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

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

Parent Directory | Revision Log | View Patch Patch

-revision 230 by ph10,
Mon Sep 10 13:23:56 2007 UTC
+revision 461 by ph10,
Mon Oct  5 10:59:35 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 254 
 non-anchored pattern. There is more deta
+Line 259 
 non-anchored pattern. There is more deta
  .\" </a>
  section on \fBpcre_exec()\fP options
  .\"
- below. The choice of newline convention does not affect the interpretation of
+ below.
- the \en or \er escape sequences.
+ .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 314 
 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 337 
 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 378 
 avoiding the use of the stack.
+Line 395 
 avoiding the use of the stack.
  Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
  called to compile a pattern into an internal form. The only difference between
  the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
- \fIerrorcodeptr\fP, via which a numerical error code can be returned.
+ \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
+ too much repetition, we refer just to \fBpcre_compile()\fP below, but the
+ information applies equally to \fBpcre_compile2()\fP.
  .P
  The pattern is a C string terminated by a binary zero, and is passed in the
  \fIpattern\fP argument. A pointer to a single block of memory that is obtained
-Line 394 
 argument, which is an address (see below
+Line 413 
 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 some others as well) 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
- 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,
- matching as well as at compile time.
+ PCRE_BSR_\fIxxx\fP, and 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
  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
  error message. This is a static string that is part of the library. You must
- 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
- where the error was discovered is placed in the variable pointed to by
+ character that was being processed when the error was discovered is placed in
- \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,
+ an immediate error is given. Some errors are not detected until checks are
+ carried out when the whole pattern has been scanned; in this case the offset is
+ set to the end of the pattern.
  .P
  If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
  \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
-Line 458 
 facility, see the
+Line 481 
 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 530 
 If this option is set, an unanchored pat
+Line 562 
 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 653 
 out of use. To avoid confusion, they hav
+Line 699 
 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 661 
 out of use. To avoid confusion, they hav
+Line 707 
 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 690 
 out of use. To avoid confusion, they hav
+Line 736 
 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)
  [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 719 
 help speed up matching, \fBpcre_study()\
+Line 774 
 help speed up matching, \fBpcre_study()\
  results of the study.
  .P
  The returned value from \fBpcre_study()\fP can be passed directly to
- \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
- 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
- described
+ passed; these are described
  .\" HTML <a href="#extradata">
  .\" </a>
  below
  .\"
  in the section on matching a pattern.
  .P
- If studying the pattern does not produce any additional information
+ If studying the pattern does not produce any useful information,
  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
- 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
- own \fBpcre_extra\fP block.
+ \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
  .P
  The second argument of \fBpcre_study()\fP contains option bits. At present, no
  options are defined, and this argument should always be zero.
-Line 751 
 This is a typical call to \fBpcre_study\
+Line 806 
 This is a typical call to \fBpcre_study\
 ,              /* no options exist */
      &error);        /* set to NULL or points to a message */
  .sp
- 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
- 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
- bytes is created.
+ mean that there are any strings of that length that match, but it does
+ guarantee that no shorter strings match. The value is used by
+ \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
+ match strings that are shorter than the lower bound. You can find out the value
+ in a calling program via the \fBpcre_fullinfo()\fP function.
+ .P
+ Studying a pattern is also useful for non-anchored patterns that do not have a
+ single fixed starting character. A bitmap of possible starting bytes is
+ created. This speeds up finding a position in the subject at which to start
+ matching.
  .
  .
  .\" HTML <a name="localesupport"></a>
-Line 899 
 fourth argument should point to an \fBun
+Line 963 
 fourth argument should point to an \fBun
    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.
+ 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 917 
 follows something of variable length. Fo
+Line 982 
 follows something of variable length. Fo
  /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
  is -1.
  .sp
+   PCRE_INFO_MINLENGTH
+ .sp
+ If the pattern was studied and a minimum length for matching subject strings
+ was computed, its value is returned. Otherwise the returned value is -1. The
+ value is a number of characters, not bytes (this may be relevant in UTF-8
+ mode). The fourth argument should point to an \fBint\fP variable. A
+ non-negative value is a lower bound to the length of any matching string. There
+ may not be any strings of that length that do actually match, but every string
+ that does match is at least that long.
+ .sp
    PCRE_INFO_NAMECOUNT
    PCRE_INFO_NAMEENTRYSIZE
    PCRE_INFO_NAMETABLE
-Line 937 
 entry; both of these return an \fBint\fP
+Line 1012 
 entry; both of these return an \fBint\fP
  length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
  entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
  are the number of the capturing parenthesis, most significant byte first. The
- rest of the entry is the corresponding name, zero terminated. The names are in
+ rest of the entry is the corresponding name, zero terminated.
- alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
+ .P
- their parentheses numbers. For example, consider the following pattern (assume
+ The names are in alphabetical order. Duplicate names may appear if (?| is used
- PCRE_EXTENDED is set, so white space - including newlines - is ignored):
+ to create multiple groups with the same number, as described in the
+ .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
+ .\" </a>
+ section on duplicate subpattern numbers
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page. Duplicate names for subpatterns with different numbers are permitted only
+ if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
+ table in the order in which they were found in the pattern. In the absence of
+ (?| this is the order of increasing number; when (?| is used this is not
+ necessarily the case because later subpatterns may have lower numbers.
+ .P
+ As a simple example of the name/number table, consider the following pattern
+ (assume PCRE_EXTENDED is set, so white space - including newlines - is
+ ignored):
  .sp
  .\" JOIN
    (?<date> (?<year>(\ed\ed)?\ed\ed) -
-Line 961 
 different for each compiled pattern.
+Line 1053 
 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 1004 
 variable.
+Line 1097 
 variable.
  Return the size of the data block pointed to by the \fIstudy_data\fP field in
  a \fBpcre_extra\fP block. That is, it is the value that was passed to
  \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
- 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
+ study data, zero is returned. The fourth argument should point to a
  \fBsize_t\fP variable.
  .
  .
-Line 1066 
 is different. (This seems a highly unlik
+Line 1160 
 is different. (This seems a highly unlik
  .P
  The function \fBpcre_exec()\fP is called to match a subject string against a
  compiled pattern, which is passed in the \fIcode\fP argument. If the
- 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
  \fIextra\fP argument. This function is the main matching facility of the
  library, and it operates in a Perl-like manner. For specialist use there is
  also an alternative matching function, which is described
-Line 1134 
 the block by setting the other fields an
+Line 1228 
 the block by setting the other fields an
  The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
  vast amount of resources when running patterns that are not going to match,
  but which have a very large number of possibilities in their search trees. The
- classic example is the use of nested unlimited repeats.
+ classic example is a pattern that uses nested unlimited repeats.
  .P
  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
  (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
-Line 1167 
 with a \fBpcre_extra\fP block in which \
+Line 1261 
 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 1194 
 documentation for a discussion of saving
+Line 1288 
 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 1203 
 matching position. If a pattern was comp
+Line 1299 
 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 1229 
 start, it skips both the CR and the LF b
+Line 1333 
 start, it skips both the CR and the LF b
  [\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
-Line 1261 
 match the empty string, the entire match
+Line 1365 
 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 1302 
 PCRE_NO_UTF8_CHECK is set, the effect of
+Line 1427 
 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 1320 
 documentation.
+Line 1449 
 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 1358 
 pattern. Following the usage in Jeffrey
+Line 1487 
 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
  advisable to supply an \fIovector\fP.
  .P
- The \fBpcre_info()\fP function can be used to find out how many capturing
+ The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
  subpatterns there are in a compiled pattern. The smallest size for
  \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
  the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
-Line 1500 
 documentation for details of partial mat
+Line 1632 
 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 1675 
 These functions call \fBpcre_get_stringn
+Line 1805 
 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, as described in the
+ .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
+ .\" </a>
+ section on duplicate subpattern numbers
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page, you cannot use names to distinguish the different subpatterns, because
+ names are not included in the compiled code. The matching process uses only
+ numbers. For this reason, the use of different names for subpatterns of the
+ same number causes an error at compile time.
  .
  .SH "DUPLICATE SUBPATTERN NAMES"
  .rs
-Line 1685 
 the behaviour may not be what you want (
+Line 1829 
 the behaviour may not be what you want (
  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
  .PP
  When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
- are not required to be unique. Normally, patterns with duplicate names are such
+ are not required to be unique. (Duplicate names are always allowed for
- that in any one match, only one of the named subpatterns participates. An
+ subpatterns with the same number, created by using the (?| feature. Indeed, if
- example is shown in the
+ such subpatterns are named, they are required to use the same names.)
+ .P
+ Normally, patterns with duplicate names are such that in any one match, only
+ one of the named subpatterns participates. An example is shown in the
  .\" HREF
  \fBpcrepattern\fP
  .\"
-Line 1751 
 a compiled pattern, using a matching alg
+Line 1898 
 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 1791 
 Here is an example of a simple call to \
+Line 1938 
 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 1814 
 matching point in the subject string.
+Line 1966 
 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 1924 
 Cambridge CB2 3QH, England.
+Line 2075 
 Cambridge CB2 3QH, England.
  .rs
  .sp
  .nf
- Last updated: 10 September 2007
+ Last updated: 03 October 2009
- Copyright (c) 1997-2007 University of Cambridge.
+ Copyright (c) 1997-2009 University of Cambridge.
  .fi

 Legend:



Removed from v.230
 


changed lines


 
Added in v.461
 Legend:



Removed from v.230
 


changed lines


 
Added in v.461
-Removed from v.230
+Added in v.461

webmaster@exim.org	ViewVC Help
Powered by ViewVC 1.1.12