/[pcre]/code/trunk/doc/pcreapi.3
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revision 518 by ph10, Tue May 18 15:47:01 2010 UTC revision 547 by ph10, Mon Jun 21 14:06:54 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 759  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 772  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 840  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 1437  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 1637  If a pattern contains back references, b Line 1689  If a pattern contains back references, b
1689  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
1690  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
1691  automatically freed at the end of matching.  automatically freed at the end of matching.
1692    .P
1693    This error is also given if \fBpcre_stack_malloc()\fP fails in
1694    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1695    \fB--disable-stack-for-recursion\fP.
1696  .sp  .sp
1697    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1698  .sp  .sp
# Line 1985  Here is an example of a simple call to \ Line 2041  Here is an example of a simple call to \
2041  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
2042  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,
2043  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2044  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,
2045  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.
2046  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,
2047    so their description is not repeated here.
2048  .sp  .sp
2049    PCRE_PARTIAL_HARD    PCRE_PARTIAL_HARD
2050    PCRE_PARTIAL_SOFT    PCRE_PARTIAL_SOFT
# Line 2121  Cambridge CB2 3QH, England. Line 2178  Cambridge CB2 3QH, England.
2178  .rs  .rs
2179  .sp  .sp
2180  .nf  .nf
2181  Last updated: 16 May 2010  Last updated: 21 June 2010
2182  Copyright (c) 1997-2010 University of Cambridge.  Copyright (c) 1997-2010 University of Cambridge.
2183  .fi  .fi

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