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Line 13 from the original man page. If there is any nonsense i
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Line 13 from the original man page. If there is any nonsense i
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man page, in case the conversion went wrong. |
man page, in case the conversion went wrong. |
<br> |
<br> |
<ul> |
<ul> |
<li><a name="TOC1" href="#SEC1">PCRE CALLOUTS</a> | <li><a name="TOC1" href="#SEC1">SYNOPSIS</a> |
<li><a name="TOC2" href="#SEC2">MISSING CALLOUTS</a> | <li><a name="TOC2" href="#SEC2">DESCRIPTION</a> |
<li><a name="TOC3" href="#SEC3">THE CALLOUT INTERFACE</a> | <li><a name="TOC3" href="#SEC3">MISSING CALLOUTS</a> |
<li><a name="TOC4" href="#SEC4">RETURN VALUES</a> | <li><a name="TOC4" href="#SEC4">THE CALLOUT INTERFACE</a> |
<li><a name="TOC5" href="#SEC5">AUTHOR</a> | <li><a name="TOC5" href="#SEC5">RETURN VALUES</a> |
<li><a name="TOC6" href="#SEC6">REVISION</a> | <li><a name="TOC6" href="#SEC6">AUTHOR</a> |
| <li><a name="TOC7" href="#SEC7">REVISION</a> |
</ul> |
</ul> |
<br><a name="SEC1" href="#TOC1">PCRE CALLOUTS</a><br> | <br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br> |
<P> |
<P> |
|
<b>#include <pcre.h></b> |
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</P> |
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<P> |
<b>int (*pcre_callout)(pcre_callout_block *);</b> |
<b>int (*pcre_callout)(pcre_callout_block *);</b> |
</P> |
</P> |
<P> |
<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> |
PCRE provides a feature called "callout", which is a means of temporarily |
PCRE provides a feature called "callout", which is a means of temporarily |
passing control to the caller of PCRE in the middle of pattern matching. The |
passing control to the caller of PCRE in the middle of pattern matching. The |
caller of PCRE provides an external function by putting its entry point in the |
caller of PCRE provides an external function by putting its entry point in the |
global variable <i>pcre_callout</i>. By default, this variable contains NULL, | global variable <i>pcre_callout</i> (<i>pcre16_callout</i> for the 16-bit |
which disables all calling out. | library, <i>pcre32_callout</i> for the 32-bit library). By default, this |
| variable contains NULL, which disables all calling out. |
</P> |
</P> |
<P> |
<P> |
Within a regular expression, (?C) indicates the points at which the external |
Within a regular expression, (?C) indicates the points at which the external |
Line 39 For example, this pattern has two callout points:
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Line 51 For example, this pattern has two callout points:
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<pre> |
<pre> |
(?C1)abc(?C2)def |
(?C1)abc(?C2)def |
</pre> |
</pre> |
If the PCRE_AUTO_CALLOUT option bit is set when <b>pcre_compile()</b> or | If the PCRE_AUTO_CALLOUT option bit is set when a pattern is compiled, PCRE |
<b>pcre_compile2()</b> is called, PCRE automatically inserts callouts, all with | automatically inserts callouts, all with number 255, before each item in the |
number 255, before each item in the pattern. For example, if PCRE_AUTO_CALLOUT | pattern. For example, if PCRE_AUTO_CALLOUT is used with the pattern |
is used with the pattern | |
<pre> |
<pre> |
A(\d{2}|--) |
A(\d{2}|--) |
</pre> |
</pre> |
Line 53 it is processed as if it were
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Line 64 it is processed as if it were
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<br> |
<br> |
<br> |
<br> |
Notice that there is a callout before and after each parenthesis and |
Notice that there is a callout before and after each parenthesis and |
alternation bar. Automatic callouts can be used for tracking the progress of | alternation bar. If the pattern contains a conditional group whose condition is |
pattern matching. The | an assertion, an automatic callout is inserted immediately before the |
| condition. Such a callout may also be inserted explicitly, for example: |
| <pre> |
| (?(?C9)(?=a)ab|de) |
| </pre> |
| This applies only to assertion conditions (because they are themselves |
| independent groups). |
| </P> |
| <P> |
| Automatic callouts can be used for tracking the progress of pattern matching. |
| The |
<a href="pcretest.html"><b>pcretest</b></a> |
<a href="pcretest.html"><b>pcretest</b></a> |
command has an option that sets automatic callouts; when it is used, the output |
command has an option that sets automatic callouts; when it is used, the output |
indicates how the pattern is matched. This is useful information when you are |
indicates how the pattern is matched. This is useful information when you are |
trying to optimize the performance of a particular pattern. |
trying to optimize the performance of a particular pattern. |
</P> |
</P> |
|
<br><a name="SEC3" href="#TOC1">MISSING CALLOUTS</a><br> |
<P> |
<P> |
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. |
|
</P> |
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<br><a name="SEC2" href="#TOC1">MISSING CALLOUTS</a><br> |
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<P> |
|
You should be aware that, because of optimizations in the way PCRE matches |
You should be aware that, because of optimizations in the way PCRE matches |
patterns by default, callouts sometimes do not happen. For example, if the |
patterns by default, callouts sometimes do not happen. For example, if the |
pattern is |
pattern is |
Line 86 been scanned far enough.
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Line 102 been scanned far enough.
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</P> |
</P> |
<P> |
<P> |
You can disable these optimizations by passing the PCRE_NO_START_OPTIMIZE |
You can disable these optimizations by passing the PCRE_NO_START_OPTIMIZE |
option to <b>pcre_compile()</b>, <b>pcre_exec()</b>, or <b>pcre_dfa_exec()</b>, | option to the matching function, or by starting the pattern with |
or by starting the pattern with (*NO_START_OPT). This slows down the matching | (*NO_START_OPT). This slows down the matching process, but does ensure that |
process, but does ensure that callouts such as the example above are obeyed. | callouts such as the example above are obeyed. |
</P> |
</P> |
<br><a name="SEC3" href="#TOC1">THE CALLOUT INTERFACE</a><br> | <br><a name="SEC4" href="#TOC1">THE CALLOUT INTERFACE</a><br> |
<P> |
<P> |
During matching, when PCRE reaches a callout point, the external function |
During matching, when PCRE reaches a callout point, the external function |
defined by <i>pcre_callout</i> is called (if it is set). This applies to both | defined by <i>pcre_callout</i> or <i>pcre[16|32]_callout</i> is called |
the <b>pcre_exec()</b> and the <b>pcre_dfa_exec()</b> matching functions. The | (if it is set). This applies to both normal and DFA matching. The only |
only argument to the callout function is a pointer to a <b>pcre_callout</b> | argument to the callout function is a pointer to a <b>pcre_callout</b> |
block. This structure contains the following fields: | or <b>pcre[16|32]_callout</b> block. |
| These structures contains the following fields: |
<pre> |
<pre> |
int <i>version</i>; | int <i>version</i>; |
int <i>callout_number</i>; | int <i>callout_number</i>; |
int *<i>offset_vector</i>; | int *<i>offset_vector</i>; |
const char *<i>subject</i>; | const char *<i>subject</i>; (8-bit version) |
int <i>subject_length</i>; | PCRE_SPTR16 <i>subject</i>; (16-bit version) |
int <i>start_match</i>; | PCRE_SPTR32 <i>subject</i>; (32-bit version) |
int <i>current_position</i>; | int <i>subject_length</i>; |
int <i>capture_top</i>; | int <i>start_match</i>; |
int <i>capture_last</i>; | int <i>current_position</i>; |
void *<i>callout_data</i>; | int <i>capture_top</i>; |
int <i>pattern_position</i>; | int <i>capture_last</i>; |
int <i>next_item_length</i>; | </pre> |
const unsigned char *<i>mark</i>; | int <i>pattern_position</i>; |
| int <i>next_item_length</i>; |
| const unsigned char *<i>mark</i>; (8-bit version) |
| const PCRE_UCHAR16 *<i>mark</i>; (16-bit version) |
| const PCRE_UCHAR32 *<i>mark</i>; (32-bit version) |
</pre> |
</pre> |
The <i>version</i> field is an integer containing the version number of the |
The <i>version</i> field is an integer containing the version number of the |
block format. The initial version was 0; the current version is 2. The version |
block format. The initial version was 0; the current version is 2. The version |
Line 124 automatically generated callouts).
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Line 145 automatically generated callouts).
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</P> |
</P> |
<P> |
<P> |
The <i>offset_vector</i> field is a pointer to the vector of offsets that was |
The <i>offset_vector</i> field is a pointer to the vector of offsets that was |
passed by the caller to <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. When | passed by the caller to the matching function. When <b>pcre_exec()</b> or |
<b>pcre_exec()</b> is used, the contents can be inspected in order to extract | <b>pcre[16|32]_exec()</b> is used, the contents can be inspected, in order to |
substrings that have been matched so far, in the same way as for extracting | extract substrings that have been matched so far, in the same way as for |
substrings after a match has completed. For <b>pcre_dfa_exec()</b> this field is | extracting substrings after a match has completed. For the DFA matching |
not useful. | functions, this field is not useful. |
</P> |
</P> |
<P> |
<P> |
The <i>subject</i> and <i>subject_length</i> fields contain copies of the values |
The <i>subject</i> and <i>subject_length</i> fields contain copies of the values |
that were passed to <b>pcre_exec()</b>. | that were passed to the matching function. |
</P> |
</P> |
<P> |
<P> |
The <i>start_match</i> field normally contains the offset within the subject at |
The <i>start_match</i> field normally contains the offset within the subject at |
Line 147 The <i>current_position</i> field contains the offset
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Line 168 The <i>current_position</i> field contains the offset
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current match pointer. |
current match pointer. |
</P> |
</P> |
<P> |
<P> |
When the <b>pcre_exec()</b> function is used, the <i>capture_top</i> field | When the <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> is used, the |
contains one more than the number of the highest numbered captured substring so | <i>capture_top</i> field contains one more than the number of the highest |
far. If no substrings have been captured, the value of <i>capture_top</i> is | numbered captured substring so far. If no substrings have been captured, the |
one. This is always the case when <b>pcre_dfa_exec()</b> is used, because it | value of <i>capture_top</i> is one. This is always the case when the DFA |
does not support captured substrings. | functions are used, because they do not support captured substrings. |
</P> |
</P> |
<P> |
<P> |
The <i>capture_last</i> field contains the number of the most recently captured |
The <i>capture_last</i> field contains the number of the most recently captured |
substring. If no substrings have been captured, its value is -1. This is always | substring. However, when a recursion exits, the value reverts to what it was |
the case when <b>pcre_dfa_exec()</b> is used. | outside the recursion, as do the values of all captured substrings. If no |
| substrings have been captured, the value of <i>capture_last</i> is -1. This is |
| always the case for the DFA matching functions. |
</P> |
</P> |
<P> |
<P> |
The <i>callout_data</i> field contains a value that is passed to | The <i>callout_data</i> field contains a value that is passed to a matching |
<b>pcre_exec()</b> or <b>pcre_dfa_exec()</b> specifically so that it can be | function specifically so that it can be passed back in callouts. It is passed |
passed back in callouts. It is passed in the <i>pcre_callout</i> field of the | in the <i>callout_data</i> field of a <b>pcre_extra</b> or <b>pcre[16|32]_extra</b> |
<b>pcre_extra</b> data structure. If no such data was passed, the value of | data structure. If no such data was passed, the value of <i>callout_data</i> in |
<i>callout_data</i> in a <b>pcre_callout</b> block is NULL. There is a | a callout block is NULL. There is a description of the <b>pcre_extra</b> |
description of the <b>pcre_extra</b> structure in the | structure in the |
<a href="pcreapi.html"><b>pcreapi</b></a> |
<a href="pcreapi.html"><b>pcreapi</b></a> |
documentation. |
documentation. |
</P> |
</P> |
<P> |
<P> |
The <i>pattern_position</i> field is present from version 1 of the | The <i>pattern_position</i> field is present from version 1 of the callout |
<i>pcre_callout</i> structure. It contains the offset to the next item to be | structure. It contains the offset to the next item to be matched in the pattern |
matched in the pattern string. | string. |
</P> |
</P> |
<P> |
<P> |
The <i>next_item_length</i> field is present from version 1 of the | The <i>next_item_length</i> field is present from version 1 of the callout |
<i>pcre_callout</i> structure. It contains the length of the next item to be | structure. It contains the length of the next item to be matched in the pattern |
matched in the pattern string. When the callout immediately precedes an | string. When the callout immediately precedes an alternation bar, a closing |
alternation bar, a closing parenthesis, or the end of the pattern, the length | parenthesis, or the end of the pattern, the length is zero. When the callout |
is zero. When the callout precedes an opening parenthesis, the length is that | precedes an opening parenthesis, the length is that of the entire subpattern. |
of the entire subpattern. | |
</P> |
</P> |
<P> |
<P> |
The <i>pattern_position</i> and <i>next_item_length</i> fields are intended to |
The <i>pattern_position</i> and <i>next_item_length</i> fields are intended to |
Line 187 help in distinguishing between different automatic cal
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Line 209 help in distinguishing between different automatic cal
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same callout number. However, they are set for all callouts. |
same callout number. However, they are set for all callouts. |
</P> |
</P> |
<P> |
<P> |
The <i>mark</i> field is present from version 2 of the <i>pcre_callout</i> | The <i>mark</i> field is present from version 2 of the callout structure. In |
structure. In callouts from <b>pcre_exec()</b> it contains a pointer to the | callouts from <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> it contains a |
zero-terminated name of the most recently passed (*MARK), (*PRUNE), or (*THEN) | pointer to the zero-terminated name of the most recently passed (*MARK), |
item in the match, or NULL if no such items have been passed. Instances of | (*PRUNE), or (*THEN) item in the match, or NULL if no such items have been |
(*PRUNE) or (*THEN) without a name do not obliterate a previous (*MARK). In | passed. Instances of (*PRUNE) or (*THEN) without a name do not obliterate a |
callouts from <b>pcre_dfa_exec()</b> this field always contains NULL. | previous (*MARK). In callouts from the DFA matching functions this field always |
| contains NULL. |
</P> |
</P> |
<br><a name="SEC4" href="#TOC1">RETURN VALUES</a><br> | <br><a name="SEC5" href="#TOC1">RETURN VALUES</a><br> |
<P> |
<P> |
The external callout function returns an integer to PCRE. If the value is zero, |
The external callout function returns an integer to PCRE. If the value is zero, |
matching proceeds as normal. If the value is greater than zero, matching fails |
matching proceeds as normal. If the value is greater than zero, matching fails |
at the current point, but the testing of other matching possibilities goes |
at the current point, but the testing of other matching possibilities goes |
ahead, just as if a lookahead assertion had failed. If the value is less than |
ahead, just as if a lookahead assertion had failed. If the value is less than |
zero, the match is abandoned, and <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b> | zero, the match is abandoned, the matching function returns the negative value. |
returns the negative value. | |
</P> |
</P> |
<P> |
<P> |
Negative values should normally be chosen from the set of PCRE_ERROR_xxx |
Negative values should normally be chosen from the set of PCRE_ERROR_xxx |
Line 209 values. In particular, PCRE_ERROR_NOMATCH forces a sta
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Line 231 values. In particular, PCRE_ERROR_NOMATCH forces a sta
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The error number PCRE_ERROR_CALLOUT is reserved for use by callout functions; |
The error number PCRE_ERROR_CALLOUT is reserved for use by callout functions; |
it will never be used by PCRE itself. |
it will never be used by PCRE itself. |
</P> |
</P> |
<br><a name="SEC5" href="#TOC1">AUTHOR</a><br> | <br><a name="SEC6" href="#TOC1">AUTHOR</a><br> |
<P> |
<P> |
Philip Hazel |
Philip Hazel |
<br> |
<br> |
Line 218 University Computing Service
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Line 240 University Computing Service
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Cambridge CB2 3QH, England. |
Cambridge CB2 3QH, England. |
<br> |
<br> |
</P> |
</P> |
<br><a name="SEC6" href="#TOC1">REVISION</a><br> | <br><a name="SEC7" href="#TOC1">REVISION</a><br> |
<P> |
<P> |
Last updated: 30 November 2011 | Last updated: 03 March 2013 |
<br> |
<br> |
Copyright © 1997-2011 University of Cambridge. | Copyright © 1997-2013 University of Cambridge. |
<br> |
<br> |
<p> |
<p> |
Return to the <a href="index.html">PCRE index page</a>. |
Return to the <a href="index.html">PCRE index page</a>. |