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revision 440 by ph10, Wed Sep 9 10:14:40 2009 UTC revision 457 by ph10, Sat Oct 3 16:24:08 2009 UTC
# Line 395  avoiding the use of the stack. Line 395  avoiding the use of the stack.
395  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
396  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
397  the two interfaces is that \fBpcre_compile2()\fP has an additional argument,  the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
398  \fIerrorcodeptr\fP, via which a numerical error code can be returned.  \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
399    too much repetition, we refer just to \fBpcre_compile()\fP below, but the
400    information applies equally to \fBpcre_compile2()\fP.
401  .P  .P
402  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
403  \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 414  argument, which is an address (see below
414  The \fIoptions\fP argument contains various bit settings that affect the  The \fIoptions\fP argument contains various bit settings that affect the
415  compilation. It should be zero if no options are required. The available  compilation. It should be zero if no options are required. The available
416  options are described below. Some of them (in particular, those that are  options are described below. Some of them (in particular, those that are
417  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
418  within the pattern (see the detailed description in the  within the pattern (see the detailed description in the
419  .\" HREF  .\" HREF
420  \fBpcrepattern\fP  \fBpcrepattern\fP
421  .\"  .\"
422  documentation). For those options that can be different in different parts of  documentation). For those options that can be different in different parts of
423  the pattern, the contents of the \fIoptions\fP argument specifies their initial  the pattern, the contents of the \fIoptions\fP argument specifies their
424  settings at the start of compilation and execution. The PCRE_ANCHORED and  settings at the start of compilation and execution. The PCRE_ANCHORED,
425  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
426  compile time.  of matching as well as at compile time.
427  .P  .P
428  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
429  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
430  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
431  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
432  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
433  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
434  \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,
435    an immediate error is given. Some errors are not detected until checks are
436    carried out when the whole pattern has been scanned; in this case the offset is
437    set to the end of the pattern.
438  .P  .P
439  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
440  \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 769  help speed up matching, \fBpcre_study()\ Line 774  help speed up matching, \fBpcre_study()\
774  results of the study.  results of the study.
775  .P  .P
776  The returned value from \fBpcre_study()\fP can be passed directly to  The returned value from \fBpcre_study()\fP can be passed directly to
777  \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
778  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
779  described  passed; these are described
780  .\" HTML <a href="#extradata">  .\" HTML <a href="#extradata">
781  .\" </a>  .\" </a>
782  below  below
783  .\"  .\"
784  in the section on matching a pattern.  in the section on matching a pattern.
785  .P  .P
786  If studying the pattern does not produce any additional information  If studying the pattern does not produce any useful information,
787  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
788  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
789  own \fBpcre_extra\fP block.  \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
790  .P  .P
791  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
792  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 806  This is a typical call to \fBpcre_study\
806      0,              /* no options exist */      0,              /* no options exist */
807      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
808  .sp  .sp
809  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
810  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
811  bytes is created.  mean that there are any strings of that length that match, but it does
812    guarantee that no shorter strings match. The value is used by
813    \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
814    match strings that are shorter than the lower bound. You can find out the value
815    in a calling program via the \fBpcre_fullinfo()\fP function.
816    .P
817    Studying a pattern is also useful for non-anchored patterns that do not have a
818    single fixed starting character. A bitmap of possible starting bytes is
819    created. This speeds up finding a position in the subject at which to start
820    matching.
821  .  .
822  .  .
823  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
# Line 968  follows something of variable length. Fo Line 982  follows something of variable length. Fo
982  /^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
983  is -1.  is -1.
984  .sp  .sp
985      PCRE_INFO_MINLENGTH
986    .sp
987    If the pattern was studied and a minimum length for matching subject strings
988    was computed, its value is returned. Otherwise the returned value is -1. The
989    value is a number of characters, not bytes (this may be relevant in UTF-8
990    mode). The fourth argument should point to an \fBint\fP variable. A
991    non-negative value is a lower bound to the length of any matching string. There
992    may not be any strings of that length that do actually match, but every string
993    that does match is at least that long.
994    .sp
995    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
996    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
997    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
# Line 988  entry; both of these return an \fBint\fP Line 1012  entry; both of these return an \fBint\fP
1012  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
1013  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
1014  are the number of the capturing parenthesis, most significant byte first. The  are the number of the capturing parenthesis, most significant byte first. The
1015  rest of the entry is the corresponding name, zero terminated. The names are in  rest of the entry is the corresponding name, zero terminated.
1016  alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of  .P
1017  their parentheses numbers. For example, consider the following pattern (assume  The names are in alphabetical order. Duplicate names may appear if (?| is used
1018  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  to create multiple groups with the same number, as described in the
1019    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1020    .\" </a>
1021    section on duplicate subpattern numbers
1022    .\"
1023    in the
1024    .\" HREF
1025    \fBpcrepattern\fP
1026    .\"
1027    page. Duplicate names for subpatterns with different numbers are permitted only
1028    if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1029    table in the order in which they were found in the pattern. In the absence of
1030    (?| this is the order of increasing number; when (?| is used this is not
1031    necessarily the case because later subpatterns may have lower numbers.
1032    .P
1033    As a simple example of the name/number table, consider the following pattern
1034    (assume PCRE_EXTENDED is set, so white space - including newlines - is
1035    ignored):
1036  .sp  .sp
1037  .\" JOIN  .\" JOIN
1038    (?<date> (?<year>(\ed\ed)?\ed\ed) -    (?<date> (?<year>(\ed\ed)?\ed\ed) -
# Line 1056  variable. Line 1097  variable.
1097  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
1098  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
1099  \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
1100  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
1101    study data, zero is returned. The fourth argument should point to a
1102  \fBsize_t\fP variable.  \fBsize_t\fP variable.
1103  .  .
1104  .  .
# Line 1118  is different. (This seems a highly unlik Line 1160  is different. (This seems a highly unlik
1160  .P  .P
1161  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
1162  compiled pattern, which is passed in the \fIcode\fP argument. If the  compiled pattern, which is passed in the \fIcode\fP argument. If the
1163  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
1164  \fIextra\fP argument. This function is the main matching facility of the  \fIextra\fP argument. This function is the main matching facility of the
1165  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
1166  also an alternative matching function, which is described  also an alternative matching function, which is described
# Line 1186  the block by setting the other fields an Line 1228  the block by setting the other fields an
1228  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
1229  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,
1230  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
1231  classic example is the use of nested unlimited repeats.  classic example is a pattern that uses nested unlimited repeats.
1232  .P  .P
1233  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1234  (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 1246  documentation for a discussion of saving Line 1288  documentation for a discussion of saving
1288  .sp  .sp
1289  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
1290  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,
1291  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_START_OPTIMIZE,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1292  PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and PCRE_PARTIAL_HARD.  PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1293    PCRE_PARTIAL_HARD.
1294  .sp  .sp
1295    PCRE_ANCHORED    PCRE_ANCHORED
1296  .sp  .sp
# Line 1322  match the empty string, the entire match Line 1365  match the empty string, the entire match
1365  .sp  .sp
1366    a?b?    a?b?
1367  .sp  .sp
1368  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
1369  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
1370  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".
1371  .P  .sp
1372  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1373  of a pattern match of the empty string within its \fBsplit()\fP function, and  .sp
1374  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
1375  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
1376  PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the  can occur only if the pattern contains \eK.
1377  starting offset (see below) and trying an ordinary match again. There is some  .P
1378  code that demonstrates how to do this in the  Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1379    does make a special case of a pattern match of the empty string within its
1380    \fBsplit()\fP function, and when using the /g modifier. It is possible to
1381    emulate Perl's behaviour after matching a null string by first trying the match
1382    again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1383    if that fails, by advancing the starting offset (see below) and trying an
1384    ordinary match again. There is some code that demonstrates how to do this in
1385    the
1386  .\" HREF  .\" HREF
1387  \fBpcredemo\fP  \fBpcredemo\fP
1388  .\"  .\"
# Line 1477  the \fIovector\fP is not big enough to r Line 1527  the \fIovector\fP is not big enough to r
1527  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
1528  advisable to supply an \fIovector\fP.  advisable to supply an \fIovector\fP.
1529  .P  .P
1530  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
1531  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
1532  \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
1533  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 1756  then call \fBpcre_copy_substring()\fP or Line 1806  then call \fBpcre_copy_substring()\fP or
1806  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,
1807  the behaviour may not be what you want (see the next section).  the behaviour may not be what you want (see the next section).
1808  .P  .P
1809  \fBWarning:\fP If the pattern uses the "(?|" feature to set up multiple  \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
1810  subpatterns with the same number, you cannot use names to distinguish them,  subpatterns with the same number, as described in the
1811  because names are not included in the compiled code. The matching process uses  .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1812  only numbers.  .\" </a>
1813    section on duplicate subpattern numbers
1814    .\"
1815    in the
1816    .\" HREF
1817    \fBpcrepattern\fP
1818    .\"
1819    page, you cannot use names to distinguish the different subpatterns, because
1820    names are not included in the compiled code. The matching process uses only
1821    numbers. For this reason, the use of different names for subpatterns of the
1822    same number causes an error at compile time.
1823  .  .
1824  .SH "DUPLICATE SUBPATTERN NAMES"  .SH "DUPLICATE SUBPATTERN NAMES"
1825  .rs  .rs
# Line 1769  only numbers. Line 1829  only numbers.
1829  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1830  .PP  .PP
1831  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
1832  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
1833  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
1834  example is shown in the  such subpatterns are named, they are required to use the same names.)
1835    .P
1836    Normally, patterns with duplicate names are such that in any one match, only
1837    one of the named subpatterns participates. An example is shown in the
1838  .\" HREF  .\" HREF
1839  \fBpcrepattern\fP  \fBpcrepattern\fP
1840  .\"  .\"
# Line 1875  Here is an example of a simple call to \ Line 1938  Here is an example of a simple call to \
1938  .sp  .sp
1939  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
1940  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,
1941  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1942  PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last  PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST,
1943  four of these are exactly the same as for \fBpcre_exec()\fP, so their  and PCRE_DFA_RESTART. All but the last four of these are exactly the same as
1944  description is not repeated here.  for \fBpcre_exec()\fP, so their description is not repeated here.
1945  .sp  .sp
1946    PCRE_PARTIAL_HARD    PCRE_PARTIAL_HARD
1947    PCRE_PARTIAL_SOFT    PCRE_PARTIAL_SOFT
# Line 2012  Cambridge CB2 3QH, England. Line 2075  Cambridge CB2 3QH, England.
2075  .rs  .rs
2076  .sp  .sp
2077  .nf  .nf
2078  Last updated: 09 September 2009  Last updated: 03 October 2009
2079  Copyright (c) 1997-2009 University of Cambridge.  Copyright (c) 1997-2009 University of Cambridge.
2080  .fi  .fi

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