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

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-revision 412 by ph10,
Sat Apr 11 10:34:37 2009 UTC
+revision 567 by ph10,
Sat Nov  6 17:10:00 2010 UTC
 Line 132 
 an application that uses PCRE. The heade
  and PCRE_MINOR to contain the major and minor release numbers for the library.
  Applications can use these to include support for different releases of PCRE.
  .P
+ In a Windows environment, if you want to statically link an application program
+ against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
+ including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
+ \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
+ \fB__declspec(dllimport)\fP, with unwanted results.
+ .P
  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 155 
 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 390 
 avoiding the use of the stack.
+Line 401 
 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 407 
 argument, which is an address (see below
+Line 420 
 argument, which is an address (see below
  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
- compatible with Perl, but also some others) can also be set and unset from
+ compatible with Perl, but some others as well) can also be set and unset from
  within the pattern (see the detailed description in the
  .\" HREF
  \fBpcrepattern\fP
  .\"
  documentation). For those options that can be different in different parts of
- the pattern, the contents of the \fIoptions\fP argument specifies their initial
+ the pattern, the contents of the \fIoptions\fP argument specifies their
- settings at the start of compilation and execution. The PCRE_ANCHORED and
+ settings at the start of compilation and execution. The PCRE_ANCHORED,
- PCRE_NEWLINE_\fIxxx\fP options can be set at the time of matching as well as at
+ PCRE_BSR_\fIxxx\fP, and PCRE_NEWLINE_\fIxxx\fP options can be set at the time
- compile 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 543 
 set, any backslash in a pattern that is
+Line 559 
 set, any backslash in a pattern that is
  special meaning causes an error, thus reserving these combinations for future
  expansion. By default, as in Perl, a backslash followed by a letter with no
  special meaning is treated as a literal. (Perl can, however, be persuaded to
- give a warning for this.) There are at present no other features controlled by
+ give an error for this, by running it with the -w option.) There are at present
- this option. It can also be set by a (?X) option setting within a pattern.
+ no other features controlled by this option. It can also be set by a (?X)
+ option setting within a pattern.
  .sp
    PCRE_FIRSTLINE
  .sp
-Line 625 
 were followed by ?: but named parenthese
+Line 642 
 were followed by ?: but named parenthese
  they acquire numbers in the usual way). There is no equivalent of this option
  in Perl.
  .sp
+   PCRE_UCP
+ .sp
+ This option changes the way PCRE processes \eb, \ed, \es, \ew, and some of the
+ POSIX character classes. By default, only ASCII characters are recognized, but
+ if PCRE_UCP is set, Unicode properties are used instead to classify characters.
+ More details are given in the section on
+ .\" HTML <a href="pcre.html#genericchartypes">
+ .\" </a>
+ generic character types
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page. If you set PCRE_UCP, matching one of the items it affects takes much
+ longer. The option is available only if PCRE has been compiled with Unicode
+ property support.
+ .sp
    PCRE_UNGREEDY
  .sp
  This option inverts the "greediness" of the quantifiers so that they are not
-Line 730 
 out of use. To avoid confusion, they hav
+Line 765 
 out of use. To avoid confusion, they hav
  [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
+ 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
  \eg is not followed by a braced, angle-bracketed, or quoted
          name/number or by a plain number
  a numbered reference must not be zero
- (*VERB) with an argument is not supported
+ an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
  (*VERB) not recognized
  number is too big
  subpattern name expected
  digit expected after (?+
  ] is an invalid data character in JavaScript compatibility mode
+ different names for subpatterns of the same number are
+         not allowed
+ (*MARK) must have an argument
+ this version of PCRE is not compiled with PCRE_UCP support
  .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.
-Line 764 
 help speed up matching, \fBpcre_study()\
+Line 804 
 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 796 
 This is a typical call to \fBpcre_study\
+Line 836 
 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.
+ .P
+ The two optimizations just described can be disabled by setting the
+ PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
+ \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
+ callouts, or make use of (*MARK), and you make use of these in cases where
+ matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
+ .\" HTML <a href="#execoptions">
+ .\" </a>
+ below.
+ .\"
  .
  .
  .\" HTML <a name="localesupport"></a>
-Line 808 
 bytes is created.
+Line 867 
 bytes is created.
  PCRE handles caseless matching, and determines whether characters are letters,
  digits, or whatever, by reference to a set of tables, indexed by character
  value. When running in UTF-8 mode, this applies only to characters with codes
- less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
+ less than 128. By default, higher-valued codes never match escapes such as \ew
- can be tested with \ep if PCRE is built with Unicode character property
+ or \ed, but they can be tested with \ep if PCRE is built with Unicode character
- support. The use of locales with Unicode is discouraged. If you are handling
+ property support. Alternatively, the PCRE_UCP option can be set at compile
- characters with codes greater than 128, you should either use UTF-8 and
+ time; this causes \ew and friends to use Unicode property support instead of
- Unicode, or use locales, but not try to mix the two.
+ built-in tables. The use of locales with Unicode is discouraged. If you are
+ handling characters with codes greater than 128, you should either use UTF-8
+ and Unicode, or use locales, but not try to mix the two.
  .P
  PCRE contains an internal set of tables that are used when the final argument
  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
-Line 963 
 follows something of variable length. Fo
+Line 1024 
 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 983 
 entry; both of these return an \fBint\fP
+Line 1054 
 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 1007 
 different for each compiled pattern.
+Line 1095 
 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 1050 
 variable.
+Line 1139 
 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 1112 
 is different. (This seems a highly unlik
+Line 1202 
 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 1162 
 fields (not necessarily in this order):
+Line 1252 
 fields (not necessarily in this order):
    unsigned long int \fImatch_limit_recursion\fP;
    void *\fIcallout_data\fP;
    const unsigned char *\fItables\fP;
+   unsigned char **\fImark\fP;
  .sp
  The \fIflags\fP field is a bitmap that specifies which of the other fields
  are set. The flag bits are:
-Line 1171 
 are set. The flag bits are:
+Line 1262 
 are set. The flag bits are:
    PCRE_EXTRA_MATCH_LIMIT_RECURSION
    PCRE_EXTRA_CALLOUT_DATA
    PCRE_EXTRA_TABLES
+   PCRE_EXTRA_MARK
  .sp
  Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
-Line 1180 
 the block by setting the other fields an
+Line 1272 
 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 1213 
 with a \fBpcre_extra\fP block in which \
+Line 1305 
 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 1233 
 called. See the
+Line 1325 
 called. See the
  \fBpcreprecompile\fP
  .\"
  documentation for a discussion of saving compiled patterns for later use.
+ .P
+ If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
+ be set to point to a \fBchar *\fP variable. If the pattern contains any
+ backtracking control verbs such as (*MARK:NAME), and the execution ends up with
+ a name to pass back, a pointer to the name string (zero terminated) is placed
+ in the variable pointed to by the \fImark\fP field. The names are within the
+ compiled pattern; if you wish to retain such a name you must copy it before
+ freeing the memory of a compiled pattern. If there is no name to pass back, the
+ variable pointed to by the \fImark\fP field set to NULL. For details of the
+ backtracking control verbs, see the section entitled
+ .\" HTML <a href="pcrepattern#backtrackcontrol">
+ .\" </a>
+ "Backtracking control"
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ documentation.
+ .
  .
  .\" HTML <a name="execoptions"></a>
  .SS "Option bits for \fBpcre_exec()\fP"
-Line 1240 
 documentation for a discussion of saving
+Line 1352 
 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_START_OPTIMIZE,
+ PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
- PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
+ PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
+ PCRE_PARTIAL_HARD.
  .sp
    PCRE_ANCHORED
  .sp
-Line 1316 
 match the empty string, the entire match
+Line 1429 
 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. In the most general case, you have to check to see if the
+ newline convention recognizes CRLF as a newline, and if so, and the current
+ character is CR followed by LF, advance the starting offset by two characters
+ instead of one.
  .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
+ a match, in order to speed up the process. For example, if it is known that an
- match must start with a specific character, it searches the subject for that
+ unanchored match must start with a specific character, it searches the subject
- character, and fails immediately if it cannot find it, without actually running
+ for that character, and fails immediately if it cannot find it, without
- the main matching function. When callouts are in use, these optimizations can
+ actually running the main matching function. This means that a special item
- cause them to be skipped. This option disables the "start-up" optimizations,
+ such as (*COMMIT) at the start of a pattern is not considered until after a
- causing performance to suffer, but ensuring that the callouts do occur.
+ suitable starting point for the match has been found. When callouts or (*MARK)
+ items are in use, these "start-up" optimizations can cause them to be skipped
+ if the pattern is never actually used. The start-up optimizations are in effect
+ a pre-scan of the subject that takes place before the pattern is run.
+ .P
+ The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
+ causing performance to suffer, but ensuring that in cases where the result is
+ "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
+ are considered at every possible starting position in the subject string.
+ Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
+ Consider the pattern
+ .sp
+   (*COMMIT)ABC
+ .sp
+ When this is compiled, PCRE records the fact that a match must start with the
+ character "A". Suppose the subject string is "DEFABC". The start-up
+ optimization scans along the subject, finds "A" and runs the first match
+ attempt from there. The (*COMMIT) item means that the pattern must match the
+ current starting position, which in this case, it does. However, if the same
+ match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
+ subject string does not happen. The first match attempt is run starting from
+ "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
+ the overall result is "no match". If the pattern is studied, more start-up
+ optimizations may be used. For example, a minimum length for the subject may be
+ recorded. Consider the pattern
+ .sp
+   (*MARK:A)(X|Y)
+ .sp
+ The minimum length for a match is one character. If the subject is "ABC", there
+ will be attempts to match "ABC", "BC", "C", and then finally an empty string.
+ If the pattern is studied, the final attempt does not take place, because PCRE
+ knows that the subject is too short, and so the (*MARK) is never encountered.
+ In this case, studying the pattern does not affect the overall match result,
+ which is still "no match", but it does affect the auxiliary information that is
+ returned.
  .sp
    PCRE_NO_UTF8_CHECK
  .sp
-Line 1354 
 in the main
+Line 1515 
 in the main
  \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,
+ the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains a value that does
+ not point to the start of a UTF-8 character (or to the end of the subject),
  PCRE_ERROR_BADUTF8_OFFSET is returned.
  .P
  If you already know that your subject is valid, and you want to skip these
-Line 1362 
 checks for performance reasons, you can
+Line 1524 
 checks for performance reasons, you can
  calling \fBpcre_exec()\fP. You might want to do this for the second and
  subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
  all the matches in a single subject string. However, you should be sure that
- the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
+ the value of \fIstartoffset\fP points to the start of a UTF-8 character (or the
- PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
+ end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
- subject, or a value of \fIstartoffset\fP that does not point to the start of a
+ invalid UTF-8 string as a subject or an invalid value of \fIstartoffset\fP is
- UTF-8 character, is undefined. Your program may crash.
+ undefined. Your program may crash.
  .sp
-   PCRE_PARTIAL
+   PCRE_PARTIAL_HARD
- .sp
+   PCRE_PARTIAL_SOFT
- This option turns on the partial matching feature. If the subject string fails
+ .sp
- to match the pattern, but at some point during the matching process the end of
+ These options turn on the partial matching feature. For backwards
- the subject was reached (that is, the subject partially matches the pattern and
+ compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
- the failure to match occurred only because there were not enough subject
+ occurs if the end of the subject string is reached successfully, but there are
- characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of
+ not enough subject characters to complete the match. If this happens when
- PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
+ PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
- may appear in the pattern. These are discussed in the
+ testing any remaining alternatives. Only if no complete match can be found is
+ PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
+ PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
+ but only if no complete match can be found.
+ .P
+ If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
+ partial match is found, \fBpcre_exec()\fP immediately returns
+ PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
+ when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
+ important that an alternative complete match.
+ .P
+ In both cases, 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 of partial and multi-segment matching, with examples, in the
  .\" HREF
  \fBpcrepartial\fP
  .\"
  documentation.
  .
+ .
  .SS "The string to be matched by \fBpcre_exec()\fP"
  .rs
  .sp
  The subject string is passed to \fBpcre_exec()\fP as a pointer in
  \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
- in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
+ in \fIstartoffset\fP. If this is negative or greater than the length of the
- a UTF-8 character. Unlike the pattern string, the subject may contain binary
+ subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET.
- zero bytes. When the starting offset is zero, the search for a match starts at
+ .P
- the beginning of the subject, and this is by far the most common case.
+ In UTF-8 mode, the byte offset must point to the start of a UTF-8 character (or
+ the end of the subject). Unlike the pattern string, the subject may contain
+ binary zero bytes. When the starting offset is zero, the search for a match
+ starts at 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 
 start of the subject, which is deemed to
+Line 1589 
 start of the subject, which is deemed to
  set to 4, it finds the second occurrence of "iss" because it is able to look
  behind the starting point to discover that it is preceded by a letter.
  .P
+ Finding all the matches in a subject is tricky when the pattern can match an
+ empty string. It is possible to emulate Perl's /g behaviour by first trying the
+ match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
+ PCRE_ANCHORED options, and then if that fails, advancing the starting offset
+ and trying an ordinary match again. There is some code that demonstrates how to
+ do this in the
+ .\" HREF
+ \fBpcredemo\fP
+ .\"
+ sample program. In the most general case, you have to check to see if the
+ newline convention recognizes CRLF as a newline, and if so, and the current
+ character is CR followed by LF, advance the starting offset by two characters
+ instead of one.
+ .P
  If a non-zero starting offset is passed when the pattern is anchored, one
  attempt to match at the given offset is made. This can only succeed if the
  pattern does not require the match to be at the start of the subject.
  .
+ .
  .SS "How \fBpcre_exec()\fP returns captured substrings"
  .rs
  .sp
-Line 1463 
 the \fIovector\fP is not big enough to r
+Line 1658 
 the \fIovector\fP is not big enough to r
  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 1527 
 If a pattern contains back references, b
+Line 1722 
 If a pattern contains back references, b
  gets a block of memory at the start of matching to use for this purpose. If the
  call via \fBpcre_malloc()\fP fails, this error is given. The memory is
  automatically freed at the end of matching.
+ .P
+ This error is also given if \fBpcre_stack_malloc()\fP fails in
+ \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
+ \fB--disable-stack-for-recursion\fP.
  .sp
    PCRE_ERROR_NOSUBSTRING    (-7)
  .sp
-Line 1568 
 documentation for details of partial mat
+Line 1767 
 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 1593 
 description above.
+Line 1790 
 description above.
    PCRE_ERROR_BADNEWLINE     (-23)
  .sp
  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
+ .sp
+   PCRE_ERROR_BADOFFSET      (-24)
+ .sp
+ The value of \fIstartoffset\fP was negative or greater than the length of the
+ subject, that is, the value in \fIlength\fP.
  .P
  Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
  .
-Line 1744 
 then call \fBpcre_copy_substring()\fP or
+Line 1946 
 then call \fBpcre_copy_substring()\fP or
  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
+ \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
- subpatterns with the same number, you cannot use names to distinguish them,
+ subpatterns with the same number, as described in the
- because names are not included in the compiled code. The matching process uses
+ .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
- only numbers.
+ .\" </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 1757 
 only numbers.
+Line 1969 
 only numbers.
  .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 1823 
 a compiled pattern, using a matching alg
+Line 2038 
 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 1863 
 Here is an example of a simple call to \
+Line 2078 
 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_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
- the same as for \fBpcre_exec()\fP, so their description is not repeated here.
+ PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
- .sp
+ All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
-   PCRE_PARTIAL
+ so their description is not repeated here.
  .sp
- This has the same general effect as it does for \fBpcre_exec()\fP, but the
+   PCRE_PARTIAL_HARD
- details are slightly different. When PCRE_PARTIAL is set for
+   PCRE_PARTIAL_SOFT
- \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into
+ .sp
- PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
+ These have the same general effect as they do for \fBpcre_exec()\fP, but the
- complete matches, but there is still at least one matching possibility. The
+ details are slightly different. When PCRE_PARTIAL_HARD is set for
- portion of the string that provided the partial match is set as the first
+ \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
- matching string.
+ is reached and there is still at least one matching possibility that requires
+ 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.
+ There is a more detailed discussion of partial and multi-segment matching, with
+ examples, in the
+ .\" HREF
+ \fBpcrepartial\fP
+ .\"
+ documentation.
  .sp
    PCRE_DFA_SHORTEST
  .sp
-Line 1886 
 matching point in the subject string.
+Line 2113 
 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 1996 
 Cambridge CB2 3QH, England.
+Line 2222 
 Cambridge CB2 3QH, England.
  .rs
  .sp
  .nf
- Last updated: 11 April 2009
+ Last updated: 06 November 2010
- Copyright (c) 1997-2009 University of Cambridge.
+ Copyright (c) 1997-2010 University of Cambridge.
  .fi

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