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revision 426 by ph10, Wed Aug 26 15:38:32 2009 UTC revision 455 by ph10, Sat Sep 26 19:12:32 2009 UTC
# Line 135  Applications can use these to include su Line 135  Applications can use these to include su
135  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
136  and \fBpcre_exec()\fP are used for compiling and matching regular expressions  and \fBpcre_exec()\fP are used for compiling and matching regular expressions
137  in a Perl-compatible manner. A sample program that demonstrates the simplest  in a Perl-compatible manner. A sample program that demonstrates the simplest
138  way of using them is provided in the file called \fIpcredemo.c\fP in the source  way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
139  distribution. The  source distribution. A listing of this program is given in the
140    .\" HREF
141    \fBpcredemo\fP
142    .\"
143    documentation, and the
144  .\" HREF  .\" HREF
145  \fBpcresample\fP  \fBpcresample\fP
146  .\"  .\"
# Line 145  documentation describes how to compile a Line 149  documentation describes how to compile a
149  A second matching function, \fBpcre_dfa_exec()\fP, which is not  A second matching function, \fBpcre_dfa_exec()\fP, which is not
150  Perl-compatible, is also provided. This uses a different algorithm for the  Perl-compatible, is also provided. This uses a different algorithm for the
151  matching. The alternative algorithm finds all possible matches (at a given  matching. The alternative algorithm finds all possible matches (at a given
152  point in the subject), and scans the subject just once. However, this algorithm  point in the subject), and scans the subject just once (unless there are
153  does not return captured substrings. A description of the two matching  lookbehind assertions). However, this algorithm does not return captured
154  algorithms and their advantages and disadvantages is given in the  substrings. A description of the two matching algorithms and their advantages
155    and disadvantages is given in the
156  .\" HREF  .\" HREF
157  \fBpcrematching\fP  \fBpcrematching\fP
158  .\"  .\"
# Line 422  If \fIerrptr\fP is NULL, \fBpcre_compile Line 427  If \fIerrptr\fP is NULL, \fBpcre_compile
427  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
428  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
429  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
430  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
431  where the error was discovered is placed in the variable pointed to by  character that was being processes when the error was discovered is placed in
432  \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,
433    an immediate error is given. Some errors are not detected until checks are
434    carried out when the whole pattern has been scanned; in this case the offset is
435    set to the end of the pattern.
436  .P  .P
437  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
438  \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 764  help speed up matching, \fBpcre_study()\ Line 772  help speed up matching, \fBpcre_study()\
772  results of the study.  results of the study.
773  .P  .P
774  The returned value from \fBpcre_study()\fP can be passed directly to  The returned value from \fBpcre_study()\fP can be passed directly to
775  \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
776  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
777  described  passed; these are described
778  .\" HTML <a href="#extradata">  .\" HTML <a href="#extradata">
779  .\" </a>  .\" </a>
780  below  below
781  .\"  .\"
782  in the section on matching a pattern.  in the section on matching a pattern.
783  .P  .P
784  If studying the pattern does not produce any additional information  If studying the pattern does not produce any useful information,
785  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
786  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
787  own \fBpcre_extra\fP block.  \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
788  .P  .P
789  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
790  options are defined, and this argument should always be zero.  options are defined, and this argument should always be zero.
# Line 796  This is a typical call to \fBpcre_study\ Line 804  This is a typical call to \fBpcre_study\
804      0,              /* no options exist */      0,              /* no options exist */
805      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
806  .sp  .sp
807  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
808  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
809  bytes is created.  mean that there are any strings of that length that match, but it does
810    guarantee that no shorter strings match. The value is used by
811    \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
812    match strings that are shorter than the lower bound. You can find out the value
813    in a calling program via the \fBpcre_fullinfo()\fP function.
814    .P
815    Studying a pattern is also useful for non-anchored patterns that do not have a
816    single fixed starting character. A bitmap of possible starting bytes is
817    created. This speeds up finding a position in the subject at which to start
818    matching.
819  .  .
820  .  .
821  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
# Line 963  follows something of variable length. Fo Line 980  follows something of variable length. Fo
980  /^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
981  is -1.  is -1.
982  .sp  .sp
983      PCRE_INFO_MINLENGTH
984    .sp
985    If the pattern was studied and a minimum length for matching subject strings
986    was computed, its value is returned. Otherwise the returned value is -1. The
987    value is a number of characters, not bytes (there may be a difference in UTF-8
988    mode). The fourth argument should point to an \fBint\fP variable. A
989    non-negative value is a lower bound to the length of any matching string. There
990    may not be any strings of that length that do actually match, but every string
991    that does match is at least that long.
992    .sp
993    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
994    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
995    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
# Line 1007  different for each compiled pattern. Line 1034  different for each compiled pattern.
1034  .sp  .sp
1035    PCRE_INFO_OKPARTIAL    PCRE_INFO_OKPARTIAL
1036  .sp  .sp
1037  Return 1 if the pattern can be used for partial matching, otherwise 0. The  Return 1 if the pattern can be used for partial matching with
1038  fourth argument should point to an \fBint\fP variable. From release 8.00, this  \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1039  always returns 1, because the restrictions that previously applied to partial  \fBint\fP variable. From release 8.00, this always returns 1, because the
1040  matching have been lifted. The  restrictions that previously applied to partial matching have been lifted. The
1041  .\" HREF  .\" HREF
1042  \fBpcrepartial\fP  \fBpcrepartial\fP
1043  .\"  .\"
# Line 1051  variable. Line 1078  variable.
1078  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
1079  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
1080  \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
1081  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
1082    study data, zero is returned. The fourth argument should point to a
1083  \fBsize_t\fP variable.  \fBsize_t\fP variable.
1084  .  .
1085  .  .
# Line 1113  is different. (This seems a highly unlik Line 1141  is different. (This seems a highly unlik
1141  .P  .P
1142  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
1143  compiled pattern, which is passed in the \fIcode\fP argument. If the  compiled pattern, which is passed in the \fIcode\fP argument. If the
1144  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
1145  \fIextra\fP argument. This function is the main matching facility of the  \fIextra\fP argument. This function is the main matching facility of the
1146  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
1147  also an alternative matching function, which is described  also an alternative matching function, which is described
# Line 1214  with a \fBpcre_extra\fP block in which \ Line 1242  with a \fBpcre_extra\fP block in which \
1242  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1243  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1244  .P  .P
1245  The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,  The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1246  which is described in the  and is described in the
1247  .\" HREF  .\" HREF
1248  \fBpcrecallout\fP  \fBpcrecallout\fP
1249  .\"  .\"
# Line 1241  documentation for a discussion of saving Line 1269  documentation for a discussion of saving
1269  .sp  .sp
1270  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
1271  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,
1272  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_START_OPTIMIZE,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1273  PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.  PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1274    PCRE_PARTIAL_HARD.
1275  .sp  .sp
1276    PCRE_ANCHORED    PCRE_ANCHORED
1277  .sp  .sp
# Line 1317  match the empty string, the entire match Line 1346  match the empty string, the entire match
1346  .sp  .sp
1347    a?b?    a?b?
1348  .sp  .sp
1349  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
1350  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
1351  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".
1352  .P  .sp
1353  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1354  of a pattern match of the empty string within its \fBsplit()\fP function, and  .sp
1355  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
1356  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
1357  PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the  can occur only if the pattern contains \eK.
1358  starting offset (see below) and trying an ordinary match again. There is some  .P
1359  code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.  Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1360    does make a special case of a pattern match of the empty string within its
1361    \fBsplit()\fP function, and when using the /g modifier. It is possible to
1362    emulate Perl's behaviour after matching a null string by first trying the match
1363    again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1364    if that fails, by advancing the starting offset (see below) and trying an
1365    ordinary match again. There is some code that demonstrates how to do this in
1366    the
1367    .\" HREF
1368    \fBpcredemo\fP
1369    .\"
1370    sample program.
1371  .sp  .sp
1372    PCRE_NO_START_OPTIMIZE    PCRE_NO_START_OPTIMIZE
1373  .sp  .sp
# Line 1368  PCRE_NO_UTF8_CHECK is set, the effect of Line 1408  PCRE_NO_UTF8_CHECK is set, the effect of
1408  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
1409  UTF-8 character, is undefined. Your program may crash.  UTF-8 character, is undefined. Your program may crash.
1410  .sp  .sp
1411    PCRE_PARTIAL    PCRE_PARTIAL_HARD
1412      PCRE_PARTIAL_SOFT
1413  .sp  .sp
1414  This option turns on the partial matching feature. If the subject string fails  These options turn on the partial matching feature. For backwards
1415  to match the pattern, but at some point during the matching process the end of  compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1416  the subject was reached (that is, the subject partially matches the pattern and  occurs if the end of the subject string is reached successfully, but there are
1417  the failure to match occurred only because there were not enough subject  not enough subject characters to complete the match. If this happens when
1418  characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of  PCRE_PARTIAL_HARD is set, \fBpcre_exec()\fP immediately returns
1419  PCRE_ERROR_NOMATCH. The portion of the string that provided the longest partial  PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
1420  match is set as the first matching string. There is further discussion in the  by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
1421    returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
1422    was inspected when the partial match was found is set as the first matching
1423    string. There is a more detailed discussion in the
1424  .\" HREF  .\" HREF
1425  \fBpcrepartial\fP  \fBpcrepartial\fP
1426  .\"  .\"
# Line 1822  a compiled pattern, using a matching alg Line 1866  a compiled pattern, using a matching alg
1866  just once, and does not backtrack. This has different characteristics to the  just once, and does not backtrack. This has different characteristics to the
1867  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
1868  patterns are not supported. Nevertheless, there are times when this kind of  patterns are not supported. Nevertheless, there are times when this kind of
1869  matching can be useful. For a discussion of the two matching algorithms, see  matching can be useful. For a discussion of the two matching algorithms, and a
1870  the  list of features that \fBpcre_dfa_exec()\fP does not support, see the
1871  .\" HREF  .\" HREF
1872  \fBpcrematching\fP  \fBpcrematching\fP
1873  .\"  .\"
# Line 1862  Here is an example of a simple call to \ Line 1906  Here is an example of a simple call to \
1906  .sp  .sp
1907  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
1908  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,
1909  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1910  PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are  PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST,
1911  exactly the same as for \fBpcre_exec()\fP, so their description is not repeated  and PCRE_DFA_RESTART. All but the last four of these are exactly the same as
1912  here.  for \fBpcre_exec()\fP, so their description is not repeated here.
1913  .sp  .sp
1914    PCRE_PARTIAL    PCRE_PARTIAL_HARD
1915  .sp    PCRE_PARTIAL_SOFT
1916  This has the same general effect as it does for \fBpcre_exec()\fP, but the  .sp
1917  details are slightly different. When PCRE_PARTIAL is set for  These have the same general effect as they do for \fBpcre_exec()\fP, but the
1918  \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into  details are slightly different. When PCRE_PARTIAL_HARD is set for
1919  PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no  \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
1920  complete matches, but there is still at least one matching possibility. The  is reached and there is still at least one matching possibility that requires
1921  portion of the string that provided the longest partial match is set as the  additional characters. This happens even if some complete matches have also
1922  first matching string.  been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
1923    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
1924    there have been no complete matches, but there is still at least one matching
1925    possibility. The portion of the string that was inspected when the longest
1926    partial match was found is set as the first matching string in both cases.
1927  .sp  .sp
1928    PCRE_DFA_SHORTEST    PCRE_DFA_SHORTEST
1929  .sp  .sp
# Line 1886  matching point in the subject string. Line 1934  matching point in the subject string.
1934  .sp  .sp
1935    PCRE_DFA_RESTART    PCRE_DFA_RESTART
1936  .sp  .sp
1937  When \fBpcre_dfa_exec()\fP is called with the PCRE_PARTIAL option, and returns  When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
1938  a partial match, it is possible to call it again, with additional subject  again, with additional subject characters, and have it continue with the same
1939  characters, and have it continue with the same match. The PCRE_DFA_RESTART  match. The PCRE_DFA_RESTART option requests this action; when it is set, the
1940  option requests this action; when it is set, the \fIworkspace\fP and  \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
1941  \fIwscount\fP options must reference the same vector as before because data  before because data about the match so far is left in them after a partial
1942  about the match so far is left in them after a partial match. There is more  match. There is more discussion of this facility in the
 discussion of this facility in the  
1943  .\" HREF  .\" HREF
1944  \fBpcrepartial\fP  \fBpcrepartial\fP
1945  .\"  .\"
# Line 1996  Cambridge CB2 3QH, England. Line 2043  Cambridge CB2 3QH, England.
2043  .rs  .rs
2044  .sp  .sp
2045  .nf  .nf
2046  Last updated: 26 August 2009  Last updated: 26 September 2009
2047  Copyright (c) 1997-2009 University of Cambridge.  Copyright (c) 1997-2009 University of Cambridge.
2048  .fi  .fi
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