Elliott Hughes | 0c26e19 | 2019-08-07 12:24:46 -0700 | [diff] [blame] | 1 | .TH PCRE2LIMITS 3 "03 February 2019" "PCRE2 10.33" |
Janis Danisevskis | 112c9cc | 2016-03-31 13:35:25 +0100 | [diff] [blame] | 2 | .SH NAME |
| 3 | PCRE2 - Perl-compatible regular expressions (revised API) |
| 4 | .SH "SIZE AND OTHER LIMITATIONS" |
| 5 | .rs |
| 6 | .sp |
| 7 | There are some size limitations in PCRE2 but it is hoped that they will never |
| 8 | in practice be relevant. |
| 9 | .P |
Elliott Hughes | 653c210 | 2019-01-09 15:41:36 -0800 | [diff] [blame] | 10 | The maximum size of a compiled pattern is approximately 64 thousand code units |
| 11 | for the 8-bit and 16-bit libraries if PCRE2 is compiled with the default |
| 12 | internal linkage size, which is 2 bytes for these libraries. If you want to |
| 13 | process regular expressions that are truly enormous, you can compile PCRE2 with |
| 14 | an internal linkage size of 3 or 4 (when building the 16-bit library, 3 is |
| 15 | rounded up to 4). See the \fBREADME\fP file in the source distribution and the |
Janis Danisevskis | 112c9cc | 2016-03-31 13:35:25 +0100 | [diff] [blame] | 16 | .\" HREF |
| 17 | \fBpcre2build\fP |
| 18 | .\" |
| 19 | documentation for details. In these cases the limit is substantially larger. |
| 20 | However, the speed of execution is slower. In the 32-bit library, the internal |
| 21 | linkage size is always 4. |
| 22 | .P |
| 23 | The maximum length of a source pattern string is essentially unlimited; it is |
| 24 | the largest number a PCRE2_SIZE variable can hold. However, the program that |
| 25 | calls \fBpcre2_compile()\fP can specify a smaller limit. |
| 26 | .P |
| 27 | The maximum length (in code units) of a subject string is one less than the |
| 28 | largest number a PCRE2_SIZE variable can hold. PCRE2_SIZE is an unsigned |
| 29 | integer type, usually defined as size_t. Its maximum value (that is |
| 30 | ~(PCRE2_SIZE)0) is reserved as a special indicator for zero-terminated strings |
| 31 | and unset offsets. |
| 32 | .P |
Janis Danisevskis | 112c9cc | 2016-03-31 13:35:25 +0100 | [diff] [blame] | 33 | All values in repeating quantifiers must be less than 65536. |
| 34 | .P |
| 35 | The maximum length of a lookbehind assertion is 65535 characters. |
| 36 | .P |
Elliott Hughes | 0c26e19 | 2019-08-07 12:24:46 -0700 | [diff] [blame] | 37 | There is no limit to the number of parenthesized groups, but there can be no |
| 38 | more than 65535 capture groups, and there is a limit to the depth of nesting of |
| 39 | parenthesized subpatterns of all kinds. This is imposed in order to limit the |
| 40 | amount of system stack used at compile time. The default limit can be specified |
| 41 | when PCRE2 is built; if not, the default is set to 250. An application can |
| 42 | change this limit by calling pcre2_set_parens_nest_limit() to set the limit in |
| 43 | a compile context. |
Janis Danisevskis | 112c9cc | 2016-03-31 13:35:25 +0100 | [diff] [blame] | 44 | .P |
Elliott Hughes | 0c26e19 | 2019-08-07 12:24:46 -0700 | [diff] [blame] | 45 | The maximum length of name for a named capture group is 32 code units, and the |
| 46 | maximum number of such groups is 10000. |
Janis Danisevskis | 112c9cc | 2016-03-31 13:35:25 +0100 | [diff] [blame] | 47 | .P |
| 48 | The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or (*THEN) verb |
Elliott Hughes | 9bc971b | 2018-07-27 13:23:14 -0700 | [diff] [blame] | 49 | is 255 code units for the 8-bit library and 65535 code units for the 16-bit and |
| 50 | 32-bit libraries. |
| 51 | .P |
| 52 | The maximum length of a string argument to a callout is the largest number a |
| 53 | 32-bit unsigned integer can hold. |
Janis Danisevskis | 112c9cc | 2016-03-31 13:35:25 +0100 | [diff] [blame] | 54 | . |
| 55 | . |
| 56 | .SH AUTHOR |
| 57 | .rs |
| 58 | .sp |
| 59 | .nf |
| 60 | Philip Hazel |
| 61 | University Computing Service |
| 62 | Cambridge, England. |
| 63 | .fi |
| 64 | . |
| 65 | . |
| 66 | .SH REVISION |
| 67 | .rs |
| 68 | .sp |
| 69 | .nf |
Elliott Hughes | 0c26e19 | 2019-08-07 12:24:46 -0700 | [diff] [blame] | 70 | Last updated: 02 February 2019 |
| 71 | Copyright (c) 1997-2019 University of Cambridge. |
Janis Danisevskis | 112c9cc | 2016-03-31 13:35:25 +0100 | [diff] [blame] | 72 | .fi |