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diff --git a/libs/Pcre16/docs/doc/pcrecallout.3 b/libs/Pcre16/docs/doc/pcrecallout.3 deleted file mode 100644 index 8ebc995952..0000000000 --- a/libs/Pcre16/docs/doc/pcrecallout.3 +++ /dev/null @@ -1,255 +0,0 @@ -.TH PCRECALLOUT 3 "12 November 2013" "PCRE 8.34" -.SH NAME -PCRE - Perl-compatible regular expressions -.SH SYNOPSIS -.rs -.sp -.B #include <pcre.h> -.PP -.SM -.B int (*pcre_callout)(pcre_callout_block *); -.PP -.B int (*pcre16_callout)(pcre16_callout_block *); -.PP -.B int (*pcre32_callout)(pcre32_callout_block *); -. -.SH DESCRIPTION -.rs -.sp -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 (\fIpcre16_callout\fP for the 16-bit -library, \fIpcre32_callout\fP for the 32-bit library). 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)abc(?C2)def -.sp -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 -.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. If the pattern contains a conditional group whose condition is -an assertion, an automatic callout is inserted immediately before the -condition. Such a callout may also be inserted explicitly, for example: -.sp - (?(?C9)(?=a)ab|de) -.sp -This applies only to assertion conditions (because they are themselves -independent groups). -.P -Automatic callouts can be used for tracking the progress of pattern matching. -The -.\" HREF -\fBpcretest\fP -.\" -program has a pattern qualifier (/C) that sets automatic callouts; when it is -used, the output indicates how the pattern is being 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 compiles and -matches patterns, callouts sometimes do not happen exactly as you might expect. -.P -At compile time, PCRE "auto-possessifies" repeated items when it knows that -what follows cannot be part of the repeat. For example, a+[bc] is compiled as -if it were a++[bc]. The \fBpcretest\fP output when this pattern is anchored and -then applied with automatic callouts to the string "aaaa" is: -.sp - --->aaaa - +0 ^ ^ - +1 ^ a+ - +3 ^ ^ [bc] - No match -.sp -This indicates that when matching [bc] fails, there is no backtracking into a+ -and therefore the callouts that would be taken for the backtracks do not occur. -You can disable the auto-possessify feature by passing PCRE_NO_AUTO_POSSESS -to \fBpcre_compile()\fP, or starting the pattern with (*NO_AUTO_POSSESS). If -this is done in \fBpcretest\fP (using the /O qualifier), the output changes to -this: -.sp - --->aaaa - +0 ^ ^ - +1 ^ a+ - +3 ^ ^ [bc] - +3 ^ ^ [bc] - +3 ^ ^ [bc] - +3 ^^ [bc] - No match -.sp -This time, when matching [bc] fails, the matcher backtracks into a+ and tries -again, repeatedly, until a+ itself fails. -.P -Other optimizations that provide fast "no match" results also affect callouts. -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. -.P -If the pattern is studied, PCRE knows the minimum length of a matching string, -and will immediately give a "no match" return without actually running a match -if the subject is not long enough, or, for unanchored patterns, if it has -been scanned far enough. -.P -You can disable these optimizations by passing the PCRE_NO_START_OPTIMIZE -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. -. -. -.SH "THE CALLOUT INTERFACE" -.rs -.sp -During matching, when PCRE reaches a callout point, the external function -defined by \fIpcre_callout\fP or \fIpcre[16|32]_callout\fP 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 \fBpcre_callout\fP or -\fBpcre[16|32]_callout\fP block. These structures contains the following -fields: -.sp - int \fIversion\fP; - int \fIcallout_number\fP; - int *\fIoffset_vector\fP; - const char *\fIsubject\fP; (8-bit version) - PCRE_SPTR16 \fIsubject\fP; (16-bit version) - PCRE_SPTR32 \fIsubject\fP; (32-bit version) - 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; - const unsigned char *\fImark\fP; (8-bit version) - const PCRE_UCHAR16 *\fImark\fP; (16-bit version) - const PCRE_UCHAR32 *\fImark\fP; (32-bit version) -.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 2. 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 the matching function. When \fBpcre_exec()\fP or -\fBpcre[16|32]_exec()\fP 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 the DFA matching -functions, this field is not useful. -.P -The \fIsubject\fP and \fIsubject_length\fP fields contain copies of the values -that were passed to the matching function. -.P -The \fIstart_match\fP field normally contains the offset within the subject at -which the current match attempt started. However, if the escape sequence \eK -has been encountered, this value is changed to reflect the modified starting -point. 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 -When the \fBpcre_exec()\fP or \fBpcre[16|32]_exec()\fP is used, 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. This is always the case when the DFA -functions are used, because they do not support captured substrings. -.P -The \fIcapture_last\fP field contains the number of the most recently captured -substring. However, when a recursion exits, the value reverts to what it was -outside the recursion, as do the values of all captured substrings. If no -substrings have been captured, the value of \fIcapture_last\fP is -1. This is -always the case for the DFA matching functions. -.P -The \fIcallout_data\fP 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 \fIcallout_data\fP field of a \fBpcre_extra\fP or \fBpcre[16|32]_extra\fP -data structure. If no such data was passed, the value of \fIcallout_data\fP in -a callout 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 callout -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 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. -.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. -.P -The \fImark\fP field is present from version 2 of the callout structure. In -callouts from \fBpcre_exec()\fP or \fBpcre[16|32]_exec()\fP 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. -. -. -.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 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, the matching function 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. -. -. -.SH AUTHOR -.rs -.sp -.nf -Philip Hazel -University Computing Service -Cambridge CB2 3QH, England. -.fi -. -. -.SH REVISION -.rs -.sp -.nf -Last updated: 12 November 2013 -Copyright (c) 1997-2013 University of Cambridge. -.fi |