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# Line 25  INTRODUCTION Line 25  INTRODUCTION
25         items, and there is an option for requesting some  minor  changes  that         items, and there is an option for requesting some  minor  changes  that
26         give better JavaScript compatibility.         give better JavaScript compatibility.
27    
28           Starting with release 8.30, it is possible to compile two separate PCRE
29           libraries:  the  original,  which  supports  8-bit  character   strings
30           (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         The  current implementation of PCRE corresponds approximately with Perl
45         5.10/5.11, including support for UTF-8 encoded strings and Unicode gen-         5.12, including support for UTF-8/16 encoded strings and  Unicode  gen-
46         eral  category properties. However, UTF-8 and Unicode support has to be         eral  category properties. However, UTF-8/16 and Unicode support has to
47         explicitly enabled; it is not the default. The  Unicode  tables  corre-         be explicitly enabled; it is not the default. The Unicode tables corre-
48         spond to Unicode release 5.2.0.         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 function that matches the same compiled patterns in a  dif-         alternative function that matches the same compiled patterns in a  dif-
# Line 39  INTRODUCTION Line 55  INTRODUCTION
55    
56         PCRE  is  written  in C and released as a C library. A number of people         PCRE  is  written  in C and released as a C library. A number of people
57         have written wrappers and interfaces of various kinds.  In  particular,         have written wrappers and interfaces of various kinds.  In  particular,
58         Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now         Google  Inc.   have  provided a comprehensive C++ wrapper for the 8-bit
59         included as part of the PCRE distribution. The pcrecpp page has details         library. This is now included as part of  the  PCRE  distribution.  The
60         of  this  interface.  Other  people's contributions can be found in the         pcrecpp  page  has  details of this interface. Other people's contribu-
61         Contrib directory at the primary FTP site, which is:         tions can be found in the Contrib directory at the  primary  FTP  site,
62           which is:
63    
64         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
65    
66         Details of exactly which Perl regular expression features are  and  are         Details  of  exactly which Perl regular expression features are and are
67         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
68         tern and pcrecompat pages. There is a syntax summary in the  pcresyntax         tern  and pcrecompat pages. There is a syntax summary in the pcresyntax
69         page.         page.
70    
71         Some  features  of  PCRE can be included, excluded, or changed when the         Some features of PCRE can be included, excluded, or  changed  when  the
72         library is built. The pcre_config() function makes it  possible  for  a         library  is  built.  The pcre_config() function makes it possible for a
73         client  to  discover  which  features are available. The features them-         client to discover which features are  available.  The  features  them-
74         selves are described in the pcrebuild page. Documentation about  build-         selves  are described in the pcrebuild page. Documentation about build-
75         ing  PCRE  for various operating systems can be found in the README and         ing PCRE for various operating systems can be found in the  README  and
76         NON-UNIX-USE files in the source distribution.         NON-UNIX-USE files in the source distribution.
77    
78         The library contains a number of undocumented  internal  functions  and         The  libraries contains a number of undocumented internal functions and
79         data  tables  that  are  used by more than one of the exported external         data tables that are used by more than one  of  the  exported  external
80         functions, but which are not intended  for  use  by  external  callers.         functions,  but  which  are  not  intended for use by external callers.
81         Their  names  all begin with "_pcre_", which hopefully will not provoke         Their names all begin with "_pcre_" or "_pcre16_", which hopefully will
82         any name clashes. In some environments, it is possible to control which         not  provoke  any name clashes. In some environments, it is possible to
83         external  symbols  are  exported when a shared library is built, and in         control which external symbols are exported when a  shared  library  is
84         these cases the undocumented symbols are not exported.         built, and in these cases the undocumented symbols are not exported.
85    
86    
87  USER DOCUMENTATION  USER DOCUMENTATION
88    
89         The user documentation for PCRE comprises a number  of  different  sec-         The  user  documentation  for PCRE comprises a number of different sec-
90         tions.  In the "man" format, each of these is a separate "man page". In         tions. In the "man" format, each of these is a separate "man page".  In
91         the HTML format, each is a separate page, linked from the  index  page.         the  HTML  format, each is a separate page, linked from the index page.
92         In  the  plain  text format, all the sections, except the pcredemo sec-         In the plain text format, all the sections, except  the  pcredemo  sec-
93         tion, are concatenated, for ease of searching. The sections are as fol-         tion, are concatenated, for ease of searching. The sections are as fol-
94         lows:         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           pcredemo          a demonstration C program that uses PCRE           pcredemo          a demonstration C program that uses PCRE
105           pcregrep          description of the pcregrep command           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 pcredemo program           pcresample        discussion of the pcredemo program
116           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
117           pcresyntax        quick syntax reference           pcresyntax        quick syntax reference
118           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
119             pcreunicode       discussion of Unicode and UTF-8/16 support
120    
121         In  addition,  in the "man" and HTML formats, there is a short page for         In addition, in the "man" and HTML formats, there is a short  page  for
122         each C library function, listing its arguments and results.         each 8-bit C library function, listing its arguments and results.
123    
124    
125  LIMITATIONS  AUTHOR
126    
127         There are some size limitations in PCRE but it is hoped that they  will         Philip Hazel
128         never in practice be relevant.         University Computing Service
129           Cambridge CB2 3QH, England.
130    
131         The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE         Putting  an actual email address here seems to have been a spam magnet,
132         is compiled with the default internal linkage size of 2. If you want to         so I've taken it away. If you want to email me, use  my  two  initials,
133         process  regular  expressions  that are truly enormous, you can compile         followed by the two digits 10, at the domain cam.ac.uk.
        PCRE with an internal linkage size of 3 or 4 (see the  README  file  in  
        the  source  distribution and the pcrebuild documentation for details).  
        In these cases the limit is substantially larger.  However,  the  speed  
        of execution is slower.  
134    
        All values in repeating quantifiers must be less than 65536.  
135    
136         There is no limit to the number of parenthesized subpatterns, but there  REVISION
        can be no more than 65535 capturing subpatterns.  
137    
138         The maximum length of name for a named subpattern is 32 characters, and         Last updated: 10 January 2012
139         the maximum number of named subpatterns is 10000.         Copyright (c) 1997-2012 University of Cambridge.
140    ------------------------------------------------------------------------------
141    
        The  maximum  length of a subject string is the largest positive number  
        that an integer variable can hold. However, when using the  traditional  
        matching function, PCRE uses recursion to handle subpatterns and indef-  
        inite repetition.  This means that the available stack space may  limit  
        the size of a subject string that can be processed by certain patterns.  
        For a discussion of stack issues, see the pcrestack documentation.  
142    
143    PCRE(3)                                                                PCRE(3)
144    
 UTF-8 AND UNICODE PROPERTY SUPPORT  
145    
146         From release 3.3, PCRE has  had  some  support  for  character  strings  NAME
147         encoded  in the UTF-8 format. For release 4.0 this was greatly extended         PCRE - Perl-compatible regular expressions
        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,  or the pattern must start with the  
        sequence (*UTF8). When either of these is the case,  both  the  pattern  
        and  any  subject  strings  that  are matched against it are treated as  
        UTF-8 strings instead of strings of 1-byte characters.  
   
        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.  
148    
149         If PCRE is built with Unicode character property support (which implies         #include <pcre.h>
        UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-  
        ported.  The available properties that can be tested are limited to the  
        general category properties such as Lu for an upper case letter  or  Nd  
        for  a  decimal number, the Unicode script names such as Arabic or Han,  
        and the derived properties Any and L&. A full  list  is  given  in  the  
        pcrepattern documentation. Only the short names for properties are sup-  
        ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-  
        ter},  is  not  supported.   Furthermore,  in Perl, many properties may  
        optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE  
        does not support this.  
150    
    Validity of UTF-8 strings  
151    
152         When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and  PCRE 16-BIT API BASIC FUNCTIONS
        subjects are (by default) checked for validity on entry to the relevant  
        functions.  From  release 7.3 of PCRE, the check is according the rules  
        of RFC 3629, which are themselves derived from the  Unicode  specifica-  
        tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which  
        allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current  
        check allows only values in the range U+0 to U+10FFFF, excluding U+D800  
        to U+DFFF.  
   
        The excluded code points are the "Low Surrogate Area"  of  Unicode,  of  
        which  the Unicode Standard says this: "The Low Surrogate Area does not  
        contain any  character  assignments,  consequently  no  character  code  
        charts or namelists are provided for this area. Surrogates are reserved  
        for use with UTF-16 and then must be used in pairs."  The  code  points  
        that  are  encoded  by  UTF-16  pairs are available as independent code  
        points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate  
        thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)  
   
        If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return  
        (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know  
        that your strings are valid, and therefore want to skip these checks in  
        order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at  
        compile  time  or at run time, PCRE assumes that the pattern or subject  
        it is given (respectively) contains only valid  UTF-8  codes.  In  this  
        case, it does not diagnose an invalid UTF-8 string.  
153    
154         If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,         pcre16 *pcre16_compile(PCRE_SPTR16 pattern, int options,
155         what happens depends on why the string is invalid. If the  string  con-              const char **errptr, int *erroffset,
156         forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a              const unsigned char *tableptr);
        string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,  
        apart from the initial validity test, PCRE (when in UTF-8 mode) handles  
        strings according to the more liberal rules of RFC  2279.  However,  if  
        the  string does not even conform to RFC 2279, the result is undefined.  
        Your program may crash.  
157    
158         If you want to process strings  of  values  in  the  full  range  0  to         pcre16 *pcre16_compile2(PCRE_SPTR16 pattern, int options,
159         0x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can              int *errorcodeptr,
160         set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in              const char **errptr, int *erroffset,
161         this situation, you will have to apply your own validity check.              const unsigned char *tableptr);
162    
163     General comments about UTF-8 mode         pcre16_extra *pcre16_study(const pcre16 *code, int options,
164                const char **errptr);
165    
166         1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a         void pcre16_free_study(pcre16_extra *extra);
        two-byte UTF-8 character if the value is greater than 127.  
167    
168         2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8         int pcre16_exec(const pcre16 *code, const pcre16_extra *extra,
169         characters for values greater than \177.              PCRE_SPTR16 subject, int length, int startoffset,
170                int options, int *ovector, int ovecsize);
171    
172         3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-         int pcre16_dfa_exec(const pcre16 *code, const pcre16_extra *extra,
173         vidual bytes, for example: \x{100}{3}.              PCRE_SPTR16 subject, int length, int startoffset,
174                int options, int *ovector, int ovecsize,
175                int *workspace, int wscount);
176    
        4. The dot metacharacter matches one UTF-8 character instead of a  sin-  
        gle byte.  
177    
178         5.  The  escape sequence \C can be used to match a single byte in UTF-8  PCRE 16-BIT API STRING EXTRACTION FUNCTIONS
        mode, but its use can lead to some strange effects.  This  facility  is  
        not available in the alternative matching function, pcre_dfa_exec().  
179    
180         6.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly         int pcre16_copy_named_substring(const pcre16 *code,
181         test characters of any code value, but, by default, the characters that              PCRE_SPTR16 subject, int *ovector,
182         PCRE  recognizes  as digits, spaces, or word characters remain the same              int stringcount, PCRE_SPTR16 stringname,
183         set as before, all with values less than 256. This  remains  true  even              PCRE_UCHAR16 *buffer, int buffersize);
        when  PCRE  is built to include Unicode property support, because to do  
        otherwise would slow down PCRE in many common  cases.  Note  that  this  
        also applies to \b, because it is defined in terms of \w and \W. If you  
        really want to test for a wider sense of, say,  "digit",  you  can  use  
        explicit  Unicode property tests such as \p{Nd}.  Alternatively, if you  
        set the PCRE_UCP option, the way that the  character  escapes  work  is  
        changed  so that Unicode properties are used to determine which charac-  
        ters match. There are more details in the section on generic  character  
        types in the pcrepattern documentation.  
184    
185         7.  Similarly,  characters that match the POSIX named character classes         int pcre16_copy_substring(PCRE_SPTR16 subject, int *ovector,
186         are all low-valued characters, unless the PCRE_UCP option is set.              int stringcount, int stringnumber, PCRE_UCHAR16 *buffer,
187                int buffersize);
188    
189         8. However, the Perl 5.10 horizontal and vertical  whitespace  matching         int pcre16_get_named_substring(const pcre16 *code,
190         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-              PCRE_SPTR16 subject, int *ovector,
191         acters, whether or not PCRE_UCP is set.              int stringcount, PCRE_SPTR16 stringname,
192                PCRE_SPTR16 *stringptr);
193    
194         9. Case-insensitive matching applies only to  characters  whose  values         int pcre16_get_stringnumber(const pcre16 *code,
195         are  less than 128, unless PCRE is built with Unicode property support.              PCRE_SPTR16 name);
196         Even when Unicode property support is available, PCRE  still  uses  its  
197         own  character  tables when checking the case of low-valued characters,         int pcre16_get_stringtable_entries(const pcre16 *code,
198         so as not to degrade performance.  The Unicode property information  is              PCRE_SPTR16 name, PCRE_UCHAR16 **first, PCRE_UCHAR16 **last);
199         used only for characters with higher values. Even when Unicode property  
200         support is available, PCRE supports case-insensitive matching only when         int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector,
201         there  is  a  one-to-one  mapping between a letter's cases. There are a              int stringcount, int stringnumber,
202         small number of many-to-one mappings in Unicode;  these  are  not  sup-              PCRE_SPTR16 *stringptr);
203         ported by PCRE.  
204           int pcre16_get_substring_list(PCRE_SPTR16 subject,
205                int *ovector, int stringcount, PCRE_SPTR16 **listptr);
206    
207           void pcre16_free_substring(PCRE_SPTR16 stringptr);
208    
209           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 260  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: 12 May 2010         Last updated: 14 April 2012
465         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
466  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
467    
468    
# Line 308  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 Unicode 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         or pcre_compile2() functions.         and  UTF-16  independently because that would allow ridiculous settings
560           such as  requesting  UTF-16  support  while  building  only  the  8-bit
561         If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE         library.  It  is not possible to build one library with UTF support and
562         expects its input to be either ASCII or UTF-8 (depending on the runtime         the other without in the same configuration. (For backwards compatibil-
563         option). It is not possible to support both EBCDIC and UTF-8  codes  in         ity, --enable-utf8 is a synonym of --enable-utf.)
564         the  same  version  of  the  library.  Consequently,  --enable-utf8 and  
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.         --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 355  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 the linefeed (LF) character as indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
# Line 401  WHAT \R MATCHES Line 655  WHAT \R MATCHES
655         functions are called.         functions are called.
656    
657    
 BUILDING SHARED AND STATIC LIBRARIES  
   
        The  PCRE building process uses libtool to build both shared and static  
        Unix libraries by default. You can suppress one of these by adding  one  
        of  
   
          --disable-shared  
          --disable-static  
   
        to the configure command, as required.  
   
   
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 436  HANDLING VERY LARGE PATTERNS Line 678  HANDLING VERY LARGE PATTERNS
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 truyl enormous patterns,         Nevertheless,  some  people do want to process truly enormous patterns,
682         so it is possible to compile PCRE to use three-byte or  four-byte  off-         so it is possible to compile PCRE to use three-byte or  four-byte  off-
683         sets by 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
694    
695         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
696         ing by making recursive calls to an internal function  called  match().         ing  by  making recursive calls to an internal function called match().
697         In  environments  where  the size of the stack is limited, this can se-         In environments where the size of the stack is limited,  this  can  se-
698         verely limit PCRE's operation. (The Unix environment does  not  usually         verely  limit  PCRE's operation. (The Unix environment does not usually
699         suffer from this problem, but it may sometimes be necessary to increase         suffer from this problem, but it may sometimes be necessary to increase
700         the maximum stack size.  There is a discussion in the  pcrestack  docu-         the  maximum  stack size.  There is a discussion in the pcrestack docu-
701         mentation.)  An alternative approach to recursion that uses memory from         mentation.) An alternative approach to recursion that uses memory  from
702         the heap to remember data, instead of using recursive  function  calls,         the  heap  to remember data, instead of using recursive function calls,
703         has  been  implemented to work round the problem of limited stack size.         has been implemented to work round the problem of limited  stack  size.
704         If you want to build a version of PCRE that works this way, add         If you want to build a version of PCRE that works this way, add
705    
706           --disable-stack-for-recursion           --disable-stack-for-recursion
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. By default these point to malloc() and free(), but  you         ment  functions. By default these point to malloc() and free(), but you
711         can replace the pointers so that your own functions are used instead.         can replace the pointers so that your own functions are used instead.
712    
713         Separate  functions  are  provided  rather  than  using pcre_malloc and         Separate functions are  provided  rather  than  using  pcre_malloc  and
714         pcre_free because the  usage  is  very  predictable:  the  block  sizes         pcre_free  because  the  usage  is  very  predictable:  the block sizes
715         requested  are  always  the  same,  and  the blocks are always freed in         requested are always the same, and  the  blocks  are  always  freed  in
716         reverse order. A calling program might be able to  implement  optimized         reverse  order.  A calling program might be able to implement optimized
717         functions  that  perform  better  than  malloc()  and free(). PCRE runs         functions that perform better  than  malloc()  and  free().  PCRE  runs
718         noticeably more slowly when built in this way. This option affects only         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().         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         This  is  the  case for most computer operating systems. PCRE can, how-         This is the case for most computer operating systems.  PCRE  can,  how-
775         ever, be compiled to run in an EBCDIC environment by 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.  You  should  only  use  it if you know that you are in an EBCDIC         bles. You should only use it if you know that  you  are  in  an  EBCDIC
781         environment (for example,  an  IBM  mainframe  operating  system).  The         environment  (for  example,  an  IBM  mainframe  operating system). The
782         --enable-ebcdic option is incompatible with --enable-utf8.         --enable-ebcdic option is incompatible with --enable-utf.
783    
784    
785  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
# Line 549  PCREGREP OPTIONS FOR COMPRESSED FILE SUP Line 792  PCREGREP OPTIONS FOR COMPRESSED FILE SUP
792           --enable-pcregrep-libbz2           --enable-pcregrep-libbz2
793    
794         to the configure command. These options naturally require that the rel-         to the configure command. These options naturally require that the rel-
795         evant libraries are installed on your system. Configuration  will  fail         evant  libraries  are installed on your system. Configuration will fail
796         if they are not.         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  PCRETEST OPTION FOR LIBREADLINE SUPPORT
816    
817         If you add         If you add
# Line 586  PCRETEST OPTION FOR LIBREADLINE SUPPORT Line 845  PCRETEST OPTION FOR LIBREADLINE SUPPORT
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 598  AUTHOR Line 857  AUTHOR
857    
858  REVISION  REVISION
859    
860         Last updated: 29 September 2009         Last updated: 07 January 2012
861         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
862  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
863    
864    
# Line 615  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 697  THE ALTERNATIVE MATCHING ALGORITHM Line 958  THE ALTERNATIVE MATCHING ALGORITHM
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.  There  is  an  option to stop the algorithm after the first match         est.  The  matches are returned in decreasing order of length. There is
962         (which is necessarily the shortest) is 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)         8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
1020         are not supported. (*FAIL) is supported, and  behaves  like  a  failing         are not supported. (*FAIL) is supported, and  behaves  like  a  failing
# Line 769  ADVANTAGES OF THE ALTERNATIVE ALGORITHM Line 1032  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
1032         things with callouts.         things with callouts.
1033    
1034         2.  Because  the  alternative  algorithm  scans the subject string just         2.  Because  the  alternative  algorithm  scans the subject string just
1035         once, and never needs to backtrack, it is possible to  pass  very  long         once, and never needs to backtrack (except for lookbehinds), it is pos-
1036         subject  strings  to  the matching function in several pieces, checking         sible  to  pass  very  long subject strings to the matching function in
1037         for partial matching each time.  The  pcrepartial  documentation  gives         several pieces, checking for partial matching each time. Although it is
1038         details of partial matching.         possible  to  do multi-segment matching using the standard algorithm by
1039           retaining partially matched substrings, it  is  more  complicated.  The
1040           pcrepartial  documentation  gives  details of partial matching and dis-
1041           cusses multi-segment matching.
1042    
1043    
1044  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
1045    
1046         The alternative algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
1047    
1048         1.  It  is  substantially  slower  than the standard algorithm. This is         1. It is substantially slower than  the  standard  algorithm.  This  is
1049         partly because it has to search for all possible matches, but  is  also         partly  because  it has to search for all possible matches, but is also
1050         because it is less susceptible to optimization.         because it is less susceptible to optimization.
1051    
1052         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
# Line 798  AUTHOR Line 1064  AUTHOR
1064    
1065  REVISION  REVISION
1066    
1067         Last updated: 29 September 2009         Last updated: 08 January 2012
1068         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
1069  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
1070    
1071    
# Line 809  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 826  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 835  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 866  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 890  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         In a Windows environment, if you want to statically link an application         In a Windows environment, if you want to statically link an application
1219         program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC         program  against  a  non-dll  pcre.a  file, you must define PCRE_STATIC
1220         before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-         before including pcre.h or pcrecpp.h, because otherwise  the  pcre_mal-
1221         loc()   and   pcre_free()   exported   functions   will   be   declared         loc()   and   pcre_free()   exported   functions   will   be   declared
1222         __declspec(dllimport), with unwanted results.         __declspec(dllimport), with unwanted results.
1223    
1224         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The  functions  pcre_compile(),  pcre_compile2(),   pcre_study(),   and
1225         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec()  are used for compiling and matching regular expressions in
1226         a  Perl-compatible  manner. A sample program that demonstrates the sim-         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         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         the PCRE source distribution. A listing of this program is given in the
1229         pcredemo documentation, and the pcresample documentation describes  how         pcredemo  documentation, and the pcresample documentation describes how
1230         to compile and run it.         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  (unless  there         point  in  the  subject), and scans the subject just once (unless there
1246         are  lookbehind  assertions).  However,  this algorithm does not return         are lookbehind assertions). However, this  algorithm  does  not  return
1247         captured substrings. A description of the two matching  algorithms  and         captured  substrings.  A description of the two matching algorithms and
1248         their  advantages  and disadvantages is given in the pcrematching docu-         their advantages and disadvantages is given in the  pcrematching  docu-
1249         mentation.         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 944  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         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         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         the start of the pattern itself; this overrides any other settings. See
1326         the pcrepattern page for details of the special character sequences.         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. There is more detail about this in the         ment for a non-anchored pattern. There is more detail about this in the
1334         section on pcre_exec() options below.         section on pcre_exec() options below.
1335    
1336         The choice of newline convention does not affect the interpretation  of         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,         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.         which is controlled in a similar way, but by separate options.
1339    
1340    
1341  MULTITHREADING  MULTITHREADING
1342    
1343         The PCRE functions can be used in  multi-threading  applications,  with         The  PCRE  functions  can be used in multi-threading applications, with
1344         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
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 1054  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.  Though they are derived from ASCII, the same values         and -1 for ANY.  Though they are derived from ASCII,  the  same  values
1423         are returned in EBCDIC environments. The default should normally corre-         are returned in EBCDIC environments. The default should normally corre-
1424         spond to the standard sequence for your operating system.         spond to the standard sequence for your operating system.
1425    
1426           PCRE_CONFIG_BSR           PCRE_CONFIG_BSR
1427    
1428         The output is an integer whose value indicates what character sequences         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         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         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-         matches only CR, LF, or CRLF. The default can be overridden when a pat-
1432         tern is compiled or matched.         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    
1447         The output is an integer that contains the threshold  above  which  the         The  output  is  an integer that contains the threshold above which the
1448         POSIX  interface  uses malloc() for output vectors. Further details are         POSIX interface uses malloc() for output vectors. Further  details  are
1449         given in the pcreposix documentation.         given in the pcreposix documentation.
1450    
1451           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1452    
1453         The output is a long integer that gives the default limit for the  num-         The  output is a long integer that gives the default limit for the num-
1454         ber  of  internal  matching  function calls in a pcre_exec() execution.         ber of internal matching function calls  in  a  pcre_exec()  execution.
1455         Further 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 a long integer that gives the default limit for the depth         The output is a long integer that gives the default limit for the depth
1460         of   recursion  when  calling  the  internal  matching  function  in  a         of  recursion  when  calling  the  internal  matching  function  in   a
1461         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()         pcre_exec()  execution.  Further  details  are  given  with pcre_exec()
1462         below.         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 1136  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.  To         errorcodeptr,  via  which  a  numerical  error code can be returned. To
1490         avoid  too  much repetition, we refer just to pcre_compile() below, but         avoid too much repetition, we refer just to pcre_compile()  below,  but
1491         the information applies equally to pcre_compile2().         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, but some others as well) can also be set  and         are  compatible with Perl, but some others as well) can also be set and
1510         unset  from  within  the  pattern  (see the detailed description in the         unset from within the pattern (see  the  detailed  description  in  the
1511         pcrepattern documentation). For those options that can be different  in         pcrepattern  documentation). For those options that can be different in
1512         different  parts  of  the pattern, the contents of the options argument         different parts of the pattern, the contents of  the  options  argument
1513         specifies their settings at the start of compilation and execution. The         specifies their settings at the start of compilation and execution. The
1514         PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at         PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK,  and
1515         the time of matching as well as at compile time.         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 byte offset from the start of the  pattern  to  the         try to free it. Normally, the offset from the start of the  pattern  to
1523         character  that  was  being  processed when the error was discovered is         the  byte  that  was  being  processed when the error was discovered is
1524         placed in the variable pointed to by erroffset, which must not be NULL.         placed in the variable pointed to by erroffset, which must not be  NULL
1525         If  it  is,  an  immediate error is given. Some errors are not detected         (if  it is, an immediate error is given). However, for an invalid UTF-8
1526         until checks are carried out when the whole pattern has  been  scanned;         string, the offset is that of the first byte of the failing character.
1527         in this case the offset is set to the end of the pattern.  
1528           Some errors are not detected until the whole pattern has been  scanned;
1529           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-         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         codeptr argument is not NULL, a non-zero error code number is  returned
# Line 1252  COMPILING A PATTERN Line 1606  COMPILING 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    
# Line 1269  COMPILING A PATTERN Line 1625  COMPILING A PATTERN
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         This  option  makes  it possible to include comments inside complicated         Which  characters  are  interpreted  as  newlines  is controlled by the
1637         patterns.  Note, however, that this applies only  to  data  characters.         options passed to pcre_compile() or by a special sequence at the  start
1638         Whitespace   characters  may  never  appear  within  special  character         of  the  pattern, as described in the section entitled "Newline conven-
1639         sequences in a pattern, for  example  within  the  sequence  (?(  which         tions" in the pcrepattern documentation. Note that the end of this type
1640         introduces a conditional subpattern.         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
1644           patterns.   Note,  however,  that this applies only to data characters.
1645           White space  characters  may  never  appear  within  special  character
1646           sequences in a pattern, for example within the sequence (?( that intro-
1647           duces a conditional subpattern.
1648    
1649           PCRE_EXTRA           PCRE_EXTRA
1650    
1651         This  option  was invented in order to turn on additional functionality         This option was invented in order to turn on  additional  functionality
1652         of PCRE that is incompatible with Perl, but it  is  currently  of  very         of  PCRE  that  is  incompatible with Perl, but it is currently of very
1653         little  use. When set, any backslash in a pattern that is followed by a         little use. When set, any backslash in a pattern that is followed by  a
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 an error for this, by         literal. (Perl can, however, be persuaded to give an error for this, by
1658         running it with the -w option.) There are at present no other  features         running  it with the -w option.) There are at present no other features
1659         controlled  by this option. It can also be set by a (?X) option setting         controlled by this option. It can also be set by a (?X) option  setting
1660         within a pattern.         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           PCRE_JAVASCRIPT_COMPAT
1669    
1670         If this option is set, PCRE's behaviour is changed in some ways so that         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         it is compatible with JavaScript rather than Perl. The changes  are  as
1672         follows:         follows:
1673    
1674         (1) A lone closing square bracket in a pattern  causes  a  compile-time         (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         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         as a data character). Thus, the pattern AB]CD becomes illegal when this
1677         option is set.         option is set.
1678    
1679         (2)  At run time, a back reference to an unset subpattern group matches         (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-         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         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         set  (assuming  it can find an "a" in the subject), whereas it fails by
1683         default, for Perl compatibility.         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
1702         line of characters (even if it actually contains newlines). The  "start         line  of characters (even if it actually contains newlines). The "start
1703         of  line"  metacharacter  (^)  matches only at the start of the string,         of line" metacharacter (^) matches only at the  start  of  the  string,
1704         while the "end of line" metacharacter ($) matches only at  the  end  of         while  the  "end  of line" metacharacter ($) matches only at the end of
1705         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1706         is set). This is the same as Perl.         is set). This is the same as Perl.
1707    
1708         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"
1709         constructs  match  immediately following or immediately before internal         constructs match immediately following or immediately  before  internal
1710         newlines in the subject string, respectively, as well as  at  the  very         newlines  in  the  subject string, respectively, as well as at the very
1711         start  and  end.  This is equivalent to Perl's /m option, and it can be         start and end. This is equivalent to Perl's /m option, and  it  can  be
1712         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1713         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
1714         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1715    
1716           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1342  COMPILING A PATTERN Line 1719  COMPILING A PATTERN
1719           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1720           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1721    
1722         These options override the default newline definition that  was  chosen         These  options  override the default newline definition that was chosen
1723         when  PCRE  was built. Setting the first or the second specifies that a         when PCRE was built. Setting the first or the second specifies  that  a
1724         newline is indicated by a single character (CR  or  LF,  respectively).         newline  is  indicated  by a single character (CR or LF, respectively).
1725         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1726         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
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
1737         used  (default  plus the five values above). This means that if you set         used (default plus the five values above). This means that if  you  set
1738         more than one newline option, the combination may or may not be  sensi-         more  than one newline option, the combination may or may not be sensi-
1739         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
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.
# Line 1382  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           PCRE_UCP
1770    
1771         This option changes the way PCRE processes \b, \d, \s, \w, and some  of         This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1772         the POSIX character classes. By default, only ASCII characters are rec-         \w,  and  some  of  the POSIX character classes. By default, only ASCII
1773         ognized, but if PCRE_UCP is set, Unicode properties are used instead to         characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1774         classify  characters.  More details are given in the section on generic         are  used instead to classify characters. More details are given in the
1775         character types in the pcrepattern page. If you set PCRE_UCP,  matching         section on generic character types in the pcrepattern page. If you  set
1776         one  of the items it affects takes much longer. The option is available         PCRE_UCP,  matching  one of the items it affects takes much longer. The
1777         only if PCRE has been compiled with Unicode property support.         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.  There  is  a  discussion about the validity of         automatically  checked.  There  is  a  discussion about the validity of
1799         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of         UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence  is
1800         bytes  is  found,  pcre_compile() returns an error. If you already know         found,  pcre_compile()  returns an error. If you already know that your
1801         that your pattern is valid, and you want to skip this check for perfor-         pattern is valid, and you want to skip this check for performance  rea-
1802         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is         sons,  you  can set the PCRE_NO_UTF8_CHECK option.  When it is set, the
1803         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is         effect of passing an invalid UTF-8 string as a pattern is undefined. It
1804         undefined.  It  may  cause your program to crash. Note that this option         may  cause  your  program  to  crash. Note that this option can also be
1805         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the         passed to pcre_exec() and pcre_dfa_exec(),  to  suppress  the  validity
1806         UTF-8 validity checking of subject strings.         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 1461  COMPILATION ERROR CODES Line 1847  COMPILATION ERROR CODES
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 10000)           49  too many named subpatterns (maximum 10000)
1868           50  [this code is not in use]           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           53  internal error: previously-checked referenced subpattern
1872                 not found                 not found
# Line 1499  COMPILATION ERROR CODES Line 1885  COMPILATION ERROR CODES
1885           65  different names for subpatterns of the same number are           65  different names for subpatterns of the same number are
1886                 not allowed                 not allowed
1887           66  (*MARK) must have an argument           66  (*MARK) must have an argument
1888           67  this version of PCRE is not compiled with PCRE_UCP support           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         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.         values may be used if the limits were changed when PCRE was built.
# Line 1528  STUDYING A PATTERN Line 1923  STUDYING A PATTERN
1923         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or
1924         pcre_dfa_exec(), it must set up 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. At present,         The  second  argument  of  pcre_study() contains option bits. There are
1927         no options are defined, and this argument should always be zero.         three options:
1928    
1929             PCRE_STUDY_JIT_COMPILE
1930             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
# Line 1538  STUDYING A PATTERN Line 1951  STUDYING A PATTERN
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               re, sd, "subject", 7, 0, 0, ovector, 30);
1974             ...
1975             pcre_free_study(sd);
1976             pcre_free(re);
1977    
1978         Studying a pattern does two things: first, a lower bound for the length         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         of subject string that is needed to match the pattern is computed. This
# Line 1557  STUDYING A PATTERN Line 1986  STUDYING A PATTERN
1986         Studying a pattern is also useful for non-anchored patterns that do not         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         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         bytes  is  created. This speeds up finding a position in the subject at
1989         which to start matching.         which to start matching. (In 16-bit mode, the bitmap is used for 16-bit
1990           values less than 256.)
1991    
1992         The two optimizations just described can be  disabled  by  setting  the         These  two optimizations apply to both pcre_exec() and pcre_dfa_exec(),
1993         PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or         and the information is also used by the JIT  compiler.   The  optimiza-
1994         pcre_dfa_exec(). You might want to do this  if  your  pattern  contains         tions can be disabled by setting the PCRE_NO_START_OPTIMIZE option when
1995         callouts,  or  make  use of (*MARK), and you make use of these in cases         calling pcre_exec() or pcre_dfa_exec(), but if this is done, JIT execu-
1996         where matching fails.  See  the  discussion  of  PCRE_NO_START_OPTIMIZE         tion  is  also disabled. You might want to do this if your pattern con-
1997         below.         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
2003    
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. By  default,  higher-valued  codes         characters  with  codes  less than 128. By default, higher-valued codes
2008         never match escapes such as \w or \d, but they can be tested with \p if         never match escapes such as \w or \d, but they can be tested with \p if
2009         PCRE is built with Unicode character property  support.  Alternatively,         PCRE  is  built with Unicode character property support. Alternatively,
2010         the  PCRE_UCP  option  can  be  set at compile time; this causes \w and         the PCRE_UCP option can be set at compile  time;  this  causes  \w  and
2011         friends to use Unicode property support instead of built-in tables. The         friends to use Unicode property support instead of built-in tables. The
2012         use of locales with Unicode is discouraged. If you are handling charac-         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-         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.         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
2018         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
2019         acters. However, when PCRE is built, it is possible to cause the inter-         acters. However, when PCRE is built, it is possible to cause the inter-
2020         nal tables to be rebuilt in the default "C" locale of the local system,         nal tables to be rebuilt in the default "C" locale of the local system,
2021         which may cause them to be different.         which may cause them to be different.
2022    
2023         The internal tables can always be overridden by tables supplied by  the         The  internal tables can always be overridden by tables supplied by the
2024         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
2025         from the default. As more and more applications change  to  using  Uni-         from  the  default.  As more and more applications change to using Uni-
2026         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
2027    
2028         External  tables  are  built by calling the pcre_maketables() function,         External tables are built by calling  the  pcre_maketables()  function,
2029         which has no arguments, in the relevant locale. The result can then  be         which  has no arguments, in the relevant locale. The result can then be
2030         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
2031         example, to build and use tables that are appropriate  for  the  French         example,  to  build  and use tables that are appropriate for the French
2032         locale  (where  accented  characters  with  values greater than 128 are         locale (where accented characters with  values  greater  than  128  are
2033         treated as letters), the following code could be used:         treated as letters), the following code could be used:
2034    
2035           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
2036           tables = pcre_maketables();           tables = pcre_maketables();
2037           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
2038    
2039         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;         The  locale  name "fr_FR" is used on Linux and other Unix-like systems;
2040         if you are using Windows, the name for the French locale is "french".         if you are using Windows, the name for the French locale is "french".
2041    
2042         When  pcre_maketables()  runs,  the  tables are built in memory that is         When pcre_maketables() runs, the tables are built  in  memory  that  is
2043         obtained via pcre_malloc. It is the caller's responsibility  to  ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
2044         that  the memory containing the tables remains available for as long as         that the memory containing the tables remains available for as long  as
2045         it is needed.         it is needed.
2046    
2047         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
2048         pattern,  and the same tables are used via this pointer by pcre_study()         pattern, and the same tables are used via this pointer by  pcre_study()
2049         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
2050         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
2051         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
2052    
2053         It is possible to pass a table pointer or NULL (indicating the  use  of         It  is  possible to pass a table pointer or NULL (indicating the use of
2054         the  internal  tables)  to  pcre_exec(). Although not intended for this         the internal tables) to pcre_exec(). Although  not  intended  for  this
2055         purpose, this facility could be used to match a pattern in a  different         purpose,  this facility could be used to match a pattern in a different
2056         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
2057         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
2058    
# Line 1630  INFORMATION ABOUT A PATTERN Line 2062  INFORMATION ABOUT A PATTERN
2062         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
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
2071         the pattern was not studied. The third argument specifies  which  piece         the  pattern  was not studied. The third argument specifies which piece
2072         of  information  is required, and the fourth argument is a pointer to a         of information is required, and the fourth argument is a pointer  to  a
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         The  "magic  number" is placed at the start of each compiled pattern as           PCRE_ERROR_BADOPTION      the value of what was invalid
2082         an simple check against passing an arbitrary memory pointer. Here is  a  
2083         typical  call  of pcre_fullinfo(), to obtain the length of the compiled         The "magic number" is placed at the start of each compiled  pattern  as
2084         pattern:         an  simple check against passing an arbitrary memory pointer. The endi-
2085           anness error can occur if a compiled pattern is saved and reloaded on a
2086           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    
# Line 1683  INFORMATION ABOUT A PATTERN Line 2118  INFORMATION ABOUT A PATTERN
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
# Line 1704  INFORMATION ABOUT A PATTERN Line 2143  INFORMATION ABOUT A PATTERN
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           PCRE_INFO_HASCRORLF
2152    
# Line 1722  INFORMATION ABOUT A PATTERN Line 2161  INFORMATION ABOUT A PATTERN
2161         otherwise 0. The fourth argument should point to an int variable.  (?J)         otherwise 0. The fourth argument should point to an int variable.  (?J)
2162         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.         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           PCRE_INFO_MINLENGTH
2198    
2199         If  the  pattern  was studied and a minimum length for matching subject         If the pattern was studied and a minimum length  for  matching  subject
2200         strings was computed, its value is  returned.  Otherwise  the  returned         strings  was  computed,  its  value is returned. Otherwise the returned
2201         value  is  -1. The value is a number of characters, not bytes (this may         value is -1. The value is a number of characters, which in  UTF-8  mode
2202         be relevant in UTF-8 mode). The fourth argument should point to an  int         may  be  different from the number of bytes. The fourth argument should
2203         variable.  A  non-negative  value is a lower bound to the length of any         point to an int variable. A non-negative value is a lower bound to  the
2204         matching string. There may not be any strings of that  length  that  do         length  of  any  matching  string. There may not be any strings of that
2205         actually match, but every string that does match is at least that long.         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
# Line 1760  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.         16-bit library, the pointer points to 16-bit data units, the  first  of
2230           which  contains  the  parenthesis  number. The rest of the entry is the
2231           corresponding name, zero terminated.
2232    
2233         The names are in alphabetical order. Duplicate names may appear if  (?|         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         is used to create multiple groups with the same number, as described in
# Line 1776  INFORMATION ABOUT A PATTERN Line 2241  INFORMATION ABOUT A PATTERN
2241         terns may have lower numbers.         terns may have lower numbers.
2242    
2243         As a simple example of the name/number table,  consider  the  following         As a simple example of the name/number table,  consider  the  following
2244         pattern  (assume  PCRE_EXTENDED is set, so white space - including new-         pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is
2245         lines - is ignored):         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 1830  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().  If pcre_extra is NULL, or there is no study         size_t  variable. The study_data field is set by pcre_study() to record
2313         data, zero is returned. The fourth argument should point  to  a  size_t         information that will speed  up  matching  (see  the  section  entitled
2314         variable.         "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           be  saved  and  restored  (see  the  pcreprecompile  documentation  for
2317  OBSOLETE INFO FUNCTION         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
2321    
2322         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
2323    
2324         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
2325         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
2326         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
2327         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
2328         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
2329    
2330         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
2331         zero.  It is changed only by calling this function, whose action is  to         zero.   It is changed only by calling this function, whose action is to
2332         add  the  adjust  value  (which may be positive or negative) to it. The         add the adjust value (which may be positive or  negative)  to  it.  The
2333         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
2334         is  constrained to lie between 0 and 65535, inclusive. If the new value         is constrained to lie between 0 and 65535, inclusive. If the new  value
2335         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
2336    
2337         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
2338         if  a  pattern  is  compiled on one host and then transferred to a host         if a pattern is compiled on one host and then  transferred  to  a  host
2339         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
2340    
2341    
# Line 1895  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         was 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 1925  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;           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
          PCRE_EXTRA_MARK  
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
# Line 1961  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2420  MATCHING A PATTERN: THE TRADITIONAL FUNC
2420         search trees. The classic example is a pattern that uses nested  unlim-         search trees. The classic example is a pattern that uses nested  unlim-
2421         ited 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         The  default  value  for  match_limit_recursion can be set when PCRE is         compiled code.
2455         built; the default default  is  the  same  value  as  the  default  for  
2456         match_limit.  You can override the default by suppling pcre_exec() with         The default value for match_limit_recursion can be  set  when  PCRE  is
2457         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         built;  the  default  default  is  the  same  value  as the default for
2458         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the         match_limit. You can override the default by suppling pcre_exec()  with
2459           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
2460           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 callout_data field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
2464         ture, and 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
2468         pattern.  A  non-NULL value is stored with the compiled pattern only if         pattern. A non-NULL value is stored with the compiled pattern  only  if
2469         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
2470         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2471         PCRE's internal tables to be used. This facility is  helpful  when  re-         PCRE's  internal  tables  to be used. This facility is helpful when re-
2472         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
2473         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
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         If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2478         set  to  point  to a char * variable. If the pattern contains any back-         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         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-         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         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         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.         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         If there is no name to pass back, the variable pointed to by  the  mark
2485         field set to NULL. For details of the backtracking control  verbs,  see         field  is  set  to NULL. For details of the backtracking control verbs,
2486         the section entitled "Backtracking control" in the pcrepattern documen-         see the section entitled "Backtracking control" in the pcrepattern doc-
2487         tation.         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_NOTEMPTY_ATSTART,         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2494         PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_HARD,   and
2495         PCRE_PARTIAL_HARD.         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 2123  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2598  MATCHING A PATTERN: THE TRADITIONAL FUNC
2598         set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that         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-         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         nary  match  again. There is some code that demonstrates how to do this
2601         in the pcredemo sample program.         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           PCRE_NO_START_OPTIMIZE
2607    
2608         There are a number of optimizations that pcre_exec() uses at the  start         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         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         known that an unanchored match must start with a specific character, it
2611         searches  the  subject  for that character, and fails immediately if it         searches the subject for that character, and fails  immediately  if  it
2612         cannot find it, without actually running the  main  matching  function.         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-         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         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         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         "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-         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.         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,         The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2621         possibly  causing  performance  to  suffer,  but ensuring that in cases         possibly causing performance to suffer,  but  ensuring  that  in  cases
2622         where the result is "no match", the callouts do occur, and  that  items         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         such as (*COMMIT) and (*MARK) are considered at every possible starting
2624         position in the subject  string.   Setting  PCRE_NO_START_OPTIMIZE  can         position  in  the  subject  string. If PCRE_NO_START_OPTIMIZE is set at
2625         change the outcome of a matching operation.  Consider the pattern         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           (*COMMIT)ABC
2633    
# Line 2175  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2658  MATCHING A PATTERN: THE TRADITIONAL FUNC
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. There is a discussion about         place.  The  value  of  startoffset  is  also checked to ensure that it
2663         the validity of UTF-8 strings in the section on UTF-8  support  in  the         points to the start of a UTF-8 character. There is a  discussion  about
2664         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,         the  validity  of  UTF-8 strings in the pcreunicode page. If an invalid
2665         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-         sequence  of  bytes   is   found,   pcre_exec()   returns   the   error
2666         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.         PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
2667           truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
2668           both  cases, information about the precise nature of the error may also
2669           be returned (see the descriptions of these errors in the section  enti-
2670           tled  Error return values from pcre_exec() below).  If startoffset con-
2671           tains a value that does not point to the start of a UTF-8 character (or
2672           to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2673    
2674         If  you  already  know that your subject is valid, and you want to skip         If  you  already  know that your subject is valid, and you want to skip
2675         these   checks   for   performance   reasons,   you   can    set    the         these   checks   for   performance   reasons,   you   can    set    the
# Line 2188  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2677  MATCHING A PATTERN: THE TRADITIONAL FUNC
2677         do this for the second and subsequent calls to pcre_exec() if  you  are         do this for the second and subsequent calls to pcre_exec() if  you  are
2678         making  repeated  calls  to  find  all  the matches in a single subject         making  repeated  calls  to  find  all  the matches in a single subject
2679         string. However, you should be  sure  that  the  value  of  startoffset         string. However, you should be  sure  that  the  value  of  startoffset
2680         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         points  to  the  start of a character (or the end of the subject). When
2681         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid string as a
2682         value  of startoffset that does not point to the start of a UTF-8 char-         subject  or  an invalid value of startoffset is undefined. Your program
2683         acter, is undefined. Your program may crash.         may crash.
2684    
2685           PCRE_PARTIAL_HARD           PCRE_PARTIAL_HARD
2686           PCRE_PARTIAL_SOFT           PCRE_PARTIAL_SOFT
# Line 2200  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2689  MATCHING A PATTERN: THE TRADITIONAL FUNC
2689         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial         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,         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         but  there  are not enough subject characters to complete the match. If
2692         this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2693         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,         matching  continues  by  testing any remaining alternatives. Only if no
2694         matching continues by testing any other alternatives. Only if they  all         complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
2695         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).         PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
2696         The portion of the string that was inspected when the partial match was         caller is prepared to handle a partial match, but only if  no  complete
2697         found  is  set  as  the first matching string. There is a more detailed         match can be found.
2698         discussion in the pcrepartial documentation.  
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 bytes) in length, and a starting byte offset in startoffset.         length  in  bytes in length, and a starting byte offset in startoffset.
2714         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-         If this is  negative  or  greater  than  the  length  of  the  subject,
2715         acter.  Unlike  the pattern string, the subject may contain binary zero         pcre_exec()  returns  PCRE_ERROR_BADOFFSET. When the starting offset is
2716         bytes. When the starting offset is zero, the search for a match  starts         zero, the search for a match starts at the beginning  of  the  subject,
2717         at  the  beginning  of  the subject, and this is by far the most common         and this is by far the most common case. In UTF-8 mode, the byte offset
2718         case.         must point to the start of a UTF-8 character (or the end  of  the  sub-
2719           ject).  Unlike  the pattern string, the subject may contain binary zero
2720           bytes.
2721    
2722         A non-zero starting offset is useful when searching for  another  match         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-         in  the same subject by calling pcre_exec() again after a previous suc-
# Line 2237  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2738  MATCHING A PATTERN: THE TRADITIONAL FUNC
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         If  a  non-zero starting offset is passed when the pattern is anchored,         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,
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
2755         subject.         subject.
2756    
2757     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2758    
2759         In general, a pattern matches a certain portion of the subject, and  in         In  general, a pattern matches a certain portion of the subject, and in
2760         addition,  further  substrings  from  the  subject may be picked out by         addition, further substrings from the subject  may  be  picked  out  by
2761         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,
2762         this  is  called "capturing" in what follows, and the phrase "capturing         this is called "capturing" in what follows, and the  phrase  "capturing
2763         subpattern" is used for a fragment of a pattern that picks out  a  sub-         subpattern"  is  used for a fragment of a pattern that picks out a sub-
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 integers         Captured substrings are returned to the caller via a vector of integers
2768         whose  address is passed in ovector. The number of elements in the vec-         whose address is passed in ovector. The number of elements in the  vec-
2769         tor is passed in ovecsize, which must be a non-negative  number.  Note:         tor  is  passed in ovecsize, which must be a non-negative number. Note:
2770         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  number 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  each pair is set to the byte offset of the first character         element of each pair is set to the byte offset of the  first  character
2783         in a substring, and the second is set to the byte offset of  the  first         in  a  substring, and the second is set to the byte offset of the first
2784         character  after  the end of a substring. Note: these values are always         character after the end of a substring. Note: these values  are  always
2785         byte offsets, even in UTF-8 mode. They are not character counts.         byte offsets, even in UTF-8 mode. They are not character counts.
2786    
2787         The first pair of integers, ovector[0]  and  ovector[1],  identify  the         The  first  pair  of  integers, ovector[0] and ovector[1], identify the
2788         portion  of  the subject string matched by the entire pattern. The next         portion of the subject string matched by the entire pattern.  The  next
2789         pair is used for the first capturing subpattern, and so on.  The  value         pair  is  used for the first capturing subpattern, and so on. The value
2790         returned by pcre_exec() is one more than the highest numbered pair that         returned by pcre_exec() is one more than the highest numbered pair that
2791         has been set.  For example, if two substrings have been  captured,  the         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         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         value from a successful match is 1, indicating that just the first pair
2794         of offsets has been set.         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. If the substring offsets are  not  of         function  returns a value of zero. If neither the actual string matched
2802         interest,  pcre_exec()  may  be  called with ovector passed as NULL and         nor any captured substrings are of interest, pcre_exec() may be  called
2803         ovecsize as zero. However, if the pattern contains back references  and         with  ovector passed as NULL and ovecsize as zero. However, if the pat-
2804         the  ovector is not big enough to remember the related substrings, PCRE         tern contains back references and the ovector  is  not  big  enough  to
2805         has to get additional memory for use during matching. Thus it  is  usu-         remember  the related substrings, PCRE has to get additional memory for
2806         ally advisable to supply an ovector.         use during matching. Thus it is usually advisable to supply an  ovector
2807           of reasonable size.
2808    
2809           There  are  some  cases where zero is returned (indicating vector over-
2810           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         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         subpatterns  there  are  in  a  compiled pattern. The smallest size for
2826         ovector  that  will allow for n captured substrings, in addition to the         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 2327  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 2336  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().         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-         This can happen only when PCRE has been compiled with  --disable-stack-
2895         for-recursion.         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         This code is no longer in  use.  It  was  formerly  returned  when  the         This  code  is  no  longer  in  use.  It was formerly returned when the
2942         PCRE_PARTIAL  option  was used with a compiled pattern containing items         PCRE_PARTIAL option was used with a compiled pattern  containing  items
2943         that were  not  supported  for  partial  matching.  From  release  8.00         that  were  not  supported  for  partial  matching.  From  release 8.00
2944         onwards, there are no restrictions on partial matching.         onwards, there are no restrictions on partial matching.
2945    
2946           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2947    
2948         An  unexpected  internal error has occurred. This error could be caused         An unexpected internal error has occurred. This error could  be  caused
2949         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2950    
2951           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
# Line 2413  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2955  MATCHING A PATTERN: THE TRADITIONAL FUNC
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    
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 and -22 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 2597  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 2620  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 2690  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 3375  MATCHING A PATTERN: THE ALTERNATIVE FUNC
3375         of the subject is reached, there have been  no  complete  matches,  but         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         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         string that was inspected when the longest partial match was  found  is
3378         set as the first matching string in both cases.         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    
# Line 2741  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 3428  MATCHING A PATTERN: THE ALTERNATIVE FUNC
3428         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
3429         est matching string is given first. If there were too many  matches  to         est matching string is given first. If there were too many  matches  to
3430         fit  into ovector, the yield of the function is zero, and the vector is         fit  into ovector, the yield of the function is zero, and the vector is
3431         filled with the longest matches.         filled with the longest matches.  Unlike  pcre_exec(),  pcre_dfa_exec()
3432           can use the entire ovector for returning matched strings.
3433    
3434     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
3435    
3436         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
3437         Many  of  the  errors  are  the  same as for pcre_exec(), and these are         Many of the errors are the same  as  for  pcre_exec(),  and  these  are
3438         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
3439         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
3440    
3441           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
3442    
3443         This  return is given if pcre_dfa_exec() encounters an item in the pat-         This return is given if pcre_dfa_exec() encounters an item in the  pat-
3444         tern that it does not support, for instance, the use of \C  or  a  back         tern  that  it  does not support, for instance, the use of \C or a back
3445         reference.         reference.
3446    
3447           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
3448    
3449         This  return  is  given  if pcre_dfa_exec() encounters a condition item         This return is given if pcre_dfa_exec()  encounters  a  condition  item
3450         that uses a back reference for the condition, or a test  for  recursion         that  uses  a back reference for the condition, or a test for recursion
3451         in a specific group. These are not supported.         in a specific group. These are not supported.
3452    
3453           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
3454    
3455         This  return  is given if pcre_dfa_exec() is called with an extra block         This return is given if pcre_dfa_exec() is called with an  extra  block
3456         that contains a setting of the match_limit field. This is not supported         that  contains  a  setting  of the match_limit or match_limit_recursion
3457         (it is meaningless).         fields. This is not supported (these fields  are  meaningless  for  DFA
3458           matching).
3459    
3460           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
3461    
# Line 2780  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 3469  MATCHING A PATTERN: THE ALTERNATIVE FUNC
3469         This error is given if the output vector  is  not  large  enough.  This         This error is given if the output vector  is  not  large  enough.  This
3470         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
3471    
3472             PCRE_ERROR_DFA_BADRESTART (-30)
3473    
3474           When  pcre_dfa_exec()  is called with the PCRE_DFA_RESTART option, some
3475           plausibility checks are made on the contents of  the  workspace,  which
3476           should  contain  data about the previous partial match. If any of these
3477           checks fail, this error is given.
3478    
3479    
3480  SEE ALSO  SEE ALSO
3481    
3482         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcre16(3),  pcrebuild(3),  pcrecallout(3),  pcrecpp(3)(3),   pcrematch-
3483         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         ing(3), pcrepartial(3), pcreposix(3), pcreprecompile(3), pcresample(3),
3484           pcrestack(3).
3485    
3486    
3487  AUTHOR  AUTHOR
# Line 2796  AUTHOR Line 3493  AUTHOR
3493    
3494  REVISION  REVISION
3495    
3496         Last updated: 21 June 2010         Last updated: 04 May 2012
3497         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
3498  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3499    
3500    
# Line 2812  PCRE CALLOUTS Line 3509  PCRE CALLOUTS
3509    
3510         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
3511    
3512           int (*pcre16_callout)(pcre16_callout_block *);
3513    
3514         PCRE provides a feature called "callout", which is a means of temporar-         PCRE provides a feature called "callout", which is a means of temporar-
3515         ily passing control to the caller of PCRE  in  the  middle  of  pattern         ily passing control to the caller of PCRE  in  the  middle  of  pattern
3516         matching.  The  caller of PCRE provides an external function by putting         matching.  The  caller of PCRE provides an external function by putting
3517         its entry point in the global variable pcre_callout. By  default,  this         its entry point in the global variable pcre_callout (pcre16_callout for
3518         variable contains NULL, which disables all calling out.         the  16-bit  library).  By  default, this variable contains NULL, which
3519           disables all calling out.
3520    
3521         Within  a  regular  expression,  (?C) indicates the points at which the         Within a regular expression, (?C) indicates the  points  at  which  the
3522         external function is to be called.  Different  callout  points  can  be         external  function  is  to  be  called. Different callout points can be
3523         identified  by  putting  a number less than 256 after the letter C. The         identified by putting a number less than 256 after the  letter  C.  The
3524         default value is zero.  For  example,  this  pattern  has  two  callout         default  value  is  zero.   For  example,  this pattern has two callout
3525         points:         points:
3526    
3527           (?C1)abc(?C2)def           (?C1)abc(?C2)def
3528    
3529         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() or         If the PCRE_AUTO_CALLOUT option bit is set when a pattern is  compiled,
3530         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all         PCRE  automatically  inserts callouts, all with number 255, before each
3531         with  number  255,  before  each  item  in the pattern. For example, if         item in the pattern. For example, if PCRE_AUTO_CALLOUT is used with the
3532         PCRE_AUTO_CALLOUT is used with the pattern         pattern
3533    
3534           A(\d{2}|--)           A(\d{2}|--)
3535    
# Line 2837  PCRE CALLOUTS Line 3537  PCRE CALLOUTS
3537    
3538         (?C255)A(?C255)((?C255)\d{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255)         (?C255)A(?C255)((?C255)\d{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255)
3539    
3540         Notice that there is a callout before and after  each  parenthesis  and         Notice  that  there  is a callout before and after each parenthesis and
3541         alternation  bar.  Automatic  callouts  can  be  used  for tracking the         alternation bar. Automatic  callouts  can  be  used  for  tracking  the
3542         progress of pattern matching. The pcretest command has an  option  that         progress  of  pattern matching. The pcretest command has an option that
3543         sets  automatic callouts; when it is used, the output indicates how the         sets automatic callouts; when it is used, the output indicates how  the
3544         pattern is matched. This is useful information when you are  trying  to         pattern  is  matched. This is useful information when you are trying to
3545         optimize the performance of a particular pattern.         optimize the performance of a particular pattern.
3546    
3547           The use of callouts in a pattern makes it ineligible  for  optimization
3548           by  the  just-in-time  compiler.  Studying  such  a  pattern  with  the
3549           PCRE_STUDY_JIT_COMPILE option always fails.
3550    
3551    
3552  MISSING CALLOUTS  MISSING CALLOUTS
3553    
3554         You  should  be  aware  that,  because of optimizations in the way PCRE         You should be aware that, because of  optimizations  in  the  way  PCRE
3555         matches patterns by default, callouts  sometimes  do  not  happen.  For         matches  patterns  by  default,  callouts  sometimes do not happen. For
3556         example, if the pattern is         example, if the pattern is
3557    
3558           ab(?C4)cd           ab(?C4)cd
3559    
3560         PCRE knows that any matching string must contain the letter "d". If the         PCRE knows that any matching string must contain the letter "d". If the
3561         subject string is "abyz", the lack of "d" means that  matching  doesn't         subject  string  is "abyz", the lack of "d" means that matching doesn't
3562         ever  start,  and  the  callout is never reached. However, with "abyd",         ever start, and the callout is never  reached.  However,  with  "abyd",
3563         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
3564    
3565         If the pattern is studied, PCRE knows the minimum length of a  matching         If  the pattern is studied, PCRE knows the minimum length of a matching
3566         string,  and will immediately give a "no match" return without actually         string, and will immediately give a "no match" return without  actually
3567         running a match if the subject is not long enough, or,  for  unanchored         running  a  match if the subject is not long enough, or, for unanchored
3568         patterns, if it has been scanned far enough.         patterns, if it has been scanned far enough.
3569    
3570         You  can disable these optimizations by passing the PCRE_NO_START_OPTI-         You can disable these optimizations by passing the  PCRE_NO_START_OPTI-
3571         MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the         MIZE  option  to the matching function, or by starting the pattern with
3572         matching  process,  but  does  ensure that callouts such as the example         (*NO_START_OPT). This slows down the matching process, but does  ensure
3573         above are obeyed.         that callouts such as the example above are obeyed.
3574    
3575    
3576  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
3577    
3578         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
3579         tion  defined by pcre_callout is called (if it is set). This applies to         tion defined by pcre_callout or pcre16_callout  is  called  (if  it  is
3580         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         set).   This applies to both normal and DFA matching. The only argument
3581         only  argument  to  the callout function is a pointer to a pcre_callout         to the callout function is a pointer to a pcre_callout or  pcre16_call-
3582         block. This structure contains the following fields:         out block.  These structures contains the following fields:
3583    
3584           int          version;           int           version;
3585           int          callout_number;           int           callout_number;
3586           int         *offset_vector;           int          *offset_vector;
3587           const char  *subject;           const char   *subject;           (8-bit version)
3588           int          subject_length;           PCRE_SPTR16   subject;           (16-bit version)
3589           int          start_match;           int           subject_length;
3590           int          current_position;           int           start_match;
3591           int          capture_top;           int           current_position;
3592           int          capture_last;           int           capture_top;
3593           void        *callout_data;           int           capture_last;
3594           int          pattern_position;           void         *callout_data;
3595           int          next_item_length;           int           pattern_position;
3596             int           next_item_length;
3597         The version field is an integer containing the version  number  of  the           const unsigned char *mark;       (8-bit version)
3598         block  format. The initial version was 0; the current version is 1. The           const PCRE_UCHAR16  *mark;       (16-bit version)
3599         version number will change again in future  if  additional  fields  are  
3600           The  version  field  is an integer containing the version number of the
3601           block format. The initial version was 0; the current version is 2.  The
3602           version  number  will  change  again in future if additional fields are
3603         added, but the intention is never to remove any of the existing fields.         added, but the intention is never to remove any of the existing fields.
3604    
3605         The  callout_number  field  contains the number of the callout, as com-         The callout_number field contains the number of the  callout,  as  com-
3606         piled into the pattern (that is, the number after ?C for  manual  call-         piled  into  the pattern (that is, the number after ?C for manual call-
3607         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
3608    
3609         The  offset_vector field is a pointer to the vector of offsets that was         The offset_vector field is a pointer to the vector of offsets that  was
3610         passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When         passed  by  the  caller  to  the matching function. When pcre_exec() or
3611         pcre_exec()  is used, the contents can be inspected in order to extract         pcre16_exec() is used, the contents  can  be  inspected,  in  order  to
3612         substrings that have been matched so  far,  in  the  same  way  as  for         extract  substrings  that  have been matched so far, in the same way as
3613         extracting  substrings after a match has completed. For pcre_dfa_exec()         for extracting substrings after a match  has  completed.  For  the  DFA
3614         this field is not useful.         matching functions, this field is not useful.
3615    
3616         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
3617         were passed to pcre_exec().         were passed to the matching function.
3618    
3619         The  start_match  field normally contains the offset within the subject         The start_match field normally contains the offset within  the  subject
3620         at which the current match attempt  started.  However,  if  the  escape         at  which  the  current  match  attempt started. However, if the escape
3621         sequence  \K has been encountered, this value is changed to reflect the         sequence \K has been encountered, this value is changed to reflect  the
3622         modified starting point. If the pattern is not  anchored,  the  callout         modified  starting  point.  If the pattern is not anchored, the callout
3623         function may be called several times from the same point in the pattern         function may be called several times from the same point in the pattern
3624         for different starting points in the subject.         for different starting points in the subject.
3625    
3626         The current_position field contains the offset within  the  subject  of         The  current_position  field  contains the offset within the subject of
3627         the current match pointer.         the current match pointer.
3628    
3629         When  the  pcre_exec() function is used, the capture_top field contains         When the pcre_exec() or pcre16_exec() is used,  the  capture_top  field
3630         one more than the number of the highest numbered captured substring  so         contains one more than the number of the highest numbered captured sub-
3631         far.  If  no substrings have been captured, the value of capture_top is         string so far. If no substrings have been captured, the value  of  cap-
3632         one. This is always the case when pcre_dfa_exec() is used,  because  it         ture_top  is  one.  This  is always the case when the DFA functions are
3633         does not support captured substrings.         used, because they do not support captured substrings.
3634    
3635         The  capture_last  field  contains the number of the most recently cap-         The capture_last field contains the number of the  most  recently  cap-
3636         tured substring. If no substrings have been captured, its value is  -1.         tured  substring. If no substrings have been captured, its value is -1.
3637         This is always the case when pcre_dfa_exec() is used.         This is always the case for the DFA matching functions.
3638    
3639         The  callout_data  field contains a value that is passed to pcre_exec()         The callout_data field contains a value that is passed  to  a  matching
3640         or pcre_dfa_exec() specifically so that it can be passed back in  call-         function  specifically so that it can be passed back in callouts. It is
3641         outs.  It  is  passed  in the pcre_callout field of the pcre_extra data         passed in the callout_data field of a pcre_extra or  pcre16_extra  data
3642         structure. If no such data was passed, the value of callout_data  in  a         structure.  If  no such data was passed, the value of callout_data in a
3643         pcre_callout  block  is  NULL. There is a description of the pcre_extra         callout block is NULL. There is a description of the pcre_extra  struc-
3644         structure in the pcreapi documentation.         ture in the pcreapi documentation.
3645    
3646         The pattern_position field is present from version 1 of the  pcre_call-         The  pattern_position  field  is  present from version 1 of the callout
3647         out structure. It contains the offset to the next item to be matched in         structure. It contains the offset to the next item to be matched in the
3648         the pattern string.         pattern string.
3649    
3650         The next_item_length field is present from version 1 of the  pcre_call-         The  next_item_length  field  is  present from version 1 of the callout
3651         out structure. It contains the length of the next item to be matched in         structure. It contains the length of the next item to be matched in the
3652         the pattern string. When the callout immediately precedes  an  alterna-         pattern  string.  When  the callout immediately precedes an alternation
3653         tion  bar, a closing parenthesis, or the end of the pattern, the length         bar, a closing parenthesis, or the end of the pattern,  the  length  is
3654         is zero. When the callout precedes an opening parenthesis,  the  length         zero.  When  the callout precedes an opening parenthesis, the length is
3655         is that of the entire subpattern.         that of the entire subpattern.
3656    
3657         The  pattern_position  and next_item_length fields are intended to help         The pattern_position and next_item_length fields are intended  to  help
3658         in distinguishing between different automatic callouts, which all  have         in  distinguishing between different automatic callouts, which all have
3659         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
3660    
3661           The mark field is present from version 2 of the callout  structure.  In
3662           callouts from pcre_exec() or pcre16_exec() it contains a pointer to the
3663           zero-terminated name of the most recently passed (*MARK), (*PRUNE),  or
3664           (*THEN)  item  in the match, or NULL if no such items have been passed.
3665           Instances of (*PRUNE) or (*THEN) without a name  do  not  obliterate  a
3666           previous  (*MARK).  In  callouts  from  the DFA matching functions this
3667           field always contains NULL.
3668    
3669    
3670  RETURN VALUES  RETURN VALUES
3671    
3672         The  external callout function returns an integer to PCRE. If the value         The external callout function returns an integer to PCRE. If the  value
3673         is zero, matching proceeds as normal. If  the  value  is  greater  than         is  zero,  matching  proceeds  as  normal. If the value is greater than
3674         zero,  matching  fails  at  the current point, but the testing of other         zero, matching fails at the current point, but  the  testing  of  other
3675         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3676         failed.  If  the  value  is less than zero, the match is abandoned, and         failed. If the value is less than zero, the  match  is  abandoned,  the
3677         pcre_exec() or pcre_dfa_exec() returns the negative value.         matching function returns the negative value.
3678    
3679         Negative  values  should  normally  be   chosen   from   the   set   of         Negative   values   should   normally   be   chosen  from  the  set  of
3680         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
3681         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
3682         reserved  for  use  by callout functions; it will never be used by PCRE         reserved for use by callout functions; it will never be  used  by  PCRE
3683         itself.         itself.
3684    
3685    
# Line 2977  AUTHOR Line 3692  AUTHOR
3692    
3693  REVISION  REVISION
3694    
3695         Last updated: 29 September 2009         Last updated: 08 Janurary 2012
3696         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2012 University of Cambridge.
3697  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3698    
3699    
# Line 2993  DIFFERENCES BETWEEN PCRE AND PERL Line 3708  DIFFERENCES BETWEEN PCRE AND PERL
3708    
3709         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3710         handle regular expressions. The differences  described  here  are  with         handle regular expressions. The differences  described  here  are  with
3711         respect to Perl 5.10/5.11.         respect to Perl versions 5.10 and above.
3712    
3713         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details         1. PCRE has only a subset of Perl's Unicode support. Details of what it
3714         of what it does have are given in the section on UTF-8 support  in  the         does have are given in the pcreunicode page.
3715         main pcre page.  
3716           2. PCRE allows repeat quantifiers only on parenthesized assertions, but
3717         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         they  do  not mean what you might think. For example, (?!a){3} does not
3718         permits them, but they do not mean what you might think.  For  example,         assert that the next three characters are not "a". It just asserts that
3719         (?!a){3} does not assert that the next three characters are not "a". It         the next character is not "a" three times (in principle: PCRE optimizes
3720         just asserts that the next character is not "a" three times.         this to run the assertion just once). Perl allows repeat quantifiers on
3721           other assertions such as \b, but these do not seem to have any use.
3722         3. Capturing subpatterns that occur inside  negative  lookahead  asser-  
3723         tions  are  counted,  but their entries in the offsets vector are never         3.  Capturing  subpatterns  that occur inside negative lookahead asser-
3724         set. Perl sets its numerical variables from any such patterns that  are         tions are counted, but their entries in the offsets  vector  are  never
3725           set.  Perl sets its numerical variables from any such patterns that are
3726         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3727         ing), but only if the negative lookahead assertion  contains  just  one         ing),  but  only  if the negative lookahead assertion contains just one
3728         branch.         branch.
3729    
3730         4.  Though  binary zero characters are supported in the subject string,         4. Though binary zero characters are supported in the  subject  string,
3731         they are not allowed in a pattern string because it is passed as a nor-         they are not allowed in a pattern string because it is passed as a nor-
3732         mal C string, terminated by zero. The escape sequence \0 can be used in         mal C string, terminated by zero. The escape sequence \0 can be used in
3733         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3734    
3735         5. The following Perl escape sequences are not supported: \l,  \u,  \L,         5.  The  following Perl escape sequences are not supported: \l, \u, \L,
3736         \U, and \N. In fact these are implemented by Perl's general string-han-         \U, and \N when followed by a character name or Unicode value.  (\N  on
3737         dling and are not part of its pattern matching engine. If any of  these         its own, matching a non-newline character, is supported.) In fact these
3738         are encountered by PCRE, an error is generated.         are implemented by Perl's general string-handling and are not  part  of
3739           its  pattern  matching engine. If any of these are encountered by PCRE,
3740         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE         an error is generated by default. However, if the  PCRE_JAVASCRIPT_COM-
3741         is built with Unicode character property support. The  properties  that         PAT  option  is set, \U and \u are interpreted as JavaScript interprets
3742         can  be tested with \p and \P are limited to the general category prop-         them.
3743         erties such as Lu and Nd, script names such as Greek or  Han,  and  the  
3744         derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
3745         property, which Perl does not; the  Perl  documentation  says  "Because         is  built  with Unicode character property support. The properties that
3746           can be tested with \p and \P are limited to the general category  prop-
3747           erties  such  as  Lu and Nd, script names such as Greek or Han, and the
3748           derived properties Any and L&. PCRE does  support  the  Cs  (surrogate)
3749           property,  which  Perl  does  not; the Perl documentation says "Because
3750         Perl hides the need for the user to understand the internal representa-         Perl hides the need for the user to understand the internal representa-
3751         tion of Unicode characters, there is no need to implement the  somewhat         tion  of Unicode characters, there is no need to implement the somewhat
3752         messy concept of surrogates."         messy concept of surrogates."
3753    
3754         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE implements a simpler version of \X than Perl, which changed  to
3755           make  \X  match what Unicode calls an "extended grapheme cluster". This
3756           is more complicated than an extended Unicode sequence,  which  is  what
3757           PCRE matches.
3758    
3759           8. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3760         ters in between are treated as literals.  This  is  slightly  different         ters in between are treated as literals.  This  is  slightly  different
3761         from  Perl  in  that  $  and  @ are also handled as literals inside the         from  Perl  in  that  $  and  @ are also handled as literals inside the
3762         quotes. In Perl, they cause variable interpolation (but of course  PCRE         quotes. In Perl, they cause variable interpolation (but of course  PCRE
# Line 3047  DIFFERENCES BETWEEN PCRE AND PERL Line 3772  DIFFERENCES BETWEEN PCRE AND PERL
3772         The  \Q...\E  sequence  is recognized both inside and outside character         The  \Q...\E  sequence  is recognized both inside and outside character
3773         classes.         classes.
3774    
3775         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         9. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3776         constructions.  However,  there is support for recursive patterns. This         constructions.  However,  there is support for recursive patterns. This
3777         is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE         is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE
3778         "callout"  feature allows an external function to be called during pat-         "callout"  feature allows an external function to be called during pat-
3779         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3780