/[pcre]/code/trunk/doc/pcrecallout.3
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revision 168 by ph10, Tue May 29 15:18:18 2007 UTC revision 389 by ph10, Sun Mar 15 18:24:05 2009 UTC
# Line 44  trying to optimize the performance of a Line 44  trying to optimize the performance of a
44  .rs  .rs
45  .sp  .sp
46  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
47  patterns, callouts sometimes do not happen. For example, if the pattern is  patterns by default, callouts sometimes do not happen. For example, if the
48    pattern is
49  .sp  .sp
50    ab(?C4)cd    ab(?C4)cd
51  .sp  .sp
# Line 52  PCRE knows that any matching string must Line 53  PCRE knows that any matching string must
53  string is "abyz", the lack of "d" means that matching doesn't ever start, and  string is "abyz", the lack of "d" means that matching doesn't ever start, and
54  the callout is never reached. However, with "abyd", though the result is still  the callout is never reached. However, with "abyd", though the result is still
55  no match, the callout is obeyed.  no match, the callout is obeyed.
56    .P
57    You can disable these optimizations by passing the PCRE_NO_START_OPTIMIZE
58    option to \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. This slows down the
59    matching process, but does ensure that callouts such as the example above are
60    obeyed.
61  .  .
62  .  .
63  .SH "THE CALLOUT INTERFACE"  .SH "THE CALLOUT INTERFACE"
# Line 172  Cambridge CB2 3QH, England. Line 178  Cambridge CB2 3QH, England.
178  .rs  .rs
179  .sp  .sp
180  .nf  .nf
181  Last updated: 29 May 2007  Last updated: 15 March 2009
182  Copyright (c) 1997-2007 University of Cambridge.  Copyright (c) 1997-2009 University of Cambridge.
183  .fi  .fi

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