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pcre

    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 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