-pcregrep-jit
607    
608           to the "configure" command.
609    
610    
611  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
612    
613         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
614         the end of a line. This is the normal newline  character  on  Unix-like         the end of a line. This is the normal newline  character  on  Unix-like
615         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
616         instead, by adding         adding
617    
618           --enable-newline-is-cr           --enable-newline-is-cr
619    
# Line 326  CODE VALUE OF NEWLINE Line 636  CODE VALUE OF NEWLINE
636    
637         causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
638    
639         Whatever line ending convention is selected when PCRE is built  can  be         Whatever  line  ending convention is selected when PCRE is built can be
640         overridden  when  the library functions are called. At build time it is         overridden when the library functions are called. At build time  it  is
641         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
642    
643    
644  BUILDING SHARED AND STATIC LIBRARIES  WHAT \R MATCHES
645    
646         The PCRE building process uses libtool to build both shared and  static         By  default,  the  sequence \R in a pattern matches any Unicode newline
647         Unix  libraries by default. You can suppress one of these by adding one         sequence, whatever has been selected as the line  ending  sequence.  If
648         of         you specify
649    
650           --disable-shared           --enable-bsr-anycrlf
          --disable-static  
651    
652         to the configure command, as required.         the  default  is changed so that \R matches only CR, LF, or CRLF. What-
653           ever is selected when PCRE is built can be overridden when the  library
654           functions are called.
655    
656    
657  POSIX MALLOC USAGE  POSIX MALLOC USAGE
658    
659         When PCRE is called through the POSIX interface (see the pcreposix doc-         When  the  8-bit library is called through the POSIX interface (see the
660         umentation),  additional  working  storage  is required for holding the         pcreposix documentation), additional working storage  is  required  for
661         pointers to capturing substrings, because PCRE requires three  integers         holding  the  pointers  to  capturing substrings, because PCRE requires
662         per  substring,  whereas  the POSIX interface provides only two. If the         three integers per substring, whereas the POSIX interface provides only
663         number of expected substrings is small, the wrapper function uses space         two.  If  the number of expected substrings is small, the wrapper func-
664         on the stack, because this is faster than using malloc() for each call.         tion uses space on the stack, because this is faster  than  using  mal-
665         The default threshold above which the stack is no longer used is 10; it         loc()  for each call. The default threshold above which the stack is no
666         can be changed by adding a setting such as         longer used is 10; it can be changed by adding a setting such as
667    
668           --with-posix-malloc-threshold=20           --with-posix-malloc-threshold=20
669    
# Line 361  POSIX MALLOC USAGE Line 672  POSIX MALLOC USAGE
672    
673  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
674    
675         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
676         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
677         nation  metacharacter).  By default, two-byte values are used for these         nation metacharacter). By default, two-byte values are used  for  these
678         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets,  leading  to  a  maximum size for a compiled pattern of around
679         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
680         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless,  some  people do want to process truly enormous patterns,
681         is  possible  to compile PCRE to use three-byte or four-byte offsets by         so it is possible to compile PCRE to use three-byte or  four-byte  off-
682         adding a setting such as         sets by adding a setting such as
683    
684           --with-link-size=3           --with-link-size=3
685    
686         to the configure command. The value given must be 2,  3,  or  4.  Using         to  the  configure command. The value given must be 2, 3, or 4. For the
687         longer  offsets slows down the operation of PCRE because it has to load         16-bit library, a value of 3 is rounded up to 4. Using  longer  offsets
688         additional bytes when handling them.         slows down the operation of PCRE because it has to load additional data
689           when handling them.
690    
691    
692  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
# Line 395  AVOIDING EXCESSIVE STACK USAGE Line 707  AVOIDING EXCESSIVE STACK USAGE
707         to  the  configure  command. With this configuration, PCRE will use the         to  the  configure  command. With this configuration, PCRE will use the
708         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-
709         ment  functions. By default these point to malloc() and free(), but you         ment  functions. By default these point to malloc() and free(), but you
710         can replace the pointers so that your own functions are used.         can replace the pointers so that your own functions are used instead.
711    
712         Separate functions are  provided  rather  than  using  pcre_malloc  and         Separate functions are  provided  rather  than  using  pcre_malloc  and
713         pcre_free  because  the  usage  is  very  predictable:  the block sizes         pcre_free  because  the  usage  is  very  predictable:  the block sizes
# Line 403  AVOIDING EXCESSIVE STACK USAGE Line 715  AVOIDING EXCESSIVE STACK USAGE
715         reverse  order.  A calling program might be able to implement optimized         reverse  order.  A calling program might be able to implement optimized
716         functions that perform better  than  malloc()  and  free().  PCRE  runs         functions that perform better  than  malloc()  and  free().  PCRE  runs
717         noticeably more slowly when built in this way. This option affects only         noticeably more slowly when built in this way. This option affects only
718         the  pcre_exec()  function;  it   is   not   relevant   for   the   the         the pcre_exec() function; it is not relevant for pcre_dfa_exec().
        pcre_dfa_exec() function.  
719    
720    
721  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
722    
723         Internally,  PCRE has a function called match(), which it calls repeat-         Internally, PCRE has a function called match(), which it calls  repeat-
724         edly  (sometimes  recursively)  when  matching  a  pattern   with   the         edly   (sometimes   recursively)  when  matching  a  pattern  with  the
725         pcre_exec()  function.  By controlling the maximum number of times this         pcre_exec() function. By controlling the maximum number of  times  this
726         function may be called during a single matching operation, a limit  can         function  may be called during a single matching operation, a limit can
727         be  placed  on  the resources used by a single call to pcre_exec(). The         be placed on the resources used by a single call  to  pcre_exec().  The
728         limit can be changed at run time, as described in the pcreapi  documen-         limit  can be changed at run time, as described in the pcreapi documen-
729         tation.  The default is 10 million, but this can be changed by adding a         tation. The default is 10 million, but this can be changed by adding  a
730         setting such as         setting such as
731    
732           --with-match-limit=500000           --with-match-limit=500000
733    
734         to  the  configure  command.  This  setting  has  no  effect   on   the         to   the   configure  command.  This  setting  has  no  effect  on  the
735         pcre_dfa_exec() matching function.         pcre_dfa_exec() matching function.
736    
737         In  some  environments  it is desirable to limit the depth of recursive         In some environments it is desirable to limit the  depth  of  recursive
738         calls of match() more strictly than the total number of calls, in order         calls of match() more strictly than the total number of calls, in order
739         to  restrict  the maximum amount of stack (or heap, if --disable-stack-         to restrict the maximum amount of stack (or heap,  if  --disable-stack-
740         for-recursion is specified) that is used. A second limit controls this;         for-recursion is specified) that is used. A second limit controls this;
741         it  defaults  to  the  value  that is set for --with-match-limit, which         it defaults to the value that  is  set  for  --with-match-limit,  which
742         imposes no additional constraints. However, you can set a  lower  limit         imposes  no  additional constraints. However, you can set a lower limit
743         by adding, for example,         by adding, for example,
744    
745           --with-match-limit-recursion=10000           --with-match-limit-recursion=10000
746    
747         to  the  configure  command.  This  value can also be overridden at run         to the configure command. This value can  also  be  overridden  at  run
748         time.         time.
749    
750    
751  CREATING CHARACTER TABLES AT BUILD TIME  CREATING CHARACTER TABLES AT BUILD TIME
752    
753         PCRE uses fixed tables for processing characters whose code values  are         PCRE  uses fixed tables for processing characters whose code values are
754         less  than 256. By default, PCRE is built with a set of tables that are         less than 256. By default, PCRE is built with a set of tables that  are
755         distributed in the file pcre_chartables.c.dist. These  tables  are  for         distributed  in  the  file pcre_chartables.c.dist. These tables are for
756         ASCII codes only. If you add         ASCII codes only. If you add
757    
758           --enable-rebuild-chartables           --enable-rebuild-chartables
759    
760         to  the  configure  command, the distributed tables are no longer used.         to the configure command, the distributed tables are  no  longer  used.
761         Instead, a program called dftables is compiled and  run.  This  outputs         Instead,  a  program  called dftables is compiled and run. This outputs
762         the source for new set of tables, created in the default locale of your         the source for new set of tables, created in the default locale of your
763         C runtime system. (This method of replacing the tables does not work if         C runtime system. (This method of replacing the tables does not work if
764         you  are cross compiling, because dftables is run on the local host. If         you are cross compiling, because dftables is run on the local host.  If
765         you need to create alternative tables when cross  compiling,  you  will         you  need  to  create alternative tables when cross compiling, you will
766         have to do so "by hand".)         have to do so "by hand".)
767    
768    
769  USING EBCDIC CODE  USING EBCDIC CODE
770    
771         PCRE  assumes  by  default that it will run in an environment where the         PCRE assumes by default that it will run in an  environment  where  the
772         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
773         This  is  the  case for most computer operating systems. PCRE can, how-         This is the case for most computer operating systems.  PCRE  can,  how-
774         ever, be compiled to run in an EBCDIC environment by adding         ever, be compiled to run in an EBCDIC environment by adding
775    
776           --enable-ebcdic           --enable-ebcdic
777    
778         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
779         bles.  You  should  only  use  it if you know that you are in an EBCDIC         bles. You should only use it if you know that  you  are  in  an  EBCDIC
780         environment (for example, an IBM mainframe operating system).         environment  (for  example,  an  IBM  mainframe  operating system). The
781           --enable-ebcdic option is incompatible with --enable-utf.
782    
783    
784    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
785    
786           By default, pcregrep reads all files as plain text. You can build it so
787           that it recognizes files whose names end in .gz or .bz2, and reads them
788           with libz or libbz2, respectively, by adding one or both of
789    
790             --enable-pcregrep-libz
791             --enable-pcregrep-libbz2
792    
793           to the configure command. These options naturally require that the rel-
794           evant  libraries  are installed on your system. Configuration will fail
795           if they are not.
796    
797    
798    PCREGREP BUFFER SIZE
799    
800           pcregrep uses an internal buffer to hold a "window" on the file  it  is
801           scanning, in order to be able to output "before" and "after" lines when
802           it finds a match. The size of the buffer is controlled by  a  parameter
803           whose default value is 20K. The buffer itself is three times this size,
804           but because of the way it is used for holding "before" lines, the long-
805           est  line  that  is guaranteed to be processable is the parameter size.
806           You can change the default parameter value by adding, for example,
807    
808             --with-pcregrep-bufsize=50K
809    
810           to the configure command. The caller of pcregrep can, however, override
811           this value by specifying a run-time option.
812    
813    
814    PCRETEST OPTION FOR LIBREADLINE SUPPORT
815    
816           If you add
817    
818             --enable-pcretest-libreadline
819    
820           to  the  configure  command,  pcretest  is  linked with the libreadline
821           library, and when its input is from a terminal, it reads it  using  the
822           readline() function. This provides line-editing and history facilities.
823           Note that libreadline is GPL-licensed, so if you distribute a binary of
824           pcretest linked in this way, there may be licensing issues.
825    
826           Setting  this  option  causes  the -lreadline option to be added to the
827           pcretest build. In many operating environments with  a  sytem-installed
828           libreadline this is sufficient. However, in some environments (e.g.  if
829           an unmodified distribution version of readline is in use),  some  extra
830           configuration  may  be necessary. The INSTALL file for libreadline says
831           this:
832    
833             "Readline uses the termcap functions, but does not link with the
834             termcap or curses library itself, allowing applications which link
835             with readline the to choose an appropriate library."
836    
837           If your environment has not been set up so that an appropriate  library
838           is automatically included, you may need to add something like
839    
840             LIBS="-ncurses"
841    
842           immediately before the configure command.
843    
844    
845  SEE ALSO  SEE ALSO
846    
847         pcreapi(3), pcre_config(3).         pcreapi(3), pcre16, pcre_config(3).
848    
849    
850  AUTHOR  AUTHOR
# Line 483  AUTHOR Line 856  AUTHOR
856    
857  REVISION  REVISION
858    
859         Last updated: 30 July 2007         Last updated: 07 January 2012
860         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
861  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
862    
863    
864  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
865    
866    
# Line 500  PCRE MATCHING ALGORITHMS Line 873  PCRE MATCHING ALGORITHMS
873         This document describes the two different algorithms that are available         This document describes the two different algorithms that are available
874         in PCRE for matching a compiled regular expression against a given sub-         in PCRE for matching a compiled regular expression against a given sub-
875         ject  string.  The  "standard"  algorithm  is  the  one provided by the         ject  string.  The  "standard"  algorithm  is  the  one provided by the
876         pcre_exec() function.  This works in the same was  as  Perl's  matching         pcre_exec() and pcre16_exec() functions. These work in the same was  as
877         function, and provides a Perl-compatible matching operation.         Perl's matching function, and provide a Perl-compatible matching opera-
878           tion. The just-in-time (JIT) optimization  that  is  described  in  the
879         An  alternative  algorithm is provided by the pcre_dfa_exec() function;         pcrejit documentation is compatible with these functions.
880         this operates in a different way, and is not  Perl-compatible.  It  has  
881         advantages  and disadvantages compared with the standard algorithm, and         An  alternative  algorithm  is  provided  by  the  pcre_dfa_exec()  and
882         these are described below.         pcre16_dfa_exec() functions; they operate in a different way,  and  are
883           not  Perl-compatible. This alternative has advantages and disadvantages
884           compared with the standard algorithm, and these are described below.
885    
886         When there is only one possible way in which a given subject string can         When there is only one possible way in which a given subject string can
887         match  a pattern, the two algorithms give the same answer. A difference         match  a pattern, the two algorithms give the same answer. A difference
# Line 571  THE ALTERNATIVE MATCHING ALGORITHM Line 946  THE ALTERNATIVE MATCHING ALGORITHM
946         though  it is not implemented as a traditional finite state machine (it         though  it is not implemented as a traditional finite state machine (it
947         keeps multiple states active simultaneously).         keeps multiple states active simultaneously).
948    
949           Although the general principle of this matching algorithm  is  that  it
950           scans  the subject string only once, without backtracking, there is one
951           exception: when a lookaround assertion is encountered,  the  characters
952           following  or  preceding  the  current  point  have to be independently
953           inspected.
954    
955         The scan continues until either the end of the subject is  reached,  or         The scan continues until either the end of the subject is  reached,  or
956         there  are  no more unterminated paths. At this point, terminated paths         there  are  no more unterminated paths. At this point, terminated paths
957         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
958         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
959         this algorithm finds all of them, and in particular, it finds the long-         this algorithm finds all of them, and in particular, it finds the long-
960         est.  In PCRE, there is an option to stop the algorithm after the first         est.  The  matches are returned in decreasing order of length. There is
961         match (which is necessarily the shortest) has been found.         an option to stop the algorithm after the first match (which is  neces-
962           sarily the shortest) is found.
963    
964         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
965         subject. If the pattern         subject. If the pattern
966    
967           cat(er(pillar)?)           cat(er(pillar)?)?
968    
969         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
970         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
971         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
972         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
973    
974         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
975         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
976    
977         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
978         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
979         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
980         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
981         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
982    
983           ^a++\w!           ^a++\w!
984    
985         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
986         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
987         it  is matched as if it were a standalone pattern at the current point,         it is matched as if it were a standalone pattern at the current  point,
988         and the longest match is then "locked in" for the rest of  the  overall         and  the  longest match is then "locked in" for the rest of the overall
989         pattern.         pattern.
990    
991         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
992         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
993         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
994         algorithm does not attempt to do this. This means that no captured sub-         algorithm does not attempt to do this. This means that no captured sub-
995         strings are available.         strings are available.
996    
997         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
998         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
999    
1000         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
1001         ence  as  the  condition or test for a specific group recursion are not         ence as the condition or test for a specific group  recursion  are  not
1002         supported.         supported.
1003    
1004         5. Because many paths through the tree may be  active,  the  \K  escape         5.  Because  many  paths  through the tree may be active, the \K escape
1005         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
1006         be on some paths and not on others), is not  supported.  It  causes  an         be  on  some  paths  and not on others), is not supported. It causes an
1007         error if encountered.         error if encountered.
1008    
1009         6.  Callouts  are  supported, but the value of the capture_top field is         6. Callouts are supported, but the value of the  capture_top  field  is
1010         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
1011    
1012         7.  The \C escape sequence, which (in the standard algorithm) matches a         7.  The  \C  escape  sequence, which (in the standard algorithm) always
1013         single  byte, even in UTF-8 mode, is not supported because the alterna-         matches a single data unit, even in UTF-8 or UTF-16 modes, is not  sup-
1014         tive algorithm moves through the subject  string  one  character  at  a         ported  in these modes, because the alternative algorithm moves through
1015         time, for all active paths through the tree.         the subject string one character (not data unit) at  a  time,  for  all
1016           active paths through the tree.
1017    
1018           8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
1019           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
1020           negative assertion.
1021    
1022    
1023  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 643  ADVANTAGES OF THE ALTERNATIVE ALGORITHM Line 1030  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
1030         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
1031         things with callouts.         things with callouts.
1032    
1033         2.  There is much better support for partial matching. The restrictions         2.  Because  the  alternative  algorithm  scans the subject string just
1034         on the content of the pattern that apply when using the standard  algo-         once, and never needs to backtrack (except for lookbehinds), it is pos-
1035         rithm  for  partial matching do not apply to the alternative algorithm.         sible  to  pass  very  long subject strings to the matching function in
1036         For non-anchored patterns, the starting position of a partial match  is         several pieces, checking for partial matching each time. Although it is
1037         available.         possible  to  do multi-segment matching using the standard algorithm by
1038           retaining partially matched substrings, it  is  more  complicated.  The
1039         3.  Because  the  alternative  algorithm  scans the subject string just         pcrepartial  documentation  gives  details of partial matching and dis-
1040         once, and never needs to backtrack, it is possible to  pass  very  long         cusses multi-segment matching.
        subject  strings  to  the matching function in several pieces, checking  
        for partial matching each time.  
1041    
1042    
1043  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 678  AUTHOR Line 1063  AUTHOR
1063    
1064  REVISION  REVISION
1065    
1066         Last updated: 29 May 2007         Last updated: 08 January 2012
1067         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
1068  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
1069    
1070    
1071  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
1072    
1073    
1074  NAME  NAME
1075         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
1076    
1077           #include <pcre.h>
1078    
 PCRE NATIVE API  
1079    
1080         #include <pcre.h>  PCRE NATIVE API BASIC FUNCTIONS
1081    
1082         pcre *pcre_compile(const char *pattern, int options,         pcre *pcre_compile(const char *pattern, int options,
1083              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
# Line 706  PCRE NATIVE API Line 1091  PCRE NATIVE API
1091         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
1092              const char **errptr);              const char **errptr);
1093    
1094           void pcre_free_study(pcre_extra *extra);
1095    
1096         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
1097              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1098              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
# Line 715  PCRE NATIVE API Line 1102  PCRE NATIVE API
1102              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
1103              int *workspace, int wscount);              int *workspace, int wscount);
1104    
1105    
1106    PCRE NATIVE API STRING EXTRACTION FUNCTIONS
1107    
1108         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
1109              const char *subject, int *ovector,              const char *subject, int *ovector,
1110              int stringcount, const char *stringname,              int stringcount, const char *stringname,
# Line 746  PCRE NATIVE API Line 1136  PCRE NATIVE API
1136    
1137         void pcre_free_substring_list(const char **stringptr);         void pcre_free_substring_list(const char **stringptr);
1138    
1139    
1140    PCRE NATIVE API AUXILIARY FUNCTIONS
1141    
1142           pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);
1143    
1144           void pcre_jit_stack_free(pcre_jit_stack *stack);
1145    
1146           void pcre_assign_jit_stack(pcre_extra *extra,
1147                pcre_jit_callback callback, void *data);
1148    
1149         const unsigned char *pcre_maketables(void);         const unsigned char *pcre_maketables(void);
1150    
1151         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1152              int what, void *where);              int what, void *where);
1153    
        int pcre_info(const pcre *code, int *optptr, int *firstcharptr);  
   
1154         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1155    
1156         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1157    
1158         char *pcre_version(void);         const char *pcre_version(void);
1159    
1160           int pcre_pattern_to_host_byte_order(pcre *code,
1161                pcre_extra *extra, const unsigned char *tables);
1162    
1163    
1164    PCRE NATIVE API INDIRECTED FUNCTIONS
1165    
1166         void *(*pcre_malloc)(size_t);         void *(*pcre_malloc)(size_t);
1167    
# Line 770  PCRE NATIVE API Line 1174  PCRE NATIVE API
1174         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
1175    
1176    
1177    PCRE 8-BIT AND 16-BIT LIBRARIES
1178    
1179           From  release  8.30,  PCRE  can  be  compiled as a library for handling
1180           16-bit character strings as  well  as,  or  instead  of,  the  original
1181           library that handles 8-bit character strings. To avoid too much compli-
1182           cation, this document describes the 8-bit versions  of  the  functions,
1183           with only occasional references to the 16-bit library.
1184    
1185           The  16-bit  functions  operate in the same way as their 8-bit counter-
1186           parts; they just use different  data  types  for  their  arguments  and
1187           results, and their names start with pcre16_ instead of pcre_. For every
1188           option that has UTF8 in its name (for example, PCRE_UTF8), there  is  a
1189           corresponding 16-bit name with UTF8 replaced by UTF16. This facility is
1190           in fact just cosmetic; the 16-bit option names define the same bit val-
1191           ues.
1192    
1193           References to bytes and UTF-8 in this document should be read as refer-
1194           ences to 16-bit data  quantities  and  UTF-16  when  using  the  16-bit
1195           library,  unless specified otherwise. More details of the specific dif-
1196           ferences for the 16-bit library are given in the pcre16 page.
1197    
1198    
1199  PCRE API OVERVIEW  PCRE API OVERVIEW
1200    
1201         PCRE has its own native API, which is described in this document. There         PCRE has its own native API, which is described in this document. There
1202         are also some wrapper functions that correspond to  the  POSIX  regular         are  also some wrapper functions (for the 8-bit library only) that cor-
1203         expression  API.  These  are  described in the pcreposix documentation.         respond to the POSIX regular expression  API,  but  they  do  not  give
1204         Both of these APIs define a set of C function calls. A C++  wrapper  is         access  to  all  the functionality. They are described in the pcreposix
1205         distributed with PCRE. It is documented in the pcrecpp page.         documentation. Both of these APIs define a set of C function  calls.  A
1206           C++ wrapper (again for the 8-bit library only) is also distributed with
1207         The  native  API  C  function prototypes are defined in the header file         PCRE. It is documented in the pcrecpp page.
1208         pcre.h, and on Unix systems the library itself is called  libpcre.   It  
1209         can normally be accessed by adding -lpcre to the command for linking an         The native API C function prototypes are defined  in  the  header  file
1210         application  that  uses  PCRE.  The  header  file  defines  the  macros         pcre.h,  and  on Unix-like systems the (8-bit) library itself is called
1211         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-         libpcre. It can normally be accessed by adding -lpcre  to  the  command
1212         bers for the library.  Applications can use these  to  include  support         for  linking an application that uses PCRE. The header file defines the
1213           macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release
1214           numbers  for the library. Applications can use these to include support
1215         for different releases of PCRE.         for different releases of PCRE.
1216    
1217         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         In a Windows environment, if you want to statically link an application
1218         pcre_exec() are used for compiling and matching regular expressions  in         program  against  a  non-dll  pcre.a  file, you must define PCRE_STATIC
1219         a  Perl-compatible  manner. A sample program that demonstrates the sim-         before including pcre.h or pcrecpp.h, because otherwise  the  pcre_mal-
1220         plest way of using them is provided in the file  called  pcredemo.c  in         loc()   and   pcre_free()   exported   functions   will   be   declared
1221         the  source distribution. The pcresample documentation describes how to         __declspec(dllimport), with unwanted results.
1222         run it.  
1223           The  functions  pcre_compile(),  pcre_compile2(),   pcre_study(),   and
1224           pcre_exec()  are used for compiling and matching regular expressions in
1225           a Perl-compatible manner. A sample program that demonstrates  the  sim-
1226           plest  way  of  using them is provided in the file called pcredemo.c in
1227           the PCRE source distribution. A listing of this program is given in the
1228           pcredemo  documentation, and the pcresample documentation describes how
1229           to compile and run it.
1230    
1231           Just-in-time compiler support is an optional feature of PCRE  that  can
1232           be built in appropriate hardware environments. It greatly speeds up the
1233           matching performance of  many  patterns.  Simple  programs  can  easily
1234           request  that  it  be  used  if available, by setting an option that is
1235           ignored when it is not relevant. More complicated programs  might  need
1236           to     make    use    of    the    functions    pcre_jit_stack_alloc(),
1237           pcre_jit_stack_free(), and pcre_assign_jit_stack() in order to  control
1238           the  JIT  code's  memory  usage.   These functions are discussed in the
1239           pcrejit documentation.
1240    
1241         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
1242         ble,  is  also provided. This uses a different algorithm for the match-         ble,  is  also provided. This uses a different algorithm for the match-
1243         ing. The alternative algorithm finds all possible matches (at  a  given         ing. The alternative algorithm finds all possible matches (at  a  given
1244         point  in  the subject), and scans the subject just once. However, this         point  in  the  subject), and scans the subject just once (unless there
1245         algorithm does not return captured substrings. A description of the two         are lookbehind assertions). However, this  algorithm  does  not  return
1246         matching  algorithms and their advantages and disadvantages is given in         captured  substrings.  A description of the two matching algorithms and
1247         the pcrematching documentation.         their advantages and disadvantages is given in the  pcrematching  docu-
1248           mentation.
1249    
1250         In addition to the main compiling and  matching  functions,  there  are         In  addition  to  the  main compiling and matching functions, there are
1251         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
1252         string that is matched by pcre_exec(). They are:         string that is matched by pcre_exec(). They are:
1253    
# Line 816  PCRE API OVERVIEW Line 1262  PCRE API OVERVIEW
1262         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
1263         to free the memory used for extracted strings.         to free the memory used for extracted strings.
1264    
1265         The  function  pcre_maketables()  is  used  to build a set of character         The function pcre_maketables() is used to  build  a  set  of  character
1266         tables  in  the  current  locale   for   passing   to   pcre_compile(),         tables   in   the   current   locale  for  passing  to  pcre_compile(),
1267         pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is         pcre_exec(), or pcre_dfa_exec(). This is an optional facility  that  is
1268         provided for specialist use.  Most  commonly,  no  special  tables  are         provided  for  specialist  use.  Most  commonly,  no special tables are
1269         passed,  in  which case internal tables that are generated when PCRE is         passed, in which case internal tables that are generated when  PCRE  is
1270         built are used.         built are used.
1271    
1272         The function pcre_fullinfo() is used to find out  information  about  a         The  function  pcre_fullinfo()  is used to find out information about a
1273         compiled  pattern; pcre_info() is an obsolete version that returns only         compiled pattern. The function pcre_version() returns a  pointer  to  a
1274         some of the available information, but is retained for  backwards  com-         string containing the version of PCRE and its date of release.
        patibility.   The function pcre_version() returns a pointer to a string  
        containing the version of PCRE and its date of release.  
1275    
1276         The function pcre_refcount() maintains a  reference  count  in  a  data         The  function  pcre_refcount()  maintains  a  reference count in a data
1277         block  containing  a compiled pattern. This is provided for the benefit         block containing a compiled pattern. This is provided for  the  benefit
1278         of object-oriented applications.         of object-oriented applications.
1279    
1280         The global variables pcre_malloc and pcre_free  initially  contain  the         The  global  variables  pcre_malloc and pcre_free initially contain the
1281         entry  points  of  the  standard malloc() and free() functions, respec-         entry points of the standard malloc()  and  free()  functions,  respec-
1282         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
1283         so  a  calling  program  can replace them if it wishes to intercept the         so a calling program can replace them if it  wishes  to  intercept  the
1284         calls. This should be done before calling any PCRE functions.         calls. This should be done before calling any PCRE functions.
1285    
1286         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also         The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
1287         indirections  to  memory  management functions. These special functions         indirections to memory management functions.  These  special  functions
1288         are used only when PCRE is compiled to use  the  heap  for  remembering         are  used  only  when  PCRE is compiled to use the heap for remembering
1289         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
1290         function. See the pcrebuild documentation for  details  of  how  to  do         function.  See  the  pcrebuild  documentation  for details of how to do
1291         this.  It  is  a non-standard way of building PCRE, for use in environ-         this. It is a non-standard way of building PCRE, for  use  in  environ-
1292         ments that have limited stacks. Because of the greater  use  of  memory         ments  that  have  limited stacks. Because of the greater use of memory
1293         management,  it  runs  more  slowly. Separate functions are provided so         management, it runs more slowly. Separate  functions  are  provided  so
1294         that special-purpose external code can be  used  for  this  case.  When         that  special-purpose  external  code  can  be used for this case. When
1295         used,  these  functions  are always called in a stack-like manner (last         used, these functions are always called in a  stack-like  manner  (last
1296         obtained, first freed), and always for memory blocks of the same  size.         obtained,  first freed), and always for memory blocks of the same size.
1297         There  is  a discussion about PCRE's stack usage in the pcrestack docu-         There is a discussion about PCRE's stack usage in the  pcrestack  docu-
1298         mentation.         mentation.
1299    
1300         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
1301         by  the  caller  to  a "callout" function, which PCRE will then call at         by the caller to a "callout" function, which PCRE  will  then  call  at
1302         specified points during a matching operation. Details are given in  the         specified  points during a matching operation. Details are given in the
1303         pcrecallout documentation.         pcrecallout documentation.
1304    
1305    
1306  NEWLINES  NEWLINES
1307    
1308         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
1309         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
1310         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
1311         ceding, or any Unicode newline sequence. The Unicode newline  sequences         ceding,  or any Unicode newline sequence. The Unicode newline sequences
1312         are  the  three just mentioned, plus the single characters VT (vertical         are the three just mentioned, plus the single characters  VT  (vertical
1313         tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line         tab,  U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
1314         separator, U+2028), and PS (paragraph separator, U+2029).         separator, U+2028), and PS (paragraph separator, U+2029).
1315    
1316         Each  of  the first three conventions is used by at least one operating         Each of the first three conventions is used by at least  one  operating
1317         system as its standard newline sequence. When PCRE is built, a  default         system  as its standard newline sequence. When PCRE is built, a default
1318         can  be  specified.  The default default is LF, which is the Unix stan-         can be specified.  The default default is LF, which is the  Unix  stan-
1319         dard. When PCRE is run, the default can be overridden,  either  when  a         dard.  When  PCRE  is run, the default can be overridden, either when a
1320         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
1321    
1322           At compile time, the newline convention can be specified by the options
1323           argument  of  pcre_compile(), or it can be specified by special text at
1324           the start of the pattern itself; this overrides any other settings. See
1325           the pcrepattern page for details of the special character sequences.
1326    
1327         In the PCRE documentation the word "newline" is used to mean "the char-         In the PCRE documentation the word "newline" is used to mean "the char-
1328         acter or pair of characters that indicate a line break". The choice  of         acter or pair of characters that indicate a line break". The choice  of
1329         newline  convention  affects  the  handling of the dot, circumflex, and         newline  convention  affects  the  handling of the dot, circumflex, and
1330         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
1331         CRLF  is a recognized line ending sequence, the match position advance-         CRLF  is a recognized line ending sequence, the match position advance-
1332         ment for a non-anchored pattern. The choice of newline convention  does         ment for a non-anchored pattern. There is more detail about this in the
1333         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
1334    
1335           The  choice of newline convention does not affect the interpretation of
1336           the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
1337           which is controlled in a similar way, but by separate options.
1338    
1339    
1340  MULTITHREADING  MULTITHREADING
# Line 891  MULTITHREADING Line 1344  MULTITHREADING
1344         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
1345         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
1346    
1347         The  compiled form of a regular expression is not altered during match-         The compiled form of a regular expression is not altered during  match-
1348         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
1349         at once.         at once.
1350    
1351           If the just-in-time optimization feature is being used, it needs  sepa-
1352           rate  memory stack areas for each thread. See the pcrejit documentation
1353           for more details.
1354    
1355    
1356  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
1357    
1358         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
1359         later time, possibly by a different program, and even on a  host  other         later  time,  possibly by a different program, and even on a host other
1360         than  the  one  on  which  it  was  compiled.  Details are given in the         than the one on which  it  was  compiled.  Details  are  given  in  the
1361         pcreprecompile documentation. However, compiling a  regular  expression         pcreprecompile  documentation,  which  includes  a  description  of the
1362         with  one version of PCRE for use with a different version is not guar-         pcre_pattern_to_host_byte_order() function. However, compiling a  regu-
1363         anteed to work and may cause crashes.         lar  expression  with one version of PCRE for use with a different ver-
1364           sion is not guaranteed to work and may cause crashes.
1365    
1366    
1367  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 917  CHECKING BUILD-TIME OPTIONS Line 1375  CHECKING BUILD-TIME OPTIONS
1375    
1376         The  first  argument  for pcre_config() is an integer, specifying which         The  first  argument  for pcre_config() is an integer, specifying which
1377         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
1378         into  which  the  information  is  placed. The following information is         into  which  the  information  is placed. The returned value is zero on
1379           success, or the negative error code PCRE_ERROR_BADOPTION if  the  value
1380           in  the  first argument is not recognized. The following information is
1381         available:         available:
1382    
1383           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
1384    
1385         The output is an integer that is set to one if UTF-8 support is  avail-         The output is an integer that is set to one if UTF-8 support is  avail-
1386         able; otherwise it is set to zero.         able;  otherwise  it  is  set  to  zero. If this option is given to the
1387           16-bit  version  of  this  function,  pcre16_config(),  the  result  is
1388           PCRE_ERROR_BADOPTION.
1389    
1390             PCRE_CONFIG_UTF16
1391    
1392           The output is an integer that is set to one if UTF-16 support is avail-
1393           able; otherwise it is set to zero. This value should normally be  given
1394           to the 16-bit version of this function, pcre16_config(). If it is given
1395           to the 8-bit version of this function, the result is  PCRE_ERROR_BADOP-
1396           TION.
1397    
1398           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
1399    
1400         The  output  is  an  integer  that is set to one if support for Unicode         The  output  is  an  integer  that is set to one if support for Unicode
1401         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1402    
1403             PCRE_CONFIG_JIT
1404    
1405           The output is an integer that is set to one if support for just-in-time
1406           compiling is available; otherwise it is set to zero.
1407    
1408             PCRE_CONFIG_JITTARGET
1409    
1410           The  output is a pointer to a zero-terminated "const char *" string. If
1411           JIT support is available, the string contains the name of the architec-
1412           ture  for  which the JIT compiler is configured, for example "x86 32bit
1413           (little endian + unaligned)". If JIT  support  is  not  available,  the
1414           result is NULL.
1415    
1416           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1417    
1418         The output is an integer whose value specifies  the  default  character         The  output  is  an integer whose value specifies the default character
1419         sequence  that is recognized as meaning "newline". The four values that         sequence that is recognized as meaning "newline". The four values  that
1420         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1421         and  -1  for  ANY. The default should normally be the standard sequence         and -1 for ANY.  Though they are derived from ASCII,  the  same  values
1422         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1423           spond to the standard sequence for your operating system.
1424    
1425             PCRE_CONFIG_BSR
1426    
1427           The output is an integer whose value indicates what character sequences
1428           the  \R  escape sequence matches by default. A value of 0 means that \R
1429           matches any Unicode line ending sequence; a value of 1  means  that  \R
1430           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1431           tern is compiled or matched.
1432    
1433           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1434    
1435         The output is an integer that contains the number  of  bytes  used  for         The output is an integer that contains the number  of  bytes  used  for
1436         internal linkage in compiled regular expressions. The value is 2, 3, or         internal  linkage  in  compiled  regular  expressions.  For  the  8-bit
1437         4. Larger values allow larger regular expressions to  be  compiled,  at         library, the value can be 2, 3, or 4. For the 16-bit library, the value
1438         the  expense  of  slower matching. The default value of 2 is sufficient         is either 2 or 4 and is still a number of bytes. The default value of 2
1439         for all but the most massive patterns, since  it  allows  the  compiled         is sufficient for all but the most massive patterns,  since  it  allows
1440         pattern to be up to 64K in size.         the  compiled  pattern  to  be  up to 64K in size.  Larger values allow
1441           larger regular expressions to be compiled, at  the  expense  of  slower
1442           matching.
1443    
1444           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1445    
# Line 955  CHECKING BUILD-TIME OPTIONS Line 1449  CHECKING BUILD-TIME OPTIONS
1449    
1450           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1451    
1452         The output is an integer that gives the default limit for the number of         The  output is a long integer that gives the default limit for the num-
1453         internal matching function calls in a  pcre_exec()  execution.  Further         ber of internal matching function calls  in  a  pcre_exec()  execution.
1454         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1455    
1456           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1457    
1458         The  output is an integer that gives the default limit for the depth of         The output is a long integer that gives the default limit for the depth
1459         recursion when calling the internal matching function in a  pcre_exec()         of  recursion  when  calling  the  internal  matching  function  in   a
1460         execution. Further details are given with pcre_exec() below.         pcre_exec()  execution.  Further  details  are  given  with pcre_exec()
1461           below.
1462    
1463           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1464    
1465         The  output is an integer that is set to one if internal recursion when         The output is an integer that is set to one if internal recursion  when
1466         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1467         the  stack  to remember their state. This is the usual way that PCRE is         the stack to remember their state. This is the usual way that  PCRE  is
1468         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1469         on  the  heap  instead  of  recursive  function  calls.  In  this case,         on the  heap  instead  of  recursive  function  calls.  In  this  case,
1470         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
1471         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1472    
1473    
# Line 989  COMPILING A PATTERN Line 1484  COMPILING A PATTERN
1484    
1485         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1486         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1487         the  two interfaces is that pcre_compile2() has an additional argument,         the two interfaces is that pcre_compile2() has an additional  argument,
1488         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr,  via  which  a  numerical  error code can be returned. To
1489           avoid too much repetition, we refer just to pcre_compile()  below,  but
1490           the information applies equally to pcre_compile2().
1491    
1492         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1493         the  pattern  argument.  A  pointer to a single block of memory that is         the pattern argument. A pointer to a single block  of  memory  that  is
1494         obtained via pcre_malloc is returned. This contains the  compiled  code         obtained  via  pcre_malloc is returned. This contains the compiled code
1495         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1496         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1497         It is up to the caller to free the memory (via pcre_free) when it is no         It is up to the caller to free the memory (via pcre_free) when it is no
1498         longer required.         longer required.
1499    
1500         Although the compiled code of a PCRE regex is relocatable, that is,  it         Although  the compiled code of a PCRE regex is relocatable, that is, it
1501         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
1502         fully relocatable, because it may contain a copy of the tableptr  argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
1503         ment, which is an address (see below).         ment, which is an address (see below).
1504    
1505         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1506         pilation. It should be zero if no options are required.  The  available         pilation.  It  should be zero if no options are required. The available
1507         options  are  described  below. Some of them, in particular, those that         options are described below. Some of them (in  particular,  those  that
1508         are compatible with Perl, can also be set and  unset  from  within  the         are  compatible with Perl, but some others as well) can also be set and
1509         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset from within the pattern (see  the  detailed  description  in  the
1510         tion). For these options, the contents of the options  argument  speci-         pcrepattern  documentation). For those options that can be different in
1511         fies  their initial settings at the start of compilation and execution.         different parts of the pattern, the contents of  the  options  argument
1512         The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time         specifies their settings at the start of compilation and execution. The
1513         of matching as well as at compile time.         PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK,  and
1514           PCRE_NO_START_OPTIMIZE  options  can  be set at the time of matching as
1515           well as at compile time.
1516    
1517         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1518         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1519         sets the variable pointed to by errptr to point to a textual error mes-         sets the variable pointed to by errptr to point to a textual error mes-
1520         sage. This is a static string that is part of the library. You must not         sage. This is a static string that is part of the library. You must not
1521         try to free it. The offset from the start of the pattern to the charac-         try to free it. Normally, the offset from the start of the  pattern  to
1522         ter where the error was discovered is placed in the variable pointed to         the  byte  that  was  being  processed when the error was discovered is
1523         by  erroffset,  which must not be NULL. If it is, an immediate error is         placed in the variable pointed to by erroffset, which must not be  NULL
1524         given.         (if  it is, an immediate error is given). However, for an invalid UTF-8
1525           string, the offset is that of the first byte of the failing character.
1526         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-  
1527         codeptr  argument is not NULL, a non-zero error code number is returned         Some errors are not detected until the whole pattern has been  scanned;
1528         via this argument in the event of an error. This is in addition to  the         in  these  cases,  the offset passed back is the length of the pattern.
1529           Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1530           It may sometimes point into the middle of a UTF-8 character.
1531    
1532           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1533           codeptr argument is not NULL, a non-zero error code number is  returned
1534           via  this argument in the event of an error. This is in addition to the
1535         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1536    
1537         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
1538         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1539         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1540         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
1541         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1542         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1543         support below.         support below.
1544    
1545         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1546         pile():         pile():
1547    
1548           pcre *re;           pcre *re;
# Line 1050  COMPILING A PATTERN Line 1555  COMPILING A PATTERN
1555             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1556             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1557    
1558         The following names for option bits are defined in  the  pcre.h  header         The  following  names  for option bits are defined in the pcre.h header
1559         file:         file:
1560    
1561           PCRE_ANCHORED           PCRE_ANCHORED
1562    
1563         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
1564         is constrained to match only at the first matching point in the  string         is  constrained to match only at the first matching point in the string
1565         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1566         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1567         only way to do it in Perl.         only way to do it in Perl.
1568    
1569           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1570    
1571         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1572         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1573         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1574    
1575             PCRE_BSR_ANYCRLF
1576             PCRE_BSR_UNICODE
1577    
1578           These options (which are mutually exclusive) control what the \R escape
1579           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1580           or to match any Unicode newline sequence. The default is specified when
1581           PCRE is built. It can be overridden from within the pattern, or by set-
1582           ting an option when a compiled pattern is matched.
1583    
1584           PCRE_CASELESS           PCRE_CASELESS
1585    
1586         If  this  bit is set, letters in the pattern match both upper and lower         If this bit is set, letters in the pattern match both upper  and  lower
1587         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be         case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
1588         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1589         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1590         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1591         with higher values, the concept of case is supported if  PCRE  is  com-         with  higher  values,  the concept of case is supported if PCRE is com-
1592         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1593         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1594         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1595         UTF-8 support.         UTF-8 support.
1596    
1597           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1598    
1599         If this bit is set, a dollar metacharacter in the pattern matches  only         If  this bit is set, a dollar metacharacter in the pattern matches only
1600         at  the  end  of the subject string. Without this option, a dollar also         at the end of the subject string. Without this option,  a  dollar  also
1601         matches immediately before a newline at the end of the string (but  not         matches  immediately before a newline at the end of the string (but not
1602         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1603         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1604         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1605    
1606           PCRE_DOTALL           PCRE_DOTALL
1607    
1608         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharacter in the pattern matches a  char-
1609         acters, including those that indicate newline. Without it, a  dot  does         acter of any value, including one that indicates a newline. However, it
1610         not  match  when  the  current position is at a newline. This option is         only ever matches one character, even if newlines are  coded  as  CRLF.
1611         equivalent to Perl's /s option, and it can be changed within a  pattern         Without  this option, a dot does not match when the current position is
1612         by  a (?s) option setting. A negative class such as [^a] always matches         at a newline. This option is equivalent to Perl's /s option, and it can
1613         newline characters, independent of the setting of this option.         be  changed within a pattern by a (?s) option setting. A negative class
1614           such as [^a] always matches newline characters, independent of the set-
1615           ting of this option.
1616    
1617           PCRE_DUPNAMES           PCRE_DUPNAMES
1618    
1619         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1620         not be unique. This can be helpful for certain types of pattern when it         not be unique. This can be helpful for certain types of pattern when it
1621         is known that only one instance of the named  subpattern  can  ever  be         is  known  that  only  one instance of the named subpattern can ever be
1622         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1623         the pcrepattern documentation.         the pcrepattern documentation.
1624    
1625           PCRE_EXTENDED           PCRE_EXTENDED
1626    
1627         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1628         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1629         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1630         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1631         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1632         option,  and  it  can be changed within a pattern by a (?x) option set-         option, and it can be changed within a pattern by a  (?x)  option  set-
1633         ting.         ting.
1634    
1635           Which  characters  are  interpreted  as  newlines  is controlled by the
1636           options passed to pcre_compile() or by a special sequence at the  start
1637           of  the  pattern, as described in the section entitled "Newline conven-
1638           tions" in the pcrepattern documentation. Note that the end of this type
1639           of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1640           sequences that happen to represent a newline do not count.
1641    
1642         This option makes it possible to include  comments  inside  complicated         This option makes it possible to include  comments  inside  complicated
1643         patterns.   Note,  however,  that this applies only to data characters.         patterns.   Note,  however,  that this applies only to data characters.
1644         Whitespace  characters  may  never  appear  within  special   character         Whitespace  characters  may  never  appear  within  special   character
1645         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for example within the sequence (?( that intro-
1646         introduces a conditional subpattern.         duces a conditional subpattern.
1647    
1648           PCRE_EXTRA           PCRE_EXTRA
1649    
# Line 1130  COMPILING A PATTERN Line 1653  COMPILING A PATTERN
1653         letter  that  has  no  special  meaning causes an error, thus reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1654         these combinations for future expansion. By  default,  as  in  Perl,  a         these combinations for future expansion. By  default,  as  in  Perl,  a
1655         backslash  followed by a letter with no special meaning is treated as a         backslash  followed by a letter with no special meaning is treated as a
1656         literal. (Perl can, however, be persuaded to give a warning for  this.)         literal. (Perl can, however, be persuaded to give an error for this, by
1657         There  are  at  present no other features controlled by this option. It         running  it with the -w option.) There are at present no other features
1658         can also be set by a (?X) option setting within a pattern.         controlled by this option. It can also be set by a (?X) option  setting
1659           within a pattern.
1660    
1661           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1662    
1663         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1664         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1665         matched text may continue over the newline.         matched text may continue over the newline.
1666    
1667             PCRE_JAVASCRIPT_COMPAT
1668    
1669           If this option is set, PCRE's behaviour is changed in some ways so that
1670           it is compatible with JavaScript rather than Perl. The changes  are  as
1671           follows:
1672    
1673           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1674           error, because this is illegal in JavaScript (by default it is  treated
1675           as a data character). Thus, the pattern AB]CD becomes illegal when this
1676           option is set.
1677    
1678           (2) At run time, a back reference to an unset subpattern group  matches
1679           an  empty  string (by default this causes the current matching alterna-
1680           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1681           set  (assuming  it can find an "a" in the subject), whereas it fails by
1682           default, for Perl compatibility.
1683    
1684           (3) \U matches an upper case "U" character; by default \U causes a com-
1685           pile time error (Perl uses \U to upper case subsequent characters).
1686    
1687           (4) \u matches a lower case "u" character unless it is followed by four
1688           hexadecimal digits, in which case the hexadecimal  number  defines  the
1689           code  point  to match. By default, \u causes a compile time error (Perl
1690           uses it to upper case the following character).
1691    
1692           (5) \x matches a lower case "x" character unless it is followed by  two
1693           hexadecimal  digits,  in  which case the hexadecimal number defines the
1694           code point to match. By default, as in Perl, a  hexadecimal  number  is
1695           always expected after \x, but it may have zero, one, or two digits (so,
1696           for example, \xz matches a binary zero character followed by z).
1697    
1698           PCRE_MULTILINE           PCRE_MULTILINE
1699    
1700         By default, PCRE treats the subject string as consisting  of  a  single         By default, PCRE treats the subject string as consisting  of  a  single
# Line 1173  COMPILING A PATTERN Line 1728  COMPILING A PATTERN
1728         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1729         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1730         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1731         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph  separator, U+2029). For the 8-bit library, the last two are
1732         UTF-8 mode.         recognized only in UTF-8 mode.
1733    
1734         The newline setting in the  options  word  uses  three  bits  that  are         The newline setting in the  options  word  uses  three  bits  that  are
1735         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
# Line 1184  COMPILING A PATTERN Line 1739  COMPILING A PATTERN
1739         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1740         cause an error.         cause an error.
1741    
1742         The only time that a line break is specially recognized when  compiling         The only time that a line break in a pattern  is  specially  recognized
1743         a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a         when  compiling  is when PCRE_EXTENDED is set. CR and LF are whitespace
1744         character class is encountered. This indicates  a  comment  that  lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1745         until  after the next line break sequence. In other circumstances, line         side  a  character class indicates a comment that lasts until after the
1746         break  sequences  are  treated  as  literal  data,   except   that   in         next line break sequence. In other circumstances, line break  sequences
1747         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1748    
1749         The newline option that is set at compile time becomes the default that         The newline option that is set at compile time becomes the default that
1750         is  used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.         is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1751    
1752           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1753    
# Line 1203  COMPILING A PATTERN Line 1757  COMPILING A PATTERN
1757         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1758         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1759    
1760             NO_START_OPTIMIZE
1761    
1762           This is an option that acts at matching time; that is, it is really  an
1763           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1764           time, it is remembered with the compiled pattern and assumed at  match-
1765           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1766           below.
1767    
1768             PCRE_UCP
1769    
1770           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1771           \w,  and  some  of  the POSIX character classes. By default, only ASCII
1772           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1773           are  used instead to classify characters. More details are given in the
1774           section on generic character types in the pcrepattern page. If you  set
1775           PCRE_UCP,  matching  one of the items it affects takes much longer. The
1776           option is available only if PCRE has been compiled with  Unicode  prop-
1777           erty support.
1778    
1779           PCRE_UNGREEDY           PCRE_UNGREEDY
1780    
1781         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1782         are  not greedy by default, but become greedy if followed by "?". It is         are not greedy by default, but become greedy if followed by "?". It  is
1783         not compatible with Perl. It can also be set by a (?U)  option  setting         not  compatible  with Perl. It can also be set by a (?U) option setting
1784         within the pattern.         within the pattern.
1785    
1786           PCRE_UTF8           PCRE_UTF8
1787    
1788         This  option  causes PCRE to regard both the pattern and the subject as         This option causes PCRE to regard both the pattern and the  subject  as
1789         strings of UTF-8 characters instead of single-byte  character  strings.         strings of UTF-8 characters instead of single-byte strings. However, it
1790         However,  it is available only when PCRE is built to include UTF-8 sup-         is available only when PCRE is built to include UTF  support.  If  not,
1791         port. If not, the use of this option provokes an error. Details of  how         the  use  of  this option provokes an error. Details of how this option
1792         this  option  changes the behaviour of PCRE are given in the section on         changes the behaviour of PCRE are given in the pcreunicode page.
        UTF-8 support in the main pcre page.  
1793    
1794           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1795    
1796         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
1797         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
1798         pcre_compile() returns an error. If you already know that your  pattern         UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence  is
1799         is  valid, and you want to skip this check for performance reasons, you         found,  pcre_compile()  returns an error. If you already know that your
1800         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of         pattern is valid, and you want to skip this check for performance  rea-
1801         passing an invalid UTF-8 string as a pattern is undefined. It may cause         sons,  you  can set the PCRE_NO_UTF8_CHECK option.  When it is set, the
1802         your program to crash.  Note that this option can  also  be  passed  to         effect of passing an invalid UTF-8 string as a pattern is undefined. It
1803         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-         may  cause  your  program  to  crash. Note that this option can also be
1804         ing of subject strings.         passed to pcre_exec() and pcre_dfa_exec(),  to  suppress  the  validity
1805           checking of subject strings.
1806    
1807    
1808  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1809    
1810         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
1811         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
1812         both compiling functions. As PCRE has developed, some error codes  have         both  compiling  functions.  Note  that error messages are always 8-bit
1813         fallen out of use. To avoid confusion, they have not been re-used.         ASCII strings, even in 16-bit mode. As PCRE has developed,  some  error
1814           codes  have  fallen  out of use. To avoid confusion, they have not been
1815           re-used.
1816    
1817            0  no error            0  no error
1818            1  \ at end of pattern            1  \ at end of pattern
# Line 1251  COMPILATION ERROR CODES Line 1826  COMPILATION ERROR CODES
1826            9  nothing to repeat            9  nothing to repeat
1827           10  [this code is not in use]           10  [this code is not in use]
1828           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1829           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1830           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1831           14  missing )           14  missing )
1832           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1259  COMPILATION ERROR CODES Line 1834  COMPILATION ERROR CODES
1834           17  unknown option bit(s) set           17  unknown option bit(s) set
1835           18  missing ) after comment           18  missing ) after comment
1836           19  [this code is not in use]           19  [this code is not in use]
1837           20  regular expression too large           20  regular expression is too large
1838           21  failed to get memory           21  failed to get memory
1839           22  unmatched parentheses           22  unmatched parentheses
1840           23  internal error: code overflow           23  internal error: code overflow
# Line 1271  COMPILATION ERROR CODES Line 1846  COMPILATION ERROR CODES
1846           29  (?R or (?[+-]digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1847           30  unknown POSIX class name           30  unknown POSIX class name
1848           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1849           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is compiled without UTF support
1850           33  [this code is not in use]           33  [this code is not in use]
1851           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1852           35  invalid condition (?(0)           35  invalid condition (?(0)
1853           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
1854           37  PCRE does not support \L, \l, \N, \U, or \u           37  PCRE does not support \L, \l, \N{name}, \U, or \u
1855           38  number after (?C is > 255           38  number after (?C is > 255
1856           39  closing ) for (?C expected           39  closing ) for (?C expected
1857           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
1858           41  unrecognized character after (?P           41  unrecognized character after (?P
1859           42  syntax error in subpattern name (missing terminator)           42  syntax error in subpattern name (missing terminator)
1860           43  two named subpatterns have the same name           43  two named subpatterns have the same name
1861           44  invalid UTF-8 string           44  invalid UTF-8 string (specifically UTF-8)
1862           45  support for \P, \p, and \X has not been compiled           45  support for \P, \p, and \X has not been compiled
1863           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1864           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1865           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1866           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1867           50  [this code is not in use]           50  [this code is not in use]
1868           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 in 8-bit non-UTF-8 mode
1869           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1870           53   internal  error:  previously-checked  referenced  subpattern not           53  internal error: previously-checked referenced subpattern
1871         found                 not found
1872           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1873           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1874           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1875           57  \g is not followed by a braced name or an optionally braced           57  \g is not followed by a braced, angle-bracketed, or quoted
1876                 non-zero number                 name/number or by a plain number
1877           58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number           58  a numbered reference must not be zero
1878             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1879             60  (*VERB) not recognized
1880             61  number is too big
1881             62  subpattern name expected
1882             63  digit expected after (?+
1883             64  ] is an invalid data character in JavaScript compatibility mode
1884             65  different names for subpatterns of the same number are
1885                   not allowed
1886             66  (*MARK) must have an argument
1887             67  this version of PCRE is not compiled with Unicode property
1888                   support
1889             68  \c must be followed by an ASCII character
1890             69  \k is not followed by a braced, angle-bracketed, or quoted name
1891             70  internal error: unknown opcode in find_fixedlength()
1892             71  \N is not supported in a class
1893             72  too many forward references
1894             73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
1895             74  invalid UTF-16 string (specifically UTF-16)
1896    
1897           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1898           values may be used if the limits were changed when PCRE was built.
1899    
1900    
1901  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1307  STUDYING A PATTERN Line 1903  STUDYING A PATTERN
1903         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1904              const char **errptr);              const char **errptr);
1905    
1906         If a compiled pattern is going to be used several times,  it  is  worth         If  a  compiled  pattern is going to be used several times, it is worth
1907         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
1908         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1909         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1910         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1911         pointer  to a pcre_extra block, in which the study_data field points to         pointer to a pcre_extra block, in which the study_data field points  to
1912         the results of the study.         the results of the study.
1913    
1914         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1915         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
1916         that can be set by the caller before the block  is  passed;  these  are         tains  other  fields  that can be set by the caller before the block is
1917         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1918    
1919         If  studying  the  pattern  does not produce any additional information         If studying the  pattern  does  not  produce  any  useful  information,
1920         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1921         wants  to  pass  any of the other fields to pcre_exec(), it must set up         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or
1922         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1923    
1924         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument  of  pcre_study() contains option bits. There are
1925         no options are defined, and this argument should always be zero.         three options:
1926    
1927         The  third argument for pcre_study() is a pointer for an error message.           PCRE_STUDY_JIT_COMPILE
1928         If studying succeeds (even if no data is  returned),  the  variable  it           PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
1929         points  to  is  set  to NULL. Otherwise it is set to point to a textual           PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
1930    
1931           If any of these are set, and the just-in-time  compiler  is  available,
1932           the  pattern  is  further compiled into machine code that executes much
1933           faster than the pcre_exec()  interpretive  matching  function.  If  the
1934           just-in-time  compiler is not available, these options are ignored. All
1935           other bits in the options argument must be zero.
1936    
1937           JIT compilation is a heavyweight optimization. It can  take  some  time
1938           for  patterns  to  be analyzed, and for one-off matches and simple pat-
1939           terns the benefit of faster execution might be offset by a much  slower
1940           study time.  Not all patterns can be optimized by the JIT compiler. For
1941           those that cannot be handled, matching automatically falls back to  the
1942           pcre_exec()  interpreter.  For more details, see the pcrejit documenta-
1943           tion.
1944    
1945           The third argument for pcre_study() is a pointer for an error  message.
1946           If  studying  succeeds  (even  if no data is returned), the variable it
1947           points to is set to NULL. Otherwise it is set to  point  to  a  textual
1948         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1949         must  not  try  to  free it. You should test the error pointer for NULL         must not try to free it. You should test the  error  pointer  for  NULL
1950         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1951    
1952         This is a typical call to pcre_study():         When  you are finished with a pattern, you can free the memory used for
1953           the study data by calling pcre_free_study(). This function was added to
1954           the  API  for  release  8.20. For earlier versions, the memory could be
1955           freed with pcre_free(), just like the pattern itself. This  will  still
1956           work  in  cases where JIT optimization is not used, but it is advisable
1957           to change to the new function when convenient.
1958    
1959           This is a typical way in which pcre_study() is used (except that  in  a
1960           real application there should be tests for errors):
1961    
1962           pcre_extra *pe;           int rc;
1963           pe = pcre_study(           pcre *re;
1964             pcre_extra *sd;
1965             re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1966             sd = pcre_study(
1967             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
1968             0,              /* no options exist */             0,              /* no options */
1969             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1970             rc = pcre_exec(   /* see below for details of pcre_exec() options */
1971         At present, studying a pattern is useful only for non-anchored patterns             re, sd, "subject", 7, 0, 0, ovector, 30);
1972         that  do not have a single fixed starting character. A bitmap of possi-           ...
1973         ble starting bytes is created.           pcre_free_study(sd);
1974             pcre_free(re);
1975    
1976           Studying a pattern does two things: first, a lower bound for the length
1977           of subject string that is needed to match the pattern is computed. This
1978           does not mean that there are any strings of that length that match, but
1979           it does guarantee that no shorter strings match. The value is  used  by
1980           pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
1981           match strings that are shorter than the lower bound. You can  find  out
1982           the value in a calling program via the pcre_fullinfo() function.
1983    
1984           Studying a pattern is also useful for non-anchored patterns that do not
1985           have a single fixed starting character. A bitmap of  possible  starting
1986           bytes  is  created. This speeds up finding a position in the subject at
1987           which to start matching. (In 16-bit mode, the bitmap is used for 16-bit
1988           values less than 256.)
1989    
1990           These  two optimizations apply to both pcre_exec() and pcre_dfa_exec(),
1991           and the information is also used by the JIT  compiler.   The  optimiza-
1992           tions can be disabled by setting the PCRE_NO_START_OPTIMIZE option when
1993           calling pcre_exec() or pcre_dfa_exec(), but if this is done, JIT execu-
1994           tion  is  also disabled. You might want to do this if your pattern con-
1995           tains callouts or (*MARK) and you want to make use of these  facilities
1996           in    cases    where    matching   fails.   See   the   discussion   of
1997           PCRE_NO_START_OPTIMIZE below.
1998    
1999    
2000  LOCALE SUPPORT  LOCALE SUPPORT
# Line 1353  LOCALE SUPPORT Line 2002  LOCALE SUPPORT
2002         PCRE handles caseless matching, and determines whether  characters  are         PCRE handles caseless matching, and determines whether  characters  are
2003         letters,  digits, or whatever, by reference to a set of tables, indexed         letters,  digits, or whatever, by reference to a set of tables, indexed
2004         by character value. When running in UTF-8 mode, this  applies  only  to         by character value. When running in UTF-8 mode, this  applies  only  to
2005         characters  with  codes  less than 128. Higher-valued codes never match         characters  with  codes  less than 128. By default, higher-valued codes
2006         escapes such as \w or \d, but can be tested with \p if  PCRE  is  built         never match escapes such as \w or \d, but they can be tested with \p if
2007         with  Unicode  character property support. The use of locales with Uni-         PCRE  is  built with Unicode character property support. Alternatively,
2008         code is discouraged. If you are handling characters with codes  greater         the PCRE_UCP option can be set at compile  time;  this  causes  \w  and
2009         than  128, you should either use UTF-8 and Unicode, or use locales, but         friends to use Unicode property support instead of built-in tables. The
2010         not try to mix the two.         use of locales with Unicode is discouraged. If you are handling charac-
2011           ters  with codes greater than 128, you should either use UTF-8 and Uni-
2012           code, or use locales, but not try to mix the two.
2013    
2014         PCRE contains an internal set of tables that are used  when  the  final         PCRE contains an internal set of tables that are used  when  the  final
2015         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
# Line 1410  INFORMATION ABOUT A PATTERN Line 2061  INFORMATION ABOUT A PATTERN
2061              int what, void *where);              int what, void *where);
2062    
2063         The  pcre_fullinfo() function returns information about a compiled pat-         The  pcre_fullinfo() function returns information about a compiled pat-
2064         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the pcre_info() function, which was removed from  the
2065         less retained for backwards compability (and is documented below).         library at version 8.30, after more than 10 years of obsolescence.
2066    
2067         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
2068         pattern. The second argument is the result of pcre_study(), or NULL  if         pattern. The second argument is the result of pcre_study(), or NULL  if
# Line 1420  INFORMATION ABOUT A PATTERN Line 2071  INFORMATION ABOUT A PATTERN
2071         variable  to  receive  the  data. The yield of the function is zero for         variable  to  receive  the  data. The yield of the function is zero for
2072         success, or one of the following negative numbers:         success, or one of the following negative numbers:
2073    
2074           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL           the argument code was NULL
2075                                 the argument where was NULL                                     the argument where was NULL
2076           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC       the "magic number" was not found
2077           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
2078                                       endianness
2079             PCRE_ERROR_BADOPTION      the value of what was invalid
2080    
2081         The "magic number" is placed at the start of each compiled  pattern  as         The "magic number" is placed at the start of each compiled  pattern  as
2082         an  simple check against passing an arbitrary memory pointer. Here is a         an  simple check against passing an arbitrary memory pointer. The endi-
2083         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         anness error can occur if a compiled pattern is saved and reloaded on a
2084         pattern:         different  host.  Here  is a typical call of pcre_fullinfo(), to obtain
2085           the length of the compiled pattern:
2086    
2087           int rc;           int rc;
2088           size_t length;           size_t length;
2089           rc = pcre_fullinfo(           rc = pcre_fullinfo(
2090             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
2091             pe,               /* result of pcre_study(), or NULL */             sd,               /* result of pcre_study(), or NULL */
2092             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
2093             &length);         /* where to put the data */             &length);         /* where to put the data */
2094    
2095         The  possible  values for the third argument are defined in pcre.h, and         The possible values for the third argument are defined in  pcre.h,  and
2096         are as follows:         are as follows:
2097    
2098           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
2099    
2100         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
2101         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
2102         there are no back references.         there are no back references.
2103    
2104           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
2105    
2106         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
2107         argument should point to an int variable.         argument should point to an int variable.
2108    
2109           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
2110    
2111         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
2112         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
2113         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
2114         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
2115         passing a NULL table pointer.         passing a NULL table pointer.
2116    
2117           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
2118    
2119         Return  information  about  the first byte of any matched string, for a         Return information about the first data unit of any matched string, for
2120         non-anchored pattern. The fourth argument should point to an int  vari-         a  non-anchored  pattern.  (The name of this option refers to the 8-bit
2121         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name         library, where data units are bytes.) The fourth argument should  point
2122         is still recognized for backwards compatibility.)         to an int variable.
2123    
2124           If  there  is  a  fixed first value, for example, the letter "c" from a
2125           pattern such as (cat|cow|coyote), its value is returned. In  the  8-bit
2126           library,  the  value is always less than 256; in the 16-bit library the
2127           value can be up to 0xffff.
2128    
2129         If there is a fixed first byte, for example, from  a  pattern  such  as         If there is no fixed first value, and if either
        (cat|cow|coyote), its value is returned. Otherwise, if either  
2130    
2131         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
2132         branch starts with "^", or         branch starts with "^", or
2133    
2134         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2135         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
2136    
2137         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
2138         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
2139         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
2140    
2141           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
2142    
2143         If  the pattern was studied, and this resulted in the construction of a         If the pattern was studied, and this resulted in the construction of  a
2144         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit  table indicating a fixed set of values for the first data unit
2145         matching  string, a pointer to the table is returned. Otherwise NULL is         in any matching string, a pointer to the table is  returned.  Otherwise
2146         returned. The fourth argument should point to an unsigned char *  vari-         NULL  is returned. The fourth argument should point to an unsigned char
2147         able.         * variable.
2148    
2149             PCRE_INFO_HASCRORLF
2150    
2151           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
2152           characters,  otherwise  0.  The  fourth argument should point to an int
2153           variable. An explicit match is either a literal CR or LF character,  or
2154           \r or \n.
2155    
2156           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
2157    
2158         Return  1  if the (?J) option setting is used in the pattern, otherwise         Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
2159         0. The fourth argument should point to an int variable. The (?J) inter-         otherwise 0. The fourth argument should point to an int variable.  (?J)
2160         nal option setting changes the local PCRE_DUPNAMES option.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
2161    
2162             PCRE_INFO_JIT
2163    
2164           Return  1  if  the pattern was studied with one of the JIT options, and
2165           just-in-time compiling was successful. The fourth argument should point
2166           to  an  int variable. A return value of 0 means that JIT support is not
2167           available in this version of PCRE, or that the pattern was not  studied
2168           with  a JIT option, or that the JIT compiler could not handle this par-
2169           ticular pattern. See the pcrejit documentation for details of what  can
2170           and cannot be handled.
2171    
2172             PCRE_INFO_JITSIZE
2173    
2174           If  the  pattern was successfully studied with a JIT option, return the
2175           size of the JIT compiled code, otherwise return zero. The fourth  argu-
2176           ment should point to a size_t variable.
2177    
2178           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
2179    
2180         Return  the  value of the rightmost literal byte that must exist in any         Return  the value of the rightmost literal data unit that must exist in
2181         matched string, other than at its  start,  if  such  a  byte  has  been         any matched string, other than at its start, if such a value  has  been
2182         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
2183         is no such byte, -1 is returned. For anchored patterns, a last  literal         is no such value, -1 is returned. For anchored patterns, a last literal
2184         byte  is  recorded only if it follows something of variable length. For         value  is recorded only if it follows something of variable length. For
2185         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
2186         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
2187    
2188             PCRE_INFO_MINLENGTH
2189    
2190           If  the  pattern  was studied and a minimum length for matching subject
2191           strings was computed, its value is  returned.  Otherwise  the  returned
2192           value  is  -1. The value is a number of characters, which in UTF-8 mode
2193           may be different from the number of bytes. The fourth  argument  should
2194           point  to an int variable. A non-negative value is a lower bound to the
2195           length of any matching string. There may not be  any  strings  of  that
2196           length  that  do actually match, but every string that does match is at
2197           least that long.
2198    
2199           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
2200           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
2201           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
2202    
2203         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
2204         ses. The names are just an additional way of identifying the  parenthe-         ses.  The names are just an additional way of identifying the parenthe-
2205         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
2206         pcre_get_named_substring() are provided for  extracting  captured  sub-         pcre_get_named_substring()  are  provided  for extracting captured sub-
2207         strings  by  name. It is also possible to extract the data directly, by         strings by name. It is also possible to extract the data  directly,  by
2208         first converting the name to a number in order to  access  the  correct         first  converting  the  name to a number in order to access the correct
2209         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
2210         the conversion, you need  to  use  the  name-to-number  map,  which  is         the  conversion,  you  need  to  use  the  name-to-number map, which is
2211         described by these three values.         described by these three values.
2212    
2213         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
2214         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
2215         of  each  entry;  both  of  these  return  an int value. The entry size         of each entry; both of these  return  an  int  value.  The  entry  size
2216         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
2217         a  pointer  to  the  first  entry of the table (a pointer to char). The         a pointer to the first entry of the table. This is a pointer to char in
2218         first two bytes of each entry are the number of the capturing parenthe-         the 8-bit library, where the first two bytes of each entry are the num-
2219         sis,  most  significant byte first. The rest of the entry is the corre-         ber of the capturing parenthesis, most significant byte first.  In  the
2220         sponding name, zero terminated. The names are  in  alphabetical  order.         16-bit  library,  the pointer points to 16-bit data units, the first of
2221         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-         which contains the parenthesis number. The rest of  the  entry  is  the
2222         theses numbers. For example, consider  the  following  pattern  (assume         corresponding name, zero terminated.
2223         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is  
2224         ignored):         The  names are in alphabetical order. Duplicate names may appear if (?|
2225           is used to create multiple groups with the same number, as described in
2226           the  section  on  duplicate subpattern numbers in the pcrepattern page.
2227           Duplicate names for subpatterns with different  numbers  are  permitted
2228           only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
2229           appear in the table in the order in which they were found in  the  pat-
2230           tern.  In  the  absence  of (?| this is the order of increasing number;
2231           when (?| is used this is not necessarily the case because later subpat-
2232           terns may have lower numbers.
2233    
2234           As  a  simple  example of the name/number table, consider the following
2235           pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is
2236           set, so white space - including newlines - is ignored):
2237    
2238           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
2239           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
2240    
2241         There are four named subpatterns, so the table has  four  entries,  and         There  are  four  named subpatterns, so the table has four entries, and
2242         each  entry  in the table is eight bytes long. The table is as follows,         each entry in the table is eight bytes long. The table is  as  follows,
2243         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
2244         as ??:         as ??:
2245    
# Line 1544  INFORMATION ABOUT A PATTERN Line 2248  INFORMATION ABOUT A PATTERN
2248           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
2249           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
2250    
2251         When  writing  code  to  extract  data from named subpatterns using the         When writing code to extract data  from  named  subpatterns  using  the
2252         name-to-number map, remember that the length of the entries  is  likely         name-to-number  map,  remember that the length of the entries is likely
2253         to be different for each compiled pattern.         to be different for each compiled pattern.
2254    
2255           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
2256    
2257         Return  1 if the pattern can be used for partial matching, otherwise 0.         Return 1  if  the  pattern  can  be  used  for  partial  matching  with
2258         The fourth argument should point to an int  variable.  The  pcrepartial         pcre_exec(),  otherwise  0.  The fourth argument should point to an int
2259         documentation  lists  the restrictions that apply to patterns when par-         variable. From  release  8.00,  this  always  returns  1,  because  the
2260         tial matching is used.         restrictions  that  previously  applied  to  partial matching have been
2261           lifted. The pcrepartial documentation gives details of  partial  match-
2262           ing.
2263    
2264           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
2265    
2266         Return a copy of the options with which the pattern was  compiled.  The         Return  a  copy of the options with which the pattern was compiled. The
2267         fourth  argument  should  point to an unsigned long int variable. These         fourth argument should point to an unsigned long  int  variable.  These
2268         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
2269         by any top-level option settings at the start of the pattern itself. In         by any top-level option settings at the start of the pattern itself. In
2270         other words, they are the options that will be in force  when  matching         other  words,  they are the options that will be in force when matching
2271         starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with         starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
2272         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
2273         and PCRE_EXTENDED.         and PCRE_EXTENDED.
2274    
2275         A  pattern  is  automatically  anchored by PCRE if all of its top-level         A pattern is automatically anchored by PCRE if  all  of  its  top-level
2276         alternatives begin with one of the following:         alternatives begin with one of the following:
2277    
2278           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1580  INFORMATION ABOUT A PATTERN Line 2286  INFORMATION ABOUT A PATTERN
2286    
2287           PCRE_INFO_SIZE           PCRE_INFO_SIZE
2288    
2289         Return  the  size  of the compiled pattern, that is, the value that was         Return the size of the compiled pattern in bytes (for both  libraries).
2290         passed as the argument to pcre_malloc() when PCRE was getting memory in         The  fourth argument should point to a size_t variable. This value does
2291         which to place the compiled data. The fourth argument should point to a         not include the  size  of  the  pcre  structure  that  is  returned  by
2292         size_t variable.         pcre_compile().  The  value that is passed as the argument to pcre_mal-
2293           loc() when pcre_compile() is getting memory in which to place the  com-
2294           piled  data  is  the value returned by this option plus the size of the
2295           pcre structure. Studying a compiled pattern, with or without JIT,  does
2296           not alter the value returned by this option.
2297    
2298           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
2299    
2300         Return the size of the data block pointed to by the study_data field in         Return the size in bytes of the data block pointed to by the study_data
2301         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to         field in a pcre_extra block. If pcre_extra is  NULL,  or  there  is  no
2302         pcre_malloc() when PCRE was getting memory into which to place the data         study  data,  zero  is  returned. The fourth argument should point to a
2303         created  by  pcre_study(). The fourth argument should point to a size_t         size_t variable. The study_data field is set by pcre_study() to  record
2304         variable.         information  that  will  speed  up  matching  (see the section entitled
2305           "Studying a pattern" above). The format of the study_data block is pri-
2306           vate,  but  its length is made available via this option so that it can
2307  OBSOLETE INFO FUNCTION         be  saved  and  restored  (see  the  pcreprecompile  documentation  for
2308           details).
        int pcre_info(const pcre *code, int *optptr, int *firstcharptr);  
   
        The pcre_info() function is now obsolete because its interface  is  too  
        restrictive  to return all the available data about a compiled pattern.  
        New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of  
        pcre_info()  is the number of capturing subpatterns, or one of the fol-  
        lowing negative numbers:  
   
          PCRE_ERROR_NULL       the argument code was NULL  
          PCRE_ERROR_BADMAGIC   the "magic number" was not found  
   
        If the optptr argument is not NULL, a copy of the  options  with  which  
        the  pattern  was  compiled  is placed in the integer it points to (see  
        PCRE_INFO_OPTIONS above).  
   
        If the pattern is not anchored and the  firstcharptr  argument  is  not  
        NULL,  it is used to pass back information about the first character of  
        any matched string (see PCRE_INFO_FIRSTBYTE above).  
2309    
2310    
2311  REFERENCE COUNTS  REFERENCE COUNTS
2312    
2313         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
2314    
2315         The pcre_refcount() function is used to maintain a reference  count  in         The  pcre_refcount()  function is used to maintain a reference count in
2316         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
2317         benefit of applications that  operate  in  an  object-oriented  manner,         benefit  of  applications  that  operate  in an object-oriented manner,
2318         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
2319         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
2320    
2321         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
2322         zero.   It is changed only by calling this function, whose action is to         zero.  It is changed only by calling this function, whose action is  to
2323         add the adjust value (which may be positive or  negative)  to  it.  The         add  the  adjust  value  (which may be positive or negative) to it. The
2324         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
2325         is constrained to lie between 0 and 65535, inclusive. If the new  value         is  constrained to lie between 0 and 65535, inclusive. If the new value
2326         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
2327    
2328         Except  when it is zero, the reference count is not correctly preserved         Except when it is zero, the reference count is not correctly  preserved
2329         if a pattern is compiled on one host and then  transferred  to  a  host         if  a  pattern  is  compiled on one host and then transferred to a host
2330         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
2331    
2332    
# Line 1646  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2338  MATCHING A PATTERN: THE TRADITIONAL FUNC
2338    
2339         The function pcre_exec() is called to match a subject string against  a         The function pcre_exec() is called to match a subject string against  a
2340         compiled  pattern, which is passed in the code argument. If the pattern         compiled  pattern, which is passed in the code argument. If the pattern
2341         has been studied, the result of the study should be passed in the extra         was studied, the result of the study should  be  passed  in  the  extra
2342         argument.  This  function is the main matching facility of the library,         argument.  You  can call pcre_exec() with the same code and extra argu-
2343         and it operates in a Perl-like manner. For specialist use there is also         ments as many times as you like, in order to  match  different  subject
2344         an  alternative matching function, which is described below in the sec-         strings with the same pattern.
2345         tion about the pcre_dfa_exec() function.  
2346           This  function  is  the  main  matching facility of the library, and it
2347           operates in a Perl-like manner. For specialist use  there  is  also  an
2348           alternative  matching function, which is described below in the section
2349           about the pcre_dfa_exec() function.
2350    
2351         In most applications, the pattern will have been compiled (and  option-         In most applications, the pattern will have been compiled (and  option-
2352         ally  studied)  in the same process that calls pcre_exec(). However, it         ally  studied)  in the same process that calls pcre_exec(). However, it
# Line 1682  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2378  MATCHING A PATTERN: THE TRADITIONAL FUNC
2378    
2379           unsigned long int flags;           unsigned long int flags;
2380           void *study_data;           void *study_data;
2381             void *executable_jit;
2382           unsigned long int match_limit;           unsigned long int match_limit;
2383           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
2384           void *callout_data;           void *callout_data;
2385           const unsigned char *tables;           const unsigned char *tables;
2386             unsigned char **mark;
2387    
2388         The flags field is a bitmap that specifies which of  the  other  fields         In the 16-bit version of  this  structure,  the  mark  field  has  type
2389         are set. The flag bits are:         "PCRE_UCHAR16 **".
2390    
2391           PCRE_EXTRA_STUDY_DATA         The  flags  field is used to specify which of the other fields are set.
2392           The flag bits are:
2393    
2394             PCRE_EXTRA_CALLOUT_DATA
2395             PCRE_EXTRA_EXECUTABLE_JIT
2396             PCRE_EXTRA_MARK
2397           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
2398           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
2399           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_STUDY_DATA
2400           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
2401    
2402         Other  flag  bits should be set to zero. The study_data field is set in         Other flag bits should be set to zero. The study_data field  and  some-
2403         the pcre_extra block that is returned by  pcre_study(),  together  with         times  the executable_jit field are set in the pcre_extra block that is
2404         the appropriate flag bit. You should not set this yourself, but you may         returned by pcre_study(), together with the appropriate flag bits.  You
2405         add to the block by setting the other fields  and  their  corresponding         should  not set these yourself, but you may add to the block by setting
2406         flag bits.         other fields and their corresponding flag bits.
2407    
2408         The match_limit field provides a means of preventing PCRE from using up         The match_limit field provides a means of preventing PCRE from using up
2409         a vast amount of resources when running patterns that are not going  to         a  vast amount of resources when running patterns that are not going to
2410         match,  but  which  have  a very large number of possibilities in their         match, but which have a very large number  of  possibilities  in  their
2411         search trees. The classic  example  is  the  use  of  nested  unlimited         search  trees. The classic example is a pattern that uses nested unlim-
2412         repeats.         ited repeats.
2413    
2414         Internally,  PCRE uses a function called match() which it calls repeat-         Internally, pcre_exec() uses a function called match(), which it  calls
2415         edly (sometimes recursively). The limit set by match_limit  is  imposed         repeatedly  (sometimes  recursively).  The  limit set by match_limit is
2416         on  the  number  of times this function is called during a match, which         imposed on the number of times this function is called during a  match,
2417         has the effect of limiting the amount of  backtracking  that  can  take         which  has  the  effect of limiting the amount of backtracking that can
2418         place. For patterns that are not anchored, the count restarts from zero         take place. For patterns that are not anchored, the count restarts from
2419         for each position in the subject string.         zero for each position in the subject string.
2420    
2421           When pcre_exec() is called with a pattern that was successfully studied
2422           with a JIT option, the way that the matching is  executed  is  entirely
2423           different.  However, there is still the possibility of runaway matching
2424           that goes on for a very long time, and so the match_limit value is also
2425           used in this case (but in a different way) to limit how long the match-
2426           ing can continue.
2427    
2428         The default value for the limit can be set  when  PCRE  is  built;  the         The default value for the limit can be set  when  PCRE  is  built;  the
2429         default  default  is 10 million, which handles all but the most extreme         default  default  is 10 million, which handles all but the most extreme
# Line 1728  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2438  MATCHING A PATTERN: THE TRADITIONAL FUNC
2438         the total number of calls, because not all calls to match() are  recur-         the total number of calls, because not all calls to match() are  recur-
2439         sive.  This limit is of use only if it is set smaller than match_limit.         sive.  This limit is of use only if it is set smaller than match_limit.
2440    
2441         Limiting the recursion depth limits the amount of  stack  that  can  be         Limiting  the  recursion  depth limits the amount of machine stack that
2442         used, or, when PCRE has been compiled to use memory on the heap instead         can be used, or, when PCRE has been compiled to use memory on the  heap
2443         of the stack, the amount of heap memory that can be used.         instead  of the stack, the amount of heap memory that can be used. This
2444           limit is not relevant, and is ignored, when matching is done using  JIT
2445         The default value for match_limit_recursion can be  set  when  PCRE  is         compiled code.
2446         built;  the  default  default  is  the  same  value  as the default for  
2447         match_limit. You can override the default by suppling pcre_exec()  with         The  default  value  for  match_limit_recursion can be set when PCRE is
2448         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and         built; the default default  is  the  same  value  as  the  default  for
2449         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the         match_limit.  You can override the default by suppling pcre_exec() with
2450           a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
2451           PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
2452         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2453    
2454         The  pcre_callout  field is used in conjunction with the "callout" fea-         The callout_data field is used in conjunction with the  "callout"  fea-
2455         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2456    
2457         The tables field  is  used  to  pass  a  character  tables  pointer  to         The  tables  field  is  used  to  pass  a  character  tables pointer to
2458         pcre_exec();  this overrides the value that is stored with the compiled         pcre_exec(); this overrides the value that is stored with the  compiled
2459         pattern. A non-NULL value is stored with the compiled pattern  only  if         pattern.  A  non-NULL value is stored with the compiled pattern only if
2460         custom  tables  were  supplied to pcre_compile() via its tableptr argu-         custom tables were supplied to pcre_compile() via  its  tableptr  argu-
2461         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2462         PCRE's  internal  tables  to be used. This facility is helpful when re-         PCRE's internal tables to be used. This facility is  helpful  when  re-
2463         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
2464         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
2465         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
2466         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2467    
2468           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
2469           set  to point to a suitable variable. If the pattern contains any back-
2470           tracking control verbs such as (*MARK:NAME), and the execution ends  up
2471           with  a  name  to  pass back, a pointer to the name string (zero termi-
2472           nated) is placed in the variable pointed to  by  the  mark  field.  The
2473           names  are  within  the  compiled pattern; if you wish to retain such a
2474           name you must copy it before freeing the memory of a compiled  pattern.
2475           If  there  is no name to pass back, the variable pointed to by the mark
2476           field is set to NULL. For details of the  backtracking  control  verbs,
2477           see the section entitled "Backtracking control" in the pcrepattern doc-
2478           umentation.
2479    
2480     Option bits for pcre_exec()     Option bits for pcre_exec()
2481    
2482         The  unused  bits of the options argument for pcre_exec() must be zero.         The unused bits of the options argument for pcre_exec() must  be  zero.
2483         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
2484         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
2485         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_HARD,  and
2486           PCRE_PARTIAL_SOFT.
2487    
2488           If the pattern was successfully studied with one  of  the  just-in-time
2489           (JIT) compile options, the only supported options for JIT execution are
2490           PCRE_NO_UTF8_CHECK,    PCRE_NOTBOL,     PCRE_NOTEOL,     PCRE_NOTEMPTY,
2491           PCRE_NOTEMPTY_ATSTART,  PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an
2492           unsupported option is used, JIT execution is disabled  and  the  normal
2493           interpretive code in pcre_exec() is run.
2494    
2495           PCRE_ANCHORED           PCRE_ANCHORED
2496    
2497         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
2498         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
2499         turned out to be anchored by virtue of its contents, it cannot be  made         turned  out to be anchored by virtue of its contents, it cannot be made
2500         unachored at matching time.         unachored at matching time.
2501    
2502             PCRE_BSR_ANYCRLF
2503             PCRE_BSR_UNICODE
2504    
2505           These options (which are mutually exclusive) control what the \R escape
2506           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
2507           or to match any Unicode newline sequence. These  options  override  the
2508           choice that was made or defaulted when the pattern was compiled.
2509    
2510           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
2511           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
2512           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
# Line 1778  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2518  MATCHING A PATTERN: THE TRADITIONAL FUNC
2518         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion  of  pcre_compile()  above.  During  matching,  the newline choice
2519         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
2520         ters.  It may also alter the way the match position is advanced after a         ters.  It may also alter the way the match position is advanced after a
2521         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
2522         PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY is set, and a match attempt  
2523         fails when the current position is at a CRLF sequence, the match  posi-         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
2524         tion  is  advanced by two characters instead of one, in other words, to         set,  and a match attempt for an unanchored pattern fails when the cur-
2525         after the CRLF.         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
2526           explicit  matches  for  CR  or  LF  characters,  the  match position is
2527           advanced by two characters instead of one, in other words, to after the
2528           CRLF.
2529    
2530           The above rule is a compromise that makes the most common cases work as
2531           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
2532           option is not set), it does not match the string "\r\nA" because, after
2533           failing at the start, it skips both the CR and the LF before  retrying.
2534           However,  the  pattern  [\r\n]A does match that string, because it con-
2535           tains an explicit CR or LF reference, and so advances only by one char-
2536           acter after the first failure.
2537    
2538           An explicit match for CR of LF is either a literal appearance of one of
2539           those characters, or one of the \r or  \n  escape  sequences.  Implicit
2540           matches  such  as [^X] do not count, nor does \s (which includes CR and
2541           LF in the characters that it matches).
2542    
2543           Notwithstanding the above, anomalous effects may still occur when  CRLF
2544           is a valid newline sequence and explicit \r or \n escapes appear in the
2545           pattern.
2546    
2547           PCRE_NOTBOL           PCRE_NOTBOL
2548    
# Line 1810  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2570  MATCHING A PATTERN: THE TRADITIONAL FUNC
2570    
2571           a?b?           a?b?
2572    
2573         is applied to a string not beginning with "a" or "b",  it  matches  the         is applied to a string not beginning with "a" or  "b",  it  matches  an
2574         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
2575         match is not valid, so PCRE searches further into the string for occur-         match is not valid, so PCRE searches further into the string for occur-
2576         rences of "a" or "b".         rences of "a" or "b".
2577    
2578         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2579         cial case of a pattern match of the empty  string  within  its  split()  
2580         function,  and  when  using  the /g modifier. It is possible to emulate         This  is  like PCRE_NOTEMPTY, except that an empty string match that is
2581         Perl's behaviour after matching a null string by first trying the match         not at the start of  the  subject  is  permitted.  If  the  pattern  is
2582         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         anchored, such a match can occur only if the pattern contains \K.
2583         if that fails by advancing the starting offset (see below)  and  trying  
2584         an ordinary match again. There is some code that demonstrates how to do         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2585         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2586           match  of  the empty string within its split() function, and when using
2587           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2588           matching a null string by first trying the match again at the same off-
2589           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2590           fails, by advancing the starting offset (see below) and trying an ordi-
2591           nary match again. There is some code that demonstrates how to  do  this
2592           in  the  pcredemo sample program. In the most general case, you have to
2593           check to see if the newline convention recognizes CRLF  as  a  newline,
2594           and  if so, and the current character is CR followed by LF, advance the
2595           starting offset by two characters instead of one.
2596    
2597             PCRE_NO_START_OPTIMIZE
2598    
2599           There are a number of optimizations that pcre_exec() uses at the  start
2600           of  a  match,  in  order to speed up the process. For example, if it is
2601           known that an unanchored match must start with a specific character, it
2602           searches  the  subject  for that character, and fails immediately if it
2603           cannot find it, without actually running the  main  matching  function.
2604           This means that a special item such as (*COMMIT) at the start of a pat-
2605           tern is not considered until after a suitable starting  point  for  the
2606           match  has been found. When callouts or (*MARK) items are in use, these
2607           "start-up" optimizations can cause them to be skipped if the pattern is
2608           never  actually  used.  The start-up optimizations are in effect a pre-
2609           scan of the subject that takes place before the pattern is run.
2610    
2611           The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,
2612           possibly  causing  performance  to  suffer,  but ensuring that in cases
2613           where the result is "no match", the callouts do occur, and  that  items
2614           such as (*COMMIT) and (*MARK) are considered at every possible starting
2615           position in the subject string. If  PCRE_NO_START_OPTIMIZE  is  set  at
2616           compile  time,  it  cannot  be  unset  at  matching  time.  The  use of
2617           PCRE_NO_START_OPTIMIZE disables JIT execution; when it is set, matching
2618           is always done using interpretively.
2619    
2620           Setting  PCRE_NO_START_OPTIMIZE  can  change  the outcome of a matching
2621           operation.  Consider the pattern
2622    
2623             (*COMMIT)ABC
2624    
2625           When this is compiled, PCRE records the fact that a  match  must  start
2626           with  the  character  "A".  Suppose the subject string is "DEFABC". The
2627           start-up optimization scans along the subject, finds "A" and  runs  the
2628           first  match attempt from there. The (*COMMIT) item means that the pat-
2629           tern must match the current starting position, which in this  case,  it
2630           does.  However,  if  the  same match is run with PCRE_NO_START_OPTIMIZE
2631           set, the initial scan along the subject string  does  not  happen.  The
2632           first  match  attempt  is  run  starting  from "D" and when this fails,
2633           (*COMMIT) prevents any further matches  being  tried,  so  the  overall
2634           result  is  "no  match". If the pattern is studied, more start-up opti-
2635           mizations may be used. For example, a minimum length  for  the  subject
2636           may be recorded. Consider the pattern
2637    
2638             (*MARK:A)(X|Y)
2639    
2640           The  minimum  length  for  a  match is one character. If the subject is
2641           "ABC", there will be attempts to  match  "ABC",  "BC",  "C",  and  then
2642           finally  an empty string.  If the pattern is studied, the final attempt
2643           does not take place, because PCRE knows that the subject is too  short,
2644           and  so  the  (*MARK) is never encountered.  In this case, studying the
2645           pattern does not affect the overall match result, which  is  still  "no
2646           match", but it does affect the auxiliary information that is returned.
2647    
2648           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2649    
2650         When PCRE_UTF8 is set at compile time, the validity of the subject as a         When PCRE_UTF8 is set at compile time, the validity of the subject as a
2651         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
2652         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
2653         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence         points to the start of a UTF-8 character. There is a  discussion  about
2654         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         the  validity  of  UTF-8 strings in the pcreunicode page. If an invalid
2655         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         sequence  of  bytes   is   found,   pcre_exec()   returns   the   error
2656         returned.         PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
2657           truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
2658         If you already know that your subject is valid, and you  want  to  skip         both  cases, information about the precise nature of the error may also
2659         these    checks    for   performance   reasons,   you   can   set   the         be returned (see the descriptions of these errors in the section  enti-
2660         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         tled  Error return values from pcre_exec() below).  If startoffset con-
2661         do  this  for the second and subsequent calls to pcre_exec() if you are         tains a value that does not point to the start of a UTF-8 character (or
2662         making repeated calls to find all  the  matches  in  a  single  subject         to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2663         string.  However,  you  should  be  sure  that the value of startoffset  
2664         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         If  you  already  know that your subject is valid, and you want to skip
2665         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         these   checks   for   performance   reasons,   you   can    set    the
2666         value of startoffset that does not point to the start of a UTF-8  char-         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2667         acter, is undefined. Your program may crash.         do this for the second and subsequent calls to pcre_exec() if  you  are
2668           making  repeated  calls  to  find  all  the matches in a single subject
2669           PCRE_PARTIAL         string. However, you should be  sure  that  the  value  of  startoffset
2670           points  to  the  start of a character (or the end of the subject). When
2671         This  option  turns  on  the  partial  matching feature. If the subject         PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid string as a
2672         string fails to match the pattern, but at some point during the  match-         subject  or  an invalid value of startoffset is undefined. Your program
2673         ing  process  the  end of the subject was reached (that is, the subject         may crash.
2674         partially matches the pattern and the failure to  match  occurred  only  
2675         because  there were not enough subject characters), pcre_exec() returns           PCRE_PARTIAL_HARD
2676         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is           PCRE_PARTIAL_SOFT
2677         used,  there  are restrictions on what may appear in the pattern. These  
2678         are discussed in the pcrepartial documentation.         These options turn on the partial matching feature. For backwards  com-
2679           patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2680           match occurs if the end of the subject string is reached  successfully,
2681           but  there  are not enough subject characters to complete the match. If
2682           this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2683           matching  continues  by  testing any remaining alternatives. Only if no
2684           complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
2685           PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
2686           caller is prepared to handle a partial match, but only if  no  complete
2687           match can be found.
2688    
2689           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this
2690           case, if a partial match  is  found,  pcre_exec()  immediately  returns
2691           PCRE_ERROR_PARTIAL,  without  considering  any  other  alternatives. In
2692           other words, when PCRE_PARTIAL_HARD is set, a partial match is  consid-
2693           ered to be more important that an alternative complete match.
2694    
2695           In  both  cases,  the portion of the string that was inspected when the
2696           partial match was found is set as the first matching string. There is a
2697           more  detailed  discussion  of partial and multi-segment matching, with
2698           examples, in the pcrepartial documentation.
2699    
2700     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2701    
2702         The subject string is passed to pcre_exec() as a pointer in subject,  a         The subject string is passed to pcre_exec() as a pointer in subject,  a
2703         length  in  length, and a starting byte offset in startoffset. In UTF-8         length  in  bytes in length, and a starting byte offset in startoffset.
2704         mode, the byte offset must point to the start  of  a  UTF-8  character.         If this is  negative  or  greater  than  the  length  of  the  subject,
2705         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec()  returns  PCRE_ERROR_BADOFFSET. When the starting offset is
2706         When the starting offset is zero, the search for a match starts at  the         zero, the search for a match starts at the beginning  of  the  subject,
2707         beginning of the subject, and this is by far the most common case.         and this is by far the most common case. In UTF-8 mode, the byte offset
2708           must point to the start of a UTF-8 character (or the end  of  the  sub-
2709         A  non-zero  starting offset is useful when searching for another match         ject).  Unlike  the pattern string, the subject may contain binary zero
2710         in the same subject by calling pcre_exec() again after a previous  suc-         bytes.
2711         cess.   Setting  startoffset differs from just passing over a shortened  
2712         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins         A non-zero starting offset is useful when searching for  another  match
2713           in  the same subject by calling pcre_exec() again after a previous suc-
2714           cess.  Setting startoffset differs from just passing over  a  shortened
2715           string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
2716         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2717    
2718           \Biss\B           \Biss\B
2719    
2720         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
2721         only if the current position in the subject is not  a  word  boundary.)         only  if  the  current position in the subject is not a word boundary.)
2722         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
2723         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
2724         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
2725         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
2726         to  be  a  word  boundary. However, if pcre_exec() is passed the entire         to be a word boundary. However, if pcre_exec()  is  passed  the  entire
2727         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
2728         rence  of "iss" because it is able to look behind the starting point to         rence of "iss" because it is able to look behind the starting point  to
2729         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2730    
2731           Finding  all  the  matches  in a subject is tricky when the pattern can
2732           match an empty string. It is possible to emulate Perl's /g behaviour by
2733           first   trying   the   match   again  at  the  same  offset,  with  the
2734           PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED  options,  and  then  if  that
2735           fails,  advancing  the  starting  offset  and  trying an ordinary match
2736           again. There is some code that demonstrates how to do this in the pcre-
2737           demo sample program. In the most general case, you have to check to see
2738           if the newline convention recognizes CRLF as a newline, and if so,  and
2739           the current character is CR followed by LF, advance the starting offset
2740           by two characters instead of one.
2741    
2742         If a non-zero starting offset is passed when the pattern  is  anchored,         If a non-zero starting offset is passed when the pattern  is  anchored,
2743         one attempt to match at the given offset is made. This can only succeed         one attempt to match at the given offset is made. This can only succeed
2744         if the pattern does not require the match to be at  the  start  of  the         if the pattern does not require the match to be at  the  start  of  the
# Line 1899  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2754  MATCHING A PATTERN: THE TRADITIONAL FUNC
2754         string. PCRE supports several other kinds of  parenthesized  subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
2755         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2756    
2757         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2758         offsets whose address is passed in ovector. The number of  elements  in         whose address is passed in ovector. The number of elements in the  vec-
2759         the  vector is passed in ovecsize, which must be a non-negative number.         tor  is  passed in ovecsize, which must be a non-negative number. Note:
2760         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2761    
2762         The first two-thirds of the vector is used to pass back  captured  sub-         The first two-thirds of the vector is used to pass back  captured  sub-
2763         strings,  each  substring using a pair of integers. The remaining third         strings,  each  substring using a pair of integers. The remaining third
2764         of the vector is used as workspace by pcre_exec() while  matching  cap-         of the vector is used as workspace by pcre_exec() while  matching  cap-
2765         turing  subpatterns, and is not available for passing back information.         turing  subpatterns, and is not available for passing back information.
2766         The length passed in ovecsize should always be a multiple of three.  If         The number passed in ovecsize should always be a multiple of three.  If
2767         it is not, it is rounded down.         it is not, it is rounded down.
2768    
2769         When  a  match  is successful, information about captured substrings is         When  a  match  is successful, information about captured substrings is
2770         returned in pairs of integers, starting at the  beginning  of  ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
2771         and  continuing  up  to two-thirds of its length at the most. The first         and  continuing  up  to two-thirds of its length at the most. The first
2772         element of a pair is set to the offset of the first character in a sub-         element of each pair is set to the byte offset of the  first  character
2773         string,  and  the  second  is  set to the offset of the first character         in  a  substring, and the second is set to the byte offset of the first
2774         after the end of a substring. The  first  pair,  ovector[0]  and  ovec-         character after the end of a substring. Note: these values  are  always
2775         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2776         entire pattern. The next pair is used for the first  capturing  subpat-  
2777         tern, and so on. The value returned by pcre_exec() is one more than the         The  first  pair  of  integers, ovector[0] and ovector[1], identify the
2778         highest numbered pair that has been set. For example, if two substrings         portion of the subject string matched by the entire pattern.  The  next
2779         have  been captured, the returned value is 3. If there are no capturing         pair  is  used for the first capturing subpattern, and so on. The value
2780         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2781         that just the first pair of offsets has been set.         has  been  set.  For example, if two substrings have been captured, the
2782           returned value is 3. If there are no capturing subpatterns, the  return
2783           value from a successful match is 1, indicating that just the first pair
2784           of offsets has been set.
2785    
2786         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2787         of the string that it matched that is returned.         of the string that it matched that is returned.
2788    
2789         If the vector is too small to hold all the captured substring  offsets,         If  the vector is too small to hold all the captured substring offsets,
2790         it is used as far as possible (up to two-thirds of its length), and the         it is used as far as possible (up to two-thirds of its length), and the
2791         function returns a value of zero. In particular, if the substring  off-         function  returns a value of zero. If neither the actual string matched
2792         sets are not of interest, pcre_exec() may be called with ovector passed         not any captured substrings are of interest, pcre_exec() may be  called
2793         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         with  ovector passed as NULL and ovecsize as zero. However, if the pat-
2794         references  and  the  ovector is not big enough to remember the related         tern contains back references and the ovector  is  not  big  enough  to
2795         substrings, PCRE has to get additional memory for use during  matching.         remember  the related substrings, PCRE has to get additional memory for
2796         Thus it is usually advisable to supply an ovector.         use during matching. Thus it is usually advisable to supply an  ovector
2797           of reasonable size.
2798         The  pcre_info()  function  can  be used to find out how many capturing  
2799         subpatterns there are in a compiled  pattern.  The  smallest  size  for         There  are  some  cases where zero is returned (indicating vector over-
2800         ovector  that  will allow for n captured substrings, in addition to the         flow) when in fact the vector is exactly the right size for  the  final
2801           match. For example, consider the pattern
2802    
2803             (a)(?:(b)c|bd)
2804    
2805           If  a  vector of 6 elements (allowing for only 1 captured substring) is
2806           given with subject string "abd", pcre_exec() will try to set the second
2807           captured string, thereby recording a vector overflow, before failing to
2808           match "c" and backing up  to  try  the  second  alternative.  The  zero
2809           return,  however,  does  correctly  indicate that the maximum number of
2810           slots (namely 2) have been filled. In similar cases where there is tem-
2811           porary  overflow,  but  the final number of used slots is actually less
2812           than the maximum, a non-zero value is returned.
2813    
2814           The pcre_fullinfo() function can be used to find out how many capturing
2815           subpatterns  there  are  in  a  compiled pattern. The smallest size for
2816           ovector that will allow for n captured substrings, in addition  to  the
2817         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
2818    
2819         It is possible for capturing subpattern number n+1 to match  some  part         It  is  possible for capturing subpattern number n+1 to match some part
2820         of the subject when subpattern n has not been used at all. For example,         of the subject when subpattern n has not been used at all. For example,
2821         if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the         if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the
2822         return from the function is 4, and subpatterns 1 and 3 are matched, but         return from the function is 4, and subpatterns 1 and 3 are matched, but
2823         2 is not. When this happens, both values in  the  offset  pairs  corre-         2  is  not.  When  this happens, both values in the offset pairs corre-
2824         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2825    
2826         Offset  values  that correspond to unused subpatterns at the end of the         Offset values that correspond to unused subpatterns at the end  of  the
2827         expression are also set to -1. For example,  if  the  string  "abc"  is         expression  are  also  set  to  -1. For example, if the string "abc" is
2828         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not         matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not
2829         matched. The return from the function is 2, because  the  highest  used         matched.  The  return  from the function is 2, because the highest used
2830         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1, and the offsets for  for  the  second
2831         for the second and third capturing subpatterns if  you  wish  (assuming         and  third  capturing subpatterns (assuming the vector is large enough,
2832         the vector is large enough, of course).         of course) are set to -1.
2833    
2834           Note: Elements in the first two-thirds of ovector that  do  not  corre-
2835           spond  to  capturing parentheses in the pattern are never changed. That
2836           is, if a pattern contains n capturing parentheses, no more  than  ovec-
2837           tor[0]  to ovector[2n+1] are set by pcre_exec(). The other elements (in
2838           the first two-thirds) retain whatever values they previously had.
2839    
2840         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
2841         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2842    
2843     Error return values from pcre_exec()     Error return values from pcre_exec()
2844    
2845         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
2846         defined in the header file:         defined in the header file:
2847    
2848           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1971  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2851  MATCHING A PATTERN: THE TRADITIONAL FUNC
2851    
2852           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2853    
2854         Either  code  or  subject  was  passed as NULL, or ovector was NULL and         Either code or subject was passed as NULL,  or  ovector  was  NULL  and
2855         ovecsize was not zero.         ovecsize was not zero.
2856    
2857           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1980  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2860  MATCHING A PATTERN: THE TRADITIONAL FUNC
2860    
2861           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2862    
2863         PCRE stores a 4-byte "magic number" at the start of the compiled  code,         PCRE  stores a 4-byte "magic number" at the start of the compiled code,
2864         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
2865         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
2866         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
2867         gives when the magic number is not present.         gives when the magic number is not present.
2868    
2869           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2870    
2871         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2872         compiled  pattern.  This  error  could be caused by a bug in PCRE or by         compiled pattern. This error could be caused by a bug  in  PCRE  or  by
2873         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2874    
2875           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2876    
2877         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
2878         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2879         PCRE gets a block of memory at the start of matching to  use  for  this         PCRE  gets  a  block of memory at the start of matching to use for this
2880         purpose.  If the call via pcre_malloc() fails, this error is given. The         purpose. If the call via pcre_malloc() fails, this error is given.  The
2881         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2882    
2883           This  error  is also given if pcre_stack_malloc() fails in pcre_exec().
2884           This can happen only when PCRE has been compiled with  --disable-stack-
2885           for-recursion.
2886    
2887           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2888    
2889         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
2890         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2891         returned by pcre_exec().         returned by pcre_exec().
2892    
2893           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2894    
2895         The backtracking limit, as specified by  the  match_limit  field  in  a         The  backtracking  limit,  as  specified  by the match_limit field in a
2896         pcre_extra  structure  (or  defaulted) was reached. See the description         pcre_extra structure (or defaulted) was reached.  See  the  description
2897         above.         above.
2898    
2899           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2900    
2901         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
2902         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
2903         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2904    
2905           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2906    
2907         A string that contains an invalid UTF-8 byte sequence was passed  as  a         A  string  that contains an invalid UTF-8 byte sequence was passed as a
2908         subject.         subject, and the PCRE_NO_UTF8_CHECK option was not set. If the size  of
2909           the  output  vector  (ovecsize)  is  at least 2, the byte offset to the
2910           start of the the invalid UTF-8 character is placed in  the  first  ele-
2911           ment,  and  a  reason  code is placed in the second element. The reason
2912           codes are listed in the following section.  For backward compatibility,
2913           if  PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8 char-
2914           acter  at  the  end  of  the   subject   (reason   codes   1   to   5),
2915           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2916    
2917           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2918    
2919         The UTF-8 byte sequence that was passed as a subject was valid, but the         The  UTF-8  byte  sequence that was passed as a subject was checked and
2920         value of startoffset did not point to the beginning of a UTF-8  charac-         found to be valid (the PCRE_NO_UTF8_CHECK option was not set), but  the
2921         ter.         value  of startoffset did not point to the beginning of a UTF-8 charac-
2922           ter or the end of the subject.
2923    
2924           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2925    
2926         The  subject  string did not match, but it did match partially. See the         The subject string did not match, but it did match partially.  See  the
2927         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2928    
2929           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2930    
2931         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This  code  is  no  longer  in  use.  It was formerly returned when the
2932         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL option was used with a compiled pattern  containing  items
2933         documentation for details of partial matching.         that  were  not  supported  for  partial  matching.  From  release 8.00
2934           onwards, there are no restrictions on partial matching.
2935    
2936           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2937    
# Line 2047  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2940  MATCHING A PATTERN: THE TRADITIONAL FUNC
2940    
2941           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2942    
2943         This  error is given if the value of the ovecsize argument is negative.         This error is given if the value of the ovecsize argument is negative.
2944    
2945           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2946    
2947         The internal recursion limit, as specified by the match_limit_recursion         The internal recursion limit, as specified by the match_limit_recursion
2948         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
2949         description above.         description above.
2950    
2951           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2952    
2953         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2954    
2955             PCRE_ERROR_BADOFFSET      (-24)
2956    
2957           The value of startoffset was negative or greater than the length of the
2958           subject, that is, the value in length.
2959    
2960             PCRE_ERROR_SHORTUTF8      (-25)
2961    
2962           This error is returned instead of PCRE_ERROR_BADUTF8 when  the  subject
2963           string  ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD
2964           option is set.  Information  about  the  failure  is  returned  as  for
2965           PCRE_ERROR_BADUTF8.  It  is in fact sufficient to detect this case, but
2966           this special error code for PCRE_PARTIAL_HARD precedes the  implementa-
2967           tion  of returned information; it is retained for backwards compatibil-
2968           ity.
2969    
2970             PCRE_ERROR_RECURSELOOP    (-26)
2971    
2972           This error is returned when pcre_exec() detects a recursion loop within
2973           the  pattern. Specifically, it means that either the whole pattern or a
2974           subpattern has been called recursively for the second time at the  same
2975           position in the subject string. Some simple patterns that might do this
2976           are detected and faulted at compile time, but more  complicated  cases,
2977           in particular mutual recursions between two different subpatterns, can-
2978           not be detected until run time.
2979    
2980             PCRE_ERROR_JIT_STACKLIMIT (-27)
2981    
2982           This error is returned when a pattern  that  was  successfully  studied
2983           using  a  JIT compile option is being matched, but the memory available
2984           for the just-in-time processing stack is  not  large  enough.  See  the
2985           pcrejit documentation for more details.
2986    
2987             PCRE_ERROR_BADMODE (-28)
2988    
2989           This error is given if a pattern that was compiled by the 8-bit library
2990           is passed to a 16-bit library function, or vice versa.
2991    
2992             PCRE_ERROR_BADENDIANNESS (-29)
2993    
2994           This error is given if  a  pattern  that  was  compiled  and  saved  is
2995           reloaded  on  a  host  with  different endianness. The utility function
2996           pcre_pattern_to_host_byte_order() can be used to convert such a pattern
2997           so that it runs on the new host.
2998    
2999         Error numbers -16 to -20 and -22 are not used by pcre_exec().         Error numbers -16 to -20 and -22 are not used by pcre_exec().
3000    
3001       Reason codes for invalid UTF-8 strings
3002    
3003           This  section  applies  only  to  the  8-bit library. The corresponding
3004           information for the 16-bit library is given in the pcre16 page.
3005    
3006           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
3007           UTF8,  and  the size of the output vector (ovecsize) is at least 2, the
3008           offset of the start of the invalid UTF-8 character  is  placed  in  the
3009           first output vector element (ovector[0]) and a reason code is placed in
3010           the second element (ovector[1]). The reason codes are  given  names  in
3011           the pcre.h header file:
3012    
3013             PCRE_UTF8_ERR1
3014             PCRE_UTF8_ERR2
3015             PCRE_UTF8_ERR3
3016             PCRE_UTF8_ERR4
3017             PCRE_UTF8_ERR5
3018    
3019           The  string  ends  with a truncated UTF-8 character; the code specifies
3020           how many bytes are missing (1 to 5). Although RFC 3629 restricts  UTF-8
3021           characters  to  be  no longer than 4 bytes, the encoding scheme (origi-
3022           nally defined by RFC 2279) allows for  up  to  6  bytes,  and  this  is
3023           checked first; hence the possibility of 4 or 5 missing bytes.
3024    
3025             PCRE_UTF8_ERR6
3026             PCRE_UTF8_ERR7
3027             PCRE_UTF8_ERR8
3028             PCRE_UTF8_ERR9
3029             PCRE_UTF8_ERR10
3030    
3031           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
3032           the character do not have the binary value 0b10 (that  is,  either  the
3033           most significant bit is 0, or the next bit is 1).
3034    
3035             PCRE_UTF8_ERR11
3036             PCRE_UTF8_ERR12
3037    
3038           A  character that is valid by the RFC 2279 rules is either 5 or 6 bytes
3039           long; these code points are excluded by RFC 3629.
3040    
3041             PCRE_UTF8_ERR13
3042    
3043           A 4-byte character has a value greater than 0x10fff; these code  points
3044           are excluded by RFC 3629.
3045    
3046             PCRE_UTF8_ERR14
3047    
3048           A  3-byte  character  has  a  value in the range 0xd800 to 0xdfff; this
3049           range of code points are reserved by RFC 3629 for use with UTF-16,  and
3050           so are excluded from UTF-8.
3051    
3052             PCRE_UTF8_ERR15
3053             PCRE_UTF8_ERR16
3054             PCRE_UTF8_ERR17
3055             PCRE_UTF8_ERR18
3056             PCRE_UTF8_ERR19
3057    
3058           A  2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes
3059           for a value that can be represented by fewer bytes, which  is  invalid.
3060           For  example,  the two bytes 0xc0, 0xae give the value 0x2e, whose cor-
3061           rect coding uses just one byte.
3062    
3063             PCRE_UTF8_ERR20
3064    
3065           The two most significant bits of the first byte of a character have the
3066           binary  value 0b10 (that is, the most significant bit is 1 and the sec-
3067           ond is 0). Such a byte can only validly occur as the second  or  subse-
3068           quent byte of a multi-byte character.
3069    
3070             PCRE_UTF8_ERR21
3071    
3072           The  first byte of a character has the value 0xfe or 0xff. These values
3073           can never occur in a valid UTF-8 string.
3074    
3075    
3076  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
3077    
# Line 2197  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 3208  EXTRACTING CAPTURED SUBSTRINGS BY NAME
3208         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
3209         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
3210    
3211           Warning: If the pattern uses the (?| feature to set up multiple subpat-
3212           terns  with  the  same number, as described in the section on duplicate
3213           subpattern numbers in the pcrepattern page, you  cannot  use  names  to
3214           distinguish  the  different subpatterns, because names are not included
3215           in the compiled code. The matching process uses only numbers. For  this
3216           reason,  the  use of different names for subpatterns of the same number
3217           causes an error at compile time.
3218    
3219    
3220  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
3221    
# Line 2204  DUPLICATE SUBPATTERN NAMES Line 3223  DUPLICATE SUBPATTERN NAMES
3223              const char *name, char **first, char **last);              const char *name, char **first, char **last);
3224    
3225         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for
3226         subpatterns  are  not  required  to  be unique. Normally, patterns with         subpatterns  are not required to be unique. (Duplicate names are always
3227         duplicate names are such that in any one match, only one of  the  named         allowed for subpatterns with the same number, created by using the  (?|
3228         subpatterns  participates. An example is shown in the pcrepattern docu-         feature.  Indeed,  if  such subpatterns are named, they are required to
3229         mentation.         use the same names.)
3230    
3231           Normally, patterns with duplicate names are such that in any one match,
3232           only  one of the named subpatterns participates. An example is shown in
3233           the pcrepattern documentation.
3234    
3235         When   duplicates   are   present,   pcre_copy_named_substring()    and         When   duplicates   are   present,   pcre_copy_named_substring()    and
3236         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring()  return the first substring corresponding to
# Line 2224  DUPLICATE SUBPATTERN NAMES Line 3247  DUPLICATE SUBPATTERN NAMES
3247         the name-to-number table  for  the  given  name.  The  function  itself         the name-to-number table  for  the  given  name.  The  function  itself
3248         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if
3249         there are none. The format of the table is described above in the  sec-         there are none. The format of the table is described above in the  sec-
3250         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion  entitled  Information about a pattern above.  Given all the rele-
3251         entries for the name, you can extract each of their numbers, and  hence         vant entries for the name, you can extract each of their  numbers,  and
3252         the captured data, if any.         hence the captured data, if any.
3253    
3254    
3255  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
# Line 2247  FINDING ALL POSSIBLE MATCHES Line 3270  FINDING ALL POSSIBLE MATCHES
3270         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
3271    
3272    
3273    OBTAINING AN ESTIMATE OF STACK USAGE
3274    
3275           Matching certain patterns using pcre_exec() can use a  lot  of  process
3276           stack,  which  in  certain  environments can be rather limited in size.
3277           Some users find it helpful to have an estimate of the amount  of  stack
3278           that  is  used  by  pcre_exec(),  to help them set recursion limits, as
3279           described in the pcrestack documentation. The estimate that  is  output
3280           by pcretest when called with the -m and -C options is obtained by call-
3281           ing pcre_exec with the values NULL, NULL, NULL, -999, and -999 for  its
3282           first five arguments.
3283    
3284           Normally,  if  its  first  argument  is  NULL,  pcre_exec() immediately
3285           returns the negative error code PCRE_ERROR_NULL, but with this  special
3286           combination  of  arguments,  it returns instead a negative number whose
3287           absolute value is the approximate stack frame size in bytes.  (A  nega-
3288           tive  number  is  used so that it is clear that no match has happened.)
3289           The value is approximate because in  some  cases,  recursive  calls  to
3290           pcre_exec() occur when there are one or two additional variables on the
3291           stack.
3292    
3293           If PCRE has been compiled to use the heap  instead  of  the  stack  for
3294           recursion,  the  value  returned  is  the  size  of  each block that is
3295           obtained from the heap.
3296    
3297    
3298  MATCHING A PATTERN: THE ALTERNATIVE FUNCTION  MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
3299    
3300         int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,         int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
# Line 2260  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 3308  MATCHING A PATTERN: THE ALTERNATIVE FUNC
3308         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics  to  the  normal  algorithm, and is not compatible with
3309         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl. Some of the features of PCRE patterns are not  supported.  Never-
3310         theless,  there are times when this kind of matching can be useful. For         theless,  there are times when this kind of matching can be useful. For
3311         a discussion of the two matching algorithms, see the pcrematching docu-         a discussion of the two matching algorithms, and  a  list  of  features
3312         mentation.         that  pcre_dfa_exec() does not support, see the pcrematching documenta-
3313           tion.
3314    
3315         The  arguments  for  the  pcre_dfa_exec()  function are the same as for         The arguments for the pcre_dfa_exec() function  are  the  same  as  for
3316         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
3317         ent  way,  and  this is described below. The other common arguments are         ent way, and this is described below. The other  common  arguments  are
3318         used in the same way as for pcre_exec(), so their  description  is  not         used  in  the  same way as for pcre_exec(), so their description is not
3319         repeated here.         repeated here.
3320    
3321         The  two  additional  arguments provide workspace for the function. The         The two additional arguments provide workspace for  the  function.  The
3322         workspace vector should contain at least 20 elements. It  is  used  for         workspace  vector  should  contain at least 20 elements. It is used for
3323         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
3324         workspace will be needed for patterns and subjects where  there  are  a         workspace  will  be  needed for patterns and subjects where there are a
3325         lot of potential matches.         lot of potential matches.
3326    
3327         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2294  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 3343  MATCHING A PATTERN: THE ALTERNATIVE FUNC
3343    
3344     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
3345    
3346         The  unused  bits  of  the options argument for pcre_dfa_exec() must be         The unused bits of the options argument  for  pcre_dfa_exec()  must  be
3347         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-
3348         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
3349         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART,       PCRE_NO_UTF8_CHECK,      PCRE_BSR_ANYCRLF,
3350         three of these are the same as for pcre_exec(), so their description is         PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD,  PCRE_PAR-
3351         not repeated here.         TIAL_SOFT,  PCRE_DFA_SHORTEST,  and PCRE_DFA_RESTART.  All but the last
3352           four of these are  exactly  the  same  as  for  pcre_exec(),  so  their
3353           PCRE_PARTIAL         description is not repeated here.
3354    
3355         This has the same general effect as it does for  pcre_exec(),  but  the           PCRE_PARTIAL_HARD
3356         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for           PCRE_PARTIAL_SOFT
3357         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into  
3358         PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have         These  have the same general effect as they do for pcre_exec(), but the
3359         been no complete matches, but there is still at least one matching pos-         details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for
3360         sibility.  The portion of the string that provided the partial match is         pcre_dfa_exec(),  it  returns PCRE_ERROR_PARTIAL if the end of the sub-
3361         set as the first matching string.         ject is reached and there is still at least  one  matching  possibility
3362           that requires additional characters. This happens even if some complete
3363           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
3364           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
3365           of the subject is reached, there have been  no  complete  matches,  but
3366           there  is  still  at least one matching possibility. The portion of the
3367           string that was inspected when the longest partial match was  found  is
3368           set  as  the  first  matching  string  in  both cases.  There is a more
3369           detailed discussion of partial and multi-segment matching,  with  exam-
3370           ples, in the pcrepartial documentation.
3371    
3372           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
3373    
3374         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
3375         stop as soon as it has found one match. Because of the way the alterna-         stop as soon as it has found one match. Because of the way the alterna-
3376         tive algorithm works, this is necessarily the shortest  possible  match         tive  algorithm  works, this is necessarily the shortest possible match
3377         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
3378    
3379           PCRE_DFA_RESTART           PCRE_DFA_RESTART
3380    
3381         When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and         When pcre_dfa_exec() returns a partial match, it is possible to call it
3382         returns a partial match, it is possible to call it  again,  with  addi-         again,  with  additional  subject characters, and have it continue with
3383         tional  subject  characters,  and have it continue with the same match.         the same match. The PCRE_DFA_RESTART option requests this action;  when
3384         The PCRE_DFA_RESTART option requests this action; when it is  set,  the         it  is  set,  the workspace and wscount options must reference the same
3385         workspace  and wscount options must reference the same vector as before         vector as before because data about the match so far is  left  in  them
3386         because data about the match so far is left in  them  after  a  partial         after a partial match. There is more discussion of this facility in the
3387         match.  There  is  more  discussion of this facility in the pcrepartial         pcrepartial documentation.
        documentation.  
3388    
3389     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
3390    
# Line 2361  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 3418  MATCHING A PATTERN: THE ALTERNATIVE FUNC
3418         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
3419         est matching string is given first. If there were too many  matches  to         est matching string is given first. If there were too many  matches  to
3420         fit  into ovector, the yield of the function is zero, and the vector is         fit  into ovector, the yield of the function is zero, and the vector is
3421         filled with the longest matches.         filled with the longest matches.  Unlike  pcre_exec(),  pcre_dfa_exec()
3422           can use the entire ovector for returning matched strings.
3423    
3424     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
3425    
3426         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
3427         Many  of  the  errors  are  the  same as for pcre_exec(), and these are         Many of the errors are the sam