/[pcre]/code/trunk/doc/pcreapi.3

Diff of /code/trunk/doc/pcreapi.3

Parent Directory | Revision Log | View Patch Patch

-revision 345 by ph10,
Mon Apr 28 15:10:02 2008 UTC
+revision 442 by ph10,
Fri Sep 11 10:21:02 2009 UTC
 Line 135 
 Applications can use these to include su
  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
  and \fBpcre_exec()\fP are used for compiling and matching regular expressions
  in a Perl-compatible manner. A sample program that demonstrates the simplest
- 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
- distribution. The
+ source distribution. A listing of this program is given in the
+ .\" HREF
+ \fBpcredemo\fP
+ .\"
+ documentation, and the
  .\" HREF
  \fBpcresample\fP
  .\"
-Line 145 
 documentation describes how to compile a
+Line 149 
 documentation describes how to compile a
  A second matching function, \fBpcre_dfa_exec()\fP, which is not
  Perl-compatible, is also provided. This uses a different algorithm for the
  matching. The alternative algorithm finds all possible matches (at a given
- 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
- does not return captured substrings. A description of the two matching
+ lookbehind assertions). However, this algorithm does not return captured
- algorithms and their advantages and disadvantages is given in the
+ substrings. A description of the two matching algorithms and their advantages
+ and disadvantages is given in the
  .\" HREF
  \fBpcrematching\fP
  .\"
-Line 317 
 properties is available; otherwise it is
+Line 322 
 properties is available; otherwise it is
  .sp
  The output is an integer whose value specifies the default character sequence
  that is recognized as meaning "newline". The four values that are supported
- are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY. The
+ are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
- default should normally be the standard sequence for your operating system.
+ Though they are derived from ASCII, the same values are returned in EBCDIC
+ environments. The default should normally correspond to the standard sequence
+ for your operating system.
  .sp
    PCRE_CONFIG_BSR
  .sp
-Line 347 
 documentation.
+Line 354 
 documentation.
  .sp
    PCRE_CONFIG_MATCH_LIMIT
  .sp
- The output is an integer that gives the default limit for the number of
+ The output is a long integer that gives the default limit for the number of
  internal matching function calls in a \fBpcre_exec()\fP execution. Further
  details are given with \fBpcre_exec()\fP below.
  .sp
    PCRE_CONFIG_MATCH_LIMIT_RECURSION
  .sp
- The output is an integer that gives the default limit for the depth of
+ The output is a long integer that gives the default limit for the depth of
  recursion when calling the internal matching function in a \fBpcre_exec()\fP
  execution. Further details are given with \fBpcre_exec()\fP below.
  .sp
-Line 404 
 argument, which is an address (see below
+Line 411 
 argument, which is an address (see below
  .P
  The \fIoptions\fP argument contains various bit settings that affect the
  compilation. It should be zero if no options are required. The available
- options are described below. Some of them, in particular, those that are
+ options are described below. Some of them (in particular, those that are
- compatible with Perl, can also be set and unset from within the pattern (see
+ compatible with Perl, but also some others) can also be set and unset from
- the detailed description in the
+ within the pattern (see the detailed description in the
  .\" HREF
  \fBpcrepattern\fP
  .\"
- documentation). For these options, the contents of the \fIoptions\fP argument
+ documentation). For those options that can be different in different parts of
- specifies their initial settings at the start of compilation and execution. The
+ the pattern, the contents of the \fIoptions\fP argument specifies their initial
- PCRE_ANCHORED and PCRE_NEWLINE_\fIxxx\fP options can be set at the time of
+ settings at the start of compilation and execution. The PCRE_ANCHORED and
- matching as well as at compile time.
+ PCRE_NEWLINE_\fIxxx\fP options can be set at the time of matching as well as at
+ compile time.
  .P
  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
-Line 1004 
 different for each compiled pattern.
+Line 1012 
 different for each compiled pattern.
  .sp
    PCRE_INFO_OKPARTIAL
  .sp
- 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
- fourth argument should point to an \fBint\fP variable. The
+ \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
+ \fBint\fP variable. From release 8.00, this always returns 1, because the
+ restrictions that previously applied to partial matching have been lifted. The
  .\" HREF
  \fBpcrepartial\fP
  .\"
- documentation lists the restrictions that apply to patterns when partial
+ documentation gives details of partial matching.
- matching is used.
  .sp
    PCRE_INFO_OPTIONS
  .sp
-Line 1210 
 with a \fBpcre_extra\fP block in which \
+Line 1219 
 with a \fBpcre_extra\fP block in which \
  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
  .P
- 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,
- which is described in the
+ and is described in the
  .\" HREF
  \fBpcrecallout\fP
  .\"
-Line 1237 
 documentation for a discussion of saving
+Line 1246 
 documentation for a discussion of saving
  .sp
  The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
- PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
+ PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
+ PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
+ PCRE_PARTIAL_HARD.
  .sp
    PCRE_ANCHORED
  .sp
-Line 1312 
 match the empty string, the entire match
+Line 1323 
 match the empty string, the entire match
  .sp
    a?b?
  .sp
- 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
  string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
  valid, so PCRE searches further into the string for occurrences of "a" or "b".
- .P
+ .sp
- Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
+   PCRE_NOTEMPTY_ATSTART
- of a pattern match of the empty string within its \fBsplit()\fP function, and
+ .sp
- 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
- 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
- PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
+ can occur only if the pattern contains \eK.
- starting offset (see below) and trying an ordinary match again. There is some
+ .P
- 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
+ does make a special case of a pattern match of the empty string within its
+ \fBsplit()\fP function, and when using the /g modifier. It is possible to
+ emulate Perl's behaviour after matching a null string by first trying the match
+ again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
+ if that fails, by advancing the starting offset (see below) and trying an
+ ordinary match again. There is some code that demonstrates how to do this in
+ the
+ .\" HREF
+ \fBpcredemo\fP
+ .\"
+ sample program.
+ .sp
+   PCRE_NO_START_OPTIMIZE
+ .sp
+ There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
+ a match, in order to speed up the process. For example, if it is known that a
+ match must start with a specific character, it searches the subject for that
+ character, and fails immediately if it cannot find it, without actually running
+ the main matching function. When callouts are in use, these optimizations can
+ cause them to be skipped. This option disables the "start-up" optimizations,
+ causing performance to suffer, but ensuring that the callouts do occur.
  .sp
    PCRE_NO_UTF8_CHECK
  .sp
-Line 1353 
 PCRE_NO_UTF8_CHECK is set, the effect of
+Line 1385 
 PCRE_NO_UTF8_CHECK is set, the effect of
  subject, or a value of \fIstartoffset\fP that does not point to the start of a
  UTF-8 character, is undefined. Your program may crash.
  .sp
-   PCRE_PARTIAL
+   PCRE_PARTIAL_HARD
+   PCRE_PARTIAL_SOFT
  .sp
- This option turns on the partial matching feature. If the subject string fails
+ These options turn on the partial matching feature. For backwards
- 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
- 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
- the failure to match occurred only because there were not enough subject
+ not enough subject characters to complete the match. If this happens when
- characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of
+ PCRE_PARTIAL_HARD is set, \fBpcre_exec()\fP immediately returns
- PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
+ PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
- may appear in the pattern. These are discussed in the
+ by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
+ returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
+ was inspected when the partial match was found is set as the first matching
+ string. There is a more detailed discussion in the
  .\" HREF
  \fBpcrepartial\fP
  .\"
-Line 1371 
 documentation.
+Line 1407 
 documentation.
  .rs
  .sp
  The subject string is passed to \fBpcre_exec()\fP as a pointer in
- \fIsubject\fP, a length in \fIlength\fP, and a starting byte offset in
+ \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
- \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of a
+ in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
- UTF-8 character. Unlike the pattern string, the subject may contain binary zero
+ a UTF-8 character. Unlike the pattern string, the subject may contain binary
- bytes. When the starting offset is zero, the search for a match starts at the
+ zero bytes. When the starting offset is zero, the search for a match starts at
- beginning of the subject, and this is by far the most common case.
+ the beginning of the subject, and this is by far the most common case.
  .P
  A non-zero starting offset is useful when searching for another match in the
  same subject by calling \fBpcre_exec()\fP again after a previous success.
-Line 1409 
 pattern. Following the usage in Jeffrey
+Line 1445 
 pattern. Following the usage in Jeffrey
  a fragment of a pattern that picks out a substring. PCRE supports several other
  kinds of parenthesized subpattern that do not cause substrings to be captured.
  .P
- Captured substrings are returned to the caller via a vector of integer offsets
+ Captured substrings are returned to the caller via a vector of integers whose
- whose address is passed in \fIovector\fP. The number of elements in the vector
+ address is passed in \fIovector\fP. The number of elements in the vector is
- is passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP:
+ passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
- this argument is NOT the size of \fIovector\fP in bytes.
+ argument is NOT the size of \fIovector\fP in bytes.
  .P
  The first two-thirds of the vector is used to pass back captured substrings,
  each substring using a pair of integers. The remaining third of the vector is
  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
- and is not available for passing back information. The length passed in
+ and is not available for passing back information. The number passed in
  \fIovecsize\fP should always be a multiple of three. If it is not, it is
  rounded down.
  .P
  When a match is successful, information about captured substrings is returned
  in pairs of integers, starting at the beginning of \fIovector\fP, and
- continuing up to two-thirds of its length at the most. The first element of a
+ continuing up to two-thirds of its length at the most. The first element of
- pair is set to the offset of the first character in a substring, and the second
+ each pair is set to the byte offset of the first character in a substring, and
- is set to the offset of the first character after the end of a substring. The
+ the second is set to the byte offset of the first character after the end of a
- first pair, \fIovector[0]\fP and \fIovector[1]\fP, identify the portion of the
+ substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
- subject string matched by the entire pattern. The next pair is used for the
+ mode. They are not character counts.
- first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP
+ .P
- is one more than the highest numbered pair that has been set. For example, if
+ The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
- two substrings have been captured, the returned value is 3. If there are no
+ portion of the subject string matched by the entire pattern. The next pair is
- capturing subpatterns, the return value from a successful match is 1,
+ used for the first capturing subpattern, and so on. The value returned by
- indicating that just the first pair of offsets has been set.
+ \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
+ For example, if two substrings have been captured, the returned value is 3. If
+ there are no capturing subpatterns, the return value from a successful match is
+, indicating that just the first pair of offsets has been set.
  .P
  If a capturing subpattern is matched repeatedly, it is the last portion of the
  string that it matched that is returned.
  .P
  If the vector is too small to hold all the captured substring offsets, it is
  used as far as possible (up to two-thirds of its length), and the function
- returns a value of zero. In particular, if the substring offsets are not of
+ returns a value of zero. If the substring offsets are not of interest,
- interest, \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
+ \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
  \fIovecsize\fP as zero. However, if the pattern contains back references and
  the \fIovector\fP is not big enough to remember the related substrings, PCRE
  has to get additional memory for use during matching. Thus it is usually
-Line 1551 
 documentation for details of partial mat
+Line 1590 
 documentation for details of partial mat
  .sp
    PCRE_ERROR_BADPARTIAL     (-13)
  .sp
- The PCRE_PARTIAL option was used with a compiled pattern containing items that
+ This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
- are not supported for partial matching. See the
+ option was used with a compiled pattern containing items that were not
- .\" HREF
+ supported for partial matching. From release 8.00 onwards, there are no
- \fBpcrepartial\fP
+ restrictions on partial matching.
- .\"
- documentation for details of partial matching.
  .sp
    PCRE_ERROR_INTERNAL       (-14)
  .sp
-Line 1726 
 These functions call \fBpcre_get_stringn
+Line 1763 
 These functions call \fBpcre_get_stringn
  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
  the behaviour may not be what you want (see the next section).
- .
+ .P
+ \fBWarning:\fP If the pattern uses the "(?|" feature to set up multiple
+ subpatterns with the same number, you cannot use names to distinguish them,
+ because names are not included in the compiled code. The matching process uses
+ only numbers.
  .
  .SH "DUPLICATE SUBPATTERN NAMES"
  .rs
-Line 1802 
 a compiled pattern, using a matching alg
+Line 1843 
 a compiled pattern, using a matching alg
  just once, and does not backtrack. This has different characteristics to the
  normal algorithm, and is not compatible with Perl. Some of the features of PCRE
  patterns are not supported. Nevertheless, there are times when this kind of
- 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
- the
+ list of features that \fBpcre_dfa_exec()\fP does not support, see the
  .\" HREF
  \fBpcrematching\fP
  .\"
-Line 1842 
 Here is an example of a simple call to \
+Line 1883 
 Here is an example of a simple call to \
  .sp
  The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
- PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,
+ PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
- 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,
- the same as for \fBpcre_exec()\fP, so their description is not repeated here.
+ and PCRE_DFA_RESTART. All but the last four of these are exactly the same as
- .sp
+ for \fBpcre_exec()\fP, so their description is not repeated here.
-   PCRE_PARTIAL
+ .sp
- .sp
+   PCRE_PARTIAL_HARD
- This has the same general effect as it does for \fBpcre_exec()\fP, but the
+   PCRE_PARTIAL_SOFT
- details are slightly different. When PCRE_PARTIAL is set for
+ .sp
- \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into
+ These have the same general effect as they do for \fBpcre_exec()\fP, but the
- PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
+ details are slightly different. When PCRE_PARTIAL_HARD is set for
- complete matches, but there is still at least one matching possibility. The
+ \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
- portion of the string that provided the partial match is set as the first
+ is reached and there is still at least one matching possibility that requires
- matching string.
+ additional characters. This happens even if some complete matches have also
+ been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
+ is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
+ there have been no complete matches, but there is still at least one matching
+ possibility. The portion of the string that was inspected when the longest
+ partial match was found is set as the first matching string in both cases.
  .sp
    PCRE_DFA_SHORTEST
  .sp
-Line 1865 
 matching point in the subject string.
+Line 1911 
 matching point in the subject string.
  .sp
    PCRE_DFA_RESTART
  .sp
- 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
- 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
- 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
- option requests this action; when it is set, the \fIworkspace\fP and
+ \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
- \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
- 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
  .\" HREF
  \fBpcrepartial\fP
  .\"
-Line 1975 
 Cambridge CB2 3QH, England.
+Line 2020 
 Cambridge CB2 3QH, England.
  .rs
  .sp
  .nf
- Last updated: 12 April 2008
+ Last updated: 11 September 2009
- Copyright (c) 1997-2008 University of Cambridge.
+ Copyright (c) 1997-2009 University of Cambridge.
  .fi

 Legend:



Removed from v.345
 


changed lines


 
Added in v.442
 Legend:



Removed from v.345
 


changed lines


 
Added in v.442
-Removed from v.345
+Added in v.442

webmaster@exim.org	ViewVC Help
Powered by ViewVC 1.1.12