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

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

Parent Directory | Revision Log | View Patch Patch

-revision 182 by ph10,
Wed Jun 13 15:09:54 2007 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
  .\"
- documentation describes how to run it.
+ documentation describes how to compile and run it.
  .P
  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 218 
 points during a matching operation. Deta
+Line 223 
 points during a matching operation. Deta
  documentation.
  .
  .
+ .\" HTML <a name="newlines"></a>
  .SH NEWLINES
  .rs
  .sp
-Line 235 
 The default default is LF, which is the
+Line 241 
 The default default is LF, which is the
  default can be overridden, either when a pattern is compiled, or when it is
  matched.
  .P
+ At compile time, the newline convention can be specified by the \fIoptions\fP
+ argument of \fBpcre_compile()\fP, or it can be specified by special text at the
+ start of the pattern itself; this overrides any other settings. See the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page for details of the special character sequences.
+ .P
  In the PCRE documentation the word "newline" is used to mean "the character or
  pair of characters that indicate a line break". The choice of newline
  convention affects the handling of the dot, circumflex, and dollar
  metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
  recognized line ending sequence, the match position advancement for a
- non-anchored pattern. The choice of newline convention does not affect the
+ non-anchored pattern. There is more detail about this in the
- interpretation of the \en or \er escape sequences.
+ .\" HTML <a href="#execoptions">
+ .\" </a>
+ section on \fBpcre_exec()\fP options
+ .\"
+ below.
+ .P
+ The choice of newline convention does not affect the interpretation of
+ the \en or \er escape sequences, nor does it affect what \eR matches, which is
+ controlled in a similar way, but by separate options.
  .
  .
  .SH MULTITHREADING
-Line 300 
 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
+ The output is an integer whose value indicates what character sequences the \eR
+ escape sequence matches by default. A value of 0 means that \eR matches any
+ Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
+ or CRLF. The default can be overridden when a pattern is compiled or matched.
  .sp
    PCRE_CONFIG_LINK_SIZE
  .sp
-Line 323 
 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 380 
 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 444 
 facility, see the
+Line 476 
 facility, see the
  .\"
  documentation.
  .sp
+   PCRE_BSR_ANYCRLF
+   PCRE_BSR_UNICODE
+ .sp
+ These options (which are mutually exclusive) control what the \eR escape
+ sequence matches. The choice is either to match only CR, LF, or CRLF, or to
+ match any Unicode newline sequence. The default is specified when PCRE is
+ built. It can be overridden from within the pattern, or by setting an option
+ when a compiled pattern is matched.
+ .sp
    PCRE_CASELESS
  .sp
  If this bit is set, letters in the pattern match both upper and lower case
-Line 516 
 If this option is set, an unanchored pat
+Line 557 
 If this option is set, an unanchored pat
  the first newline in the subject string, though the matched text may continue
  over the newline.
  .sp
+   PCRE_JAVASCRIPT_COMPAT
+ .sp
+ If this option is set, PCRE's behaviour is changed in some ways so that it is
+ compatible with JavaScript rather than Perl. The changes are as follows:
+ .P
+ (1) A lone closing square bracket in a pattern causes a compile-time error,
+ because this is illegal in JavaScript (by default it is treated as a data
+ character). Thus, the pattern AB]CD becomes illegal when this option is set.
+ .P
+ (2) At run time, a back reference to an unset subpattern group matches an empty
+ string (by default this causes the current matching alternative to fail). A
+ pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
+ an "a" in the subject), whereas it fails by default, for Perl compatibility.
+ .sp
    PCRE_MULTILINE
  .sp
  By default, PCRE treats the subject string as consisting of a single line of
-Line 601 
 page.
+Line 656 
 page.
    PCRE_NO_UTF8_CHECK
  .sp
  When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
- automatically checked. If an invalid UTF-8 sequence of bytes is found,
+ automatically checked. There is a discussion about the
- \fBpcre_compile()\fP returns an error. If you already know that your pattern is
+ .\" HTML <a href="pcre.html#utf8strings">
- valid, and you want to skip this check for performance reasons, you can set the
+ .\" </a>
- PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid
+ validity of UTF-8 strings
- UTF-8 string as a pattern is undefined. It may cause your program to crash.
+ .\"
- Note that this option can also be passed to \fBpcre_exec()\fP and
+ in the main
- \fBpcre_dfa_exec()\fP, to suppress the UTF-8 validity checking of subject
+ .\" HREF
- strings.
+ \fBpcre\fP
+ .\"
+ page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
+ returns an error. If you already know that your pattern is valid, and you want
+ to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
+ option. When it is set, the effect of passing an invalid UTF-8 string as a
+ pattern is undefined. It may cause your program to crash. Note that this option
+ can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
+ the UTF-8 validity checking of subject strings.
  .
  .
  .SH "COMPILATION ERROR CODES"
-Line 631 
 out of use. To avoid confusion, they hav
+Line 694 
 out of use. To avoid confusion, they hav
  nothing to repeat
  [this code is not in use]
  internal error: unexpected repeat
- unrecognized character after (?
+ unrecognized character after (? or (?-
  POSIX named classes are supported only within a class
  missing )
  reference to non-existent subpattern
-Line 639 
 out of use. To avoid confusion, they hav
+Line 702 
 out of use. To avoid confusion, they hav
  unknown option bit(s) set
  missing ) after comment
  [this code is not in use]
- regular expression too large
+ regular expression is too large
  failed to get memory
  unmatched parentheses
  internal error: code overflow
-Line 668 
 out of use. To avoid confusion, they hav
+Line 731 
 out of use. To avoid confusion, they hav
  malformed \eP or \ep sequence
  unknown property name after \eP or \ep
  subpattern name is too long (maximum 32 characters)
- too many named subpatterns (maximum 10,000)
+ too many named subpatterns (maximum 10000)
- repeated subpattern is too long
+ [this code is not in use]
  octal value is greater than \e377 (not in UTF-8 mode)
  internal error: overran compiling workspace
  internal error: previously-checked referenced subpattern not found
  DEFINE group contains more than one branch
  repeating a DEFINE group is not allowed
- inconsistent NEWLINE options"
+ inconsistent NEWLINE options
- \eg is not followed by a braced name or an optionally braced
+ \eg is not followed by a braced, angle-bracketed, or quoted
-         non-zero number
+         name/number or by a plain number
- (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number
+ a numbered reference must not be zero
+ (*VERB) with an argument is not supported
+ (*VERB) not recognized
+ number is too big
+ subpattern name expected
+ digit expected after (?+
+ ] is an invalid data character in JavaScript compatibility mode
+ .sp
+ The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
+ be used if the limits were changed when PCRE was built.
  .
  .
  .SH "STUDYING A PATTERN"
-Line 874 
 table indicating a fixed set of bytes fo
+Line 946 
 table indicating a fixed set of bytes fo
  string, a pointer to the table is returned. Otherwise NULL is returned. The
  fourth argument should point to an \fBunsigned char *\fP variable.
  .sp
+   PCRE_INFO_HASCRORLF
+ .sp
+ Return 1 if the pattern contains any explicit matches for CR or LF characters,
+ otherwise 0. The fourth argument should point to an \fBint\fP variable. An
+ explicit match is either a literal CR or LF character, or \er or \en.
+ .sp
    PCRE_INFO_JCHANGED
  .sp
- Return 1 if the (?J) option setting is used in the pattern, otherwise 0. The
+ Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
- fourth argument should point to an \fBint\fP variable. The (?J) internal option
+. The fourth argument should point to an \fBint\fP variable. (?J) and
- setting changes the local PCRE_DUPNAMES option.
+ (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
  .sp
    PCRE_INFO_LASTLITERAL
  .sp
-Line 934 
 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
  Return a copy of the options with which the pattern was compiled. The fourth
  argument should point to an \fBunsigned long int\fP variable. These option bits
  are those specified in the call to \fBpcre_compile()\fP, modified by any
- top-level option settings within the pattern itself.
+ top-level option settings at the start of the pattern itself. In other words,
+ they are the options that will be in force when matching starts. For example,
+ if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
+ result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
  .P
  A pattern is automatically anchored by PCRE if all of its top-level
  alternatives begin with one of the following:
-Line 1137 
 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 1158 
 called. See the
+Line 1240 
 called. See the
  .\"
  documentation for a discussion of saving compiled patterns for later use.
  .
+ .\" HTML <a name="execoptions"></a>
  .SS "Option bits for \fBpcre_exec()\fP"
  .rs
  .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 1172 
 matching position. If a pattern was comp
+Line 1257 
 matching position. If a pattern was comp
  to be anchored by virtue of its contents, it cannot be made unachored at
  matching time.
  .sp
+   PCRE_BSR_ANYCRLF
+   PCRE_BSR_UNICODE
+ .sp
+ These options (which are mutually exclusive) control what the \eR escape
+ sequence matches. The choice is either to match only CR, LF, or CRLF, or to
+ match any Unicode newline sequence. These options override the choice that was
+ made or defaulted when the pattern was compiled.
+ .sp
    PCRE_NEWLINE_CR
    PCRE_NEWLINE_LF
    PCRE_NEWLINE_CRLF
-Line 1183 
 the pattern was compiled. For details, s
+Line 1276 
 the pattern was compiled. For details, s
  \fBpcre_compile()\fP above. During matching, the newline choice affects the
  behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
  the way the match position is advanced after a match failure for an unanchored
- pattern. When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is
+ pattern.
- set, and a match attempt fails when the current position is at a CRLF sequence,
+ .P
- the match position is advanced by two characters instead of one, in other
+ When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
- words, to after the CRLF.
+ match attempt for an unanchored pattern fails when the current position is at a
+ CRLF sequence, and the pattern contains no explicit matches for CR or LF
+ characters, the match position is advanced by two characters instead of one, in
+ other words, to after the CRLF.
+ .P
+ The above rule is a compromise that makes the most common cases work as
+ expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
+ set), it does not match the string "\er\enA" because, after failing at the
+ start, it skips both the CR and the LF before retrying. However, the pattern
+ [\er\en]A does match that string, because it contains an explicit CR or LF
+ reference, and so advances only by one character after the first failure.
+ .P
+ An explicit match for CR of LF is either a literal appearance of one of those
+ characters, or one of the \er or \en escape sequences. Implicit matches such as
+ [^X] do not count, nor does \es (which includes CR and LF in the characters
+ that it matches).
+ .P
+ Notwithstanding the above, anomalous effects may still occur when CRLF is a
+ valid newline sequence and explicit \er or \en escapes appear in the pattern.
  .sp
    PCRE_NOTBOL
  .sp
-Line 1212 
 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
  When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
  string is automatically checked when \fBpcre_exec()\fP is subsequently called.
  The value of \fIstartoffset\fP is also checked to ensure that it points to the
- start of a UTF-8 character. If an invalid UTF-8 sequence of bytes is found,
+ start of a UTF-8 character. There is a discussion about the validity of UTF-8
- \fBpcre_exec()\fP returns the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP
+ strings in the
- contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
+ .\" HTML <a href="pcre.html#utf8strings">
+ .\" </a>
+ section on UTF-8 support
+ .\"
+ in the main
+ .\" HREF
+ \fBpcre\fP
+ .\"
+ page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
+ the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
+ PCRE_ERROR_BADUTF8_OFFSET is returned.
  .P
  If you already know that your subject is valid, and you want to skip these
  checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
-Line 1243 
 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 1261 
 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 1299 
 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 1441 
 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 1463 
 The internal recursion limit, as specifi
+Line 1610 
 The internal recursion limit, as specifi
  field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
  description above.
  .sp
-   PCRE_ERROR_NULLWSLIMIT    (-22)
- .sp
- When a group that can match an empty substring is repeated with an unbounded
- upper limit, the subject position at the start of the group must be remembered,
- so that a test for an empty string can be made when the end of the group is
- reached. Some workspace is required for this; if it runs out, this error is
- given.
- .sp
    PCRE_ERROR_BADNEWLINE     (-23)
  .sp
  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
  .P
- Error numbers -16 to -20 are not used by \fBpcre_exec()\fP.
+ Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
  .
  .
  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
-Line 1624 
 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 1640 
 example is shown in the
+Line 1783 
 example is shown in the
  .\" HREF
  \fBpcrepattern\fP
  .\"
- documentation. When duplicates are present, \fBpcre_copy_named_substring()\fP
+ documentation.
- and \fBpcre_get_named_substring()\fP return the first substring corresponding
+ .P
- to the given name that is set. If none are set, an empty string is returned.
+ When duplicates are present, \fBpcre_copy_named_substring()\fP and
- The \fBpcre_get_stringnumber()\fP function returns one of the numbers that are
+ \fBpcre_get_named_substring()\fP return the first substring corresponding to
- associated with the name, but it is not defined which it is.
+ the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
- .sp
+ returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
+ returns one of the numbers that are associated with the name, but it is not
+ defined which it is.
+ .P
  If you want to get full details of all captured substrings for a given name,
  you must use the \fBpcre_get_stringtable_entries()\fP function. The first
  argument is the compiled pattern, and the second is the name. The third and
-Line 1697 
 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 1737 
 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 1760 
 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 1870 
 Cambridge CB2 3QH, England.
+Line 2020 
 Cambridge CB2 3QH, England.
  .rs
  .sp
  .nf
- Last updated: 13 June 2007
+ Last updated: 11 September 2009
- Copyright (c) 1997-2007 University of Cambridge.
+ Copyright (c) 1997-2009 University of Cambridge.
  .fi

 Legend:



Removed from v.182
 


changed lines


 
Added in v.442
 Legend:



Removed from v.182
 


changed lines


 
Added in v.442
-Removed from v.182
+Added in v.442

webmaster@exim.org	ViewVC Help
Powered by ViewVC 1.1.12