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

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

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-revision 65 by nigel,
Sat Feb 24 21:40:08 2007 UTC
+revision 77 by nigel,
Sat Feb 24 21:40:45 2007 UTC
 Line 3
  <title>pcreapi specification</title>
  </head>
  <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
- This HTML document has been generated automatically from the original man page.
+ <h1>pcreapi man page</h1>
- If there is any nonsense in it, please consult the man page, in case the
+ <p>
- conversion went wrong.<br>
+ Return to the <a href="index.html">PCRE index page</a>.
+ </p>
+ <p>
+ This page is part of the PCRE HTML documentation. It was generated automatically
+ from the original man page. If there is any nonsense in it, please consult the
+ man page, in case the conversion went wrong.
+ <br>
  <ul>
- <li><a name="TOC1" href="#SEC1">SYNOPSIS OF PCRE API</a>
+ <li><a name="TOC1" href="#SEC1">PCRE NATIVE API</a>
- <li><a name="TOC2" href="#SEC2">PCRE API</a>
+ <li><a name="TOC2" href="#SEC2">PCRE API OVERVIEW</a>
  <li><a name="TOC3" href="#SEC3">MULTITHREADING</a>
- <li><a name="TOC4" href="#SEC4">CHECKING BUILD-TIME OPTIONS</a>
+ <li><a name="TOC4" href="#SEC4">SAVING PRECOMPILED PATTERNS FOR LATER USE</a>
- <li><a name="TOC5" href="#SEC5">COMPILING A PATTERN</a>
+ <li><a name="TOC5" href="#SEC5">CHECKING BUILD-TIME OPTIONS</a>
- <li><a name="TOC6" href="#SEC6">STUDYING A PATTERN</a>
+ <li><a name="TOC6" href="#SEC6">COMPILING A PATTERN</a>
- <li><a name="TOC7" href="#SEC7">LOCALE SUPPORT</a>
+ <li><a name="TOC7" href="#SEC7">COMPILATION ERROR CODES</a>
- <li><a name="TOC8" href="#SEC8">INFORMATION ABOUT A PATTERN</a>
+ <li><a name="TOC8" href="#SEC8">STUDYING A PATTERN</a>
- <li><a name="TOC9" href="#SEC9">OBSOLETE INFO FUNCTION</a>
+ <li><a name="TOC9" href="#SEC9">LOCALE SUPPORT</a>
- <li><a name="TOC10" href="#SEC10">MATCHING A PATTERN</a>
+ <li><a name="TOC10" href="#SEC10">INFORMATION ABOUT A PATTERN</a>
- <li><a name="TOC11" href="#SEC11">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a>
+ <li><a name="TOC11" href="#SEC11">OBSOLETE INFO FUNCTION</a>
- <li><a name="TOC12" href="#SEC12">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a>
+ <li><a name="TOC12" href="#SEC12">REFERENCE COUNTS</a>
+ <li><a name="TOC13" href="#SEC13">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a>
+ <li><a name="TOC14" href="#SEC14">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a>
+ <li><a name="TOC15" href="#SEC15">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a>
+ <li><a name="TOC16" href="#SEC16">FINDING ALL POSSIBLE MATCHES</a>
+ <li><a name="TOC17" href="#SEC17">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a>
  </ul>
- <br><a name="SEC1" href="#TOC1">SYNOPSIS OF PCRE API</a><br>
+ <br><a name="SEC1" href="#TOC1">PCRE NATIVE API</a><br>
  <P>
  <b>#include &#60;pcre.h&#62;</b>
  </P>
-Line 30 
 conversion went wrong.
+Line 41 
 conversion went wrong.
  <b>const unsigned char *<i>tableptr</i>);</b>
  </P>
  <P>
+ <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
+ <b>int *<i>errorcodeptr</i>,</b>
+ <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
+ <b>const unsigned char *<i>tableptr</i>);</b>
+ </P>
+ <P>
  <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
  <b>const char **<i>errptr</i>);</b>
  </P>
-Line 39 
 conversion went wrong.
+Line 56 
 conversion went wrong.
  <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b>
  </P>
  <P>
+ <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
+ <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
+ <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
+ <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
+ </P>
+ <P>
  <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
  <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
  <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
-Line 86 
 conversion went wrong.
+Line 109 
 conversion went wrong.
  <b>*<i>firstcharptr</i>);</b>
  </P>
  <P>
+ <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
+ </P>
+ <P>
  <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
  </P>
  <P>
-Line 98 
 conversion went wrong.
+Line 124 
 conversion went wrong.
  <b>void (*pcre_free)(void *);</b>
  </P>
  <P>
- <b>int (*pcre_callout)(pcre_callout_block *);</b>
+ <b>void *(*pcre_stack_malloc)(size_t);</b>
  </P>
- <br><a name="SEC2" href="#TOC1">PCRE API</a><br>
  <P>
- PCRE has its own native API, which is described in this document. There is also
+ <b>void (*pcre_stack_free)(void *);</b>
- a set of wrapper functions that correspond to the POSIX regular expression API.
- These are described in the <b>pcreposix</b> documentation.
  </P>
  <P>
- The native API function prototypes are defined in the header file <b>pcre.h</b>,
+ <b>int (*pcre_callout)(pcre_callout_block *);</b>
- and on Unix systems the library itself is called <b>libpcre.a</b>, so can be
- accessed by adding <b>-lpcre</b> to the command for linking an application which
- calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to
- contain the major and minor release numbers for the library. Applications can
- use these to include support for different releases.
  </P>
+ <br><a name="SEC2" href="#TOC1">PCRE API OVERVIEW</a><br>
  <P>
- The functions <b>pcre_compile()</b>, <b>pcre_study()</b>, and <b>pcre_exec()</b>
+ PCRE has its own native API, which is described in this document. There is
- are used for compiling and matching regular expressions. A sample program that
+ also a set of wrapper functions that correspond to the POSIX regular expression
- demonstrates the simplest way of using them is given in the file
+ API. These are described in the
- <i>pcredemo.c</i>. The <b>pcresample</b> documentation describes how to run it.
+ <a href="pcreposix.html"><b>pcreposix</b></a>
+ documentation. Both of these APIs define a set of C function calls. A C++
+ wrapper is distributed with PCRE. It is documented in the
+ <a href="pcrecpp.html"><b>pcrecpp</b></a>
+ page.
  </P>
  <P>
- There are convenience functions for extracting captured substrings from a
+ The native API C function prototypes are defined in the header file
- matched subject string. They are:
+ <b>pcre.h</b>, and on Unix systems the library itself is called <b>libpcre</b>.
+ It can normally be accessed by adding <b>-lpcre</b> to the command for linking
+ an application that uses PCRE. The header file defines the macros PCRE_MAJOR
+ 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>
+ <P>
+ The functions <b>pcre_compile()</b>, <b>pcre_compile2()</b>, <b>pcre_study()</b>,
+ and <b>pcre_exec()</b> 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 <i>pcredemo.c</i> in the source
+ distribution. The
+ <a href="pcresample.html"><b>pcresample</b></a>
+ documentation describes how to run it.
+ </P>
+ <P>
+ A second matching function, <b>pcre_dfa_exec()</b>, which is not
+ Perl-compatible, is also provided. This uses a different algorithm for the
+ matching. This allows it to find all possible matches (at a given point in the
+ subject), not just one. However, this algorithm does not return captured
+ substrings. A description of the two matching algorithms and their advantages
+ and disadvantages is given in the
+ <a href="pcrematching.html"><b>pcrematching</b></a>
+ documentation.
  </P>
  <P>
+ In addition to the main compiling and matching functions, there are convenience
+ functions for extracting captured substrings from a subject string that is
+ matched by <b>pcre_exec()</b>. They are:
  <pre>
    <b>pcre_copy_substring()</b>
    <b>pcre_copy_named_substring()</b>
    <b>pcre_get_substring()</b>
    <b>pcre_get_named_substring()</b>
    <b>pcre_get_substring_list()</b>
- </PRE>
+   <b>pcre_get_stringnumber()</b>
- </P>
+ </pre>
- <P>
  <b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also
  provided, to free the memory used for extracted strings.
  </P>
  <P>
- The function <b>pcre_maketables()</b> is used (optionally) to build a set of
+ The function <b>pcre_maketables()</b> is used to build a set of character tables
- character tables in the current locale for passing to <b>pcre_compile()</b>.
+ in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>,
+ or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for
+ specialist use. Most commonly, no special tables are passed, in which case
+ internal tables that are generated when PCRE is built are used.
  </P>
  <P>
  The function <b>pcre_fullinfo()</b> is used to find out information about a
- compiled pattern; <b>pcre_info()</b> is an obsolete version which returns only
+ compiled pattern; <b>pcre_info()</b> is an obsolete version that returns only
  some of the available information, but is retained for backwards compatibility.
  The function <b>pcre_version()</b> returns a pointer to a string containing the
  version of PCRE and its date of release.
  </P>
  <P>
+ The function <b>pcre_refcount()</b> maintains a reference count in a data block
+ containing a compiled pattern. This is provided for the benefit of
+ object-oriented applications.
+ </P>
+ <P>
  The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain
- the entry points of the standard <b>malloc()</b> and <b>free()</b> functions
+ the entry points of the standard <b>malloc()</b> and <b>free()</b> functions,
  respectively. PCRE calls the memory management functions via these variables,
  so a calling program can replace them if it wishes to intercept the calls. This
  should be done before calling any PCRE functions.
  </P>
  <P>
+ The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also
+ indirections to memory management functions. These special functions are used
+ only when PCRE is compiled to use the heap for remembering data, instead of
+ recursive function calls, when running the <b>pcre_exec()</b> function. This is
+ a non-standard way of building PCRE, for use in environments that have limited
+ stacks. Because of the greater use of memory management, it runs more slowly.
+ Separate functions are provided so that special-purpose external code can be
+ used for this case. When used, these functions are always called in a
+ stack-like manner (last obtained, first freed), and always for memory blocks of
+ the same size.
+ </P>
+ <P>
  The global variable <b>pcre_callout</b> initially contains NULL. It can be set
  by the caller to a "callout" function, which PCRE will then call at specified
- points during a matching operation. Details are given in the <b>pcrecallout</b>
+ points during a matching operation. Details are given in the
+ <a href="pcrecallout.html"><b>pcrecallout</b></a>
  documentation.
  </P>
  <br><a name="SEC3" href="#TOC1">MULTITHREADING</a><br>
  <P>
  The PCRE functions can be used in multi-threading applications, with the
- proviso that the memory management functions pointed to by <b>pcre_malloc</b>
+ proviso that the memory management functions pointed to by <b>pcre_malloc</b>,
- and <b>pcre_free</b>, and the callout function pointed to by <b>pcre_callout</b>,
+ <b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the
- are shared by all threads.
+ callout function pointed to by <b>pcre_callout</b>, are shared by all threads.
  </P>
  <P>
  The compiled form of a regular expression is not altered during matching, so
  the same compiled pattern can safely be used by several threads at once.
  </P>
- <br><a name="SEC4" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
+ <br><a name="SEC4" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br>
+ <P>
+ The compiled form of a regular expression can be saved and re-used at a later
+ time, possibly by a different program, and even on a host other than the one on
+ which it was compiled. Details are given in the
+ <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
+ documentation.
+ </P>
+ <br><a name="SEC5" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
  <P>
  <b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b>
  </P>
-Line 186 
 documentation has more details about the
+Line 263 
 documentation has more details about the
  The first argument for <b>pcre_config()</b> is an integer, specifying which
  information is required; the second argument is a pointer to a variable into
  which the information is placed. The following information is available:
- </P>
- <P>
  <pre>
    PCRE_CONFIG_UTF8
- </PRE>
+ </pre>
- </P>
- <P>
  The output is an integer that is set to one if UTF-8 support is available;
  otherwise it is set to zero.
- </P>
+ <pre>
- <P>
+   PCRE_CONFIG_UNICODE_PROPERTIES
+ </pre>
+ The output is an integer that is set to one if support for Unicode character
+ properties is available; otherwise it is set to zero.
  <pre>
    PCRE_CONFIG_NEWLINE
- </PRE>
+ </pre>
- </P>
- <P>
  The output is an integer that is set to the value of the code that is used for
  the newline character. It is either linefeed (10) or carriage return (13), and
  should normally be the standard character for your operating system.
- </P>
- <P>
  <pre>
    PCRE_CONFIG_LINK_SIZE
- </PRE>
+ </pre>
- </P>
- <P>
  The output is an integer that contains the number of bytes used for internal
  linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
  allow larger regular expressions to be compiled, at the expense of slower
  matching. The default value of 2 is sufficient for all but the most massive
  patterns, since it allows the compiled pattern to be up to 64K in size.
- </P>
- <P>
  <pre>
    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
- </PRE>
+ </pre>
- </P>
- <P>
  The output is an integer that contains the threshold above which the POSIX
  interface uses <b>malloc()</b> for output vectors. Further details are given in
- the <b>pcreposix</b> documentation.
+ the
- </P>
+ <a href="pcreposix.html"><b>pcreposix</b></a>
- <P>
+ documentation.
  <pre>
    PCRE_CONFIG_MATCH_LIMIT
- </PRE>
+ </pre>
- </P>
- <P>
  The output is an integer that gives the default limit for the number of
  internal matching function calls in a <b>pcre_exec()</b> execution. Further
  details are given with <b>pcre_exec()</b> below.
+ <pre>
+   PCRE_CONFIG_STACKRECURSE
+ </pre>
+ The output is an integer that is set to one if internal recursion when running
+ <b>pcre_exec()</b> is implemented by recursive function calls that use the stack
+ to remember their state. This is the usual way that PCRE is compiled. The
+ output is zero if PCRE was compiled to use blocks of data on the heap instead
+ of recursive function calls. In this case, <b>pcre_stack_malloc</b> and
+ <b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus
+ avoiding the use of the stack.
  </P>
- <br><a name="SEC5" href="#TOC1">COMPILING A PATTERN</a><br>
+ <br><a name="SEC6" href="#TOC1">COMPILING A PATTERN</a><br>
  <P>
  <b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b>
  <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
  <b>const unsigned char *<i>tableptr</i>);</b>
+ <b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b>
+ <b>int *<i>errorcodeptr</i>,</b>
+ <b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b>
+ <b>const unsigned char *<i>tableptr</i>);</b>
  </P>
  <P>
- The function <b>pcre_compile()</b> is called to compile a pattern into an
+ Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be
- internal form. The pattern is a C string terminated by a binary zero, and
+ called to compile a pattern into an internal form. The only difference between
- is passed in the argument <i>pattern</i>. A pointer to a single block of memory
+ the two interfaces is that <b>pcre_compile2()</b> has an additional argument,
- that is obtained via <b>pcre_malloc</b> is returned. This contains the compiled
+ <i>errorcodeptr</i>, via which a numerical error code can be returned.
- code and related data. The <b>pcre</b> type is defined for the returned block;
+ </P>
- this is a typedef for a structure whose contents are not externally defined. It
+ <P>
- is up to the caller to free the memory when it is no longer required.
+ The pattern is a C string terminated by a binary zero, and is passed in the
+ <i>pattern</i> argument. A pointer to a single block of memory that is obtained
+ via <b>pcre_malloc</b> is returned. This contains the compiled code and related
+ data. The <b>pcre</b> type is defined for the returned block; this is a typedef
+ for a structure whose contents are not externally defined. It is up to the
+ caller to free the memory when it is no longer required.
  </P>
  <P>
  Although the compiled code of a PCRE regex is relocatable, that is, it does not
  depend on memory location, the complete <b>pcre</b> data block is not
- fully relocatable, because it contains a copy of the <i>tableptr</i> argument,
+ fully relocatable, because it may contain a copy of the <i>tableptr</i>
- which is an address (see below).
+ argument, which is an address (see below).
  </P>
  <P>
  The <i>options</i> argument contains independent bits that affect the
- compilation. It should be zero if no options are required. Some of the options,
+ compilation. It should be zero if no options are required. The available
- in particular, those that are compatible with Perl, can also be set and unset
+ options are described below. Some of them, in particular, those that are
- from within the pattern (see the detailed description of regular expressions
+ compatible with Perl, can also be set and unset from within the pattern (see
- in the <b>pcrepattern</b> documentation). For these options, the contents of the
+ the detailed description in the
- <i>options</i> argument specifies their initial settings at the start of
+ <a href="pcrepattern.html"><b>pcrepattern</b></a>
- compilation and execution. The PCRE_ANCHORED option can be set at the time of
+ documentation). For these options, the contents of the <i>options</i> argument
- matching as well as at compile time.
+ specifies their initial settings at the start of compilation and execution. The
+ PCRE_ANCHORED option can be set at the time of matching as well as at compile
+ time.
  </P>
  <P>
  If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately.
-Line 278 
 the error was discovered is placed in th
+Line 363 
 the error was discovered is placed in th
  <i>erroffset</i>, which must not be NULL. If it is, an immediate error is given.
  </P>
  <P>
- If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
+ If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the
- character tables which are built when it is compiled, using the default C
+ <i>errorcodeptr</i> argument is not NULL, a non-zero error code number is
- locale. Otherwise, <i>tableptr</i> must be the result of a call to
+ returned via this argument in the event of an error. This is in addition to the
- <b>pcre_maketables()</b>. See the section on locale support below.
+ textual error message. Error codes and messages are listed below.
  </P>
  <P>
- This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
+ If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of
+ character tables that are built when PCRE is compiled, using the default C
+ locale. Otherwise, <i>tableptr</i> must be an address that is the result of a
+ call to <b>pcre_maketables()</b>. This value is stored with the compiled
+ pattern, and used again by <b>pcre_exec()</b>, unless another table pointer is
+ passed to it. For more discussion, see the section on locale support below.
  </P>
  <P>
+ This code fragment shows a typical straightforward call to <b>pcre_compile()</b>:
  <pre>
    pcre *re;
    const char *error;
-Line 297 
 This code fragment shows a typical strai
+Line 388 
 This code fragment shows a typical strai
      &error,           /* for error message */
      &erroffset,       /* for error offset */
      NULL);            /* use default character tables */
- </PRE>
+ </pre>
- </P>
+ The following names for option bits are defined in the <b>pcre.h</b> header
- <P>
+ file:
- The following option bits are defined:
- </P>
- <P>
  <pre>
    PCRE_ANCHORED
- </PRE>
+ </pre>
- </P>
- <P>
  If this bit is set, the pattern is forced to be "anchored", that is, it is
- constrained to match only at the first matching point in the string which is
+ constrained to match only at the first matching point in the string that is
  being searched (the "subject string"). This effect can also be achieved by
  appropriate constructs in the pattern itself, which is the only way to do it in
  Perl.
- </P>
+ <pre>
- <P>
+   PCRE_AUTO_CALLOUT
+ </pre>
+ If this bit is set, <b>pcre_compile()</b> automatically inserts callout items,
+ all with number 255, before each pattern item. For discussion of the callout
+ facility, see the
+ <a href="pcrecallout.html"><b>pcrecallout</b></a>
+ documentation.
  <pre>
    PCRE_CASELESS
- </PRE>
+ </pre>
- </P>
- <P>
  If this bit is set, letters in the pattern match both upper and lower case
  letters. It is equivalent to Perl's /i option, and it can be changed within a
- pattern by a (?i) option setting.
+ pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
- </P>
+ concept of case for characters whose values are less than 128, so caseless
- <P>
+ matching is always possible. For characters with higher values, the concept of
+ case is supported if PCRE is compiled with Unicode property support, but not
+ otherwise. If you want to use caseless matching for characters 128 and above,
+ you must ensure that PCRE is compiled with Unicode property support as well as
+ with UTF-8 support.
  <pre>
    PCRE_DOLLAR_ENDONLY
- </PRE>
+ </pre>
- </P>
- <P>
  If this bit is set, a dollar metacharacter in the pattern matches only at the
  end of the subject string. Without this option, a dollar also matches
  immediately before the final character if it is a newline (but not before any
  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is
  set. There is no equivalent to this option in Perl, and no way to set it within
  a pattern.
- </P>
- <P>
  <pre>
    PCRE_DOTALL
- </PRE>
+ </pre>
- </P>
- <P>
  If this bit is set, a dot metacharater in the pattern matches all characters,
  including newlines. Without it, newlines are excluded. This option is
  equivalent to Perl's /s option, and it can be changed within a pattern by a
  (?s) option setting. A negative class such as [^a] always matches a newline
  character, independent of the setting of this option.
- </P>
- <P>
  <pre>
    PCRE_EXTENDED
- </PRE>
+ </pre>
- </P>
- <P>
  If this bit is set, whitespace data characters in the pattern are totally
  ignored except when escaped or inside a character class. Whitespace does not
  include the VT character (code 11). In addition, characters between an
-Line 367 
 This option makes it possible to include
+Line 451 
 This option makes it possible to include
  Note, however, that this applies only to data characters. Whitespace characters
  may never appear within special character sequences in a pattern, for example
  within the sequence (?( which introduces a conditional subpattern.
- </P>
- <P>
  <pre>
    PCRE_EXTRA
- </PRE>
+ </pre>
- </P>
- <P>
  This option was invented in order to turn on additional functionality of PCRE
  that is incompatible with Perl, but it is currently of very little use. When
  set, any backslash in a pattern that is followed by a letter that has no
-Line 382 
 expansion. By default, as in Perl, a bac
+Line 462 
 expansion. By default, as in Perl, a bac
  special meaning is treated as a literal. There are at present no other features
  controlled by this option. It can also be set by a (?X) option setting within a
  pattern.
- </P>
+ <pre>
- <P>
+   PCRE_FIRSTLINE
+ </pre>
+ If this option is set, an unanchored pattern is required to match before or at
+ the first newline character in the subject string, though the matched text may
+ continue over the newline.
  <pre>
    PCRE_MULTILINE
- </PRE>
+ </pre>
- </P>
+ By default, PCRE treats the subject string as consisting of a single line of
- <P>
+ characters (even if it actually contains newlines). The "start of line"
- By default, PCRE treats the subject string as consisting of a single "line" of
- characters (even if it actually contains several newlines). The "start of line"
  metacharacter (^) matches only at the start of the string, while the "end of
  line" metacharacter ($) matches only at the end of the string, or before a
  terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
-Line 403 
 string, respectively, as well as at the
+Line 485 
 string, respectively, as well as at the
  to Perl's /m option, and it can be changed within a pattern by a (?m) option
  setting. If there are no "\n" characters in a subject string, or no
  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
- </P>
- <P>
  <pre>
    PCRE_NO_AUTO_CAPTURE
- </PRE>
+ </pre>
- </P>
- <P>
  If this option is set, it disables the use of numbered capturing parentheses in
  the pattern. Any opening parenthesis that is not followed by ? behaves as if it
  were followed by ?: but named parentheses can still be used for capturing (and
  they acquire numbers in the usual way). There is no equivalent of this option
  in Perl.
- </P>
- <P>
  <pre>
    PCRE_UNGREEDY
- </PRE>
+ </pre>
- </P>
- <P>
  This option inverts the "greediness" of the quantifiers so that they are not
  greedy by default, but become greedy if followed by "?". It is not compatible
  with Perl. It can also be set by a (?U) option setting within the pattern.
- </P>
- <P>
  <pre>
    PCRE_UTF8
- </PRE>
+ </pre>
- </P>
- <P>
  This option causes PCRE to regard both the pattern and the subject as strings
  of UTF-8 characters instead of single-byte character strings. However, it is
- available only if PCRE has been built to include UTF-8 support. If not, the use
+ available only when PCRE is built to include UTF-8 support. If not, the use
  of this option provokes an error. Details of how this option changes the
  behaviour of PCRE are given in the
  <a href="pcre.html#utf8support">section on UTF-8 support</a>
  in the main
  <a href="pcre.html"><b>pcre</b></a>
  page.
+ <pre>
+   PCRE_NO_UTF8_CHECK
+ </pre>
+ 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,
+ <b>pcre_compile()</b> 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 <b>pcre_exec()</b> and
+ <b>pcre_dfa_exec()</b>, to suppress the UTF-8 validity checking of subject
+ strings.
+ </P>
+ <br><a name="SEC7" href="#TOC1">COMPILATION ERROR CODES</a><br>
+ <P>
+ The following table lists the error codes than may be returned by
+ <b>pcre_compile2()</b>, along with the error messages that may be returned by
+ both compiling functions.
+ <pre>
+ no error
+ \ at end of pattern
+ \c at end of pattern
+ unrecognized character follows \
+ numbers out of order in {} quantifier
+ number too big in {} quantifier
+ missing terminating ] for character class
+ invalid escape sequence in character class
+ range out of order in character class
+ nothing to repeat
+ operand of unlimited repeat could match the empty string
+ internal error: unexpected repeat
+ unrecognized character after (?
+ POSIX named classes are supported only within a class
+ missing )
+ reference to non-existent subpattern
+ erroffset passed as NULL
+ unknown option bit(s) set
+ missing ) after comment
+ parentheses nested too deeply
+ regular expression too large
+ failed to get memory
+ unmatched parentheses
+ internal error: code overflow
+ unrecognized character after (?&#60;
+ lookbehind assertion is not fixed length
+ malformed number after (?(
+ conditional group contains more than two branches
+ assertion expected after (?(
+ (?R or (?digits must be followed by )
+ unknown POSIX class name
+ POSIX collating elements are not supported
+ this version of PCRE is not compiled with PCRE_UTF8 support
+ spare error
+ character value in \x{...} sequence is too large
+ invalid condition (?(0)
+ \C not allowed in lookbehind assertion
+ PCRE does not support \L, \l, \N, \U, or \u
+ number after (?C is &#62; 255
+ closing ) for (?C expected
+ recursive call could loop indefinitely
+ unrecognized character after (?P
+ syntax error after (?P
+ two named groups have the same name
+ invalid UTF-8 string
+ support for \P, \p, and \X has not been compiled
+ malformed \P or \p sequence
+ unknown property name after \P or \p
+ </PRE>
  </P>
- <br><a name="SEC6" href="#TOC1">STUDYING A PATTERN</a><br>
+ <br><a name="SEC8" href="#TOC1">STUDYING A PATTERN</a><br>
  <P>
- <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b>
+ <b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i></b>
  <b>const char **<i>errptr</i>);</b>
  </P>
  <P>
- When a pattern is going to be used several times, it is worth spending more
+ If a compiled pattern is going to be used several times, it is worth spending
- time analyzing it in order to speed up the time taken for matching. The
+ more time analyzing it in order to speed up the time taken for matching. The
  function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first
- argument. If studing the pattern produces additional information that will help
+ argument. If studying the pattern produces additional information that will
- speed up matching, <b>pcre_study()</b> returns a pointer to a <b>pcre_extra</b>
+ help speed up matching, <b>pcre_study()</b> returns a pointer to a
- block, in which the <i>study_data</i> field points to the results of the study.
+ <b>pcre_extra</b> block, in which the <i>study_data</i> field points to the
+ results of the study.
  </P>
  <P>
- The returned value from a <b>pcre_study()</b> can be passed directly to
+ The returned value from <b>pcre_study()</b> can be passed directly to
- <b>pcre_exec()</b>. However, the <b>pcre_extra</b> block also contains other
+ <b>pcre_exec()</b>. However, a <b>pcre_extra</b> block also contains other
  fields that can be set by the caller before the block is passed; these are
- described below. If studying the pattern does not produce any additional
+ described
- information, <b>pcre_study()</b> returns NULL. In that circumstance, if the
+ <a href="#extradata">below</a>
- calling program wants to pass some of the other fields to <b>pcre_exec()</b>, it
+ in the section on matching a pattern.
- must set up its own <b>pcre_extra</b> block.
+ </P>
+ <P>
+ If studying the pattern does not produce any additional information
+ <b>pcre_study()</b> returns NULL. In that circumstance, if the calling program
+ wants to pass any of the other fields to <b>pcre_exec()</b>, it must set up its
+ own <b>pcre_extra</b> block.
  </P>
  <P>
- The second argument contains option bits. At present, no options are defined
+ The second argument of <b>pcre_study()</b> contains option bits. At present, no
- for <b>pcre_study()</b>, and this argument should always be zero.
+ options are defined, and this argument should always be zero.
  </P>
  <P>
  The third argument for <b>pcre_study()</b> is a pointer for an error message. If
-Line 477 
 be sure that it has run successfully.
+Line 621 
 be sure that it has run successfully.
  </P>
  <P>
  This is a typical call to <b>pcre_study</b>():
- </P>
- <P>
  <pre>
    pcre_extra *pe;
    pe = pcre_study(
      re,             /* result of pcre_compile() */
 ,              /* no options exist */
      &error);        /* set to NULL or points to a message */
- </PRE>
+ </pre>
- </P>
- <P>
  At present, studying a pattern is useful only for non-anchored patterns that do
  not have a single fixed starting character. A bitmap of possible starting
- characters is created.
+ bytes is created.
- </P>
+ <a name="localesupport"></a></P>
- <a name="localesupport"></a><br><a name="SEC7" href="#TOC1">LOCALE SUPPORT</a><br>
+ <br><a name="SEC9" href="#TOC1">LOCALE SUPPORT</a><br>
  <P>
- PCRE handles caseless matching, and determines whether characters are letters,
+ PCRE handles caseless matching, and determines whether characters are letters
- digits, or whatever, by reference to a set of tables. When running in UTF-8
+ digits, or whatever, by reference to a set of tables, indexed by character
- mode, this applies only to characters with codes less than 256. The library
+ value. When running in UTF-8 mode, this applies only to characters with codes
- contains a default set of tables that is created in the default C locale when
+ less than 128. Higher-valued codes never match escapes such as \w or \d, but
- PCRE is compiled. This is used when the final argument of <b>pcre_compile()</b>
+ can be tested with \p if PCRE is built with Unicode character property
- is NULL, and is sufficient for many applications.
+ support.
  </P>
  <P>
- An alternative set of tables can, however, be supplied. Such tables are built
+ An internal set of tables is created in the default C locale when PCRE is
- by calling the <b>pcre_maketables()</b> function, which has no arguments, in the
+ built. This is used when the final argument of <b>pcre_compile()</b> is NULL,
- relevant locale. The result can then be passed to <b>pcre_compile()</b> as often
+ and is sufficient for many applications. An alternative set of tables can,
- as necessary. For example, to build and use tables that are appropriate for the
+ however, be supplied. These may be created in a different locale from the
- French locale (where accented characters with codes greater than 128 are
+ default. As more and more applications change to using Unicode, the need for
- treated as letters), the following code could be used:
+ this locale support is expected to die away.
  </P>
  <P>
+ External tables are built by calling the <b>pcre_maketables()</b> function,
+ which has no arguments, in the relevant locale. The result can then be passed
+ to <b>pcre_compile()</b> or <b>pcre_exec()</b> as often as necessary. For
+ example, to build and use tables that are appropriate for the French locale
+ (where accented characters with values greater than 128 are treated as letters),
+ the following code could be used:
  <pre>
-   setlocale(LC_CTYPE, "fr");
+   setlocale(LC_CTYPE, "fr_FR");
    tables = pcre_maketables();
    re = pcre_compile(..., tables);
- </PRE>
+ </pre>
+ When <b>pcre_maketables()</b> runs, the tables are built in memory that is
+ obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure
+ that the memory containing the tables remains available for as long as it is
+ needed.
  </P>
  <P>
- The tables are built in memory that is obtained via <b>pcre_malloc</b>. The
+ The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled
- pointer that is passed to <b>pcre_compile</b> is saved with the compiled
  pattern, and the same tables are used via this pointer by <b>pcre_study()</b>
- and <b>pcre_exec()</b>. Thus, for any single pattern, compilation, studying and
+ and normally also by <b>pcre_exec()</b>. Thus, by default, for any single
- matching all happen in the same locale, but different patterns can be compiled
+ pattern, compilation, studying and matching all happen in the same locale, but
- in different locales. It is the caller's responsibility to ensure that the
+ different patterns can be compiled in different locales.
- memory containing the tables remains available for as long as it is needed.
+ </P>
+ <P>
+ It is possible to pass a table pointer or NULL (indicating the use of the
+ internal tables) to <b>pcre_exec()</b>. Although not intended for this purpose,
+ this facility could be used to match a pattern in a different locale from the
+ one in which it was compiled. Passing table pointers at run time is discussed
+ below in the section on matching a pattern.
  </P>
- <br><a name="SEC8" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
+ <br><a name="SEC10" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br>
  <P>
  <b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
  <b>int <i>what</i>, void *<i>where</i>);</b>
-Line 542 
 the pattern was not studied. The third a
+Line 697 
 the pattern was not studied. The third a
  information is required, and the fourth argument is a pointer to a variable
  to receive the data. The yield of the function is zero for success, or one of
  the following negative numbers:
- </P>
- <P>
  <pre>
    PCRE_ERROR_NULL       the argument <i>code</i> was NULL
                          the argument <i>where</i> was NULL
    PCRE_ERROR_BADMAGIC   the "magic number" was not found
    PCRE_ERROR_BADOPTION  the value of <i>what</i> was invalid
- </PRE>
+ </pre>
- </P>
+ The "magic number" is placed at the start of each compiled pattern as an simple
- <P>
+ check against passing an arbitrary memory pointer. Here is a typical call of
- Here is a typical call of <b>pcre_fullinfo()</b>, to obtain the length of the
+ <b>pcre_fullinfo()</b>, to obtain the length of the compiled pattern:
- compiled pattern:
- </P>
- <P>
  <pre>
    int rc;
    unsigned long int length;
-Line 564 
 compiled pattern:
+Line 714 
 compiled pattern:
      pe,               /* result of pcre_study(), or NULL */
      PCRE_INFO_SIZE,   /* what is required */
      &length);         /* where to put the data */
- </PRE>
+ </pre>
- </P>
- <P>
  The possible values for the third argument are defined in <b>pcre.h</b>, and are
  as follows:
- </P>
- <P>
  <pre>
    PCRE_INFO_BACKREFMAX
- </PRE>
+ </pre>
- </P>
- <P>
  Return the number of the highest back reference in the pattern. The fourth
  argument should point to an <b>int</b> variable. Zero is returned if there are
  no back references.
- </P>
- <P>
  <pre>
    PCRE_INFO_CAPTURECOUNT
- </PRE>
+ </pre>
- </P>
- <P>
  Return the number of capturing subpatterns in the pattern. The fourth argument
- should point to an \fbint\fR variable.
+ should point to an <b>int</b> variable.
- </P>
+ <pre>
- <P>
+   PCRE_INFO_DEFAULT_TABLES
+ </pre>
+ Return a pointer to the internal default character tables within PCRE. The
+ fourth argument should point to an <b>unsigned char *</b> variable. This
+ information call is provided for internal use by the <b>pcre_study()</b>
+ function. External callers can cause PCRE to use its internal tables by passing
+ a NULL table pointer.
  <pre>
    PCRE_INFO_FIRSTBYTE
- </PRE>
+ </pre>
- </P>
- <P>
  Return information about the first byte of any matched string, for a
  non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the
  old name is still recognized for backwards compatibility.)
  </P>
  <P>
- If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote),
+ If there is a fixed first byte, for example, from a pattern such as
- it is returned in the integer pointed to by <i>where</i>. Otherwise, if either
+ (cat|cow|coyote), it is returned in the integer pointed to by <i>where</i>.
- </P>
+ Otherwise, if either
- <P>
+ <br>
+ <br>
  (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
  starts with "^", or
- </P>
+ <br>
- <P>
+ <br>
  (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
  (if it were set, the pattern would be anchored),
- </P>
+ <br>
- <P>
+ <br>
  -1 is returned, indicating that the pattern matches only at the start of a
  subject string or after any newline within the string. Otherwise -2 is
  returned. For anchored patterns, -2 is returned.
- </P>
- <P>
  <pre>
    PCRE_INFO_FIRSTTABLE
- </PRE>
+ </pre>
- </P>
- <P>
  If the pattern was studied, and this resulted in the construction of a 256-bit
  table indicating a fixed set of bytes for the first byte in any matching
  string, a pointer to the table is returned. Otherwise NULL is returned. The
  fourth argument should point to an <b>unsigned char *</b> variable.
- </P>
- <P>
  <pre>
    PCRE_INFO_LASTLITERAL
- </PRE>
+ </pre>
- </P>
- <P>
  Return the value of the rightmost literal byte that must exist in any matched
  string, other than at its start, if such a byte has been recorded. The fourth
  argument should point to an <b>int</b> variable. If there is no such byte, -1 is
-Line 640 
 returned. For anchored patterns, a last
+Line 777 
 returned. For anchored patterns, a last
  follows something of variable length. For example, for the pattern
  /^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value
  is -1.
- </P>
- <P>
  <pre>
    PCRE_INFO_NAMECOUNT
    PCRE_INFO_NAMEENTRYSIZE
    PCRE_INFO_NAMETABLE
- </PRE>
+ </pre>
- </P>
- <P>
  PCRE supports the use of named as well as numbered capturing parentheses. The
  names are just an additional way of identifying the parentheses, which still
- acquire a number. A caller that wants to extract data from a named subpattern
+ acquire numbers. A convenience function called <b>pcre_get_named_substring()</b>
- must convert the name to a number in order to access the correct pointers in
+ is provided for extracting an individual captured substring by name. It is also
- the output vector (described with <b>pcre_exec()</b> below). In order to do
+ possible to extract the data directly, by first converting the name to a number
- this, it must first use these three values to obtain the name-to-number mapping
+ in order to access the correct pointers in the output vector (described with
- table for the pattern.
+ <b>pcre_exec()</b> below). To do the conversion, you need to use the
+ name-to-number map, which is described by these three values.
  </P>
  <P>
  The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
-Line 667 
 are the number of the capturing parenthe
+Line 801 
 are the number of the capturing parenthe
  rest of the entry is the corresponding name, zero terminated. The names are in
  alphabetical order. For example, consider the following pattern (assume
  PCRE_EXTENDED is set, so white space - including newlines - is ignored):
- </P>
- <P>
  <pre>
-   (?P&#60;date&#62; (?P&#60;year&#62;(\d\d)?\d\d) -
+   (?P&#60;date&#62; (?P&#60;year&#62;(\d\d)?\d\d) - (?P&#60;month&#62;\d\d) - (?P&#60;day&#62;\d\d) )
-   (?P&#60;month&#62;\d\d) - (?P&#60;day&#62;\d\d) )
+ </pre>
- </PRE>
- </P>
- <P>
  There are four named subpatterns, so the table has four entries, and each entry
  in the table is eight bytes long. The table is as follows, with non-printing
- bytes shows in hex, and undefined bytes shown as ??:
+ bytes shows in hexadecimal, and undefined bytes shown as ??:
- </P>
- <P>
  <pre>
 01 d  a  t  e  00 ??
 05 d  a  y  00 ?? ??
 04 m  o  n  t  h  00
 02 y  e  a  r  00 ??
- </PRE>
+ </pre>
- </P>
+ When writing code to extract data from named subpatterns using the
- <P>
+ name-to-number map, remember that the length of each entry is likely to be
- When writing code to extract data from named subpatterns, remember that the
+ different for each compiled pattern.
- length of each entry may be different for each compiled pattern.
- </P>
- <P>
  <pre>
    PCRE_INFO_OPTIONS
- </PRE>
+ </pre>
- </P>
- <P>
  Return a copy of the options with which the pattern was compiled. The fourth
  argument should point to an <b>unsigned long int</b> variable. These option bits
  are those specified in the call to <b>pcre_compile()</b>, modified by any
-Line 705 
 top-level option settings within the pat
+Line 827 
 top-level option settings within the pat
  <P>
  A pattern is automatically anchored by PCRE if all of its top-level
  alternatives begin with one of the following:
- </P>
- <P>
  <pre>
    ^     unless PCRE_MULTILINE is set
    \A    always
    \G    always
-   .*    if PCRE_DOTALL is set and there are no back
+   .*    if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
-           references to the subpattern in which .* appears
+ </pre>
- </PRE>
- </P>
- <P>
  For such patterns, the PCRE_ANCHORED bit is set in the options returned by
  <b>pcre_fullinfo()</b>.
- </P>
- <P>
  <pre>
    PCRE_INFO_SIZE
- </PRE>
+ </pre>
- </P>
- <P>
  Return the size of the compiled pattern, that is, the value that was passed as
  the argument to <b>pcre_malloc()</b> when PCRE was getting memory in which to
  place the compiled data. The fourth argument should point to a <b>size_t</b>
  variable.
- </P>
- <P>
  <pre>
    PCRE_INFO_STUDYSIZE
- </PRE>
+ </pre>
- </P>
+ Return the size of the data block pointed to by the <i>study_data</i> field in
- <P>
- Returns the size of the data block pointed to by the <i>study_data</i> field in
  a <b>pcre_extra</b> block. That is, it is the value that was passed to
  <b>pcre_malloc()</b> when PCRE was getting memory into which to place the data
  created by <b>pcre_study()</b>. The fourth argument should point to a
  <b>size_t</b> variable.
  </P>
- <br><a name="SEC9" href="#TOC1">OBSOLETE INFO FUNCTION</a><br>
+ <br><a name="SEC11" href="#TOC1">OBSOLETE INFO FUNCTION</a><br>
  <P>
  <b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b>
  <b>*<i>firstcharptr</i>);</b>
-Line 753 
 restrictive to return all the available
+Line 862 
 restrictive to return all the available
  programs should use <b>pcre_fullinfo()</b> instead. The yield of
  <b>pcre_info()</b> is the number of capturing subpatterns, or one of the
  following negative numbers:
- </P>
- <P>
  <pre>
    PCRE_ERROR_NULL       the argument <i>code</i> was NULL
    PCRE_ERROR_BADMAGIC   the "magic number" was not found
- </PRE>
+ </pre>
- </P>
- <P>
  If the <i>optptr</i> argument is not NULL, a copy of the options with which the
  pattern was compiled is placed in the integer it points to (see
  PCRE_INFO_OPTIONS above).
-Line 770 
 If the pattern is not anchored and the <
+Line 875 
 If the pattern is not anchored and the <
  it is used to pass back information about the first character of any matched
  string (see PCRE_INFO_FIRSTBYTE above).
  </P>
- <br><a name="SEC10" href="#TOC1">MATCHING A PATTERN</a><br>
+ <br><a name="SEC12" href="#TOC1">REFERENCE COUNTS</a><br>
+ <P>
+ <b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b>
+ </P>
+ <P>
+ The <b>pcre_refcount()</b> function is used to maintain a reference count in the
+ data block that contains a compiled pattern. It is provided for the benefit of
+ applications that operate in an object-oriented manner, where different parts
+ of the application may be using the same compiled pattern, but you want to free
+ the block when they are all done.
+ </P>
+ <P>
+ When a pattern is compiled, the reference count field is initialized to zero.
+ It is changed only by calling this function, whose action is to add the
+ <i>adjust</i> value (which may be positive or negative) to it. The yield of the
+ function is the new value. However, the value of the count is constrained to
+ lie between 0 and 65535, inclusive. If the new value is outside these limits,
+ it is forced to the appropriate limit value.
+ </P>
+ <P>
+ Except when it is zero, the reference count is not correctly preserved if a
+ pattern is compiled on one host and then transferred to a host whose byte-order
+ is different. (This seems a highly unlikely scenario.)
+ </P>
+ <br><a name="SEC13" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
  <P>
  <b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
  <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
-Line 778 
 string (see PCRE_INFO_FIRSTBYTE above).
+Line 907 
 string (see PCRE_INFO_FIRSTBYTE above).
  </P>
  <P>
  The function <b>pcre_exec()</b> is called to match a subject string against a
- pre-compiled pattern, which is passed in the <i>code</i> argument. If the
+ compiled pattern, which is passed in the <i>code</i> argument. If the
  pattern has been studied, the result of the study should be passed in the
- <i>extra</i> argument.
+ <i>extra</i> 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
+ <a href="#dfamatch">below</a>
+ in the section about the <b>pcre_dfa_exec()</b> function.
  </P>
  <P>
- Here is an example of a simple call to <b>pcre_exec()</b>:
+ In most applications, the pattern will have been compiled (and optionally
+ studied) in the same process that calls <b>pcre_exec()</b>. However, it is
+ possible to save compiled patterns and study data, and then use them later
+ in different processes, possibly even on different hosts. For a discussion
+ about this, see the
+ <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
+ documentation.
  </P>
  <P>
+ Here is an example of a simple call to <b>pcre_exec()</b>:
  <pre>
    int rc;
    int ovector[30];
-Line 796 
 Here is an example of a simple call to <
+Line 936 
 Here is an example of a simple call to <
 ,             /* the length of the subject string */
 ,              /* start at offset 0 in the subject */
 ,              /* default options */
-     ovector,        /* vector for substring information */
+     ovector,        /* vector of integers for substring information */
-);            /* number of elements in the vector */
+);            /* number of elements (NOT size in bytes) */
- </PRE>
+ <a name="extradata"></a></PRE>
  </P>
+ <br><b>
+ Extra data for <b>pcre_exec()</b>
+ </b><br>
  <P>
  If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b>
  data block. The <b>pcre_study()</b> function returns such a block (when it
  doesn't return NULL), but you can also create one for yourself, and pass
- additional information in it. The fields in the block are as follows:
+ additional information in it. The fields in a <b>pcre_extra</b> block are as
- </P>
+ follows:
- <P>
  <pre>
    unsigned long int <i>flags</i>;
    void *<i>study_data</i>;
    unsigned long int <i>match_limit</i>;
    void *<i>callout_data</i>;
- </PRE>
+   const unsigned char *<i>tables</i>;
- </P>
+ </pre>
- <P>
  The <i>flags</i> field is a bitmap that specifies which of the other fields
  are set. The flag bits are:
- </P>
- <P>
  <pre>
    PCRE_EXTRA_STUDY_DATA
    PCRE_EXTRA_MATCH_LIMIT
    PCRE_EXTRA_CALLOUT_DATA
- </PRE>
+   PCRE_EXTRA_TABLES
- </P>
+ </pre>
- <P>
  Other flag bits should be set to zero. The <i>study_data</i> field is set in the
  <b>pcre_extra</b> block that is returned by <b>pcre_study()</b>, together with
- the appropriate flag bit. You should not set this yourself, but you can add to
+ the appropriate flag bit. You should not set this yourself, but you may add to
- the block by setting the other fields.
+ the block by setting the other fields and their corresponding flag bits.
  </P>
  <P>
  The <i>match_limit</i> 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. Internally, PCRE uses a
+ classic example is the use of nested unlimited repeats.
- function called <b>match()</b> which it calls repeatedly (sometimes
+ </P>
- recursively). The limit is imposed on the number of times this function is
+ <P>
- called during a match, which has the effect of limiting the amount of recursion
+ Internally, PCRE uses a function called <b>match()</b> which it calls repeatedly
- and backtracking that can take place. For patterns that are not anchored, the
+ (sometimes recursively). The limit is imposed on the number of times this
- count starts from zero for each position in the subject string.
+ function is called during a match, which has the effect of limiting the amount
+ of recursion and backtracking that can take place. For patterns that are not
+ anchored, the count starts from zero for each position in the subject string.
  </P>
  <P>
  The default limit for the library can be set when PCRE is built; the default
  default is 10 million, which handles all but the most extreme cases. You can
- reduce the default by suppling <b>pcre_exec()</b> with a \fRpcre_extra\fR block
+ reduce the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b> block
  in which <i>match_limit</i> is set to a smaller value, and
  PCRE_EXTRA_MATCH_LIMIT is set in the <i>flags</i> field. If the limit is
  exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_MATCHLIMIT.
  </P>
  <P>
  The <i>pcre_callout</i> field is used in conjunction with the "callout" feature,
- which is described in the <b>pcrecallout</b> documentation.
+ which is described in the
- </P>
+ <a href="pcrecallout.html"><b>pcrecallout</b></a>
- <P>
+ documentation.
- The PCRE_ANCHORED option can be passed in the <i>options</i> argument, whose
- unused bits must be zero. This limits <b>pcre_exec()</b> to matching at the
- first matching position. However, if a pattern was compiled with PCRE_ANCHORED,
- or turned out to be anchored by virtue of its contents, it cannot be made
- unachored at matching time.
- </P>
- <P>
- There are also three further options that can be set only at matching time:
  </P>
  <P>
+ The <i>tables</i> field is used to pass a character tables pointer to
+ <b>pcre_exec()</b>; this overrides the value that is stored with the compiled
+ pattern. A non-NULL value is stored with the compiled pattern only if custom
+ tables were supplied to <b>pcre_compile()</b> via its <i>tableptr</i> argument.
+ If NULL is passed to <b>pcre_exec()</b> using this mechanism, it forces PCRE's
+ internal tables to be used. This facility is helpful when re-using patterns
+ that have been saved after compiling with an external set of tables, because
+ the external tables might be at a different address when <b>pcre_exec()</b> is
+ called. See the
+ <a href="pcreprecompile.html"><b>pcreprecompile</b></a>
+ documentation for a discussion of saving compiled patterns for later use.
+ </P>
+ <br><b>
+ Option bits for <b>pcre_exec()</b>
+ </b><br>
+ <P>
+ The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be
+ zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NOTBOL,
+ PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
+ <pre>
+   PCRE_ANCHORED
+ </pre>
+ The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first
+ matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
+ to be anchored by virtue of its contents, it cannot be made unachored at
+ matching time.
  <pre>
    PCRE_NOTBOL
- </PRE>
+ </pre>
- </P>
+ This option specifies that first character of the subject string is not the
- <P>
+ beginning of a line, so the circumflex metacharacter should not match before
- The first character of the string is not the beginning of a line, so the
+ it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
- circumflex metacharacter should not match before it. Setting this without
+ never to match. This option affects only the behaviour of the circumflex
- PCRE_MULTILINE (at compile time) causes circumflex never to match.
+ metacharacter. It does not affect \A.
- </P>
- <P>
  <pre>
    PCRE_NOTEOL
- </PRE>
+ </pre>
- </P>
+ This option specifies that the end of the subject string is not the end of a
- <P>
+ line, so the dollar metacharacter should not match it nor (except in multiline
- The end of the string is not the end of a line, so the dollar metacharacter
+ mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
- should not match it nor (except in multiline mode) a newline immediately before
+ compile time) causes dollar never to match. This option affects only the
- it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never
+ behaviour of the dollar metacharacter. It does not affect \Z or \z.
- to match.
- </P>
- <P>
  <pre>
    PCRE_NOTEMPTY
- </PRE>
+ </pre>
- </P>
- <P>
  An empty string is not considered to be a valid match if this option is set. If
  there are alternatives in the pattern, they are tried. If all the alternatives
  match the empty string, the entire match fails. For example, if the pattern
- </P>
- <P>
  <pre>
    a?b?
- </PRE>
+ </pre>
- </P>
- <P>
  is applied to a string not beginning with "a" or "b", it matches the 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".
-Line 910 
 Perl has no direct equivalent of PCRE_NO
+Line 1057 
 Perl has no direct equivalent of PCRE_NO
  of a pattern match of the empty string within its <b>split()</b> 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 set, and then if that fails by advancing the starting offset (see
+ PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
- below) and trying an ordinary match again.
+ starting offset (see below) and trying an ordinary match again. There is some
+ code that demonstrates how to do this in the <i>pcredemo.c</i> sample program.
+ <pre>
+   PCRE_NO_UTF8_CHECK
+ </pre>
+ When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
+ string is automatically checked when <b>pcre_exec()</b> is subsequently called.
+ The value of <i>startoffset</i> 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,
+ <b>pcre_exec()</b> returns the error PCRE_ERROR_BADUTF8. If <i>startoffset</i>
+ contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
+ </P>
+ <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
+ calling <b>pcre_exec()</b>. You might want to do this for the second and
+ subsequent calls to <b>pcre_exec()</b> 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 <i>startoffset</i> points to the start of a UTF-8 character. When
+ PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
+ subject, or a value of <i>startoffset</i> that does not point to the start of a
+ UTF-8 character, is undefined. Your program may crash.
+ <pre>
+   PCRE_PARTIAL
+ </pre>
+ This option turns on the partial matching feature. If the subject string fails
+ to match the pattern, but at some point during the matching process the end of
+ the subject was reached (that is, the subject partially matches the pattern and
+ the failure to match occurred only because there were not enough subject
+ characters), <b>pcre_exec()</b> returns PCRE_ERROR_PARTIAL instead of
+ PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
+ may appear in the pattern. These are discussed in the
+ <a href="pcrepartial.html"><b>pcrepartial</b></a>
+ documentation.
  </P>
+ <br><b>
+ The string to be matched by <b>pcre_exec()</b>
+ </b><br>
  <P>
  The subject string is passed to <b>pcre_exec()</b> as a pointer in
- <i>subject</i>, a length in <i>length</i>, and a starting offset in
+ <i>subject</i>, a length in <i>length</i>, and a starting byte offset in
- <i>startoffset</i>. Unlike the pattern string, the subject may contain binary
+ <i>startoffset</i>. In UTF-8 mode, the byte offset must point to the start of a
- zero bytes. When the starting offset is zero, the search for a match starts at
+ UTF-8 character. Unlike the pattern string, the subject may contain binary zero
- the beginning of the subject, and this is by far the most common case.
+ bytes. When the starting offset is zero, the search for a match starts at the
- </P>
+ beginning of the subject, and this is by far the most common case.
- <P>
- If the pattern was compiled with the PCRE_UTF8 option, the subject must be a
- sequence of bytes that is a valid UTF-8 string. If an invalid UTF-8 string is
- passed, PCRE's behaviour is not defined.
  </P>
  <P>
  A non-zero starting offset is useful when searching for another match in the
-Line 931 
 same subject by calling pcre_exec()
+Line 1110 
 same subject by calling pcre_exec()
  Setting <i>startoffset</i> differs from just passing over a shortened string and
  setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
  lookbehind. For example, consider the pattern
- </P>
- <P>
  <pre>
    \Biss\B
- </PRE>
+ </pre>
- </P>
- <P>
  which finds occurrences of "iss" in the middle of words. (\B matches only if
  the current position in the subject is not a word boundary.) When applied to
  the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first
-Line 950 
 behind the starting point to discover th
+Line 1125 
 behind the starting point to discover th
  </P>
  <P>
  If a non-zero starting offset is passed when the pattern is anchored, one
- attempt to match at the given offset is tried. This can only succeed if the
+ 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.
  </P>
+ <br><b>
+ How <b>pcre_exec()</b> returns captured substrings
+ </b><br>
  <P>
  In general, a pattern matches a certain portion of the subject, and in
  addition, further substrings from the subject may be picked out by parts of the
-Line 964 
 kinds of parenthesized subpattern that d
+Line 1142 
 kinds of parenthesized subpattern that d
  <P>
  Captured substrings are returned to the caller via a vector of integer offsets
  whose address is passed in <i>ovector</i>. The number of elements in the vector
- is passed in <i>ovecsize</i>. The first two-thirds of the vector is used to pass
+ is passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>:
- back captured substrings, each substring using a pair of integers. The
+ this argument is NOT the size of <i>ovector</i> in bytes.
- remaining third of the vector is used as workspace by <b>pcre_exec()</b> while
+ </P>
- matching capturing subpatterns, and is not available for passing back
+ <P>
- information. The length passed in <i>ovecsize</i> should always be a multiple of
+ The first two-thirds of the vector is used to pass back captured substrings,
- three. If it is not, it is rounded down.
+ each substring using a pair of integers. The remaining third of the vector is
+ used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns,
+ and is not available for passing back information. The length passed in
+ <i>ovecsize</i> should always be a multiple of three. If it is not, it is
+ rounded down.
  </P>
  <P>
- When a match has been successful, information about captured substrings is
+ When a match is successful, information about captured substrings is returned
- returned in pairs of integers, starting at the beginning of <i>ovector</i>, and
+ in pairs of integers, starting at the beginning of <i>ovector</i>, and
  continuing up to two-thirds of its length at the most. The first element of a
  pair is set to the offset of the first character in a substring, and the second
  is set to the offset of the first character after the end of a substring. The
-Line 997 
 values corresponding to the unused subpa
+Line 1179 
 values corresponding to the unused subpa
  </P>
  <P>
  If a capturing subpattern is matched repeatedly, it is the last portion of the
- string that it matched that gets returned.
+ string that it matched that is returned.
  </P>
  <P>
- If the vector is too small to hold all the captured substrings, it is used as
+ If the vector is too small to hold all the captured substring offsets, it is
- far as possible (up to two-thirds of its length), and the function returns a
+ used as far as possible (up to two-thirds of its length), and the function
- value of zero. In particular, if the substring offsets are not of interest,
+ returns a value of zero. In particular, if the substring offsets are not of
- <b>pcre_exec()</b> may be called with <i>ovector</i> passed as NULL and
+ interest, <b>pcre_exec()</b> may be called with <i>ovector</i> passed as NULL and
  <i>ovecsize</i> as zero. However, if the pattern contains back references and
- the <i>ovector</i> isn't big enough to remember the related substrings, PCRE has
+ the <i>ovector</i> is not big enough to remember the related substrings, PCRE
- to get additional memory for use during matching. Thus it is usually advisable
+ has to get additional memory for use during matching. Thus it is usually
- to supply an <i>ovector</i>.
+ advisable to supply an <i>ovector</i>.
  </P>
  <P>
  Note that <b>pcre_info()</b> can be used to find out how many capturing
  subpatterns there are in a compiled pattern. The smallest size for
  <i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to
  the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3.
- </P>
+ <a name="errorlist"></a></P>
+ <br><b>
+ Return values from <b>pcre_exec()</b>
+ </b><br>
  <P>
  If <b>pcre_exec()</b> fails, it returns a negative number. The following are
  defined in the header file:
- </P>
- <P>
  <pre>
    PCRE_ERROR_NOMATCH        (-1)
- </PRE>
+ </pre>
- </P>
- <P>
  The subject string did not match the pattern.
- </P>
- <P>
  <pre>
    PCRE_ERROR_NULL           (-2)
- </PRE>
+ </pre>
- </P>
- <P>
  Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was
  NULL and <i>ovecsize</i> was not zero.
- </P>
- <P>
  <pre>
    PCRE_ERROR_BADOPTION      (-3)
- </PRE>
+ </pre>
- </P>
- <P>
  An unrecognized bit was set in the <i>options</i> argument.
- </P>
- <P>
  <pre>
    PCRE_ERROR_BADMAGIC       (-4)
- </PRE>
+ </pre>
- </P>
- <P>
  PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
- the case when it is passed a junk pointer. This is the error it gives when the
+ the case when it is passed a junk pointer and to detect when a pattern that was
- magic number isn't present.
+ compiled in an environment of one endianness is run in an environment with the
- </P>
+ other endianness. This is the error that PCRE gives when the magic number is
- <P>
+ not present.
  <pre>
    PCRE_ERROR_UNKNOWN_NODE   (-5)
- </PRE>
+ </pre>
- </P>
- <P>
  While running the pattern match, an unknown item was encountered in the
  compiled pattern. This error could be caused by a bug in PCRE or by overwriting
  of the compiled pattern.
- </P>
- <P>
  <pre>
    PCRE_ERROR_NOMEMORY       (-6)
- </PRE>
+ </pre>
- </P>
- <P>
  If a pattern contains back references, but the <i>ovector</i> that is passed to
  <b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE
  gets a block of memory at the start of matching to use for this purpose. If the
- call via <b>pcre_malloc()</b> fails, this error is given. The memory is freed at
+ call via <b>pcre_malloc()</b> fails, this error is given. The memory is
- the end of matching.
+ automatically freed at the end of matching.
- </P>
- <P>
  <pre>
    PCRE_ERROR_NOSUBSTRING    (-7)
- </PRE>
+ </pre>
- </P>
- <P>
  This error is used by the <b>pcre_copy_substring()</b>,
  <b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see
  below). It is never returned by <b>pcre_exec()</b>.
- </P>
- <P>
  <pre>
    PCRE_ERROR_MATCHLIMIT     (-8)
- </PRE>
+ </pre>
- </P>
- <P>
  The recursion and backtracking limit, as specified by the <i>match_limit</i>
  field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the
  description above.
- </P>
- <P>
  <pre>
    PCRE_ERROR_CALLOUT        (-9)
- </PRE>
+ </pre>
- </P>
- <P>
  This error is never generated by <b>pcre_exec()</b> itself. It is provided for
  use by callout functions that want to yield a distinctive error code. See the
- <b>pcrecallout</b> documentation for details.
+ <a href="pcrecallout.html"><b>pcrecallout</b></a>
+ documentation for details.
+ <pre>
+   PCRE_ERROR_BADUTF8        (-10)
+ </pre>
+ A string that contains an invalid UTF-8 byte sequence was passed as a subject.
+ <pre>
+   PCRE_ERROR_BADUTF8_OFFSET (-11)
+ </pre>
+ The UTF-8 byte sequence that was passed as a subject was valid, but the value
+ of <i>startoffset</i> did not point to the beginning of a UTF-8 character.
+ <pre>
+   PCRE_ERROR_PARTIAL        (-12)
+ </pre>
+ The subject string did not match, but it did match partially. See the
+ <a href="pcrepartial.html"><b>pcrepartial</b></a>
+ documentation for details of partial matching.
+ <pre>
+   PCRE_ERROR_BADPARTIAL     (-13)
+ </pre>
+ The PCRE_PARTIAL option was used with a compiled pattern containing items that
+ are not supported for partial matching. See the
+ <a href="pcrepartial.html"><b>pcrepartial</b></a>
+ documentation for details of partial matching.
+ <pre>
+   PCRE_ERROR_INTERNAL       (-14)
+ </pre>
+ An unexpected internal error has occurred. This error could be caused by a bug
+ in PCRE or by overwriting of the compiled pattern.
+ <pre>
+   PCRE_ERROR_BADCOUNT       (-15)
+ </pre>
+ This error is given if the value of the <i>ovecsize</i> argument is negative.
  </P>
- <br><a name="SEC11" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
+ <br><a name="SEC14" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
  <P>
  <b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b>
  <b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b>
-Line 1134 
 a C string.
+Line 1317 
 a C string.
  </P>
  <P>
  The first three arguments are the same for all three of these functions:
- <i>subject</i> is the subject string which has just been successfully matched,
+ <i>subject</i> is the subject string that has just been successfully matched,
  <i>ovector</i> is a pointer to the vector of integer offsets that was passed to
  <b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were
  captured by the match, including the substring that matched the entire regular
- expression. This is the value returned by <b>pcre_exec</b> if it is greater than
+ expression. This is the value returned by <b>pcre_exec()</b> if it is greater
- zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of space
+ than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of
- in <i>ovector</i>, the value passed as <i>stringcount</i> should be the size of
+ space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the
- the vector divided by three.
+ number of elements in the vector divided by three.
  </P>
  <P>
  The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>
  extract a single substring, whose number is given as <i>stringnumber</i>. A
- value of zero extracts the substring that matched the entire pattern, while
+ value of zero extracts the substring that matched the entire pattern, whereas
  higher values extract the captured substrings. For <b>pcre_copy_substring()</b>,
  the string is placed in <i>buffer</i>, whose length is given by
  <i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is
  obtained via <b>pcre_malloc</b>, and its address is returned via
  <i>stringptr</i>. The yield of the function is the length of the string, not
  including the terminating zero, or one of
- </P>
- <P>
  <pre>
    PCRE_ERROR_NOMEMORY       (-6)
- </PRE>
+ </pre>
- </P>
- <P>
  The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get
  memory failed for <b>pcre_get_substring()</b>.
- </P>
- <P>
  <pre>
    PCRE_ERROR_NOSUBSTRING    (-7)
- </PRE>
+ </pre>
- </P>
- <P>
  There is no substring whose number is <i>stringnumber</i>.
  </P>
  <P>
  The <b>pcre_get_substring_list()</b> function extracts all available substrings
  and builds a list of pointers to them. All this is done in a single block of
- memory which is obtained via <b>pcre_malloc</b>. The address of the memory block
+ memory that is obtained via <b>pcre_malloc</b>. The address of the memory block
  is returned via <i>listptr</i>, which is also the start of the list of string
  pointers. The end of the list is marked by a NULL pointer. The yield of the
  function is zero if all went well, or
- </P>
- <P>
  <pre>
    PCRE_ERROR_NOMEMORY       (-6)
- </PRE>
+ </pre>
- </P>
- <P>
  if the attempt to get the memory block failed.
  </P>
  <P>
-Line 1206 
 linked via a special interface to anothe
+Line 1377 
 linked via a special interface to anothe
  <b>pcre_free</b> directly; it is for these cases that the functions are
  provided.
  </P>
- <br><a name="SEC12" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
+ <br><a name="SEC15" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
+ <P>
+ <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
+ <b>const char *<i>name</i>);</b>
+ </P>
  <P>
  <b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b>
  <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
-Line 1214 
 provided.
+Line 1389 
 provided.
  <b>char *<i>buffer</i>, int <i>buffersize</i>);</b>
  </P>
  <P>
- <b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b>
- <b>const char *<i>name</i>);</b>
- </P>
- <P>
  <b>int pcre_get_named_substring(const pcre *<i>code</i>,</b>
  <b>const char *<i>subject</i>, int *<i>ovector</i>,</b>
  <b>int <i>stringcount</i>, const char *<i>stringname</i>,</b>
  <b>const char **<i>stringptr</i>);</b>
  </P>
  <P>
- To extract a substring by name, you first have to find associated number. This
+ To extract a substring by name, you first have to find associated number.
- can be done by calling <b>pcre_get_stringnumber()</b>. The first argument is the
+ For example, for this pattern
- compiled pattern, and the second is the name. For example, for this pattern
- </P>
- <P>
  <pre>
-   ab(?&#60;xxx&#62;\d+)...
+   (a+)b(?&#60;xxx&#62;\d+)...
- </PRE>
+ </pre>
+ the number of the subpattern called "xxx" is 2. You can find the number from
+ the name by calling <b>pcre_get_stringnumber()</b>. The first argument is the
+ compiled pattern, and the second is the name. The yield of the function is the
+ subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
+ that name.
  </P>
  <P>
- the number of the subpattern called "xxx" is 1. Given the number, you can then
+ Given the number, you can extract the substring directly, or use one of the
- extract the substring directly, or use one of the functions described in the
+ functions described in the previous section. For convenience, there are also
- previous section. For convenience, there are also two functions that do the
+ two functions that do the whole job.
- whole job.
  </P>
  <P>
  Most of the arguments of <i>pcre_copy_named_substring()</i> and
- <i>pcre_get_named_substring()</i> are the same as those for the functions that
+ <i>pcre_get_named_substring()</i> are the same as those for the similarly named
- extract by number, and so are not re-described here. There are just two
+ functions that extract by number. As these are described in the previous
- differences.
+ section, they are not re-described here. There are just two differences:
  </P>
  <P>
  First, instead of a substring number, a substring name is given. Second, there
-Line 1256 
 These functions call pcre_get_stringn
+Line 1428 
 These functions call pcre_get_stringn
  then call <i>pcre_copy_substring()</i> or <i>pcre_get_substring()</i>, as
  appropriate.
  </P>
+ <br><a name="SEC16" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br>
+ <P>
+ The traditional matching function uses a similar algorithm to Perl, which stops
+ when it finds the first match, starting at a given point in the subject. If you
+ want to find all possible matches, or the longest possible match, consider
+ using the alternative matching function (see below) instead. If you cannot use
+ the alternative function, but still need to find all possible matches, you
+ can kludge it up by making use of the callout facility, which is described in
+ the
+ <a href="pcrecallout.html"><b>pcrecallout</b></a>
+ documentation.
+ </P>
+ <P>
+ What you have to do is to insert a callout right at the end of the pattern.
+ When your callout function is called, extract and save the current matched
+ substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try
+ other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b>
+ will yield PCRE_ERROR_NOMATCH.
+ <a name="dfamatch"></a></P>
+ <br><a name="SEC17" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
+ <P>
+ <b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b>
+ <b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b>
+ <b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b>
+ <b>int *<i>workspace</i>, int <i>wscount</i>);</b>
+ </P>
+ <P>
+ The function <b>pcre_dfa_exec()</b> is called to match a subject string against
+ a compiled pattern, using a "DFA" matching algorithm. 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 the
+ <a href="pcrematching.html"><b>pcrematching</b></a>
+ documentation.
+ </P>
+ <P>
+ The arguments for the <b>pcre_dfa_exec()</b> function are the same as for
+ <b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a
+ different way, and this is described below. The other common arguments are used
+ in the same way as for <b>pcre_exec()</b>, so their description is not repeated
+ here.
+ </P>
+ <P>
+ The two additional arguments provide workspace for the function. The workspace
+ vector should contain at least 20 elements. It is used for keeping track of
+ multiple paths through the pattern tree. More workspace will be needed for
+ patterns and subjects where there are a lot of possible matches.
+ </P>
+ <P>
+ Here is an example of a simple call to <b>pcre_exec()</b>:
+ <pre>
+   int rc;
+   int ovector[10];
+   int wspace[20];
+   rc = pcre_exec(
+     re,             /* result of pcre_compile() */
+     NULL,           /* we didn't study the pattern */
+     "some string",  /* the subject string */
+,             /* the length of the subject string */
+,              /* start at offset 0 in the subject */
+,              /* default options */
+     ovector,        /* vector of integers for substring information */
+,             /* number of elements (NOT size in bytes) */
+     wspace,         /* working space vector */
+);            /* number of elements (NOT size in bytes) */
+ </PRE>
+ </P>
+ <br><b>
+ Option bits for <b>pcre_dfa_exec()</b>
+ </b><br>
+ <P>
+ The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be
+ zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NOTBOL,
+ PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,
+ PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are
+ the same as for <b>pcre_exec()</b>, so their description is not repeated here.
+ <pre>
+   PCRE_PARTIAL
+ </pre>
+ This has the same general effect as it does for <b>pcre_exec()</b>, but the
+ details are slightly different. When PCRE_PARTIAL is set for
+ <b>pcre_dfa_exec()</b>, 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 provided the partial match is set as the first
+ matching string.
+ <pre>
+   PCRE_DFA_SHORTEST
+ </pre>
+ Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
+ soon as it has found one match. Because of the way the DFA algorithm works,
+ this is necessarily the shortest possible match at the first possible matching
+ point in the subject string.
+ <pre>
+   PCRE_DFA_RESTART
+ </pre>
+ When <b>pcre_dfa_exec()</b> is called with the PCRE_PARTIAL option, and returns
+ a partial match, it is possible to call it again, with additional subject
+ characters, and have it continue with the same match. The PCRE_DFA_RESTART
+ option requests this action; when it is set, the <i>workspace</i> and
+ <i>wscount</i> options must reference the same vector as before because data
+ about the match so far is left in them after a partial match. There is more
+ discussion of this facility in the
+ <a href="pcrepartial.html"><b>pcrepartial</b></a>
+ documentation.
+ </P>
+ <br><b>
+ Successful returns from <b>pcre_dfa_exec()</b>
+ </b><br>
+ <P>
+ When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one
+ substring in the subject. Note, however, that all the matches from one run of
+ the function start at the same point in the subject. The shorter matches are
+ all initial substrings of the longer matches. For example, if the pattern
+ <pre>
+   &#60;.*&#62;
+ </pre>
+ is matched against the string
+ <pre>
+   This is &#60;something&#62; &#60;something else&#62; &#60;something further&#62; no more
+ </pre>
+ the three matched strings are
+ <pre>
+   &#60;something&#62;
+   &#60;something&#62; &#60;something else&#62;
+   &#60;something&#62; &#60;something else&#62; &#60;something further&#62;
+ </pre>
+ On success, the yield of the function is a number greater than zero, which is
+ the number of matched substrings. The substrings themselves are returned in
+ <i>ovector</i>. Each string uses two elements; the first is the offset to the
+ start, and the second is the offset to the end. All the strings have the same
+ start offset. (Space could have been saved by giving this only once, but it was
+ decided to retain some compatibility with the way <b>pcre_exec()</b> returns
+ data, even though the meaning of the strings is different.)
+ </P>
+ <P>
+ The strings are returned in reverse order of length; that is, the longest
+ matching string is given first. If there were too many matches to fit into
+ <i>ovector</i>, the yield of the function is zero, and the vector is filled with
+ the longest matches.
+ </P>
+ <br><b>
+ Error returns from <b>pcre_dfa_exec()</b>
+ </b><br>
+ <P>
+ The <b>pcre_dfa_exec()</b> function returns a negative number when it fails.
+ Many of the errors are the same as for <b>pcre_exec()</b>, and these are
+ described
+ <a href="#errorlist">above.</a>
+ There are in addition the following errors that are specific to
+ <b>pcre_dfa_exec()</b>:
+ <pre>
+   PCRE_ERROR_DFA_UITEM      (-16)
+ </pre>
+ This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern
+ that it does not support, for instance, the use of \C or a back reference.
+ <pre>
+   PCRE_ERROR_DFA_UCOND      (-17)
+ </pre>
+ This return is given if <b>pcre_dfa_exec()</b> encounters a condition item in a
+ pattern that uses a back reference for the condition. This is not supported.
+ <pre>
+   PCRE_ERROR_DFA_UMLIMIT    (-18)
+ </pre>
+ This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i>
+ block that contains a setting of the <i>match_limit</i> field. This is not
+ supported (it is meaningless).
+ <pre>
+   PCRE_ERROR_DFA_WSSIZE     (-19)
+ </pre>
+ This return is given if <b>pcre_dfa_exec()</b> runs out of space in the
+ <i>workspace</i> vector.
+ <pre>
+   PCRE_ERROR_DFA_RECURSE    (-20)
+ </pre>
+ When a recursive subpattern is processed, the matching function calls itself
+ recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This
+ error is given if the output vector is not large enough. This should be
+ extremely rare, as a vector of size 1000 is used.
+ </P>
  <P>
- Last updated: 03 February 2003
+ Last updated: 16 May 2005
  <br>
- Copyright &copy; 1997-2003 University of Cambridge.
+ Copyright &copy; 1997-2005 University of Cambridge.
+ <p>
+ Return to the <a href="index.html">PCRE index page</a>.
+ </p>

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