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revision 579 by ph10, Wed Nov 24 17:39:25 2010 UTC revision 678 by ph10, Sun Aug 28 15:23:03 2011 UTC
# Line 1  Line 1 
1  .TH PCREAPI 3  .TH PCREAPI 3
2  .SH NAME  .SH NAME
3  PCRE - Perl-compatible regular expressions  PCRE - Perl-compatible regular expressions
4  .SH "PCRE NATIVE API"  .SH "PCRE NATIVE API BASIC FUNCTIONS"
5  .rs  .rs
6  .sp  .sp
7  .B #include <pcre.h>  .B #include <pcre.h>
# Line 25  PCRE - Perl-compatible regular expressio Line 25  PCRE - Perl-compatible regular expressio
25  .ti +5n  .ti +5n
26  .B const char **\fIerrptr\fP);  .B const char **\fIerrptr\fP);
27  .PP  .PP
28    .B void pcre_free_study(pcre_extra *\fIextra\fP);
29    .PP
30  .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"  .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
31  .ti +5n  .ti +5n
32  .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,  .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
33  .ti +5n  .ti +5n
34  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
35    .
36    .
37    .SH "PCRE NATIVE API AUXILIARY FUNCTIONS"
38    .rs
39    .sp
40    .B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP);
41    .PP
42    .B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP);
43    .PP
44    .B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP,
45    .ti +5n
46    .B pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);
47  .PP  .PP
48  .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"  .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
49  .ti +5n  .ti +5n
# Line 114  PCRE - Perl-compatible regular expressio Line 128  PCRE - Perl-compatible regular expressio
128  .sp  .sp
129  PCRE has its own native API, which is described in this document. There are  PCRE has its own native API, which is described in this document. There are
130  also some wrapper functions that correspond to the POSIX regular expression  also some wrapper functions that correspond to the POSIX regular expression
131  API. These are described in the  API, but they do not give access to all the functionality. They are described
132    in the
133  .\" HREF  .\" HREF
134  \fBpcreposix\fP  \fBpcreposix\fP
135  .\"  .\"
136  documentation. Both of these APIs define a set of C function calls. A C++  documentation. Both of these APIs define a set of C function calls. A C++
137  wrapper is distributed with PCRE. It is documented in the  wrapper is also distributed with PCRE. It is documented in the
138  .\" HREF  .\" HREF
139  \fBpcrecpp\fP  \fBpcrecpp\fP
140  .\"  .\"
# Line 152  documentation, and the Line 167  documentation, and the
167  .\"  .\"
168  documentation describes how to compile and run it.  documentation describes how to compile and run it.
169  .P  .P
170    Just-in-time compiler support is an optional feature of PCRE that can be built
171    in appropriate hardware environments. It greatly speeds up the matching
172    performance of many patterns. Simple programs can request its use if available.
173    More complicated programs might need to make use of the
174    \fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and
175    \fBpcre_assign_jit_stack()\fP functions in order to control its memory usage.
176    These functions are discussed in the
177    .\" HREF
178    \fBpcrejit\fP
179    .\"
180    documentation.
181    .P
182  A second matching function, \fBpcre_dfa_exec()\fP, which is not  A second matching function, \fBpcre_dfa_exec()\fP, which is not
183  Perl-compatible, is also provided. This uses a different algorithm for the  Perl-compatible, is also provided. This uses a different algorithm for the
184  matching. The alternative algorithm finds all possible matches (at a given  matching. The alternative algorithm finds all possible matches (at a given
# Line 282  callout function pointed to by \fBpcre_c Line 309  callout function pointed to by \fBpcre_c
309  .P  .P
310  The compiled form of a regular expression is not altered during matching, so  The compiled form of a regular expression is not altered during matching, so
311  the same compiled pattern can safely be used by several threads at once.  the same compiled pattern can safely be used by several threads at once.
312    .P
313    If the just-in-time optimization feature is being used, it needs separate
314    memory stack areas for each thread. See the
315    .\" HREF
316    \fBpcrejit\fP
317    .\"
318    documentation for more details.
319  .  .
320  .  .
321  .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"  .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
# Line 324  otherwise it is set to zero. Line 358  otherwise it is set to zero.
358  The output is an integer that is set to one if support for Unicode character  The output is an integer that is set to one if support for Unicode character
359  properties is available; otherwise it is set to zero.  properties is available; otherwise it is set to zero.
360  .sp  .sp
361      PCRE_CONFIG_JIT
362    .sp
363    The output is an integer that is set to one if support for just-in-time
364    compiling is available; otherwise it is set to zero.
365    .sp
366    PCRE_CONFIG_NEWLINE    PCRE_CONFIG_NEWLINE
367  .sp  .sp
368  The output is an integer whose value specifies the default character sequence  The output is an integer whose value specifies the default character sequence
# Line 436  If \fIerrptr\fP is NULL, \fBpcre_compile Line 475  If \fIerrptr\fP is NULL, \fBpcre_compile
475  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
476  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
477  error message. This is a static string that is part of the library. You must  error message. This is a static string that is part of the library. You must
478  not try to free it. The offset from the start of the pattern to the byte that  not try to free it. Normally, the offset from the start of the pattern to the
479  was being processed when the error was discovered is placed in the variable  byte that was being processed when the error was discovered is placed in the
480  pointed to by \fIerroffset\fP, which must not be NULL. If it is, an immediate  variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, an
481  error is given. Some errors are not detected until checks are carried out when  immediate error is given). However, for an invalid UTF-8 string, the offset is
482  the whole pattern has been scanned; in this case the offset is set to the end  that of the first byte of the failing character. Also, some errors are not
483  of the pattern.  detected until checks are carried out when the whole pattern has been scanned;
484    in these cases the offset passed back is the length of the pattern.
485  .P  .P
486  Note that the offset is in bytes, not characters, even in UTF-8 mode. It may  Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
487  point into the middle of a UTF-8 character (for example, when  sometimes point into the middle of a UTF-8 character.
 PCRE_ERROR_BADUTF8 is returned for an invalid UTF-8 string).  
488  .P  .P
489  If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the  If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
490  \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is  \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
# Line 552  unescaped # outside a character class an Line 591  unescaped # outside a character class an
591  ignored. This is equivalent to Perl's /x option, and it can be changed within a  ignored. This is equivalent to Perl's /x option, and it can be changed within a
592  pattern by a (?x) option setting.  pattern by a (?x) option setting.
593  .P  .P
594  Which characters are interpreted as newlines  Which characters are interpreted as newlines is controlled by the options
595  is controlled by the options passed to \fBpcre_compile()\fP or by a special  passed to \fBpcre_compile()\fP or by a special sequence at the start of the
596  sequence at the start of the pattern, as described in the section entitled  pattern, as described in the section entitled
597  .\" HTML <a href="pcrepattern.html#newlines">  .\" HTML <a href="pcrepattern.html#newlines">
598  .\" </a>  .\" </a>
599  "Newline conventions"  "Newline conventions"
# Line 701  of UTF-8 characters instead of single-by Line 740  of UTF-8 characters instead of single-by
740  available only when PCRE is built to include UTF-8 support. If not, the use  available only when PCRE is built to include UTF-8 support. If not, the use
741  of this option provokes an error. Details of how this option changes the  of this option provokes an error. Details of how this option changes the
742  behaviour of PCRE are given in the  behaviour of PCRE are given in the
 .\" HTML <a href="pcre.html#utf8support">  
 .\" </a>  
 section on UTF-8 support  
 .\"  
 in the main  
743  .\" HREF  .\" HREF
744  \fBpcre\fP  \fBpcreunicode\fP
745  .\"  .\"
746  page.  page.
747  .sp  .sp
# Line 777  out of use. To avoid confusion, they hav Line 811  out of use. To avoid confusion, they hav
811    34  character value in \ex{...} sequence is too large    34  character value in \ex{...} sequence is too large
812    35  invalid condition (?(0)    35  invalid condition (?(0)
813    36  \eC not allowed in lookbehind assertion    36  \eC not allowed in lookbehind assertion
814    37  PCRE does not support \eL, \el, \eN, \eU, or \eu    37  PCRE does not support \eL, \el, \eN{name}, \eU, or \eu
815    38  number after (?C is > 255    38  number after (?C is > 255
816    39  closing ) for (?C expected    39  closing ) for (?C expected
817    40  recursive call could loop indefinitely    40  recursive call could loop indefinitely
# Line 811  out of use. To avoid confusion, they hav Line 845  out of use. To avoid confusion, they hav
845          not allowed          not allowed
846    66  (*MARK) must have an argument    66  (*MARK) must have an argument
847    67  this version of PCRE is not compiled with PCRE_UCP support    67  this version of PCRE is not compiled with PCRE_UCP support
848      68  \ec must be followed by an ASCII character
849      69  \ek is not followed by a braced, angle-bracketed, or quoted name
850  .sp  .sp
851  The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may  The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
852  be used if the limits were changed when PCRE was built.  be used if the limits were changed when PCRE was built.
853  .  .
854  .  .
855    .\" HTML <a name="studyingapattern"></a>
856  .SH "STUDYING A PATTERN"  .SH "STUDYING A PATTERN"
857  .rs  .rs
858  .sp  .sp
# Line 846  If studying the pattern does not produce Line 883  If studying the pattern does not produce
883  wants to pass any of the other fields to \fBpcre_exec()\fP or  wants to pass any of the other fields to \fBpcre_exec()\fP or
884  \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.  \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
885  .P  .P
886  The second argument of \fBpcre_study()\fP contains option bits. At present, no  The second argument of \fBpcre_study()\fP contains option bits. There is only
887  options are defined, and this argument should always be zero.  one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-time
888    compiler is available, the pattern is further compiled into machine code that
889    executes much faster than the \fBpcre_exec()\fP matching function. If
890    the just-in-time compiler is not available, this option is ignored. All other
891    bits in the \fIoptions\fP argument must be zero.
892    .P
893    JIT compilation is a heavyweight optimization. It can take some time for
894    patterns to be analyzed, and for one-off matches and simple patterns the
895    benefit of faster execution might be offset by a much slower study time.
896    Not all patterns can be optimized by the JIT compiler. For those that cannot be
897    handled, matching automatically falls back to the \fBpcre_exec()\fP
898    interpreter. For more details, see the
899    .\" HREF
900    \fBpcrejit\fP
901    .\"
902    documentation.
903  .P  .P
904  The third argument for \fBpcre_study()\fP is a pointer for an error message. If  The third argument for \fBpcre_study()\fP is a pointer for an error message. If
905  studying succeeds (even if no data is returned), the variable it points to is  studying succeeds (even if no data is returned), the variable it points to is
# Line 856  static string that is part of the librar Line 908  static string that is part of the librar
908  should test the error pointer for NULL after calling \fBpcre_study()\fP, to be  should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
909  sure that it has run successfully.  sure that it has run successfully.
910  .P  .P
911  This is a typical call to \fBpcre_study\fP():  When you are finished with a pattern, you can free the memory used for the
912    study data by calling \fBpcre_free_study()\fP. This function was added to the
913    API for release 8.20. For earlier versions, the memory could be freed with
914    \fBpcre_free()\fP, just like the pattern itself. This will still work in cases
915    where PCRE_STUDY_JIT_COMPILE is not used, but it is advisable to change to the
916    new function when convenient.
917    .P
918    This is a typical way in which \fBpcre_study\fP() is used (except that in a
919    real application there should be tests for errors):
920  .sp  .sp
921    pcre_extra *pe;    int rc;
922    pe = pcre_study(    pcre *re;
923      pcre_extra *sd;
924      re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
925      sd = pcre_study(
926      re,             /* result of pcre_compile() */      re,             /* result of pcre_compile() */
927      0,              /* no options exist */      0,              /* no options */
928      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
929      rc = pcre_exec(   /* see below for details of pcre_exec() options */
930        re, sd, "subject", 7, 0, 0, ovector, 30);
931      ...
932      pcre_free_study(sd);
933      pcre_free(re);
934  .sp  .sp
935  Studying a pattern does two things: first, a lower bound for the length of  Studying a pattern does two things: first, a lower bound for the length of
936  subject string that is needed to match the pattern is computed. This does not  subject string that is needed to match the pattern is computed. This does not
# Line 877  single fixed starting character. A bitma Line 945  single fixed starting character. A bitma
945  created. This speeds up finding a position in the subject at which to start  created. This speeds up finding a position in the subject at which to start
946  matching.  matching.
947  .P  .P
948  The two optimizations just described can be disabled by setting the  These two optimizations apply to both \fBpcre_exec()\fP and
949  PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or  \fBpcre_dfa_exec()\fP. However, they are not used by \fBpcre_exec()\fP if
950    \fBpcre_study()\fP is called with the PCRE_STUDY_JIT_COMPILE option, and
951    just-in-time compiling is successful. The optimizations can be disabled by
952    setting the PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
953  \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains  \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
954  callouts or (*MARK), and you want to make use of these facilities in cases  callouts or (*MARK) (which cannot be handled by the JIT compiler), and you want
955  where matching fails. See the discussion of PCRE_NO_START_OPTIMIZE  to make use of these facilities in cases where matching fails. See the
956    discussion of PCRE_NO_START_OPTIMIZE
957  .\" HTML <a href="#execoptions">  .\" HTML <a href="#execoptions">
958  .\" </a>  .\" </a>
959  below.  below.
# Line 946  one in which it was compiled. Passing ta Line 1018  one in which it was compiled. Passing ta
1018  below in the section on matching a pattern.  below in the section on matching a pattern.
1019  .  .
1020  .  .
1021    .\" HTML <a name="infoaboutpattern"></a>
1022  .SH "INFORMATION ABOUT A PATTERN"  .SH "INFORMATION ABOUT A PATTERN"
1023  .rs  .rs
1024  .sp  .sp
# Line 977  check against passing an arbitrary memor Line 1050  check against passing an arbitrary memor
1050    size_t length;    size_t length;
1051    rc = pcre_fullinfo(    rc = pcre_fullinfo(
1052      re,               /* result of pcre_compile() */      re,               /* result of pcre_compile() */
1053      pe,               /* result of pcre_study(), or NULL */      sd,               /* result of pcre_study(), or NULL */
1054      PCRE_INFO_SIZE,   /* what is required */      PCRE_INFO_SIZE,   /* what is required */
1055      &length);         /* where to put the data */      &length);         /* where to put the data */
1056  .sp  .sp
# Line 1042  Return 1 if the (?J) or (?-J) option set Line 1115  Return 1 if the (?J) or (?-J) option set
1115  0. The fourth argument should point to an \fBint\fP variable. (?J) and  0. The fourth argument should point to an \fBint\fP variable. (?J) and
1116  (?-J) set and unset the local PCRE_DUPNAMES option, respectively.  (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1117  .sp  .sp
1118      PCRE_INFO_JIT
1119    .sp
1120    Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE option, and
1121    just-in-time compiling was successful. The fourth argument should point to an
1122    \fBint\fP variable. A return value of 0 means that JIT support is not available
1123    in this version of PCRE, or that the pattern was not studied with the
1124    PCRE_STUDY_JIT_COMPILE option, or that the JIT compiler could not handle this
1125    particular pattern. See the
1126    .\" HREF
1127    \fBpcrejit\fP
1128    .\"
1129    documentation for details of what can and cannot be handled.
1130    .sp
1131    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
1132  .sp  .sp
1133  Return the value of the rightmost literal byte that must exist in any matched  Return the value of the rightmost literal byte that must exist in any matched
# Line 1164  variable. Line 1250  variable.
1250  .sp  .sp
1251    PCRE_INFO_STUDYSIZE    PCRE_INFO_STUDYSIZE
1252  .sp  .sp
1253  Return the size of the data block pointed to by the \fIstudy_data\fP field in  Return the size of the data block pointed to by the \fIstudy_data\fP field in a
1254  a \fBpcre_extra\fP block. That is, it is the value that was passed to  \fBpcre_extra\fP block. If \fBpcre_extra\fP is NULL, or there is no study data,
1255  \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data  zero is returned. The fourth argument should point to a \fBsize_t\fP variable.
1256  created by \fBpcre_study()\fP. If \fBpcre_extra\fP is NULL, or there is no  The \fIstudy_data\fP field is set by \fBpcre_study()\fP to record information
1257  study data, zero is returned. The fourth argument should point to a  that will speed up matching (see the section entitled
1258  \fBsize_t\fP variable.  .\" HTML <a href="#studyingapattern">
1259    .\" </a>
1260    "Studying a pattern"
1261    .\"
1262    above). The format of the \fIstudy_data\fP block is private, but its length
1263    is made available via this option so that it can be saved and restored (see the
1264    .\" HREF
1265    \fBpcreprecompile\fP
1266    .\"
1267    documentation for details).
1268  .  .
1269  .  .
1270  .SH "OBSOLETE INFO FUNCTION"  .SH "OBSOLETE INFO FUNCTION"
# Line 1264  Here is an example of a simple call to \ Line 1359  Here is an example of a simple call to \
1359      ovector,        /* vector of integers for substring information */      ovector,        /* vector of integers for substring information */
1360      30);            /* number of elements (NOT size in bytes) */      30);            /* number of elements (NOT size in bytes) */
1361  .  .
1362    .
1363  .\" HTML <a name="extradata"></a>  .\" HTML <a name="extradata"></a>
1364  .SS "Extra data for \fBpcre_exec()\fR"  .SS "Extra data for \fBpcre_exec()\fR"
1365  .rs  .rs
# Line 1276  fields (not necessarily in this order): Line 1372  fields (not necessarily in this order):
1372  .sp  .sp
1373    unsigned long int \fIflags\fP;    unsigned long int \fIflags\fP;
1374    void *\fIstudy_data\fP;    void *\fIstudy_data\fP;
1375      void *\fIexecutable_jit\fP;
1376    unsigned long int \fImatch_limit\fP;    unsigned long int \fImatch_limit\fP;
1377    unsigned long int \fImatch_limit_recursion\fP;    unsigned long int \fImatch_limit_recursion\fP;
1378    void *\fIcallout_data\fP;    void *\fIcallout_data\fP;
# Line 1286  The \fIflags\fP field is a bitmap that s Line 1383  The \fIflags\fP field is a bitmap that s
1383  are set. The flag bits are:  are set. The flag bits are:
1384  .sp  .sp
1385    PCRE_EXTRA_STUDY_DATA    PCRE_EXTRA_STUDY_DATA
1386      PCRE_EXTRA_EXECUTABLE_JIT
1387    PCRE_EXTRA_MATCH_LIMIT    PCRE_EXTRA_MATCH_LIMIT
1388    PCRE_EXTRA_MATCH_LIMIT_RECURSION    PCRE_EXTRA_MATCH_LIMIT_RECURSION
1389    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1390    PCRE_EXTRA_TABLES    PCRE_EXTRA_TABLES
1391    PCRE_EXTRA_MARK    PCRE_EXTRA_MARK
1392  .sp  .sp
1393  Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the  Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes
1394  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with  the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is
1395  the appropriate flag bit. You should not set this yourself, but you may add to  returned by \fBpcre_study()\fP, together with the appropriate flag bits. You
1396  the block by setting the other fields and their corresponding flag bits.  should not set these yourself, but you may add to the block by setting the
1397    other fields and their corresponding flag bits.
1398  .P  .P
1399  The \fImatch_limit\fP field provides a means of preventing PCRE from using up a  The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1400  vast amount of resources when running patterns that are not going to match,  vast amount of resources when running patterns that are not going to match,
1401  but which have a very large number of possibilities in their search trees. The  but which have a very large number of possibilities in their search trees. The
1402  classic example is a pattern that uses nested unlimited repeats.  classic example is a pattern that uses nested unlimited repeats.
1403  .P  .P
1404  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly  Internally, \fBpcre_exec()\fP uses a function called \fBmatch()\fP, which it
1405  (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the  calls repeatedly (sometimes recursively). The limit set by \fImatch_limit\fP is
1406  number of times this function is called during a match, which has the effect of  imposed on the number of times this function is called during a match, which
1407  limiting the amount of backtracking that can take place. For patterns that are  has the effect of limiting the amount of backtracking that can take place. For
1408  not anchored, the count restarts from zero for each position in the subject  patterns that are not anchored, the count restarts from zero for each position
1409  string.  in the subject string.
1410    .P
1411    When \fBpcre_exec()\fP is called with a pattern that was successfully studied
1412    with the PCRE_STUDY_JIT_COMPILE option, the way that the matching is executed
1413    is entirely different. However, there is still the possibility of runaway
1414    matching that goes on for a very long time, and so the \fImatch_limit\fP value
1415    is also used in this case (but in a different way) to limit how long the
1416    matching can continue.
1417  .P  .P
1418  The default value for the limit can be set when PCRE is built; the default  The default value for the limit can be set when PCRE is built; the default
1419  default is 10 million, which handles all but the most extreme cases. You can  default is 10 million, which handles all but the most extreme cases. You can
# Line 1320  The \fImatch_limit_recursion\fP field is Line 1426  The \fImatch_limit_recursion\fP field is
1426  instead of limiting the total number of times that \fBmatch()\fP is called, it  instead of limiting the total number of times that \fBmatch()\fP is called, it
1427  limits the depth of recursion. The recursion depth is a smaller number than the  limits the depth of recursion. The recursion depth is a smaller number than the
1428  total number of calls, because not all calls to \fBmatch()\fP are recursive.  total number of calls, because not all calls to \fBmatch()\fP are recursive.
1429  This limit is of use only if it is set smaller than \fImatch_limit\fP.  This limit is of use only if it is set smaller than \fImatch_limit\fP.
1430  .P  .P
1431  Limiting the recursion depth limits the amount of stack that can be used, or,  Limiting the recursion depth limits the amount of machine stack that can be
1432  when PCRE has been compiled to use memory on the heap instead of the stack, the  used, or, when PCRE has been compiled to use memory on the heap instead of the
1433  amount of heap memory that can be used.  stack, the amount of heap memory that can be used. This limit is relevant, and
1434    is ignored, when the pattern was successfully studied with
1435    PCRE_STUDY_JIT_COMPILE.
1436  .P  .P
1437  The default value for \fImatch_limit_recursion\fP can be set when PCRE is  The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1438  built; the default default is the same value as the default for  built; the default default is the same value as the default for
# Line 1547  in the main Line 1655  in the main
1655  .\"  .\"
1656  page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns  page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1657  the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is  the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
1658  a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. If  a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
1659  \fIstartoffset\fP contains a value that does not point to the start of a UTF-8  both cases, information about the precise nature of the error may also be
1660  character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is  returned (see the descriptions of these errors in the section entitled \fIError
1661    return values from\fP \fBpcre_exec()\fP
1662    .\" HTML <a href="#errorlist">
1663    .\" </a>
1664    below).
1665    .\"
1666    If \fIstartoffset\fP contains a value that does not point to the start of a
1667    UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1668  returned.  returned.
1669  .P  .P
1670  If you already know that your subject is valid, and you want to skip these  If you already know that your subject is valid, and you want to skip these
# Line 1717  whatever values they previously had. Line 1832  whatever values they previously had.
1832  Some convenience functions are provided for extracting the captured substrings  Some convenience functions are provided for extracting the captured substrings
1833  as separate strings. These are described below.  as separate strings. These are described below.
1834  .  .
1835    .
1836  .\" HTML <a name="errorlist"></a>  .\" HTML <a name="errorlist"></a>
1837  .SS "Error return values from \fBpcre_exec()\fP"  .SS "Error return values from \fBpcre_exec()\fP"
1838  .rs  .rs
# Line 1786  documentation for details. Line 1902  documentation for details.
1902  .sp  .sp
1903    PCRE_ERROR_BADUTF8        (-10)    PCRE_ERROR_BADUTF8        (-10)
1904  .sp  .sp
1905  A string that contains an invalid UTF-8 byte sequence was passed as a subject.  A string that contains an invalid UTF-8 byte sequence was passed as a subject,
1906  However, if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8  and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
1907  character at the end of the subject, PCRE_ERROR_SHORTUTF8 is used instead.  (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
1908    UTF-8 character is placed in the first element, and a reason code is placed in
1909    the second element. The reason codes are listed in the
1910    .\" HTML <a href="#badutf8reasons">
1911    .\" </a>
1912    following section.
1913    .\"
1914    For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
1915    truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
1916    PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
1917  .sp  .sp
1918    PCRE_ERROR_BADUTF8_OFFSET (-11)    PCRE_ERROR_BADUTF8_OFFSET (-11)
1919  .sp  .sp
1920  The UTF-8 byte sequence that was passed as a subject was valid, but the value  The UTF-8 byte sequence that was passed as a subject was checked and found to
1921  of \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the  be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
1922    \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
1923  end of the subject.  end of the subject.
1924  .sp  .sp
1925    PCRE_ERROR_PARTIAL        (-12)    PCRE_ERROR_PARTIAL        (-12)
# Line 1837  subject, that is, the value in \fIlength Line 1963  subject, that is, the value in \fIlength
1963  .sp  .sp
1964    PCRE_ERROR_SHORTUTF8      (-25)    PCRE_ERROR_SHORTUTF8      (-25)
1965  .sp  .sp
1966  The subject string ended with an incomplete (truncated) UTF-8 character, and  This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
1967  the PCRE_PARTIAL_HARD option was set. Without this option, PCRE_ERROR_BADUTF8  ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
1968  is returned in this situation.  Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
1969    fact sufficient to detect this case, but this special error code for
1970    PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
1971    retained for backwards compatibility.
1972    .sp
1973      PCRE_ERROR_RECURSELOOP    (-26)
1974    .sp
1975    This error is returned when \fBpcre_exec()\fP detects a recursion loop within
1976    the pattern. Specifically, it means that either the whole pattern or a
1977    subpattern has been called recursively for the second time at the same position
1978    in the subject string. Some simple patterns that might do this are detected and
1979    faulted at compile time, but more complicated cases, in particular mutual
1980    recursions between two different subpatterns, cannot be detected until run
1981    time.
1982    .sp
1983      PCRE_ERROR_JIT_STACKLIMIT (-27)
1984    .sp
1985    This error is returned when a pattern that was successfully studied using the
1986    PCRE_STUDY_JIT_COMPILE option is matched, but the memory available for the
1987    just-in-time processing stack is not large enough. See the
1988    .\" HREF
1989    \fBpcrejit\fP
1990    .\"
1991    documentation for more details.
1992  .P  .P
1993  Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.  Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1994  .  .
1995  .  .
1996    .\" HTML <a name="badutf8reasons"></a>
1997    .SS "Reason codes for invalid UTF-8 strings"
1998    .rs
1999    .sp
2000    When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
2001    PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
2002    least 2, the offset of the start of the invalid UTF-8 character is placed in
2003    the first output vector element (\fIovector[0]\fP) and a reason code is placed
2004    in the second element (\fIovector[1]\fP). The reason codes are given names in
2005    the \fBpcre.h\fP header file:
2006    .sp
2007      PCRE_UTF8_ERR1
2008      PCRE_UTF8_ERR2
2009      PCRE_UTF8_ERR3
2010      PCRE_UTF8_ERR4
2011      PCRE_UTF8_ERR5
2012    .sp
2013    The string ends with a truncated UTF-8 character; the code specifies how many
2014    bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2015    no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2016    allows for up to 6 bytes, and this is checked first; hence the possibility of
2017    4 or 5 missing bytes.
2018    .sp
2019      PCRE_UTF8_ERR6
2020      PCRE_UTF8_ERR7
2021      PCRE_UTF8_ERR8
2022      PCRE_UTF8_ERR9
2023      PCRE_UTF8_ERR10
2024    .sp
2025    The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2026    character do not have the binary value 0b10 (that is, either the most
2027    significant bit is 0, or the next bit is 1).
2028    .sp
2029      PCRE_UTF8_ERR11
2030      PCRE_UTF8_ERR12
2031    .sp
2032    A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2033    these code points are excluded by RFC 3629.
2034    .sp
2035      PCRE_UTF8_ERR13
2036    .sp
2037    A 4-byte character has a value greater than 0x10fff; these code points are
2038    excluded by RFC 3629.
2039    .sp
2040      PCRE_UTF8_ERR14
2041    .sp
2042    A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2043    code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2044    from UTF-8.
2045    .sp
2046      PCRE_UTF8_ERR15
2047      PCRE_UTF8_ERR16
2048      PCRE_UTF8_ERR17
2049      PCRE_UTF8_ERR18
2050      PCRE_UTF8_ERR19
2051    .sp
2052    A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2053    value that can be represented by fewer bytes, which is invalid. For example,
2054    the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2055    one byte.
2056    .sp
2057      PCRE_UTF8_ERR20
2058    .sp
2059    The two most significant bits of the first byte of a character have the binary
2060    value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2061    byte can only validly occur as the second or subsequent byte of a multi-byte
2062    character.
2063    .sp
2064      PCRE_UTF8_ERR21
2065    .sp
2066    The first byte of a character has the value 0xfe or 0xff. These values can
2067    never occur in a valid UTF-8 string.
2068    .
2069    .
2070  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
2071  .rs  .rs
2072  .sp  .sp
# Line 2039  fourth are pointers to variables which a Line 2262  fourth are pointers to variables which a
2262  has run, they point to the first and last entries in the name-to-number table  has run, they point to the first and last entries in the name-to-number table
2263  for the given name. The function itself returns the length of each entry, or  for the given name. The function itself returns the length of each entry, or
2264  PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is  PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2265  described above in the section entitled \fIInformation about a pattern\fP.  described above in the section entitled \fIInformation about a pattern\fP
2266    .\" HTML <a href="#infoaboutpattern">
2267    .\" </a>
2268    above.
2269    .\"
2270  Given all the relevant entries for the name, you can extract each of their  Given all the relevant entries for the name, you can extract each of their
2271  numbers, and hence the captured data, if any.  numbers, and hence the captured data, if any.
2272  .  .
# Line 2169  match. There is more discussion of this Line 2396  match. There is more discussion of this
2396  .\"  .\"
2397  documentation.  documentation.
2398  .  .
2399    .
2400  .SS "Successful returns from \fBpcre_dfa_exec()\fP"  .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2401  .rs  .rs
2402  .sp  .sp
# Line 2202  matching string is given first. If there Line 2430  matching string is given first. If there
2430  \fIovector\fP, the yield of the function is zero, and the vector is filled with  \fIovector\fP, the yield of the function is zero, and the vector is filled with
2431  the longest matches.  the longest matches.
2432  .  .
2433    .
2434  .SS "Error returns from \fBpcre_dfa_exec()\fP"  .SS "Error returns from \fBpcre_dfa_exec()\fP"
2435  .rs  .rs
2436  .sp  .sp
# Line 2229  group. These are not supported. Line 2458  group. These are not supported.
2458    PCRE_ERROR_DFA_UMLIMIT    (-18)    PCRE_ERROR_DFA_UMLIMIT    (-18)
2459  .sp  .sp
2460  This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP  This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2461  block that contains a setting of the \fImatch_limit\fP field. This is not  block that contains a setting of the \fImatch_limit\fP or
2462  supported (it is meaningless).  \fImatch_limit_recursion\fP fields. This is not supported (these fields are
2463    meaningless for DFA matching).
2464  .sp  .sp
2465    PCRE_ERROR_DFA_WSSIZE     (-19)    PCRE_ERROR_DFA_WSSIZE     (-19)
2466  .sp  .sp
# Line 2267  Cambridge CB2 3QH, England. Line 2497  Cambridge CB2 3QH, England.
2497  .rs  .rs
2498  .sp  .sp
2499  .nf  .nf
2500  Last updated: 21 November 2010  Last updated: 27 August 2011
2501  Copyright (c) 1997-2010 University of Cambridge.  Copyright (c) 1997-2011 University of Cambridge.
2502  .fi  .fi

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