version 1.1.1.2, 2012/02/21 23:50:25
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version 1.1.1.3, 2013/07/22 08:25:57
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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> |
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<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> |
<b>int (*pcre16_callout)(pcre16_callout_block *);</b> |
<b>int (*pcre16_callout)(pcre16_callout_block *);</b> |
</P> |
</P> |
<P> |
<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> (<i>pcre16_callout</i> for the 16-bit |
global variable <i>pcre_callout</i> (<i>pcre16_callout</i> for the 16-bit |
library). By default, this variable contains NULL, which disables all calling | library, <i>pcre32_callout</i> for the 32-bit library). By default, this |
out. | 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 56 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> |
|
<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 93 option to the matching function, or by starting the pa
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Line 106 option to the matching function, or by starting the pa
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(*NO_START_OPT). This slows down the matching process, but does ensure that |
(*NO_START_OPT). This slows down the matching 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> or <i>pcre16_callout</i> is called (if it is set). | defined by <i>pcre_callout</i> or <i>pcre[16|32]_callout</i> is called |
This applies to both normal and DFA matching. The only argument to the callout | (if it is set). This applies to both normal and DFA matching. The only |
function is a pointer to a <b>pcre_callout</b> or <b>pcre16_callout</b> block. | argument to the callout function is a pointer to a <b>pcre_callout</b> |
| or <b>pcre[16|32]_callout</b> block. |
These structures contains the following fields: |
These structures contains the following fields: |
<pre> |
<pre> |
int <i>version</i>; |
int <i>version</i>; |
Line 106 These structures contains the following fields:
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Line 120 These structures contains the following fields:
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int *<i>offset_vector</i>; |
int *<i>offset_vector</i>; |
const char *<i>subject</i>; (8-bit version) |
const char *<i>subject</i>; (8-bit version) |
PCRE_SPTR16 <i>subject</i>; (16-bit version) |
PCRE_SPTR16 <i>subject</i>; (16-bit version) |
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PCRE_SPTR32 <i>subject</i>; (32-bit version) |
int <i>subject_length</i>; |
int <i>subject_length</i>; |
int <i>start_match</i>; |
int <i>start_match</i>; |
int <i>current_position</i>; |
int <i>current_position</i>; |
Line 116 These structures contains the following fields:
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Line 131 These structures contains the following fields:
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int <i>next_item_length</i>; |
int <i>next_item_length</i>; |
const unsigned char *<i>mark</i>; (8-bit version) |
const unsigned char *<i>mark</i>; (8-bit version) |
const PCRE_UCHAR16 *<i>mark</i>; (16-bit version) |
const PCRE_UCHAR16 *<i>mark</i>; (16-bit version) |
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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 130 automatically generated callouts).
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Line 146 automatically generated callouts).
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<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 the matching function. When <b>pcre_exec()</b> or |
passed by the caller to the matching function. When <b>pcre_exec()</b> or |
<b>pcre16_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 the DFA matching functions, this | extracting substrings after a match has completed. For the DFA matching |
field is 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 |
Line 152 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> or <b>pcre16_exec()</b> is used, the | When the <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> is used, the |
<i>capture_top</i> field contains one more than the number of the highest |
<i>capture_top</i> field contains one more than the number of the highest |
numbered captured substring so far. If no substrings have been captured, the |
numbered captured substring so far. If no substrings have been captured, the |
value of <i>capture_top</i> is one. This is always the case when the DFA |
value of <i>capture_top</i> is one. This is always the case when the DFA |
Line 160 functions are used, because they do not support captur
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Line 176 functions are used, because they do not support captur
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</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 for the DFA matching functions. | 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 a matching |
The <i>callout_data</i> field contains a value that is passed to a matching |
function specifically so that it can be passed back in callouts. It is passed |
function specifically so that it can be passed back in callouts. It is passed |
in the <i>callout_data</i> field of a <b>pcre_extra</b> or <b>pcre16_extra</b> | in the <i>callout_data</i> field of a <b>pcre_extra</b> or <b>pcre[16|32]_extra</b> |
data structure. If no such data was passed, the value of <i>callout_data</i> in |
data structure. If no such data was passed, the value of <i>callout_data</i> in |
a callout block is NULL. There is a description of the <b>pcre_extra</b> |
a callout block is NULL. There is a description of the <b>pcre_extra</b> |
structure in the |
structure in the |
Line 192 same callout number. However, they are set for all cal
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Line 210 same callout number. However, they are set for all cal
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</P> |
</P> |
<P> |
<P> |
The <i>mark</i> field is present from version 2 of the callout structure. In |
The <i>mark</i> field is present from version 2 of the callout structure. In |
callouts from <b>pcre_exec()</b> or <b>pcre16_exec()</b> it contains a pointer to | callouts from <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> it contains a |
the zero-terminated name of the most recently passed (*MARK), (*PRUNE), or | pointer to the zero-terminated name of the most recently passed (*MARK), |
(*THEN) item in the match, or NULL if no such items have been passed. Instances | (*PRUNE), or (*THEN) item in the match, or NULL if no such items have been |
of (*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 the DFA matching functions 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 |
Line 212 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 221 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: 08 Janurary 2012 | Last updated: 03 March 2013 |
<br> |
<br> |
Copyright © 1997-2012 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>. |