36af74cb25
Some manual changes done to the library were lost with this update. They will be added in the next commit.
3275 lines
149 KiB
HTML
3275 lines
149 KiB
HTML
<html>
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<head>
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<title>pcre2api specification</title>
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</head>
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<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
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<h1>pcre2api man page</h1>
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<p>
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Return to the <a href="index.html">PCRE2 index page</a>.
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</p>
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<p>
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This page is part of the PCRE2 HTML documentation. It was generated
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automatically from the original man page. If there is any nonsense in it,
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please consult the man page, in case the conversion went wrong.
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<br>
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<ul>
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<li><a name="TOC1" href="#SEC1">PCRE2 NATIVE API BASIC FUNCTIONS</a>
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<li><a name="TOC2" href="#SEC2">PCRE2 NATIVE API AUXILIARY MATCH FUNCTIONS</a>
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<li><a name="TOC3" href="#SEC3">PCRE2 NATIVE API GENERAL CONTEXT FUNCTIONS</a>
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<li><a name="TOC4" href="#SEC4">PCRE2 NATIVE API COMPILE CONTEXT FUNCTIONS</a>
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<li><a name="TOC5" href="#SEC5">PCRE2 NATIVE API MATCH CONTEXT FUNCTIONS</a>
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<li><a name="TOC6" href="#SEC6">PCRE2 NATIVE API STRING EXTRACTION FUNCTIONS</a>
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<li><a name="TOC7" href="#SEC7">PCRE2 NATIVE API STRING SUBSTITUTION FUNCTION</a>
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<li><a name="TOC8" href="#SEC8">PCRE2 NATIVE API JIT FUNCTIONS</a>
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<li><a name="TOC9" href="#SEC9">PCRE2 NATIVE API SERIALIZATION FUNCTIONS</a>
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<li><a name="TOC10" href="#SEC10">PCRE2 NATIVE API AUXILIARY FUNCTIONS</a>
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<li><a name="TOC11" href="#SEC11">PCRE2 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a>
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<li><a name="TOC12" href="#SEC12">PCRE2 API OVERVIEW</a>
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<li><a name="TOC13" href="#SEC13">STRING LENGTHS AND OFFSETS</a>
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<li><a name="TOC14" href="#SEC14">NEWLINES</a>
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<li><a name="TOC15" href="#SEC15">MULTITHREADING</a>
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<li><a name="TOC16" href="#SEC16">PCRE2 CONTEXTS</a>
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<li><a name="TOC17" href="#SEC17">CHECKING BUILD-TIME OPTIONS</a>
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<li><a name="TOC18" href="#SEC18">COMPILING A PATTERN</a>
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<li><a name="TOC19" href="#SEC19">COMPILATION ERROR CODES</a>
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<li><a name="TOC20" href="#SEC20">JUST-IN-TIME (JIT) COMPILATION</a>
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<li><a name="TOC21" href="#SEC21">LOCALE SUPPORT</a>
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<li><a name="TOC22" href="#SEC22">INFORMATION ABOUT A COMPILED PATTERN</a>
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<li><a name="TOC23" href="#SEC23">INFORMATION ABOUT A PATTERN'S CALLOUTS</a>
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<li><a name="TOC24" href="#SEC24">SERIALIZATION AND PRECOMPILING</a>
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<li><a name="TOC25" href="#SEC25">THE MATCH DATA BLOCK</a>
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<li><a name="TOC26" href="#SEC26">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a>
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<li><a name="TOC27" href="#SEC27">NEWLINE HANDLING WHEN MATCHING</a>
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<li><a name="TOC28" href="#SEC28">HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS</a>
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<li><a name="TOC29" href="#SEC29">OTHER INFORMATION ABOUT A MATCH</a>
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<li><a name="TOC30" href="#SEC30">ERROR RETURNS FROM <b>pcre2_match()</b></a>
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<li><a name="TOC31" href="#SEC31">OBTAINING A TEXTUAL ERROR MESSAGE</a>
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<li><a name="TOC32" href="#SEC32">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a>
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<li><a name="TOC33" href="#SEC33">EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS</a>
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<li><a name="TOC34" href="#SEC34">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a>
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<li><a name="TOC35" href="#SEC35">CREATING A NEW STRING WITH SUBSTITUTIONS</a>
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<li><a name="TOC36" href="#SEC36">DUPLICATE SUBPATTERN NAMES</a>
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<li><a name="TOC37" href="#SEC37">FINDING ALL POSSIBLE MATCHES AT ONE POSITION</a>
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<li><a name="TOC38" href="#SEC38">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a>
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<li><a name="TOC39" href="#SEC39">SEE ALSO</a>
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<li><a name="TOC40" href="#SEC40">AUTHOR</a>
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<li><a name="TOC41" href="#SEC41">REVISION</a>
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</ul>
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<P>
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<b>#include <pcre2.h></b>
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<br>
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<br>
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PCRE2 is a new API for PCRE. This document contains a description of all its
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functions. See the
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<a href="pcre2.html"><b>pcre2</b></a>
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document for an overview of all the PCRE2 documentation.
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</P>
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<br><a name="SEC1" href="#TOC1">PCRE2 NATIVE API BASIC FUNCTIONS</a><br>
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<P>
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<b>pcre2_code *pcre2_compile(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b>
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<b> uint32_t <i>options</i>, int *<i>errorcode</i>, PCRE2_SIZE *<i>erroroffset,</i></b>
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<b> pcre2_compile_context *<i>ccontext</i>);</b>
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<br>
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<br>
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<b>void pcre2_code_free(pcre2_code *<i>code</i>);</b>
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<br>
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<br>
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<b>pcre2_match_data *pcre2_match_data_create(uint32_t <i>ovecsize</i>,</b>
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<b> pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
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<b>pcre2_match_data *pcre2_match_data_create_from_pattern(</b>
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<b> const pcre2_code *<i>code</i>, pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
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<b>int pcre2_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b>
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<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b>
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<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b>
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<b> pcre2_match_context *<i>mcontext</i>);</b>
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<br>
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<br>
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<b>int pcre2_dfa_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b>
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<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b>
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<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b>
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<b> pcre2_match_context *<i>mcontext</i>,</b>
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<b> int *<i>workspace</i>, PCRE2_SIZE <i>wscount</i>);</b>
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<br>
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<br>
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<b>void pcre2_match_data_free(pcre2_match_data *<i>match_data</i>);</b>
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</P>
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<br><a name="SEC2" href="#TOC1">PCRE2 NATIVE API AUXILIARY MATCH FUNCTIONS</a><br>
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<P>
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<b>PCRE2_SPTR pcre2_get_mark(pcre2_match_data *<i>match_data</i>);</b>
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<br>
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<br>
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<b>uint32_t pcre2_get_ovector_count(pcre2_match_data *<i>match_data</i>);</b>
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<br>
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<br>
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<b>PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *<i>match_data</i>);</b>
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<br>
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<br>
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<b>PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *<i>match_data</i>);</b>
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</P>
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<br><a name="SEC3" href="#TOC1">PCRE2 NATIVE API GENERAL CONTEXT FUNCTIONS</a><br>
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<P>
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<b>pcre2_general_context *pcre2_general_context_create(</b>
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<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b>
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<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b>
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<br>
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<br>
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<b>pcre2_general_context *pcre2_general_context_copy(</b>
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<b> pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
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<b>void pcre2_general_context_free(pcre2_general_context *<i>gcontext</i>);</b>
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</P>
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<br><a name="SEC4" href="#TOC1">PCRE2 NATIVE API COMPILE CONTEXT FUNCTIONS</a><br>
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<P>
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<b>pcre2_compile_context *pcre2_compile_context_create(</b>
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<b> pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
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<b>pcre2_compile_context *pcre2_compile_context_copy(</b>
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<b> pcre2_compile_context *<i>ccontext</i>);</b>
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<br>
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<br>
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<b>void pcre2_compile_context_free(pcre2_compile_context *<i>ccontext</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_bsr(pcre2_compile_context *<i>ccontext</i>,</b>
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<b> uint32_t <i>value</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_character_tables(pcre2_compile_context *<i>ccontext</i>,</b>
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<b> const unsigned char *<i>tables</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_max_pattern_length(pcre2_compile_context *<i>ccontext</i>,</b>
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<b> PCRE2_SIZE <i>value</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_newline(pcre2_compile_context *<i>ccontext</i>,</b>
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<b> uint32_t <i>value</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_parens_nest_limit(pcre2_compile_context *<i>ccontext</i>,</b>
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<b> uint32_t <i>value</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_compile_recursion_guard(pcre2_compile_context *<i>ccontext</i>,</b>
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<b> int (*<i>guard_function</i>)(uint32_t, void *), void *<i>user_data</i>);</b>
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</P>
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<br><a name="SEC5" href="#TOC1">PCRE2 NATIVE API MATCH CONTEXT FUNCTIONS</a><br>
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<P>
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<b>pcre2_match_context *pcre2_match_context_create(</b>
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<b> pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
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<b>pcre2_match_context *pcre2_match_context_copy(</b>
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<b> pcre2_match_context *<i>mcontext</i>);</b>
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<br>
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<br>
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<b>void pcre2_match_context_free(pcre2_match_context *<i>mcontext</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_callout(pcre2_match_context *<i>mcontext</i>,</b>
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<b> int (*<i>callout_function</i>)(pcre2_callout_block *, void *),</b>
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<b> void *<i>callout_data</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_match_limit(pcre2_match_context *<i>mcontext</i>,</b>
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<b> uint32_t <i>value</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_offset_limit(pcre2_match_context *<i>mcontext</i>,</b>
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<b> PCRE2_SIZE <i>value</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_recursion_limit(pcre2_match_context *<i>mcontext</i>,</b>
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<b> uint32_t <i>value</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_recursion_memory_management(</b>
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<b> pcre2_match_context *<i>mcontext</i>,</b>
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<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b>
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<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b>
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</P>
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<br><a name="SEC6" href="#TOC1">PCRE2 NATIVE API STRING EXTRACTION FUNCTIONS</a><br>
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<P>
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<b>int pcre2_substring_copy_byname(pcre2_match_data *<i>match_data</i>,</b>
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<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR *<i>buffer</i>, PCRE2_SIZE *<i>bufflen</i>);</b>
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<br>
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<br>
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<b>int pcre2_substring_copy_bynumber(pcre2_match_data *<i>match_data</i>,</b>
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<b> uint32_t <i>number</i>, PCRE2_UCHAR *<i>buffer</i>,</b>
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<b> PCRE2_SIZE *<i>bufflen</i>);</b>
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<br>
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<br>
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<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b>
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<br>
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<br>
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<b>int pcre2_substring_get_byname(pcre2_match_data *<i>match_data</i>,</b>
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<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR **<i>bufferptr</i>, PCRE2_SIZE *<i>bufflen</i>);</b>
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<br>
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<br>
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<b>int pcre2_substring_get_bynumber(pcre2_match_data *<i>match_data</i>,</b>
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<b> uint32_t <i>number</i>, PCRE2_UCHAR **<i>bufferptr</i>,</b>
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<b> PCRE2_SIZE *<i>bufflen</i>);</b>
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<br>
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<br>
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<b>int pcre2_substring_length_byname(pcre2_match_data *<i>match_data</i>,</b>
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<b> PCRE2_SPTR <i>name</i>, PCRE2_SIZE *<i>length</i>);</b>
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<br>
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<br>
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<b>int pcre2_substring_length_bynumber(pcre2_match_data *<i>match_data</i>,</b>
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<b> uint32_t <i>number</i>, PCRE2_SIZE *<i>length</i>);</b>
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<br>
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<br>
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<b>int pcre2_substring_nametable_scan(const pcre2_code *<i>code</i>,</b>
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<b> PCRE2_SPTR <i>name</i>, PCRE2_SPTR *<i>first</i>, PCRE2_SPTR *<i>last</i>);</b>
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<br>
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<br>
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<b>int pcre2_substring_number_from_name(const pcre2_code *<i>code</i>,</b>
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<b> PCRE2_SPTR <i>name</i>);</b>
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<br>
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<br>
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<b>void pcre2_substring_list_free(PCRE2_SPTR *<i>list</i>);</b>
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<br>
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<br>
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<b>int pcre2_substring_list_get(pcre2_match_data *<i>match_data</i>,</b>
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<b>" PCRE2_UCHAR ***<i>listptr</i>, PCRE2_SIZE **<i>lengthsptr</i>);</b>
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</P>
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<br><a name="SEC7" href="#TOC1">PCRE2 NATIVE API STRING SUBSTITUTION FUNCTION</a><br>
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<P>
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<b>int pcre2_substitute(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b>
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<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b>
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<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b>
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<b> pcre2_match_context *<i>mcontext</i>, PCRE2_SPTR \fIreplacementzfP,</b>
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<b> PCRE2_SIZE <i>rlength</i>, PCRE2_UCHAR *<i>outputbuffer</i>,</b>
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<b> PCRE2_SIZE *<i>outlengthptr</i>);</b>
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</P>
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<br><a name="SEC8" href="#TOC1">PCRE2 NATIVE API JIT FUNCTIONS</a><br>
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<P>
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<b>int pcre2_jit_compile(pcre2_code *<i>code</i>, uint32_t <i>options</i>);</b>
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<br>
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<br>
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<b>int pcre2_jit_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b>
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<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b>
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<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b>
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<b> pcre2_match_context *<i>mcontext</i>);</b>
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<br>
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<br>
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<b>void pcre2_jit_free_unused_memory(pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
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<b>pcre2_jit_stack *pcre2_jit_stack_create(PCRE2_SIZE <i>startsize</i>,</b>
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<b> PCRE2_SIZE <i>maxsize</i>, pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
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<b>void pcre2_jit_stack_assign(pcre2_match_context *<i>mcontext</i>,</b>
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<b> pcre2_jit_callback <i>callback_function</i>, void *<i>callback_data</i>);</b>
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<br>
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<br>
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<b>void pcre2_jit_stack_free(pcre2_jit_stack *<i>jit_stack</i>);</b>
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</P>
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<br><a name="SEC9" href="#TOC1">PCRE2 NATIVE API SERIALIZATION FUNCTIONS</a><br>
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<P>
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<b>int32_t pcre2_serialize_decode(pcre2_code **<i>codes</i>,</b>
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<b> int32_t <i>number_of_codes</i>, const uint8_t *<i>bytes</i>,</b>
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<b> pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
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<b>int32_t pcre2_serialize_encode(const pcre2_code **<i>codes</i>,</b>
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<b> int32_t <i>number_of_codes</i>, uint8_t **<i>serialized_bytes</i>,</b>
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<b> PCRE2_SIZE *<i>serialized_size</i>, pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
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<b>void pcre2_serialize_free(uint8_t *<i>bytes</i>);</b>
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<br>
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<br>
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<b>int32_t pcre2_serialize_get_number_of_codes(const uint8_t *<i>bytes</i>);</b>
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</P>
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<br><a name="SEC10" href="#TOC1">PCRE2 NATIVE API AUXILIARY FUNCTIONS</a><br>
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<P>
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<b>pcre2_code *pcre2_code_copy(const pcre2_code *<i>code</i>);</b>
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<br>
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<br>
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<b>pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *<i>code</i>);</b>
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<br>
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<br>
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<b>int pcre2_get_error_message(int <i>errorcode</i>, PCRE2_UCHAR *<i>buffer</i>,</b>
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<b> PCRE2_SIZE <i>bufflen</i>);</b>
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<br>
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<br>
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<b>const unsigned char *pcre2_maketables(pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
|
|
<b>int pcre2_pattern_info(const pcre2 *<i>code</i>, uint32_t <i>what</i>, void *<i>where</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>int pcre2_callout_enumerate(const pcre2_code *<i>code</i>,</b>
|
|
<b> int (*<i>callback</i>)(pcre2_callout_enumerate_block *, void *),</b>
|
|
<b> void *<i>user_data</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b>
|
|
</P>
|
|
<br><a name="SEC11" href="#TOC1">PCRE2 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a><br>
|
|
<P>
|
|
There are three PCRE2 libraries, supporting 8-bit, 16-bit, and 32-bit code
|
|
units, respectively. However, there is just one header file, <b>pcre2.h</b>.
|
|
This contains the function prototypes and other definitions for all three
|
|
libraries. One, two, or all three can be installed simultaneously. On Unix-like
|
|
systems the libraries are called <b>libpcre2-8</b>, <b>libpcre2-16</b>, and
|
|
<b>libpcre2-32</b>, and they can also co-exist with the original PCRE libraries.
|
|
</P>
|
|
<P>
|
|
Character strings are passed to and from a PCRE2 library as a sequence of
|
|
unsigned integers in code units of the appropriate width. Every PCRE2 function
|
|
comes in three different forms, one for each library, for example:
|
|
<pre>
|
|
<b>pcre2_compile_8()</b>
|
|
<b>pcre2_compile_16()</b>
|
|
<b>pcre2_compile_32()</b>
|
|
</pre>
|
|
There are also three different sets of data types:
|
|
<pre>
|
|
<b>PCRE2_UCHAR8, PCRE2_UCHAR16, PCRE2_UCHAR32</b>
|
|
<b>PCRE2_SPTR8, PCRE2_SPTR16, PCRE2_SPTR32</b>
|
|
</pre>
|
|
The UCHAR types define unsigned code units of the appropriate widths. For
|
|
example, PCRE2_UCHAR16 is usually defined as `uint16_t'. The SPTR types are
|
|
constant pointers to the equivalent UCHAR types, that is, they are pointers to
|
|
vectors of unsigned code units.
|
|
</P>
|
|
<P>
|
|
Many applications use only one code unit width. For their convenience, macros
|
|
are defined whose names are the generic forms such as <b>pcre2_compile()</b> and
|
|
PCRE2_SPTR. These macros use the value of the macro PCRE2_CODE_UNIT_WIDTH to
|
|
generate the appropriate width-specific function and macro names.
|
|
PCRE2_CODE_UNIT_WIDTH is not defined by default. An application must define it
|
|
to be 8, 16, or 32 before including <b>pcre2.h</b> in order to make use of the
|
|
generic names.
|
|
</P>
|
|
<P>
|
|
Applications that use more than one code unit width can be linked with more
|
|
than one PCRE2 library, but must define PCRE2_CODE_UNIT_WIDTH to be 0 before
|
|
including <b>pcre2.h</b>, and then use the real function names. Any code that is
|
|
to be included in an environment where the value of PCRE2_CODE_UNIT_WIDTH is
|
|
unknown should also use the real function names. (Unfortunately, it is not
|
|
possible in C code to save and restore the value of a macro.)
|
|
</P>
|
|
<P>
|
|
If PCRE2_CODE_UNIT_WIDTH is not defined before including <b>pcre2.h</b>, a
|
|
compiler error occurs.
|
|
</P>
|
|
<P>
|
|
When using multiple libraries in an application, you must take care when
|
|
processing any particular pattern to use only functions from a single library.
|
|
For example, if you want to run a match using a pattern that was compiled with
|
|
<b>pcre2_compile_16()</b>, you must do so with <b>pcre2_match_16()</b>, not
|
|
<b>pcre2_match_8()</b>.
|
|
</P>
|
|
<P>
|
|
In the function summaries above, and in the rest of this document and other
|
|
PCRE2 documents, functions and data types are described using their generic
|
|
names, without the 8, 16, or 32 suffix.
|
|
</P>
|
|
<br><a name="SEC12" href="#TOC1">PCRE2 API OVERVIEW</a><br>
|
|
<P>
|
|
PCRE2 has its own native API, which is described in this document. There are
|
|
also some wrapper functions for the 8-bit library 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="pcre2posix.html"><b>pcre2posix</b></a>
|
|
documentation. Both these APIs define a set of C function calls.
|
|
</P>
|
|
<P>
|
|
The native API C data types, function prototypes, option values, and error
|
|
codes are defined in the header file <b>pcre2.h</b>, which contains definitions
|
|
of PCRE2_MAJOR and PCRE2_MINOR, the major and minor release numbers for the
|
|
library. Applications can use these to include support for different releases
|
|
of PCRE2.
|
|
</P>
|
|
<P>
|
|
In a Windows environment, if you want to statically link an application program
|
|
against a non-dll PCRE2 library, you must define PCRE2_STATIC before including
|
|
<b>pcre2.h</b>.
|
|
</P>
|
|
<P>
|
|
The functions <b>pcre2_compile()</b>, and <b>pcre2_match()</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>pcre2demo.c</i> in the PCRE2 source distribution. A listing
|
|
of this program is given in the
|
|
<a href="pcre2demo.html"><b>pcre2demo</b></a>
|
|
documentation, and the
|
|
<a href="pcre2sample.html"><b>pcre2sample</b></a>
|
|
documentation describes how to compile and run it.
|
|
</P>
|
|
<P>
|
|
Just-in-time compiler support is an optional feature of PCRE2 that can be built
|
|
in appropriate hardware environments. It greatly speeds up the matching
|
|
performance of many patterns. Programs can request that it be used if
|
|
available, by calling <b>pcre2_jit_compile()</b> after a pattern has been
|
|
successfully compiled by <b>pcre2_compile()</b>. This does nothing if JIT
|
|
support is not available.
|
|
</P>
|
|
<P>
|
|
More complicated programs might need to make use of the specialist functions
|
|
<b>pcre2_jit_stack_create()</b>, <b>pcre2_jit_stack_free()</b>, and
|
|
<b>pcre2_jit_stack_assign()</b> in order to control the JIT code's memory usage.
|
|
</P>
|
|
<P>
|
|
JIT matching is automatically used by <b>pcre2_match()</b> if it is available,
|
|
unless the PCRE2_NO_JIT option is set. There is also a direct interface for JIT
|
|
matching, which gives improved performance. The JIT-specific functions are
|
|
discussed in the
|
|
<a href="pcre2jit.html"><b>pcre2jit</b></a>
|
|
documentation.
|
|
</P>
|
|
<P>
|
|
A second matching function, <b>pcre2_dfa_match()</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="pcre2matching.html"><b>pcre2matching</b></a>
|
|
documentation. There is no JIT support for <b>pcre2_dfa_match()</b>.
|
|
</P>
|
|
<P>
|
|
In addition to the main compiling and matching functions, there are convenience
|
|
functions for extracting captured substrings from a subject string that has
|
|
been matched by <b>pcre2_match()</b>. They are:
|
|
<pre>
|
|
<b>pcre2_substring_copy_byname()</b>
|
|
<b>pcre2_substring_copy_bynumber()</b>
|
|
<b>pcre2_substring_get_byname()</b>
|
|
<b>pcre2_substring_get_bynumber()</b>
|
|
<b>pcre2_substring_list_get()</b>
|
|
<b>pcre2_substring_length_byname()</b>
|
|
<b>pcre2_substring_length_bynumber()</b>
|
|
<b>pcre2_substring_nametable_scan()</b>
|
|
<b>pcre2_substring_number_from_name()</b>
|
|
</pre>
|
|
<b>pcre2_substring_free()</b> and <b>pcre2_substring_list_free()</b> are also
|
|
provided, to free the memory used for extracted strings.
|
|
</P>
|
|
<P>
|
|
The function <b>pcre2_substitute()</b> can be called to match a pattern and
|
|
return a copy of the subject string with substitutions for parts that were
|
|
matched.
|
|
</P>
|
|
<P>
|
|
Functions whose names begin with <b>pcre2_serialize_</b> are used for saving
|
|
compiled patterns on disc or elsewhere, and reloading them later.
|
|
</P>
|
|
<P>
|
|
Finally, there are functions for finding out information about a compiled
|
|
pattern (<b>pcre2_pattern_info()</b>) and about the configuration with which
|
|
PCRE2 was built (<b>pcre2_config()</b>).
|
|
</P>
|
|
<P>
|
|
Functions with names ending with <b>_free()</b> are used for freeing memory
|
|
blocks of various sorts. In all cases, if one of these functions is called with
|
|
a NULL argument, it does nothing.
|
|
</P>
|
|
<br><a name="SEC13" href="#TOC1">STRING LENGTHS AND OFFSETS</a><br>
|
|
<P>
|
|
The PCRE2 API uses string lengths and offsets into strings of code units in
|
|
several places. These values are always of type PCRE2_SIZE, which is an
|
|
unsigned integer type, currently always defined as <i>size_t</i>. The largest
|
|
value that can be stored in such a type (that is ~(PCRE2_SIZE)0) is reserved
|
|
as a special indicator for zero-terminated strings and unset offsets.
|
|
Therefore, the longest string that can be handled is one less than this
|
|
maximum.
|
|
<a name="newlines"></a></P>
|
|
<br><a name="SEC14" href="#TOC1">NEWLINES</a><br>
|
|
<P>
|
|
PCRE2 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 PCRE2 is built, a default can be specified.
|
|
The default default is LF, which is the Unix standard. However, the newline
|
|
convention can be changed by an application when calling <b>pcre2_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="pcre2pattern.html"><b>pcre2pattern</b></a>
|
|
page for details of the special character sequences.
|
|
</P>
|
|
<P>
|
|
In the PCRE2 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="#matchoptions">section on <b>pcre2_match()</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; this has
|
|
its own separate convention.
|
|
</P>
|
|
<br><a name="SEC15" href="#TOC1">MULTITHREADING</a><br>
|
|
<P>
|
|
In a multithreaded application it is important to keep thread-specific data
|
|
separate from data that can be shared between threads. The PCRE2 library code
|
|
itself is thread-safe: it contains no static or global variables. The API is
|
|
designed to be fairly simple for non-threaded applications while at the same
|
|
time ensuring that multithreaded applications can use it.
|
|
</P>
|
|
<P>
|
|
There are several different blocks of data that are used to pass information
|
|
between the application and the PCRE2 libraries.
|
|
</P>
|
|
<br><b>
|
|
The compiled pattern
|
|
</b><br>
|
|
<P>
|
|
A pointer to the compiled form of a pattern is returned to the user when
|
|
<b>pcre2_compile()</b> is successful. The data in the compiled pattern is fixed,
|
|
and does not change when the pattern is matched. Therefore, it is thread-safe,
|
|
that is, the same compiled pattern can be used by more than one thread
|
|
simultaneously. For example, an application can compile all its patterns at the
|
|
start, before forking off multiple threads that use them. However, if the
|
|
just-in-time optimization feature is being used, it needs separate memory stack
|
|
areas for each thread. See the
|
|
<a href="pcre2jit.html"><b>pcre2jit</b></a>
|
|
documentation for more details.
|
|
</P>
|
|
<P>
|
|
In a more complicated situation, where patterns are compiled only when they are
|
|
first needed, but are still shared between threads, pointers to compiled
|
|
patterns must be protected from simultaneous writing by multiple threads, at
|
|
least until a pattern has been compiled. The logic can be something like this:
|
|
<pre>
|
|
Get a read-only (shared) lock (mutex) for pointer
|
|
if (pointer == NULL)
|
|
{
|
|
Get a write (unique) lock for pointer
|
|
pointer = pcre2_compile(...
|
|
}
|
|
Release the lock
|
|
Use pointer in pcre2_match()
|
|
</pre>
|
|
Of course, testing for compilation errors should also be included in the code.
|
|
</P>
|
|
<P>
|
|
If JIT is being used, but the JIT compilation is not being done immediately,
|
|
(perhaps waiting to see if the pattern is used often enough) similar logic is
|
|
required. JIT compilation updates a pointer within the compiled code block, so
|
|
a thread must gain unique write access to the pointer before calling
|
|
<b>pcre2_jit_compile()</b>. Alternatively, <b>pcre2_code_copy()</b> or
|
|
<b>pcre2_code_copy_with_tables()</b> can be used to obtain a private copy of the
|
|
compiled code.
|
|
</P>
|
|
<br><b>
|
|
Context blocks
|
|
</b><br>
|
|
<P>
|
|
The next main section below introduces the idea of "contexts" in which PCRE2
|
|
functions are called. A context is nothing more than a collection of parameters
|
|
that control the way PCRE2 operates. Grouping a number of parameters together
|
|
in a context is a convenient way of passing them to a PCRE2 function without
|
|
using lots of arguments. The parameters that are stored in contexts are in some
|
|
sense "advanced features" of the API. Many straightforward applications will
|
|
not need to use contexts.
|
|
</P>
|
|
<P>
|
|
In a multithreaded application, if the parameters in a context are values that
|
|
are never changed, the same context can be used by all the threads. However, if
|
|
any thread needs to change any value in a context, it must make its own
|
|
thread-specific copy.
|
|
</P>
|
|
<br><b>
|
|
Match blocks
|
|
</b><br>
|
|
<P>
|
|
The matching functions need a block of memory for working space and for storing
|
|
the results of a match. This includes details of what was matched, as well as
|
|
additional information such as the name of a (*MARK) setting. Each thread must
|
|
provide its own copy of this memory.
|
|
</P>
|
|
<br><a name="SEC16" href="#TOC1">PCRE2 CONTEXTS</a><br>
|
|
<P>
|
|
Some PCRE2 functions have a lot of parameters, many of which are used only by
|
|
specialist applications, for example, those that use custom memory management
|
|
or non-standard character tables. To keep function argument lists at a
|
|
reasonable size, and at the same time to keep the API extensible, "uncommon"
|
|
parameters are passed to certain functions in a <b>context</b> instead of
|
|
directly. A context is just a block of memory that holds the parameter values.
|
|
Applications that do not need to adjust any of the context parameters can pass
|
|
NULL when a context pointer is required.
|
|
</P>
|
|
<P>
|
|
There are three different types of context: a general context that is relevant
|
|
for several PCRE2 operations, a compile-time context, and a match-time context.
|
|
</P>
|
|
<br><b>
|
|
The general context
|
|
</b><br>
|
|
<P>
|
|
At present, this context just contains pointers to (and data for) external
|
|
memory management functions that are called from several places in the PCRE2
|
|
library. The context is named `general' rather than specifically `memory'
|
|
because in future other fields may be added. If you do not want to supply your
|
|
own custom memory management functions, you do not need to bother with a
|
|
general context. A general context is created by:
|
|
<b>pcre2_general_context *pcre2_general_context_create(</b>
|
|
<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b>
|
|
<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b>
|
|
<br>
|
|
<br>
|
|
The two function pointers specify custom memory management functions, whose
|
|
prototypes are:
|
|
<pre>
|
|
<b>void *private_malloc(PCRE2_SIZE, void *);</b>
|
|
<b>void private_free(void *, void *);</b>
|
|
</pre>
|
|
Whenever code in PCRE2 calls these functions, the final argument is the value
|
|
of <i>memory_data</i>. Either of the first two arguments of the creation
|
|
function may be NULL, in which case the system memory management functions
|
|
<i>malloc()</i> and <i>free()</i> are used. (This is not currently useful, as
|
|
there are no other fields in a general context, but in future there might be.)
|
|
The <i>private_malloc()</i> function is used (if supplied) to obtain memory for
|
|
storing the context, and all three values are saved as part of the context.
|
|
</P>
|
|
<P>
|
|
Whenever PCRE2 creates a data block of any kind, the block contains a pointer
|
|
to the <i>free()</i> function that matches the <i>malloc()</i> function that was
|
|
used. When the time comes to free the block, this function is called.
|
|
</P>
|
|
<P>
|
|
A general context can be copied by calling:
|
|
<b>pcre2_general_context *pcre2_general_context_copy(</b>
|
|
<b> pcre2_general_context *<i>gcontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
The memory used for a general context should be freed by calling:
|
|
<b>void pcre2_general_context_free(pcre2_general_context *<i>gcontext</i>);</b>
|
|
<a name="compilecontext"></a></P>
|
|
<br><b>
|
|
The compile context
|
|
</b><br>
|
|
<P>
|
|
A compile context is required if you want to change the default values of any
|
|
of the following compile-time parameters:
|
|
<pre>
|
|
What \R matches (Unicode newlines or CR, LF, CRLF only)
|
|
PCRE2's character tables
|
|
The newline character sequence
|
|
The compile time nested parentheses limit
|
|
The maximum length of the pattern string
|
|
An external function for stack checking
|
|
</pre>
|
|
A compile context is also required if you are using custom memory management.
|
|
If none of these apply, just pass NULL as the context argument of
|
|
<i>pcre2_compile()</i>.
|
|
</P>
|
|
<P>
|
|
A compile context is created, copied, and freed by the following functions:
|
|
<b>pcre2_compile_context *pcre2_compile_context_create(</b>
|
|
<b> pcre2_general_context *<i>gcontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>pcre2_compile_context *pcre2_compile_context_copy(</b>
|
|
<b> pcre2_compile_context *<i>ccontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>void pcre2_compile_context_free(pcre2_compile_context *<i>ccontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
A compile context is created with default values for its parameters. These can
|
|
be changed by calling the following functions, which return 0 on success, or
|
|
PCRE2_ERROR_BADDATA if invalid data is detected.
|
|
<b>int pcre2_set_bsr(pcre2_compile_context *<i>ccontext</i>,</b>
|
|
<b> uint32_t <i>value</i>);</b>
|
|
<br>
|
|
<br>
|
|
The value must be PCRE2_BSR_ANYCRLF, to specify that \R matches only CR, LF,
|
|
or CRLF, or PCRE2_BSR_UNICODE, to specify that \R matches any Unicode line
|
|
ending sequence. The value is used by the JIT compiler and by the two
|
|
interpreted matching functions, <i>pcre2_match()</i> and
|
|
<i>pcre2_dfa_match()</i>.
|
|
<b>int pcre2_set_character_tables(pcre2_compile_context *<i>ccontext</i>,</b>
|
|
<b> const unsigned char *<i>tables</i>);</b>
|
|
<br>
|
|
<br>
|
|
The value must be the result of a call to <i>pcre2_maketables()</i>, whose only
|
|
argument is a general context. This function builds a set of character tables
|
|
in the current locale.
|
|
<b>int pcre2_set_max_pattern_length(pcre2_compile_context *<i>ccontext</i>,</b>
|
|
<b> PCRE2_SIZE <i>value</i>);</b>
|
|
<br>
|
|
<br>
|
|
This sets a maximum length, in code units, for the pattern string that is to be
|
|
compiled. If the pattern is longer, an error is generated. This facility is
|
|
provided so that applications that accept patterns from external sources can
|
|
limit their size. The default is the largest number that a PCRE2_SIZE variable
|
|
can hold, which is effectively unlimited.
|
|
<b>int pcre2_set_newline(pcre2_compile_context *<i>ccontext</i>,</b>
|
|
<b> uint32_t <i>value</i>);</b>
|
|
<br>
|
|
<br>
|
|
This specifies which characters or character sequences are to be recognized as
|
|
newlines. The value must be one of PCRE2_NEWLINE_CR (carriage return only),
|
|
PCRE2_NEWLINE_LF (linefeed only), PCRE2_NEWLINE_CRLF (the two-character
|
|
sequence CR followed by LF), PCRE2_NEWLINE_ANYCRLF (any of the above), or
|
|
PCRE2_NEWLINE_ANY (any Unicode newline sequence).
|
|
</P>
|
|
<P>
|
|
When a pattern is compiled with the PCRE2_EXTENDED option, the value of this
|
|
parameter affects the recognition of white space and the end of internal
|
|
comments starting with #. The value is saved with the compiled pattern for
|
|
subsequent use by the JIT compiler and by the two interpreted matching
|
|
functions, <i>pcre2_match()</i> and <i>pcre2_dfa_match()</i>.
|
|
<b>int pcre2_set_parens_nest_limit(pcre2_compile_context *<i>ccontext</i>,</b>
|
|
<b> uint32_t <i>value</i>);</b>
|
|
<br>
|
|
<br>
|
|
This parameter ajusts the limit, set when PCRE2 is built (default 250), on the
|
|
depth of parenthesis nesting in a pattern. This limit stops rogue patterns
|
|
using up too much system stack when being compiled. The limit applies to
|
|
parentheses of all kinds, not just capturing parentheses.
|
|
<b>int pcre2_set_compile_recursion_guard(pcre2_compile_context *<i>ccontext</i>,</b>
|
|
<b> int (*<i>guard_function</i>)(uint32_t, void *), void *<i>user_data</i>);</b>
|
|
<br>
|
|
<br>
|
|
There is at least one application that runs PCRE2 in threads with very limited
|
|
system stack, where running out of stack is to be avoided at all costs. The
|
|
parenthesis limit above cannot take account of how much stack is actually
|
|
available. For a finer control, you can supply a function that is called
|
|
whenever <b>pcre2_compile()</b> starts to compile a parenthesized part of a
|
|
pattern. This function can check the actual stack size (or anything else that
|
|
it wants to, of course).
|
|
</P>
|
|
<P>
|
|
The first argument to the callout function gives the current depth of
|
|
nesting, and the second is user data that is set up by the last argument of
|
|
<b>pcre2_set_compile_recursion_guard()</b>. The callout function should return
|
|
zero if all is well, or non-zero to force an error.
|
|
<a name="matchcontext"></a></P>
|
|
<br><b>
|
|
The match context
|
|
</b><br>
|
|
<P>
|
|
A match context is required if you want to change the default values of any
|
|
of the following match-time parameters:
|
|
<pre>
|
|
A callout function
|
|
The offset limit for matching an unanchored pattern
|
|
The limit for calling <b>match()</b> (see below)
|
|
The limit for calling <b>match()</b> recursively
|
|
</pre>
|
|
A match context is also required if you are using custom memory management.
|
|
If none of these apply, just pass NULL as the context argument of
|
|
<b>pcre2_match()</b>, <b>pcre2_dfa_match()</b>, or <b>pcre2_jit_match()</b>.
|
|
</P>
|
|
<P>
|
|
A match context is created, copied, and freed by the following functions:
|
|
<b>pcre2_match_context *pcre2_match_context_create(</b>
|
|
<b> pcre2_general_context *<i>gcontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>pcre2_match_context *pcre2_match_context_copy(</b>
|
|
<b> pcre2_match_context *<i>mcontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>void pcre2_match_context_free(pcre2_match_context *<i>mcontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
A match context is created with default values for its parameters. These can
|
|
be changed by calling the following functions, which return 0 on success, or
|
|
PCRE2_ERROR_BADDATA if invalid data is detected.
|
|
<b>int pcre2_set_callout(pcre2_match_context *<i>mcontext</i>,</b>
|
|
<b> int (*<i>callout_function</i>)(pcre2_callout_block *, void *),</b>
|
|
<b> void *<i>callout_data</i>);</b>
|
|
<br>
|
|
<br>
|
|
This sets up a "callout" function, which PCRE2 will call at specified points
|
|
during a matching operation. Details are given in the
|
|
<a href="pcre2callout.html"><b>pcre2callout</b></a>
|
|
documentation.
|
|
<b>int pcre2_set_offset_limit(pcre2_match_context *<i>mcontext</i>,</b>
|
|
<b> PCRE2_SIZE <i>value</i>);</b>
|
|
<br>
|
|
<br>
|
|
The <i>offset_limit</i> parameter limits how far an unanchored search can
|
|
advance in the subject string. The default value is PCRE2_UNSET. The
|
|
<b>pcre2_match()</b> and <b>pcre2_dfa_match()</b> functions return
|
|
PCRE2_ERROR_NOMATCH if a match with a starting point before or at the given
|
|
offset is not found. For example, if the pattern /abc/ is matched against
|
|
"123abc" with an offset limit less than 3, the result is PCRE2_ERROR_NO_MATCH.
|
|
A match can never be found if the <i>startoffset</i> argument of
|
|
<b>pcre2_match()</b> or <b>pcre2_dfa_match()</b> is greater than the offset
|
|
limit.
|
|
</P>
|
|
<P>
|
|
When using this facility, you must set PCRE2_USE_OFFSET_LIMIT when calling
|
|
<b>pcre2_compile()</b> so that when JIT is in use, different code can be
|
|
compiled. If a match is started with a non-default match limit when
|
|
PCRE2_USE_OFFSET_LIMIT is not set, an error is generated.
|
|
</P>
|
|
<P>
|
|
The offset limit facility can be used to track progress when searching large
|
|
subject strings. See also the PCRE2_FIRSTLINE option, which requires a match to
|
|
start within the first line of the subject. If this is set with an offset
|
|
limit, a match must occur in the first line and also within the offset limit.
|
|
In other words, whichever limit comes first is used.
|
|
<b>int pcre2_set_match_limit(pcre2_match_context *<i>mcontext</i>,</b>
|
|
<b> uint32_t <i>value</i>);</b>
|
|
<br>
|
|
<br>
|
|
The <i>match_limit</i> parameter provides a means of preventing PCRE2 from using
|
|
up too many resources when processing 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>pcre2_match()</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. This limit is not relevant to <b>pcre2_dfa_match()</b>,
|
|
which ignores it.
|
|
</P>
|
|
<P>
|
|
When <b>pcre2_match()</b> is called with a pattern that was successfully
|
|
processed by <b>pcre2_jit_compile()</b>, the way in which 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 PCRE2 is built; the default
|
|
default is 10 million, which handles all but the most extreme cases. If the
|
|
limit is exceeded, <b>pcre2_match()</b> returns PCRE2_ERROR_MATCHLIMIT. 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=ddd)
|
|
</pre>
|
|
where ddd is a decimal number. However, such a setting is ignored unless ddd is
|
|
less than the limit set by the caller of <b>pcre2_match()</b> or, if no such
|
|
limit is set, less than the default.
|
|
<b>int pcre2_set_recursion_limit(pcre2_match_context *<i>mcontext</i>,</b>
|
|
<b> uint32_t <i>value</i>);</b>
|
|
<br>
|
|
<br>
|
|
The <i>recursion_limit</i> parameter 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 system stack that can be
|
|
used, or, when PCRE2 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. However, it is
|
|
supported by <b>pcre2_dfa_match()</b>, which uses recursive function calls less
|
|
frequently than <b>pcre2_match()</b>, but which can be caused to use a lot of
|
|
stack by a recursive pattern such as /(.)(?1)/ matched to a very long string.
|
|
</P>
|
|
<P>
|
|
The default value for <i>recursion_limit</i> can be set when PCRE2 is built; the
|
|
default default is the same value as the default for <i>match_limit</i>. If the
|
|
limit is exceeded, <b>pcre2_match()</b> and <b>pcre2_dfa_match()</b> return
|
|
PCRE2_ERROR_RECURSIONLIMIT. 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=ddd)
|
|
</pre>
|
|
where ddd is a decimal number. However, such a setting is ignored unless ddd is
|
|
less than the limit set by the caller of <b>pcre2_match()</b> or
|
|
<b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default.
|
|
<b>int pcre2_set_recursion_memory_management(</b>
|
|
<b> pcre2_match_context *<i>mcontext</i>,</b>
|
|
<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b>
|
|
<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b>
|
|
<br>
|
|
<br>
|
|
This function sets up two additional custom memory management functions for use
|
|
by <b>pcre2_match()</b> when PCRE2 is compiled to use the heap for remembering
|
|
backtracking data, instead of recursive function calls that use the system
|
|
stack. There is a discussion about PCRE2's stack usage in the
|
|
<a href="pcre2stack.html"><b>pcre2stack</b></a>
|
|
documentation. See the
|
|
<a href="pcre2build.html"><b>pcre2build</b></a>
|
|
documentation for details of how to build PCRE2.
|
|
</P>
|
|
<P>
|
|
Using the heap for recursion is a non-standard way of building PCRE2, for use
|
|
in environments that have limited stacks. Because of the greater use of memory
|
|
management, <b>pcre2_match()</b> runs more slowly. Functions that are different
|
|
to the general custom memory functions are provided so that special-purpose
|
|
external code can be used for this case, because the memory blocks are all the
|
|
same size. The blocks are retained by <b>pcre2_match()</b> until it is about to
|
|
exit so that they can be re-used when possible during the match. In the absence
|
|
of these functions, the normal custom memory management functions are used, if
|
|
supplied, otherwise the system functions.
|
|
</P>
|
|
<br><a name="SEC17" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br>
|
|
<P>
|
|
<b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b>
|
|
</P>
|
|
<P>
|
|
The function <b>pcre2_config()</b> makes it possible for a PCRE2 client to
|
|
discover which optional features have been compiled into the PCRE2 library. The
|
|
<a href="pcre2build.html"><b>pcre2build</b></a>
|
|
documentation has more details about these optional features.
|
|
</P>
|
|
<P>
|
|
The first argument for <b>pcre2_config()</b> specifies which information is
|
|
required. The second argument is a pointer to memory into which the information
|
|
is placed. If NULL is passed, the function returns the amount of memory that is
|
|
needed for the requested information. For calls that return numerical values,
|
|
the value is in bytes; when requesting these values, <i>where</i> should point
|
|
to appropriately aligned memory. For calls that return strings, the required
|
|
length is given in code units, not counting the terminating zero.
|
|
</P>
|
|
<P>
|
|
When requesting information, the returned value from <b>pcre2_config()</b> is
|
|
non-negative on success, or the negative error code PCRE2_ERROR_BADOPTION if
|
|
the value in the first argument is not recognized. The following information is
|
|
available:
|
|
<pre>
|
|
PCRE2_CONFIG_BSR
|
|
</pre>
|
|
The output is a uint32_t integer whose value indicates what character
|
|
sequences the \R escape sequence matches by default. A value of
|
|
PCRE2_BSR_UNICODE means that \R matches any Unicode line ending sequence; a
|
|
value of PCRE2_BSR_ANYCRLF means that \R matches only CR, LF, or CRLF. The
|
|
default can be overridden when a pattern is compiled.
|
|
<pre>
|
|
PCRE2_CONFIG_JIT
|
|
</pre>
|
|
The output is a uint32_t integer that is set to one if support for just-in-time
|
|
compiling is available; otherwise it is set to zero.
|
|
<pre>
|
|
PCRE2_CONFIG_JITTARGET
|
|
</pre>
|
|
The <i>where</i> argument should point to a buffer that is at least 48 code
|
|
units long. (The exact length required can be found by calling
|
|
<b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with a
|
|
string that 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, PCRE2_ERROR_BADOPTION is returned, otherwise the number of
|
|
code units used is returned. This is the length of the string, plus one unit
|
|
for the terminating zero.
|
|
<pre>
|
|
PCRE2_CONFIG_LINKSIZE
|
|
</pre>
|
|
The output is a uint32_t integer that contains the number of bytes used for
|
|
internal linkage in compiled regular expressions. When PCRE2 is configured, the
|
|
value can be set to 2, 3, or 4, with the default being 2. This is the value
|
|
that is returned by <b>pcre2_config()</b>. However, when the 16-bit library is
|
|
compiled, a value of 3 is rounded up to 4, and when the 32-bit library is
|
|
compiled, internal linkages always use 4 bytes, so the configured value is not
|
|
relevant.
|
|
</P>
|
|
<P>
|
|
The default value of 2 for the 8-bit and 16-bit libraries is sufficient for all
|
|
but the most massive patterns, since it allows the size of the compiled pattern
|
|
to be up to 64K code units. Larger values allow larger regular expressions to
|
|
be compiled by those two libraries, but at the expense of slower matching.
|
|
<pre>
|
|
PCRE2_CONFIG_MATCHLIMIT
|
|
</pre>
|
|
The output is a uint32_t integer that gives the default limit for the number of
|
|
internal matching function calls in a <b>pcre2_match()</b> execution. Further
|
|
details are given with <b>pcre2_match()</b> below.
|
|
<pre>
|
|
PCRE2_CONFIG_NEWLINE
|
|
</pre>
|
|
The output is a uint32_t integer whose value specifies the default character
|
|
sequence that is recognized as meaning "newline". The values are:
|
|
<pre>
|
|
PCRE2_NEWLINE_CR Carriage return (CR)
|
|
PCRE2_NEWLINE_LF Linefeed (LF)
|
|
PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF)
|
|
PCRE2_NEWLINE_ANY Any Unicode line ending
|
|
PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF
|
|
</pre>
|
|
The default should normally correspond to the standard sequence for your
|
|
operating system.
|
|
<pre>
|
|
PCRE2_CONFIG_PARENSLIMIT
|
|
</pre>
|
|
The output is a uint32_t 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
|
|
PCRE2 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, see <b>pcre2_set_compile_recursion_guard()</b>.
|
|
<pre>
|
|
PCRE2_CONFIG_RECURSIONLIMIT
|
|
</pre>
|
|
The output is a uint32_t integer that gives the default limit for the depth of
|
|
recursion when calling the internal matching function in a <b>pcre2_match()</b>
|
|
execution. Further details are given with <b>pcre2_match()</b> below.
|
|
<pre>
|
|
PCRE2_CONFIG_STACKRECURSE
|
|
</pre>
|
|
The output is a uint32_t integer that is set to one if internal recursion when
|
|
running <b>pcre2_match()</b> is implemented by recursive function calls that use
|
|
the system stack to remember their state. This is the usual way that PCRE2 is
|
|
compiled. The output is zero if PCRE2 was compiled to use blocks of data on the
|
|
heap instead of recursive function calls.
|
|
<pre>
|
|
PCRE2_CONFIG_UNICODE_VERSION
|
|
</pre>
|
|
The <i>where</i> argument should point to a buffer that is at least 24 code
|
|
units long. (The exact length required can be found by calling
|
|
<b>pcre2_config()</b> with <b>where</b> set to NULL.) If PCRE2 has been compiled
|
|
without Unicode support, the buffer is filled with the text "Unicode not
|
|
supported". Otherwise, the Unicode version string (for example, "8.0.0") is
|
|
inserted. The number of code units used is returned. This is the length of the
|
|
string plus one unit for the terminating zero.
|
|
<pre>
|
|
PCRE2_CONFIG_UNICODE
|
|
</pre>
|
|
The output is a uint32_t integer that is set to one if Unicode support is
|
|
available; otherwise it is set to zero. Unicode support implies UTF support.
|
|
<pre>
|
|
PCRE2_CONFIG_VERSION
|
|
</pre>
|
|
The <i>where</i> argument should point to a buffer that is at least 12 code
|
|
units long. (The exact length required can be found by calling
|
|
<b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with
|
|
the PCRE2 version string, zero-terminated. The number of code units used is
|
|
returned. This is the length of the string plus one unit for the terminating
|
|
zero.
|
|
<a name="compiling"></a></P>
|
|
<br><a name="SEC18" href="#TOC1">COMPILING A PATTERN</a><br>
|
|
<P>
|
|
<b>pcre2_code *pcre2_compile(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b>
|
|
<b> uint32_t <i>options</i>, int *<i>errorcode</i>, PCRE2_SIZE *<i>erroroffset,</i></b>
|
|
<b> pcre2_compile_context *<i>ccontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>void pcre2_code_free(pcre2_code *<i>code</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>pcre2_code *pcre2_code_copy(const pcre2_code *<i>code</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *<i>code</i>);</b>
|
|
</P>
|
|
<P>
|
|
The <b>pcre2_compile()</b> function compiles a pattern into an internal form.
|
|
The pattern is defined by a pointer to a string of code units and a length. If
|
|
the pattern is zero-terminated, the length can be specified as
|
|
PCRE2_ZERO_TERMINATED. The function returns a pointer to a block of memory that
|
|
contains the compiled pattern and related data, or NULL if an error occurred.
|
|
</P>
|
|
<P>
|
|
If the compile context argument <i>ccontext</i> is NULL, memory for the compiled
|
|
pattern is obtained by calling <b>malloc()</b>. Otherwise, it is obtained from
|
|
the same memory function that was used for the compile context. The caller must
|
|
free the memory by calling <b>pcre2_code_free()</b> when it is no longer needed.
|
|
</P>
|
|
<P>
|
|
The function <b>pcre2_code_copy()</b> makes a copy of the compiled code in new
|
|
memory, using the same memory allocator as was used for the original. However,
|
|
if the code has been processed by the JIT compiler (see
|
|
<a href="#jitcompiling">below),</a>
|
|
the JIT information cannot be copied (because it is position-dependent).
|
|
The new copy can initially be used only for non-JIT matching, though it can be
|
|
passed to <b>pcre2_jit_compile()</b> if required.
|
|
</P>
|
|
<P>
|
|
The <b>pcre2_code_copy()</b> function provides a way for individual threads in a
|
|
multithreaded application to acquire a private copy of shared compiled code.
|
|
However, it does not make a copy of the character tables used by the compiled
|
|
pattern; the new pattern code points to the same tables as the original code.
|
|
(See
|
|
<a href="#jitcompiling">"Locale Support"</a>
|
|
below for details of these character tables.) In many applications the same
|
|
tables are used throughout, so this behaviour is appropriate. Nevertheless,
|
|
there are occasions when a copy of a compiled pattern and the relevant tables
|
|
are needed. The <b>pcre2_code_copy_with_tables()</b> provides this facility.
|
|
Copies of both the code and the tables are made, with the new code pointing to
|
|
the new tables. The memory for the new tables is automatically freed when
|
|
<b>pcre2_code_free()</b> is called for the new copy of the compiled code.
|
|
</P>
|
|
<P>
|
|
NOTE: When one of the matching functions is called, pointers to the compiled
|
|
pattern and the subject string are set in the match data block so that they can
|
|
be referenced by the substring extraction functions. After running a match, you
|
|
must not free a compiled pattern (or a subject string) until after all
|
|
operations on the
|
|
<a href="#matchdatablock">match data block</a>
|
|
have taken place.
|
|
</P>
|
|
<P>
|
|
The <i>options</i> argument for <b>pcre2_compile()</b> 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="pcre2pattern.html"><b>pcre2pattern</b></a>
|
|
documentation).
|
|
</P>
|
|
<P>
|
|
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. The PCRE2_ANCHORED and PCRE2_NO_UTF_CHECK options can be set at
|
|
the time of matching as well as at compile time.
|
|
</P>
|
|
<P>
|
|
Other, less frequently required compile-time parameters (for example, the
|
|
newline setting) can be provided in a compile context (as described
|
|
<a href="#compilecontext">above).</a>
|
|
</P>
|
|
<P>
|
|
If <i>errorcode</i> or <i>erroroffset</i> is NULL, <b>pcre2_compile()</b> returns
|
|
NULL immediately. Otherwise, the variables to which these point are set to an
|
|
error code and an offset (number of code units) within the pattern,
|
|
respectively, when <b>pcre2_compile()</b> returns NULL because a compilation
|
|
error has occurred. The values are not defined when compilation is successful
|
|
and <b>pcre2_compile()</b> returns a non-NULL value.
|
|
</P>
|
|
<P>
|
|
The value returned in <i>erroroffset</i> is an indication of where in the
|
|
pattern the error occurred. It is not necessarily the furthest point in the
|
|
pattern that was read. For example, after the error "lookbehind assertion is
|
|
not fixed length", the error offset points to the start of the failing
|
|
assertion.
|
|
</P>
|
|
<P>
|
|
The <b>pcre2_get_error_message()</b> function (see "Obtaining a textual error
|
|
message"
|
|
<a href="#geterrormessage">below)</a>
|
|
provides a textual message for each error code. Compilation errors have
|
|
positive error codes; UTF formatting error codes are negative. For an invalid
|
|
UTF-8 or UTF-16 string, the offset is that of the first code 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 code 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>
|
|
This code fragment shows a typical straightforward call to
|
|
<b>pcre2_compile()</b>:
|
|
<pre>
|
|
pcre2_code *re;
|
|
PCRE2_SIZE erroffset;
|
|
int errorcode;
|
|
re = pcre2_compile(
|
|
"^A.*Z", /* the pattern */
|
|
PCRE2_ZERO_TERMINATED, /* the pattern is zero-terminated */
|
|
0, /* default options */
|
|
&errorcode, /* for error code */
|
|
&erroffset, /* for error offset */
|
|
NULL); /* no compile context */
|
|
</pre>
|
|
The following names for option bits are defined in the <b>pcre2.h</b> header
|
|
file:
|
|
<pre>
|
|
PCRE2_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>
|
|
PCRE2_ALLOW_EMPTY_CLASS
|
|
</pre>
|
|
By default, for compatibility with Perl, a closing square bracket that
|
|
immediately follows an opening one is treated as a data character for the
|
|
class. When PCRE2_ALLOW_EMPTY_CLASS is set, it terminates the class, which
|
|
therefore contains no characters and so can never match.
|
|
<pre>
|
|
PCRE2_ALT_BSUX
|
|
</pre>
|
|
This option request alternative handling of three escape sequences, which
|
|
makes PCRE2's behaviour more like ECMAscript (aka JavaScript). When it is set:
|
|
</P>
|
|
<P>
|
|
(1) \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>
|
|
(2) \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>
|
|
(3) \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>
|
|
PCRE2_ALT_CIRCUMFLEX
|
|
</pre>
|
|
In multiline mode (when PCRE2_MULTILINE is set), the circumflex metacharacter
|
|
matches at the start of the subject (unless PCRE2_NOTBOL is set), and also
|
|
after any internal newline. However, it does not match after a newline at the
|
|
end of the subject, for compatibility with Perl. If you want a multiline
|
|
circumflex also to match after a terminating newline, you must set
|
|
PCRE2_ALT_CIRCUMFLEX.
|
|
<pre>
|
|
PCRE2_ALT_VERBNAMES
|
|
</pre>
|
|
By default, for compatibility with Perl, the name in any verb sequence such as
|
|
(*MARK:NAME) is any sequence of characters that does not include a closing
|
|
parenthesis. The name is not processed in any way, and it is not possible to
|
|
include a closing parenthesis in the name. However, if the PCRE2_ALT_VERBNAMES
|
|
option is set, normal backslash processing is applied to verb names and only an
|
|
unescaped closing parenthesis terminates the name. A closing parenthesis can be
|
|
included in a name either as \) or between \Q and \E. If the PCRE2_EXTENDED
|
|
option is set, unescaped whitespace in verb names is skipped and #-comments are
|
|
recognized, exactly as in the rest of the pattern.
|
|
<pre>
|
|
PCRE2_AUTO_CALLOUT
|
|
</pre>
|
|
If this bit is set, <b>pcre2_compile()</b> automatically inserts callout items,
|
|
all with number 255, before each pattern item, except immediately before or
|
|
after a callout in the pattern. For discussion of the callout facility, see the
|
|
<a href="pcre2callout.html"><b>pcre2callout</b></a>
|
|
documentation.
|
|
<pre>
|
|
PCRE2_CASELESS
|
|
</pre>
|
|
If this bit is set, letters in the pattern match both upper and lower case
|
|
letters in the subject. It is equivalent to Perl's /i option, and it can be
|
|
changed within a pattern by a (?i) option setting.
|
|
<pre>
|
|
PCRE2_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 PCRE2_DOLLAR_ENDONLY option is ignored if PCRE2_MULTILINE is
|
|
set. There is no equivalent to this option in Perl, and no way to set it within
|
|
a pattern.
|
|
<pre>
|
|
PCRE2_DOTALL
|
|
</pre>
|
|
If this bit is set, a dot metacharacter in the pattern matches any character,
|
|
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 in the subject 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>
|
|
PCRE2_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="pcre2pattern.html"><b>pcre2pattern</b></a>
|
|
documentation.
|
|
<pre>
|
|
PCRE2_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 numerical quantifiers such as {1,3}.
|
|
Ignorable white space is permitted between an item and a following quantifier
|
|
and between a quantifier and a following + that indicates possessiveness.
|
|
</P>
|
|
<P>
|
|
PCRE2_EXTENDED also causes characters between an unescaped # outside a
|
|
character class and the next newline, inclusive, to be ignored, which makes it
|
|
possible to include comments inside complicated patterns. 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. PCRE2_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 can be specified by a setting in
|
|
the compile context that is passed to <b>pcre2_compile()</b> or by a special
|
|
sequence at the start of the pattern, as described in the section entitled
|
|
<a href="pcre2pattern.html#newlines">"Newline conventions"</a>
|
|
in the <b>pcre2pattern</b> documentation. A default is defined when PCRE2 is
|
|
built.
|
|
<pre>
|
|
PCRE2_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. See also PCRE2_USE_OFFSET_LIMIT, which provides a more
|
|
general limiting facility. If PCRE2_FIRSTLINE is set with an offset limit, a
|
|
match must occur in the first line and also within the offset limit. In other
|
|
words, whichever limit comes first is used.
|
|
<pre>
|
|
PCRE2_MATCH_UNSET_BACKREF
|
|
</pre>
|
|
If this option is set, 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. Setting this option makes PCRE2 behave more like ECMAscript (aka
|
|
JavaScript).
|
|
<pre>
|
|
PCRE2_MULTILINE
|
|
</pre>
|
|
By default, for the purposes of matching "start of line" and "end of line",
|
|
PCRE2 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 PCRE2_DOLLAR_ENDONLY is set). Note, however, that unless
|
|
PCRE2_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 PCRE2_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. Note that the "start of line" metacharacter does not match
|
|
after a newline at the end of the subject, for compatibility with Perl.
|
|
However, you can change this by setting the PCRE2_ALT_CIRCUMFLEX option. If
|
|
there are no newlines in a subject string, or no occurrences of ^ or $ in a
|
|
pattern, setting PCRE2_MULTILINE has no effect.
|
|
<pre>
|
|
PCRE2_NEVER_BACKSLASH_C
|
|
</pre>
|
|
This option locks out the use of \C in the pattern that is being compiled.
|
|
This escape can cause unpredictable behaviour in UTF-8 or UTF-16 modes, because
|
|
it may leave the current matching point in the middle of a multi-code-unit
|
|
character. This option may be useful in applications that process patterns from
|
|
external sources. Note that there is also a build-time option that permanently
|
|
locks out the use of \C.
|
|
<pre>
|
|
PCRE2_NEVER_UCP
|
|
</pre>
|
|
This option locks out the use of Unicode properties for handling \B, \b, \D,
|
|
\d, \S, \s, \W, \w, and some of the POSIX character classes, as described
|
|
for the PCRE2_UCP option below. In particular, it prevents the creator of the
|
|
pattern from enabling this facility by starting the pattern with (*UCP). This
|
|
option may be useful in applications that process patterns from external
|
|
sources. The option combination PCRE_UCP and PCRE_NEVER_UCP causes an error.
|
|
<pre>
|
|
PCRE2_NEVER_UTF
|
|
</pre>
|
|
This option locks out interpretation of the pattern as UTF-8, UTF-16, or
|
|
UTF-32, depending on which library is in use. In particular, it prevents the
|
|
creator of the pattern from switching to UTF interpretation by starting the
|
|
pattern with (*UTF). This option may be useful in applications that process
|
|
patterns from external sources. The combination of PCRE2_UTF and
|
|
PCRE2_NEVER_UTF causes an error.
|
|
<pre>
|
|
PCRE2_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. Note that, if this option is set, references to capturing groups (back
|
|
references or recursion/subroutine calls) may only refer to named groups,
|
|
though the reference can be by name or by number.
|
|
<pre>
|
|
PCRE2_NO_AUTO_POSSESS
|
|
</pre>
|
|
If this option is set, it disables "auto-possessification", which 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 callouts 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>
|
|
PCRE2_NO_DOTSTAR_ANCHOR
|
|
</pre>
|
|
If this option is set, it disables an optimization that is applied when .* is
|
|
the first significant item in a top-level branch of a pattern, and all the
|
|
other branches also start with .* or with \A or \G or ^. The optimization is
|
|
automatically disabled for .* if it is inside an atomic group or a capturing
|
|
group that is the subject of a back reference, or if the pattern contains
|
|
(*PRUNE) or (*SKIP). When the optimization is not disabled, such a pattern is
|
|
automatically anchored if PCRE2_DOTALL is set for all the .* items and
|
|
PCRE2_MULTILINE is not set for any ^ items. Otherwise, the fact that any match
|
|
must start either at the start of the subject or following a newline is
|
|
remembered. Like other optimizations, this can cause callouts to be skipped.
|
|
<pre>
|
|
PCRE2_NO_START_OPTIMIZE
|
|
</pre>
|
|
This is an option whose main effect is at matching time. It does not change
|
|
what <b>pcre2_compile()</b> generates, but it does affect the output of the JIT
|
|
compiler.
|
|
</P>
|
|
<P>
|
|
There are a number of optimizations that may occur 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, the matching code 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 PCRE2_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.
|
|
</P>
|
|
<P>
|
|
Setting PCRE2_NO_START_OPTIMIZE may change the outcome of a matching operation.
|
|
Consider the pattern
|
|
<pre>
|
|
(*COMMIT)ABC
|
|
</pre>
|
|
When this is compiled, PCRE2 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 PCRE2_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". There are also other start-up optimizations.
|
|
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", and "C". An attempt to match an empty
|
|
string at the end of the subject does not take place, because PCRE2 knows that
|
|
the subject is now too short, and so the (*MARK) is never encountered. In this
|
|
case, the optimization does not affect the overall match result, which is still
|
|
"no match", but it does affect the auxiliary information that is returned.
|
|
<pre>
|
|
PCRE2_NO_UTF_CHECK
|
|
</pre>
|
|
When PCRE2_UTF is set, the validity of the pattern as a UTF string is
|
|
automatically checked. There are discussions about the validity of
|
|
<a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a>
|
|
<a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a>
|
|
and
|
|
<a href="pcre2unicode.html#utf32strings">UTF-32 strings</a>
|
|
in the
|
|
<a href="pcre2unicode.html"><b>pcre2unicode</b></a>
|
|
document.
|
|
If an invalid UTF sequence is found, <b>pcre2_compile()</b> returns a negative
|
|
error code.
|
|
</P>
|
|
<P>
|
|
If you know that your pattern is valid, and you want to skip this check for
|
|
performance reasons, you can set the PCRE2_NO_UTF_CHECK option. When it is set,
|
|
the effect of passing an invalid UTF 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>pcre2_match()</b> and <b>pcre_dfa_match()</b>, to suppress validity
|
|
checking of the subject string.
|
|
<pre>
|
|
PCRE2_UCP
|
|
</pre>
|
|
This option changes the way PCRE2 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 PCRE2_UCP is set, Unicode properties are used instead to
|
|
classify characters. More details are given in the section on
|
|
<a href="pcre2pattern.html#genericchartypes">generic character types</a>
|
|
in the
|
|
<a href="pcre2pattern.html"><b>pcre2pattern</b></a>
|
|
page. If you set PCRE2_UCP, matching one of the items it affects takes much
|
|
longer. The option is available only if PCRE2 has been compiled with Unicode
|
|
support.
|
|
<pre>
|
|
PCRE2_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>
|
|
PCRE2_USE_OFFSET_LIMIT
|
|
</pre>
|
|
This option must be set for <b>pcre2_compile()</b> if
|
|
<b>pcre2_set_offset_limit()</b> is going to be used to set a non-default offset
|
|
limit in a match context for matches that use this pattern. An error is
|
|
generated if an offset limit is set without this option. For more details, see
|
|
the description of <b>pcre2_set_offset_limit()</b> in the
|
|
<a href="#matchcontext">section</a>
|
|
that describes match contexts. See also the PCRE2_FIRSTLINE
|
|
option above.
|
|
<pre>
|
|
PCRE2_UTF
|
|
</pre>
|
|
This option causes PCRE2 to regard both the pattern and the subject strings
|
|
that are subsequently processed as strings of UTF characters instead of
|
|
single-code-unit strings. It is available when PCRE2 is built to include
|
|
Unicode support (which is the default). If Unicode support is not available,
|
|
the use of this option provokes an error. Details of how this option changes
|
|
the behaviour of PCRE2 are given in the
|
|
<a href="pcre2unicode.html"><b>pcre2unicode</b></a>
|
|
page.
|
|
</P>
|
|
<br><a name="SEC19" href="#TOC1">COMPILATION ERROR CODES</a><br>
|
|
<P>
|
|
There are over 80 positive error codes that <b>pcre2_compile()</b> may return
|
|
(via <i>errorcode</i>) if it finds an error in the pattern. There are also some
|
|
negative error codes that are used for invalid UTF strings. These are the same
|
|
as given by <b>pcre2_match()</b> and <b>pcre2_dfa_match()</b>, and are described
|
|
in the
|
|
<a href="pcre2unicode.html"><b>pcre2unicode</b></a>
|
|
page. The <b>pcre2_get_error_message()</b> function (see "Obtaining a textual
|
|
error message"
|
|
<a href="#geterrormessage">below)</a>
|
|
can be called to obtain a textual error message from any error code.
|
|
<a name="jitcompiling"></a></P>
|
|
<br><a name="SEC20" href="#TOC1">JUST-IN-TIME (JIT) COMPILATION</a><br>
|
|
<P>
|
|
<b>int pcre2_jit_compile(pcre2_code *<i>code</i>, uint32_t <i>options</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>int pcre2_jit_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b>
|
|
<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b>
|
|
<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b>
|
|
<b> pcre2_match_context *<i>mcontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>void pcre2_jit_free_unused_memory(pcre2_general_context *<i>gcontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>pcre2_jit_stack *pcre2_jit_stack_create(PCRE2_SIZE <i>startsize</i>,</b>
|
|
<b> PCRE2_SIZE <i>maxsize</i>, pcre2_general_context *<i>gcontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>void pcre2_jit_stack_assign(pcre2_match_context *<i>mcontext</i>,</b>
|
|
<b> pcre2_jit_callback <i>callback_function</i>, void *<i>callback_data</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>void pcre2_jit_stack_free(pcre2_jit_stack *<i>jit_stack</i>);</b>
|
|
</P>
|
|
<P>
|
|
These functions provide support for JIT compilation, which, if the just-in-time
|
|
compiler is available, further processes a compiled pattern into machine code
|
|
that executes much faster than the <b>pcre2_match()</b> interpretive matching
|
|
function. Full details are given in the
|
|
<a href="pcre2jit.html"><b>pcre2jit</b></a>
|
|
documentation.
|
|
</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 compilation time.
|
|
Most, but not all patterns can be optimized by the JIT compiler.
|
|
<a name="localesupport"></a></P>
|
|
<br><a name="SEC21" href="#TOC1">LOCALE SUPPORT</a><br>
|
|
<P>
|
|
PCRE2 handles caseless matching, and determines whether characters are letters,
|
|
digits, or whatever, by reference to a set of tables, indexed by character code
|
|
point. This applies only to characters whose code points are less than 256. By
|
|
default, higher-valued code points never match escapes such as \w or \d.
|
|
However, if PCRE2 is built with UTF support, all characters can be tested with
|
|
\p and \P, or, alternatively, the PCRE2_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>
|
|
PCRE2 contains an internal set of character tables that are used by default.
|
|
These are sufficient for many applications. Normally, the internal tables
|
|
recognize only ASCII characters. However, when PCRE2 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 be overridden by tables supplied by the application
|
|
that calls PCRE2. 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>pcre2_maketables()</b> function, in
|
|
the relevant locale. The result can be passed to <b>pcre2_compile()</b> as often
|
|
as necessary, by creating a compile context and calling
|
|
<b>pcre2_set_character_tables()</b> to set the tables pointer therein. 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 = pcre2_maketables(NULL);
|
|
ccontext = pcre2_compile_context_create(NULL);
|
|
pcre2_set_character_tables(ccontext, tables);
|
|
re = pcre2_compile(..., ccontext);
|
|
</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". 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 (via the compile context) to <b>pcre2_compile()</b>
|
|
is saved with the compiled pattern, and the same tables are used by
|
|
<b>pcre2_match()</b> and <b>pcre_dfa_match()</b>. Thus, for any single pattern,
|
|
compilation, and matching all happen in the same locale, but different patterns
|
|
can be processed in different locales.
|
|
<a name="infoaboutpattern"></a></P>
|
|
<br><a name="SEC22" href="#TOC1">INFORMATION ABOUT A COMPILED PATTERN</a><br>
|
|
<P>
|
|
<b>int pcre2_pattern_info(const pcre2 *<i>code</i>, uint32_t <i>what</i>, void *<i>where</i>);</b>
|
|
</P>
|
|
<P>
|
|
The <b>pcre2_pattern_info()</b> function returns general information about a
|
|
compiled pattern. For information about callouts, see the
|
|
<a href="pcre2pattern.html#infoaboutcallouts">next section.</a>
|
|
The first argument for <b>pcre2_pattern_info()</b> is a pointer to the compiled
|
|
pattern. The second argument specifies which piece of information is required,
|
|
and the third argument is a pointer to a variable to receive the data. If the
|
|
third argument is NULL, the first argument is ignored, and the function returns
|
|
the size in bytes of the variable that is required for the information
|
|
requested. Otherwise, The yield of the function is zero for success, or one of
|
|
the following negative numbers:
|
|
<pre>
|
|
PCRE2_ERROR_NULL the argument <i>code</i> was NULL
|
|
PCRE2_ERROR_BADMAGIC the "magic number" was not found
|
|
PCRE2_ERROR_BADOPTION the value of <i>what</i> was invalid
|
|
PCRE2_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. Here is a typical call of
|
|
<b>pcre2_pattern_info()</b>, to obtain the length of the compiled pattern:
|
|
<pre>
|
|
int rc;
|
|
size_t length;
|
|
rc = pcre2_pattern_info(
|
|
re, /* result of pcre2_compile() */
|
|
PCRE2_INFO_SIZE, /* what is required */
|
|
&length); /* where to put the data */
|
|
</pre>
|
|
The possible values for the second argument are defined in <b>pcre2.h</b>, and
|
|
are as follows:
|
|
<pre>
|
|
PCRE2_INFO_ALLOPTIONS
|
|
PCRE2_INFO_ARGOPTIONS
|
|
</pre>
|
|
Return a copy of the pattern's options. The third argument should point to a
|
|
<b>uint32_t</b> variable. PCRE2_INFO_ARGOPTIONS returns exactly the options that
|
|
were passed to <b>pcre2_compile()</b>, whereas PCRE2_INFO_ALLOPTIONS returns
|
|
the compile options as modified by any top-level (*XXX) option settings such as
|
|
(*UTF) at the start of the pattern itself.
|
|
</P>
|
|
<P>
|
|
For example, if the pattern /(*UTF)abc/ is compiled with the PCRE2_EXTENDED
|
|
option, the result for PCRE2_INFO_ALLOPTIONS is PCRE2_EXTENDED and PCRE2_UTF.
|
|
Option settings such as (?i) that can change within a pattern do not affect the
|
|
result of PCRE2_INFO_ALLOPTIONS, even if they appear right at the start of the
|
|
pattern. (This was different in some earlier releases.)
|
|
</P>
|
|
<P>
|
|
A pattern compiled without PCRE2_ANCHORED is automatically anchored by PCRE2 if
|
|
the first significant item in every top-level branch is one of the following:
|
|
<pre>
|
|
^ unless PCRE2_MULTILINE is set
|
|
\A always
|
|
\G always
|
|
.* sometimes - see below
|
|
</pre>
|
|
When .* is the first significant item, anchoring is possible only when all the
|
|
following are true:
|
|
<pre>
|
|
.* is not in an atomic group
|
|
.* is not in a capturing group that is the subject of a back reference
|
|
PCRE2_DOTALL is in force for .*
|
|
Neither (*PRUNE) nor (*SKIP) appears in the pattern.
|
|
PCRE2_NO_DOTSTAR_ANCHOR is not set.
|
|
</pre>
|
|
For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in the
|
|
options returned for PCRE2_INFO_ALLOPTIONS.
|
|
<pre>
|
|
PCRE2_INFO_BACKREFMAX
|
|
</pre>
|
|
Return the number of the highest back reference in the pattern. The third
|
|
argument should point to an <b>uint32_t</b> variable. Named subpatterns acquire
|
|
numbers as well as names, and these count towards the highest back reference.
|
|
Back references such as \4 or \g{12} match the captured characters of the
|
|
given group, but in addition, the check that a capturing group is set in a
|
|
conditional subpattern such as (?(3)a|b) is also a back reference. Zero is
|
|
returned if there are no back references.
|
|
<pre>
|
|
PCRE2_INFO_BSR
|
|
</pre>
|
|
The output is a uint32_t whose value indicates what character sequences the \R
|
|
escape sequence matches. A value of PCRE2_BSR_UNICODE means that \R matches
|
|
any Unicode line ending sequence; a value of PCRE2_BSR_ANYCRLF means that \R
|
|
matches only CR, LF, or CRLF.
|
|
<pre>
|
|
PCRE2_INFO_CAPTURECOUNT
|
|
</pre>
|
|
Return the highest capturing subpattern number in the pattern. In patterns
|
|
where (?| is not used, this is also the total number of capturing subpatterns.
|
|
The third argument should point to an <b>uint32_t</b> variable.
|
|
<pre>
|
|
PCRE2_INFO_FIRSTBITMAP
|
|
</pre>
|
|
In the absence of a single first code unit for a non-anchored pattern,
|
|
<b>pcre2_compile()</b> may construct a 256-bit table that defines a fixed set of
|
|
values for the first code unit in any match. For example, a pattern that starts
|
|
with [abc] results in a table with three bits set. When code unit values
|
|
greater than 255 are supported, the flag bit for 255 means "any code unit of
|
|
value 255 or above". If such a table was constructed, a pointer to it is
|
|
returned. Otherwise NULL is returned. The third argument should point to an
|
|
<b>const uint8_t *</b> variable.
|
|
<pre>
|
|
PCRE2_INFO_FIRSTCODETYPE
|
|
</pre>
|
|
Return information about the first code unit of any matched string, for a
|
|
non-anchored pattern. The third argument should point to an <b>uint32_t</b>
|
|
variable. 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 PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed first value, but
|
|
it is known that a match can occur only at the start of the subject or
|
|
following a newline in the subject, 2 is returned. Otherwise, and for anchored
|
|
patterns, 0 is returned.
|
|
<pre>
|
|
PCRE2_INFO_FIRSTCODEUNIT
|
|
</pre>
|
|
Return the value of the first code unit of any matched string in the situation
|
|
where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0. The third
|
|
argument should point to an <b>uint32_t</b> variable. 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>
|
|
PCRE2_INFO_HASBACKSLASHC
|
|
</pre>
|
|
Return 1 if the pattern contains any instances of \C, otherwise 0. The third
|
|
argument should point to an <b>uint32_t</b> variable.
|
|
<pre>
|
|
PCRE2_INFO_HASCRORLF
|
|
</pre>
|
|
Return 1 if the pattern contains any explicit matches for CR or LF characters,
|
|
otherwise 0. The third argument should point to an <b>uint32_t</b> variable. An
|
|
explicit match is either a literal CR or LF character, or \r or \n.
|
|
<pre>
|
|
PCRE2_INFO_JCHANGED
|
|
</pre>
|
|
Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
|
|
0. The third argument should point to an <b>uint32_t</b> variable. (?J) and
|
|
(?-J) set and unset the local PCRE2_DUPNAMES option, respectively.
|
|
<pre>
|
|
PCRE2_INFO_JITSIZE
|
|
</pre>
|
|
If the compiled pattern was successfully processed by
|
|
<b>pcre2_jit_compile()</b>, return the size of the JIT compiled code, otherwise
|
|
return zero. The third argument should point to a <b>size_t</b> variable.
|
|
<pre>
|
|
PCRE2_INFO_LASTCODETYPE
|
|
</pre>
|
|
Returns 1 if there is a rightmost literal code unit that must exist in any
|
|
matched string, other than at its start. The third argument should point to an
|
|
<b>uint32_t</b> variable. If there is no such value, 0 is returned. When 1 is
|
|
returned, the code unit value itself can be retrieved using
|
|
PCRE2_INFO_LASTCODEUNIT. 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 1 (with "z" returned from
|
|
PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/ the returned value is 0.
|
|
<pre>
|
|
PCRE2_INFO_LASTCODEUNIT
|
|
</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
|
|
third argument should point to an <b>uint32_t</b> variable. If there is no such
|
|
value, 0 is returned.
|
|
<pre>
|
|
PCRE2_INFO_MATCHEMPTY
|
|
</pre>
|
|
Return 1 if the pattern might match an empty string, otherwise 0. The third
|
|
argument should point to an <b>uint32_t</b> variable. When a pattern contains
|
|
recursive subroutine calls it is not always possible to determine whether or
|
|
not it can match an empty string. PCRE2 takes a cautious approach and returns 1
|
|
in such cases.
|
|
<pre>
|
|
PCRE2_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 third argument
|
|
should point to an unsigned 32-bit integer. If no such value has been set, the
|
|
call to <b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET.
|
|
<pre>
|
|
PCRE2_INFO_MAXLOOKBEHIND
|
|
</pre>
|
|
Return the number of characters (not code units) in the longest lookbehind
|
|
assertion in the pattern. The third argument should point to an unsigned 32-bit
|
|
integer. 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>
|
|
PCRE2_INFO_MINLENGTH
|
|
</pre>
|
|
If a minimum length for matching subject strings was computed, its value is
|
|
returned. Otherwise the returned value is 0. The value is a number of
|
|
characters, which in UTF mode may be different from the number of code units.
|
|
The third argument should point to an <b>uint32_t</b> variable. The 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>
|
|
PCRE2_INFO_NAMECOUNT
|
|
PCRE2_INFO_NAMEENTRYSIZE
|
|
PCRE2_INFO_NAMETABLE
|
|
</pre>
|
|
PCRE2 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>pcre2_substring_get_byname()</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>pcre2_match()</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. PCRE2_INFO_NAMECOUNT gives
|
|
the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives the size of each
|
|
entry in code units; both of these return a <b>uint32_t</b> value. The entry
|
|
size depends on the length of the longest name.
|
|
</P>
|
|
<P>
|
|
PCRE2_INFO_NAMETABLE returns a pointer to the first entry of the table. This is
|
|
a PCRE2_SPTR pointer to a block of code units. In the 8-bit library, 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
|
|
code units, the first of which contains the parenthesis number. In the 32-bit
|
|
library, the pointer points to 32-bit code 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="pcre2pattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
|
|
in the
|
|
<a href="pcre2pattern.html"><b>pcre2pattern</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.
|
|
</P>
|
|
<P>
|
|
Duplicate names for subpatterns with different numbers are permitted, but only
|
|
if PCRE2_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 PCRE2_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>
|
|
PCRE2_INFO_NEWLINE
|
|
</pre>
|
|
The output is a <b>uint32_t</b> with one of the following values:
|
|
<pre>
|
|
PCRE2_NEWLINE_CR Carriage return (CR)
|
|
PCRE2_NEWLINE_LF Linefeed (LF)
|
|
PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF)
|
|
PCRE2_NEWLINE_ANY Any Unicode line ending
|
|
PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF
|
|
</pre>
|
|
This specifies the default character sequence that will be recognized as
|
|
meaning "newline" while matching.
|
|
<pre>
|
|
PCRE2_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 third
|
|
argument should point to an unsigned 32-bit integer. If no such value has been
|
|
set, the call to <b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET.
|
|
<pre>
|
|
PCRE2_INFO_SIZE
|
|
</pre>
|
|
Return the size of the compiled pattern in bytes (for all three libraries). The
|
|
third argument should point to a <b>size_t</b> variable. This value includes the
|
|
size of the general data block that precedes the code units of the compiled
|
|
pattern itself. The value that is used when <b>pcre2_compile()</b> is getting
|
|
memory in which to place the compiled pattern may be slightly larger than the
|
|
value returned by this option, because there are cases where the code that
|
|
calculates the size has to over-estimate. Processing a pattern with the JIT
|
|
compiler does not alter the value returned by this option.
|
|
<a name="infoaboutcallouts"></a></P>
|
|
<br><a name="SEC23" href="#TOC1">INFORMATION ABOUT A PATTERN'S CALLOUTS</a><br>
|
|
<P>
|
|
<b>int pcre2_callout_enumerate(const pcre2_code *<i>code</i>,</b>
|
|
<b> int (*<i>callback</i>)(pcre2_callout_enumerate_block *, void *),</b>
|
|
<b> void *<i>user_data</i>);</b>
|
|
<br>
|
|
<br>
|
|
A script language that supports the use of string arguments in callouts might
|
|
like to scan all the callouts in a pattern before running the match. This can
|
|
be done by calling <b>pcre2_callout_enumerate()</b>. The first argument is a
|
|
pointer to a compiled pattern, the second points to a callback function, and
|
|
the third is arbitrary user data. The callback function is called for every
|
|
callout in the pattern in the order in which they appear. Its first argument is
|
|
a pointer to a callout enumeration block, and its second argument is the
|
|
<i>user_data</i> value that was passed to <b>pcre2_callout_enumerate()</b>. The
|
|
contents of the callout enumeration block are described in the
|
|
<a href="pcre2callout.html"><b>pcre2callout</b></a>
|
|
documentation, which also gives further details about callouts.
|
|
</P>
|
|
<br><a name="SEC24" href="#TOC1">SERIALIZATION AND PRECOMPILING</a><br>
|
|
<P>
|
|
It is possible to save compiled patterns on disc or elsewhere, and reload them
|
|
later, subject to a number of restrictions. The functions whose names begin
|
|
with <b>pcre2_serialize_</b> are used for this purpose. They are described in
|
|
the
|
|
<a href="pcre2serialize.html"><b>pcre2serialize</b></a>
|
|
documentation.
|
|
<a name="matchdatablock"></a></P>
|
|
<br><a name="SEC25" href="#TOC1">THE MATCH DATA BLOCK</a><br>
|
|
<P>
|
|
<b>pcre2_match_data *pcre2_match_data_create(uint32_t <i>ovecsize</i>,</b>
|
|
<b> pcre2_general_context *<i>gcontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>pcre2_match_data *pcre2_match_data_create_from_pattern(</b>
|
|
<b> const pcre2_code *<i>code</i>, pcre2_general_context *<i>gcontext</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>void pcre2_match_data_free(pcre2_match_data *<i>match_data</i>);</b>
|
|
</P>
|
|
<P>
|
|
Information about a successful or unsuccessful match is placed in a match
|
|
data block, which is an opaque structure that is accessed by function calls. In
|
|
particular, the match data block contains a vector of offsets into the subject
|
|
string that define the matched part of the subject and any substrings that were
|
|
captured. This is known as the <i>ovector</i>.
|
|
</P>
|
|
<P>
|
|
Before calling <b>pcre2_match()</b>, <b>pcre2_dfa_match()</b>, or
|
|
<b>pcre2_jit_match()</b> you must create a match data block by calling one of
|
|
the creation functions above. For <b>pcre2_match_data_create()</b>, the first
|
|
argument is the number of pairs of offsets in the <i>ovector</i>. One pair of
|
|
offsets is required to identify the string that matched the whole pattern, with
|
|
another pair for each captured substring. For example, a value of 4 creates
|
|
enough space to record the matched portion of the subject plus three captured
|
|
substrings. A minimum of at least 1 pair is imposed by
|
|
<b>pcre2_match_data_create()</b>, so it is always possible to return the overall
|
|
matched string.
|
|
</P>
|
|
<P>
|
|
The second argument of <b>pcre2_match_data_create()</b> is a pointer to a
|
|
general context, which can specify custom memory management for obtaining the
|
|
memory for the match data block. If you are not using custom memory management,
|
|
pass NULL, which causes <b>malloc()</b> to be used.
|
|
</P>
|
|
<P>
|
|
For <b>pcre2_match_data_create_from_pattern()</b>, the first argument is a
|
|
pointer to a compiled pattern. The ovector is created to be exactly the right
|
|
size to hold all the substrings a pattern might capture. The second argument is
|
|
again a pointer to a general context, but in this case if NULL is passed, the
|
|
memory is obtained using the same allocator that was used for the compiled
|
|
pattern (custom or default).
|
|
</P>
|
|
<P>
|
|
A match data block can be used many times, with the same or different compiled
|
|
patterns. You can extract information from a match data block after a match
|
|
operation has finished, using functions that are described in the sections on
|
|
<a href="#matchedstrings">matched strings</a>
|
|
and
|
|
<a href="#matchotherdata">other match data</a>
|
|
below.
|
|
</P>
|
|
<P>
|
|
When a call of <b>pcre2_match()</b> fails, valid data is available in the match
|
|
block only when the error is PCRE2_ERROR_NOMATCH, PCRE2_ERROR_PARTIAL, or one
|
|
of the error codes for an invalid UTF string. Exactly what is available depends
|
|
on the error, and is detailed below.
|
|
</P>
|
|
<P>
|
|
When one of the matching functions is called, pointers to the compiled pattern
|
|
and the subject string are set in the match data block so that they can be
|
|
referenced by the extraction functions. After running a match, you must not
|
|
free a compiled pattern or a subject string until after all operations on the
|
|
match data block (for that match) have taken place.
|
|
</P>
|
|
<P>
|
|
When a match data block itself is no longer needed, it should be freed by
|
|
calling <b>pcre2_match_data_free()</b>.
|
|
</P>
|
|
<br><a name="SEC26" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br>
|
|
<P>
|
|
<b>int pcre2_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b>
|
|
<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b>
|
|
<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b>
|
|
<b> pcre2_match_context *<i>mcontext</i>);</b>
|
|
</P>
|
|
<P>
|
|
The function <b>pcre2_match()</b> is called to match a subject string against a
|
|
compiled pattern, which is passed in the <i>code</i> argument. You can call
|
|
<b>pcre2_match()</b> with the same <i>code</i> argument as many times as you
|
|
like, in order to find multiple matches in the subject string or 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>pcre2_dfa_match()</b> function.
|
|
</P>
|
|
<P>
|
|
Here is an example of a simple call to <b>pcre2_match()</b>:
|
|
<pre>
|
|
pcre2_match_data *md = pcre2_match_data_create(4, NULL);
|
|
int rc = pcre2_match(
|
|
re, /* result of pcre2_compile() */
|
|
"some string", /* the subject string */
|
|
11, /* the length of the subject string */
|
|
0, /* start at offset 0 in the subject */
|
|
0, /* default options */
|
|
match_data, /* the match data block */
|
|
NULL); /* a match context; NULL means use defaults */
|
|
</pre>
|
|
If the subject string is zero-terminated, the length can be given as
|
|
PCRE2_ZERO_TERMINATED. A match context must be provided if certain less common
|
|
matching parameters are to be changed. For details, see the section on
|
|
<a href="#matchcontext">the match context</a>
|
|
above.
|
|
</P>
|
|
<br><b>
|
|
The string to be matched by <b>pcre2_match()</b>
|
|
</b><br>
|
|
<P>
|
|
The subject string is passed to <b>pcre2_match()</b> as a pointer in
|
|
<i>subject</i>, a length in <i>length</i>, and a starting offset in
|
|
<i>startoffset</i>. The length and offset are in code units, not characters.
|
|
That is, they are in bytes for the 8-bit library, 16-bit code units for the
|
|
16-bit library, and 32-bit code units for the 32-bit library, whether or not
|
|
UTF processing is enabled.
|
|
</P>
|
|
<P>
|
|
If <i>startoffset</i> is greater than the length of the subject,
|
|
<b>pcre2_match()</b> returns PCRE2_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 starting offset
|
|
must point to the start of a character, or to the end of the subject (in UTF-32
|
|
mode, one code unit equals one character, so all offsets are valid). Like 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>pcre2_match()</b> again after a previous success.
|
|
Setting <i>startoffset</i> differs from passing over a shortened string and
|
|
setting PCRE2_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>pcre2_match()</b> finds the first
|
|
occurrence. If <b>pcre2_match()</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>pcre2_match()</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 PCRE2_NOTEMPTY_ATSTART and
|
|
PCRE2_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="pcre2demo.html"><b>pcre2demo</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.
|
|
<a name="matchoptions"></a></P>
|
|
<br><b>
|
|
Option bits for <b>pcre2_match()</b>
|
|
</b><br>
|
|
<P>
|
|
The unused bits of the <i>options</i> argument for <b>pcre2_match()</b> must be
|
|
zero. The only bits that may be set are PCRE2_ANCHORED, PCRE2_NOTBOL,
|
|
PCRE2_NOTEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_JIT,
|
|
PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, and PCRE2_PARTIAL_SOFT. Their action is
|
|
described below.
|
|
</P>
|
|
<P>
|
|
Setting PCRE2_ANCHORED at match time is not supported by the just-in-time (JIT)
|
|
compiler. If it is set, JIT matching is disabled and the normal interpretive
|
|
code in <b>pcre2_match()</b> is run. Apart from PCRE2_NO_JIT (obviously), the
|
|
remaining options are supported for JIT matching.
|
|
<pre>
|
|
PCRE2_ANCHORED
|
|
</pre>
|
|
The PCRE2_ANCHORED option limits <b>pcre2_match()</b> to matching at the first
|
|
matching position. If a pattern was compiled with PCRE2_ANCHORED, or turned out
|
|
to be anchored by virtue of its contents, it cannot be made unachored at
|
|
matching time. Note that setting the option at match time disables JIT
|
|
matching.
|
|
<pre>
|
|
PCRE2_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 having set PCRE2_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>
|
|
PCRE2_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 having set
|
|
PCRE2_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>
|
|
PCRE2_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 PCRE2_NOTEMPTY set, this match is not
|
|
valid, so <b>pcre2_match()</b> searches further into the string for occurrences
|
|
of "a" or "b".
|
|
<pre>
|
|
PCRE2_NOTEMPTY_ATSTART
|
|
</pre>
|
|
This is like PCRE2_NOTEMPTY, except that it locks out an empty string match
|
|
only at the first matching position, that is, at the start of the subject plus
|
|
the starting offset. An empty string match later in the subject is permitted.
|
|
If the pattern is anchored, such a match can occur only if the pattern contains
|
|
\K.
|
|
<pre>
|
|
PCRE2_NO_JIT
|
|
</pre>
|
|
By default, if a pattern has been successfully processed by
|
|
<b>pcre2_jit_compile()</b>, JIT is automatically used when <b>pcre2_match()</b>
|
|
is called with options that JIT supports. Setting PCRE2_NO_JIT disables the use
|
|
of JIT; it forces matching to be done by the interpreter.
|
|
<pre>
|
|
PCRE2_NO_UTF_CHECK
|
|
</pre>
|
|
When PCRE2_UTF is set at compile time, the validity of the subject as a UTF
|
|
string is checked by default when <b>pcre2_match()</b> is subsequently called.
|
|
If a non-zero starting offset is given, the check is applied only to that part
|
|
of the subject that could be inspected during matching, and there is a check
|
|
that the starting offset points to the first code unit of a character or to the
|
|
end of the subject. If there are no lookbehind assertions in the pattern, the
|
|
check starts at the starting offset. Otherwise, it starts at the length of the
|
|
longest lookbehind before the starting offset, or at the start of the subject
|
|
if there are not that many characters before the starting offset. Note that the
|
|
sequences \b and \B are one-character lookbehinds.
|
|
</P>
|
|
<P>
|
|
The check is carried out before any other processing takes place, and a
|
|
negative error code is returned if the check fails. There are several UTF error
|
|
codes for each code unit width, corresponding to different problems with the
|
|
code unit sequence. There are discussions about the validity of
|
|
<a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a>
|
|
<a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a>
|
|
and
|
|
<a href="pcre2unicode.html#utf32strings">UTF-32 strings</a>
|
|
in the
|
|
<a href="pcre2unicode.html"><b>pcre2unicode</b></a>
|
|
page.
|
|
</P>
|
|
<P>
|
|
If you know that your subject is valid, and you want to skip these checks for
|
|
performance reasons, you can set the PCRE2_NO_UTF_CHECK option when calling
|
|
<b>pcre2_match()</b>. You might want to do this for the second and subsequent
|
|
calls to <b>pcre2_match()</b> if you are making repeated calls to find all the
|
|
matches in a single subject string.
|
|
</P>
|
|
<P>
|
|
NOTE: When PCRE2_NO_UTF_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 indefinitely.
|
|
<pre>
|
|
PCRE2_PARTIAL_HARD
|
|
PCRE2_PARTIAL_SOFT
|
|
</pre>
|
|
These options turn on the partial matching feature. 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
|
|
PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD) is set, matching continues by
|
|
testing any remaining alternatives. Only if no complete match can be found is
|
|
PCRE2_ERROR_PARTIAL returned instead of PCRE2_ERROR_NOMATCH. In other words,
|
|
PCRE2_PARTIAL_SOFT specifies that the caller is prepared to handle a partial
|
|
match, but only if no complete match can be found.
|
|
</P>
|
|
<P>
|
|
If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this case, if
|
|
a partial match is found, <b>pcre2_match()</b> immediately returns
|
|
PCRE2_ERROR_PARTIAL, without considering any other alternatives. In other
|
|
words, when PCRE2_PARTIAL_HARD is set, a partial match is considered to be more
|
|
important that an alternative complete match.
|
|
</P>
|
|
<P>
|
|
There is a more detailed discussion of partial and multi-segment matching, with
|
|
examples, in the
|
|
<a href="pcre2partial.html"><b>pcre2partial</b></a>
|
|
documentation.
|
|
</P>
|
|
<br><a name="SEC27" href="#TOC1">NEWLINE HANDLING WHEN MATCHING</a><br>
|
|
<P>
|
|
When PCRE2 is built, a default newline convention is set; this is usually the
|
|
standard convention for the operating system. The default can be overridden in
|
|
a
|
|
<a href="#compilecontext">compile context</a>
|
|
by calling <b>pcre2_set_newline()</b>. It can also be overridden by starting a
|
|
pattern string with, for example, (*CRLF), as described in the
|
|
<a href="pcre2pattern.html#newlines">section on newline conventions</a>
|
|
in the
|
|
<a href="pcre2pattern.html"><b>pcre2pattern</b></a>
|
|
page. During matching, the newline choice affects the behaviour of the dot,
|
|
circumflex, and dollar metacharacters. It may also alter the way the match
|
|
starting position is advanced after a match failure for an unanchored pattern.
|
|
</P>
|
|
<P>
|
|
When PCRE2_NEWLINE_CRLF, PCRE2_NEWLINE_ANYCRLF, or PCRE2_NEWLINE_ANY is set as
|
|
the newline convention, and a match attempt for an unanchored pattern fails
|
|
when the current starting 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 PCRE2_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 in the pattern, or one of the \r or \n escape sequences. Implicit
|
|
matches such as [^X] do not count, nor does \s, even though it 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.
|
|
<a name="matchedstrings"></a></P>
|
|
<br><a name="SEC28" href="#TOC1">HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS</a><br>
|
|
<P>
|
|
<b>uint32_t pcre2_get_ovector_count(pcre2_match_data *<i>match_data</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *<i>match_data</i>);</b>
|
|
</P>
|
|
<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
|
|
parenthesized parts of the pattern. Following the usage in Jeffrey Friedl's
|
|
book, this is called "capturing" in what follows, and the phrase "capturing
|
|
subpattern" or "capturing group" is used for a fragment of a pattern that picks
|
|
out a substring. PCRE2 supports several other kinds of parenthesized subpattern
|
|
that do not cause substrings to be captured. The <b>pcre2_pattern_info()</b>
|
|
function can be used to find out how many capturing subpatterns there are in a
|
|
compiled pattern.
|
|
</P>
|
|
<P>
|
|
You can use auxiliary functions for accessing captured substrings
|
|
<a href="#extractbynumber">by number</a>
|
|
or
|
|
<a href="#extractbyname">by name,</a>
|
|
as described in sections below.
|
|
</P>
|
|
<P>
|
|
Alternatively, you can make direct use of the vector of PCRE2_SIZE values,
|
|
called the <b>ovector</b>, which contains the offsets of captured strings. It is
|
|
part of the
|
|
<a href="#matchdatablock">match data block.</a>
|
|
The function <b>pcre2_get_ovector_pointer()</b> returns the address of the
|
|
ovector, and <b>pcre2_get_ovector_count()</b> returns the number of pairs of
|
|
values it contains.
|
|
</P>
|
|
<P>
|
|
Within the ovector, the first in each pair of values is set to the offset of
|
|
the first code unit of a substring, and the second is set to the offset of the
|
|
first code unit after the end of a substring. These values are always code unit
|
|
offsets, not character offsets. That is, they are byte offsets in the 8-bit
|
|
library, 16-bit offsets in the 16-bit library, and 32-bit offsets in the 32-bit
|
|
library.
|
|
</P>
|
|
<P>
|
|
After a partial match (error return PCRE2_ERROR_PARTIAL), only the first pair
|
|
of offsets (that is, <i>ovector[0]</i> and <i>ovector[1]</i>) are set. They
|
|
identify the part of the subject that was partially matched. See the
|
|
<a href="pcre2partial.html"><b>pcre2partial</b></a>
|
|
documentation for details of partial matching.
|
|
</P>
|
|
<P>
|
|
After a successful match, the first pair of offsets identifies the portion of
|
|
the subject string that was matched by the entire pattern. The next pair is
|
|
used for the first capturing subpattern, and so on. The value returned by
|
|
<b>pcre2_match()</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 pattern uses the \K escape sequence within a positive assertion, the
|
|
reported start of a successful match can be greater than the end of the match.
|
|
For example, if the pattern (?=ab\K) is matched against "ab", the start and
|
|
end offset values for the match are 2 and 0.
|
|
</P>
|
|
<P>
|
|
If a capturing subpattern group is matched repeatedly within a single match
|
|
operation, it is the last portion of the subject that it matched that is
|
|
returned.
|
|
</P>
|
|
<P>
|
|
If the ovector is too small to hold all the captured substring offsets, as much
|
|
as possible is filled in, and the function returns a value of zero. If captured
|
|
substrings are not of interest, <b>pcre2_match()</b> may be called with a match
|
|
data block whose ovector is of minimum length (that is, one pair). However, if
|
|
the pattern contains back references and the <i>ovector</i> is not big enough to
|
|
remember the related substrings, PCRE2 has to get additional memory for use
|
|
during matching. Thus it is usually advisable to set up a match data block
|
|
containing an ovector of reasonable size.
|
|
</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 PCRE2_UNSET.
|
|
</P>
|
|
<P>
|
|
Offset values that correspond to unused subpatterns at the end of the
|
|
expression are also set to PCRE2_UNSET. 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. The offsets for for the second and third capturing
|
|
subpatterns (assuming the vector is large enough, of course) are set to
|
|
PCRE2_UNSET.
|
|
</P>
|
|
<P>
|
|
Elements in the ovector 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>pcre2_match()</b>. The other elements retain whatever values they previously
|
|
had.
|
|
<a name="matchotherdata"></a></P>
|
|
<br><a name="SEC29" href="#TOC1">OTHER INFORMATION ABOUT A MATCH</a><br>
|
|
<P>
|
|
<b>PCRE2_SPTR pcre2_get_mark(pcre2_match_data *<i>match_data</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *<i>match_data</i>);</b>
|
|
</P>
|
|
<P>
|
|
As well as the offsets in the ovector, other information about a match is
|
|
retained in the match data block and can be retrieved by the above functions in
|
|
appropriate circumstances. If they are called at other times, the result is
|
|
undefined.
|
|
</P>
|
|
<P>
|
|
After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a failure
|
|
to match (PCRE2_ERROR_NOMATCH), a (*MARK) name may be available, and
|
|
<b>pcre2_get_mark()</b> can be called. It returns a pointer to the
|
|
zero-terminated name, which is within the compiled pattern. Otherwise NULL is
|
|
returned. The length of the (*MARK) name (excluding the terminating zero) is
|
|
stored in the code unit that preceeds the name. You should use this instead of
|
|
relying on the terminating zero if the (*MARK) name might contain a binary
|
|
zero.
|
|
</P>
|
|
<P>
|
|
After a successful match, the (*MARK) name that is returned is the
|
|
last one encountered on the matching path through the pattern. After a "no
|
|
match" or a partial match, the last encountered (*MARK) name is returned. For
|
|
example, consider this pattern:
|
|
<pre>
|
|
^(*MARK:A)((*MARK:B)a|b)c
|
|
</pre>
|
|
When it matches "bc", the returned mark is A. The B mark is "seen" in the first
|
|
branch of the group, but it is not on the matching path. On the other hand,
|
|
when this pattern fails to match "bx", the returned mark is B.
|
|
</P>
|
|
<P>
|
|
After a successful match, a partial match, or one of the invalid UTF errors
|
|
(for example, PCRE2_ERROR_UTF8_ERR5), <b>pcre2_get_startchar()</b> can be
|
|
called. After a successful or partial match it returns the code unit offset of
|
|
the character at which the match started. For a non-partial match, this can be
|
|
different to the value of <i>ovector[0]</i> if the pattern contains the \K
|
|
escape sequence. After a partial match, however, this value is always the same
|
|
as <i>ovector[0]</i> because \K does not affect the result of a partial match.
|
|
</P>
|
|
<P>
|
|
After a UTF check failure, <b>pcre2_get_startchar()</b> can be used to obtain
|
|
the code unit offset of the invalid UTF character. Details are given in the
|
|
<a href="pcre2unicode.html"><b>pcre2unicode</b></a>
|
|
page.
|
|
<a name="errorlist"></a></P>
|
|
<br><a name="SEC30" href="#TOC1">ERROR RETURNS FROM <b>pcre2_match()</b></a><br>
|
|
<P>
|
|
If <b>pcre2_match()</b> fails, it returns a negative number. This can be
|
|
converted to a text string by calling the <b>pcre2_get_error_message()</b>
|
|
function (see "Obtaining a textual error message"
|
|
<a href="#geterrormessage">below).</a>
|
|
Negative error codes are also returned by other functions, and are documented
|
|
with them. The codes are given names in the header file. If UTF checking is in
|
|
force and an invalid UTF subject string is detected, one of a number of
|
|
UTF-specific negative error codes is returned. Details are given in the
|
|
<a href="pcre2unicode.html"><b>pcre2unicode</b></a>
|
|
page. The following are the other errors that may be returned by
|
|
<b>pcre2_match()</b>:
|
|
<pre>
|
|
PCRE2_ERROR_NOMATCH
|
|
</pre>
|
|
The subject string did not match the pattern.
|
|
<pre>
|
|
PCRE2_ERROR_PARTIAL
|
|
</pre>
|
|
The subject string did not match, but it did match partially. See the
|
|
<a href="pcre2partial.html"><b>pcre2partial</b></a>
|
|
documentation for details of partial matching.
|
|
<pre>
|
|
PCRE2_ERROR_BADMAGIC
|
|
</pre>
|
|
PCRE2 stores a 4-byte "magic number" at the start of the compiled code, to
|
|
catch the case when it is passed a junk pointer. This is the error that is
|
|
returned when the magic number is not present.
|
|
<pre>
|
|
PCRE2_ERROR_BADMODE
|
|
</pre>
|
|
This error is given when 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>
|
|
PCRE2_ERROR_BADOFFSET
|
|
</pre>
|
|
The value of <i>startoffset</i> was greater than the length of the subject.
|
|
<pre>
|
|
PCRE2_ERROR_BADOPTION
|
|
</pre>
|
|
An unrecognized bit was set in the <i>options</i> argument.
|
|
<pre>
|
|
PCRE2_ERROR_BADUTFOFFSET
|
|
</pre>
|
|
The UTF code unit sequence that was passed as a subject was checked and found
|
|
to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the value of
|
|
<i>startoffset</i> did not point to the beginning of a UTF character or the end
|
|
of the subject.
|
|
<pre>
|
|
PCRE2_ERROR_CALLOUT
|
|
</pre>
|
|
This error is never generated by <b>pcre2_match()</b> itself. It is provided for
|
|
use by callout functions that want to cause <b>pcre2_match()</b> or
|
|
<b>pcre2_callout_enumerate()</b> to return a distinctive error code. See the
|
|
<a href="pcre2callout.html"><b>pcre2callout</b></a>
|
|
documentation for details.
|
|
<pre>
|
|
PCRE2_ERROR_INTERNAL
|
|
</pre>
|
|
An unexpected internal error has occurred. This error could be caused by a bug
|
|
in PCRE2 or by overwriting of the compiled pattern.
|
|
<pre>
|
|
PCRE2_ERROR_JIT_BADOPTION
|
|
</pre>
|
|
This error is returned when a pattern that was successfully studied using JIT
|
|
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="pcre2jit.html"><b>pcre2jit</b></a>
|
|
documentation for more details.
|
|
<pre>
|
|
PCRE2_ERROR_JIT_STACKLIMIT
|
|
</pre>
|
|
This error is returned when a pattern that was successfully studied using JIT
|
|
is being matched, but the memory available for the just-in-time processing
|
|
stack is not large enough. See the
|
|
<a href="pcre2jit.html"><b>pcre2jit</b></a>
|
|
documentation for more details.
|
|
<pre>
|
|
PCRE2_ERROR_MATCHLIMIT
|
|
</pre>
|
|
The backtracking limit was reached.
|
|
<pre>
|
|
PCRE2_ERROR_NOMEMORY
|
|
</pre>
|
|
If a pattern contains back references, but the ovector is not big enough to
|
|
remember the referenced substrings, PCRE2 gets a block of memory at the start
|
|
of matching to use for this purpose. There are some other special cases where
|
|
extra memory is needed during matching. This error is given when memory cannot
|
|
be obtained.
|
|
<pre>
|
|
PCRE2_ERROR_NULL
|
|
</pre>
|
|
Either the <i>code</i>, <i>subject</i>, or <i>match_data</i> argument was passed
|
|
as NULL.
|
|
<pre>
|
|
PCRE2_ERROR_RECURSELOOP
|
|
</pre>
|
|
This error is returned when <b>pcre2_match()</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 matching
|
|
is attempted.
|
|
<pre>
|
|
PCRE2_ERROR_RECURSIONLIMIT
|
|
</pre>
|
|
The internal recursion limit was reached.
|
|
<a name="geterrormessage"></a></P>
|
|
<br><a name="SEC31" href="#TOC1">OBTAINING A TEXTUAL ERROR MESSAGE</a><br>
|
|
<P>
|
|
<b>int pcre2_get_error_message(int <i>errorcode</i>, PCRE2_UCHAR *<i>buffer</i>,</b>
|
|
<b> PCRE2_SIZE <i>bufflen</i>);</b>
|
|
</P>
|
|
<P>
|
|
A text message for an error code from any PCRE2 function (compile, match, or
|
|
auxiliary) can be obtained by calling <b>pcre2_get_error_message()</b>. The code
|
|
is passed as the first argument, with the remaining two arguments specifying a
|
|
code unit buffer and its length, into which the text message is placed. Note
|
|
that the message is returned in code units of the appropriate width for the
|
|
library that is being used.
|
|
</P>
|
|
<P>
|
|
The returned message is terminated with a trailing zero, and the function
|
|
returns the number of code units used, excluding the trailing zero. If the
|
|
error number is unknown, the negative error code PCRE2_ERROR_BADDATA is
|
|
returned. If the buffer is too small, the message is truncated (but still with
|
|
a trailing zero), and the negative error code PCRE2_ERROR_NOMEMORY is returned.
|
|
None of the messages are very long; a buffer size of 120 code units is ample.
|
|
<a name="extractbynumber"></a></P>
|
|
<br><a name="SEC32" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br>
|
|
<P>
|
|
<b>int pcre2_substring_length_bynumber(pcre2_match_data *<i>match_data</i>,</b>
|
|
<b> uint32_t <i>number</i>, PCRE2_SIZE *<i>length</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>int pcre2_substring_copy_bynumber(pcre2_match_data *<i>match_data</i>,</b>
|
|
<b> uint32_t <i>number</i>, PCRE2_UCHAR *<i>buffer</i>,</b>
|
|
<b> PCRE2_SIZE *<i>bufflen</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>int pcre2_substring_get_bynumber(pcre2_match_data *<i>match_data</i>,</b>
|
|
<b> uint32_t <i>number</i>, PCRE2_UCHAR **<i>bufferptr</i>,</b>
|
|
<b> PCRE2_SIZE *<i>bufflen</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b>
|
|
</P>
|
|
<P>
|
|
Captured substrings can be accessed directly by using the ovector as described
|
|
<a href="#matchedstrings">above.</a>
|
|
For convenience, auxiliary functions are provided for extracting captured
|
|
substrings as new, separate, zero-terminated strings. 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.
|
|
</P>
|
|
<P>
|
|
The functions in this section identify substrings by number. The number zero
|
|
refers to the entire matched substring, with higher numbers referring to
|
|
substrings captured by parenthesized groups. After a partial match, only
|
|
substring zero is available. An attempt to extract any other substring gives
|
|
the error PCRE2_ERROR_PARTIAL. The next section describes similar functions for
|
|
extracting captured substrings by name.
|
|
</P>
|
|
<P>
|
|
If a pattern uses the \K escape sequence within a positive assertion, the
|
|
reported start of a successful match can be greater than the end of the match.
|
|
For example, if the pattern (?=ab\K) is matched against "ab", the start and
|
|
end offset values for the match are 2 and 0. In this situation, calling these
|
|
functions with a zero substring number extracts a zero-length empty string.
|
|
</P>
|
|
<P>
|
|
You can find the length in code units of a captured substring without
|
|
extracting it by calling <b>pcre2_substring_length_bynumber()</b>. The first
|
|
argument is a pointer to the match data block, the second is the group number,
|
|
and the third is a pointer to a variable into which the length is placed. If
|
|
you just want to know whether or not the substring has been captured, you can
|
|
pass the third argument as NULL.
|
|
</P>
|
|
<P>
|
|
The <b>pcre2_substring_copy_bynumber()</b> function copies a captured substring
|
|
into a supplied buffer, whereas <b>pcre2_substring_get_bynumber()</b> copies it
|
|
into new memory, obtained using the same memory allocation function that was
|
|
used for the match data block. The first two arguments of these functions are a
|
|
pointer to the match data block and a capturing group number.
|
|
</P>
|
|
<P>
|
|
The final arguments of <b>pcre2_substring_copy_bynumber()</b> are a pointer to
|
|
the buffer and a pointer to a variable that contains its length in code units.
|
|
This is updated to contain the actual number of code units used for the
|
|
extracted substring, excluding the terminating zero.
|
|
</P>
|
|
<P>
|
|
For <b>pcre2_substring_get_bynumber()</b> the third and fourth arguments point
|
|
to variables that are updated with a pointer to the new memory and the number
|
|
of code units that comprise the substring, again excluding the terminating
|
|
zero. When the substring is no longer needed, the memory should be freed by
|
|
calling <b>pcre2_substring_free()</b>.
|
|
</P>
|
|
<P>
|
|
The return value from all these functions is zero for success, or a negative
|
|
error code. If the pattern match failed, the match failure code is returned.
|
|
If a substring number greater than zero is used after a partial match,
|
|
PCRE2_ERROR_PARTIAL is returned. Other possible error codes are:
|
|
<pre>
|
|
PCRE2_ERROR_NOMEMORY
|
|
</pre>
|
|
The buffer was too small for <b>pcre2_substring_copy_bynumber()</b>, or the
|
|
attempt to get memory failed for <b>pcre2_substring_get_bynumber()</b>.
|
|
<pre>
|
|
PCRE2_ERROR_NOSUBSTRING
|
|
</pre>
|
|
There is no substring with that number in the pattern, that is, the number is
|
|
greater than the number of capturing parentheses.
|
|
<pre>
|
|
PCRE2_ERROR_UNAVAILABLE
|
|
</pre>
|
|
The substring number, though not greater than the number of captures in the
|
|
pattern, is greater than the number of slots in the ovector, so the substring
|
|
could not be captured.
|
|
<pre>
|
|
PCRE2_ERROR_UNSET
|
|
</pre>
|
|
The substring did not participate in the match. For example, if the pattern is
|
|
(abc)|(def) and the subject is "def", and the ovector contains at least two
|
|
capturing slots, substring number 1 is unset.
|
|
</P>
|
|
<br><a name="SEC33" href="#TOC1">EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS</a><br>
|
|
<P>
|
|
<b>int pcre2_substring_list_get(pcre2_match_data *<i>match_data</i>,</b>
|
|
<b>" PCRE2_UCHAR ***<i>listptr</i>, PCRE2_SIZE **<i>lengthsptr</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>void pcre2_substring_list_free(PCRE2_SPTR *<i>list</i>);</b>
|
|
</P>
|
|
<P>
|
|
The <b>pcre2_substring_list_get()</b> function extracts all available substrings
|
|
and builds a list of pointers to them. It also (optionally) builds a second
|
|
list that contains their lengths (in code units), excluding a terminating zero
|
|
that is added to each of them. All this is done in a single block of memory
|
|
that is obtained using the same memory allocation function that was used to get
|
|
the match data block.
|
|
</P>
|
|
<P>
|
|
This function must be called only after a successful match. If called after a
|
|
partial match, the error code PCRE2_ERROR_PARTIAL is returned.
|
|
</P>
|
|
<P>
|
|
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 address of the list of lengths is returned via
|
|
<i>lengthsptr</i>. If your strings do not contain binary zeros and you do not
|
|
therefore need the lengths, you may supply NULL as the <b>lengthsptr</b>
|
|
argument to disable the creation of a list of lengths. The yield of the
|
|
function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the memory block
|
|
could not be obtained. When the list is no longer needed, it should be freed by
|
|
calling <b>pcre2_substring_list_free()</b>.
|
|
</P>
|
|
<P>
|
|
If this function encounters 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, it returns an empty string. This
|
|
can be distinguished from a genuine zero-length substring by inspecting the
|
|
appropriate offset in the ovector, which contain PCRE2_UNSET for unset
|
|
substrings, or by calling <b>pcre2_substring_length_bynumber()</b>.
|
|
<a name="extractbyname"></a></P>
|
|
<br><a name="SEC34" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br>
|
|
<P>
|
|
<b>int pcre2_substring_number_from_name(const pcre2_code *<i>code</i>,</b>
|
|
<b> PCRE2_SPTR <i>name</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>int pcre2_substring_length_byname(pcre2_match_data *<i>match_data</i>,</b>
|
|
<b> PCRE2_SPTR <i>name</i>, PCRE2_SIZE *<i>length</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>int pcre2_substring_copy_byname(pcre2_match_data *<i>match_data</i>,</b>
|
|
<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR *<i>buffer</i>, PCRE2_SIZE *<i>bufflen</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>int pcre2_substring_get_byname(pcre2_match_data *<i>match_data</i>,</b>
|
|
<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR **<i>bufferptr</i>, PCRE2_SIZE *<i>bufflen</i>);</b>
|
|
<br>
|
|
<br>
|
|
<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</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 (PCRE2_DUPNAMES was not set), you can find the number from the name by
|
|
calling <b>pcre2_substring_number_from_name()</b>. The first argument is the
|
|
compiled pattern, and the second is the name. The yield of the function is the
|
|
subpattern number, PCRE2_ERROR_NOSUBSTRING if there is no subpattern of that
|
|
name, or PCRE2_ERROR_NOUNIQUESUBSTRING if there is more than one subpattern of
|
|
that name. Given the number, you can extract the substring directly, or use one
|
|
of the functions described above.
|
|
</P>
|
|
<P>
|
|
For convenience, there are also "byname" functions that correspond to the
|
|
"bynumber" functions, the only difference being that the second argument is a
|
|
name instead of a number. If PCRE2_DUPNAMES is set and there are duplicate
|
|
names, these functions scan all the groups with the given name, and return the
|
|
first named string that is set.
|
|
</P>
|
|
<P>
|
|
If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is
|
|
returned. If all groups with the name have numbers that are greater than the
|
|
number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is returned. If there
|
|
is at least one group with a slot in the ovector, but no group is found to be
|
|
set, PCRE2_ERROR_UNSET is returned.
|
|
</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="pcre2pattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a>
|
|
in the
|
|
<a href="pcre2pattern.html"><b>pcre2pattern</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="SEC35" href="#TOC1">CREATING A NEW STRING WITH SUBSTITUTIONS</a><br>
|
|
<P>
|
|
<b>int pcre2_substitute(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b>
|
|
<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b>
|
|
<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b>
|
|
<b> pcre2_match_context *<i>mcontext</i>, PCRE2_SPTR <i>replacement</i>,</b>
|
|
<b> PCRE2_SIZE <i>rlength</i>, PCRE2_UCHAR *\fIoutputbuffer\zfP,</b>
|
|
<b> PCRE2_SIZE *<i>outlengthptr</i>);</b>
|
|
</P>
|
|
<P>
|
|
This function calls <b>pcre2_match()</b> and then makes a copy of the subject
|
|
string in <i>outputbuffer</i>, replacing the part that was matched with the
|
|
<i>replacement</i> string, whose length is supplied in <b>rlength</b>. This can
|
|
be given as PCRE2_ZERO_TERMINATED for a zero-terminated string. Matches in
|
|
which a \K item in a lookahead in the pattern causes the match to end before
|
|
it starts are not supported, and give rise to an error return.
|
|
</P>
|
|
<P>
|
|
The first seven arguments of <b>pcre2_substitute()</b> are the same as for
|
|
<b>pcre2_match()</b>, except that the partial matching options are not
|
|
permitted, and <i>match_data</i> may be passed as NULL, in which case a match
|
|
data block is obtained and freed within this function, using memory management
|
|
functions from the match context, if provided, or else those that were used to
|
|
allocate memory for the compiled code.
|
|
</P>
|
|
<P>
|
|
The <i>outlengthptr</i> argument must point to a variable that contains the
|
|
length, in code units, of the output buffer. If the function is successful, the
|
|
value is updated to contain the length of the new string, excluding the
|
|
trailing zero that is automatically added.
|
|
</P>
|
|
<P>
|
|
If the function is not successful, the value set via <i>outlengthptr</i> depends
|
|
on the type of error. For syntax errors in the replacement string, the value is
|
|
the offset in the replacement string where the error was detected. For other
|
|
errors, the value is PCRE2_UNSET by default. This includes the case of the
|
|
output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set
|
|
(see below), in which case the value is the minimum length needed, including
|
|
space for the trailing zero. Note that in order to compute the required length,
|
|
<b>pcre2_substitute()</b> has to simulate all the matching and copying, instead
|
|
of giving an error return as soon as the buffer overflows. Note also that the
|
|
length is in code units, not bytes.
|
|
</P>
|
|
<P>
|
|
In the replacement string, which is interpreted as a UTF string in UTF mode,
|
|
and is checked for UTF validity unless the PCRE2_NO_UTF_CHECK option is set, a
|
|
dollar character is an escape character that can specify the insertion of
|
|
characters from capturing groups or (*MARK) items in the pattern. The following
|
|
forms are always recognized:
|
|
<pre>
|
|
$$ insert a dollar character
|
|
$<n> or ${<n>} insert the contents of group <n>
|
|
$*MARK or ${*MARK} insert the name of the last (*MARK) encountered
|
|
</pre>
|
|
Either a group number or a group name can be given for <n>. Curly brackets are
|
|
required only if the following character would be interpreted as part of the
|
|
number or name. The number may be zero to include the entire matched string.
|
|
For example, if the pattern a(b)c is matched with "=abc=" and the replacement
|
|
string "+$1$0$1+", the result is "=+babcb+=".
|
|
</P>
|
|
<P>
|
|
The facility for inserting a (*MARK) name can be used to perform simple
|
|
simultaneous substitutions, as this <b>pcre2test</b> example shows:
|
|
<pre>
|
|
/(*:pear)apple|(*:orange)lemon/g,replace=${*MARK}
|
|
apple lemon
|
|
2: pear orange
|
|
</pre>
|
|
As well as the usual options for <b>pcre2_match()</b>, a number of additional
|
|
options can be set in the <i>options</i> argument.
|
|
</P>
|
|
<P>
|
|
PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject string,
|
|
replacing every matching substring. If this is not set, only the first matching
|
|
substring is replaced. If any matched substring has zero length, after the
|
|
substitution has happened, an attempt to find a non-empty match at the same
|
|
position is performed. If this is not successful, the current position is
|
|
advanced by one character except when CRLF is a valid newline sequence and the
|
|
next two characters are CR, LF. In this case, the current position is advanced
|
|
by two characters.
|
|
</P>
|
|
<P>
|
|
PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is
|
|
too small. The default action is to return PCRE2_ERROR_NOMEMORY immediately. If
|
|
this option is set, however, <b>pcre2_substitute()</b> continues to go through
|
|
the motions of matching and substituting (without, of course, writing anything)
|
|
in order to compute the size of buffer that is needed. This value is passed
|
|
back via the <i>outlengthptr</i> variable, with the result of the function still
|
|
being PCRE2_ERROR_NOMEMORY.
|
|
</P>
|
|
<P>
|
|
Passing a buffer size of zero is a permitted way of finding out how much memory
|
|
is needed for given substitution. However, this does mean that the entire
|
|
operation is carried out twice. Depending on the application, it may be more
|
|
efficient to allocate a large buffer and free the excess afterwards, instead of
|
|
using PCRE2_SUBSTITUTE_OVERFLOW_LENGTH.
|
|
</P>
|
|
<P>
|
|
PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capturing groups that do
|
|
not appear in the pattern to be treated as unset groups. This option should be
|
|
used with care, because it means that a typo in a group name or number no
|
|
longer causes the PCRE2_ERROR_NOSUBSTRING error.
|
|
</P>
|
|
<P>
|
|
PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capturing groups (including unknown
|
|
groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated as empty
|
|
strings when inserted as described above. If this option is not set, an attempt
|
|
to insert an unset group causes the PCRE2_ERROR_UNSET error. This option does
|
|
not influence the extended substitution syntax described below.
|
|
</P>
|
|
<P>
|
|
PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the
|
|
replacement string. Without this option, only the dollar character is special,
|
|
and only the group insertion forms listed above are valid. When
|
|
PCRE2_SUBSTITUTE_EXTENDED is set, two things change:
|
|
</P>
|
|
<P>
|
|
Firstly, backslash in a replacement string is interpreted as an escape
|
|
character. The usual forms such as \n or \x{ddd} can be used to specify
|
|
particular character codes, and backslash followed by any non-alphanumeric
|
|
character quotes that character. Extended quoting can be coded using \Q...\E,
|
|
exactly as in pattern strings.
|
|
</P>
|
|
<P>
|
|
There are also four escape sequences for forcing the case of inserted letters.
|
|
The insertion mechanism has three states: no case forcing, force upper case,
|
|
and force lower case. The escape sequences change the current state: \U and
|
|
\L change to upper or lower case forcing, respectively, and \E (when not
|
|
terminating a \Q quoted sequence) reverts to no case forcing. The sequences
|
|
\u and \l force the next character (if it is a letter) to upper or lower
|
|
case, respectively, and then the state automatically reverts to no case
|
|
forcing. Case forcing applies to all inserted characters, including those from
|
|
captured groups and letters within \Q...\E quoted sequences.
|
|
</P>
|
|
<P>
|
|
Note that case forcing sequences such as \U...\E do not nest. For example,
|
|
the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final \E has no
|
|
effect.
|
|
</P>
|
|
<P>
|
|
The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more
|
|
flexibility to group substitution. The syntax is similar to that used by Bash:
|
|
<pre>
|
|
${<n>:-<string>}
|
|
${<n>:+<string1>:<string2>}
|
|
</pre>
|
|
As before, <n> may be a group number or a name. The first form specifies a
|
|
default value. If group <n> is set, its value is inserted; if not, <string> is
|
|
expanded and the result inserted. The second form specifies strings that are
|
|
expanded and inserted when group <n> is set or unset, respectively. The first
|
|
form is just a convenient shorthand for
|
|
<pre>
|
|
${<n>:+${<n>}:<string>}
|
|
</pre>
|
|
Backslash can be used to escape colons and closing curly brackets in the
|
|
replacement strings. A change of the case forcing state within a replacement
|
|
string remains in force afterwards, as shown in this <b>pcre2test</b> example:
|
|
<pre>
|
|
/(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo
|
|
body
|
|
1: hello
|
|
somebody
|
|
1: HELLO
|
|
</pre>
|
|
The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended
|
|
substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause unknown
|
|
groups in the extended syntax forms to be treated as unset.
|
|
</P>
|
|
<P>
|
|
If successful, <b>pcre2_substitute()</b> returns the number of replacements that
|
|
were made. This may be zero if no matches were found, and is never greater than
|
|
1 unless PCRE2_SUBSTITUTE_GLOBAL is set.
|
|
</P>
|
|
<P>
|
|
In the event of an error, a negative error code is returned. Except for
|
|
PCRE2_ERROR_NOMATCH (which is never returned), errors from <b>pcre2_match()</b>
|
|
are passed straight back.
|
|
</P>
|
|
<P>
|
|
PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring insertion,
|
|
unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set.
|
|
</P>
|
|
<P>
|
|
PCRE2_ERROR_UNSET is returned for an unset substring insertion (including an
|
|
unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) when the simple
|
|
(non-extended) syntax is used and PCRE2_SUBSTITUTE_UNSET_EMPTY is not set.
|
|
</P>
|
|
<P>
|
|
PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big enough. If the
|
|
PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size of buffer that is
|
|
needed is returned via <i>outlengthptr</i>. Note that this does not happen by
|
|
default.
|
|
</P>
|
|
<P>
|
|
PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in the
|
|
replacement string, with more particular errors being PCRE2_ERROR_BADREPESCAPE
|
|
(invalid escape sequence), PCRE2_ERROR_REPMISSING_BRACE (closing curly bracket
|
|
not found), PCRE2_BADSUBSTITUTION (syntax error in extended group
|
|
substitution), and PCRE2_BADSUBPATTERN (the pattern match ended before it
|
|
started, which can happen if \K is used in an assertion).
|
|
</P>
|
|
<P>
|
|
As for all PCRE2 errors, a text message that describes the error can be
|
|
obtained by calling the <b>pcre2_get_error_message()</b> function (see
|
|
"Obtaining a textual error message"
|
|
<a href="#geterrormessage">above).</a>
|
|
</P>
|
|
<br><a name="SEC36" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br>
|
|
<P>
|
|
<b>int pcre2_substring_nametable_scan(const pcre2_code *<i>code</i>,</b>
|
|
<b> PCRE2_SPTR <i>name</i>, PCRE2_SPTR *<i>first</i>, PCRE2_SPTR *<i>last</i>);</b>
|
|
</P>
|
|
<P>
|
|
When a pattern is compiled with the PCRE2_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="pcre2pattern.html"><b>pcre2pattern</b></a>
|
|
documentation.
|
|
</P>
|
|
<P>
|
|
When duplicates are present, <b>pcre2_substring_copy_byname()</b> and
|
|
<b>pcre2_substring_get_byname()</b> return the first substring corresponding to
|
|
the given name that is set. Only if none are set is PCRE2_ERROR_UNSET is
|
|
returned. The <b>pcre2_substring_number_from_name()</b> function returns the
|
|
error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate names.
|
|
</P>
|
|
<P>
|
|
If you want to get full details of all captured substrings for a given name,
|
|
you must use the <b>pcre2_substring_nametable_scan()</b> function. The first
|
|
argument is the compiled pattern, and the second is the name. If the third and
|
|
fourth arguments are NULL, the function returns a group number for a unique
|
|
name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise.
|
|
</P>
|
|
<P>
|
|
When the third and fourth arguments are not NULL, they must be pointers to
|
|
variables that 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, and the
|
|
function returns the length of each entry in code units. In both cases,
|
|
PCRE2_ERROR_NOSUBSTRING is returned if there are no entries for the given name.
|
|
</P>
|
|
<P>
|
|
The format of the name table is described
|
|
<a href="#infoaboutpattern">above</a>
|
|
in the section entitled <i>Information about a pattern</i>. Given all the
|
|
relevant entries for the name, you can extract each of their numbers, and hence
|
|
the captured data.
|
|
</P>
|
|
<br><a name="SEC37" href="#TOC1">FINDING ALL POSSIBLE MATCHES AT ONE POSITION</a><br>
|
|
<P>
|
|
The traditional matching function uses a similar algorithm to Perl, which stops
|
|
when it finds the first match at a given point in the subject. If you want to
|
|
find all possible matches, or the longest possible match at a given position,
|
|
consider using the alternative matching function (see below) instead. If you
|
|
cannot use the alternative function, you can kludge it up by making use of the
|
|
callout facility, which is described in the
|
|
<a href="pcre2callout.html"><b>pcre2callout</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>pcre2_match()</b> to backtrack and try
|
|
other alternatives. Ultimately, when it runs out of matches,
|
|
<b>pcre2_match()</b> will yield PCRE2_ERROR_NOMATCH.
|
|
<a name="dfamatch"></a></P>
|
|
<br><a name="SEC38" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br>
|
|
<P>
|
|
<b>int pcre2_dfa_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b>
|
|
<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b>
|
|
<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b>
|
|
<b> pcre2_match_context *<i>mcontext</i>,</b>
|
|
<b> int *<i>workspace</i>, PCRE2_SIZE <i>wscount</i>);</b>
|
|
</P>
|
|
<P>
|
|
The function <b>pcre2_dfa_match()</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
|
|
PCRE2 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>pcre2_dfa_match()</b> does not support, see the
|
|
<a href="pcre2matching.html"><b>pcre2matching</b></a>
|
|
documentation.
|
|
</P>
|
|
<P>
|
|
The arguments for the <b>pcre2_dfa_match()</b> function are the same as for
|
|
<b>pcre2_match()</b>, plus two extras. The ovector within the match data block
|
|
is used in a different way, and this is described below. The other common
|
|
arguments are used in the same way as for <b>pcre2_match()</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 is 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>pcre2_dfa_match()</b>:
|
|
<pre>
|
|
int wspace[20];
|
|
pcre2_match_data *md = pcre2_match_data_create(4, NULL);
|
|
int rc = pcre2_dfa_match(
|
|
re, /* result of pcre2_compile() */
|
|
"some string", /* the subject string */
|
|
11, /* the length of the subject string */
|
|
0, /* start at offset 0 in the subject */
|
|
0, /* default options */
|
|
match_data, /* the match data block */
|
|
NULL, /* a match context; NULL means use defaults */
|
|
wspace, /* working space vector */
|
|
20); /* number of elements (NOT size in bytes) */
|
|
</PRE>
|
|
</P>
|
|
<br><b>
|
|
Option bits for <b>pcre_dfa_match()</b>
|
|
</b><br>
|
|
<P>
|
|
The unused bits of the <i>options</i> argument for <b>pcre2_dfa_match()</b> must
|
|
be zero. The only bits that may be set are PCRE2_ANCHORED, PCRE2_NOTBOL,
|
|
PCRE2_NOTEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_UTF_CHECK,
|
|
PCRE2_PARTIAL_HARD, PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and
|
|
PCRE2_DFA_RESTART. All but the last four of these are exactly the same as for
|
|
<b>pcre2_match()</b>, so their description is not repeated here.
|
|
<pre>
|
|
PCRE2_PARTIAL_HARD
|
|
PCRE2_PARTIAL_SOFT
|
|
</pre>
|
|
These have the same general effect as they do for <b>pcre2_match()</b>, but the
|
|
details are slightly different. When PCRE2_PARTIAL_HARD is set for
|
|
<b>pcre2_dfa_match()</b>, it returns PCRE2_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
|
|
already been found. When PCRE2_PARTIAL_SOFT is set, the return code
|
|
PCRE2_ERROR_NOMATCH is converted into PCRE2_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="pcre2partial.html"><b>pcre2partial</b></a>
|
|
documentation.
|
|
<pre>
|
|
PCRE2_DFA_SHORTEST
|
|
</pre>
|
|
Setting the PCRE2_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>
|
|
PCRE2_DFA_RESTART
|
|
</pre>
|
|
When <b>pcre2_dfa_match()</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 PCRE2_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="pcre2partial.html"><b>pcre2partial</b></a>
|
|
documentation.
|
|
</P>
|
|
<br><b>
|
|
Successful returns from <b>pcre2_dfa_match()</b>
|
|
</b><br>
|
|
<P>
|
|
When <b>pcre2_dfa_match()</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 else> <something further>
|
|
<something> <something else>
|
|
<something>
|
|
</pre>
|
|
On success, the yield of the function is a number greater than zero, which is
|
|
the number of matched substrings. The offsets of the substrings are returned in
|
|
the ovector, and can be extracted by number in the same way as for
|
|
<b>pcre2_match()</b>, but the numbers bear no relation to any capturing groups
|
|
that may exist in the pattern, because DFA matching does not support group
|
|
capture.
|
|
</P>
|
|
<P>
|
|
Calls to the convenience functions that extract substrings by name
|
|
return the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used after a
|
|
DFA match. The convenience functions that extract substrings by number never
|
|
return PCRE2_ERROR_NOSUBSTRING, and the meanings of some other errors are
|
|
slightly different:
|
|
<pre>
|
|
PCRE2_ERROR_UNAVAILABLE
|
|
</pre>
|
|
The ovector is not big enough to include a slot for the given substring number.
|
|
<pre>
|
|
PCRE2_ERROR_UNSET
|
|
</pre>
|
|
There is a slot in the ovector for this substring, but there were insufficient
|
|
matches to fill it.
|
|
</P>
|
|
<P>
|
|
The matched strings are stored in the ovector in reverse order of length; that
|
|
is, the longest matching string is first. If there were too many matches to fit
|
|
into the ovector, the yield of the function is zero, and the vector is filled
|
|
with the longest matches.
|
|
</P>
|
|
<P>
|
|
NOTE: PCRE2'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++". 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 auch as "a\d+?" or set
|
|
the PCRE2_NO_AUTO_POSSESS option when compiling.
|
|
</P>
|
|
<br><b>
|
|
Error returns from <b>pcre2_dfa_match()</b>
|
|
</b><br>
|
|
<P>
|
|
The <b>pcre2_dfa_match()</b> function returns a negative number when it fails.
|
|
Many of the errors are the same as for <b>pcre2_match()</b>, as described
|
|
<a href="#errorlist">above.</a>
|
|
There are in addition the following errors that are specific to
|
|
<b>pcre2_dfa_match()</b>:
|
|
<pre>
|
|
PCRE2_ERROR_DFA_UITEM
|
|
</pre>
|
|
This return is given if <b>pcre2_dfa_match()</b> encounters an item in the
|
|
pattern that it does not support, for instance, the use of \C in a UTF mode or
|
|
a back reference.
|
|
<pre>
|
|
PCRE2_ERROR_DFA_UCOND
|
|
</pre>
|
|
This return is given if <b>pcre2_dfa_match()</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>
|
|
PCRE2_ERROR_DFA_WSSIZE
|
|
</pre>
|
|
This return is given if <b>pcre2_dfa_match()</b> runs out of space in the
|
|
<i>workspace</i> vector.
|
|
<pre>
|
|
PCRE2_ERROR_DFA_RECURSE
|
|
</pre>
|
|
When a recursive subpattern is processed, the matching function calls itself
|
|
recursively, using private memory for the ovector and <i>workspace</i>. This
|
|
error is given if the internal ovector is not large enough. This should be
|
|
extremely rare, as a vector of size 1000 is used.
|
|
<pre>
|
|
PCRE2_ERROR_DFA_BADRESTART
|
|
</pre>
|
|
When <b>pcre2_dfa_match()</b> is called with the <b>PCRE2_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="SEC39" href="#TOC1">SEE ALSO</a><br>
|
|
<P>
|
|
<b>pcre2build</b>(3), <b>pcre2callout</b>(3), <b>pcre2demo(3)</b>,
|
|
<b>pcre2matching</b>(3), <b>pcre2partial</b>(3), <b>pcre2posix</b>(3),
|
|
<b>pcre2sample</b>(3), <b>pcre2stack</b>(3), <b>pcre2unicode</b>(3).
|
|
</P>
|
|
<br><a name="SEC40" href="#TOC1">AUTHOR</a><br>
|
|
<P>
|
|
Philip Hazel
|
|
<br>
|
|
University Computing Service
|
|
<br>
|
|
Cambridge, England.
|
|
<br>
|
|
</P>
|
|
<br><a name="SEC41" href="#TOC1">REVISION</a><br>
|
|
<P>
|
|
Last updated: 23 December 2016
|
|
<br>
|
|
Copyright © 1997-2016 University of Cambridge.
|
|
<br>
|
|
<p>
|
|
Return to the <a href="index.html">PCRE2 index page</a>.
|
|
</p>
|