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pcre 8.34

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:  8: Return to the <a href="index.html">PCRE index page</a>. 9:  10:  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:   15:   16: SIZE AND OTHER LIMITATIONS 17:   18:  19: There are some size limitations in PCRE but it is hoped that they will never in 20: practice be relevant. 21:  22:  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, and 32-bit units for 25: the 32-bit library) if PCRE is compiled with the default internal linkage size, 26: which is 2 bytes for the 8-bit and 16-bit libraries, and 4 bytes for the 32-bit 27: library. If you want to process regular expressions that are truly enormous, 28: you can compile PCRE with an internal linkage size of 3 or 4 (when building the 29: 16-bit or 32-bit library, 3 is rounded up to 4). See the README file in 30: the source distribution and the 31: <a href="pcrebuild.html">pcrebuild</a> 32: documentation for details. In these cases the limit is substantially larger. 33: However, the speed of execution is slower. 34:  35:  36: All values in repeating quantifiers must be less than 65536. 37:  38:  39: There is no limit to the number of parenthesized subpatterns, but there can be 40: no more than 65535 capturing subpatterns. There is, however, a limit to the 41: depth of nesting of parenthesized subpatterns of all kinds. This is imposed in 42: order to limit the amount of system stack used at compile time. The limit can 43: be specified when PCRE is built; the default is 250. 44:  45:  46: There is a limit to the number of forward references to subsequent subpatterns 47: of around 200,000. Repeated forward references with fixed upper limits, for 48: example, (?2){0,100} when subpattern number 2 is to the right, are included in 49: the count. There is no limit to the number of backward references. 50:  51:  52: The maximum length of name for a named subpattern is 32 characters, and the 53: maximum number of named subpatterns is 10000. 54:  55:  56: The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or (*THEN) verb 57: is 255 for the 8-bit library and 65535 for the 16-bit and 32-bit libraries. 58:  59:  60: The maximum length of a subject string is the largest positive number that an 61: integer variable can hold. However, when using the traditional matching 62: function, PCRE uses recursion to handle subpatterns and indefinite repetition. 63: This means that the available stack space may limit the size of a subject 64: string that can be processed by certain patterns. For a discussion of stack 65: issues, see the 66: <a href="pcrestack.html">pcrestack</a> 67: documentation. 68:  69:   70: AUTHOR 71:   72:  73: Philip Hazel 74:   75: University Computing Service 76:   77: Cambridge CB2 3QH, England. 78:   79:  80:   81: REVISION 82:   83:  84: Last updated: 05 November 2013 85:   86: Copyright © 1997-2013 University of Cambridge. 87:   88:  89: Return to the <a href="index.html">PCRE index page</a>. 90: 