Annotation of embedaddon/pcre/doc/html/pcrelimits.html, revision 1.1.1.2
1.1 misho 1: <html>
2: <head>
3: <title>pcrelimits specification</title>
4: </head>
5: <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6: <h1>pcrelimits man page</h1>
7: <p>
8: Return to the <a href="index.html">PCRE index page</a>.
9: </p>
10: <p>
11: This page is part of the PCRE HTML documentation. It was generated automatically
12: from the original man page. If there is any nonsense in it, please consult the
13: man page, in case the conversion went wrong.
14: <br>
15: <br><b>
16: SIZE AND OTHER LIMITATIONS
17: </b><br>
18: <P>
19: There are some size limitations in PCRE but it is hoped that they will never in
20: practice be relevant.
21: </P>
22: <P>
1.1.1.2 ! misho 23: The maximum length of a compiled pattern is approximately 64K data units (bytes
! 24: for the 8-bit library, 16-bit units for the 16-bit library) if PCRE is compiled
! 25: with the default internal linkage size of 2 bytes. If you want to process
1.1 misho 26: regular expressions that are truly enormous, you can compile PCRE with an
1.1.1.2 ! misho 27: internal linkage size of 3 or 4 (when building the 16-bit library, 3 is rounded
! 28: up to 4). See the <b>README</b> file in the source distribution and the
1.1 misho 29: <a href="pcrebuild.html"><b>pcrebuild</b></a>
1.1.1.2 ! misho 30: documentation for details. In these cases the limit is substantially larger.
1.1 misho 31: However, the speed of execution is slower.
32: </P>
33: <P>
34: All values in repeating quantifiers must be less than 65536.
35: </P>
36: <P>
37: There is no limit to the number of parenthesized subpatterns, but there can be
38: no more than 65535 capturing subpatterns.
39: </P>
40: <P>
41: There is a limit to the number of forward references to subsequent subpatterns
42: of around 200,000. Repeated forward references with fixed upper limits, for
43: example, (?2){0,100} when subpattern number 2 is to the right, are included in
44: the count. There is no limit to the number of backward references.
45: </P>
46: <P>
47: The maximum length of name for a named subpattern is 32 characters, and the
48: maximum number of named subpatterns is 10000.
49: </P>
50: <P>
51: The maximum length of a subject string is the largest positive number that an
52: integer variable can hold. However, when using the traditional matching
53: function, PCRE uses recursion to handle subpatterns and indefinite repetition.
54: This means that the available stack space may limit the size of a subject
55: string that can be processed by certain patterns. For a discussion of stack
56: issues, see the
57: <a href="pcrestack.html"><b>pcrestack</b></a>
58: documentation.
59: </P>
60: <br><b>
61: AUTHOR
62: </b><br>
63: <P>
64: Philip Hazel
65: <br>
66: University Computing Service
67: <br>
68: Cambridge CB2 3QH, England.
69: <br>
70: </P>
71: <br><b>
72: REVISION
73: </b><br>
74: <P>
1.1.1.2 ! misho 75: Last updated: 08 January 2012
1.1 misho 76: <br>
1.1.1.2 ! misho 77: Copyright © 1997-2012 University of Cambridge.
1.1 misho 78: <br>
79: <p>
80: Return to the <a href="index.html">PCRE index page</a>.
81: </p>
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