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revision 455 by ph10, Sat Sep 26 19:12:32 2009 UTC revision 461 by ph10, Mon Oct 5 10:59:35 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 byte offset from the start of the pattern to the  not try to free it. The byte offset from the start of the pattern to the
433  character that was being processes when the error was discovered is placed in  character that was being processed when the error was discovered is placed in
434  the variable pointed to by \fIerroffset\fP, which must not be NULL. If it is,  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  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  carried out when the whole pattern has been scanned; in this case the offset is
# Line 783  in the section on matching a pattern. Line 785  in the section on matching a pattern.
785  .P  .P
786  If studying the pattern does not produce any useful 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 or  wants to pass any of the other fields to \fBpcre_exec()\fP or
789  \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.
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
# Line 805  This is a typical call to \fBpcre_study\ Line 807  This is a typical call to \fBpcre_study\
807      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
808  .sp  .sp
809  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
810  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
811  mean that there are any strings of that length that match, but it does  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  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  \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  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.  in a calling program via the \fBpcre_fullinfo()\fP function.
816  .P  .P
817  Studying a pattern is also useful for non-anchored patterns that do not have a  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  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  created. This speeds up finding a position in the subject at which to start
820  matching.  matching.
821  .  .
822  .  .
# Line 984  is -1. Line 986  is -1.
986  .sp  .sp
987  If the pattern was studied and a minimum length for matching subject strings  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  was computed, its value is returned. Otherwise the returned value is -1. The
989  value is a number of characters, not bytes (there may be a difference in UTF-8  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  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  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  may not be any strings of that length that do actually match, but every string
# Line 1010  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 1209  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 1352  valid, so PCRE searches further into the Line 1371  valid, so PCRE searches further into the
1371  .sp  .sp
1372    PCRE_NOTEMPTY_ATSTART    PCRE_NOTEMPTY_ATSTART
1373  .sp  .sp
1374  This is like PCRE_NOTEMPTY, except that an empty string match that is not at  This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1375  the start of the subject is permitted. If the pattern is anchored, such a match  the start of the subject is permitted. If the pattern is anchored, such a match
1376  can occur only if the pattern contains \eK.  can occur only if the pattern contains \eK.
1377  .P  .P
# Line 1408  PCRE_NO_UTF8_CHECK is set, the effect of Line 1427  PCRE_NO_UTF8_CHECK is set, the effect of
1427  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
1428  UTF-8 character, is undefined. Your program may crash.  UTF-8 character, is undefined. Your program may crash.
1429  .sp  .sp
1430    PCRE_PARTIAL_HARD    PCRE_PARTIAL_HARD
1431    PCRE_PARTIAL_SOFT    PCRE_PARTIAL_SOFT
1432  .sp  .sp
1433  These options turn on the partial matching feature. For backwards  These options turn on the partial matching feature. For backwards
# Line 1508  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 1615  documentation for details of partial mat Line 1634  documentation for details of partial mat
1634  .sp  .sp
1635  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
1636  option was used with a compiled pattern containing items that were not  option was used with a compiled pattern containing items that were not
1637  supported for partial matching. From release 8.00 onwards, there are no  supported for partial matching. From release 8.00 onwards, there are no
1638  restrictions on partial matching.  restrictions on partial matching.
1639  .sp  .sp
1640    PCRE_ERROR_INTERNAL       (-14)    PCRE_ERROR_INTERNAL       (-14)
# Line 1787  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 1800  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 1866  a compiled pattern, using a matching alg Line 1898  a compiled pattern, using a matching alg
1898  just once, and does not backtrack. This has different characteristics to the  just once, and does not backtrack. This has different characteristics to the
1899  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
1900  patterns are not supported. Nevertheless, there are times when this kind of  patterns are not supported. Nevertheless, there are times when this kind of
1901  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
1902  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
1903  .\" HREF  .\" HREF
1904  \fBpcrematching\fP  \fBpcrematching\fP
# Line 1912  and PCRE_DFA_RESTART. All but the last f Line 1944  and PCRE_DFA_RESTART. All but the last f
1944  for \fBpcre_exec()\fP, so their 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
1948  .sp  .sp
1949  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
1950  details are slightly different. When PCRE_PARTIAL_HARD is set for  details are slightly different. When PCRE_PARTIAL_HARD is set for
# Line 2043  Cambridge CB2 3QH, England. Line 2075  Cambridge CB2 3QH, England.
2075  .rs  .rs
2076  .sp  .sp
2077  .nf  .nf
2078  Last updated: 26 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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