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.TH PCREUNICODE 3 "14 April 2012" "PCRE 8.30" | .TH PCREUNICODE 3 "27 February 2013" "PCRE 8.33" |
.SH NAME |
.SH NAME |
PCRE - Perl-compatible regular expressions |
PCRE - Perl-compatible regular expressions |
.SH "UTF-8, UTF-16, AND UNICODE PROPERTY SUPPORT" | .SH "UTF-8, UTF-16, UTF-32, AND UNICODE PROPERTY SUPPORT" |
.rs |
.rs |
.sp |
.sp |
From Release 8.30, in addition to its previous UTF-8 support, PCRE also | As well as UTF-8 support, PCRE also supports UTF-16 (from release 8.30) and |
supports UTF-16 by means of a separate 16-bit library. This can be built as | UTF-32 (from release 8.32), by means of two additional libraries. They can be |
well as, or instead of, the 8-bit library. | built as well as, or instead of, the 8-bit library. |
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.SH "UTF-8 SUPPORT" |
.SH "UTF-8 SUPPORT" |
Line 18 support, and, in addition, you must call
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Line 18 support, and, in addition, you must call
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\fBpcre_compile()\fP |
\fBpcre_compile()\fP |
.\" |
.\" |
with the PCRE_UTF8 option flag, or the pattern must start with the sequence |
with the PCRE_UTF8 option flag, or the pattern must start with the sequence |
(*UTF8). When either of these is the case, both the pattern and any subject | (*UTF8) or (*UTF). When either of these is the case, both the pattern and any |
strings that are matched against it are treated as UTF-8 strings instead of | subject strings that are matched against it are treated as UTF-8 strings |
strings of 1-byte characters. | instead of strings of individual 1-byte characters. |
. |
. |
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.SH "UTF-16 SUPPORT" | .SH "UTF-16 AND UTF-32 SUPPORT" |
.rs |
.rs |
.sp |
.sp |
In order process UTF-16 strings, you must build PCRE's 16-bit library with UTF | In order process UTF-16 or UTF-32 strings, you must build PCRE's 16-bit or |
support, and, in addition, you must call | 32-bit library with UTF support, and, in addition, you must call |
.\" HTML <a href="pcre_compile.html"> | .\" HREF |
.\" </a> | |
\fBpcre16_compile()\fP |
\fBpcre16_compile()\fP |
.\" |
.\" |
with the PCRE_UTF16 option flag, or the pattern must start with the sequence | or |
(*UTF16). When either of these is the case, both the pattern and any subject | .\" HREF |
strings that are matched against it are treated as UTF-16 strings instead of | \fBpcre32_compile()\fP |
strings of 16-bit characters. | .\" |
| with the PCRE_UTF16 or PCRE_UTF32 option flag, as appropriate. Alternatively, |
| the pattern must start with the sequence (*UTF16), (*UTF32), as appropriate, or |
| (*UTF), which can be used with either library. When UTF mode is set, both the |
| pattern and any subject strings that are matched against it are treated as |
| UTF-16 or UTF-32 strings instead of strings of individual 16-bit or 32-bit |
| characters. |
. |
. |
. |
. |
.SH "UTF SUPPORT OVERHEAD" |
.SH "UTF SUPPORT OVERHEAD" |
Line 43 strings of 16-bit characters.
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Line 48 strings of 16-bit characters.
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.sp |
.sp |
If you compile PCRE with UTF support, but do not use it at run time, the |
If you compile PCRE with UTF support, but do not use it at run time, the |
library will be a bit bigger, but the additional run time overhead is limited |
library will be a bit bigger, but the additional run time overhead is limited |
to testing the PCRE_UTF8/16 flag occasionally, so should not be very big. | to testing the PCRE_UTF[8|16|32] flag occasionally, so should not be very big. |
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.SH "UNICODE PROPERTY SUPPORT" |
.SH "UNICODE PROPERTY SUPPORT" |
Line 54 support), the escape sequences \ep{..}, \eP{..}, and \
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Line 59 support), the escape sequences \ep{..}, \eP{..}, and \
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The available properties that can be tested are limited to the general |
The available properties that can be tested are limited to the general |
category properties such as Lu for an upper case letter or Nd for a decimal |
category properties such as Lu for an upper case letter or Nd for a decimal |
number, the Unicode script names such as Arabic or Han, and the derived |
number, the Unicode script names such as Arabic or Han, and the derived |
properties Any and L&. A full list is given in the | properties Any and L&. Full lists is given in the |
.\" HREF |
.\" HREF |
\fBpcrepattern\fP |
\fBpcrepattern\fP |
.\" |
.\" |
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and |
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.\" HREF |
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\fBpcresyntax\fP |
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.\" |
documentation. Only the short names for properties are supported. For example, |
documentation. Only the short names for properties are supported. For example, |
\ep{L} matches a letter. Its Perl synonym, \ep{Letter}, is not supported. |
\ep{L} matches a letter. Its Perl synonym, \ep{Letter}, is not supported. |
Furthermore, in Perl, many properties may optionally be prefixed by "Is", for |
Furthermore, in Perl, many properties may optionally be prefixed by "Is", for |
Line 75 place. From release 7.3 of PCRE, the check is accordin
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Line 84 place. From release 7.3 of PCRE, the check is accordin
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which are themselves derived from the Unicode specification. Earlier releases |
which are themselves derived from the Unicode specification. Earlier releases |
of PCRE followed the rules of RFC 2279, which allows the full range of 31-bit |
of PCRE followed the rules of RFC 2279, which allows the full range of 31-bit |
values (0 to 0x7FFFFFFF). The current check allows only values in the range U+0 |
values (0 to 0x7FFFFFFF). The current check allows only values in the range U+0 |
to U+10FFFF, excluding U+D800 to U+DFFF. | to U+10FFFF, excluding the surrogate area. (From release 8.33 the so-called |
| "non-character" code points are no longer excluded because Unicode corrigendum |
| #9 makes it clear that they should not be.) |
.P |
.P |
The excluded code points are the "Surrogate Area" of Unicode. They are reserved | Characters in the "Surrogate Area" of Unicode are reserved for use by UTF-16, |
for use by UTF-16, where they are used in pairs to encode codepoints with | where they are used in pairs to encode codepoints with values greater than |
values greater than 0xFFFF. The code points that are encoded by UTF-16 pairs | 0xFFFF. The code points that are encoded by UTF-16 pairs are available |
are available independently in the UTF-8 encoding. (In other words, the whole | independently in the UTF-8 and UTF-32 encodings. (In other words, the whole |
surrogate thing is a fudge for UTF-16 which unfortunately messes up UTF-8.) | surrogate thing is a fudge for UTF-16 which unfortunately messes up UTF-8 and |
| UTF-32.) |
.P |
.P |
If an invalid UTF-8 string is passed to PCRE, an error return is given. At |
If an invalid UTF-8 string is passed to PCRE, an error return is given. At |
compile time, the only additional information is the offset to the first byte |
compile time, the only additional information is the offset to the first byte |
Line 91 detailed reason code if the caller has provided memory
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Line 103 detailed reason code if the caller has provided memory
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.P |
.P |
In some situations, you may already know that your strings are valid, and |
In some situations, you may already know that your strings are valid, and |
therefore want to skip these checks in order to improve performance, for |
therefore want to skip these checks in order to improve performance, for |
example in the case of a long subject string that is being scanned repeatedly | example in the case of a long subject string that is being scanned repeatedly. |
with different patterns. If you set the PCRE_NO_UTF8_CHECK flag at compile time | If you set the PCRE_NO_UTF8_CHECK flag at compile time or at run time, PCRE |
or at run time, PCRE assumes that the pattern or subject it is given | assumes that the pattern or subject it is given (respectively) contains only |
(respectively) contains only valid UTF-8 codes. In this case, it does not | valid UTF-8 codes. In this case, it does not diagnose an invalid UTF-8 string. |
diagnose an invalid UTF-8 string. | |
.P |
.P |
If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, what | Note that passing PCRE_NO_UTF8_CHECK to \fBpcre_compile()\fP just disables the |
happens depends on why the string is invalid. If the string conforms to the | check for the pattern; it does not also apply to subject strings. If you want |
"old" definition of UTF-8 (RFC 2279), it is processed as a string of characters | to disable the check for a subject string you must pass this option to |
in the range 0 to 0x7FFFFFFF by \fBpcre_dfa_exec()\fP and the interpreted | \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. |
version of \fBpcre_exec()\fP. In other words, apart from the initial validity | |
test, these functions (when in UTF-8 mode) handle strings according to the more | |
liberal rules of RFC 2279. However, the just-in-time (JIT) optimization for | |
\fBpcre_exec()\fP supports only RFC 3629. If you are using JIT optimization, or | |
if the string does not even conform to RFC 2279, the result is undefined. Your | |
program may crash. | |
.P |
.P |
If you want to process strings of values in the full range 0 to 0x7FFFFFFF, | If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, the result |
encoded in a UTF-8-like manner as per the old RFC, you can set | is undefined and your program may crash. |
PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in this | |
situation, you will have to apply your own validity check, and avoid the use of | |
JIT optimization. | |
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. |
. |
. |
.\" HTML <a name="utf16strings"></a> |
.\" HTML <a name="utf16strings"></a> |
Line 136 therefore want to skip these checks in order to improv
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Line 138 therefore want to skip these checks in order to improv
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the PCRE_NO_UTF16_CHECK flag at compile time or at run time, PCRE assumes that |
the PCRE_NO_UTF16_CHECK flag at compile time or at run time, PCRE assumes that |
the pattern or subject it is given (respectively) contains only valid UTF-16 |
the pattern or subject it is given (respectively) contains only valid UTF-16 |
sequences. In this case, it does not diagnose an invalid UTF-16 string. |
sequences. In this case, it does not diagnose an invalid UTF-16 string. |
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However, if an invalid string is passed, the result is undefined. |
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.\" HTML <a name="utf32strings"></a> |
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.SS "Validity of UTF-32 strings" |
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.rs |
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.sp |
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When you set the PCRE_UTF32 flag, the strings of 32-bit data units that are |
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passed as patterns and subjects are (by default) checked for validity on entry |
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to the relevant functions. This check allows only values in the range U+0 |
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to U+10FFFF, excluding the surrogate area U+D800 to U+DFFF. |
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.P |
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If an invalid UTF-32 string is passed to PCRE, an error return is given. At |
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compile time, the only additional information is the offset to the first data |
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unit of the failing character. The run-time functions \fBpcre32_exec()\fP and |
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\fBpcre32_dfa_exec()\fP also pass back this information, as well as a more |
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detailed reason code if the caller has provided memory in which to do this. |
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.P |
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In some situations, you may already know that your strings are valid, and |
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therefore want to skip these checks in order to improve performance. If you set |
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the PCRE_NO_UTF32_CHECK flag at compile time or at run time, PCRE assumes that |
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the pattern or subject it is given (respectively) contains only valid UTF-32 |
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sequences. In this case, it does not diagnose an invalid UTF-32 string. |
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However, if an invalid string is passed, the result is undefined. |
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. |
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. |
.SS "General comments about UTF modes" |
.SS "General comments about UTF modes" |
.rs |
.rs |
.sp |
.sp |
1. Codepoints less than 256 can be specified by either braced or unbraced | 1. Codepoints less than 256 can be specified in patterns by either braced or |
hexadecimal escape sequences (for example, \ex{b3} or \exb3). Larger values | unbraced hexadecimal escape sequences (for example, \ex{b3} or \exb3). Larger |
have to use braced sequences. | values have to use braced sequences. |
.P |
.P |
2. Octal numbers up to \e777 are recognized, and in UTF-8 mode, they match | 2. Octal numbers up to \e777 are recognized, and in UTF-8 mode they match |
two-byte characters for values greater than \e177. |
two-byte characters for values greater than \e177. |
.P |
.P |
3. Repeat quantifiers apply to complete UTF characters, not to individual |
3. Repeat quantifiers apply to complete UTF characters, not to individual |
Line 155 data units, for example: \ex{100}{3}.
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Line 181 data units, for example: \ex{100}{3}.
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unit. |
unit. |
.P |
.P |
5. The escape sequence \eC can be used to match a single byte in UTF-8 mode, or |
5. The escape sequence \eC can be used to match a single byte in UTF-8 mode, or |
a single 16-bit data unit in UTF-16 mode, but its use can lead to some strange | a single 16-bit data unit in UTF-16 mode, or a single 32-bit data unit in |
effects because it breaks up multi-unit characters (see the description of \eC | UTF-32 mode, but its use can lead to some strange effects because it breaks up |
in the | multi-unit characters (see the description of \eC in the |
.\" HREF |
.\" HREF |
\fBpcrepattern\fP |
\fBpcrepattern\fP |
.\" |
.\" |
documentation). The use of \eC is not supported in the alternative matching |
documentation). The use of \eC is not supported in the alternative matching |
function \fBpcre[16]_dfa_exec()\fP, nor is it supported in UTF mode by the JIT | function \fBpcre[16|32]_dfa_exec()\fP, nor is it supported in UTF mode by the |
optimization of \fBpcre[16]_exec()\fP. If JIT optimization is requested for a | JIT optimization of \fBpcre[16|32]_exec()\fP. If JIT optimization is requested |
UTF pattern that contains \eC, it will not succeed, and so the matching will | for a UTF pattern that contains \eC, it will not succeed, and so the matching |
be carried out by the normal interpretive function. | will be carried out by the normal interpretive function. |
.P |
.P |
6. The character escapes \eb, \eB, \ed, \eD, \es, \eS, \ew, and \eW correctly |
6. The character escapes \eb, \eB, \ed, \eD, \es, \eS, \ew, and \eW correctly |
test characters of any code value, but, by default, the characters that PCRE |
test characters of any code value, but, by default, the characters that PCRE |
Line 197 low-valued characters, unless the PCRE_UCP option is s
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Line 223 low-valued characters, unless the PCRE_UCP option is s
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PCRE_UCP is set. |
PCRE_UCP is set. |
.P |
.P |
9. Case-insensitive matching applies only to characters whose values are less |
9. Case-insensitive matching applies only to characters whose values are less |
than 128, unless PCRE is built with Unicode property support. Even when Unicode | than 128, unless PCRE is built with Unicode property support. A few Unicode |
property support is available, PCRE still uses its own character tables when | characters such as Greek sigma have more than two codepoints that are |
checking the case of low-valued characters, so as not to degrade performance. | case-equivalent. Up to and including PCRE release 8.31, only one-to-one case |
The Unicode property information is used only for characters with higher | mappings were supported, but later releases (with Unicode property support) do |
values. Furthermore, PCRE supports case-insensitive matching only when there is | treat as case-equivalent all versions of characters such as Greek sigma. |
a one-to-one mapping between a letter's cases. There are a small number of | |
many-to-one mappings in Unicode; these are not supported by PCRE. | |
. |
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.SH AUTHOR |
.SH AUTHOR |
Line 220 Cambridge CB2 3QH, England.
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Line 244 Cambridge CB2 3QH, England.
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.rs |
.rs |
.sp |
.sp |
.nf |
.nf |
Last updated: 14 April 2012 | Last updated: 27 February 2013 |
Copyright (c) 1997-2012 University of Cambridge. | Copyright (c) 1997-2013 University of Cambridge. |
.fi |
.fi |