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diff --git a/srclib/pcre/doc/pcrecallout.3 b/srclib/pcre/doc/pcrecallout.3 deleted file mode 100644 index 5fd8ff8712..0000000000 --- a/srclib/pcre/doc/pcrecallout.3 +++ /dev/null @@ -1,155 +0,0 @@ -.TH PCRE 3 -.SH NAME -PCRE - Perl-compatible regular expressions -.SH "PCRE CALLOUTS" -.rs -.sp -.B int (*pcre_callout)(pcre_callout_block *); -.PP -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 \fIpcre_callout\fP. By default, this variable contains NULL, -which disables all calling out. -.P -Within a regular expression, (?C) indicates the points at which the external -function is to be called. Different callout points can be identified by putting -a number less than 256 after the letter C. The default value is zero. -For example, this pattern has two callout points: -.sp - (?C1)\deabc(?C2)def -.sp -If the PCRE_AUTO_CALLOUT option bit is set when \fBpcre_compile()\fP 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 -.sp - A(\ed{2}|--) -.sp -it is processed as if it were -.sp -(?C255)A(?C255)((?C255)\ed{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255) -.sp -Notice that there is a callout before and after each parenthesis and -alternation bar. Automatic callouts can be used for tracking the progress of -pattern matching. The -.\" HREF -\fBpcretest\fP -.\" -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 -trying to optimize the performance of a particular pattern. -. -. -.SH "MISSING CALLOUTS" -.rs -.sp -You should be aware that, because of optimizations in the way PCRE matches -patterns, callouts sometimes do not happen. For example, if the pattern is -.sp - ab(?C4)cd -.sp -PCRE knows that any matching string must contain the letter "d". If the subject -string is "abyz", the lack of "d" means that matching doesn't ever start, and -the callout is never reached. However, with "abyd", though the result is still -no match, the callout is obeyed. -. -. -.SH "THE CALLOUT INTERFACE" -.rs -.sp -During matching, when PCRE reaches a callout point, the external function -defined by \fIpcre_callout\fP is called (if it is set). The only argument is a -pointer to a \fBpcre_callout\fP block. This structure contains the following -fields: -.sp - int \fIversion\fP; - int \fIcallout_number\fP; - int *\fIoffset_vector\fP; - const char *\fIsubject\fP; - int \fIsubject_length\fP; - int \fIstart_match\fP; - int \fIcurrent_position\fP; - int \fIcapture_top\fP; - int \fIcapture_last\fP; - void *\fIcallout_data\fP; - int \fIpattern_position\fP; - int \fInext_item_length\fP; -.sp -The \fIversion\fP field is an integer containing the version number of the -block format. The initial version was 0; the current version is 1. The version -number will change again in future if additional fields are added, but the -intention is never to remove any of the existing fields. -.P -The \fIcallout_number\fP field contains the number of the callout, as compiled -into the pattern (that is, the number after ?C for manual callouts, and 255 for -automatically generated callouts). -.P -The \fIoffset_vector\fP field is a pointer to the vector of offsets that was -passed by the caller to \fBpcre_exec()\fP. 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. -.P -The \fIsubject\fP and \fIsubject_length\fP fields contain copies of the values -that were passed to \fBpcre_exec()\fP. -.P -The \fIstart_match\fP field contains the offset within the subject at which the -current match attempt started. If the pattern is not anchored, the callout -function may be called several times from the same point in the pattern for -different starting points in the subject. -.P -The \fIcurrent_position\fP field contains the offset within the subject of the -current match pointer. -.P -The \fIcapture_top\fP field contains one more than the number of the highest -numbered captured substring so far. If no substrings have been captured, -the value of \fIcapture_top\fP is one. -.P -The \fIcapture_last\fP field contains the number of the most recently captured -substring. If no substrings have been captured, its value is -1. -.P -The \fIcallout_data\fP field contains a value that is passed to -\fBpcre_exec()\fP by the caller specifically so that it can be passed back in -callouts. It is passed in the \fIpcre_callout\fP field of the \fBpcre_extra\fP -data structure. If no such data was passed, the value of \fIcallout_data\fP in -a \fBpcre_callout\fP block is NULL. There is a description of the -\fBpcre_extra\fP structure in the -.\" HREF -\fBpcreapi\fP -.\" -documentation. -.P -The \fIpattern_position\fP field is present from version 1 of the -\fIpcre_callout\fP structure. It contains the offset to the next item to be -matched in the pattern string. -.P -The \fInext_item_length\fP field is present from version 1 of the -\fIpcre_callout\fP 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. -.P -The \fIpattern_position\fP and \fInext_item_length\fP fields are intended to -help in distinguishing between different automatic callouts, which all have the -same callout number. However, they are set for all callouts. -. -. -.SH "RETURN VALUES" -.rs -.sp -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 -at the current point, but backtracking to test 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 \fBpcre_exec()\fP returns the negative -value. -.P -Negative values should normally be chosen from the set of PCRE_ERROR_xxx -values. In particular, PCRE_ERROR_NOMATCH forces a standard "no match" failure. -The error number PCRE_ERROR_CALLOUT is reserved for use by callout functions; -it will never be used by PCRE itself. -.P -.in 0 -Last updated: 09 September 2004 -.br -Copyright (c) 1997-2004 University of Cambridge. |