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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.         tern  and pcrecompat pages. There is a syntax summary in the pcresyntax
69           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
# Line 68  USER DOCUMENTATION Line 89  USER DOCUMENTATION
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
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.  
   
        All values in repeating quantifiers must be less than 65536. The  maxi-  
        mum  compiled  length  of  subpattern  with an explicit repeat count is  
        30000 bytes. The maximum number of capturing subpatterns is 65535.  
134    
        There is no limit to the number of parenthesized subpatterns, but there  
        can be no more than 65535 capturing subpatterns.  
135    
136         The maximum length of name for a named subpattern is 32 characters, and  REVISION
        the maximum number of named subpatterns is 10000.  
137    
138         The maximum length of a subject string is the largest  positive  number         Last updated: 10 January 2012
139         that  an integer variable can hold. However, when using the traditional         Copyright (c) 1997-2012 University of Cambridge.
140         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.  
141    
142    
143  UTF-8 AND UNICODE PROPERTY SUPPORT  PCRE(3)                                                                PCRE(3)
144    
        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.  
   
        If you compile PCRE with UTF-8 support, but do not use it at run  time,  
        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.  
145    
146         If PCRE is built with Unicode character property support (which implies  NAME
147         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-         PCRE - Perl-compatible regular expressions
148         ported.  The available properties that can be tested are limited to the  
149         general category properties such as Lu for an upper case letter  or  Nd         #include <pcre.h>
150         for  a  decimal number, the Unicode script names such as Arabic or Han,  
151         and the derived properties Any and L&. A full  list  is  given  in  the  
152         pcrepattern documentation. Only the short names for properties are sup-  PCRE 16-BIT API BASIC FUNCTIONS
153         ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-  
154         ter},  is  not  supported.   Furthermore,  in Perl, many properties may         pcre16 *pcre16_compile(PCRE_SPTR16 pattern, int options,
155         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE              const char **errptr, int *erroffset,
156         does not support this.              const unsigned char *tableptr);
157    
158         The following comments apply when PCRE is running in UTF-8 mode:         pcre16 *pcre16_compile2(PCRE_SPTR16 pattern, int options,
159                int *errorcodeptr,
160         1.  When you set the PCRE_UTF8 flag, the strings passed as patterns and              const char **errptr, int *erroffset,
161         subjects are checked for validity on entry to the  relevant  functions.              const unsigned char *tableptr);
162         If an invalid UTF-8 string is passed, an error return is given. In some  
163         situations, you may already know  that  your  strings  are  valid,  and         pcre16_extra *pcre16_study(const pcre16 *code, int options,
164         therefore want to skip these checks in order to improve performance. If              const char **errptr);
165         you set the PCRE_NO_UTF8_CHECK flag at compile time  or  at  run  time,  
166         PCRE  assumes  that  the  pattern or subject it is given (respectively)         void pcre16_free_study(pcre16_extra *extra);
167         contains only valid UTF-8 codes. In this case, it does not diagnose  an  
168         invalid  UTF-8 string. If you pass an invalid UTF-8 string to PCRE when         int pcre16_exec(const pcre16 *code, const pcre16_extra *extra,
169         PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program  may              PCRE_SPTR16 subject, int length, int startoffset,
170         crash.              int options, int *ovector, int ovecsize);
171    
172         2.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a         int pcre16_dfa_exec(const pcre16 *code, const pcre16_extra *extra,
173         two-byte UTF-8 character if the value is greater than 127.              PCRE_SPTR16 subject, int length, int startoffset,
174                int options, int *ovector, int ovecsize,
175         3. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8              int *workspace, int wscount);
176         characters for values greater than \177.  
177    
178         4.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-  PCRE 16-BIT API STRING EXTRACTION FUNCTIONS
179         vidual bytes, for example: \x{100}{3}.  
180           int pcre16_copy_named_substring(const pcre16 *code,
181         5. The dot metacharacter matches one UTF-8 character instead of a  sin-              PCRE_SPTR16 subject, int *ovector,
182         gle byte.              int stringcount, PCRE_SPTR16 stringname,
183                PCRE_UCHAR16 *buffer, int buffersize);
184         6.  The  escape sequence \C can be used to match a single byte in UTF-8  
185         mode, but its use can lead to some strange effects.  This  facility  is         int pcre16_copy_substring(PCRE_SPTR16 subject, int *ovector,
186         not available in the alternative matching function, pcre_dfa_exec().              int stringcount, int stringnumber, PCRE_UCHAR16 *buffer,
187                int buffersize);
188         7.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly  
189         test characters of any code value, but the characters that PCRE  recog-         int pcre16_get_named_substring(const pcre16 *code,
190         nizes  as  digits,  spaces,  or  word characters remain the same set as              PCRE_SPTR16 subject, int *ovector,
191         before, all with values less than 256. This remains true even when PCRE              int stringcount, PCRE_SPTR16 stringname,
192         includes  Unicode  property support, because to do otherwise would slow              PCRE_SPTR16 *stringptr);
193         down PCRE in many common cases. If you really want to test for a  wider  
194         sense  of,  say,  "digit",  you must use Unicode property tests such as         int pcre16_get_stringnumber(const pcre16 *code,
195         \p{Nd}.              PCRE_SPTR16 name);
196    
197         8. Similarly, characters that match the POSIX named  character  classes         int pcre16_get_stringtable_entries(const pcre16 *code,
198         are all low-valued characters.              PCRE_SPTR16 name, PCRE_UCHAR16 **first, PCRE_UCHAR16 **last);
199    
200         9.  Case-insensitive  matching  applies only to characters whose values         int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector,
201         are less than 128, unless PCRE is built with Unicode property  support.              int stringcount, int stringnumber,
202         Even  when  Unicode  property support is available, PCRE still uses its              PCRE_SPTR16 *stringptr);
203         own character tables when checking the case of  low-valued  characters,  
204         so  as not to degrade performance.  The Unicode property information is         int pcre16_get_substring_list(PCRE_SPTR16 subject,
205         used only for characters with higher values. Even when Unicode property              int *ovector, int stringcount, PCRE_SPTR16 **listptr);
206         support is available, PCRE supports case-insensitive matching only when  
207         there is a one-to-one mapping between a letter's  cases.  There  are  a         void pcre16_free_substring(PCRE_SPTR16 stringptr);
208         small  number  of  many-to-one  mappings in Unicode; these are not sup-  
209         ported by PCRE.         void pcre16_free_substring_list(PCRE_SPTR16 *stringptr);
210    
211    
212    PCRE 16-BIT API AUXILIARY FUNCTIONS
213    
214           pcre16_jit_stack *pcre16_jit_stack_alloc(int startsize, int maxsize);
215    
216           void pcre16_jit_stack_free(pcre16_jit_stack *stack);
217    
218           void pcre16_assign_jit_stack(pcre16_extra *extra,
219                pcre16_jit_callback callback, void *data);
220    
221           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. There is a discussion about
371           the validity of UTF-16 strings in the pcreunicode page.
372    
373           For the pcre16_config() function there is an  option  PCRE_CONFIG_UTF16
374           that  returns  1  if UTF-16 support is configured, otherwise 0. If this
375           option is given to pcre_config(), or if the PCRE_CONFIG_UTF8 option  is
376           given to pcre16_config(), the result is the PCRE_ERROR_BADOPTION error.
377    
378    
379    CHARACTER CODES
380    
381           In  16-bit  mode,  when  PCRE_UTF16  is  not  set, character values are
382           treated in the same way as in 8-bit, non UTF-8 mode, except, of course,
383           that  they  can  range from 0 to 0xffff instead of 0 to 0xff. Character
384           types for characters less than 0xff can therefore be influenced by  the
385           locale  in  the  same way as before.  Characters greater than 0xff have
386           only one case, and no "type" (such as letter or digit).
387    
388           In UTF-16 mode, the character code  is  Unicode,  in  the  range  0  to
389           0x10ffff,  with  the  exception of values in the range 0xd800 to 0xdfff
390           because those are "surrogate" values that are used in pairs  to  encode
391           values greater than 0xffff.
392    
393           A  UTF-16 string can indicate its endianness by special code knows as a
394           byte-order mark (BOM). The PCRE functions do not handle this, expecting
395           strings   to   be  in  host  byte  order.  A  utility  function  called
396           pcre16_utf16_to_host_byte_order() is provided to help  with  this  (see
397           above).
398    
399    
400    ERROR NAMES
401    
402           The  errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16 corre-
403           spond to their 8-bit  counterparts.  The  error  PCRE_ERROR_BADMODE  is
404           given  when  a  compiled pattern is passed to a function that processes
405           patterns in the other mode, for example, if  a  pattern  compiled  with
406           pcre_compile() is passed to pcre16_exec().
407    
408           There  are  new  error  codes whose names begin with PCRE_UTF16_ERR for
409           invalid UTF-16 strings, corresponding to the  PCRE_UTF8_ERR  codes  for
410           UTF-8  strings that are described in the section entitled "Reason codes
411           for invalid UTF-8 strings" in the main pcreapi page. The UTF-16  errors
412           are:
413    
414             PCRE_UTF16_ERR1  Missing low surrogate at end of string
415             PCRE_UTF16_ERR2  Invalid low surrogate follows high surrogate
416             PCRE_UTF16_ERR3  Isolated low surrogate
417             PCRE_UTF16_ERR4  Invalid character 0xfffe
418    
419    
420    ERROR TEXTS
421    
422           If  there is an error while compiling a pattern, the error text that is
423           passed back by pcre16_compile() or pcre16_compile2() is still an  8-bit
424           character string, zero-terminated.
425    
426    
427    CALLOUTS
428    
429           The  subject  and  mark fields in the callout block that is passed to a
430           callout function point to 16-bit vectors.
431    
432    
433    TESTING
434    
435           The pcretest program continues to operate with 8-bit input  and  output
436           files,  but it can be used for testing the 16-bit library. If it is run
437           with the command line option -16, patterns and subject strings are con-
438           verted from 8-bit to 16-bit before being passed to PCRE, and the 16-bit
439           library functions are used instead of the 8-bit ones.  Returned  16-bit
440           strings are converted to 8-bit for output. If the 8-bit library was not
441           compiled, pcretest defaults to 16-bit and the -16 option is ignored.
442    
443           When PCRE is being built, the RunTest script that is  called  by  "make
444           check"  uses  the pcretest -C option to discover which of the 8-bit and
445           16-bit libraries has been built, and runs the tests appropriately.
446    
447    
448    NOT SUPPORTED IN 16-BIT MODE
449    
450           Not all the features of the 8-bit library are available with the 16-bit
451           library.  The  C++  and  POSIX wrapper functions support only the 8-bit
452           library, and the pcregrep program is at present 8-bit only.
453    
454    
455  AUTHOR  AUTHOR
# Line 215  AUTHOR Line 458  AUTHOR
458         University Computing Service         University Computing Service
459         Cambridge CB2 3QH, England.         Cambridge CB2 3QH, England.
460    
        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.  
   
461    
462  REVISION  REVISION
463    
464         Last updated: 18 April 2007         Last updated: 14 April 2012
465         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
466  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
467    
468    
# Line 237  NAME Line 476  NAME
476  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
477    
478         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
479         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
480         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
481         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
482         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
483         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
484           instead of configure to build PCRE.
485    
486           There  is  a  lot more information about building PCRE in non-Unix-like
487           environments in the file called NON_UNIX_USE, which is part of the PCRE
488           distribution.  You  should consult this file as well as the README file
489           if you are building in a non-Unix-like environment.
490    
491           The complete list of options for configure (which includes the standard
492           ones  such  as  the  selection  of  the  installation directory) can be
493           obtained by running
494    
495           ./configure --help           ./configure --help
496    
# Line 253  PCRE BUILD-TIME OPTIONS Line 502  PCRE BUILD-TIME OPTIONS
502         is not described.         is not described.
503    
504    
505    BUILDING 8-BIT and 16-BIT LIBRARIES
506    
507           By  default,  a  library  called libpcre is built, containing functions
508           that take string arguments contained in vectors  of  bytes,  either  as
509           single-byte  characters,  or interpreted as UTF-8 strings. You can also
510           build a separate library, called libpcre16, in which strings  are  con-
511           tained  in  vectors of 16-bit data units and interpreted either as sin-
512           gle-unit characters or UTF-16 strings, by adding
513    
514             --enable-pcre16
515    
516           to the configure command. If you do not want the 8-bit library, add
517    
518             --disable-pcre8
519    
520           as well. At least one of the two libraries must be built. Note that the
521           C++  and  POSIX wrappers are for the 8-bit library only, and that pcre-
522           grep is an 8-bit program. None of these are built if  you  select  only
523           the 16-bit library.
524    
525    
526    BUILDING SHARED AND STATIC LIBRARIES
527    
528           The  PCRE building process uses libtool to build both shared and static
529           Unix libraries by default. You can suppress one of these by adding  one
530           of
531    
532             --disable-shared
533             --disable-static
534    
535           to the configure command, as required.
536    
537    
538  C++ SUPPORT  C++ SUPPORT
539    
540         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
541         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,
542         library for PCRE. You can disable this by adding         it  automatically  builds  the C++ wrapper library (which supports only
543           8-bit strings). You can disable this by adding
544    
545           --disable-cpp           --disable-cpp
546    
547         to the configure command.         to the configure command.
548    
549    
550  UTF-8 SUPPORT  UTF-8 and UTF-16 SUPPORT
551    
552         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF Unicode character strings, add
553    
554           --enable-utf8           --enable-utf
555    
556         to  the  configure  command.  Of  itself, this does not make PCRE treat         to the configure command.  This  setting  applies  to  both  libraries,
557         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
558         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
559         function.         and  UTF-16  independently because that would allow ridiculous settings
560           such as  requesting  UTF-16  support  while  building  only  the  8-bit
561           library.  It  is not possible to build one library with UTF support and
562           the other without in the same configuration. (For backwards compatibil-
563           ity, --enable-utf8 is a synonym of --enable-utf.)
564    
565           Of  itself,  this  setting does not make PCRE treat strings as UTF-8 or
566           UTF-16. As well as compiling PCRE with this option, you also have  have
567           to set the PCRE_UTF8 or PCRE_UTF16 option when you call one of the pat-
568           tern compiling functions.
569    
570           If you set --enable-utf when compiling in an EBCDIC  environment,  PCRE
571           expects  its  input  to be either ASCII or UTF-8 (depending on the run-
572           time option). It is not possible to support both EBCDIC and UTF-8 codes
573           in  the  same  version  of  the library. Consequently, --enable-utf and
574           --enable-ebcdic are mutually exclusive.
575    
576    
577  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
578    
579         UTF-8 support allows PCRE to process character values greater than  255         UTF support allows the libraries to process character codepoints up  to
580         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
581         vide any facilities for accessing the properties of such characters. If         not provide any facilities for accessing the properties of such charac-
582         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,
583         refer to Unicode character properties, you must add         which refer to Unicode character properties, you must add
584    
585           --enable-unicode-properties           --enable-unicode-properties
586    
587         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
588         not explicitly requested it.         not explicitly requested it.
589    
590         Including  Unicode  property  support  adds around 30K of tables to the         Including  Unicode  property  support  adds around 30K of tables to the
# Line 294  UNICODE CHARACTER PROPERTY SUPPORT Line 592  UNICODE CHARACTER PROPERTY SUPPORT
592         are supported. Details are given in the pcrepattern documentation.         are supported. Details are given in the pcrepattern documentation.
593    
594    
595    JUST-IN-TIME COMPILER SUPPORT
596    
597           Just-in-time compiler support is included in the build by specifying
598    
599             --enable-jit
600    
601           This  support  is available only for certain hardware architectures. If
602           this option is set for an  unsupported  architecture,  a  compile  time
603           error  occurs.   See  the pcrejit documentation for a discussion of JIT
604           usage. When JIT support is enabled, pcregrep automatically makes use of
605           it, unless you add
606    
607             --disable-pcregrep-jit
608    
609           to the "configure" command.
610    
611    
612  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
613    
614         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
615         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
616         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
617         instead, by adding         adding
618    
619           --enable-newline-is-cr           --enable-newline-is-cr
620    
# Line 322  CODE VALUE OF NEWLINE Line 637  CODE VALUE OF NEWLINE
637    
638         causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
639    
640         Whatever line ending convention is selected when PCRE is built  can  be         Whatever  line  ending convention is selected when PCRE is built can be
641         overridden  when  the library functions are called. At build time it is         overridden when the library functions are called. At build time  it  is
642         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
643    
644    
645  BUILDING SHARED AND STATIC LIBRARIES  WHAT \R MATCHES
646    
647         The PCRE building process uses libtool to build both shared and  static         By  default,  the  sequence \R in a pattern matches any Unicode newline
648         Unix  libraries by default. You can suppress one of these by adding one         sequence, whatever has been selected as the line  ending  sequence.  If
649         of         you specify
650    
651           --disable-shared           --enable-bsr-anycrlf
          --disable-static  
652    
653         to the configure command, as required.         the  default  is changed so that \R matches only CR, LF, or CRLF. What-
654           ever is selected when PCRE is built can be overridden when the  library
655           functions are called.
656    
657    
658  POSIX MALLOC USAGE  POSIX MALLOC USAGE
659    
660         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
661         umentation),  additional  working  storage  is required for holding the         pcreposix documentation), additional working storage  is  required  for
662         pointers to capturing substrings, because PCRE requires three  integers         holding  the  pointers  to  capturing substrings, because PCRE requires
663         per  substring,  whereas  the POSIX interface provides only two. If the         three integers per substring, whereas the POSIX interface provides only
664         number of expected substrings is small, the wrapper function uses space         two.  If  the number of expected substrings is small, the wrapper func-
665         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-
666         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
667         can be changed by adding a setting such as         longer used is 10; it can be changed by adding a setting such as
668    
669           --with-posix-malloc-threshold=20           --with-posix-malloc-threshold=20
670    
# Line 357  POSIX MALLOC USAGE Line 673  POSIX MALLOC USAGE
673    
674  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
675    
676         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
677         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
678         nation  metacharacter).  By default, two-byte values are used for these         nation metacharacter). By default, two-byte values are used  for  these
679         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets,  leading  to  a  maximum size for a compiled pattern of around
680         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
681         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless,  some  people do want to process truly enormous patterns,
682         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-
683         adding a setting such as         sets by adding a setting such as
684    
685           --with-link-size=3           --with-link-size=3
686    
687         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
688         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
689         additional bytes when handling them.         slows down the operation of PCRE because it has to load additional data
690           when handling them.
691    
692    
693  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
# Line 390  AVOIDING EXCESSIVE STACK USAGE Line 707  AVOIDING EXCESSIVE STACK USAGE
707    
708         to  the  configure  command. With this configuration, PCRE will use the         to  the  configure  command. With this configuration, PCRE will use the
709         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-
710         ment  functions.  Separate  functions are provided because the usage is         ment  functions. By default these point to malloc() and free(), but you
711         very predictable: the block sizes requested are always  the  same,  and         can replace the pointers so that your own functions are used instead.
712         the  blocks  are always freed in reverse order. A calling program might  
713         be able to implement optimized functions that perform better  than  the         Separate functions are  provided  rather  than  using  pcre_malloc  and
714         standard  malloc()  and  free()  functions.  PCRE  runs noticeably more         pcre_free  because  the  usage  is  very  predictable:  the block sizes
715         slowly when built in this way. This option affects only the pcre_exec()         requested are always the same, and  the  blocks  are  always  freed  in
716         function; it is not relevant for the the pcre_dfa_exec() function.         reverse  order.  A calling program might be able to implement optimized
717           functions that perform better  than  malloc()  and  free().  PCRE  runs
718           noticeably more slowly when built in this way. This option affects only
719           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
720    
721    
722  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
723    
724         Internally,  PCRE has a function called match(), which it calls repeat-         Internally, PCRE has a function called match(), which it calls  repeat-
725         edly  (sometimes  recursively)  when  matching  a  pattern   with   the         edly   (sometimes   recursively)  when  matching  a  pattern  with  the
726         pcre_exec()  function.  By controlling the maximum number of times this         pcre_exec() function. By controlling the maximum number of  times  this
727         function may be called during a single matching operation, a limit  can         function  may be called during a single matching operation, a limit can
728         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
729         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-
730         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
731         setting such as         setting such as
732    
733           --with-match-limit=500000           --with-match-limit=500000
734    
735         to  the  configure  command.  This  setting  has  no  effect   on   the         to   the   configure  command.  This  setting  has  no  effect  on  the
736         pcre_dfa_exec() matching function.         pcre_dfa_exec() matching function.
737    
738         In  some  environments  it is desirable to limit the depth of recursive         In some environments it is desirable to limit the  depth  of  recursive
739         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
740         to  restrict  the maximum amount of stack (or heap, if --disable-stack-         to restrict the maximum amount of stack (or heap,  if  --disable-stack-
741         for-recursion is specified) that is used. A second limit controls this;         for-recursion is specified) that is used. A second limit controls this;
742         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
743         imposes no additional constraints. However, you can set a  lower  limit         imposes  no  additional constraints. However, you can set a lower limit
744         by adding, for example,         by adding, for example,
745    
746           --with-match-limit-recursion=10000           --with-match-limit-recursion=10000
747    
748         to  the  configure  command.  This  value can also be overridden at run         to the configure command. This value can  also  be  overridden  at  run
749         time.         time.
750    
751    
752  CREATING CHARACTER TABLES AT BUILD TIME  CREATING CHARACTER TABLES AT BUILD TIME
753    
754         PCRE uses fixed tables for processing characters whose code values  are         PCRE  uses fixed tables for processing characters whose code values are
755         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
756         distributed in the file pcre_chartables.c.dist. These  tables  are  for         distributed  in  the  file pcre_chartables.c.dist. These tables are for
757         ASCII codes only. If you add         ASCII codes only. If you add
758    
759           --enable-rebuild-chartables           --enable-rebuild-chartables
760    
761         to  the  configure  command, the distributed tables are no longer used.         to the configure command, the distributed tables are  no  longer  used.
762         Instead, a program called dftables is compiled and  run.  This  outputs         Instead,  a  program  called dftables is compiled and run. This outputs
763         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
764         C runtime system. (This method of replacing the tables does not work if         C  run-time  system. (This method of replacing the tables does not work
765         you  are cross compiling, because dftables is run on the local host. If         if you are cross compiling, because dftables is run on the local  host.
766         you need to create alternative tables when cross  compiling,  you  will         If you need to create alternative tables when cross compiling, you will
767         have to do so "by hand".)         have to do so "by hand".)
768    
769    
770  USING EBCDIC CODE  USING EBCDIC CODE
771    
772         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
773         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
774         PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by         This is the case for most computer operating systems.  PCRE  can,  how-
775         adding         ever, be compiled to run in an EBCDIC environment by adding
776    
777           --enable-ebcdic           --enable-ebcdic
778    
779         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
780         bles.         bles. You should only use it if you know that  you  are  in  an  EBCDIC
781           environment  (for  example,  an  IBM  mainframe  operating system). The
782           --enable-ebcdic option is incompatible with --enable-utf.
783    
784    
785    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
786    
787           By default, pcregrep reads all files as plain text. You can build it so
788           that it recognizes files whose names end in .gz or .bz2, and reads them
789           with libz or libbz2, respectively, by adding one or both of
790    
791             --enable-pcregrep-libz
792             --enable-pcregrep-libbz2
793    
794           to the configure command. These options naturally require that the rel-
795           evant  libraries  are installed on your system. Configuration will fail
796           if they are not.
797    
798    
799    PCREGREP BUFFER SIZE
800    
801           pcregrep uses an internal buffer to hold a "window" on the file  it  is
802           scanning, in order to be able to output "before" and "after" lines when
803           it finds a match. The size of the buffer is controlled by  a  parameter
804           whose default value is 20K. The buffer itself is three times this size,
805           but because of the way it is used for holding "before" lines, the long-
806           est  line  that  is guaranteed to be processable is the parameter size.
807           You can change the default parameter value by adding, for example,
808    
809             --with-pcregrep-bufsize=50K
810    
811           to the configure command. The caller of pcregrep can, however, override
812           this value by specifying a run-time option.
813    
814    
815    PCRETEST OPTION FOR LIBREADLINE SUPPORT
816    
817           If you add
818    
819             --enable-pcretest-libreadline
820    
821           to  the  configure  command,  pcretest  is  linked with the libreadline
822           library, and when its input is from a terminal, it reads it  using  the
823           readline() function. This provides line-editing and history facilities.
824           Note that libreadline is GPL-licensed, so if you distribute a binary of
825           pcretest linked in this way, there may be licensing issues.
826    
827           Setting  this  option  causes  the -lreadline option to be added to the
828           pcretest build. In many operating environments with  a  sytem-installed
829           libreadline this is sufficient. However, in some environments (e.g.  if
830           an unmodified distribution version of readline is in use),  some  extra
831           configuration  may  be necessary. The INSTALL file for libreadline says
832           this:
833    
834             "Readline uses the termcap functions, but does not link with the
835             termcap or curses library itself, allowing applications which link
836             with readline the to choose an appropriate library."
837    
838           If your environment has not been set up so that an appropriate  library
839           is automatically included, you may need to add something like
840    
841             LIBS="-ncurses"
842    
843           immediately before the configure command.
844    
845    
846  SEE ALSO  SEE ALSO
847    
848         pcreapi(3), pcre_config(3).         pcreapi(3), pcre16, pcre_config(3).
849    
850    
851  AUTHOR  AUTHOR
# Line 474  AUTHOR Line 857  AUTHOR
857    
858  REVISION  REVISION
859    
860         Last updated: 16 April 2007         Last updated: 07 January 2012
861         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
862  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
863    
864    
# Line 491  PCRE MATCHING ALGORITHMS Line 874  PCRE MATCHING ALGORITHMS
874         This document describes the two different algorithms that are available         This document describes the two different algorithms that are available
875         in PCRE for matching a compiled regular expression against a given sub-         in PCRE for matching a compiled regular expression against a given sub-
876         ject  string.  The  "standard"  algorithm  is  the  one provided by the         ject  string.  The  "standard"  algorithm  is  the  one provided by the
877         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
878         function, and provides a Perl-compatible matching operation.         Perl's matching function, and provide a Perl-compatible matching opera-
879           tion. The just-in-time (JIT) optimization  that  is  described  in  the
880         An  alternative  algorithm is provided by the pcre_dfa_exec() function;         pcrejit documentation is compatible with these functions.
881         this operates in a different way, and is not  Perl-compatible.  It  has  
882         advantages  and disadvantages compared with the standard algorithm, and         An  alternative  algorithm  is  provided  by  the  pcre_dfa_exec()  and
883         these are described below.         pcre16_dfa_exec() functions; they operate in a different way,  and  are
884           not  Perl-compatible. This alternative has advantages and disadvantages
885           compared with the standard algorithm, and these are described below.
886    
887         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
888         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 562  THE ALTERNATIVE MATCHING ALGORITHM Line 947  THE ALTERNATIVE MATCHING ALGORITHM
947         though  it is not implemented as a traditional finite state machine (it         though  it is not implemented as a traditional finite state machine (it
948         keeps multiple states active simultaneously).         keeps multiple states active simultaneously).
949    
950           Although the general principle of this matching algorithm  is  that  it
951           scans  the subject string only once, without backtracking, there is one
952           exception: when a lookaround assertion is encountered,  the  characters
953           following  or  preceding  the  current  point  have to be independently
954           inspected.
955    
956         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
957         there  are  no more unterminated paths. At this point, terminated paths         there  are  no more unterminated paths. At this point, terminated paths
958         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
959         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
960         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-
961         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
962         match (which is necessarily the shortest) has been found.         an option to stop the algorithm after the first match (which is  neces-
963           sarily the shortest) is found.
964    
965         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
966         subject. If the pattern         subject. If the pattern
967    
968           cat(er(pillar)?)           cat(er(pillar)?)?
969    
970         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
971         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
972         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
973         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
974    
975         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
976         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
977    
978         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
979         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
980         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
981         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
982         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
983    
984           ^a++\w!           ^a++\w!
985    
986         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
987         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
988         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,
989         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
990         pattern.         pattern.
991    
992         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
993         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
994         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
995         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-
996         strings are available.         strings are available.
997    
998         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
999         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
1000    
1001         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
1002         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
1003         supported.         supported.
1004    
1005         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
1006         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
1007         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
1008         error if encountered.         error if encountered.
1009    
1010         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
1011         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.
1012    
1013         7.  The \C escape sequence, which (in the standard algorithm) matches a         7.  The  \C  escape  sequence, which (in the standard algorithm) always
1014         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-
1015         tive algorithm moves through the subject  string  one  character  at  a         ported  in these modes, because the alternative algorithm moves through
1016         time, for all active paths through the tree.         the subject string one character (not data unit) at  a  time,  for  all
1017           active paths through the tree.
1018    
1019           8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
1020           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
1021           negative assertion.
1022    
1023    
1024  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 634  ADVANTAGES OF THE ALTERNATIVE ALGORITHM Line 1031  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
1031         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
1032         things with callouts.         things with callouts.
1033    
1034         2.  There is much better support for partial matching. The restrictions         2.  Because  the  alternative  algorithm  scans the subject string just
1035         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-
1036         rithm  for  partial matching do not apply to the alternative algorithm.         sible  to  pass  very  long subject strings to the matching function in
1037         For non-anchored patterns, the starting position of a partial match  is         several pieces, checking for partial matching each time. Although it is
1038         available.         possible  to  do multi-segment matching using the standard algorithm by
1039           retaining partially matched substrings, it  is  more  complicated.  The
1040         3.  Because  the  alternative  algorithm  scans the subject string just         pcrepartial  documentation  gives  details of partial matching and dis-
1041         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.  
1042    
1043    
1044  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 669  AUTHOR Line 1064  AUTHOR
1064    
1065  REVISION  REVISION
1066    
1067         Last updated: 29 May 2007         Last updated: 08 January 2012
1068         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
1069  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
1070    
1071    
# Line 680  PCREAPI(3) Line 1075  PCREAPI(3)
1075  NAME  NAME
1076         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
1077    
1078           #include <pcre.h>
1079    
 PCRE NATIVE API  
1080    
1081         #include <pcre.h>  PCRE NATIVE API BASIC FUNCTIONS
1082    
1083         pcre *pcre_compile(const char *pattern, int options,         pcre *pcre_compile(const char *pattern, int options,
1084              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
# Line 697  PCRE NATIVE API Line 1092  PCRE NATIVE API
1092         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
1093              const char **errptr);              const char **errptr);
1094    
1095           void pcre_free_study(pcre_extra *extra);
1096    
1097         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
1098              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1099              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
# Line 706  PCRE NATIVE API Line 1103  PCRE NATIVE API
1103              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
1104              int *workspace, int wscount);              int *workspace, int wscount);
1105    
1106    
1107    PCRE NATIVE API STRING EXTRACTION FUNCTIONS
1108    
1109         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
1110              const char *subject, int *ovector,              const char *subject, int *ovector,
1111              int stringcount, const char *stringname,              int stringcount, const char *stringname,
# Line 737  PCRE NATIVE API Line 1137  PCRE NATIVE API
1137    
1138         void pcre_free_substring_list(const char **stringptr);         void pcre_free_substring_list(const char **stringptr);
1139    
1140    
1141    PCRE NATIVE API AUXILIARY FUNCTIONS
1142    
1143           pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);
1144    
1145           void pcre_jit_stack_free(pcre_jit_stack *stack);
1146    
1147           void pcre_assign_jit_stack(pcre_extra *extra,
1148                pcre_jit_callback callback, void *data);
1149    
1150         const unsigned char *pcre_maketables(void);         const unsigned char *pcre_maketables(void);
1151    
1152         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1153              int what, void *where);              int what, void *where);
1154    
        int pcre_info(const pcre *code, int *optptr, int *firstcharptr);  
   
1155         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1156    
1157         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1158    
1159         char *pcre_version(void);         const char *pcre_version(void);
1160    
1161           int pcre_pattern_to_host_byte_order(pcre *code,
1162                pcre_extra *extra, const unsigned char *tables);
1163    
1164    
1165    PCRE NATIVE API INDIRECTED FUNCTIONS
1166    
1167         void *(*pcre_malloc)(size_t);         void *(*pcre_malloc)(size_t);
1168    
# Line 761  PCRE NATIVE API Line 1175  PCRE NATIVE API
1175         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
1176    
1177    
1178    PCRE 8-BIT AND 16-BIT LIBRARIES
1179    
1180           From  release  8.30,  PCRE  can  be  compiled as a library for handling
1181           16-bit character strings as  well  as,  or  instead  of,  the  original
1182           library that handles 8-bit character strings. To avoid too much compli-
1183           cation, this document describes the 8-bit versions  of  the  functions,
1184           with only occasional references to the 16-bit library.
1185    
1186           The  16-bit  functions  operate in the same way as their 8-bit counter-
1187           parts; they just use different  data  types  for  their  arguments  and
1188           results, and their names start with pcre16_ instead of pcre_. For every
1189           option that has UTF8 in its name (for example, PCRE_UTF8), there  is  a
1190           corresponding 16-bit name with UTF8 replaced by UTF16. This facility is
1191           in fact just cosmetic; the 16-bit option names define the same bit val-
1192           ues.
1193    
1194           References to bytes and UTF-8 in this document should be read as refer-
1195           ences to 16-bit data  quantities  and  UTF-16  when  using  the  16-bit
1196           library,  unless specified otherwise. More details of the specific dif-
1197           ferences for the 16-bit library are given in the pcre16 page.
1198    
1199    
1200  PCRE API OVERVIEW  PCRE API OVERVIEW
1201    
1202         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
1203         are also some wrapper functions that correspond to  the  POSIX  regular         are  also some wrapper functions (for the 8-bit library only) that cor-
1204         expression  API.  These  are  described in the pcreposix documentation.         respond to the POSIX regular expression  API,  but  they  do  not  give
1205         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
1206         distributed with PCRE. It is documented in the pcrecpp page.         documentation. Both of these APIs define a set of C function  calls.  A
1207           C++ wrapper (again for the 8-bit library only) is also distributed with
1208         The  native  API  C  function prototypes are defined in the header file         PCRE. It is documented in the pcrecpp page.
1209         pcre.h, and on Unix systems the library itself is called  libpcre.   It  
1210         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
1211         application  that  uses  PCRE.  The  header  file  defines  the  macros         pcre.h,  and  on Unix-like systems the (8-bit) library itself is called
1212         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
1213         bers for the library.  Applications can use these  to  include  support         for  linking an application that uses PCRE. The header file defines the
1214           macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release
1215           numbers  for the library. Applications can use these to include support
1216         for different releases of PCRE.         for different releases of PCRE.
1217    
1218         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         In a Windows environment, if you want to statically link an application
1219         pcre_exec() are used for compiling and matching regular expressions  in         program  against  a  non-dll  pcre.a  file, you must define PCRE_STATIC
1220         a  Perl-compatible  manner. A sample program that demonstrates the sim-         before including pcre.h or pcrecpp.h, because otherwise  the  pcre_mal-
1221         plest way of using them is provided in the file  called  pcredemo.c  in         loc()   and   pcre_free()   exported   functions   will   be   declared
1222         the  source distribution. The pcresample documentation describes how to         __declspec(dllimport), with unwanted results.
1223         run it.  
1224           The  functions  pcre_compile(),  pcre_compile2(),   pcre_study(),   and
1225           pcre_exec()  are used for compiling and matching regular expressions in
1226           a Perl-compatible manner. A sample program that demonstrates  the  sim-
1227           plest  way  of  using them is provided in the file called pcredemo.c in
1228           the PCRE source distribution. A listing of this program is given in the
1229           pcredemo  documentation, and the pcresample documentation describes how
1230           to compile and run it.
1231    
1232           Just-in-time compiler support is an optional feature of PCRE  that  can
1233           be built in appropriate hardware environments. It greatly speeds up the
1234           matching performance of  many  patterns.  Simple  programs  can  easily
1235           request  that  it  be  used  if available, by setting an option that is
1236           ignored when it is not relevant. More complicated programs  might  need
1237           to     make    use    of    the    functions    pcre_jit_stack_alloc(),
1238           pcre_jit_stack_free(), and pcre_assign_jit_stack() in order to  control
1239           the  JIT  code's  memory  usage.   These functions are discussed in the
1240           pcrejit documentation.
1241    
1242         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
1243         ble,  is  also provided. This uses a different algorithm for the match-         ble,  is  also provided. This uses a different algorithm for the match-
1244         ing. The alternative algorithm finds all possible matches (at  a  given         ing. The alternative algorithm finds all possible matches (at  a  given
1245         point  in  the subject), and scans the subject just once. However, this         point  in  the  subject), and scans the subject just once (unless there
1246         algorithm does not return captured substrings. A description of the two         are lookbehind assertions). However, this  algorithm  does  not  return
1247         matching  algorithms and their advantages and disadvantages is given in         captured  substrings.  A description of the two matching algorithms and
1248         the pcrematching documentation.         their advantages and disadvantages is given in the  pcrematching  docu-
1249           mentation.
1250    
1251         In addition to the main compiling and  matching  functions,  there  are         In  addition  to  the  main compiling and matching functions, there are
1252         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
1253         string that is matched by pcre_exec(). They are:         string that is matched by pcre_exec(). They are:
1254    
# Line 807  PCRE API OVERVIEW Line 1263  PCRE API OVERVIEW
1263         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
1264         to free the memory used for extracted strings.         to free the memory used for extracted strings.
1265    
1266         The  function  pcre_maketables()  is  used  to build a set of character         The function pcre_maketables() is used to  build  a  set  of  character
1267         tables  in  the  current  locale   for   passing   to   pcre_compile(),         tables   in   the   current   locale  for  passing  to  pcre_compile(),
1268         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
1269         provided for specialist use.  Most  commonly,  no  special  tables  are         provided  for  specialist  use.  Most  commonly,  no special tables are
1270         passed,  in  which case internal tables that are generated when PCRE is         passed, in which case internal tables that are generated when  PCRE  is
1271         built are used.         built are used.
1272    
1273         The function pcre_fullinfo() is used to find out  information  about  a         The  function  pcre_fullinfo()  is used to find out information about a
1274         compiled  pattern; pcre_info() is an obsolete version that returns only         compiled pattern. The function pcre_version() returns a  pointer  to  a
1275         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.  
1276    
1277         The function pcre_refcount() maintains a  reference  count  in  a  data         The  function  pcre_refcount()  maintains  a  reference count in a data
1278         block  containing  a compiled pattern. This is provided for the benefit         block containing a compiled pattern. This is provided for  the  benefit
1279         of object-oriented applications.         of object-oriented applications.
1280    
1281         The global variables pcre_malloc and pcre_free  initially  contain  the         The  global  variables  pcre_malloc and pcre_free initially contain the
1282         entry  points  of  the  standard malloc() and free() functions, respec-         entry points of the standard malloc()  and  free()  functions,  respec-
1283         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
1284         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
1285         calls. This should be done before calling any PCRE functions.         calls. This should be done before calling any PCRE functions.
1286    
1287         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also         The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
1288         indirections  to  memory  management functions. These special functions         indirections to memory management functions.  These  special  functions
1289         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
1290         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
1291         function. See the pcrebuild documentation for  details  of  how  to  do         function.  See  the  pcrebuild  documentation  for details of how to do
1292         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-
1293         ments that have limited stacks. Because of the greater  use  of  memory         ments  that  have  limited stacks. Because of the greater use of memory
1294         management,  it  runs  more  slowly. Separate functions are provided so         management, it runs more slowly. Separate  functions  are  provided  so
1295         that special-purpose external code can be  used  for  this  case.  When         that  special-purpose  external  code  can  be used for this case. When
1296         used,  these  functions  are always called in a stack-like manner (last         used, these functions are always called in a  stack-like  manner  (last
1297         obtained, first freed), and always for memory blocks of the same  size.         obtained,  first freed), and always for memory blocks of the same size.
1298         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-
1299         mentation.         mentation.
1300    
1301         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
1302         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
1303         specified points during a matching operation. Details are given in  the         specified  points during a matching operation. Details are given in the
1304         pcrecallout documentation.         pcrecallout documentation.
1305    
1306    
1307  NEWLINES  NEWLINES
1308    
1309         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
1310         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
1311         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
1312         ceding, or any Unicode newline sequence. The Unicode newline  sequences         ceding,  or any Unicode newline sequence. The Unicode newline sequences
1313         are  the  three just mentioned, plus the single characters VT (vertical         are the three just mentioned, plus the single characters  VT  (vertical
1314         tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line         tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line
1315         separator, U+2028), and PS (paragraph separator, U+2029).         separator, U+2028), and PS (paragraph separator, U+2029).
1316    
1317         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
1318         system as its standard newline sequence. When PCRE is built, a  default         system  as its standard newline sequence. When PCRE is built, a default
1319         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-
1320         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
1321         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
1322    
1323           At compile time, the newline convention can be specified by the options
1324           argument  of  pcre_compile(), or it can be specified by special text at
1325           the start of the pattern itself; this overrides any other settings. See
1326           the pcrepattern page for details of the special character sequences.
1327    
1328         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-
1329         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
1330         newline  convention  affects  the  handling of the dot, circumflex, and         newline  convention  affects  the  handling of the dot, circumflex, and
1331         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
1332         CRLF  is a recognized line ending sequence, the match position advance-         CRLF  is a recognized line ending sequence, the match position advance-
1333         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
1334         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
1335    
1336           The  choice of newline convention does not affect the interpretation of
1337           the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
1338           which is controlled in a similar way, but by separate options.
1339    
1340    
1341  MULTITHREADING  MULTITHREADING
# Line 882  MULTITHREADING Line 1345  MULTITHREADING
1345         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
1346         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
1347    
1348         The  compiled form of a regular expression is not altered during match-         The compiled form of a regular expression is not altered during  match-
1349         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
1350         at once.         at once.
1351    
1352           If the just-in-time optimization feature is being used, it needs  sepa-
1353           rate  memory stack areas for each thread. See the pcrejit documentation
1354           for more details.
1355    
1356    
1357  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
1358    
1359         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
1360         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
1361         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
1362         pcreprecompile documentation. However, compiling a  regular  expression         pcreprecompile  documentation,  which  includes  a  description  of the
1363         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-
1364         anteed to work and may cause crashes.         lar  expression  with one version of PCRE for use with a different ver-
1365           sion is not guaranteed to work and may cause crashes.
1366    
1367    
1368  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 908  CHECKING BUILD-TIME OPTIONS Line 1376  CHECKING BUILD-TIME OPTIONS
1376    
1377         The  first  argument  for pcre_config() is an integer, specifying which         The  first  argument  for pcre_config() is an integer, specifying which
1378         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
1379         into  which  the  information  is  placed. The following information is         into  which  the  information  is placed. The returned value is zero on
1380           success, or the negative error code PCRE_ERROR_BADOPTION if  the  value
1381           in  the  first argument is not recognized. The following information is
1382         available:         available:
1383    
1384           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
1385    
1386         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-
1387         able; otherwise it is set to zero.         able;  otherwise  it  is  set  to  zero. If this option is given to the
1388           16-bit  version  of  this  function,  pcre16_config(),  the  result  is
1389           PCRE_ERROR_BADOPTION.
1390    
1391             PCRE_CONFIG_UTF16
1392    
1393           The output is an integer that is set to one if UTF-16 support is avail-
1394           able; otherwise it is set to zero. This value should normally be  given
1395           to the 16-bit version of this function, pcre16_config(). If it is given
1396           to the 8-bit version of this function, the result is  PCRE_ERROR_BADOP-
1397           TION.
1398    
1399           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
1400    
1401         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
1402         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1403    
1404             PCRE_CONFIG_JIT
1405    
1406           The output is an integer that is set to one if support for just-in-time
1407           compiling is available; otherwise it is set to zero.
1408    
1409             PCRE_CONFIG_JITTARGET
1410    
1411           The  output is a pointer to a zero-terminated "const char *" string. If
1412           JIT support is available, the string contains the name of the architec-
1413           ture  for  which the JIT compiler is configured, for example "x86 32bit
1414           (little endian + unaligned)". If JIT  support  is  not  available,  the
1415           result is NULL.
1416    
1417           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1418    
1419         The output is an integer whose value specifies  the  default  character         The  output  is  an integer whose value specifies the default character
1420         sequence  that is recognized as meaning "newline". The four values that         sequence that is recognized as meaning "newline". The four values  that
1421         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,
1422         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
1423         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1424           spond to the standard sequence for your operating system.
1425    
1426             PCRE_CONFIG_BSR
1427    
1428           The output is an integer whose value indicates what character sequences
1429           the  \R  escape sequence matches by default. A value of 0 means that \R
1430           matches any Unicode line ending sequence; a value of 1  means  that  \R
1431           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1432           tern is compiled or matched.
1433    
1434           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1435    
1436         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
1437         internal linkage in compiled regular expressions. The value is 2, 3, or         internal  linkage  in  compiled  regular  expressions.  For  the  8-bit
1438         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
1439         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
1440         for all but the most massive patterns, since  it  allows  the  compiled         is sufficient for all but the most massive patterns,  since  it  allows
1441         pattern to be up to 64K in size.         the  compiled  pattern  to  be  up to 64K in size.  Larger values allow
1442           larger regular expressions to be compiled, at  the  expense  of  slower
1443           matching.
1444    
1445           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1446    
# Line 946  CHECKING BUILD-TIME OPTIONS Line 1450  CHECKING BUILD-TIME OPTIONS
1450    
1451           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1452    
1453         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-
1454         internal matching function calls in a  pcre_exec()  execution.  Further         ber of internal matching function calls  in  a  pcre_exec()  execution.
1455         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1456    
1457           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1458    
1459         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
1460         recursion when calling the internal matching function in a  pcre_exec()         of  recursion  when  calling  the  internal  matching  function  in   a
1461         execution. Further details are given with pcre_exec() below.         pcre_exec()  execution.  Further  details  are  given  with pcre_exec()
1462           below.
1463    
1464           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1465    
1466         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
1467         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1468         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
1469         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
1470         on  the  heap  instead  of  recursive  function  calls.  In  this case,         on the  heap  instead  of  recursive  function  calls.  In  this  case,
1471         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
1472         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1473    
1474    
# Line 980  COMPILING A PATTERN Line 1485  COMPILING A PATTERN
1485    
1486         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1487         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1488         the  two interfaces is that pcre_compile2() has an additional argument,         the two interfaces is that pcre_compile2() has an additional  argument,
1489         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr,  via  which  a  numerical  error code can be returned. To
1490           avoid too much repetition, we refer just to pcre_compile()  below,  but
1491           the information applies equally to pcre_compile2().
1492    
1493         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
1494         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
1495         obtained via pcre_malloc is returned. This contains the  compiled  code         obtained  via  pcre_malloc is returned. This contains the compiled code
1496         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
1497         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1498         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
1499         longer required.         longer required.
1500    
1501         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
1502         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
1503         fully relocatable, because it may contain a copy of the tableptr  argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
1504         ment, which is an address (see below).         ment, which is an address (see below).
1505    
1506         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1507         pilation. It should be zero if no options are required.  The  available         pilation.  It  should be zero if no options are required. The available
1508         options  are  described  below. Some of them, in particular, those that         options are described below. Some of them (in  particular,  those  that
1509         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
1510         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset from within the pattern (see  the  detailed  description  in  the
1511         tion). For these options, the contents of the options  argument  speci-         pcrepattern  documentation). For those options that can be different in
1512         fies  their initial settings at the start of compilation and execution.         different parts of the pattern, the contents of  the  options  argument
1513         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
1514         of matching as well as at compile time.         PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK,  and
1515           PCRE_NO_START_OPTIMIZE  options  can  be set at the time of matching as
1516           well as at compile time.
1517    
1518         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1519         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1520         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-
1521         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
1522         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
1523         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
1524         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
1525         given.         (if  it is, an immediate error is given). However, for an invalid UTF-8
1526           string, the offset is that of the first byte of the failing character.
1527         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-  
1528         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;
1529         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.
1530           Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1531           It may sometimes point into the middle of a UTF-8 character.
1532    
1533           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1534           codeptr argument is not NULL, a non-zero error code number is  returned
1535           via  this argument in the event of an error. This is in addition to the
1536         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1537    
1538         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
1539         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1540         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1541         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
1542         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1543         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
1544         support below.         support below.
1545    
1546         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1547         pile():         pile():
1548    
1549           pcre *re;           pcre *re;
# Line 1041  COMPILING A PATTERN Line 1556  COMPILING A PATTERN
1556             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1557             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1558    
1559         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
1560         file:         file:
1561    
1562           PCRE_ANCHORED           PCRE_ANCHORED
1563    
1564         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
1565         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
1566         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1567         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1568         only way to do it in Perl.         only way to do it in Perl.
1569    
1570           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1571    
1572         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1573         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1574         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1575    
1576             PCRE_BSR_ANYCRLF
1577             PCRE_BSR_UNICODE
1578    
1579           These options (which are mutually exclusive) control what the \R escape
1580           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1581           or to match any Unicode newline sequence. The default is specified when
1582           PCRE is built. It can be overridden from within the pattern, or by set-
1583           ting an option when a compiled pattern is matched.
1584    
1585           PCRE_CASELESS           PCRE_CASELESS
1586    
1587         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
1588         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
1589         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
1590         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1591         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1592         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-
1593         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1594         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1595         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1596         UTF-8 support.         UTF-8 support.
1597    
1598           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1599    
1600         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
1601         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
1602         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
1603         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1604         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
1605         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1606    
1607           PCRE_DOTALL           PCRE_DOTALL
1608    
1609         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-
1610         acters, including those that indicate newline. Without it, a  dot  does         acter of any value, including one that indicates a newline. However, it
1611         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.
1612         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
1613         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
1614         newline characters, independent of the setting of this option.         be  changed within a pattern by a (?s) option setting. A negative class
1615           such as [^a] always matches newline characters, independent of the set-
1616           ting of this option.
1617    
1618           PCRE_DUPNAMES           PCRE_DUPNAMES
1619    
1620         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1621         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
1622         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
1623         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1624         the pcrepattern documentation.         the pcrepattern documentation.
1625    
1626           PCRE_EXTENDED           PCRE_EXTENDED
1627    
1628         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  white space data characters in the pattern are
1629         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class.  White
1630         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1631         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1632         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1633         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-
1634         ting.         ting.
1635    
1636           Which  characters  are  interpreted  as  newlines  is controlled by the
1637           options passed to pcre_compile() or by a special sequence at the  start
1638           of  the  pattern, as described in the section entitled "Newline conven-
1639           tions" in the pcrepattern documentation. Note that the end of this type
1640           of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1641           sequences that happen to represent a newline do not count.
1642    
1643         This option makes it possible to include  comments  inside  complicated         This option makes it possible to include  comments  inside  complicated
1644         patterns.   Note,  however,  that this applies only to data characters.         patterns.   Note,  however,  that this applies only to data characters.
1645         Whitespace  characters  may  never  appear  within  special   character         White space  characters  may  never  appear  within  special  character
1646         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for example within the sequence (?( that intro-
1647         introduces a conditional subpattern.         duces a conditional subpattern.
1648    
1649           PCRE_EXTRA           PCRE_EXTRA
1650    
# Line 1121  COMPILING A PATTERN Line 1654  COMPILING A PATTERN
1654         letter  that  has  no  special  meaning causes an error, thus reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1655         these combinations for future expansion. By  default,  as  in  Perl,  a         these combinations for future expansion. By  default,  as  in  Perl,  a
1656         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
1657         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
1658         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
1659         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
1660           within a pattern.
1661    
1662           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1663    
1664         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1665         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1666         matched text may continue over the newline.         matched text may continue over the newline.
1667    
1668             PCRE_JAVASCRIPT_COMPAT
1669    
1670           If this option is set, PCRE's behaviour is changed in some ways so that
1671           it is compatible with JavaScript rather than Perl. The changes  are  as
1672           follows:
1673    
1674           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1675           error, because this is illegal in JavaScript (by default it is  treated
1676           as a data character). Thus, the pattern AB]CD becomes illegal when this
1677           option is set.
1678    
1679           (2) At run time, a back reference to an unset subpattern group  matches
1680           an  empty  string (by default this causes the current matching alterna-
1681           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1682           set  (assuming  it can find an "a" in the subject), whereas it fails by
1683           default, for Perl compatibility.
1684    
1685           (3) \U matches an upper case "U" character; by default \U causes a com-
1686           pile time error (Perl uses \U to upper case subsequent characters).
1687    
1688           (4) \u matches a lower case "u" character unless it is followed by four
1689           hexadecimal digits, in which case the hexadecimal  number  defines  the
1690           code  point  to match. By default, \u causes a compile time error (Perl
1691           uses it to upper case the following character).
1692    
1693           (5) \x matches a lower case "x" character unless it is followed by  two
1694           hexadecimal  digits,  in  which case the hexadecimal number defines the
1695           code point to match. By default, as in Perl, a  hexadecimal  number  is
1696           always expected after \x, but it may have zero, one, or two digits (so,
1697           for example, \xz matches a binary zero character followed by z).
1698    
1699           PCRE_MULTILINE           PCRE_MULTILINE
1700    
1701         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 1162  COMPILING A PATTERN Line 1727  COMPILING A PATTERN
1727         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1728         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1729         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1730         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus  the  single  characters VT (vertical tab, U+000B), FF (form feed,
1731         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
1732         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph  separator, U+2029). For the 8-bit library, the last two are
1733         UTF-8 mode.         recognized only in UTF-8 mode.
1734    
1735         The newline setting in the  options  word  uses  three  bits  that  are         The newline setting in the  options  word  uses  three  bits  that  are
1736         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
# Line 1175  COMPILING A PATTERN Line 1740  COMPILING A PATTERN
1740         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1741         cause an error.         cause an error.
1742    
1743         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
1744         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 white space
1745         character class is encountered. This indicates  a  comment  that  lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1746         until  after the next line break sequence. In other circumstances, line         side  a  character class indicates a comment that lasts until after the
1747         break  sequences  are  treated  as  literal  data,   except   that   in         next line break sequence. In other circumstances, line break  sequences
1748         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1749    
1750         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
1751         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.
1752    
1753           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1754    
# Line 1194  COMPILING A PATTERN Line 1758  COMPILING A PATTERN
1758         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1759         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1760    
1761             NO_START_OPTIMIZE
1762    
1763           This is an option that acts at matching time; that is, it is really  an
1764           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1765           time, it is remembered with the compiled pattern and assumed at  match-
1766           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1767           below.
1768    
1769             PCRE_UCP
1770    
1771           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1772           \w,  and  some  of  the POSIX character classes. By default, only ASCII
1773           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1774           are  used instead to classify characters. More details are given in the
1775           section on generic character types in the pcrepattern page. If you  set
1776           PCRE_UCP,  matching  one of the items it affects takes much longer. The
1777           option is available only if PCRE has been compiled with  Unicode  prop-
1778           erty support.
1779    
1780           PCRE_UNGREEDY           PCRE_UNGREEDY
1781    
1782         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1783         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
1784         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
1785         within the pattern.         within the pattern.
1786    
1787           PCRE_UTF8           PCRE_UTF8
1788    
1789         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
1790         strings of UTF-8 characters instead of single-byte  character  strings.         strings of UTF-8 characters instead of single-byte strings. However, it
1791         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,
1792         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
1793         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.  
1794    
1795           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1796    
1797         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
1798         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
1799         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
1800         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
1801         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-
1802         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
1803         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
1804         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
1805         ing of subject strings.         passed to pcre_exec() and pcre_dfa_exec(),  to  suppress  the  validity
1806           checking of subject strings.
1807    
1808    
1809  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1810    
1811         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
1812         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
1813         both compiling functions. As PCRE has developed, some error codes  have         both  compiling  functions.  Note  that error messages are always 8-bit
1814         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
1815           codes  have  fallen  out of use. To avoid confusion, they have not been
1816           re-used.
1817    
1818            0  no error            0  no error
1819            1  \ at end of pattern            1  \ at end of pattern
# Line 1242  COMPILATION ERROR CODES Line 1827  COMPILATION ERROR CODES
1827            9  nothing to repeat            9  nothing to repeat
1828           10  [this code is not in use]           10  [this code is not in use]
1829           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1830           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1831           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1832           14  missing )           14  missing )
1833           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1250  COMPILATION ERROR CODES Line 1835  COMPILATION ERROR CODES
1835           17  unknown option bit(s) set           17  unknown option bit(s) set
1836           18  missing ) after comment           18  missing ) after comment
1837           19  [this code is not in use]           19  [this code is not in use]
1838           20  regular expression too large           20  regular expression is too large
1839           21  failed to get memory           21  failed to get memory
1840           22  unmatched parentheses           22  unmatched parentheses
1841           23  internal error: code overflow           23  internal error: code overflow
# Line 1259  COMPILATION ERROR CODES Line 1844  COMPILATION ERROR CODES
1844           26  malformed number or name after (?(           26  malformed number or name after (?(
1845           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1846           28  assertion expected after (?(           28  assertion expected after (?(
1847           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1848           30  unknown POSIX class name           30  unknown POSIX class name
1849           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1850           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is compiled without UTF support
1851           33  [this code is not in use]           33  [this code is not in use]
1852           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1853           35  invalid condition (?(0)           35  invalid condition (?(0)
1854           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
1855           37  PCRE does not support \L, \l, \N, \U, or \u           37  PCRE does not support \L, \l, \N{name}, \U, or \u
1856           38  number after (?C is > 255           38  number after (?C is > 255
1857           39  closing ) for (?C expected           39  closing ) for (?C expected
1858           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
1859           41  unrecognized character after (?P           41  unrecognized character after (?P
1860           42  syntax error in subpattern name (missing terminator)           42  syntax error in subpattern name (missing terminator)
1861           43  two named subpatterns have the same name           43  two named subpatterns have the same name
1862           44  invalid UTF-8 string           44  invalid UTF-8 string (specifically UTF-8)
1863           45  support for \P, \p, and \X has not been compiled           45  support for \P, \p, and \X has not been compiled
1864           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1865           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1866           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1867           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1868           50  repeated subpattern is too long           50  [this code is not in use]
1869           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
1870           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1871           53   internal  error:  previously-checked  referenced  subpattern not           53  internal error: previously-checked referenced subpattern
1872         found                 not found
1873           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1874           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1875           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1876             57  \g is not followed by a braced, angle-bracketed, or quoted
1877                   name/number or by a plain number
1878             58  a numbered reference must not be zero
1879             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1880             60  (*VERB) not recognized
1881             61  number is too big
1882             62  subpattern name expected
1883             63  digit expected after (?+
1884             64  ] is an invalid data character in JavaScript compatibility mode
1885             65  different names for subpatterns of the same number are
1886                   not allowed
1887             66  (*MARK) must have an argument
1888             67  this version of PCRE is not compiled with Unicode property
1889                   support
1890             68  \c must be followed by an ASCII character
1891             69  \k is not followed by a braced, angle-bracketed, or quoted name
1892             70  internal error: unknown opcode in find_fixedlength()
1893             71  \N is not supported in a class
1894             72  too many forward references
1895             73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
1896             74  invalid UTF-16 string (specifically UTF-16)
1897             75  name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
1898    
1899           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1900           values may be used if the limits were changed when PCRE was built.
1901    
1902    
1903  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1295  STUDYING A PATTERN Line 1905  STUDYING A PATTERN
1905         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1906              const char **errptr);              const char **errptr);
1907    
1908         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
1909         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
1910         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1911         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1912         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1913         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
1914         the results of the study.         the results of the study.
1915    
1916         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1917         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
1918         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
1919         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1920    
1921         If  studying  the  pattern  does not produce any additional information         If studying the  pattern  does  not  produce  any  useful  information,
1922         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1923         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
1924         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1925    
1926           The  second  argument  of  pcre_study() contains option bits. There are
1927           three options:
1928    
1929         The second argument of pcre_study() contains option bits.  At  present,           PCRE_STUDY_JIT_COMPILE
1930         no options are defined, and this argument should always be zero.           PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
1931             PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
1932    
1933           If any of these are set, and the just-in-time  compiler  is  available,
1934           the  pattern  is  further compiled into machine code that executes much
1935           faster than the pcre_exec()  interpretive  matching  function.  If  the
1936           just-in-time  compiler is not available, these options are ignored. All
1937           other bits in the options argument must be zero.
1938    
1939           JIT compilation is a heavyweight optimization. It can  take  some  time
1940           for  patterns  to  be analyzed, and for one-off matches and simple pat-
1941           terns the benefit of faster execution might be offset by a much  slower
1942           study time.  Not all patterns can be optimized by the JIT compiler. For
1943           those that cannot be handled, matching automatically falls back to  the
1944           pcre_exec()  interpreter.  For more details, see the pcrejit documenta-
1945           tion.
1946    
1947         The  third argument for pcre_study() is a pointer for an error message.         The third argument for pcre_study() is a pointer for an error  message.
1948         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1949         points  to  is  set  to NULL. Otherwise it is set to point to a textual         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1950         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
1951         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
1952         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1953    
1954         This is a typical call to pcre_study():         When  you are finished with a pattern, you can free the memory used for
1955           the study data by calling pcre_free_study(). This function was added to
1956           the  API  for  release  8.20. For earlier versions, the memory could be
1957           freed with pcre_free(), just like the pattern itself. This  will  still
1958           work  in  cases where JIT optimization is not used, but it is advisable
1959           to change to the new function when convenient.
1960    
1961           This is a typical way in which pcre_study() is used (except that  in  a
1962           real application there should be tests for errors):
1963    
1964           pcre_extra *pe;           int rc;
1965           pe = pcre_study(           pcre *re;
1966             pcre_extra *sd;
1967             re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1968             sd = pcre_study(
1969             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
1970             0,              /* no options exist */             0,              /* no options */
1971             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1972             rc = pcre_exec(   /* see below for details of pcre_exec() options */
1973         At present, studying a pattern is useful only for non-anchored patterns             re, sd, "subject", 7, 0, 0, ovector, 30);
1974         that  do not have a single fixed starting character. A bitmap of possi-           ...
1975         ble starting bytes is created.           pcre_free_study(sd);
1976             pcre_free(re);
1977    
1978           Studying a pattern does two things: first, a lower bound for the length
1979           of subject string that is needed to match the pattern is computed. This
1980           does not mean that there are any strings of that length that match, but
1981           it does guarantee that no shorter strings match. The value is  used  by
1982           pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
1983           match strings that are shorter than the lower bound. You can  find  out
1984           the value in a calling program via the pcre_fullinfo() function.
1985    
1986           Studying a pattern is also useful for non-anchored patterns that do not
1987           have a single fixed starting character. A bitmap of  possible  starting
1988           bytes  is  created. This speeds up finding a position in the subject at
1989           which to start matching. (In 16-bit mode, the bitmap is used for 16-bit
1990           values less than 256.)
1991    
1992           These  two optimizations apply to both pcre_exec() and pcre_dfa_exec(),
1993           and the information is also used by the JIT  compiler.   The  optimiza-
1994           tions can be disabled by setting the PCRE_NO_START_OPTIMIZE option when
1995           calling pcre_exec() or pcre_dfa_exec(), but if this is done, JIT execu-
1996           tion  is  also disabled. You might want to do this if your pattern con-
1997           tains callouts or (*MARK) and you want to make use of these  facilities
1998           in    cases    where    matching   fails.   See   the   discussion   of
1999           PCRE_NO_START_OPTIMIZE below.
2000    
2001    
2002  LOCALE SUPPORT  LOCALE SUPPORT
# Line 1341  LOCALE SUPPORT Line 2004  LOCALE SUPPORT
2004         PCRE handles caseless matching, and determines whether  characters  are         PCRE handles caseless matching, and determines whether  characters  are
2005         letters,  digits, or whatever, by reference to a set of tables, indexed         letters,  digits, or whatever, by reference to a set of tables, indexed
2006         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
2007         characters  with  codes  less than 128. Higher-valued codes never match         characters  with  codes  less than 128. By default, higher-valued codes
2008         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
2009         with  Unicode  character property support. The use of locales with Uni-         PCRE  is  built with Unicode character property support. Alternatively,
2010         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
2011         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
2012         not try to mix the two.         use of locales with Unicode is discouraged. If you are handling charac-
2013           ters  with codes greater than 128, you should either use UTF-8 and Uni-
2014           code, or use locales, but not try to mix the two.
2015    
2016         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
2017         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
# Line 1398  INFORMATION ABOUT A PATTERN Line 2063  INFORMATION ABOUT A PATTERN
2063              int what, void *where);              int what, void *where);
2064    
2065         The  pcre_fullinfo() function returns information about a compiled pat-         The  pcre_fullinfo() function returns information about a compiled pat-
2066         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the pcre_info() function, which was removed from  the
2067         less retained for backwards compability (and is documented below).         library at version 8.30, after more than 10 years of obsolescence.
2068    
2069         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
2070         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 1408  INFORMATION ABOUT A PATTERN Line 2073  INFORMATION ABOUT A PATTERN
2073         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
2074         success, or one of the following negative numbers:         success, or one of the following negative numbers:
2075    
2076           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL           the argument code was NULL
2077                                 the argument where was NULL                                     the argument where was NULL
2078           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC       the "magic number" was not found
2079           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
2080                                       endianness
2081             PCRE_ERROR_BADOPTION      the value of what was invalid
2082    
2083         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
2084         an  simple check against passing an arbitrary memory pointer. Here is a         an  simple check against passing an arbitrary memory pointer. The endi-
2085         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
2086         pattern:         different  host.  Here  is a typical call of pcre_fullinfo(), to obtain
2087           the length of the compiled pattern:
2088    
2089           int rc;           int rc;
2090           size_t length;           size_t length;
2091           rc = pcre_fullinfo(           rc = pcre_fullinfo(
2092             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
2093             pe,               /* result of pcre_study(), or NULL */             sd,               /* result of pcre_study(), or NULL */
2094             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
2095             &length);         /* where to put the data */             &length);         /* where to put the data */
2096    
2097         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
2098         are as follows:         are as follows:
2099    
2100           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
2101    
2102         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
2103         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
2104         there are no back references.         there are no back references.
2105    
2106           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
2107    
2108         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
2109         argument should point to an int variable.         argument should point to an int variable.
2110    
2111           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
2112    
2113         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
2114         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
2115         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
2116         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
2117         passing a NULL table pointer.         passing a NULL table pointer.
2118    
2119           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
2120    
2121         Return  information  about  the first byte of any matched string, for a         Return information about the first data unit of any matched string, for
2122         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
2123         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name         library, where data units are bytes.) The fourth argument should  point
2124         is still recognized for backwards compatibility.)         to an int variable.
2125    
2126           If  there  is  a  fixed first value, for example, the letter "c" from a
2127           pattern such as (cat|cow|coyote), its value is returned. In  the  8-bit
2128           library,  the  value is always less than 256; in the 16-bit library the
2129           value can be up to 0xffff.
2130    
2131         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  
2132    
2133         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
2134         branch starts with "^", or         branch starts with "^", or
2135    
2136         (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
2137         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
2138    
2139         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
2140         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
2141         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
2142    
2143           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
2144    
2145         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
2146         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
2147         matching  string, a pointer to the table is returned. Otherwise NULL is         in any matching string, a pointer to the table is  returned.  Otherwise
2148         returned. The fourth argument should point to an unsigned char *  vari-         NULL  is returned. The fourth argument should point to an unsigned char
2149         able.         * variable.
2150    
2151             PCRE_INFO_HASCRORLF
2152    
2153           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
2154           characters,  otherwise  0.  The  fourth argument should point to an int
2155           variable. An explicit match is either a literal CR or LF character,  or
2156           \r or \n.
2157    
2158           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
2159    
2160         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,
2161         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)
2162         nal option setting changes the local PCRE_DUPNAMES value.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
2163    
2164             PCRE_INFO_JIT
2165    
2166           Return  1  if  the pattern was studied with one of the JIT options, and
2167           just-in-time compiling was successful. The fourth argument should point
2168           to  an  int variable. A return value of 0 means that JIT support is not
2169           available in this version of PCRE, or that the pattern was not  studied
2170           with  a JIT option, or that the JIT compiler could not handle this par-
2171           ticular pattern. See the pcrejit documentation for details of what  can
2172           and cannot be handled.
2173    
2174             PCRE_INFO_JITSIZE
2175    
2176           If  the  pattern was successfully studied with a JIT option, return the
2177           size of the JIT compiled code, otherwise return zero. The fourth  argu-
2178           ment should point to a size_t variable.
2179    
2180           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
2181    
2182         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
2183         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
2184         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
2185         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
2186         byte  is  recorded only if it follows something of variable length. For         value  is recorded only if it follows something of variable length. For
2187         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
2188         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
2189    
2190             PCRE_INFO_MAXLOOKBEHIND
2191    
2192           Return  the  number of characters (NB not bytes) in the longest lookbe-
2193           hind assertion in the pattern. Note that the simple assertions  \b  and
2194           \B  require a one-character lookbehind. This information is useful when
2195           doing multi-segment matching using the partial matching facilities.
2196    
2197             PCRE_INFO_MINLENGTH
2198    
2199           If the pattern was studied and a minimum length  for  matching  subject
2200           strings  was  computed,  its  value is returned. Otherwise the returned
2201           value is -1. The value is a number of characters, which in  UTF-8  mode
2202           may  be  different from the number of bytes. The fourth argument should
2203           point to an int variable. A non-negative value is a lower bound to  the
2204           length  of  any  matching  string. There may not be any strings of that
2205           length that do actually match, but every string that does match  is  at
2206           least that long.
2207    
2208           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
2209           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
2210           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
# Line 1510  INFORMATION ABOUT A PATTERN Line 2223  INFORMATION ABOUT A PATTERN
2223         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
2224         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
2225         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
2226         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
2227         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-
2228         sis,  most  significant byte first. The rest of the entry is the corre-         ber  of  the capturing parenthesis, most significant byte first. In the
2229         sponding name, zero terminated. The names are  in  alphabetical  order.         16-bit library, the pointer points to 16-bit data units, the  first  of
2230         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
2231         theses numbers. For example, consider  the  following  pattern  (assume         corresponding name, zero terminated.
2232         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is  
2233         ignored):         The names are in alphabetical order. Duplicate names may appear if  (?|
2234           is used to create multiple groups with the same number, as described in
2235           the section on duplicate subpattern numbers in  the  pcrepattern  page.
2236           Duplicate  names  for  subpatterns with different numbers are permitted
2237           only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
2238           appear  in  the table in the order in which they were found in the pat-
2239           tern. In the absence of (?| this is the  order  of  increasing  number;
2240           when (?| is used this is not necessarily the case because later subpat-
2241           terns may have lower numbers.
2242    
2243           As a simple example of the name/number table,  consider  the  following
2244           pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is
2245           set, so white space - including newlines - is ignored):
2246    
2247           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
2248           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
# Line 1538  INFORMATION ABOUT A PATTERN Line 2263  INFORMATION ABOUT A PATTERN
2263    
2264           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
2265    
2266         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
2267         The fourth argument should point to an int  variable.  The  pcrepartial         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
2268         documentation  lists  the restrictions that apply to patterns when par-         variable.  From  release  8.00,  this  always  returns  1,  because the
2269         tial matching is used.         restrictions that previously applied  to  partial  matching  have  been
2270           lifted.  The  pcrepartial documentation gives details of partial match-
2271           ing.
2272    
2273           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
2274    
2275         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
2276         fourth  argument  should  point to an unsigned long int variable. These         fourth  argument  should  point to an unsigned long int variable. These
2277         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
2278         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
2279           other words, they are the options that will be in force  when  matching
2280           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
2281           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
2282           and PCRE_EXTENDED.
2283    
2284         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
2285         alternatives begin with one of the following:         alternatives begin with one of the following:
# Line 1564  INFORMATION ABOUT A PATTERN Line 2295  INFORMATION ABOUT A PATTERN
2295    
2296           PCRE_INFO_SIZE           PCRE_INFO_SIZE
2297    
2298         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).
2299         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
2300         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
2301         size_t variable.         pcre_compile(). The value that is passed as the argument  to  pcre_mal-
2302           loc()  when pcre_compile() is getting memory in which to place the com-
2303           piled data is the value returned by this option plus the  size  of  the
2304           pcre  structure. Studying a compiled pattern, with or without JIT, does
2305           not alter the value returned by this option.
2306    
2307           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
2308    
2309         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
2310         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
2311         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
2312         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
2313         variable.         information that will speed  up  matching  (see  the  section  entitled
2314           "Studying a pattern" above). The format of the study_data block is pri-
2315           vate, but its length is made available via this option so that  it  can
2316  OBSOLETE INFO FUNCTION         be  saved  and  restored  (see  the  pcreprecompile  documentation  for
2317           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).  
2318    
2319    
2320  REFERENCE COUNTS  REFERENCE COUNTS
# Line 1628  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2345  MATCHING A PATTERN: THE TRADITIONAL FUNC
2345              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
2346              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
2347    
2348         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
2349         compiled  pattern, which is passed in the code argument. If the pattern         compiled pattern, which is passed in the code argument. If the  pattern
2350         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
2351         argument.  This  function is the main matching facility of the library,         argument. You can call pcre_exec() with the same code and  extra  argu-
2352         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
2353         an  alternative matching function, which is described below in the sec-         strings with the same pattern.
2354         tion about the pcre_dfa_exec() function.  
2355           This function is the main matching facility  of  the  library,  and  it
2356           operates  in  a  Perl-like  manner. For specialist use there is also an
2357           alternative matching function, which is described below in the  section
2358           about the pcre_dfa_exec() function.
2359    
2360         In most applications, the pattern will have been compiled (and  option-         In  most applications, the pattern will have been compiled (and option-
2361         ally  studied)  in the same process that calls pcre_exec(). However, it         ally studied) in the same process that calls pcre_exec().  However,  it
2362         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
2363         later  in  different processes, possibly even on different hosts. For a         later in different processes, possibly even on different hosts.  For  a
2364         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
2365    
2366         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1658  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2379  MATCHING A PATTERN: THE TRADITIONAL FUNC
2379    
2380     Extra data for pcre_exec()     Extra data for pcre_exec()
2381    
2382         If the extra argument is not NULL, it must point to a  pcre_extra  data         If  the  extra argument is not NULL, it must point to a pcre_extra data
2383         block.  The pcre_study() function returns such a block (when it doesn't         block. The pcre_study() function returns such a block (when it  doesn't
2384         return NULL), but you can also create one for yourself, and pass  addi-         return  NULL), but you can also create one for yourself, and pass addi-
2385         tional  information  in it. The pcre_extra block contains the following         tional information in it. The pcre_extra block contains  the  following
2386         fields (not necessarily in this order):         fields (not necessarily in this order):
2387    
2388           unsigned long int flags;           unsigned long int flags;
2389           void *study_data;           void *study_data;
2390             void *executable_jit;
2391           unsigned long int match_limit;           unsigned long int match_limit;
2392           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
2393           void *callout_data;           void *callout_data;
2394           const unsigned char *tables;           const unsigned char *tables;
2395             unsigned char **mark;
2396    
2397         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
2398         are set. The flag bits are:         "PCRE_UCHAR16 **".
2399    
2400           PCRE_EXTRA_STUDY_DATA         The flags field is used to specify which of the other fields  are  set.
2401           The flag bits are:
2402    
2403             PCRE_EXTRA_CALLOUT_DATA
2404             PCRE_EXTRA_EXECUTABLE_JIT
2405             PCRE_EXTRA_MARK
2406           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
2407           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
2408           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_STUDY_DATA
2409           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
2410    
2411         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-
2412         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
2413         the appropriate flag bit. You should not set this yourself, but you may         returned  by pcre_study(), together with the appropriate flag bits. You
2414         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
2415         flag bits.         other fields and their corresponding flag bits.
2416    
2417         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
2418         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
2419         match,  but  which  have  a very large number of possibilities in their         match,  but  which  have  a very large number of possibilities in their
2420         search trees. The classic  example  is  the  use  of  nested  unlimited         search trees. The classic example is a pattern that uses nested  unlim-
2421         repeats.         ited repeats.
2422    
2423         Internally,  PCRE uses a function called match() which it calls repeat-         Internally,  pcre_exec() uses a function called match(), which it calls
2424         edly (sometimes recursively). The limit set by match_limit  is  imposed         repeatedly (sometimes recursively). The limit  set  by  match_limit  is
2425         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,
2426         has the effect of limiting the amount of  backtracking  that  can  take         which has the effect of limiting the amount of  backtracking  that  can
2427         place. For patterns that are not anchored, the count restarts from zero         take place. For patterns that are not anchored, the count restarts from
2428         for each position in the subject string.         zero for each position in the subject string.
2429    
2430         The default value for the limit can be set  when  PCRE  is  built;  the         When pcre_exec() is called with a pattern that was successfully studied
2431         default  default  is 10 million, which handles all but the most extreme         with  a  JIT  option, the way that the matching is executed is entirely
2432         cases. You can override the default  by  suppling  pcre_exec()  with  a         different.  However, there is still the possibility of runaway matching
2433         pcre_extra     block    in    which    match_limit    is    set,    and         that goes on for a very long time, and so the match_limit value is also
2434         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is         used in this case (but in a different way) to limit how long the match-
2435           ing can continue.
2436    
2437           The  default  value  for  the  limit can be set when PCRE is built; the
2438           default default is 10 million, which handles all but the  most  extreme
2439           cases.  You  can  override  the  default by suppling pcre_exec() with a
2440           pcre_extra    block    in    which    match_limit    is    set,     and
2441           PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is
2442         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
2443    
2444         The  match_limit_recursion field is similar to match_limit, but instead         The match_limit_recursion field is similar to match_limit, but  instead
2445         of limiting the total number of times that match() is called, it limits         of limiting the total number of times that match() is called, it limits
2446         the  depth  of  recursion. The recursion depth is a smaller number than         the depth of recursion. The recursion depth is a  smaller  number  than
2447         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-
2448         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.
2449    
2450         Limiting the recursion depth limits the amount of  stack  that  can  be         Limiting the recursion depth limits the amount of  machine  stack  that
2451         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
2452         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
2453           limit  is not relevant, and is ignored, when matching is done using JIT
2454           compiled code.
2455    
2456         The default value for match_limit_recursion can be  set  when  PCRE  is         The default value for match_limit_recursion can be  set  when  PCRE  is
2457         built;  the  default  default  is  the  same  value  as the default for         built;  the  default  default  is  the  same  value  as the default for
# Line 1723  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2460  MATCHING A PATTERN: THE TRADITIONAL FUNC
2460         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
2461         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2462    
2463         The  pcre_callout  field is used in conjunction with the "callout" fea-         The  callout_data  field is used in conjunction with the "callout" fea-
2464         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2465    
2466         The tables field  is  used  to  pass  a  character  tables  pointer  to         The tables field  is  used  to  pass  a  character  tables  pointer  to
2467         pcre_exec();  this overrides the value that is stored with the compiled         pcre_exec();  this overrides the value that is stored with the compiled
# Line 1737  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2474  MATCHING A PATTERN: THE TRADITIONAL FUNC
2474         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
2475         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2476    
2477           If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2478           set to point to a suitable variable. If the pattern contains any  back-
2479           tracking  control verbs such as (*MARK:NAME), and the execution ends up
2480           with a name to pass back, a pointer to the  name  string  (zero  termi-
2481           nated)  is  placed  in  the  variable pointed to by the mark field. The
2482           names are within the compiled pattern; if you wish  to  retain  such  a
2483           name  you must copy it before freeing the memory of a compiled pattern.
2484           If there is no name to pass back, the variable pointed to by  the  mark
2485           field  is  set  to NULL. For details of the backtracking control verbs,
2486           see the section entitled "Backtracking control" in the pcrepattern doc-
2487           umentation.
2488    
2489     Option bits for pcre_exec()     Option bits for pcre_exec()
2490    
2491         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.
2492         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,
2493         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2494         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_HARD,   and
2495           PCRE_PARTIAL_SOFT.
2496    
2497           If  the  pattern  was successfully studied with one of the just-in-time
2498           (JIT) compile options, the only supported options for JIT execution are
2499           PCRE_NO_UTF8_CHECK,     PCRE_NOTBOL,     PCRE_NOTEOL,    PCRE_NOTEMPTY,
2500           PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If  an
2501           unsupported  option  is  used, JIT execution is disabled and the normal
2502           interpretive code in pcre_exec() is run.
2503    
2504           PCRE_ANCHORED           PCRE_ANCHORED
2505    
# Line 1751  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2508  MATCHING A PATTERN: THE TRADITIONAL FUNC
2508         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
2509         unachored at matching time.         unachored at matching time.
2510    
2511             PCRE_BSR_ANYCRLF
2512             PCRE_BSR_UNICODE
2513    
2514           These options (which are mutually exclusive) control what the \R escape
2515           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2516           or  to  match  any Unicode newline sequence. These options override the
2517           choice that was made or defaulted when the pattern was compiled.
2518    
2519           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
2520           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
2521           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
2522           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
2523           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
2524    
2525         These  options  override  the  newline  definition  that  was chosen or         These options override  the  newline  definition  that  was  chosen  or
2526         defaulted when the pattern was compiled. For details, see the  descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
2527         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
2528         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2529         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
2530         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
2531         PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY is set, and a match attempt  
2532         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
2533         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-
2534         after the CRLF.         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2535           explicit matches for  CR  or  LF  characters,  the  match  position  is
2536           advanced by two characters instead of one, in other words, to after the
2537           CRLF.
2538    
2539           The above rule is a compromise that makes the most common cases work as
2540           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2541           option is not set), it does not match the string "\r\nA" because, after
2542           failing  at the start, it skips both the CR and the LF before retrying.
2543           However, the pattern [\r\n]A does match that string,  because  it  con-
2544           tains an explicit CR or LF reference, and so advances only by one char-
2545           acter after the first failure.
2546    
2547           An explicit match for CR of LF is either a literal appearance of one of
2548           those  characters,  or  one  of the \r or \n escape sequences. Implicit
2549           matches such as [^X] do not count, nor does \s (which includes  CR  and
2550           LF in the characters that it matches).
2551    
2552           Notwithstanding  the above, anomalous effects may still occur when CRLF
2553           is a valid newline sequence and explicit \r or \n escapes appear in the
2554           pattern.
2555    
2556           PCRE_NOTBOL           PCRE_NOTBOL
2557    
2558         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2559         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
2560         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
2561         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
2562         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2563    
2564           PCRE_NOTEOL           PCRE_NOTEOL
2565    
2566         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
2567         of  a line, so the dollar metacharacter should not match it nor (except         of a line, so the dollar metacharacter should not match it nor  (except
2568         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
2569         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2570         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2571         not affect \Z or \z.         not affect \Z or \z.
2572    
2573           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2574    
2575         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
2576         set. If there are alternatives in the pattern, they are tried.  If  all         set.  If  there are alternatives in the pattern, they are tried. If all
2577         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2578         example, if the pattern         example, if the pattern
2579    
2580           a?b?           a?b?
2581    
2582         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
2583         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
2584         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-
2585         rences of "a" or "b".         rences of "a" or "b".
2586    
2587         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2588         cial case of a pattern match of the empty  string  within  its  split()  
2589         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
2590         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
2591         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.
2592         if that fails by advancing the starting offset (see below)  and  trying  
2593         an ordinary match again. There is some code that demonstrates how to do         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2594         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2595           match of the empty string within its split() function, and  when  using
2596           the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2597           matching a null string by first trying the match again at the same off-
2598           set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2599           fails, by advancing the starting offset (see below) and trying an ordi-
2600           nary  match  again. There is some code that demonstrates how to do this
2601           in the pcredemo sample program. In the most general case, you  have  to
2602           check  to  see  if the newline convention recognizes CRLF as a newline,
2603           and if so, and the current character is CR followed by LF, advance  the
2604           starting offset by two characters instead of one.
2605    
2606             PCRE_NO_START_OPTIMIZE
2607    
2608           There  are a number of optimizations that pcre_exec() uses at the start
2609           of a match, in order to speed up the process. For  example,  if  it  is
2610           known that an unanchored match must start with a specific character, it
2611           searches the subject for that character, and fails  immediately  if  it
2612           cannot  find  it,  without actually running the main matching function.
2613           This means that a special item such as (*COMMIT) at the start of a pat-
2614           tern  is  not  considered until after a suitable starting point for the
2615           match has been found. When callouts or (*MARK) items are in use,  these
2616           "start-up" optimizations can cause them to be skipped if the pattern is
2617           never actually used. The start-up optimizations are in  effect  a  pre-
2618           scan of the subject that takes place before the pattern is run.
2619    
2620           The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2621           possibly causing performance to suffer,  but  ensuring  that  in  cases
2622           where  the  result is "no match", the callouts do occur, and that items
2623           such as (*COMMIT) and (*MARK) are considered at every possible starting
2624           position  in  the  subject  string. If PCRE_NO_START_OPTIMIZE is set at
2625           compile time,  it  cannot  be  unset  at  matching  time.  The  use  of
2626           PCRE_NO_START_OPTIMIZE disables JIT execution; when it is set, matching
2627           is always done using interpretively.
2628    
2629           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
2630           operation.  Consider the pattern
2631    
2632             (*COMMIT)ABC
2633    
2634           When  this  is  compiled, PCRE records the fact that a match must start
2635           with the character "A". Suppose the subject  string  is  "DEFABC".  The
2636           start-up  optimization  scans along the subject, finds "A" and runs the
2637           first match attempt from there. The (*COMMIT) item means that the  pat-
2638           tern  must  match the current starting position, which in this case, it
2639           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
2640           set,  the  initial  scan  along the subject string does not happen. The
2641           first match attempt is run starting  from  "D"  and  when  this  fails,
2642           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
2643           result is "no match". If the pattern is studied,  more  start-up  opti-
2644           mizations  may  be  used. For example, a minimum length for the subject
2645           may be recorded. Consider the pattern
2646    
2647             (*MARK:A)(X|Y)
2648    
2649           The minimum length for a match is one  character.  If  the  subject  is
2650           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
2651           finally an empty string.  If the pattern is studied, the final  attempt
2652           does  not take place, because PCRE knows that the subject is too short,
2653           and so the (*MARK) is never encountered.  In this  case,  studying  the
2654           pattern  does  not  affect the overall match result, which is still "no
2655           match", but it does affect the auxiliary information that is returned.
2656    
2657           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2658    
2659         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
2660         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2661         called.  The value of startoffset is also checked  to  ensure  that  it         called.  The entire string is checked before any other processing takes
2662         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence         place.  The  value  of  startoffset  is  also checked to ensure that it
2663         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         points to the start of a UTF-8 character. There is a  discussion  about
2664         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         the  validity  of  UTF-8 strings in the pcreunicode page. If an invalid
2665         returned.         sequence  of  bytes   is   found,   pcre_exec()   returns   the   error
2666           PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
2667         If you already know that your subject is valid, and you  want  to  skip         truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
2668         these    checks    for   performance   reasons,   you   can   set   the         both  cases, information about the precise nature of the error may also
2669         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         be returned (see the descriptions of these errors in the section  enti-
2670         do  this  for the second and subsequent calls to pcre_exec() if you are         tled  Error return values from pcre_exec() below).  If startoffset con-
2671         making repeated calls to find all  the  matches  in  a  single  subject         tains a value that does not point to the start of a UTF-8 character (or
2672         string.  However,  you  should  be  sure  that the value of startoffset         to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2673         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is  
2674         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         If  you  already  know that your subject is valid, and you want to skip
2675         value of startoffset that does not point to the start of a UTF-8  char-         these   checks   for   performance   reasons,   you   can    set    the
2676         acter, is undefined. Your program may crash.         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2677           do this for the second and subsequent calls to pcre_exec() if  you  are
2678           PCRE_PARTIAL         making  repeated  calls  to  find  all  the matches in a single subject
2679           string. However, you should be  sure  that  the  value  of  startoffset
2680         This  option  turns  on  the  partial  matching feature. If the subject         points  to  the  start of a character (or the end of the subject). When
2681         string fails to match the pattern, but at some point during the  match-         PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid string as a
2682         ing  process  the  end of the subject was reached (that is, the subject         subject  or  an invalid value of startoffset is undefined. Your program
2683         partially matches the pattern and the failure to  match  occurred  only         may crash.
2684         because  there were not enough subject characters), pcre_exec() returns  
2685         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is           PCRE_PARTIAL_HARD
2686         used,  there  are restrictions on what may appear in the pattern. These           PCRE_PARTIAL_SOFT
2687         are discussed in the pcrepartial documentation.  
2688           These options turn on the partial matching feature. For backwards  com-
2689           patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2690           match occurs if the end of the subject string is reached  successfully,
2691           but  there  are not enough subject characters to complete the match. If
2692           this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2693           matching  continues  by  testing any remaining alternatives. Only if no
2694           complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
2695           PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
2696           caller is prepared to handle a partial match, but only if  no  complete
2697           match can be found.
2698    
2699           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this
2700           case, if a partial match  is  found,  pcre_exec()  immediately  returns
2701           PCRE_ERROR_PARTIAL,  without  considering  any  other  alternatives. In
2702           other words, when PCRE_PARTIAL_HARD is set, a partial match is  consid-
2703           ered to be more important that an alternative complete match.
2704    
2705           In  both  cases,  the portion of the string that was inspected when the
2706           partial match was found is set as the first matching string. There is a
2707           more  detailed  discussion  of partial and multi-segment matching, with
2708           examples, in the pcrepartial documentation.
2709    
2710     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2711    
2712         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
2713         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.
2714         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,
2715         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec()  returns  PCRE_ERROR_BADOFFSET. When the starting offset is
2716         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,
2717         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
2718           must point to the start of a UTF-8 character (or the end  of  the  sub-
2719         A  non-zero  starting offset is useful when searching for another match         ject).  Unlike  the pattern string, the subject may contain binary zero
2720         in the same subject by calling pcre_exec() again after a previous  suc-         bytes.
2721         cess.   Setting  startoffset differs from just passing over a shortened  
2722         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
2723           in  the same subject by calling pcre_exec() again after a previous suc-
2724           cess.  Setting startoffset differs from just passing over  a  shortened
2725           string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
2726         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2727    
2728           \Biss\B           \Biss\B
2729    
2730         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
2731         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.)
2732         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
2733         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
2734         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
2735         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
2736         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
2737         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-
2738         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
2739         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2740    
2741           Finding  all  the  matches  in a subject is tricky when the pattern can
2742           match an empty string. It is possible to emulate Perl's /g behaviour by
2743           first   trying   the   match   again  at  the  same  offset,  with  the
2744           PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED  options,  and  then  if  that
2745           fails,  advancing  the  starting  offset  and  trying an ordinary match
2746           again. There is some code that demonstrates how to do this in the pcre-
2747           demo sample program. In the most general case, you have to check to see
2748           if the newline convention recognizes CRLF as a newline, and if so,  and
2749           the current character is CR followed by LF, advance the starting offset
2750           by two characters instead of one.
2751    
2752         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,
2753         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
2754         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 1883  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2764  MATCHING A PATTERN: THE TRADITIONAL FUNC
2764         string. PCRE supports several other kinds of  parenthesized  subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
2765         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2766    
2767         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2768         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-
2769         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:
2770         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2771    
2772         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-
2773         strings,  each  substring using a pair of integers. The remaining third         strings,  each  substring using a pair of integers. The remaining third
2774         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-
2775         turing  subpatterns, and is not available for passing back information.         turing  subpatterns, and is not available for passing back information.
2776         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
2777         it is not, it is rounded down.         it is not, it is rounded down.
2778    
2779         When  a  match  is successful, information about captured substrings is         When  a  match  is successful, information about captured substrings is
2780         returned in pairs of integers, starting at the  beginning  of  ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
2781         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
2782         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
2783         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
2784         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
2785         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2786         entire pattern. The next pair is used for the first  capturing  subpat-  
2787         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
2788         highest numbered pair that has been set. For example, if two substrings         portion of the subject string matched by the entire pattern.  The  next
2789         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
2790         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2791         that just the first pair of offsets has been set.         has  been  set.  For example, if two substrings have been captured, the
2792           returned value is 3. If there are no capturing subpatterns, the  return
2793           value from a successful match is 1, indicating that just the first pair
2794           of offsets has been set.
2795    
2796         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2797         of the string that it matched that is returned.         of the string that it matched that is returned.
2798    
2799         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,
2800         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
2801         function returns a value of zero. In particular, if the substring  off-         function  returns a value of zero. If neither the actual string matched
2802         sets are not of interest, pcre_exec() may be called with ovector passed         nor any captured substrings are of interest, pcre_exec() may be  called
2803         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-
2804         references  and  the  ovector is not big enough to remember the related         tern contains back references and the ovector  is  not  big  enough  to
2805         substrings, PCRE has to get additional memory for use during  matching.         remember  the related substrings, PCRE has to get additional memory for
2806         Thus it is usually advisable to supply an ovector.         use during matching. Thus it is usually advisable to supply an  ovector
2807           of reasonable size.
2808         The  pcre_info()  function  can  be used to find out how many capturing  
2809         subpatterns there are in a compiled  pattern.  The  smallest  size  for         There  are  some  cases where zero is returned (indicating vector over-
2810         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
2811           match. For example, consider the pattern
2812    
2813             (a)(?:(b)c|bd)
2814    
2815           If  a  vector of 6 elements (allowing for only 1 captured substring) is
2816           given with subject string "abd", pcre_exec() will try to set the second
2817           captured string, thereby recording a vector overflow, before failing to
2818           match "c" and backing up  to  try  the  second  alternative.  The  zero
2819           return,  however,  does  correctly  indicate that the maximum number of
2820           slots (namely 2) have been filled. In similar cases where there is tem-
2821           porary  overflow,  but  the final number of used slots is actually less
2822           than the maximum, a non-zero value is returned.
2823    
2824           The pcre_fullinfo() function can be used to find out how many capturing
2825           subpatterns  there  are  in  a  compiled pattern. The smallest size for
2826           ovector that will allow for n captured substrings, in addition  to  the
2827         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.
2828    
2829         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
2830         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,
2831         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
2832         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
2833         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-
2834         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2835    
2836         Offset  values  that correspond to unused subpatterns at the end of the         Offset values that correspond to unused subpatterns at the end  of  the
2837         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
2838         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
2839         matched. The return from the function is 2, because  the  highest  used         matched.  The  return  from the function is 2, because the highest used
2840         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1, and the offsets for  for  the  second
2841         for the second and third capturing subpatterns if  you  wish  (assuming         and  third  capturing subpatterns (assuming the vector is large enough,
2842         the vector is large enough, of course).         of course) are set to -1.
2843    
2844           Note: Elements in the first two-thirds of ovector that  do  not  corre-
2845           spond  to  capturing parentheses in the pattern are never changed. That
2846           is, if a pattern contains n capturing parentheses, no more  than  ovec-
2847           tor[0]  to ovector[2n+1] are set by pcre_exec(). The other elements (in
2848           the first two-thirds) retain whatever values they previously had.
2849    
2850         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
2851         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2852    
2853     Error return values from pcre_exec()     Error return values from pcre_exec()
2854    
2855         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
2856         defined in the header file:         defined in the header file:
2857    
2858           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1955  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2861  MATCHING A PATTERN: THE TRADITIONAL FUNC
2861    
2862           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2863    
2864         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
2865         ovecsize was not zero.         ovecsize was not zero.
2866    
2867           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1964  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2870  MATCHING A PATTERN: THE TRADITIONAL FUNC
2870    
2871           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2872    
2873         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,
2874         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
2875         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
2876         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
2877         gives when the magic number is not present.         gives when the magic number is not present.
2878    
2879           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2880    
2881         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2882         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
2883         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2884    
2885           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2886    
2887         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
2888         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2889         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
2890         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
2891         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2892    
2893           This  error  is also given if pcre_stack_malloc() fails in pcre_exec().
2894           This can happen only when PCRE has been compiled with  --disable-stack-
2895           for-recursion.
2896    
2897           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2898    
2899         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
2900         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2901         returned by pcre_exec().         returned by pcre_exec().
2902    
2903           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2904    
2905         The backtracking limit, as specified by  the  match_limit  field  in  a         The  backtracking  limit,  as  specified  by the match_limit field in a
2906         pcre_extra  structure  (or  defaulted) was reached. See the description         pcre_extra structure (or defaulted) was reached.  See  the  description
2907         above.         above.
2908    
2909           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2910    
2911         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
2912         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
2913         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2914    
2915           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2916    
2917         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
2918         subject.         subject, and the PCRE_NO_UTF8_CHECK option was not set. If the size  of
2919           the  output  vector  (ovecsize)  is  at least 2, the byte offset to the
2920           start of the the invalid UTF-8 character is placed in  the  first  ele-
2921           ment,  and  a  reason  code is placed in the second element. The reason
2922           codes are listed in the following section.  For backward compatibility,
2923           if  PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8 char-
2924           acter  at  the  end  of  the   subject   (reason   codes   1   to   5),
2925           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2926    
2927           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2928    
2929         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
2930         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
2931         ter.         value  of startoffset did not point to the beginning of a UTF-8 charac-
2932           ter or the end of the subject.
2933    
2934           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2935    
2936         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
2937         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2938    
2939           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2940    
2941         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This  code  is  no  longer  in  use.  It was formerly returned when the
2942         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL option was used with a compiled pattern  containing  items
2943         documentation for details of partial matching.         that  were  not  supported  for  partial  matching.  From  release 8.00
2944           onwards, there are no restrictions on partial matching.
2945    
2946           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2947    
# Line 2031  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2950  MATCHING A PATTERN: THE TRADITIONAL FUNC
2950    
2951           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2952    
2953         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.
2954    
2955           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2956    
2957         The internal recursion limit, as specified by the match_limit_recursion         The internal recursion limit, as specified by the match_limit_recursion
2958         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
2959         description above.         description above.
2960    
          PCRE_ERROR_NULLWSLIMIT    (-22)  
   
        When a group that can match an empty  substring  is  repeated  with  an  
        unbounded  upper  limit, the subject position at the start of the group  
        must be remembered, so that a test for an empty string can be made when  
        the  end  of the group is reached. Some workspace is required for this;  
        if it runs out, this error is given.  
   
2961           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2962    
2963         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2964    
2965         Error numbers -16 to -20 are not used by pcre_exec().           PCRE_ERROR_BADOFFSET      (-24)
2966    
2967           The value of startoffset was negative or greater than the length of the
2968           subject, that is, the value in length.
2969    
2970             PCRE_ERROR_SHORTUTF8      (-25)
2971    
2972           This error is returned instead of PCRE_ERROR_BADUTF8 when  the  subject
2973           string  ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD
2974           option is set.  Information  about  the  failure  is  returned  as  for
2975           PCRE_ERROR_BADUTF8.  It  is in fact sufficient to detect this case, but
2976           this special error code for PCRE_PARTIAL_HARD precedes the  implementa-
2977           tion  of returned information; it is retained for backwards compatibil-
2978           ity.
2979    
2980             PCRE_ERROR_RECURSELOOP    (-26)
2981    
2982           This error is returned when pcre_exec() detects a recursion loop within
2983           the  pattern. Specifically, it means that either the whole pattern or a
2984           subpattern has been called recursively for the second time at the  same
2985           position in the subject string. Some simple patterns that might do this
2986           are detected and faulted at compile time, but more  complicated  cases,
2987           in particular mutual recursions between two different subpatterns, can-
2988           not be detected until run time.
2989    
2990             PCRE_ERROR_JIT_STACKLIMIT (-27)
2991    
2992           This error is returned when a pattern  that  was  successfully  studied
2993           using  a  JIT compile option is being matched, but the memory available
2994           for the just-in-time processing stack is  not  large  enough.  See  the
2995           pcrejit documentation for more details.
2996    
2997             PCRE_ERROR_BADMODE        (-28)
2998    
2999           This error is given if a pattern that was compiled by the 8-bit library
3000           is passed to a 16-bit library function, or vice versa.
3001    
3002             PCRE_ERROR_BADENDIANNESS  (-29)
3003    
3004           This error is given if  a  pattern  that  was  compiled  and  saved  is
3005           reloaded  on  a  host  with  different endianness. The utility function
3006           pcre_pattern_to_host_byte_order() can be used to convert such a pattern
3007           so that it runs on the new host.
3008    
3009           Error numbers -16 to -20, -22, and -30 are not used by pcre_exec().
3010    
3011       Reason codes for invalid UTF-8 strings
3012    
3013           This  section  applies  only  to  the  8-bit library. The corresponding
3014           information for the 16-bit library is given in the pcre16 page.
3015    
3016           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
3017           UTF8,  and  the size of the output vector (ovecsize) is at least 2, the
3018           offset of the start of the invalid UTF-8 character  is  placed  in  the
3019           first output vector element (ovector[0]) and a reason code is placed in
3020           the second element (ovector[1]). The reason codes are  given  names  in
3021           the pcre.h header file:
3022    
3023             PCRE_UTF8_ERR1
3024             PCRE_UTF8_ERR2
3025             PCRE_UTF8_ERR3
3026             PCRE_UTF8_ERR4
3027             PCRE_UTF8_ERR5
3028    
3029           The  string  ends  with a truncated UTF-8 character; the code specifies
3030           how many bytes are missing (1 to 5). Although RFC 3629 restricts  UTF-8
3031           characters  to  be  no longer than 4 bytes, the encoding scheme (origi-
3032           nally defined by RFC 2279) allows for  up  to  6  bytes,  and  this  is
3033           checked first; hence the possibility of 4 or 5 missing bytes.
3034    
3035             PCRE_UTF8_ERR6
3036             PCRE_UTF8_ERR7
3037             PCRE_UTF8_ERR8
3038             PCRE_UTF8_ERR9
3039             PCRE_UTF8_ERR10
3040    
3041           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
3042           the character do not have the binary value 0b10 (that  is,  either  the
3043           most significant bit is 0, or the next bit is 1).
3044    
3045             PCRE_UTF8_ERR11
3046             PCRE_UTF8_ERR12
3047    
3048           A  character that is valid by the RFC 2279 rules is either 5 or 6 bytes
3049           long; these code points are excluded by RFC 3629.
3050    
3051             PCRE_UTF8_ERR13
3052    
3053           A 4-byte character has a value greater than 0x10fff; these code  points
3054           are excluded by RFC 3629.
3055    
3056             PCRE_UTF8_ERR14
3057    
3058           A  3-byte  character  has  a  value in the range 0xd800 to 0xdfff; this
3059           range of code points are reserved by RFC 3629 for use with UTF-16,  and
3060           so are excluded from UTF-8.
3061    
3062             PCRE_UTF8_ERR15
3063             PCRE_UTF8_ERR16
3064             PCRE_UTF8_ERR17
3065             PCRE_UTF8_ERR18
3066             PCRE_UTF8_ERR19
3067    
3068           A  2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes
3069           for a value that can be represented by fewer bytes, which  is  invalid.
3070           For  example,  the two bytes 0xc0, 0xae give the value 0x2e, whose cor-
3071           rect coding uses just one byte.
3072    
3073             PCRE_UTF8_ERR20
3074    
3075           The two most significant bits of the first byte of a character have the
3076           binary  value 0b10 (that is, the most significant bit is 1 and the sec-
3077           ond is 0). Such a byte can only validly occur as the second  or  subse-
3078           quent byte of a multi-byte character.
3079    
3080             PCRE_UTF8_ERR21
3081    
3082           The  first byte of a character has the value 0xfe or 0xff. These values
3083           can never occur in a valid UTF-8 string.
3084    
3085    
3086  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 2189  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 3218  EXTRACTING CAPTURED SUBSTRINGS BY NAME
3218         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
3219         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
3220    
3221           Warning: If the pattern uses the (?| feature to set up multiple subpat-
3222           terns  with  the  same number, as described in the section on duplicate
3223           subpattern numbers in the pcrepattern page, you  cannot  use  names  to
3224           distinguish  the  different subpatterns, because names are not included
3225           in the compiled code. The matching process uses only numbers. For  this
3226           reason,  the  use of different names for subpatterns of the same number
3227           causes an error at compile time.
3228    
3229    
3230  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
3231    
# Line 2196  DUPLICATE SUBPATTERN NAMES Line 3233  DUPLICATE SUBPATTERN NAMES
3233              const char *name, char **first, char **last);              const char *name, char **first, char **last);
3234    
3235         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for
3236         subpatterns  are  not  required  to  be unique. Normally, patterns with         subpatterns  are not required to be unique. (Duplicate names are always
3237         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  (?|
3238         subpatterns  participates. An example is shown in the pcrepattern docu-         feature.  Indeed,  if  such subpatterns are named, they are required to
3239         mentation. When duplicates are present, pcre_copy_named_substring() and         use the same names.)
3240    
3241           Normally, patterns with duplicate names are such that in any one match,
3242           only  one of the named subpatterns participates. An example is shown in
3243           the pcrepattern documentation.
3244    
3245           When   duplicates   are   present,   pcre_copy_named_substring()    and
3246         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring()  return the first substring corresponding to
3247         the given name that is set.  If  none  are  set,  an  empty  string  is         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING
3248         returned.  The pcre_get_stringnumber() function returns one of the num-         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()
3249         bers that are associated with the name, but it is not defined which  it         function returns one of the numbers that are associated with the  name,
3250         is.         but it is not defined which it is.
3251    
3252         If  you want to get full details of all captured substrings for a given         If  you want to get full details of all captured substrings for a given
3253         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name, you must use  the  pcre_get_stringtable_entries()  function.  The
# Line 2214  DUPLICATE SUBPATTERN NAMES Line 3257  DUPLICATE SUBPATTERN NAMES
3257         the name-to-number table  for  the  given  name.  The  function  itself         the name-to-number table  for  the  given  name.  The  function  itself
3258         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if
3259         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-
3260         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion  entitled  Information about a pattern above.  Given all the rele-
3261         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
3262         the captured data, if any.         hence the captured data, if any.
3263    
3264    
3265  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
# Line 2237  FINDING ALL POSSIBLE MATCHES Line 3280  FINDING ALL POSSIBLE MATCHES
3280         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
3281    
3282    
3283    OBTAINING AN ESTIMATE OF STACK USAGE
3284    
3285           Matching certain patterns using pcre_exec() can use a  lot  of  process
3286           stack,  which  in  certain  environments can be rather limited in size.
3287           Some users find it helpful to have an estimate of the amount  of  stack
3288           that  is  used  by  pcre_exec(),  to help them set recursion limits, as
3289           described in the pcrestack documentation. The estimate that  is  output
3290           by pcretest when called with the -m and -C options is obtained by call-
3291           ing pcre_exec with the values NULL, NULL, NULL, -999, and -999 for  its
3292           first five arguments.
3293    
3294           Normally,  if  its  first  argument  is  NULL,  pcre_exec() immediately
3295           returns the negative error code PCRE_ERROR_NULL, but with this  special
3296           combination  of  arguments,  it returns instead a negative number whose
3297           absolute value is the approximate stack frame size in bytes.  (A  nega-
3298           tive  number  is  used so that it is clear that no match has happened.)
3299           The value is approximate because in  some  cases,  recursive  calls  to
3300           pcre_exec() occur when there are one or two additional variables on the
3301           stack.
3302    
3303           If PCRE has been compiled to use the heap  instead  of  the  stack  for
3304           recursion,  the  value  returned  is  the  size  of  each block that is
3305           obtained from the heap.
3306    
3307    
3308  MATCHING A PATTERN: THE ALTERNATIVE FUNCTION  MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
3309    
3310         int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,         int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
# Line 2250  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 3318  MATCHING A PATTERN: THE ALTERNATIVE FUNC
3318         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics  to  the  normal  algorithm, and is not compatible with
3319         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl. Some of the features of PCRE patterns are not  supported.  Never-
3320         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
3321         a discussion of the two matching algorithms, see the pcrematching docu-         a discussion of the two matching algorithms, and  a  list  of  features
3322         mentation.         that  pcre_dfa_exec() does not support, see the pcrematching documenta-
3323           tion.
3324    
3325         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
3326         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-
3327         ent  way,  and  this is described below. The other common arguments are         ent way, and this is described below. The other  common  arguments  are
3328         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
3329         repeated here.         repeated here.
3330    
3331         The  two  additional  arguments provide workspace for the function. The         The two additional arguments provide workspace for  the  function.  The
3332         workspace vector should contain at least 20 elements. It  is  used  for         workspace  vector  should  contain at least 20 elements. It is used for
3333         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
3334         workspace will be needed for patterns and subjects where  there  are  a         workspace  will  be  needed for patterns and subjects where there are a
3335         lot of potential matches.         lot of potential matches.
3336    
3337         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 2284  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 3353  MATCHING A PATTERN: THE ALTERNATIVE FUNC
3353    
3354     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
3355    
3356         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
3357         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-
3358         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
3359         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART,       PCRE_NO_UTF8_CHECK,      PCRE_BSR_ANYCRLF,
3360         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-
3361         not repeated here.         TIAL_SOFT,  PCRE_DFA_SHORTEST,  and PCRE_DFA_RESTART.  All but the last
3362           four of these are  exactly  the  same  as  for  pcre_exec(),  so  their
3363           PCRE_PARTIAL         description is not repeated here.
3364    
3365         This has the same general effect as it does for  pcre_exec(),  but  the           PCRE_PARTIAL_HARD
3366         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for           PCRE_PARTIAL_SOFT
3367         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into  
3368         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
3369         been no complete matches, but there is still at least one matching pos-         details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for
3370         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-
3371         set as the first matching string.         ject is reached and there is still at least  one  matching  possibility
3372           that requires additional characters. This happens even if some complete
3373           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
3374           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
3375           of the subject is reached, there have been  no  complete  matches,  but
3376           there  is  still  at least one matching possibility. The portion of the
3377           string that was inspected when the longest partial match was  found  is
3378           set  as  the  first  matching  string  in  both cases.  There is a more
3379           detailed discussion of partial and multi-segment matching,  with  exam-
3380           ples, in the pcrepartial documentation.
3381    
3382           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
3383    
3384         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
3385         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-
3386         tive algorithm works, this is necessarily the shortest  possible  match         tive  algorithm  works, this is necessarily the shortest possible match
3387         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
3388    
3389           PCRE_DFA_RESTART           PCRE_DFA_RESTART
3390    
3391         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
3392         returns a partial match, it is possible to call it  again,  with  addi-         again,  with  additional  subject characters, and have it continue with
3393         tional  subject  characters,  and have it continue with the same match.         the same match. The PCRE_DFA_RESTART option requests this action;  when
3394         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
3395         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
3396         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
3397         match.  There  is  more  discussion of this facility in the pcrepartial         pcrepartial documentation.
        documentation.  
3398