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Revision 836 - (show annotations)
Wed Dec 28 17:16:11 2011 UTC (7 years, 7 months ago) by ph10
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Merging all the changes from the pcre16 branch into the trunk.
1 .TH PCRELIMITS 3
2 .SH NAME
3 PCRE - Perl-compatible regular expressions
4 .SH "SIZE AND OTHER LIMITATIONS"
5 .rs
6 .sp
7 There are some size limitations in PCRE but it is hoped that they will never in
8 practice be relevant.
9 .P
10 The maximum length of a compiled pattern is 65539 (sic) bytes if PCRE is
11 compiled with the default internal linkage size of 2. If you want to process
12 regular expressions that are truly enormous, you can compile PCRE with an
13 internal linkage size of 3 or 4 (see the \fBREADME\fP file in the source
14 distribution and the
15 .\" HREF
16 \fBpcrebuild\fP
17 .\"
18 documentation for details). In these cases the limit is substantially larger.
19 However, the speed of execution is slower.
20 .P
21 All values in repeating quantifiers must be less than 65536.
22 .P
23 There is no limit to the number of parenthesized subpatterns, but there can be
24 no more than 65535 capturing subpatterns.
25 .P
26 There is a limit to the number of forward references to subsequent subpatterns
27 of around 200,000. Repeated forward references with fixed upper limits, for
28 example, (?2){0,100} when subpattern number 2 is to the right, are included in
29 the count. There is no limit to the number of backward references.
30 .P
31 The maximum length of name for a named subpattern is 32 characters, and the
32 maximum number of named subpatterns is 10000.
33 .P
34 The maximum length of a subject string is the largest positive number that an
35 integer variable can hold. However, when using the traditional matching
36 function, PCRE uses recursion to handle subpatterns and indefinite repetition.
37 This means that the available stack space may limit the size of a subject
38 string that can be processed by certain patterns. For a discussion of stack
39 issues, see the
40 .\" HREF
41 \fBpcrestack\fP
42 .\"
43 documentation.
44 .
45 .
46 .SH AUTHOR
47 .rs
48 .sp
49 .nf
50 Philip Hazel
51 University Computing Service
52 Cambridge CB2 3QH, England.
53 .fi
54 .
55 .
56 .SH REVISION
57 .rs
58 .sp
59 .nf
60 Last updated: 30 November 2011
61 Copyright (c) 1997-2011 University of Cambridge.
62 .fi

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