+int (*pcre16_callout)(pcre16_callout_block *); +
+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 caller of PCRE provides an external function by putting its entry point in the -global variable pcre_callout. By default, this variable contains NULL, -which disables all calling out. +global variable pcre_callout (pcre16_callout for the 16-bit +library). By default, this variable contains NULL, which disables all calling +out.
Within a regular expression, (?C) indicates the points at which the external @@ -39,10 +43,9 @@ For example, this pattern has two callout points:
(?C1)abc(?C2)def-If the PCRE_AUTO_CALLOUT option bit is set when pcre_compile() or -pcre_compile2() is called, PCRE automatically inserts callouts, all with -number 255, before each item in the pattern. For example, if PCRE_AUTO_CALLOUT -is used with the pattern +If the PCRE_AUTO_CALLOUT option bit is set when a pattern is compiled, PCRE +automatically inserts callouts, all with number 255, before each item in the +pattern. For example, if PCRE_AUTO_CALLOUT is used with the pattern
A(\d{2}|--)
@@ -86,31 +89,33 @@ been scanned far enough.
You can disable these optimizations by passing the PCRE_NO_START_OPTIMIZE -option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(), -or by starting the pattern with (*NO_START_OPT). This slows down the matching -process, but does ensure that callouts such as the example above are obeyed. +option to the matching function, or by starting the pattern with +(*NO_START_OPT). This slows down the matching process, but does ensure that +callouts such as the example above are obeyed.
During matching, when PCRE reaches a callout point, the external function -defined by pcre_callout is called (if it is set). This applies to both -the pcre_exec() and the pcre_dfa_exec() matching functions. The -only argument to the callout function is a pointer to a pcre_callout -block. This structure contains the following fields: +defined by pcre_callout or pcre16_callout is called (if it is set). +This applies to both normal and DFA matching. The only argument to the callout +function is a pointer to a pcre_callout or pcre16_callout block. +These structures contains the following fields:
- int version; - int callout_number; - int *offset_vector; - const char *subject; - int subject_length; - int start_match; - int current_position; - int capture_top; - int capture_last; - void *callout_data; - int pattern_position; - int next_item_length; - const unsigned char *mark; + int version; + int callout_number; + int *offset_vector; + const char *subject; (8-bit version) + PCRE_SPTR16 subject; (16-bit version) + int subject_length; + int start_match; + int current_position; + int capture_top; + int capture_last; + void *callout_data; + int pattern_position; + int next_item_length; + const unsigned char *mark; (8-bit version) + const PCRE_UCHAR16 *mark; (16-bit version)The version field is an integer containing the version number of the block format. The initial version was 0; the current version is 2. The version @@ -124,15 +129,15 @@ automatically generated callouts).
The offset_vector field is a pointer to the vector of offsets that was -passed by the caller to pcre_exec() or pcre_dfa_exec(). When -pcre_exec() is used, the contents can be inspected in order to extract +passed by the caller to the matching function. When pcre_exec() or +pcre16_exec() is used, the contents can be inspected, in order to extract substrings that have been matched so far, in the same way as for extracting -substrings after a match has completed. For pcre_dfa_exec() this field is -not useful. +substrings after a match has completed. For the DFA matching functions, this +field is not useful.
The subject and subject_length fields contain copies of the values -that were passed to pcre_exec(). +that were passed to the matching function.
The start_match field normally contains the offset within the subject at @@ -147,39 +152,38 @@ The current_position field contains the offset current match pointer.
-When the pcre_exec() function is used, the capture_top field -contains one more than the number of the highest numbered captured substring so -far. If no substrings have been captured, the value of capture_top is -one. This is always the case when pcre_dfa_exec() is used, because it -does not support captured substrings. +When the pcre_exec() or pcre16_exec() is used, the +capture_top field contains one more than the number of the highest +numbered captured substring so far. If no substrings have been captured, the +value of capture_top is one. This is always the case when the DFA +functions are used, because they do not support captured substrings.
The capture_last field contains the number of the most recently captured substring. If no substrings have been captured, its value is -1. This is always -the case when pcre_dfa_exec() is used. +the case for the DFA matching functions.
-The callout_data field contains a value that is passed to -pcre_exec() or pcre_dfa_exec() specifically so that it can be -passed back in callouts. It is passed in the pcre_callout field of the -pcre_extra data structure. If no such data was passed, the value of -callout_data in a pcre_callout block is NULL. There is a -description of the pcre_extra structure in the +The callout_data field contains a value that is passed to a matching +function specifically so that it can be passed back in callouts. It is passed +in the callout_data field of a pcre_extra or pcre16_extra +data structure. If no such data was passed, the value of callout_data in +a callout block is NULL. There is a description of the pcre_extra +structure in the pcreapi documentation.
-The pattern_position field is present from version 1 of the -pcre_callout structure. It contains the offset to the next item to be -matched in the pattern string. +The pattern_position field is present from version 1 of the callout +structure. It contains the offset to the next item to be matched in the pattern +string.
-The next_item_length field is present from version 1 of the -pcre_callout structure. It contains the length of the next item to be -matched in the pattern string. When the callout immediately precedes an -alternation bar, a closing parenthesis, or the end of the pattern, the length -is zero. When the callout precedes an opening parenthesis, the length is that -of the entire subpattern. +The next_item_length field is present from version 1 of the callout +structure. It contains the length of the next item to be matched in the pattern +string. When the callout immediately precedes an alternation bar, a closing +parenthesis, or the end of the pattern, the length is zero. When the callout +precedes an opening parenthesis, the length is that of the entire subpattern.
The pattern_position and next_item_length fields are intended to @@ -187,12 +191,12 @@ help in distinguishing between different automatic cal same callout number. However, they are set for all callouts.
-The mark field is present from version 2 of the pcre_callout -structure. In callouts from pcre_exec() it contains a pointer to the -zero-terminated name of the most recently passed (*MARK), (*PRUNE), or (*THEN) -item in the match, or NULL if no such items have been passed. Instances of -(*PRUNE) or (*THEN) without a name do not obliterate a previous (*MARK). In -callouts from pcre_dfa_exec() this field always contains NULL. +The mark field is present from version 2 of the callout structure. In +callouts from pcre_exec() or pcre16_exec() it contains a pointer to +the zero-terminated name of the most recently passed (*MARK), (*PRUNE), or +(*THEN) item in the match, or NULL if no such items have been passed. Instances +of (*PRUNE) or (*THEN) without a name do not obliterate a previous (*MARK). In +callouts from the DFA matching functions this field always contains NULL.
@@ -200,8 +204,7 @@ The external callout function returns an integer to PC 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 ahead, just as if a lookahead assertion had failed. If the value is less than -zero, the match is abandoned, and pcre_exec() or pcre_dfa_exec() -returns the negative value. +zero, the match is abandoned, the matching function returns the negative value.
Negative values should normally be chosen from the set of PCRE_ERROR_xxx @@ -220,9 +223,9 @@ Cambridge CB2 3QH, England.
-Last updated: 30 November 2011
+Last updated: 08 Janurary 2012
-Copyright © 1997-2011 University of Cambridge.
+Copyright © 1997-2012 University of Cambridge.
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