87 lines
2.8 KiB
HTML
87 lines
2.8 KiB
HTML
<html>
|
|
<head>
|
|
<title>pcrelimits specification</title>
|
|
</head>
|
|
<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
|
|
<h1>pcrelimits man page</h1>
|
|
<p>
|
|
Return to the <a href="index.html">PCRE index page</a>.
|
|
</p>
|
|
<p>
|
|
This page is part of the PCRE HTML documentation. It was generated automatically
|
|
from the original man page. If there is any nonsense in it, please consult the
|
|
man page, in case the conversion went wrong.
|
|
<br>
|
|
<br><b>
|
|
SIZE AND OTHER LIMITATIONS
|
|
</b><br>
|
|
<P>
|
|
There are some size limitations in PCRE but it is hoped that they will never in
|
|
practice be relevant.
|
|
</P>
|
|
<P>
|
|
The maximum length of a compiled pattern is approximately 64K data units (bytes
|
|
for the 8-bit library, 32-bit units for the 32-bit library, and 32-bit units for
|
|
the 32-bit library) if PCRE is compiled with the default internal linkage size
|
|
of 2 bytes. If you want to process regular expressions that are truly enormous,
|
|
you can compile PCRE with an internal linkage size of 3 or 4 (when building the
|
|
16-bit or 32-bit library, 3 is rounded up to 4). See the <b>README</b> file in
|
|
the source distribution and the
|
|
<a href="pcrebuild.html"><b>pcrebuild</b></a>
|
|
documentation for details. In these cases the limit is substantially larger.
|
|
However, the speed of execution is slower.
|
|
</P>
|
|
<P>
|
|
All values in repeating quantifiers must be less than 65536.
|
|
</P>
|
|
<P>
|
|
There is no limit to the number of parenthesized subpatterns, but there can be
|
|
no more than 65535 capturing subpatterns.
|
|
</P>
|
|
<P>
|
|
There is a limit to the number of forward references to subsequent subpatterns
|
|
of around 200,000. Repeated forward references with fixed upper limits, for
|
|
example, (?2){0,100} when subpattern number 2 is to the right, are included in
|
|
the count. There is no limit to the number of backward references.
|
|
</P>
|
|
<P>
|
|
The maximum length of name for a named subpattern is 32 characters, and the
|
|
maximum number of named subpatterns is 10000.
|
|
</P>
|
|
<P>
|
|
The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or (*THEN) verb
|
|
is 255 for the 8-bit library and 65535 for the 16-bit and 32-bit library.
|
|
</P>
|
|
<P>
|
|
The maximum length of a subject string is the largest positive number that an
|
|
integer variable can hold. However, when using the traditional matching
|
|
function, PCRE uses recursion to handle subpatterns and indefinite repetition.
|
|
This means that the available stack space may limit the size of a subject
|
|
string that can be processed by certain patterns. For a discussion of stack
|
|
issues, see the
|
|
<a href="pcrestack.html"><b>pcrestack</b></a>
|
|
documentation.
|
|
</P>
|
|
<br><b>
|
|
AUTHOR
|
|
</b><br>
|
|
<P>
|
|
Philip Hazel
|
|
<br>
|
|
University Computing Service
|
|
<br>
|
|
Cambridge CB2 3QH, England.
|
|
<br>
|
|
</P>
|
|
<br><b>
|
|
REVISION
|
|
</b><br>
|
|
<P>
|
|
Last updated: 04 May 2012
|
|
<br>
|
|
Copyright © 1997-2012 University of Cambridge.
|
|
<br>
|
|
<p>
|
|
Return to the <a href="index.html">PCRE index page</a>.
|
|
</p>
|