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version 1.1, 2012/02/21 23:05:52	version 1.1.1.2, 2012/02/21 23:50:25
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.TH PCREUNICODE 3	.TH PCREUNICODE 3
.SH NAME	.SH NAME
PCRE - Perl-compatible regular expressions	PCRE - Perl-compatible regular expressions
.SH "UTF-8 AND UNICODE PROPERTY SUPPORT"	.SH "UTF-8, UTF-16, AND UNICODE PROPERTY SUPPORT"
.rs	.rs
.sp	.sp
In order process UTF-8 strings, you must build PCRE to include UTF-8 support in	From Release 8.30, in addition to its previous UTF-8 support, PCRE also
the code, and, in addition, you must call	supports UTF-16 by means of a separate 16-bit library. This can be built as
	well as, or instead of, the 8-bit library.
	.
	.
	.SH "UTF-8 SUPPORT"
	.rs
	.sp
	In order process UTF-8 strings, you must build PCRE's 8-bit library with UTF
	support, and, in addition, you must call
.\" HREF	.\" HREF
\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). When either of these is the case, both the pattern and any subject
strings that are matched against it are treated as UTF-8 strings instead of	strings that are matched against it are treated as UTF-8 strings instead of
strings of 1-byte characters. PCRE does not support any other formats (in	strings of 1-byte characters.
particular, it does not support UTF-16).	.
.P	.
If you compile PCRE with UTF-8 support, but do not use it at run time, the	.SH "UTF-16 SUPPORT"
	.rs
	.sp
	In order process UTF-16 strings, you must build PCRE's 16-bit library with UTF
	support, and, in addition, you must call
	.\" HTML <a href="pcre_compile.html">
	.\" </a>
	\fBpcre16_compile()\fP
	.\"
	with the PCRE_UTF16 option flag, or the pattern must start with the sequence
	(*UTF16). When either of these is the case, both the pattern and any subject
	strings that are matched against it are treated as UTF-16 strings instead of
	strings of 16-bit characters.
	.
	.
	.SH "UTF SUPPORT OVERHEAD"
	.rs
	.sp
	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 flag occasionally, so should not be very big.	to testing the PCRE_UTF8/16 flag occasionally, so should not be very big.
.P	.
If PCRE is built with Unicode character property support (which implies UTF-8	.
support), the escape sequences \ep{..}, \eP{..}, and \eX are supported.	.SH "UNICODE PROPERTY SUPPORT"
	.rs
	.sp
	If PCRE is built with Unicode character property support (which implies UTF
	support), the escape sequences \ep{..}, \eP{..}, and \eX can be used.
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
Line 38 compatibility with Perl 5.6. PCRE does not support thi	Line 68 compatibility with Perl 5.6. PCRE does not support thi
.SS "Validity of UTF-8 strings"	.SS "Validity of UTF-8 strings"
.rs	.rs
.sp	.sp
When you set the PCRE_UTF8 flag, the strings passed as patterns and subjects	When you set the PCRE_UTF8 flag, the byte strings passed as patterns and
are (by default) checked for validity on entry to the relevant functions. From	subjects are (by default) checked for validity on entry to the relevant
release 7.3 of PCRE, the check is according the rules of RFC 3629, which are	functions. From release 7.3 of PCRE, the check is according the rules of RFC
themselves derived from the Unicode specification. Earlier releases of PCRE	3629, which are themselves derived from the Unicode specification. Earlier
followed the rules of RFC 2279, which allows the full range of 31-bit values (0	releases of PCRE followed the rules of RFC 2279, which allows the full range of
to 0x7FFFFFFF). The current check allows only values in the range U+0 to	31-bit values (0 to 0x7FFFFFFF). The current check allows only values in the
U+10FFFF, excluding U+D800 to U+DFFF.	range U+0 to U+10FFFF, excluding U+D800 to U+DFFF.
.P	.P
The excluded code points are the "Low Surrogate Area" of Unicode, of which the	The excluded code points are the "Surrogate Area" of Unicode. They are reserved
Unicode Standard says this: "The Low Surrogate Area does not contain any	for use by UTF-16, where they are used in pairs to encode codepoints with
character assignments, consequently no character code charts or namelists are	values greater than 0xFFFF. The code points that are encoded by UTF-16 pairs
provided for this area. Surrogates are reserved for use with UTF-16 and then	are available independently in the UTF-8 encoding. (In other words, the whole
must be used in pairs." The code points that are encoded by UTF-16 pairs are	surrogate thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
available as independent code points in the UTF-8 encoding. (In other words,
the whole surrogate thing is a fudge for UTF-16 which unfortunately messes up
UTF-8.)
.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 85 situation, you will have to apply your own validity ch	Line 112 situation, you will have to apply your own validity ch
JIT optimization.	JIT optimization.
.	.
.	.
.SS "General comments about UTF-8 mode"	.\" HTML <a name="utf16strings"></a>
	.SS "Validity of UTF-16 strings"
.rs	.rs
.sp	.sp
1. An unbraced hexadecimal escape sequence (such as \exb3) matches a two-byte	When you set the PCRE_UTF16 flag, the strings of 16-bit data units that are
UTF-8 character if the value is greater than 127.	passed as patterns and subjects are (by default) checked for validity on entry
	to the relevant functions. Values other than those in the surrogate range
	U+D800 to U+DFFF are independent code points. Values in the surrogate range
	must be used in pairs in the correct manner.
.P	.P
2. Octal numbers up to \e777 are recognized, and match two-byte UTF-8	If an invalid UTF-16 string is passed to PCRE, an error return is given. At
characters for values greater than \e177.	compile time, the only additional information is the offset to the first data
	unit of the failing character. The runtime functions \fBpcre16_exec()\fP and
	\fBpcre16_dfa_exec()\fP also pass back this information, as well as a more
	detailed reason code if the caller has provided memory in which to do this.
.P	.P
3. Repeat quantifiers apply to complete UTF-8 characters, not to individual	In some situations, you may already know that your strings are valid, and
bytes, for example: \ex{100}{3}.	therefore want to skip these checks in order to improve performance. If you set
	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
	sequences. In this case, it does not diagnose an invalid UTF-16 string.
	.
	.
	.SS "General comments about UTF modes"
	.rs
	.sp
	1. Codepoints less than 256 can be specified by either braced or unbraced
	hexadecimal escape sequences (for example, \ex{b3} or \exb3). Larger values
	have to use braced sequences.
.P	.P
4. The dot metacharacter matches one UTF-8 character instead of a single byte.	2. Octal numbers up to \e777 are recognized, and in UTF-8 mode, they match
	two-byte characters for values greater than \e177.
.P	.P
5. The escape sequence \eC can be used to match a single byte in UTF-8 mode,	3. Repeat quantifiers apply to complete UTF characters, not to individual
but its use can lead to some strange effects because it breaks up multibyte	data units, for example: \ex{100}{3}.
characters (see the description of \eC in the	.P
	4. The dot metacharacter matches one UTF character instead of a single data
	unit.
	.P
	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
	effects because it breaks up 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_dfa_exec()\fP, nor is it supported in UTF-8 mode by the JIT	function \fBpcre[16]_dfa_exec()\fP, nor is it supported in UTF mode by the JIT
optimization of \fBpcre_exec()\fP. If JIT optimization is requested for a UTF-8	optimization of \fBpcre[16]_exec()\fP. If JIT optimization is requested for a
pattern that contains \eC, it will not succeed, and so the matching will be	UTF pattern that contains \eC, it will not succeed, and so the matching will
carried out by the normal interpretive function.	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
recognizes as digits, spaces, or word characters remain the same set as before,	recognizes as digits, spaces, or word characters remain the same set as in
all with values less than 256. This remains true even when PCRE is built to	non-UTF mode, all with values less than 256. This remains true even when PCRE
include Unicode property support, because to do otherwise would slow down PCRE	is built to include Unicode property support, because to do otherwise would
in many common cases. Note in particular that this applies to \eb and \eB,	slow down PCRE in many common cases. Note in particular that this applies to
because they are defined in terms of \ew and \eW. If you really want to test	\eb and \eB, because they are defined in terms of \ew and \eW. If you really
for a wider sense of, say, "digit", you can use explicit Unicode property tests	want to test for a wider sense of, say, "digit", you can use explicit Unicode
such as \ep{Nd}. Alternatively, if you set the PCRE_UCP option, the way that	property tests such as \ep{Nd}. Alternatively, if you set the PCRE_UCP option,
the character escapes work is changed so that Unicode properties are used to	the way that the character escapes work is changed so that Unicode properties
determine which characters match. There are more details in the section on	are used to determine which characters match. There are more details in the
	section on
.\" HTML <a href="pcrepattern.html#genericchartypes">	.\" HTML <a href="pcrepattern.html#genericchartypes">
.\" </a>	.\" </a>
generic character types	generic character types
Line 163 Cambridge CB2 3QH, England.	Line 217 Cambridge CB2 3QH, England.
.rs	.rs
.sp	.sp
.nf	.nf
Last updated: 19 October 2011	Last updated: 13 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
.fi	.fi

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