Perl-совместимые регулярные выражения (Perl-compatible regular expressions)
Имя (Name)
PCRE - Perl-compatible regular expressions
SIZE AND OTHER LIMITATIONS
There are some size limitations in PCRE but it is hoped that they
will never in practice be relevant.
The maximum length of a compiled pattern is approximately 64K
data units (bytes for the 8-bit library, 16-bit units for the
16-bit library, and 32-bit units for the 32-bit library) if PCRE
is compiled with the default internal linkage size, which is 2
bytes for the 8-bit and 16-bit libraries, and 4 bytes for the
32-bit library. 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 README file in the source distribution
and the pcrebuild documentation for details. In these cases the
limit is substantially larger. However, the speed of execution
is slower.
All values in repeating quantifiers must be less than 65536.
There is no limit to the number of parenthesized subpatterns, but
there can be no more than 65535 capturing subpatterns. There is,
however, a limit to the depth of nesting of parenthesized
subpatterns of all kinds. This is imposed in order to limit the
amount of system stack used at compile time. The limit can be
specified when PCRE is built; the default is 250.
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.
The maximum length of name for a named subpattern is 32
characters, and the maximum number of named subpatterns is 10000.
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 libraries.
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 pcrestack documentation.
