Updated PCRE source to version 8.32 (bug 5593).
This commit is contained in:
Nicholas Hastings
@@ -13,23 +13,35 @@ from the original man page. If there is any nonsense in it, please consult the
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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">PCRE CALLOUTS</a>
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<li><a name="TOC2" href="#SEC2">MISSING CALLOUTS</a>
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<li><a name="TOC3" href="#SEC3">THE CALLOUT INTERFACE</a>
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<li><a name="TOC4" href="#SEC4">RETURN VALUES</a>
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<li><a name="TOC5" href="#SEC5">AUTHOR</a>
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<li><a name="TOC6" href="#SEC6">REVISION</a>
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<li><a name="TOC1" href="#SEC1">SYNOPSIS</a>
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<li><a name="TOC2" href="#SEC2">DESCRIPTION</a>
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<li><a name="TOC3" href="#SEC3">MISSING CALLOUTS</a>
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<li><a name="TOC4" href="#SEC4">THE CALLOUT INTERFACE</a>
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<li><a name="TOC5" href="#SEC5">RETURN VALUES</a>
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<li><a name="TOC6" href="#SEC6">AUTHOR</a>
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<li><a name="TOC7" href="#SEC7">REVISION</a>
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</ul>
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<br><a name="SEC1" href="#TOC1">PCRE CALLOUTS</a><br>
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<br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br>
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<P>
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<b>#include <pcre.h></b>
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</P>
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<P>
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<b>int (*pcre_callout)(pcre_callout_block *);</b>
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</P>
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<P>
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<b>int (*pcre16_callout)(pcre16_callout_block *);</b>
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</P>
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<P>
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<b>int (*pcre32_callout)(pcre32_callout_block *);</b>
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</P>
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<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br>
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<P>
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PCRE provides a feature called "callout", which is a means of temporarily
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passing control to the caller of PCRE in the middle of pattern matching. The
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caller of PCRE provides an external function by putting its entry point in the
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global variable <i>pcre_callout</i>. By default, this variable contains NULL,
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which disables all calling out.
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global variable <i>pcre_callout</i> (<i>pcre16_callout</i> for the 16-bit
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library, <i>pcre32_callout</i> for the 32-bit library). By default, this
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variable contains NULL, which disables all calling out.
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</P>
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<P>
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Within a regular expression, (?C) indicates the points at which the external
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@@ -39,9 +51,9 @@ For example, this pattern has two callout points:
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<pre>
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(?C1)abc(?C2)def
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</pre>
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If the PCRE_AUTO_CALLOUT option bit is set when <b>pcre_compile()</b> is called,
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PCRE automatically inserts callouts, all with number 255, before each item in
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the pattern. For example, if PCRE_AUTO_CALLOUT is used with the pattern
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If the PCRE_AUTO_CALLOUT option bit is set when a pattern is compiled, PCRE
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automatically inserts callouts, all with number 255, before each item in the
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pattern. For example, if PCRE_AUTO_CALLOUT is used with the pattern
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<pre>
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A(\d{2}|--)
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</pre>
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@@ -59,7 +71,12 @@ command has an option that sets automatic callouts; when it is used, the output
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indicates how the pattern is matched. This is useful information when you are
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trying to optimize the performance of a particular pattern.
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</P>
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<br><a name="SEC2" href="#TOC1">MISSING CALLOUTS</a><br>
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<P>
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The use of callouts in a pattern makes it ineligible for optimization by the
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just-in-time compiler. Studying such a pattern with the PCRE_STUDY_JIT_COMPILE
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option always fails.
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</P>
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<br><a name="SEC3" href="#TOC1">MISSING CALLOUTS</a><br>
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<P>
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You should be aware that, because of optimizations in the way PCRE matches
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patterns by default, callouts sometimes do not happen. For example, if the
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@@ -73,34 +90,46 @@ the callout is never reached. However, with "abyd", though the result is still
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no match, the callout is obeyed.
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</P>
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<P>
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You can disable these optimizations by passing the PCRE_NO_START_OPTIMIZE
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option to <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. This slows down the
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matching process, but does ensure that callouts such as the example above are
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obeyed.
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If the pattern is studied, PCRE knows the minimum length of a matching string,
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and will immediately give a "no match" return without actually running a match
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if the subject is not long enough, or, for unanchored patterns, if it has
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been scanned far enough.
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</P>
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<br><a name="SEC3" href="#TOC1">THE CALLOUT INTERFACE</a><br>
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<P>
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You can disable these optimizations by passing the PCRE_NO_START_OPTIMIZE
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option to the matching function, or by starting the pattern with
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(*NO_START_OPT). This slows down the matching process, but does ensure that
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callouts such as the example above are obeyed.
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</P>
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<br><a name="SEC4" href="#TOC1">THE CALLOUT INTERFACE</a><br>
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<P>
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During matching, when PCRE reaches a callout point, the external function
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defined by <i>pcre_callout</i> is called (if it is set). This applies to both
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the <b>pcre_exec()</b> and the <b>pcre_dfa_exec()</b> matching functions. The
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only argument to the callout function is a pointer to a <b>pcre_callout</b>
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block. This structure contains the following fields:
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defined by <i>pcre_callout</i> or <i>pcre[16|32]_callout</i> is called
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(if it is set). This applies to both normal and DFA matching. The only
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argument to the callout function is a pointer to a <b>pcre_callout</b>
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or <b>pcre[16|32]_callout</b> block.
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These structures contains the following fields:
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<pre>
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int <i>version</i>;
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int <i>callout_number</i>;
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int *<i>offset_vector</i>;
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const char *<i>subject</i>;
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int <i>subject_length</i>;
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int <i>start_match</i>;
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int <i>current_position</i>;
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int <i>capture_top</i>;
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int <i>capture_last</i>;
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void *<i>callout_data</i>;
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int <i>pattern_position</i>;
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int <i>next_item_length</i>;
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int <i>version</i>;
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int <i>callout_number</i>;
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int *<i>offset_vector</i>;
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const char *<i>subject</i>; (8-bit version)
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PCRE_SPTR16 <i>subject</i>; (16-bit version)
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PCRE_SPTR32 <i>subject</i>; (32-bit version)
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int <i>subject_length</i>;
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int <i>start_match</i>;
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int <i>current_position</i>;
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int <i>capture_top</i>;
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int <i>capture_last</i>;
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void *<i>callout_data</i>;
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int <i>pattern_position</i>;
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int <i>next_item_length</i>;
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const unsigned char *<i>mark</i>; (8-bit version)
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const PCRE_UCHAR16 *<i>mark</i>; (16-bit version)
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const PCRE_UCHAR32 *<i>mark</i>; (32-bit version)
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</pre>
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The <i>version</i> field is an integer containing the version number of the
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block format. The initial version was 0; the current version is 1. The version
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block format. The initial version was 0; the current version is 2. The version
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number will change again in future if additional fields are added, but the
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intention is never to remove any of the existing fields.
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</P>
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@@ -111,15 +140,15 @@ automatically generated callouts).
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</P>
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<P>
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The <i>offset_vector</i> field is a pointer to the vector of offsets that was
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passed by the caller to <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. When
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<b>pcre_exec()</b> is used, the contents can be inspected in order to extract
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passed by the caller to the matching function. When <b>pcre_exec()</b> or
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<b>pcre[16|32]_exec()</b> is used, the contents can be inspected, in order to extract
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substrings that have been matched so far, in the same way as for extracting
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substrings after a match has completed. For <b>pcre_dfa_exec()</b> this field is
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not useful.
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substrings after a match has completed. For the DFA matching functions, this
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field is not useful.
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</P>
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<P>
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The <i>subject</i> and <i>subject_length</i> fields contain copies of the values
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that were passed to <b>pcre_exec()</b>.
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that were passed to the matching function.
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</P>
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<P>
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The <i>start_match</i> field normally contains the offset within the subject at
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@@ -134,53 +163,59 @@ The <i>current_position</i> field contains the offset within the subject of the
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current match pointer.
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</P>
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<P>
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When the <b>pcre_exec()</b> function is used, the <i>capture_top</i> field
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contains one more than the number of the highest numbered captured substring so
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far. If no substrings have been captured, the value of <i>capture_top</i> is
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one. This is always the case when <b>pcre_dfa_exec()</b> is used, because it
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does not support captured substrings.
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When the <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> is used, the
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<i>capture_top</i> field contains one more than the number of the highest
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numbered captured substring so far. If no substrings have been captured, the
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value of <i>capture_top</i> is one. This is always the case when the DFA
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functions are used, because they do not support captured substrings.
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</P>
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<P>
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The <i>capture_last</i> field contains the number of the most recently captured
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substring. If no substrings have been captured, its value is -1. This is always
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the case when <b>pcre_dfa_exec()</b> is used.
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the case for the DFA matching functions.
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</P>
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<P>
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The <i>callout_data</i> field contains a value that is passed to
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<b>pcre_exec()</b> or <b>pcre_dfa_exec()</b> specifically so that it can be
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passed back in callouts. It is passed in the <i>pcre_callout</i> field of the
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<b>pcre_extra</b> data structure. If no such data was passed, the value of
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<i>callout_data</i> in a <b>pcre_callout</b> block is NULL. There is a
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description of the <b>pcre_extra</b> structure in the
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The <i>callout_data</i> field contains a value that is passed to a matching
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function specifically so that it can be passed back in callouts. It is passed
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in the <i>callout_data</i> field of a <b>pcre_extra</b> or <b>pcre[16|32]_extra</b>
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data structure. If no such data was passed, the value of <i>callout_data</i> in
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a callout block is NULL. There is a description of the <b>pcre_extra</b>
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structure in the
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<a href="pcreapi.html"><b>pcreapi</b></a>
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documentation.
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</P>
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<P>
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The <i>pattern_position</i> field is present from version 1 of the
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<i>pcre_callout</i> structure. It contains the offset to the next item to be
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matched in the pattern string.
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The <i>pattern_position</i> field is present from version 1 of the callout
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structure. It contains the offset to the next item to be matched in the pattern
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string.
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</P>
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<P>
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The <i>next_item_length</i> field is present from version 1 of the
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<i>pcre_callout</i> structure. It contains the length of the next item to be
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matched in the pattern string. When the callout immediately precedes an
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alternation bar, a closing parenthesis, or the end of the pattern, the length
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is zero. When the callout precedes an opening parenthesis, the length is that
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of the entire subpattern.
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The <i>next_item_length</i> field is present from version 1 of the callout
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structure. It contains the length of the next item to be matched in the pattern
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string. When the callout immediately precedes an alternation bar, a closing
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parenthesis, or the end of the pattern, the length is zero. When the callout
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precedes an opening parenthesis, the length is that of the entire subpattern.
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</P>
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<P>
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The <i>pattern_position</i> and <i>next_item_length</i> fields are intended to
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help in distinguishing between different automatic callouts, which all have the
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same callout number. However, they are set for all callouts.
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</P>
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<br><a name="SEC4" href="#TOC1">RETURN VALUES</a><br>
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<P>
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The <i>mark</i> field is present from version 2 of the callout structure. In
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callouts from <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> it contains a pointer to
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the zero-terminated name of the most recently passed (*MARK), (*PRUNE), or
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(*THEN) item in the match, or NULL if no such items have been passed. Instances
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of (*PRUNE) or (*THEN) without a name do not obliterate a previous (*MARK). In
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callouts from the DFA matching functions this field always contains NULL.
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</P>
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<br><a name="SEC5" href="#TOC1">RETURN VALUES</a><br>
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<P>
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The external callout function returns an integer to PCRE. If the value is zero,
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matching proceeds as normal. If the value is greater than zero, matching fails
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at the current point, but the testing of other matching possibilities goes
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ahead, just as if a lookahead assertion had failed. If the value is less than
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zero, the match is abandoned, and <b>pcre_exec()</b> (or <b>pcre_dfa_exec()</b>)
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returns the negative value.
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zero, the match is abandoned, the matching function returns the negative value.
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</P>
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<P>
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Negative values should normally be chosen from the set of PCRE_ERROR_xxx
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@@ -188,7 +223,7 @@ values. In particular, PCRE_ERROR_NOMATCH forces a standard "no match" failure.
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The error number PCRE_ERROR_CALLOUT is reserved for use by callout functions;
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it will never be used by PCRE itself.
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</P>
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<br><a name="SEC5" href="#TOC1">AUTHOR</a><br>
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<br><a name="SEC6" href="#TOC1">AUTHOR</a><br>
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<P>
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Philip Hazel
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<br>
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@@ -197,11 +232,11 @@ University Computing Service
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Cambridge CB2 3QH, England.
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<br>
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</P>
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<br><a name="SEC6" href="#TOC1">REVISION</a><br>
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<br><a name="SEC7" href="#TOC1">REVISION</a><br>
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<P>
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Last updated: 15 March 2009
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Last updated: 24 June 2012
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<br>
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Copyright © 1997-2009 University of Cambridge.
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Copyright © 1997-2012 University of Cambridge.
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<br>
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<p>
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Return to the <a href="index.html">PCRE index page</a>.
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