/[pcre]/code/trunk/doc/pcrelimits.3
ViewVC logotype

Contents of /code/trunk/doc/pcrelimits.3

Parent Directory Parent Directory | Revision Log Revision Log


Revision 954 - (show annotations)
Sat Mar 31 18:09:26 2012 UTC (7 years, 4 months ago) by ph10
File size: 2125 byte(s)
Add date and PCRE version to .TH macros of all man pages.
1 .TH PCRELIMITS 3 "13 January 2012" "PCRE 8.30"
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 approximately 64K data units (bytes
11 for the 8-bit library, 16-bit units for the 16-bit library) if PCRE is compiled
12 with the default internal linkage size of 2 bytes. If you want to process
13 regular expressions that are truly enormous, you can compile PCRE with an
14 internal linkage size of 3 or 4 (when building the 16-bit library, 3 is rounded
15 up to 4). See the \fBREADME\fP file in the source distribution and the
16 .\" HREF
17 \fBpcrebuild\fP
18 .\"
19 documentation for details. In these cases the limit is substantially larger.
20 However, the speed of execution is slower.
21 .P
22 All values in repeating quantifiers must be less than 65536.
23 .P
24 There is no limit to the number of parenthesized subpatterns, but there can be
25 no more than 65535 capturing subpatterns.
26 .P
27 There is a limit to the number of forward references to subsequent subpatterns
28 of around 200,000. Repeated forward references with fixed upper limits, for
29 example, (?2){0,100} when subpattern number 2 is to the right, are included in
30 the count. There is no limit to the number of backward references.
31 .P
32 The maximum length of name for a named subpattern is 32 characters, and the
33 maximum number of named subpatterns is 10000.
34 .P
35 The maximum length of a subject string is the largest positive number that an
36 integer variable can hold. However, when using the traditional matching
37 function, PCRE uses recursion to handle subpatterns and indefinite repetition.
38 This means that the available stack space may limit the size of a subject
39 string that can be processed by certain patterns. For a discussion of stack
40 issues, see the
41 .\" HREF
42 \fBpcrestack\fP
43 .\"
44 documentation.
45 .
46 .
47 .SH AUTHOR
48 .rs
49 .sp
50 .nf
51 Philip Hazel
52 University Computing Service
53 Cambridge CB2 3QH, England.
54 .fi
55 .
56 .
57 .SH REVISION
58 .rs
59 .sp
60 .nf
61 Last updated: 08 January 2012
62 Copyright (c) 1997-2012 University of Cambridge.
63 .fi

  ViewVC Help
Powered by ViewVC 1.1.5