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revision 440 by ph10, Wed Sep 9 10:14:40 2009 UTC revision 546 by ph10, Sun Jun 20 15:44:12 2010 UTC
# Line 132  an application that uses PCRE. The heade Line 132  an application that uses PCRE. The heade
132  and PCRE_MINOR to contain the major and minor release numbers for the library.  and PCRE_MINOR to contain the major and minor release numbers for the library.
133  Applications can use these to include support for different releases of PCRE.  Applications can use these to include support for different releases of PCRE.
134  .P  .P
135    In a Windows environment, if you want to statically link an application program
136    against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
137    including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
138    \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
139    \fB__declspec(dllimport)\fP, with unwanted results.
140    .P
141  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
142  and \fBpcre_exec()\fP are used for compiling and matching regular expressions  and \fBpcre_exec()\fP are used for compiling and matching regular expressions
143  in a Perl-compatible manner. A sample program that demonstrates the simplest  in a Perl-compatible manner. A sample program that demonstrates the simplest
# Line 395  avoiding the use of the stack. Line 401  avoiding the use of the stack.
401  Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be  Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
402  called to compile a pattern into an internal form. The only difference between  called to compile a pattern into an internal form. The only difference between
403  the two interfaces is that \fBpcre_compile2()\fP has an additional argument,  the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
404  \fIerrorcodeptr\fP, via which a numerical error code can be returned.  \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
405    too much repetition, we refer just to \fBpcre_compile()\fP below, but the
406    information applies equally to \fBpcre_compile2()\fP.
407  .P  .P
408  The pattern is a C string terminated by a binary zero, and is passed in the  The pattern is a C string terminated by a binary zero, and is passed in the
409  \fIpattern\fP argument. A pointer to a single block of memory that is obtained  \fIpattern\fP argument. A pointer to a single block of memory that is obtained
# Line 412  argument, which is an address (see below Line 420  argument, which is an address (see below
420  The \fIoptions\fP argument contains various bit settings that affect the  The \fIoptions\fP argument contains various bit settings that affect the
421  compilation. It should be zero if no options are required. The available  compilation. It should be zero if no options are required. The available
422  options are described below. Some of them (in particular, those that are  options are described below. Some of them (in particular, those that are
423  compatible with Perl, but also some others) can also be set and unset from  compatible with Perl, but some others as well) can also be set and unset from
424  within the pattern (see the detailed description in the  within the pattern (see the detailed description in the
425  .\" HREF  .\" HREF
426  \fBpcrepattern\fP  \fBpcrepattern\fP
427  .\"  .\"
428  documentation). For those options that can be different in different parts of  documentation). For those options that can be different in different parts of
429  the pattern, the contents of the \fIoptions\fP argument specifies their initial  the pattern, the contents of the \fIoptions\fP argument specifies their
430  settings at the start of compilation and execution. The PCRE_ANCHORED and  settings at the start of compilation and execution. The PCRE_ANCHORED,
431  PCRE_NEWLINE_\fIxxx\fP options can be set at the time of matching as well as at  PCRE_BSR_\fIxxx\fP, and PCRE_NEWLINE_\fIxxx\fP options can be set at the time
432  compile time.  of matching as well as at compile time.
433  .P  .P
434  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
435  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
436  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
437  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
438  not try to free it. The offset from the start of the pattern to the character  not try to free it. The byte offset from the start of the pattern to the
439  where the error was discovered is placed in the variable pointed to by  character that was being processed when the error was discovered is placed in
440  \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.  the variable pointed to by \fIerroffset\fP, which must not be NULL. If it is,
441    an immediate error is given. Some errors are not detected until checks are
442    carried out when the whole pattern has been scanned; in this case the offset is
443    set to the end of the pattern.
444  .P  .P
445  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
446  \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 548  set, any backslash in a pattern that is Line 559  set, any backslash in a pattern that is
559  special meaning causes an error, thus reserving these combinations for future  special meaning causes an error, thus reserving these combinations for future
560  expansion. By default, as in Perl, a backslash followed by a letter with no  expansion. By default, as in Perl, a backslash followed by a letter with no
561  special meaning is treated as a literal. (Perl can, however, be persuaded to  special meaning is treated as a literal. (Perl can, however, be persuaded to
562  give a warning for this.) There are at present no other features controlled by  give an error for this, by running it with the -w option.) There are at present
563  this option. It can also be set by a (?X) option setting within a pattern.  no other features controlled by this option. It can also be set by a (?X)
564    option setting within a pattern.
565  .sp  .sp
566    PCRE_FIRSTLINE    PCRE_FIRSTLINE
567  .sp  .sp
# Line 630  were followed by ?: but named parenthese Line 642  were followed by ?: but named parenthese
642  they acquire numbers in the usual way). There is no equivalent of this option  they acquire numbers in the usual way). There is no equivalent of this option
643  in Perl.  in Perl.
644  .sp  .sp
645      PCRE_UCP
646    .sp
647    This option changes the way PCRE processes \eb, \ed, \es, \ew, and some of the
648    POSIX character classes. By default, only ASCII characters are recognized, but
649    if PCRE_UCP is set, Unicode properties are used instead to classify characters.
650    More details are given in the section on
651    .\" HTML <a href="pcre.html#genericchartypes">
652    .\" </a>
653    generic character types
654    .\"
655    in the
656    .\" HREF
657    \fBpcrepattern\fP
658    .\"
659    page. If you set PCRE_UCP, matching one of the items it affects takes much
660    longer. The option is available only if PCRE has been compiled with Unicode
661    property support.
662    .sp
663    PCRE_UNGREEDY    PCRE_UNGREEDY
664  .sp  .sp
665  This option inverts the "greediness" of the quantifiers so that they are not  This option inverts the "greediness" of the quantifiers so that they are not
# Line 735  out of use. To avoid confusion, they hav Line 765  out of use. To avoid confusion, they hav
765    50  [this code is not in use]    50  [this code is not in use]
766    51  octal value is greater than \e377 (not in UTF-8 mode)    51  octal value is greater than \e377 (not in UTF-8 mode)
767    52  internal error: overran compiling workspace    52  internal error: overran compiling workspace
768    53  internal error: previously-checked referenced subpattern not found    53  internal error: previously-checked referenced subpattern
769            not found
770    54  DEFINE group contains more than one branch    54  DEFINE group contains more than one branch
771    55  repeating a DEFINE group is not allowed    55  repeating a DEFINE group is not allowed
772    56  inconsistent NEWLINE options    56  inconsistent NEWLINE options
773    57  \eg is not followed by a braced, angle-bracketed, or quoted    57  \eg is not followed by a braced, angle-bracketed, or quoted
774          name/number or by a plain number          name/number or by a plain number
775    58  a numbered reference must not be zero    58  a numbered reference must not be zero
776    59  (*VERB) with an argument is not supported    59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
777    60  (*VERB) not recognized    60  (*VERB) not recognized
778    61  number is too big    61  number is too big
779    62  subpattern name expected    62  subpattern name expected
780    63  digit expected after (?+    63  digit expected after (?+
781    64  ] is an invalid data character in JavaScript compatibility mode    64  ] is an invalid data character in JavaScript compatibility mode
782      65  different names for subpatterns of the same number are
783            not allowed
784      66  (*MARK) must have an argument
785      67  this version of PCRE is not compiled with PCRE_UCP support
786  .sp  .sp
787  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
788  be used if the limits were changed when PCRE was built.  be used if the limits were changed when PCRE was built.
# Line 769  help speed up matching, \fBpcre_study()\ Line 804  help speed up matching, \fBpcre_study()\
804  results of the study.  results of the study.
805  .P  .P
806  The returned value from \fBpcre_study()\fP can be passed directly to  The returned value from \fBpcre_study()\fP can be passed directly to
807  \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other  \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
808  fields that can be set by the caller before the block is passed; these are  also contains other fields that can be set by the caller before the block is
809  described  passed; these are described
810  .\" HTML <a href="#extradata">  .\" HTML <a href="#extradata">
811  .\" </a>  .\" </a>
812  below  below
813  .\"  .\"
814  in the section on matching a pattern.  in the section on matching a pattern.
815  .P  .P
816  If studying the pattern does not produce any additional information  If studying the pattern does not produce any useful information,
817  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
818  wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its  wants to pass any of the other fields to \fBpcre_exec()\fP or
819  own \fBpcre_extra\fP block.  \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
820  .P  .P
821  The second argument of \fBpcre_study()\fP contains option bits. At present, no  The second argument of \fBpcre_study()\fP contains option bits. At present, no
822  options are defined, and this argument should always be zero.  options are defined, and this argument should always be zero.
# Line 801  This is a typical call to \fBpcre_study\ Line 836  This is a typical call to \fBpcre_study\
836      0,              /* no options exist */      0,              /* no options exist */
837      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
838  .sp  .sp
839  At present, studying a pattern is useful only for non-anchored patterns that do  Studying a pattern does two things: first, a lower bound for the length of
840  not have a single fixed starting character. A bitmap of possible starting  subject string that is needed to match the pattern is computed. This does not
841  bytes is created.  mean that there are any strings of that length that match, but it does
842    guarantee that no shorter strings match. The value is used by
843    \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
844    match strings that are shorter than the lower bound. You can find out the value
845    in a calling program via the \fBpcre_fullinfo()\fP function.
846    .P
847    Studying a pattern is also useful for non-anchored patterns that do not have a
848    single fixed starting character. A bitmap of possible starting bytes is
849    created. This speeds up finding a position in the subject at which to start
850    matching.
851  .  .
852  .  .
853  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
# Line 813  bytes is created. Line 857  bytes is created.
857  PCRE handles caseless matching, and determines whether characters are letters,  PCRE handles caseless matching, and determines whether characters are letters,
858  digits, or whatever, by reference to a set of tables, indexed by character  digits, or whatever, by reference to a set of tables, indexed by character
859  value. When running in UTF-8 mode, this applies only to characters with codes  value. When running in UTF-8 mode, this applies only to characters with codes
860  less than 128. Higher-valued codes never match escapes such as \ew or \ed, but  less than 128. By default, higher-valued codes never match escapes such as \ew
861  can be tested with \ep if PCRE is built with Unicode character property  or \ed, but they can be tested with \ep if PCRE is built with Unicode character
862  support. The use of locales with Unicode is discouraged. If you are handling  property support. Alternatively, the PCRE_UCP option can be set at compile
863  characters with codes greater than 128, you should either use UTF-8 and  time; this causes \ew and friends to use Unicode property support instead of
864  Unicode, or use locales, but not try to mix the two.  built-in tables. The use of locales with Unicode is discouraged. If you are
865    handling characters with codes greater than 128, you should either use UTF-8
866    and Unicode, or use locales, but not try to mix the two.
867  .P  .P
868  PCRE contains an internal set of tables that are used when the final argument  PCRE contains an internal set of tables that are used when the final argument
869  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
# Line 968  follows something of variable length. Fo Line 1014  follows something of variable length. Fo
1014  /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value  /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1015  is -1.  is -1.
1016  .sp  .sp
1017      PCRE_INFO_MINLENGTH
1018    .sp
1019    If the pattern was studied and a minimum length for matching subject strings
1020    was computed, its value is returned. Otherwise the returned value is -1. The
1021    value is a number of characters, not bytes (this may be relevant in UTF-8
1022    mode). The fourth argument should point to an \fBint\fP variable. A
1023    non-negative value is a lower bound to the length of any matching string. There
1024    may not be any strings of that length that do actually match, but every string
1025    that does match is at least that long.
1026    .sp
1027    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
1028    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
1029    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
# Line 988  entry; both of these return an \fBint\fP Line 1044  entry; both of these return an \fBint\fP
1044  length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first  length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1045  entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry  entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
1046  are the number of the capturing parenthesis, most significant byte first. The  are the number of the capturing parenthesis, most significant byte first. The
1047  rest of the entry is the corresponding name, zero terminated. The names are in  rest of the entry is the corresponding name, zero terminated.
1048  alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of  .P
1049  their parentheses numbers. For example, consider the following pattern (assume  The names are in alphabetical order. Duplicate names may appear if (?| is used
1050  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  to create multiple groups with the same number, as described in the
1051    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1052    .\" </a>
1053    section on duplicate subpattern numbers
1054    .\"
1055    in the
1056    .\" HREF
1057    \fBpcrepattern\fP
1058    .\"
1059    page. Duplicate names for subpatterns with different numbers are permitted only
1060    if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1061    table in the order in which they were found in the pattern. In the absence of
1062    (?| this is the order of increasing number; when (?| is used this is not
1063    necessarily the case because later subpatterns may have lower numbers.
1064    .P
1065    As a simple example of the name/number table, consider the following pattern
1066    (assume PCRE_EXTENDED is set, so white space - including newlines - is
1067    ignored):
1068  .sp  .sp
1069  .\" JOIN  .\" JOIN
1070    (?<date> (?<year>(\ed\ed)?\ed\ed) -    (?<date> (?<year>(\ed\ed)?\ed\ed) -
# Line 1056  variable. Line 1129  variable.
1129  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
1130  a \fBpcre_extra\fP block. That is, it is the value that was passed to  a \fBpcre_extra\fP block. That is, it is the value that was passed to
1131  \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data  \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1132  created by \fBpcre_study()\fP. The fourth argument should point to a  created by \fBpcre_study()\fP. If \fBpcre_extra\fP is NULL, or there is no
1133    study data, zero is returned. The fourth argument should point to a
1134  \fBsize_t\fP variable.  \fBsize_t\fP variable.
1135  .  .
1136  .  .
# Line 1118  is different. (This seems a highly unlik Line 1192  is different. (This seems a highly unlik
1192  .P  .P
1193  The function \fBpcre_exec()\fP is called to match a subject string against a  The function \fBpcre_exec()\fP is called to match a subject string against a
1194  compiled pattern, which is passed in the \fIcode\fP argument. If the  compiled pattern, which is passed in the \fIcode\fP argument. If the
1195  pattern has been studied, the result of the study should be passed in the  pattern was studied, the result of the study should be passed in the
1196  \fIextra\fP argument. This function is the main matching facility of the  \fIextra\fP argument. This function is the main matching facility of the
1197  library, and it operates in a Perl-like manner. For specialist use there is  library, and it operates in a Perl-like manner. For specialist use there is
1198  also an alternative matching function, which is described  also an alternative matching function, which is described
# Line 1168  fields (not necessarily in this order): Line 1242  fields (not necessarily in this order):
1242    unsigned long int \fImatch_limit_recursion\fP;    unsigned long int \fImatch_limit_recursion\fP;
1243    void *\fIcallout_data\fP;    void *\fIcallout_data\fP;
1244    const unsigned char *\fItables\fP;    const unsigned char *\fItables\fP;
1245      unsigned char **\fImark\fP;
1246  .sp  .sp
1247  The \fIflags\fP field is a bitmap that specifies which of the other fields  The \fIflags\fP field is a bitmap that specifies which of the other fields
1248  are set. The flag bits are:  are set. The flag bits are:
# Line 1177  are set. The flag bits are: Line 1252  are set. The flag bits are:
1252    PCRE_EXTRA_MATCH_LIMIT_RECURSION    PCRE_EXTRA_MATCH_LIMIT_RECURSION
1253    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1254    PCRE_EXTRA_TABLES    PCRE_EXTRA_TABLES
1255      PCRE_EXTRA_MARK
1256  .sp  .sp
1257  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 is set in the
1258  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
# Line 1186  the block by setting the other fields an Line 1262  the block by setting the other fields an
1262  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
1263  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,
1264  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
1265  classic example is the use of nested unlimited repeats.  classic example is a pattern that uses nested unlimited repeats.
1266  .P  .P
1267  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1268  (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the  (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
# Line 1239  called. See the Line 1315  called. See the
1315  \fBpcreprecompile\fP  \fBpcreprecompile\fP
1316  .\"  .\"
1317  documentation for a discussion of saving compiled patterns for later use.  documentation for a discussion of saving compiled patterns for later use.
1318    .P
1319    If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1320    be set to point to a \fBchar *\fP variable. If the pattern contains any
1321    backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1322    a name to pass back, a pointer to the name string (zero terminated) is placed
1323    in the variable pointed to by the \fImark\fP field. The names are within the
1324    compiled pattern; if you wish to retain such a name you must copy it before
1325    freeing the memory of a compiled pattern. If there is no name to pass back, the
1326    variable pointed to by the \fImark\fP field set to NULL. For details of the
1327    backtracking control verbs, see the section entitled
1328    .\" HTML <a href="pcrepattern#backtrackcontrol">
1329    .\" </a>
1330    "Backtracking control"
1331    .\"
1332    in the
1333    .\" HREF
1334    \fBpcrepattern\fP
1335    .\"
1336    documentation.
1337    .
1338  .  .
1339  .\" HTML <a name="execoptions"></a>  .\" HTML <a name="execoptions"></a>
1340  .SS "Option bits for \fBpcre_exec()\fP"  .SS "Option bits for \fBpcre_exec()\fP"
# Line 1246  documentation for a discussion of saving Line 1342  documentation for a discussion of saving
1342  .sp  .sp
1343  The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be  The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1344  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1345  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_START_OPTIMIZE,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1346  PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and PCRE_PARTIAL_HARD.  PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1347    PCRE_PARTIAL_HARD.
1348  .sp  .sp
1349    PCRE_ANCHORED    PCRE_ANCHORED
1350  .sp  .sp
# Line 1322  match the empty string, the entire match Line 1419  match the empty string, the entire match
1419  .sp  .sp
1420    a?b?    a?b?
1421  .sp  .sp
1422  is applied to a string not beginning with "a" or "b", it matches the empty  is applied to a string not beginning with "a" or "b", it matches an empty
1423  string at the start of the subject. With PCRE_NOTEMPTY set, this match is not  string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1424  valid, so PCRE searches further into the string for occurrences of "a" or "b".  valid, so PCRE searches further into the string for occurrences of "a" or "b".
1425  .P  .sp
1426  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1427  of a pattern match of the empty string within its \fBsplit()\fP function, and  .sp
1428  when using the /g modifier. It is possible to emulate Perl's behaviour after  This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1429  matching a null string by first trying the match again at the same offset with  the start of the subject is permitted. If the pattern is anchored, such a match
1430  PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the  can occur only if the pattern contains \eK.
1431  starting offset (see below) and trying an ordinary match again. There is some  .P
1432  code that demonstrates how to do this in the  Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1433    does make a special case of a pattern match of the empty string within its
1434    \fBsplit()\fP function, and when using the /g modifier. It is possible to
1435    emulate Perl's behaviour after matching a null string by first trying the match
1436    again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1437    if that fails, by advancing the starting offset (see below) and trying an
1438    ordinary match again. There is some code that demonstrates how to do this in
1439    the
1440  .\" HREF  .\" HREF
1441  \fBpcredemo\fP  \fBpcredemo\fP
1442  .\"  .\"
# Line 1341  sample program. Line 1445  sample program.
1445    PCRE_NO_START_OPTIMIZE    PCRE_NO_START_OPTIMIZE
1446  .sp  .sp
1447  There are a number of optimizations that \fBpcre_exec()\fP uses at the start of  There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1448  a match, in order to speed up the process. For example, if it is known that a  a match, in order to speed up the process. For example, if it is known that an
1449  match must start with a specific character, it searches the subject for that  unanchored match must start with a specific character, it searches the subject
1450  character, and fails immediately if it cannot find it, without actually running  for that character, and fails immediately if it cannot find it, without
1451  the main matching function. When callouts are in use, these optimizations can  actually running the main matching function. This means that a special item
1452  cause them to be skipped. This option disables the "start-up" optimizations,  such as (*COMMIT) at the start of a pattern is not considered until after a
1453  causing performance to suffer, but ensuring that the callouts do occur.  suitable starting point for the match has been found. When callouts or (*MARK)
1454    items are in use, these "start-up" optimizations can cause them to be skipped
1455    if the pattern is never actually used. The start-up optimizations are in effect
1456    a pre-scan of the subject that takes place before the pattern is run.
1457    .P
1458    The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1459    causing performance to suffer, but ensuring that in cases where the result is
1460    "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1461    are considered at every possible starting position in the subject string.
1462    Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1463    Consider the pattern
1464    .sp
1465      (*COMMIT)ABC
1466    .sp
1467    When this is compiled, PCRE records the fact that a match must start with the
1468    character "A". Suppose the subject string is "DEFABC". The start-up
1469    optimization scans along the subject, finds "A" and runs the first match
1470    attempt from there. The (*COMMIT) item means that the pattern must match the
1471    current starting position, which in this case, it does. However, if the same
1472    match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1473    subject string does not happen. The first match attempt is run starting from
1474    "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1475    the overall result is "no match". If the pattern is studied, more start-up
1476    optimizations may be used. For example, a minimum length for the subject may be
1477    recorded. Consider the pattern
1478    .sp
1479      (*MARK:A)(X|Y)
1480    .sp
1481    The minimum length for a match is one character. If the subject is "ABC", there
1482    will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1483    If the pattern is studied, the final attempt does not take place, because PCRE
1484    knows that the subject is too short, and so the (*MARK) is never encountered.
1485    In this case, studying the pattern does not affect the overall match result,
1486    which is still "no match", but it does affect the auxiliary information that is
1487    returned.
1488  .sp  .sp
1489    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
1490  .sp  .sp
# Line 1377  PCRE_NO_UTF8_CHECK is set, the effect of Line 1515  PCRE_NO_UTF8_CHECK is set, the effect of
1515  subject, or a value of \fIstartoffset\fP that does not point to the start of a  subject, or a value of \fIstartoffset\fP that does not point to the start of a
1516  UTF-8 character, is undefined. Your program may crash.  UTF-8 character, is undefined. Your program may crash.
1517  .sp  .sp
1518    PCRE_PARTIAL_HARD    PCRE_PARTIAL_HARD
1519    PCRE_PARTIAL_SOFT    PCRE_PARTIAL_SOFT
1520  .sp  .sp
1521  These options turn on the partial matching feature. For backwards  These options turn on the partial matching feature. For backwards
# Line 1477  the \fIovector\fP is not big enough to r Line 1615  the \fIovector\fP is not big enough to r
1615  has to get additional memory for use during matching. Thus it is usually  has to get additional memory for use during matching. Thus it is usually
1616  advisable to supply an \fIovector\fP.  advisable to supply an \fIovector\fP.
1617  .P  .P
1618  The \fBpcre_info()\fP function can be used to find out how many capturing  The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1619  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
1620  \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to  \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1621  the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.  the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
# Line 1541  If a pattern contains back references, b Line 1679  If a pattern contains back references, b
1679  gets a block of memory at the start of matching to use for this purpose. If the  gets a block of memory at the start of matching to use for this purpose. If the
1680  call via \fBpcre_malloc()\fP fails, this error is given. The memory is  call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1681  automatically freed at the end of matching.  automatically freed at the end of matching.
1682    .P
1683    This error is also given if \fBpcre_stack_malloc()\fP fails in
1684    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1685    \fB--disable-stack-for-recursion\fP.
1686  .sp  .sp
1687    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1688  .sp  .sp
# Line 1584  documentation for details of partial mat Line 1726  documentation for details of partial mat
1726  .sp  .sp
1727  This code is no longer in use. It was formerly returned when the PCRE_PARTIAL  This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1728  option was used with a compiled pattern containing items that were not  option was used with a compiled pattern containing items that were not
1729  supported for partial matching. From release 8.00 onwards, there are no  supported for partial matching. From release 8.00 onwards, there are no
1730  restrictions on partial matching.  restrictions on partial matching.
1731  .sp  .sp
1732    PCRE_ERROR_INTERNAL       (-14)    PCRE_ERROR_INTERNAL       (-14)
# Line 1756  then call \fBpcre_copy_substring()\fP or Line 1898  then call \fBpcre_copy_substring()\fP or
1898  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1899  the behaviour may not be what you want (see the next section).  the behaviour may not be what you want (see the next section).
1900  .P  .P
1901  \fBWarning:\fP If the pattern uses the "(?|" feature to set up multiple  \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
1902  subpatterns with the same number, you cannot use names to distinguish them,  subpatterns with the same number, as described in the
1903  because names are not included in the compiled code. The matching process uses  .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1904  only numbers.  .\" </a>
1905    section on duplicate subpattern numbers
1906    .\"
1907    in the
1908    .\" HREF
1909    \fBpcrepattern\fP
1910    .\"
1911    page, you cannot use names to distinguish the different subpatterns, because
1912    names are not included in the compiled code. The matching process uses only
1913    numbers. For this reason, the use of different names for subpatterns of the
1914    same number causes an error at compile time.
1915  .  .
1916  .SH "DUPLICATE SUBPATTERN NAMES"  .SH "DUPLICATE SUBPATTERN NAMES"
1917  .rs  .rs
# Line 1769  only numbers. Line 1921  only numbers.
1921  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1922  .PP  .PP
1923  When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns  When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1924  are not required to be unique. Normally, patterns with duplicate names are such  are not required to be unique. (Duplicate names are always allowed for
1925  that in any one match, only one of the named subpatterns participates. An  subpatterns with the same number, created by using the (?| feature. Indeed, if
1926  example is shown in the  such subpatterns are named, they are required to use the same names.)
1927    .P
1928    Normally, patterns with duplicate names are such that in any one match, only
1929    one of the named subpatterns participates. An example is shown in the
1930  .\" HREF  .\" HREF
1931  \fBpcrepattern\fP  \fBpcrepattern\fP
1932  .\"  .\"
# Line 1835  a compiled pattern, using a matching alg Line 1990  a compiled pattern, using a matching alg
1990  just once, and does not backtrack. This has different characteristics to the  just once, and does not backtrack. This has different characteristics to the
1991  normal algorithm, and is not compatible with Perl. Some of the features of PCRE  normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1992  patterns are not supported. Nevertheless, there are times when this kind of  patterns are not supported. Nevertheless, there are times when this kind of
1993  matching can be useful. For a discussion of the two matching algorithms, and a  matching can be useful. For a discussion of the two matching algorithms, and a
1994  list of features that \fBpcre_dfa_exec()\fP does not support, see the  list of features that \fBpcre_dfa_exec()\fP does not support, see the
1995  .\" HREF  .\" HREF
1996  \fBpcrematching\fP  \fBpcrematching\fP
# Line 1875  Here is an example of a simple call to \ Line 2030  Here is an example of a simple call to \
2030  .sp  .sp
2031  The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be  The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2032  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2033  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2034  PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last  PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2035  four of these are exactly the same as for \fBpcre_exec()\fP, so their  PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2036  description is not repeated here.  All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2037    so their description is not repeated here.
2038  .sp  .sp
2039    PCRE_PARTIAL_HARD    PCRE_PARTIAL_HARD
2040    PCRE_PARTIAL_SOFT    PCRE_PARTIAL_SOFT
2041  .sp  .sp
2042  These have the same general effect as they do for \fBpcre_exec()\fP, but the  These have the same general effect as they do for \fBpcre_exec()\fP, but the
2043  details are slightly different. When PCRE_PARTIAL_HARD is set for  details are slightly different. When PCRE_PARTIAL_HARD is set for
# Line 2012  Cambridge CB2 3QH, England. Line 2168  Cambridge CB2 3QH, England.
2168  .rs  .rs
2169  .sp  .sp
2170  .nf  .nf
2171  Last updated: 09 September 2009  Last updated: 20 June 2010
2172  Copyright (c) 1997-2009 University of Cambridge.  Copyright (c) 1997-2010 University of Cambridge.
2173  .fi  .fi

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