/[pcre]/code/trunk/doc/pcreapi.3
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revision 525 by ph10, Wed May 26 10:50:24 2010 UTC revision 553 by ph10, Fri Oct 22 15:57:50 2010 UTC
# Line 134  Applications can use these to include su Line 134  Applications can use these to include su
134  .P  .P
135  In a Windows environment, if you want to statically link an application program  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  against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
137  including \fBpcre.h\fP, because otherwise the \fBpcre_malloc()\fP and  including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
138  \fBpcre_free()\fP exported functions will be declared  \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
139  \fB__declspec(dllimport)\fP, with unwanted results.  \fB__declspec(dllimport)\fP, with unwanted results.
140  .P  .P
141  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
# Line 765  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
# Line 778  out of use. To avoid confusion, they hav Line 779  out of use. To avoid confusion, they hav
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 not allowed    65  different names for subpatterns of the same number are
783            not allowed
784    66  (*MARK) must have an argument    66  (*MARK) must have an argument
785    67  this version of PCRE is not compiled with PCRE_UCP support    67  this version of PCRE is not compiled with PCRE_UCP support
786  .sp  .sp
# Line 846  Studying a pattern is also useful for no Line 848  Studying a pattern is also useful for no
848  single fixed starting character. A bitmap of possible starting bytes is  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  created. This speeds up finding a position in the subject at which to start
850  matching.  matching.
851    .P
852    The two optimizations just described can be disabled by setting the
853    PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
854    \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
855    callouts, or make use of (*MARK), and you make use of these in cases where
856    matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
857    .\" HTML <a href="#execoptions">
858    .\" </a>
859    below.
860    .\"
861  .  .
862  .  .
863  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
# Line 1443  sample program. Line 1455  sample program.
1455    PCRE_NO_START_OPTIMIZE    PCRE_NO_START_OPTIMIZE
1456  .sp  .sp
1457  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
1458  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
1459  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
1460  character, and fails immediately if it cannot find it, without actually running  for that character, and fails immediately if it cannot find it, without
1461  the main matching function. When callouts are in use, these optimizations can  actually running the main matching function. This means that a special item
1462  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
1463  causing performance to suffer, but ensuring that the callouts do occur.  suitable starting point for the match has been found. When callouts or (*MARK)
1464    items are in use, these "start-up" optimizations can cause them to be skipped
1465    if the pattern is never actually used. The start-up optimizations are in effect
1466    a pre-scan of the subject that takes place before the pattern is run.
1467    .P
1468    The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1469    causing performance to suffer, but ensuring that in cases where the result is
1470    "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1471    are considered at every possible starting position in the subject string.
1472    Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1473    Consider the pattern
1474    .sp
1475      (*COMMIT)ABC
1476    .sp
1477    When this is compiled, PCRE records the fact that a match must start with the
1478    character "A". Suppose the subject string is "DEFABC". The start-up
1479    optimization scans along the subject, finds "A" and runs the first match
1480    attempt from there. The (*COMMIT) item means that the pattern must match the
1481    current starting position, which in this case, it does. However, if the same
1482    match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1483    subject string does not happen. The first match attempt is run starting from
1484    "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1485    the overall result is "no match". If the pattern is studied, more start-up
1486    optimizations may be used. For example, a minimum length for the subject may be
1487    recorded. Consider the pattern
1488    .sp
1489      (*MARK:A)(X|Y)
1490    .sp
1491    The minimum length for a match is one character. If the subject is "ABC", there
1492    will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1493    If the pattern is studied, the final attempt does not take place, because PCRE
1494    knows that the subject is too short, and so the (*MARK) is never encountered.
1495    In this case, studying the pattern does not affect the overall match result,
1496    which is still "no match", but it does affect the auxiliary information that is
1497    returned.
1498  .sp  .sp
1499    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
1500  .sp  .sp
# Line 1486  These options turn on the partial matchi Line 1532  These options turn on the partial matchi
1532  compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match  compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1533  occurs if the end of the subject string is reached successfully, but there are  occurs if the end of the subject string is reached successfully, but there are
1534  not enough subject characters to complete the match. If this happens when  not enough subject characters to complete the match. If this happens when
1535  PCRE_PARTIAL_HARD is set, \fBpcre_exec()\fP immediately returns  PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1536  PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues  testing any remaining alternatives. Only if no complete match can be found is
1537  by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL  PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1538  returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that  PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1539  was inspected when the partial match was found is set as the first matching  but only if no complete match can be found.
1540  string. There is a more detailed discussion in the  .P
1541    If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1542    partial match is found, \fBpcre_exec()\fP immediately returns
1543    PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1544    when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1545    important that an alternative complete match.
1546    .P
1547    In both cases, the portion of the string that was inspected when the partial
1548    match was found is set as the first matching string. There is a more detailed
1549    discussion of partial and multi-segment matching, with examples, in the
1550  .\" HREF  .\" HREF
1551  \fBpcrepartial\fP  \fBpcrepartial\fP
1552  .\"  .\"
# Line 1643  If a pattern contains back references, b Line 1698  If a pattern contains back references, b
1698  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
1699  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
1700  automatically freed at the end of matching.  automatically freed at the end of matching.
1701    .P
1702    This error is also given if \fBpcre_stack_malloc()\fP fails in
1703    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1704    \fB--disable-stack-for-recursion\fP.
1705  .sp  .sp
1706    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1707  .sp  .sp
# Line 1991  Here is an example of a simple call to \ Line 2050  Here is an example of a simple call to \
2050  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
2051  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,
2052  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2053  PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST,  PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2054  and PCRE_DFA_RESTART. All but the last four of these are exactly the same as  PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2055  for \fBpcre_exec()\fP, so their description is not repeated here.  All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2056    so their description is not repeated here.
2057  .sp  .sp
2058    PCRE_PARTIAL_HARD    PCRE_PARTIAL_HARD
2059    PCRE_PARTIAL_SOFT    PCRE_PARTIAL_SOFT
# Line 2008  is converted into PCRE_ERROR_PARTIAL if Line 2068  is converted into PCRE_ERROR_PARTIAL if
2068  there have been no complete matches, but there is still at least one matching  there have been no complete matches, but there is still at least one matching
2069  possibility. The portion of the string that was inspected when the longest  possibility. The portion of the string that was inspected when the longest
2070  partial match was found is set as the first matching string in both cases.  partial match was found is set as the first matching string in both cases.
2071    There is a more detailed discussion of partial and multi-segment matching, with
2072    examples, in the
2073    .\" HREF
2074    \fBpcrepartial\fP
2075    .\"
2076    documentation.
2077  .sp  .sp
2078    PCRE_DFA_SHORTEST    PCRE_DFA_SHORTEST
2079  .sp  .sp
# Line 2127  Cambridge CB2 3QH, England. Line 2193  Cambridge CB2 3QH, England.
2193  .rs  .rs
2194  .sp  .sp
2195  .nf  .nf
2196  Last updated: 26 May 2010  Last updated: 22 October 2010
2197  Copyright (c) 1997-2010 University of Cambridge.  Copyright (c) 1997-2010 University of Cambridge.
2198  .fi  .fi

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