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diff --git a/doc/html/pcreapi.html b/doc/html/pcreapi.html new file mode 100644 index 0000000..b401ecc --- /dev/null +++ b/doc/html/pcreapi.html @@ -0,0 +1,2922 @@ +<html> +<head> +<title>pcreapi specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcreapi man page</h1> +<p> +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">PCRE NATIVE API BASIC FUNCTIONS</a> +<li><a name="TOC2" href="#SEC2">PCRE NATIVE API STRING EXTRACTION FUNCTIONS</a> +<li><a name="TOC3" href="#SEC3">PCRE NATIVE API AUXILIARY FUNCTIONS</a> +<li><a name="TOC4" href="#SEC4">PCRE NATIVE API INDIRECTED FUNCTIONS</a> +<li><a name="TOC5" href="#SEC5">PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a> +<li><a name="TOC6" href="#SEC6">PCRE API OVERVIEW</a> +<li><a name="TOC7" href="#SEC7">NEWLINES</a> +<li><a name="TOC8" href="#SEC8">MULTITHREADING</a> +<li><a name="TOC9" href="#SEC9">SAVING PRECOMPILED PATTERNS FOR LATER USE</a> +<li><a name="TOC10" href="#SEC10">CHECKING BUILD-TIME OPTIONS</a> +<li><a name="TOC11" href="#SEC11">COMPILING A PATTERN</a> +<li><a name="TOC12" href="#SEC12">COMPILATION ERROR CODES</a> +<li><a name="TOC13" href="#SEC13">STUDYING A PATTERN</a> +<li><a name="TOC14" href="#SEC14">LOCALE SUPPORT</a> +<li><a name="TOC15" href="#SEC15">INFORMATION ABOUT A PATTERN</a> +<li><a name="TOC16" href="#SEC16">REFERENCE COUNTS</a> +<li><a name="TOC17" href="#SEC17">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a> +<li><a name="TOC18" href="#SEC18">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a> +<li><a name="TOC19" href="#SEC19">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a> +<li><a name="TOC20" href="#SEC20">DUPLICATE SUBPATTERN NAMES</a> +<li><a name="TOC21" href="#SEC21">FINDING ALL POSSIBLE MATCHES</a> +<li><a name="TOC22" href="#SEC22">OBTAINING AN ESTIMATE OF STACK USAGE</a> +<li><a name="TOC23" href="#SEC23">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a> +<li><a name="TOC24" href="#SEC24">SEE ALSO</a> +<li><a name="TOC25" href="#SEC25">AUTHOR</a> +<li><a name="TOC26" href="#SEC26">REVISION</a> +</ul> +<P> +<b>#include <pcre.h></b> +</P> +<br><a name="SEC1" href="#TOC1">PCRE NATIVE API BASIC FUNCTIONS</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> +<br> +<br> +<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> +<br> +<br> +<b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>);</b> +<br> +<br> +<b>void pcre_free_study(pcre_extra *<i>extra</i>);</b> +<br> +<br> +<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> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +<br> +<br> +<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> +<br><a name="SEC2" href="#TOC1">PCRE NATIVE API STRING EXTRACTION FUNCTIONS</a><br> +<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> +<b> char *<i>buffer</i>, int <i>buffersize</i>);</b> +<br> +<br> +<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> +<b> int <i>buffersize</i>);</b> +<br> +<br> +<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> +<br> +<br> +<b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b> +<b> const char *<i>name</i>);</b> +<br> +<br> +<b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b> +<b> const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b> +<br> +<br> +<b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b> const char **<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre_get_substring_list(const char *<i>subject</i>,</b> +<b> int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b> +<br> +<br> +<b>void pcre_free_substring(const char *<i>stringptr</i>);</b> +<br> +<br> +<b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b> +</P> +<br><a name="SEC3" href="#TOC1">PCRE NATIVE API AUXILIARY FUNCTIONS</a><br> +<P> +<b>int pcre_jit_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> pcre_jit_stack *<i>jstack</i>);</b> +<br> +<br> +<b>pcre_jit_stack *pcre_jit_stack_alloc(int <i>startsize</i>, int <i>maxsize</i>);</b> +<br> +<br> +<b>void pcre_jit_stack_free(pcre_jit_stack *<i>stack</i>);</b> +<br> +<br> +<b>void pcre_assign_jit_stack(pcre_extra *<i>extra</i>,</b> +<b> pcre_jit_callback <i>callback</i>, void *<i>data</i>);</b> +<br> +<br> +<b>const unsigned char *pcre_maketables(void);</b> +<br> +<br> +<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> +<br> +<br> +<b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b> +<br> +<br> +<b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b> +<br> +<br> +<b>const char *pcre_version(void);</b> +<br> +<br> +<b>int pcre_pattern_to_host_byte_order(pcre *<i>code</i>,</b> +<b> pcre_extra *<i>extra</i>, const unsigned char *<i>tables</i>);</b> +</P> +<br><a name="SEC4" href="#TOC1">PCRE NATIVE API INDIRECTED FUNCTIONS</a><br> +<P> +<b>void *(*pcre_malloc)(size_t);</b> +<br> +<br> +<b>void (*pcre_free)(void *);</b> +<br> +<br> +<b>void *(*pcre_stack_malloc)(size_t);</b> +<br> +<br> +<b>void (*pcre_stack_free)(void *);</b> +<br> +<br> +<b>int (*pcre_callout)(pcre_callout_block *);</b> +<br> +<br> +<b>int (*pcre_stack_guard)(void);</b> +</P> +<br><a name="SEC5" href="#TOC1">PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a><br> +<P> +As well as support for 8-bit character strings, PCRE also supports 16-bit +strings (from release 8.30) and 32-bit strings (from release 8.32), by means of +two additional libraries. They can be built as well as, or instead of, the +8-bit library. To avoid too much complication, this document describes the +8-bit versions of the functions, with only occasional references to the 16-bit +and 32-bit libraries. +</P> +<P> +The 16-bit and 32-bit functions operate in the same way as their 8-bit +counterparts; they just use different data types for their arguments and +results, and their names start with <b>pcre16_</b> or <b>pcre32_</b> instead of +<b>pcre_</b>. For every option that has UTF8 in its name (for example, +PCRE_UTF8), there are corresponding 16-bit and 32-bit names with UTF8 replaced +by UTF16 or UTF32, respectively. This facility is in fact just cosmetic; the +16-bit and 32-bit option names define the same bit values. +</P> +<P> +References to bytes and UTF-8 in this document should be read as references to +16-bit data units and UTF-16 when using the 16-bit library, or 32-bit data +units and UTF-32 when using the 32-bit library, unless specified otherwise. +More details of the specific differences for the 16-bit and 32-bit libraries +are given in the +<a href="pcre16.html"><b>pcre16</b></a> +and +<a href="pcre32.html"><b>pcre32</b></a> +pages. +</P> +<br><a name="SEC6" href="#TOC1">PCRE API OVERVIEW</a><br> +<P> +PCRE has its own native API, which is described in this document. There are +also some wrapper functions (for the 8-bit library only) that correspond to the +POSIX regular expression API, but they do not give access to all the +functionality. They are described in the +<a href="pcreposix.html"><b>pcreposix</b></a> +documentation. Both of these APIs define a set of C function calls. A C++ +wrapper (again for the 8-bit library only) is also distributed with PCRE. It is +documented in the +<a href="pcrecpp.html"><b>pcrecpp</b></a> +page. +</P> +<P> +The native API C function prototypes are defined in the header file +<b>pcre.h</b>, and on Unix-like systems the (8-bit) 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> +In a Windows environment, if you want to statically link an application program +against a non-dll <b>pcre.a</b> file, you must define PCRE_STATIC before +including <b>pcre.h</b> or <b>pcrecpp.h</b>, because otherwise the +<b>pcre_malloc()</b> and <b>pcre_free()</b> exported functions will be declared +<b>__declspec(dllimport)</b>, with unwanted results. +</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 PCRE +source distribution. A listing of this program is given in the +<a href="pcredemo.html"><b>pcredemo</b></a> +documentation, and the +<a href="pcresample.html"><b>pcresample</b></a> +documentation describes how to compile and run it. +</P> +<P> +Just-in-time compiler support is an optional feature of PCRE that can be built +in appropriate hardware environments. It greatly speeds up the matching +performance of many patterns. Simple programs can easily request that it be +used if available, by setting an option that is ignored when it is not +relevant. More complicated programs might need to make use of the functions +<b>pcre_jit_stack_alloc()</b>, <b>pcre_jit_stack_free()</b>, and +<b>pcre_assign_jit_stack()</b> in order to control the JIT code's memory usage. +</P> +<P> +From release 8.32 there is also a direct interface for JIT execution, which +gives improved performance. The JIT-specific functions are discussed in the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation. +</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. The alternative algorithm finds all possible matches (at a given +point in the subject), and scans the subject just once (unless there are +lookbehind assertions). 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> + <b>pcre_get_stringnumber()</b> + <b>pcre_get_stringtable_entries()</b> +</pre> +<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 to build a set of character tables +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. 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, +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. See the +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation for details of how to do this. It 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. There is a +discussion about PCRE's stack usage in the +<a href="pcrestack.html"><b>pcrestack</b></a> +documentation. +</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 +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation. +</P> +<P> +The global variable <b>pcre_stack_guard</b> initially contains NULL. It can be +set by the caller to a function that is called by PCRE whenever it starts +to compile a parenthesized part of a pattern. When parentheses are nested, PCRE +uses recursive function calls, which use up the system stack. This function is +provided so that applications with restricted stacks can force a compilation +error if the stack runs out. The function should return zero if all is well, or +non-zero to force an error. +<a name="newlines"></a></P> +<br><a name="SEC7" href="#TOC1">NEWLINES</a><br> +<P> +PCRE supports five different conventions for indicating line breaks in +strings: a single CR (carriage return) character, a single LF (linefeed) +character, the two-character sequence CRLF, any of the three preceding, or any +Unicode newline sequence. The Unicode newline sequences are the three just +mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed, +U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS +(paragraph separator, U+2029). +</P> +<P> +Each of the first three conventions is used by at least one operating system as +its standard newline sequence. When PCRE is built, a default can be specified. +The default default is LF, which is the Unix standard. When PCRE is run, the +default can be overridden, either when a pattern is compiled, or when it is +matched. +</P> +<P> +At compile time, the newline convention can be specified by the <i>options</i> +argument of <b>pcre_compile()</b>, or it can be specified by special text at the +start of the pattern itself; this overrides any other settings. See the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +page for details of the special character sequences. +</P> +<P> +In the PCRE documentation the word "newline" is used to mean "the character or +pair of characters that indicate a line break". The choice of newline +convention affects the handling of the dot, circumflex, and dollar +metacharacters, the handling of #-comments in /x mode, and, when CRLF is a +recognized line ending sequence, the match position advancement for a +non-anchored pattern. There is more detail about this in the +<a href="#execoptions">section on <b>pcre_exec()</b> options</a> +below. +</P> +<P> +The choice of newline convention does not affect the interpretation of +the \n or \r escape sequences, nor does it affect what \R matches, which is +controlled in a similar way, but by separate options. +</P> +<br><a name="SEC8" 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>, +<b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the +callout and stack-checking functions pointed to by <b>pcre_callout</b> and +<b>pcre_stack_guard</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> +<P> +If the just-in-time optimization feature is being used, it needs separate +memory stack areas for each thread. See the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation for more details. +</P> +<br><a name="SEC9" 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, which includes a description of the +<b>pcre_pattern_to_host_byte_order()</b> function. However, compiling a regular +expression with one version of PCRE for use with a different version is not +guaranteed to work and may cause crashes. +</P> +<br><a name="SEC10" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br> +<P> +<b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b> +</P> +<P> +The function <b>pcre_config()</b> makes it possible for a PCRE client to +discover which optional features have been compiled into the PCRE library. The +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation has more details about these optional features. +</P> +<P> +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 returned value is zero on success, or the +negative error code PCRE_ERROR_BADOPTION if the value in the first argument is +not recognized. The following information is available: +<pre> + PCRE_CONFIG_UTF8 +</pre> +The output is an integer that is set to one if UTF-8 support is available; +otherwise it is set to zero. This value should normally be given to the 8-bit +version of this function, <b>pcre_config()</b>. If it is given to the 16-bit +or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION. +<pre> + PCRE_CONFIG_UTF16 +</pre> +The output is an integer that is set to one if UTF-16 support is available; +otherwise it is set to zero. This value should normally be given to the 16-bit +version of this function, <b>pcre16_config()</b>. If it is given to the 8-bit +or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION. +<pre> + PCRE_CONFIG_UTF32 +</pre> +The output is an integer that is set to one if UTF-32 support is available; +otherwise it is set to zero. This value should normally be given to the 32-bit +version of this function, <b>pcre32_config()</b>. If it is given to the 8-bit +or 16-bit version of this function, the result is PCRE_ERROR_BADOPTION. +<pre> + 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_JIT +</pre> +The output is an integer that is set to one if support for just-in-time +compiling is available; otherwise it is set to zero. +<pre> + PCRE_CONFIG_JITTARGET +</pre> +The output is a pointer to a zero-terminated "const char *" string. If JIT +support is available, the string contains the name of the architecture for +which the JIT compiler is configured, for example "x86 32bit (little endian + +unaligned)". If JIT support is not available, the result is NULL. +<pre> + PCRE_CONFIG_NEWLINE +</pre> +The output is an integer whose value specifies the default character sequence +that is recognized as meaning "newline". The values that are supported in +ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for +ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, ANYCRLF, and ANY yield the +same values. However, the value for LF is normally 21, though some EBCDIC +environments use 37. The corresponding values for CRLF are 3349 and 3365. The +default should normally correspond to the standard sequence for your operating +system. +<pre> + PCRE_CONFIG_BSR +</pre> +The output is an integer whose value indicates what character sequences the \R +escape sequence matches by default. A value of 0 means that \R matches any +Unicode line ending sequence; a value of 1 means that \R matches only CR, LF, +or CRLF. The default can be overridden when a pattern is compiled or matched. +<pre> + PCRE_CONFIG_LINK_SIZE +</pre> +The output is an integer that contains the number of bytes used for internal +linkage in compiled regular expressions. For the 8-bit library, the value can +be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still +a number of bytes. For the 32-bit library, the value is either 2 or 4 and is +still a number of bytes. 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. Larger values allow larger regular expressions to be compiled, at the +expense of slower matching. +<pre> + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD +</pre> +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 +<a href="pcreposix.html"><b>pcreposix</b></a> +documentation. +<pre> + PCRE_CONFIG_PARENS_LIMIT +</pre> +The output is a long integer that gives the maximum depth of nesting of +parentheses (of any kind) in a pattern. This limit is imposed to cap the amount +of system stack used when a pattern is compiled. It is specified when PCRE is +built; the default is 250. This limit does not take into account the stack that +may already be used by the calling application. For finer control over +compilation stack usage, you can set a pointer to an external checking function +in <b>pcre_stack_guard</b>. +<pre> + PCRE_CONFIG_MATCH_LIMIT +</pre> +The output is a long 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_MATCH_LIMIT_RECURSION +</pre> +The output is a long integer that gives the default limit for the depth of +recursion when calling the internal matching function 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="SEC11" 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> +<br> +<br> +<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> +Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be +called to compile a pattern into an internal form. The only difference between +the two interfaces is that <b>pcre_compile2()</b> has an additional argument, +<i>errorcodeptr</i>, via which a numerical error code can be returned. To avoid +too much repetition, we refer just to <b>pcre_compile()</b> below, but the +information applies equally to <b>pcre_compile2()</b>. +</P> +<P> +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 (via <b>pcre_free</b>) 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 may contain a copy of the <i>tableptr</i> +argument, which is an address (see below). +</P> +<P> +The <i>options</i> 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 some others as well) can also be set and unset from +within the pattern (see the detailed description in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation). For those options that can be different in different parts of +the pattern, the contents of the <i>options</i> argument specifies their +settings at the start of compilation and execution. The PCRE_ANCHORED, +PCRE_BSR_<i>xxx</i>, PCRE_NEWLINE_<i>xxx</i>, PCRE_NO_UTF8_CHECK, and +PCRE_NO_START_OPTIMIZE options 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. +Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns +NULL, and sets the variable pointed to by <i>errptr</i> 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. Normally, the offset from the start of the pattern to the +data unit that was being processed when the error was discovered is placed in +the variable pointed to by <i>erroffset</i>, which must not be NULL (if it is, +an immediate error is given). However, for an invalid UTF-8 or UTF-16 string, +the offset is that of the first data unit of the failing character. +</P> +<P> +Some errors are not detected until the whole pattern has been scanned; in these +cases, the offset passed back is the length of the pattern. Note that the +offset is in data units, not characters, even in a UTF mode. It may sometimes +point into the middle of a UTF-8 or UTF-16 character. +</P> +<P> +If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the +<i>errorcodeptr</i> argument is not NULL, a non-zero error code number is +returned via this argument in the event of an error. This is in addition to the +textual error message. Error codes and messages are listed below. +</P> +<P> +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> and <b>pcre_dfa_exec()</b> when the +pattern is matched. 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; + int erroffset; + re = pcre_compile( + "^A.*Z", /* the pattern */ + 0, /* default options */ + &error, /* for error message */ + &erroffset, /* for error offset */ + NULL); /* use default character tables */ +</pre> +The following names for option bits are defined in the <b>pcre.h</b> header +file: +<pre> + PCRE_ANCHORED +</pre> +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 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. +<pre> + 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_BSR_ANYCRLF + PCRE_BSR_UNICODE +</pre> +These options (which are mutually exclusive) control what the \R escape +sequence matches. The choice is either to match only CR, LF, or CRLF, or to +match any Unicode newline sequence. The default is specified when PCRE is +built. It can be overridden from within the pattern, or by setting an option +when a compiled pattern is matched. +<pre> + PCRE_CASELESS +</pre> +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. In UTF-8 mode, PCRE always understands the +concept of case for characters whose values are less than 128, so caseless +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> +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 a newline at the end of the string (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. +<pre> + PCRE_DOTALL +</pre> +If this bit is set, a dot metacharacter in the pattern matches a character of +any value, including one that indicates a newline. However, it only ever +matches one character, even if newlines are coded as CRLF. Without this option, +a dot does not match when the current position is at a newline. 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 newline +characters, independent of the setting of this option. +<pre> + PCRE_DUPNAMES +</pre> +If this bit is set, names used to identify capturing subpatterns need not be +unique. This can be helpful for certain types of pattern when it is known that +only one instance of the named subpattern can ever be matched. There are more +details of named subpatterns below; see also the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. +<pre> + PCRE_EXTENDED +</pre> +If this bit is set, most white space characters in the pattern are totally +ignored except when escaped or inside a character class. However, white space +is not allowed within sequences such as (?> that introduce various +parenthesized subpatterns, nor within a numerical quantifier such as {1,3}. +However, ignorable white space is permitted between an item and a following +quantifier and between a quantifier and a following + that indicates +possessiveness. +</P> +<P> +White space did not used to include the VT character (code 11), because Perl +did not treat this character as white space. However, Perl changed at release +5.18, so PCRE followed at release 8.34, and VT is now treated as white space. +</P> +<P> +PCRE_EXTENDED also causes characters between an unescaped # outside a character +class and the next newline, inclusive, to be ignored. PCRE_EXTENDED is +equivalent to Perl's /x option, and it can be changed within a pattern by a +(?x) option setting. +</P> +<P> +Which characters are interpreted as newlines is controlled by the options +passed to <b>pcre_compile()</b> or by a special sequence at the start of the +pattern, as described in the section entitled +<a href="pcrepattern.html#newlines">"Newline conventions"</a> +in the <b>pcrepattern</b> documentation. Note that the end of this type of +comment is a literal newline sequence in the pattern; escape sequences that +happen to represent a newline do not count. +</P> +<P> +This option makes it possible to include comments inside complicated patterns. +Note, however, that this applies only to data characters. White space characters +may never appear within special character sequences in a pattern, for example +within the sequence (?( that introduces a conditional subpattern. +<pre> + PCRE_EXTRA +</pre> +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 +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 an error for this, by running it with the -w option.) There are at present +no other features controlled by this option. It can also be set by a (?X) +option setting within a pattern. +<pre> + PCRE_FIRSTLINE +</pre> +If this option is set, an unanchored pattern is required to match before or at +the first newline in the subject string, though the matched text may continue +over the newline. +<pre> + PCRE_JAVASCRIPT_COMPAT +</pre> +If this option is set, PCRE's behaviour is changed in some ways so that it is +compatible with JavaScript rather than Perl. The changes are as follows: +</P> +<P> +(1) A lone closing square bracket in a pattern causes a compile-time error, +because this is illegal in JavaScript (by default it is treated as a data +character). Thus, the pattern AB]CD becomes illegal when this option is set. +</P> +<P> +(2) At run time, a back reference to an unset subpattern group matches an empty +string (by default this causes the current matching alternative to fail). A +pattern such as (\1)(a) succeeds when this option is set (assuming it can find +an "a" in the subject), whereas it fails by default, for Perl compatibility. +</P> +<P> +(3) \U matches an upper case "U" character; by default \U causes a compile +time error (Perl uses \U to upper case subsequent characters). +</P> +<P> +(4) \u matches a lower case "u" character unless it is followed by four +hexadecimal digits, in which case the hexadecimal number defines the code point +to match. By default, \u causes a compile time error (Perl uses it to upper +case the following character). +</P> +<P> +(5) \x matches a lower case "x" character unless it is followed by two +hexadecimal digits, in which case the hexadecimal number defines the code point +to match. By default, as in Perl, a hexadecimal number is always expected after +\x, but it may have zero, one, or two digits (so, for example, \xz matches a +binary zero character followed by z). +<pre> + PCRE_MULTILINE +</pre> +By default, for the purposes of matching "start of line" and "end of line", +PCRE treats the subject string as consisting of a single line of characters, +even if it actually contains newlines. The "start of line" metacharacter (^) +matches only at the start of the string, and the "end of line" metacharacter +($) matches only at the end of the string, or before a terminating newline +(except when PCRE_DOLLAR_ENDONLY is set). Note, however, that unless +PCRE_DOTALL is set, the "any character" metacharacter (.) does not match at a +newline. This behaviour (for ^, $, and dot) is the same as Perl. +</P> +<P> +When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs +match immediately following or immediately before internal newlines in the +subject string, respectively, as well as at the very start and end. This is +equivalent to Perl's /m option, and it can be changed within a pattern by a +(?m) option setting. If there are no newlines in a subject string, or no +occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect. +<pre> + PCRE_NEVER_UTF +</pre> +This option locks out interpretation of the pattern as UTF-8 (or UTF-16 or +UTF-32 in the 16-bit and 32-bit libraries). In particular, it prevents the +creator of the pattern from switching to UTF interpretation by starting the +pattern with (*UTF). This may be useful in applications that process patterns +from external sources. The combination of PCRE_UTF8 and PCRE_NEVER_UTF also +causes an error. +<pre> + PCRE_NEWLINE_CR + PCRE_NEWLINE_LF + PCRE_NEWLINE_CRLF + PCRE_NEWLINE_ANYCRLF + PCRE_NEWLINE_ANY +</pre> +These options override the default newline definition that was chosen when PCRE +was built. Setting the first or the second specifies that a newline is +indicated by a single character (CR or LF, respectively). Setting +PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character +CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three +preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies +that any Unicode newline sequence should be recognized. +</P> +<P> +In an ASCII/Unicode environment, the Unicode newline sequences are the three +just mentioned, plus the single characters VT (vertical tab, U+000B), FF (form +feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS +(paragraph separator, U+2029). For the 8-bit library, the last two are +recognized only in UTF-8 mode. +</P> +<P> +When PCRE is compiled to run in an EBCDIC (mainframe) environment, the code for +CR is 0x0d, the same as ASCII. However, the character code for LF is normally +0x15, though in some EBCDIC environments 0x25 is used. Whichever of these is +not LF is made to correspond to Unicode's NEL character. EBCDIC codes are all +less than 256. For more details, see the +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation. +</P> +<P> +The newline setting in the options word uses three bits that are treated +as a number, giving eight possibilities. Currently only six are used (default +plus the five values above). This means that if you set more than one newline +option, the combination may or may not be sensible. For example, +PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but +other combinations may yield unused numbers and cause an error. +</P> +<P> +The only time that a line break in a pattern is specially recognized when +compiling is when PCRE_EXTENDED is set. CR and LF are white space characters, +and so are ignored in this mode. Also, an unescaped # outside a character class +indicates a comment that lasts until after the next line break sequence. In +other circumstances, line break sequences in patterns are treated as literal +data. +</P> +<P> +The newline option that is set at compile time becomes the default that is used +for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden. +<pre> + PCRE_NO_AUTO_CAPTURE +</pre> +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. +<pre> + PCRE_NO_AUTO_POSSESS +</pre> +If this option is set, it disables "auto-possessification". This is an +optimization that, for example, turns a+b into a++b in order to avoid +backtracks into a+ that can never be successful. However, if callouts are in +use, auto-possessification means that some of them are never taken. You can set +this option if you want the matching functions to do a full unoptimized search +and run all the callouts, but it is mainly provided for testing purposes. +<pre> + PCRE_NO_START_OPTIMIZE +</pre> +This is an option that acts at matching time; that is, it is really an option +for <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. If it is set at compile time, +it is remembered with the compiled pattern and assumed at matching time. This +is necessary if you want to use JIT execution, because the JIT compiler needs +to know whether or not this option is set. For details see the discussion of +PCRE_NO_START_OPTIMIZE +<a href="#execoptions">below.</a> +<pre> + PCRE_UCP +</pre> +This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W, +\w, 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 +<a href="pcre.html#genericchartypes">generic character types</a> +in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +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. +<pre> + PCRE_UNGREEDY +</pre> +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. +<pre> + PCRE_UTF8 +</pre> +This option causes PCRE to regard both the pattern and the subject as strings +of UTF-8 characters instead of single-byte strings. However, it is available +only when PCRE is built to include UTF 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="pcreunicode.html"><b>pcreunicode</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. There is a discussion about the +<a href="pcreunicode.html#utf8strings">validity of UTF-8 strings</a> +in the +<a href="pcreunicode.html"><b>pcreunicode</b></a> +page. If an invalid UTF-8 sequence 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 or loop. Note that this option +can also be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress +the validity checking of subject strings only. If the same string is being +matched many times, the option can be safely set for the second and subsequent +matchings to improve performance. +</P> +<br><a name="SEC12" 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. Note that error messages are always 8-bit ASCII +strings, even in 16-bit or 32-bit mode. As PCRE has developed, some error codes +have fallen out of use. To avoid confusion, they have not been re-used. +<pre> + 0 no error + 1 \ at end of pattern + 2 \c at end of pattern + 3 unrecognized character follows \ + 4 numbers out of order in {} quantifier + 5 number too big in {} quantifier + 6 missing terminating ] for character class + 7 invalid escape sequence in character class + 8 range out of order in character class + 9 nothing to repeat + 10 [this code is not in use] + 11 internal error: unexpected repeat + 12 unrecognized character after (? or (?- + 13 POSIX named classes are supported only within a class + 14 missing ) + 15 reference to non-existent subpattern + 16 erroffset passed as NULL + 17 unknown option bit(s) set + 18 missing ) after comment + 19 [this code is not in use] + 20 regular expression is too large + 21 failed to get memory + 22 unmatched parentheses + 23 internal error: code overflow + 24 unrecognized character after (?< + 25 lookbehind assertion is not fixed length + 26 malformed number or name after (?( + 27 conditional group contains more than two branches + 28 assertion expected after (?( + 29 (?R or (?[+-]digits must be followed by ) + 30 unknown POSIX class name + 31 POSIX collating elements are not supported + 32 this version of PCRE is compiled without UTF support + 33 [this code is not in use] + 34 character value in \x{} or \o{} is too large + 35 invalid condition (?(0) + 36 \C not allowed in lookbehind assertion + 37 PCRE does not support \L, \l, \N{name}, \U, or \u + 38 number after (?C is > 255 + 39 closing ) for (?C expected + 40 recursive call could loop indefinitely + 41 unrecognized character after (?P + 42 syntax error in subpattern name (missing terminator) + 43 two named subpatterns have the same name + 44 invalid UTF-8 string (specifically UTF-8) + 45 support for \P, \p, and \X has not been compiled + 46 malformed \P or \p sequence + 47 unknown property name after \P or \p + 48 subpattern name is too long (maximum 32 characters) + 49 too many named subpatterns (maximum 10000) + 50 [this code is not in use] + 51 octal value is greater than \377 in 8-bit non-UTF-8 mode + 52 internal error: overran compiling workspace + 53 internal error: previously-checked referenced subpattern + not found + 54 DEFINE group contains more than one branch + 55 repeating a DEFINE group is not allowed + 56 inconsistent NEWLINE options + 57 \g is not followed by a braced, angle-bracketed, or quoted + name/number or by a plain number + 58 a numbered reference must not be zero + 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT) + 60 (*VERB) not recognized or malformed + 61 number is too big + 62 subpattern name expected + 63 digit expected after (?+ + 64 ] is an invalid data character in JavaScript compatibility mode + 65 different names for subpatterns of the same number are + not allowed + 66 (*MARK) must have an argument + 67 this version of PCRE is not compiled with Unicode property + support + 68 \c must be followed by an ASCII character + 69 \k is not followed by a braced, angle-bracketed, or quoted name + 70 internal error: unknown opcode in find_fixedlength() + 71 \N is not supported in a class + 72 too many forward references + 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff) + 74 invalid UTF-16 string (specifically UTF-16) + 75 name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN) + 76 character value in \u.... sequence is too large + 77 invalid UTF-32 string (specifically UTF-32) + 78 setting UTF is disabled by the application + 79 non-hex character in \x{} (closing brace missing?) + 80 non-octal character in \o{} (closing brace missing?) + 81 missing opening brace after \o + 82 parentheses are too deeply nested + 83 invalid range in character class + 84 group name must start with a non-digit + 85 parentheses are too deeply nested (stack check) +</pre> +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. +<a name="studyingapattern"></a></P> +<br><a name="SEC13" href="#TOC1">STUDYING A PATTERN</a><br> +<P> +<b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>);</b> +</P> +<P> +If a compiled pattern is going to be used several times, it is worth spending +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 studying the pattern produces additional information that will +help speed up matching, <b>pcre_study()</b> returns a pointer to a +<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 <b>pcre_study()</b> can be passed directly to +<b>pcre_exec()</b> or <b>pcre_dfa_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 +<a href="#extradata">below</a> +in the section on matching a pattern. +</P> +<P> +If studying the pattern does not produce any useful information, +<b>pcre_study()</b> returns NULL by default. In that circumstance, if the +calling program wants to pass any of the other fields to <b>pcre_exec()</b> or +<b>pcre_dfa_exec()</b>, it must set up its own <b>pcre_extra</b> block. However, +if <b>pcre_study()</b> is called with the PCRE_STUDY_EXTRA_NEEDED option, it +returns a <b>pcre_extra</b> block even if studying did not find any additional +information. It may still return NULL, however, if an error occurs in +<b>pcre_study()</b>. +</P> +<P> +The second argument of <b>pcre_study()</b> contains option bits. There are three +further options in addition to PCRE_STUDY_EXTRA_NEEDED: +<pre> + PCRE_STUDY_JIT_COMPILE + PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE + PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE +</pre> +If any of these are set, and the just-in-time compiler is available, the +pattern is further compiled into machine code that executes much faster than +the <b>pcre_exec()</b> interpretive matching function. If the just-in-time +compiler is not available, these options are ignored. All undefined bits in the +<i>options</i> argument must be zero. +</P> +<P> +JIT compilation is a heavyweight optimization. It can take some time for +patterns to be analyzed, and for one-off matches and simple patterns the +benefit of faster execution might be offset by a much slower study time. +Not all patterns can be optimized by the JIT compiler. For those that cannot be +handled, matching automatically falls back to the <b>pcre_exec()</b> +interpreter. For more details, see the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation. +</P> +<P> +The third argument for <b>pcre_study()</b> is a pointer for an error message. If +studying succeeds (even if no data is returned), the variable it points to is +set to NULL. Otherwise it is set 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. You +should test the error pointer for NULL after calling <b>pcre_study()</b>, to be +sure that it has run successfully. +</P> +<P> +When you are finished with a pattern, you can free the memory used for the +study data by calling <b>pcre_free_study()</b>. This function was added to the +API for release 8.20. For earlier versions, the memory could be freed with +<b>pcre_free()</b>, just like the pattern itself. This will still work in cases +where JIT optimization is not used, but it is advisable to change to the new +function when convenient. +</P> +<P> +This is a typical way in which <b>pcre_study</b>() is used (except that in a +real application there should be tests for errors): +<pre> + int rc; + pcre *re; + pcre_extra *sd; + re = pcre_compile("pattern", 0, &error, &erroroffset, NULL); + sd = pcre_study( + re, /* result of pcre_compile() */ + 0, /* no options */ + &error); /* set to NULL or points to a message */ + rc = pcre_exec( /* see below for details of pcre_exec() options */ + re, sd, "subject", 7, 0, 0, ovector, 30); + ... + pcre_free_study(sd); + pcre_free(re); +</pre> +Studying a pattern does two things: first, a lower bound for the length of +subject string that is needed to match the pattern is computed. This does not +mean that there are any strings of that length that match, but it does +guarantee that no shorter strings match. The value is used 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 <b>pcre_fullinfo()</b> function. +</P> +<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. (In 16-bit mode, the bitmap is used for 16-bit values less than 256. +In 32-bit mode, the bitmap is used for 32-bit values less than 256.) +</P> +<P> +These two optimizations apply to both <b>pcre_exec()</b> and +<b>pcre_dfa_exec()</b>, and the information is also used by the JIT compiler. +The optimizations can be disabled by setting the PCRE_NO_START_OPTIMIZE option. +You might want to do this if your pattern contains callouts or (*MARK) and you +want to make use of these facilities in cases where matching fails. +</P> +<P> +PCRE_NO_START_OPTIMIZE can be specified at either compile time or execution +time. However, if PCRE_NO_START_OPTIMIZE is passed to <b>pcre_exec()</b>, (that +is, after any JIT compilation has happened) JIT execution is disabled. For JIT +execution to work with PCRE_NO_START_OPTIMIZE, the option must be set at +compile time. +</P> +<P> +There is a longer discussion of PCRE_NO_START_OPTIMIZE +<a href="#execoptions">below.</a> +<a name="localesupport"></a></P> +<br><a name="SEC14" href="#TOC1">LOCALE SUPPORT</a><br> +<P> +PCRE handles caseless matching, and determines whether characters are letters, +digits, or whatever, by reference to a set of tables, indexed by character +code point. When running in UTF-8 mode, or in the 16- or 32-bit libraries, this +applies only to characters with code points less than 256. By default, +higher-valued code points never match escapes such as \w or \d. However, if +PCRE is built with Unicode property support, all characters can be tested with +\p and \P, or, alternatively, the PCRE_UCP option can be set when a pattern +is compiled; this causes \w and friends to use Unicode property support +instead of the built-in tables. +</P> +<P> +The use of locales with Unicode is discouraged. If you are handling characters +with code points greater than 128, you should either use Unicode support, or +use locales, but not try to mix the two. +</P> +<P> +PCRE contains an internal set of tables that are used when the final argument +of <b>pcre_compile()</b> is NULL. These are sufficient for many applications. +Normally, the internal tables recognize only ASCII characters. However, when +PCRE is built, it is possible to cause the internal tables to be rebuilt in the +default "C" locale of the local system, which may cause them to be different. +</P> +<P> +The internal tables can always be overridden by tables supplied by the +application that calls PCRE. These may be created in a different locale from +the default. As more and more applications change to using Unicode, the need +for 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> 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_FR"); + tables = pcre_maketables(); + re = pcre_compile(..., tables); +</pre> +The locale name "fr_FR" is used on Linux and other Unix-like systems; if you +are using Windows, the name for the French locale is "french". +</P> +<P> +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 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 also by <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>. Thus, for any single +pattern, compilation, studying and matching all happen in the same locale, but +different patterns can be processed in different locales. +</P> +<P> +It is possible to pass a table pointer or NULL (indicating the use of the +internal tables) to <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b> (see the +discussion below in the section on matching a pattern). This facility is +provided for use with pre-compiled patterns that have been saved and reloaded. +Character tables are not saved with patterns, so if a non-standard table was +used at compile time, it must be provided again when the reloaded pattern is +matched. Attempting to use this facility to match a pattern in a different +locale from the one in which it was compiled is likely to lead to anomalous +(usually incorrect) results. +<a name="infoaboutpattern"></a></P> +<br><a name="SEC15" 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> +</P> +<P> +The <b>pcre_fullinfo()</b> function returns information about a compiled +pattern. It replaces the <b>pcre_info()</b> function, which was removed from the +library at version 8.30, after more than 10 years of obsolescence. +</P> +<P> +The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled +pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if +the pattern was not studied. The third argument specifies which piece of +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: +<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_BADENDIANNESS the pattern was compiled with different + endianness + PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid + PCRE_ERROR_UNSET the requested field is not set +</pre> +The "magic number" is placed at the start of each compiled pattern as an simple +check against passing an arbitrary memory pointer. The endianness error can +occur if a compiled pattern is saved and reloaded on a different host. Here is +a typical call of <b>pcre_fullinfo()</b>, to obtain the length of the compiled +pattern: +<pre> + int rc; + size_t length; + rc = pcre_fullinfo( + re, /* result of pcre_compile() */ + sd, /* result of pcre_study(), or NULL */ + PCRE_INFO_SIZE, /* what is required */ + &length); /* where to put the data */ +</pre> +The possible values for the third argument are defined in <b>pcre.h</b>, and are +as follows: +<pre> + PCRE_INFO_BACKREFMAX +</pre> +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. +<pre> + PCRE_INFO_CAPTURECOUNT +</pre> +Return the number of capturing subpatterns in the pattern. The fourth argument +should point to an <b>int</b> variable. +<pre> + 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 (deprecated) +</pre> +Return information about the first data unit of any matched string, for a +non-anchored pattern. The name of this option refers to the 8-bit library, +where data units are bytes. The fourth argument should point to an <b>int</b> +variable. Negative values are used for special cases. However, this means that +when the 32-bit library is in non-UTF-32 mode, the full 32-bit range of +characters cannot be returned. For this reason, this value is deprecated; use +PCRE_INFO_FIRSTCHARACTERFLAGS and PCRE_INFO_FIRSTCHARACTER instead. +</P> +<P> +If there is a fixed first value, for example, the letter "c" from a pattern +such as (cat|cow|coyote), its value is returned. In the 8-bit library, the +value is always less than 256. In the 16-bit library the value can be up to +0xffff. In the 32-bit library the value can be up to 0x10ffff. +</P> +<P> +If there is no fixed first value, and if either +<br> +<br> +(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch +starts with "^", or +<br> +<br> +(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set +(if it were set, the pattern would be anchored), +<br> +<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. +<pre> + PCRE_INFO_FIRSTCHARACTER +</pre> +Return the value of the first data unit (non-UTF character) of any matched +string in the situation where PCRE_INFO_FIRSTCHARACTERFLAGS returns 1; +otherwise return 0. The fourth argument should point to an <b>uint_t</b> +variable. +</P> +<P> +In the 8-bit library, the value is always less than 256. In the 16-bit library +the value can be up to 0xffff. In the 32-bit library in UTF-32 mode the value +can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32 mode. +<pre> + PCRE_INFO_FIRSTCHARACTERFLAGS +</pre> +Return information about the first data unit of any matched string, for a +non-anchored pattern. The fourth argument should point to an <b>int</b> +variable. +</P> +<P> +If there is a fixed first value, for example, the letter "c" from a pattern +such as (cat|cow|coyote), 1 is returned, and the character value can be +retrieved using PCRE_INFO_FIRSTCHARACTER. If there is no fixed first value, and +if either +<br> +<br> +(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch +starts with "^", or +<br> +<br> +(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set +(if it were set, the pattern would be anchored), +<br> +<br> +2 is returned, indicating that the pattern matches only at the start of a +subject string or after any newline within the string. Otherwise 0 is +returned. For anchored patterns, 0 is returned. +<pre> + PCRE_INFO_FIRSTTABLE +</pre> +If the pattern was studied, and this resulted in the construction of a 256-bit +table indicating a fixed set of values for the first data unit 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. +<pre> + PCRE_INFO_HASCRORLF +</pre> +Return 1 if the pattern contains any explicit matches for CR or LF characters, +otherwise 0. The fourth argument should point to an <b>int</b> variable. An +explicit match is either a literal CR or LF character, or \r or \n. +<pre> + PCRE_INFO_JCHANGED +</pre> +Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise +0. The fourth argument should point to an <b>int</b> variable. (?J) and +(?-J) set and unset the local PCRE_DUPNAMES option, respectively. +<pre> + PCRE_INFO_JIT +</pre> +Return 1 if the pattern was studied with one of the JIT options, and +just-in-time compiling was successful. The fourth argument should point to an +<b>int</b> variable. A return value of 0 means that JIT support is not available +in this version of PCRE, or that the pattern was not studied with a JIT option, +or that the JIT compiler could not handle this particular pattern. See the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation for details of what can and cannot be handled. +<pre> + PCRE_INFO_JITSIZE +</pre> +If the pattern was successfully studied with a JIT option, return the size of +the JIT compiled code, otherwise return zero. The fourth argument should point +to a <b>size_t</b> variable. +<pre> + PCRE_INFO_LASTLITERAL +</pre> +Return the value of the rightmost literal data unit that must exist in any +matched string, other than at its start, if such a value has been recorded. The +fourth argument should point to an <b>int</b> variable. If there is no such +value, -1 is returned. For anchored patterns, a last literal value is recorded +only if it 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> +Since for the 32-bit library using the non-UTF-32 mode, this function is unable +to return the full 32-bit range of characters, this value is deprecated; +instead the PCRE_INFO_REQUIREDCHARFLAGS and PCRE_INFO_REQUIREDCHAR values should +be used. +<pre> + PCRE_INFO_MATCH_EMPTY +</pre> +Return 1 if the pattern can match an empty string, otherwise 0. The fourth +argument should point to an <b>int</b> variable. +<pre> + PCRE_INFO_MATCHLIMIT +</pre> +If the pattern set a match limit by including an item of the form +(*LIMIT_MATCH=nnnn) at the start, the value is returned. The fourth argument +should point to an unsigned 32-bit integer. If no such value has been set, the +call to <b>pcre_fullinfo()</b> returns the error PCRE_ERROR_UNSET. +<pre> + PCRE_INFO_MAXLOOKBEHIND +</pre> +Return the number of characters (NB not data units) in the longest lookbehind +assertion in the pattern. This information is useful when doing multi-segment +matching using the partial matching facilities. Note that the simple assertions +\b and \B require a one-character lookbehind. \A also registers a +one-character lookbehind, though it does not actually inspect the previous +character. This is to ensure that at least one character from the old segment +is retained when a new segment is processed. Otherwise, if there are no +lookbehinds in the pattern, \A might match incorrectly at the start of a new +segment. +<pre> + PCRE_INFO_MINLENGTH +</pre> +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, which in UTF mode may be different from the +number of data units. The fourth argument should point to an <b>int</b> +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. +<pre> + PCRE_INFO_NAMECOUNT + PCRE_INFO_NAMEENTRYSIZE + PCRE_INFO_NAMETABLE +</pre> +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 numbers. Several convenience functions such as +<b>pcre_get_named_substring()</b> are provided for extracting captured +substrings by name. It is also possible to extract the data directly, by first +converting the name to a number in order to access the correct pointers in the +output vector (described with <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 +the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each +entry; both of these return an <b>int</b> value. The entry size depends on the +length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first +entry of the table. This is a pointer to <b>char</b> in the 8-bit library, where +the first two bytes of each entry are the number of the capturing parenthesis, +most significant byte first. In the 16-bit library, the pointer points to +16-bit data units, the first of which contains the parenthesis number. In the +32-bit library, the pointer points to 32-bit data units, the first of which +contains the parenthesis number. The rest of the entry is the corresponding +name, zero terminated. +</P> +<P> +The names are in alphabetical order. If (?| is used to create multiple groups +with the same number, as described in the +<a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a> +in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +page, the groups may be given the same name, but there is only one entry in the +table. Different names for groups of the same number are not permitted. +Duplicate names for subpatterns with different numbers are permitted, +but only if PCRE_DUPNAMES is set. 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> +<P> +As a simple example of the name/number table, consider the following pattern +after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white +space - including newlines - is ignored): +<pre> + (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) ) +</pre> +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 hexadecimal, and undefined bytes shown as ??: +<pre> + 00 01 d a t e 00 ?? + 00 05 d a y 00 ?? ?? + 00 04 m o n t h 00 + 00 02 y e a r 00 ?? +</pre> +When writing code to extract data from named subpatterns using the +name-to-number map, remember that the length of the entries is likely to be +different for each compiled pattern. +<pre> + PCRE_INFO_OKPARTIAL +</pre> +Return 1 if the pattern can be used for partial matching with +<b>pcre_exec()</b>, otherwise 0. The fourth argument should point to an +<b>int</b> variable. From release 8.00, this always returns 1, because the +restrictions that previously applied to partial matching have been lifted. The +<a href="pcrepartial.html"><b>pcrepartial</b></a> +documentation gives details of partial matching. +<pre> + PCRE_INFO_OPTIONS +</pre> +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 +top-level option settings at the start of the pattern itself. In other words, +they are the options that will be in force when matching starts. For example, +if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the +result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED. +</P> +<P> +A pattern is automatically anchored by PCRE if all of its top-level +alternatives begin with one of the following: +<pre> + ^ unless PCRE_MULTILINE is set + \A always + \G always + .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears +</pre> +For such patterns, the PCRE_ANCHORED bit is set in the options returned by +<b>pcre_fullinfo()</b>. +<pre> + PCRE_INFO_RECURSIONLIMIT +</pre> +If the pattern set a recursion limit by including an item of the form +(*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth +argument should point to an unsigned 32-bit integer. If no such value has been +set, the call to <b>pcre_fullinfo()</b> returns the error PCRE_ERROR_UNSET. +<pre> + PCRE_INFO_SIZE +</pre> +Return the size of the compiled pattern in bytes (for all three libraries). The +fourth argument should point to a <b>size_t</b> variable. This value does not +include the size of the <b>pcre</b> structure that is returned by +<b>pcre_compile()</b>. The value that is passed as the argument to +<b>pcre_malloc()</b> when <b>pcre_compile()</b> is getting memory in which to +place the compiled data is the value returned by this option plus the size of +the <b>pcre</b> structure. Studying a compiled pattern, with or without JIT, +does not alter the value returned by this option. +<pre> + PCRE_INFO_STUDYSIZE +</pre> +Return the size in bytes (for all three libraries) of the data block pointed to +by the <i>study_data</i> field in a <b>pcre_extra</b> block. If <b>pcre_extra</b> +is NULL, or there is no study data, zero is returned. The fourth argument +should point to a <b>size_t</b> variable. The <i>study_data</i> field is set by +<b>pcre_study()</b> to record information that will speed up matching (see the +section entitled +<a href="#studyingapattern">"Studying a pattern"</a> +above). The format of the <i>study_data</i> block is private, but its length +is made available via this option so that it can be saved and restored (see the +<a href="pcreprecompile.html"><b>pcreprecompile</b></a> +documentation for details). +<pre> + PCRE_INFO_REQUIREDCHARFLAGS +</pre> +Returns 1 if there is a rightmost literal data unit that must exist in any +matched string, other than at its start. The fourth argument should point to +an <b>int</b> variable. If there is no such value, 0 is returned. If returning +1, the character value itself can be retrieved using PCRE_INFO_REQUIREDCHAR. +</P> +<P> +For anchored patterns, a last literal value is recorded only if it follows +something of variable length. For example, for the pattern /^a\d+z\d+/ the +returned value 1 (with "z" returned from PCRE_INFO_REQUIREDCHAR), but for +/^a\dz\d/ the returned value is 0. +<pre> + PCRE_INFO_REQUIREDCHAR +</pre> +Return the value of the rightmost literal data unit that must exist in any +matched string, other than at its start, if such a value has been recorded. The +fourth argument should point to an <b>uint32_t</b> variable. If there is no such +value, 0 is returned. +</P> +<br><a name="SEC16" 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="SEC17" 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> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +</P> +<P> +The function <b>pcre_exec()</b> is called to match a subject string against a +compiled pattern, which is passed in the <i>code</i> argument. If the +pattern was studied, the result of the study should be passed in the +<i>extra</i> argument. You can call <b>pcre_exec()</b> with the same <i>code</i> +and <i>extra</i> arguments as many times as you like, in order to match +different subject strings with the same pattern. +</P> +<P> +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> +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]; + rc = pcre_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector of integers for substring information */ + 30); /* number of elements (NOT size in bytes) */ +<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 <b>pcre_extra</b> block contains the following +fields (not necessarily in this order): +<pre> + unsigned long int <i>flags</i>; + void *<i>study_data</i>; + void *<i>executable_jit</i>; + unsigned long int <i>match_limit</i>; + unsigned long int <i>match_limit_recursion</i>; + void *<i>callout_data</i>; + const unsigned char *<i>tables</i>; + unsigned char **<i>mark</i>; +</pre> +In the 16-bit version of this structure, the <i>mark</i> field has type +"PCRE_UCHAR16 **". +<br> +<br> +In the 32-bit version of this structure, the <i>mark</i> field has type +"PCRE_UCHAR32 **". +</P> +<P> +The <i>flags</i> field is used to specify which of the other fields are set. The +flag bits are: +<pre> + PCRE_EXTRA_CALLOUT_DATA + PCRE_EXTRA_EXECUTABLE_JIT + PCRE_EXTRA_MARK + PCRE_EXTRA_MATCH_LIMIT + PCRE_EXTRA_MATCH_LIMIT_RECURSION + PCRE_EXTRA_STUDY_DATA + PCRE_EXTRA_TABLES +</pre> +Other flag bits should be set to zero. The <i>study_data</i> field and sometimes +the <i>executable_jit</i> field are set in the <b>pcre_extra</b> block that is +returned by <b>pcre_study()</b>, together with the appropriate flag bits. You +should not set these yourself, but you may add to the block by setting 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 a pattern that uses nested unlimited repeats. +</P> +<P> +Internally, <b>pcre_exec()</b> uses a function called <b>match()</b>, which it +calls repeatedly (sometimes recursively). The limit set by <i>match_limit</i> is +imposed on the number of times this function is called during a match, which +has the effect of limiting the amount of backtracking that can take place. For +patterns that are not anchored, the count restarts from zero for each position +in the subject string. +</P> +<P> +When <b>pcre_exec()</b> is called with a pattern that was successfully studied +with a JIT option, the way that the matching is executed is entirely different. +However, there is still the possibility of runaway matching that goes on for a +very long time, and so the <i>match_limit</i> value is also used in this case +(but in a different way) to limit how long the matching can continue. +</P> +<P> +The default value for the limit can be set when PCRE is built; the default +default is 10 million, which handles all but the most extreme cases. You can +override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b> +block in which <i>match_limit</i> is set, 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> +A value for the match limit may also be supplied by an item at the start of a +pattern of the form +<pre> + (*LIMIT_MATCH=d) +</pre> +where d is a decimal number. However, such a setting is ignored unless d is +less than the limit set by the caller of <b>pcre_exec()</b> or, if no such limit +is set, less than the default. +</P> +<P> +The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but +instead of limiting the total number of times that <b>match()</b> is called, it +limits the depth of recursion. The recursion depth is a smaller number than the +total number of calls, because not all calls to <b>match()</b> are recursive. +This limit is of use only if it is set smaller than <i>match_limit</i>. +</P> +<P> +Limiting the recursion depth limits the amount of machine stack that can be +used, or, when PCRE has been compiled to use memory on the heap instead of the +stack, the amount of heap memory that can be used. This limit is not relevant, +and is ignored, when matching is done using JIT compiled code. +</P> +<P> +The default value for <i>match_limit_recursion</i> can be set when PCRE is +built; the default default is the same value as the default for +<i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b> +with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and +PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit +is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT. +</P> +<P> +A value for the recursion limit may also be supplied by an item at the start of +a pattern of the form +<pre> + (*LIMIT_RECURSION=d) +</pre> +where d is a decimal number. However, such a setting is ignored unless d is +less than the limit set by the caller of <b>pcre_exec()</b> or, if no such limit +is set, less than the default. +</P> +<P> +The <i>callout_data</i> field is used in conjunction with the "callout" feature, +and is described in the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation. +</P> +<P> +The <i>tables</i> field is provided for use with patterns that have been +pre-compiled using custom character tables, saved to disc or elsewhere, and +then reloaded, because the tables that were used to compile a pattern are not +saved with it. See the +<a href="pcreprecompile.html"><b>pcreprecompile</b></a> +documentation for a discussion of saving compiled patterns for later use. If +NULL is passed using this mechanism, it forces PCRE's internal tables to be +used. +</P> +<P> +<b>Warning:</b> The tables that <b>pcre_exec()</b> uses must be the same as those +that were used when the pattern was compiled. If this is not the case, the +behaviour of <b>pcre_exec()</b> is undefined. Therefore, when a pattern is +compiled and matched in the same process, this field should never be set. In +this (the most common) case, the correct table pointer is automatically passed +with the compiled pattern from <b>pcre_compile()</b> to <b>pcre_exec()</b>. +</P> +<P> +If PCRE_EXTRA_MARK is set in the <i>flags</i> field, the <i>mark</i> field must +be set to point to a suitable 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 <i>mark</i> 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 <i>mark</i> field is set to NULL. For details of the +backtracking control verbs, see the section entitled +<a href="pcrepattern#backtrackcontrol">"Backtracking control"</a> +in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. +<a name="execoptions"></a></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_NEWLINE_<i>xxx</i>, +PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, +PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and +PCRE_PARTIAL_SOFT. +</P> +<P> +If the pattern was successfully studied with one of the just-in-time (JIT) +compile options, the only supported options for JIT execution are +PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, +PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an +unsupported option is used, JIT execution is disabled and the normal +interpretive code in <b>pcre_exec()</b> is run. +<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_BSR_ANYCRLF + PCRE_BSR_UNICODE +</pre> +These options (which are mutually exclusive) control what the \R escape +sequence matches. The choice is either to match only CR, LF, or CRLF, or to +match any Unicode newline sequence. These options override the choice that was +made or defaulted when the pattern was compiled. +<pre> + PCRE_NEWLINE_CR + PCRE_NEWLINE_LF + PCRE_NEWLINE_CRLF + PCRE_NEWLINE_ANYCRLF + PCRE_NEWLINE_ANY +</pre> +These options override the newline definition that was chosen or defaulted when +the pattern was compiled. For details, see the description of +<b>pcre_compile()</b> above. During matching, the newline choice affects the +behaviour of the dot, circumflex, and dollar metacharacters. It may also alter +the way the match position is advanced after a match failure for an unanchored +pattern. +</P> +<P> +When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a +match attempt for an unanchored pattern fails when the current position is at a +CRLF sequence, and the pattern contains no explicit matches for CR or LF +characters, the match position is advanced by two characters instead of one, in +other words, to after the CRLF. +</P> +<P> +The above rule is a compromise that makes the most common cases work as +expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not +set), it does not match the string "\r\nA" because, after failing at the +start, it skips both the CR and the LF before retrying. However, the pattern +[\r\n]A does match that string, because it contains an explicit CR or LF +reference, and so advances only by one character after the first failure. +</P> +<P> +An explicit match for CR of LF is either a literal appearance of one of those +characters, or one of the \r or \n escape sequences. Implicit matches such as +[^X] do not count, nor does \s (which includes CR and LF in the characters +that it matches). +</P> +<P> +Notwithstanding the above, anomalous effects may still occur when CRLF is a +valid newline sequence and explicit \r or \n escapes appear in the pattern. +<pre> + PCRE_NOTBOL +</pre> +This option specifies that first character of the subject string is not the +beginning of a line, so the circumflex metacharacter should not match before +it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex +never to match. This option affects only the behaviour of the circumflex +metacharacter. It does not affect \A. +<pre> + PCRE_NOTEOL +</pre> +This option specifies that the end of the subject string is not the end of a +line, so the dollar metacharacter should not match it nor (except in multiline +mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at +compile time) causes dollar never to match. This option affects only the +behaviour of the dollar metacharacter. It does not affect \Z or \z. +<pre> + PCRE_NOTEMPTY +</pre> +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 +<pre> + a?b? +</pre> +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". +<pre> + PCRE_NOTEMPTY_ATSTART +</pre> +This is like PCRE_NOTEMPTY, except that an empty string match that is not at +the start of the subject is permitted. If the pattern is anchored, such a match +can occur only if the pattern contains \K. +</P> +<P> +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 +<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_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 +<a href="pcredemo.html"><b>pcredemo</b></a> +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. +<pre> + PCRE_NO_START_OPTIMIZE +</pre> +There are a number of optimizations that <b>pcre_exec()</b> uses at the start of +a match, in order to speed up the process. For example, if it is known that an +unanchored match must start with a specific character, it searches the subject +for that character, and fails immediately if it cannot find it, without +actually running the main matching function. This means that a special item +such as (*COMMIT) at the start of a pattern is not considered until after a +suitable starting point for the match has been found. Also, 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> +<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. If +PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching +time. The use of PCRE_NO_START_OPTIMIZE at matching time (that is, passing it +to <b>pcre_exec()</b>) disables JIT execution; in this situation, matching is +always done using interpretively. +</P> +<P> +Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation. +Consider the pattern +<pre> + (*COMMIT)ABC +</pre> +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 +<pre> + (*MARK:A)(X|Y) +</pre> +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. +<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 entire string is checked before any other processing takes place. The value +of <i>startoffset</i> is also checked to ensure that it points to the start of a +UTF-8 character. There is a discussion about the +<a href="pcreunicode.html#utf8strings">validity of UTF-8 strings</a> +in the +<a href="pcreunicode.html"><b>pcreunicode</b></a> +page. If an invalid sequence of bytes is found, <b>pcre_exec()</b> returns the +error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a +truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both +cases, information about the precise nature of the error may also be returned +(see the descriptions of these errors in the section entitled \fIError return +values from\fP <b>pcre_exec()</b> +<a href="#errorlist">below).</a> +If <i>startoffset</i> 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> +<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 character (or the end +of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an +invalid string as a subject or an invalid value of <i>startoffset</i> is +undefined. Your program may crash or loop. +<pre> + PCRE_PARTIAL_HARD + PCRE_PARTIAL_SOFT +</pre> +These options turn on the partial matching feature. For backwards +compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match +occurs if the end of the subject string is reached successfully, but there are +not enough subject characters to complete the match. If this happens when +PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by +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> +<P> +If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a +partial match is found, <b>pcre_exec()</b> 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> +<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 +<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>startoffset</i>. The units for <i>length</i> and <i>startoffset</i> are bytes +for the 8-bit library, 16-bit data items for the 16-bit library, and 32-bit +data items for the 32-bit library. +</P> +<P> +If <i>startoffset</i> is negative or greater than the length of the subject, +<b>pcre_exec()</b> returns PCRE_ERROR_BADOFFSET. 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. In UTF-8 or UTF-16 mode, the offset must point +to the start of a character, or the end of the subject (in UTF-32 mode, one +data unit equals one character, so all offsets are valid). Unlike the pattern +string, the subject may contain binary zeroes. +</P> +<P> +A non-zero starting offset is useful when searching for another match in the +same subject by calling <b>pcre_exec()</b> again after a previous success. +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 +<pre> + \Biss\B +</pre> +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 +occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the +subject, namely "issipi", it does not match, because \B is always false at the +start of the subject, which is deemed to be a word boundary. However, if +<b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i> +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> +<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 +<a href="pcredemo.html"><b>pcredemo</b></a> +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> +<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. +</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 +pattern. Following the usage in Jeffrey Friedl's book, this is called +"capturing" in what follows, and the phrase "capturing subpattern" is used for +a fragment of a pattern that picks out a substring. PCRE supports several other +kinds of parenthesized subpattern that do not cause substrings to be captured. +</P> +<P> +Captured substrings are returned to the caller via a vector of integers whose +address is passed in <i>ovector</i>. The number of elements in the vector is +passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>: this +argument is NOT the size of <i>ovector</i> in bytes. +</P> +<P> +The first two-thirds of the vector is used to pass back captured substrings, +each substring using a pair of integers. The remaining third of the vector is +used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns, +and is not available for passing back information. The number 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 is successful, information about captured substrings is returned +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 +each 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. These values are always data unit offsets, even in UTF mode. They +are byte offsets in the 8-bit library, 16-bit data item offsets in the 16-bit +library, and 32-bit data item offsets in the 32-bit library. <b>Note</b>: they +are not character counts. +</P> +<P> +The first pair of integers, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the +portion of the subject string matched by the entire pattern. The next pair is +used for the first capturing subpattern, and so on. The value returned by +<b>pcre_exec()</b> is one more than the highest numbered pair that has been set. +For example, if two substrings have been captured, the returned value is 3. If +there are no capturing subpatterns, the return value from a successful match is +1, indicating that just the first pair of offsets has been set. +</P> +<P> +If a capturing subpattern is matched repeatedly, it is the last portion of the +string that it matched that is returned. +</P> +<P> +If the vector is too small to hold all the captured substring offsets, it is +used as far as possible (up to two-thirds of its length), and the function +returns a value of zero. If neither the actual string matched nor any captured +substrings are of 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> is not big enough to remember the related +substrings, PCRE has to get additional memory for use during matching. Thus it +is usually advisable to supply an <i>ovector</i> of reasonable size. +</P> +<P> +There are some cases where zero is returned (indicating vector overflow) when +in fact the vector is exactly the right size for the final match. For example, +consider the pattern +<pre> + (a)(?:(b)c|bd) +</pre> +If a vector of 6 elements (allowing for only 1 captured substring) is given +with subject string "abd", <b>pcre_exec()</b> will try to set the second +captured string, thereby recording a vector overflow, before failing to match +"c" and backing up to try the second alternative. The zero return, however, +does correctly indicate that the maximum number of slots (namely 2) have been +filled. In similar cases where there is temporary overflow, but the final +number of used slots is actually less than the maximum, a non-zero value is +returned. +</P> +<P> +The <b>pcre_fullinfo()</b> function 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> +<P> +It is possible for capturing subpattern number <i>n+1</i> to match some part of +the subject when subpattern <i>n</i> has not been used at all. For example, if +the string "abc" is matched against the pattern (a|(z))(bc) the return from the +function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this +happens, both values in the offset pairs corresponding to unused subpatterns +are set to -1. +</P> +<P> +Offset values that correspond to unused subpatterns at the end of the +expression are also set to -1. For example, if the string "abc" is matched +against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The +return from the function is 2, because the highest used capturing subpattern +number is 1, and the offsets for for the second and third capturing subpatterns +(assuming the vector is large enough, of course) are set to -1. +</P> +<P> +<b>Note</b>: Elements in the first two-thirds of <i>ovector</i> that do not +correspond to capturing parentheses in the pattern are never changed. That is, +if a pattern contains <i>n</i> capturing parentheses, no more than +<i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by <b>pcre_exec()</b>. The other +elements (in the first two-thirds) retain whatever values they previously had. +</P> +<P> +Some convenience functions are provided for extracting the captured substrings +as separate strings. These are described below. +<a name="errorlist"></a></P> +<br><b> +Error 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: +<pre> + PCRE_ERROR_NOMATCH (-1) +</pre> +The subject string did not match the pattern. +<pre> + PCRE_ERROR_NULL (-2) +</pre> +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. +<pre> + PCRE_ERROR_BADOPTION (-3) +</pre> +An unrecognized bit was set in the <i>options</i> argument. +<pre> + PCRE_ERROR_BADMAGIC (-4) +</pre> +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 and to detect when a pattern that was +compiled in an environment of one endianness is run in an environment with the +other endianness. This is the error that PCRE gives when the magic number is +not present. +<pre> + PCRE_ERROR_UNKNOWN_OPCODE (-5) +</pre> +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. +<pre> + PCRE_ERROR_NOMEMORY (-6) +</pre> +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 +automatically freed at the end of matching. +</P> +<P> +This error is also given if <b>pcre_stack_malloc()</b> fails in +<b>pcre_exec()</b>. This can happen only when PCRE has been compiled with +<b>--disable-stack-for-recursion</b>. +<pre> + PCRE_ERROR_NOSUBSTRING (-7) +</pre> +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>. +<pre> + PCRE_ERROR_MATCHLIMIT (-8) +</pre> +The 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. +<pre> + PCRE_ERROR_CALLOUT (-9) +</pre> +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 +<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, +and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector +(<i>ovecsize</i>) is at least 2, the byte offset to the start of the the invalid +UTF-8 character is placed in the first element, and a reason code is placed in +the second element. The reason codes are listed in the +<a href="#badutf8reasons">following section.</a> +For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a +truncated UTF-8 character at the end of the subject (reason codes 1 to 5), +PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8. +<pre> + PCRE_ERROR_BADUTF8_OFFSET (-11) +</pre> +The UTF-8 byte sequence that was passed as a subject was checked and found to +be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of +<i>startoffset</i> did not point to the beginning of a UTF-8 character or the +end of the subject. +<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> +This code is no longer in use. It was formerly returned when the PCRE_PARTIAL +option was used with a compiled pattern containing items that were not +supported for partial matching. From release 8.00 onwards, there are no +restrictions on 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. +<pre> + PCRE_ERROR_RECURSIONLIMIT (-21) +</pre> +The internal recursion limit, as specified by the <i>match_limit_recursion</i> +field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the +description above. +<pre> + PCRE_ERROR_BADNEWLINE (-23) +</pre> +An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given. +<pre> + PCRE_ERROR_BADOFFSET (-24) +</pre> +The value of <i>startoffset</i> was negative or greater than the length of the +subject, that is, the value in <i>length</i>. +<pre> + PCRE_ERROR_SHORTUTF8 (-25) +</pre> +This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string +ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set. +Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in +fact sufficient to detect this case, but this special error code for +PCRE_PARTIAL_HARD precedes the implementation of returned information; it is +retained for backwards compatibility. +<pre> + PCRE_ERROR_RECURSELOOP (-26) +</pre> +This error is returned when <b>pcre_exec()</b> detects a recursion loop within +the pattern. Specifically, it means that either the whole pattern or a +subpattern has been called recursively for the second time at the same position +in the subject string. Some simple patterns that might do this are detected and +faulted at compile time, but more complicated cases, in particular mutual +recursions between two different subpatterns, cannot be detected until run +time. +<pre> + PCRE_ERROR_JIT_STACKLIMIT (-27) +</pre> +This error is returned when a pattern that was successfully studied using a +JIT compile option is being matched, but the memory available for the +just-in-time processing stack is not large enough. See the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation for more details. +<pre> + PCRE_ERROR_BADMODE (-28) +</pre> +This error is given if a pattern that was compiled by the 8-bit library is +passed to a 16-bit or 32-bit library function, or vice versa. +<pre> + PCRE_ERROR_BADENDIANNESS (-29) +</pre> +This error is given if a pattern that was compiled and saved is reloaded on a +host with different endianness. The utility function +<b>pcre_pattern_to_host_byte_order()</b> can be used to convert such a pattern +so that it runs on the new host. +<pre> + PCRE_ERROR_JIT_BADOPTION +</pre> +This error is returned when a pattern that was successfully studied using a JIT +compile option is being matched, but the matching mode (partial or complete +match) does not correspond to any JIT compilation mode. When the JIT fast path +function is used, this error may be also given for invalid options. See the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation for more details. +<pre> + PCRE_ERROR_BADLENGTH (-32) +</pre> +This error is given if <b>pcre_exec()</b> is called with a negative value for +the <i>length</i> argument. +</P> +<P> +Error numbers -16 to -20, -22, and 30 are not used by <b>pcre_exec()</b>. +<a name="badutf8reasons"></a></P> +<br><b> +Reason codes for invalid UTF-8 strings +</b><br> +<P> +This section applies only to the 8-bit library. The corresponding information +for the 16-bit and 32-bit libraries is given in the +<a href="pcre16.html"><b>pcre16</b></a> +and +<a href="pcre32.html"><b>pcre32</b></a> +pages. +</P> +<P> +When <b>pcre_exec()</b> returns either PCRE_ERROR_BADUTF8 or +PCRE_ERROR_SHORTUTF8, and the size of the output vector (<i>ovecsize</i>) is at +least 2, the offset of the start of the invalid UTF-8 character is placed in +the first output vector element (<i>ovector[0]</i>) and a reason code is placed +in the second element (<i>ovector[1]</i>). The reason codes are given names in +the <b>pcre.h</b> header file: +<pre> + PCRE_UTF8_ERR1 + PCRE_UTF8_ERR2 + PCRE_UTF8_ERR3 + PCRE_UTF8_ERR4 + PCRE_UTF8_ERR5 +</pre> +The string ends with a truncated UTF-8 character; the code specifies how many +bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be +no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279) +allows for up to 6 bytes, and this is checked first; hence the possibility of +4 or 5 missing bytes. +<pre> + PCRE_UTF8_ERR6 + PCRE_UTF8_ERR7 + PCRE_UTF8_ERR8 + PCRE_UTF8_ERR9 + PCRE_UTF8_ERR10 +</pre> +The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the +character do not have the binary value 0b10 (that is, either the most +significant bit is 0, or the next bit is 1). +<pre> + PCRE_UTF8_ERR11 + PCRE_UTF8_ERR12 +</pre> +A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long; +these code points are excluded by RFC 3629. +<pre> + PCRE_UTF8_ERR13 +</pre> +A 4-byte character has a value greater than 0x10fff; these code points are +excluded by RFC 3629. +<pre> + PCRE_UTF8_ERR14 +</pre> +A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of +code points are reserved by RFC 3629 for use with UTF-16, and so are excluded +from UTF-8. +<pre> + PCRE_UTF8_ERR15 + PCRE_UTF8_ERR16 + PCRE_UTF8_ERR17 + PCRE_UTF8_ERR18 + PCRE_UTF8_ERR19 +</pre> +A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a +value that can be represented by fewer bytes, which is invalid. For example, +the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just +one byte. +<pre> + PCRE_UTF8_ERR20 +</pre> +The two most significant bits of the first byte of a character have the binary +value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a +byte can only validly occur as the second or subsequent byte of a multi-byte +character. +<pre> + PCRE_UTF8_ERR21 +</pre> +The first byte of a character has the value 0xfe or 0xff. These values can +never occur in a valid UTF-8 string. +<pre> + PCRE_UTF8_ERR22 +</pre> +This error code was formerly used when the presence of a so-called +"non-character" caused an error. Unicode corrigendum #9 makes it clear that +such characters should not cause a string to be rejected, and so this code is +no longer in use and is never returned. +</P> +<br><a name="SEC18" 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> +<b> int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b> const char **<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre_get_substring_list(const char *<i>subject</i>,</b> +<b> int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b> +</P> +<P> +Captured substrings can be accessed directly by using the offsets returned by +<b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions +<b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and +<b>pcre_get_substring_list()</b> are provided for extracting captured substrings +as new, separate, zero-terminated strings. These functions identify substrings +by number. The next section describes functions for extracting named +substrings. +</P> +<P> +A substring that contains a binary zero is correctly extracted and has a +further zero added on the end, but the result is not, of course, a C string. +However, you can process such a string by referring to the length that is +returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>. +Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate +for handling strings containing binary zeros, because the end of the final +string is not independently indicated. +</P> +<P> +The first three arguments are the same for all three of these functions: +<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 zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of +space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the +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, 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 these error codes: +<pre> + PCRE_ERROR_NOMEMORY (-6) +</pre> +The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get +memory failed for <b>pcre_get_substring()</b>. +<pre> + PCRE_ERROR_NOSUBSTRING (-7) +</pre> +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 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 the error code +<pre> + PCRE_ERROR_NOMEMORY (-6) +</pre> +if the attempt to get the memory block failed. +</P> +<P> +When any of these functions encounter a substring that is unset, which can +happen when capturing subpattern number <i>n+1</i> matches some part of the +subject, but subpattern <i>n</i> has not been used at all, they return an empty +string. This can be distinguished from a genuine zero-length substring by +inspecting the appropriate offset in <i>ovector</i>, which is negative for unset +substrings. +</P> +<P> +The two convenience functions <b>pcre_free_substring()</b> and +<b>pcre_free_substring_list()</b> can be used to free the memory returned by +a previous call of <b>pcre_get_substring()</b> or +<b>pcre_get_substring_list()</b>, respectively. They do nothing more than call +the function pointed to by <b>pcre_free</b>, which of course could be called +directly from a C program. However, PCRE is used in some situations where it is +linked via a special interface to another programming language that cannot use +<b>pcre_free</b> directly; it is for these cases that the functions are +provided. +</P> +<br><a name="SEC19" 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> +<br> +<br> +<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> +<b> char *<i>buffer</i>, int <i>buffersize</i>);</b> +<br> +<br> +<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. +For example, for this pattern +<pre> + (a+)b(?<xxx>\d+)... +</pre> +the number of the subpattern called "xxx" is 2. If the name is known to be +unique (PCRE_DUPNAMES was not set), 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> +Given the number, you can extract the substring directly, or use one of the +functions described in the previous section. For convenience, there are also +two functions that do the whole job. +</P> +<P> +Most of the arguments of <b>pcre_copy_named_substring()</b> and +<b>pcre_get_named_substring()</b> are the same as those for the similarly named +functions that extract by number. As these are described in the previous +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 +is an extra argument, given at the start, which is a pointer to the compiled +pattern. This is needed in order to gain access to the name-to-number +translation table. +</P> +<P> +These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they +then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as +appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names, +the behaviour may not be what you want (see the next section). +</P> +<P> +<b>Warning:</b> If the pattern uses the (?| feature to set up multiple +subpatterns with the same number, as described in the +<a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a> +in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +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. +</P> +<br><a name="SEC20" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br> +<P> +<b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b> +<b> const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b> +</P> +<P> +When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns +are not required to be unique. (Duplicate names are always allowed for +subpatterns with the same number, created by using the (?| feature. Indeed, if +such subpatterns are named, they are required to use the same names.) +</P> +<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 +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. +</P> +<P> +When duplicates are present, <b>pcre_copy_named_substring()</b> and +<b>pcre_get_named_substring()</b> return the first substring corresponding to +the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is +returned; no data is returned. The <b>pcre_get_stringnumber()</b> function +returns one of the numbers that are associated with the name, but it is not +defined which it is. +</P> +<P> +If you want to get full details of all captured substrings for a given name, +you must use the <b>pcre_get_stringtable_entries()</b> function. The first +argument is the compiled pattern, and the second is the name. The third and +fourth are pointers to variables which are updated by the function. After it +has run, they point to the first and last entries in the name-to-number table +for the given name. The function itself returns the length of each entry, or +PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is +described above in the section entitled <i>Information about a pattern</i> +<a href="#infoaboutpattern">above.</a> +Given all the relevant entries for the name, you can extract each of their +numbers, and hence the captured data, if any. +</P> +<br><a name="SEC21" 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. +</P> +<br><a name="SEC22" href="#TOC1">OBTAINING AN ESTIMATE OF STACK USAGE</a><br> +<P> +Matching certain patterns using <b>pcre_exec()</b> can use a lot of process +stack, which in certain environments can be rather limited in size. Some users +find it helpful to have an estimate of the amount of stack that is used by +<b>pcre_exec()</b>, to help them set recursion limits, as described in the +<a href="pcrestack.html"><b>pcrestack</b></a> +documentation. The estimate that is output by <b>pcretest</b> when called with +the <b>-m</b> and <b>-C</b> options is obtained by calling <b>pcre_exec</b> with +the values NULL, NULL, NULL, -999, and -999 for its first five arguments. +</P> +<P> +Normally, if its first argument is NULL, <b>pcre_exec()</b> immediately returns +the negative error code PCRE_ERROR_NULL, but with this special combination of +arguments, it returns instead a negative number whose absolute value is the +approximate stack frame size in bytes. (A negative number is used so that it is +clear that no match has happened.) The value is approximate because in some +cases, recursive calls to <b>pcre_exec()</b> occur when there are one or two +additional variables on the stack. +</P> +<P> +If PCRE has been compiled to use the heap instead of the stack for recursion, +the value returned is the size of each block that is obtained from the heap. +<a name="dfamatch"></a></P> +<br><a name="SEC23" 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 matching algorithm that scans the subject string +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, and a +list of features that <b>pcre_dfa_exec()</b> does not support, 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 potential matches. +</P> +<P> +Here is an example of a simple call to <b>pcre_dfa_exec()</b>: +<pre> + int rc; + int ovector[10]; + int wspace[20]; + rc = pcre_dfa_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector of integers for substring information */ + 10, /* number of elements (NOT size in bytes) */ + wspace, /* working space vector */ + 20); /* 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_NEWLINE_<i>xxx</i>, +PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, +PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, +PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. +All but the last four of these are exactly the same as for <b>pcre_exec()</b>, +so their description is not repeated here. +<pre> + PCRE_PARTIAL_HARD + PCRE_PARTIAL_SOFT +</pre> +These have the same general effect as they do for <b>pcre_exec()</b>, but the +details are slightly different. When PCRE_PARTIAL_HARD is set for +<b>pcre_dfa_exec()</b>, it returns PCRE_ERROR_PARTIAL if the end of the subject +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 +<a href="pcrepartial.html"><b>pcrepartial</b></a> +documentation. +<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 alternative 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> 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> + <.*> +</pre> +is matched against the string +<pre> + This is <something> <something else> <something further> no more +</pre> +the three matched strings are +<pre> + <something> + <something> <something else> + <something> <something else> <something further> +</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. In fact, 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. Unlike <b>pcre_exec()</b>, <b>pcre_dfa_exec()</b> can use +the entire <i>ovector</i> for returning matched strings. +</P> +<P> +NOTE: PCRE's "auto-possessification" optimization usually applies to character +repeats at the end of a pattern (as well as internally). For example, the +pattern "a\d+" is compiled as if it were "a\d++" because there is no point +even considering the possibility of backtracking into the repeated digits. For +DFA matching, this means that only one possible match is found. If you really +do want multiple matches in such cases, either use an ungreedy repeat +("a\d+?") or set the PCRE_NO_AUTO_POSSESS option when compiling. +</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 that +uses a back reference for the condition, or a test for recursion in a specific +group. These are 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> or +<i>match_limit_recursion</i> fields. This is not supported (these fields are +meaningless for DFA matching). +<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. +<pre> + PCRE_ERROR_DFA_BADRESTART (-30) +</pre> +When <b>pcre_dfa_exec()</b> is called with the <b>PCRE_DFA_RESTART</b> option, +some plausibility checks are made on the contents of the workspace, which +should contain data about the previous partial match. If any of these checks +fail, this error is given. +</P> +<br><a name="SEC24" href="#TOC1">SEE ALSO</a><br> +<P> +<b>pcre16</b>(3), <b>pcre32</b>(3), <b>pcrebuild</b>(3), <b>pcrecallout</b>(3), +<b>pcrecpp(3)</b>(3), <b>pcrematching</b>(3), <b>pcrepartial</b>(3), +<b>pcreposix</b>(3), <b>pcreprecompile</b>(3), <b>pcresample</b>(3), +<b>pcrestack</b>(3). +</P> +<br><a name="SEC25" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC26" href="#TOC1">REVISION</a><br> +<P> +Last updated: 09 February 2014 +<br> +Copyright © 1997-2014 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> |