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version 1.1.1.1, 2012/02/21 23:05:52	version 1.1.1.4, 2013/07/22 08:25:57
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man page, in case the conversion went wrong.	man page, in case the conversion went wrong.
<br>	<br>
<br><b>	<br><b>
UTF-8 AND UNICODE PROPERTY SUPPORT	UTF-8, UTF-16, UTF-32, AND UNICODE PROPERTY SUPPORT
</b><br>	</b><br>
<P>	<P>
In order process UTF-8 strings, you must build PCRE to include UTF-8 support in	As well as UTF-8 support, PCRE also supports UTF-16 (from release 8.30) and
the code, and, in addition, you must call	UTF-32 (from release 8.32), by means of two additional libraries. They can be
	built as well as, or instead of, the 8-bit library.
	</P>
	<br><b>
	UTF-8 SUPPORT
	</b><br>
	<P>
	In order process UTF-8 strings, you must build PCRE's 8-bit library with UTF
	support, and, in addition, you must call
<a href="pcre_compile.html"><b>pcre_compile()</b></a>	<a href="pcre_compile.html"><b>pcre_compile()</b></a>
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. PCRE does not support any other formats (in	instead of strings of individual 1-byte characters.
particular, it does not support UTF-16).
</P>	</P>
	<br><b>
	UTF-16 AND UTF-32 SUPPORT
	</b><br>
<P>	<P>
If you compile PCRE with UTF-8 support, but do not use it at run time, the	In order process UTF-16 or UTF-32 strings, you must build PCRE's 16-bit or
	32-bit library with UTF support, and, in addition, you must call
	<a href="pcre16_compile.html"><b>pcre16_compile()</b></a>
	or
	<a href="pcre32_compile.html"><b>pcre32_compile()</b></a>
	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.
	</P>
	<br><b>
	UTF SUPPORT OVERHEAD
	</b><br>
	<P>
	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_UTF[8\|16\|32] flag occasionally, so should not be very big.
</P>	</P>
	<br><b>
	UNICODE PROPERTY SUPPORT
	</b><br>
<P>	<P>
If PCRE is built with Unicode character property support (which implies UTF-8	If PCRE is built with Unicode character property support (which implies UTF
support), the escape sequences \p{..}, \P{..}, and \X are supported.	support), the escape sequences \p{..}, \P{..}, and \X 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
properties Any and L&. A full list is given in the	properties Any and L&. Full lists is given in the
<a href="pcrepattern.html"><b>pcrepattern</b></a>	<a href="pcrepattern.html"><b>pcrepattern</b></a>
	and
	<a href="pcresyntax.html"><b>pcresyntax</b></a>
documentation. Only the short names for properties are supported. For example,	documentation. Only the short names for properties are supported. For example,
\p{L} matches a letter. Its Perl synonym, \p{Letter}, is not supported.	\p{L} matches a letter. Its Perl synonym, \p{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 47 compatibility with Perl 5.6. PCRE does not support thi	Line 78 compatibility with Perl 5.6. PCRE does not support thi
Validity of UTF-8 strings	Validity of UTF-8 strings
</b><br>	</b><br>
<P>	<P>
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. The entire string is checked before any other processing takes
themselves derived from the Unicode specification. Earlier releases of PCRE	place. From release 7.3 of PCRE, the check is according the rules of RFC 3629,
followed the rules of RFC 2279, which allows the full range of 31-bit values (0	which are themselves derived from the Unicode specification. Earlier releases
to 0x7FFFFFFF). The current check allows only values in the range U+0 to	of PCRE followed the rules of RFC 2279, which allows the full range of 31-bit
U+10FFFF, excluding U+D800 to U+DFFF.	values (0 to 0x7FFFFFFF). The current check allows only values in the range U+0
	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>
<P>	<P>
The excluded code points are the "Low Surrogate Area" of Unicode, of which the	Characters in the "Surrogate Area" of Unicode are reserved for use by UTF-16,
Unicode Standard says this: "The Low Surrogate Area does not contain any	where they are used in pairs to encode codepoints with values greater than
character assignments, consequently no character code charts or namelists are	0xFFFF. The code points that are encoded by UTF-16 pairs are available
provided for this area. Surrogates are reserved for use with UTF-16 and then	independently in the UTF-8 and UTF-32 encodings. (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 and
available as independent code points in the UTF-8 encoding. (In other words,	UTF-32.)
the whole surrogate thing is a fudge for UTF-16 which unfortunately messes up
UTF-8.)
</P>	</P>
<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
of the failing character. The runtime functions <b>pcre_exec()</b> and	of the failing character. The run-time functions <b>pcre_exec()</b> and
<b>pcre_dfa_exec()</b> also pass back this information, as well as a more	<b>pcre_dfa_exec()</b> also pass back this information, as well as a more
detailed reason code if the caller has provided memory in which to do this.	detailed reason code if the caller has provided memory in which to do this.
</P>	</P>
<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
	example in the case of a long subject string that is being scanned repeatedly.
	If you set the PCRE_NO_UTF8_CHECK flag at compile time or at run time, PCRE
	assumes that the pattern or subject it is given (respectively) contains only
	valid UTF-8 codes. In this case, it does not diagnose an invalid UTF-8 string.
	</P>
	<P>
	Note that passing PCRE_NO_UTF8_CHECK to <b>pcre_compile()</b> just disables the
	check for the pattern; it does not also apply to subject strings. If you want
	to disable the check for a subject string you must pass this option to
	<b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>.
	</P>
	<P>
	If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, the result
	is undefined and your program may crash.
	<a name="utf16strings"></a></P>
	<br><b>
	Validity of UTF-16 strings
	</b><br>
	<P>
	When you set the PCRE_UTF16 flag, the strings of 16-bit data units that are
	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>
	If an invalid UTF-16 string is passed to PCRE, an error return is given. At
	compile time, the only additional information is the offset to the first data
	unit of the failing character. The run-time functions <b>pcre16_exec()</b> and
	<b>pcre16_dfa_exec()</b> 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>
	In some situations, you may already know that your strings are valid, and
therefore want to skip these checks in order to improve performance. If you set	therefore want to skip these checks in order to improve performance. If you set
the PCRE_NO_UTF8_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-8	the pattern or subject it is given (respectively) contains only valid UTF-16
codes. In this case, it does not diagnose an invalid UTF-8 string.	sequences. In this case, it does not diagnose an invalid UTF-16 string.
	However, if an invalid string is passed, the result is undefined.
	<a name="utf32strings"></a></P>
	<br><b>
	Validity of UTF-32 strings
	</b><br>
	<P>
	When you set the PCRE_UTF32 flag, the strings of 32-bit data units that are
	passed as patterns and subjects are (by default) checked for validity on entry
	to the relevant functions. This check allows only values in the range U+0
	to U+10FFFF, excluding the surrogate area U+D800 to U+DFFF.
</P>	</P>
<P>	<P>
If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, what	If an invalid UTF-32 string is passed to PCRE, an error return is given. At
happens depends on why the string is invalid. If the string conforms to the	compile time, the only additional information is the offset to the first data
"old" definition of UTF-8 (RFC 2279), it is processed as a string of characters	unit of the failing character. The run-time functions <b>pcre32_exec()</b> and
in the range 0 to 0x7FFFFFFF by <b>pcre_dfa_exec()</b> and the interpreted	<b>pcre32_dfa_exec()</b> also pass back this information, as well as a more
version of <b>pcre_exec()</b>. In other words, apart from the initial validity	detailed reason code if the caller has provided memory in which to do this.
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
<b>pcre_exec()</b> 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>
<P>	<P>
If you want to process strings of values in the full range 0 to 0x7FFFFFFF,	In some situations, you may already know that your strings are valid, and
encoded in a UTF-8-like manner as per the old RFC, you can set	therefore want to skip these checks in order to improve performance. If you set
PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in this	the PCRE_NO_UTF32_CHECK flag at compile time or at run time, PCRE assumes that
situation, you will have to apply your own validity check, and avoid the use of	the pattern or subject it is given (respectively) contains only valid UTF-32
JIT optimization.	sequences. In this case, it does not diagnose an invalid UTF-32 string.
	However, if an invalid string is passed, the result is undefined.
</P>	</P>
<br><b>	<br><b>
General comments about UTF-8 mode	General comments about UTF modes
</b><br>	</b><br>
<P>	<P>
1. An unbraced hexadecimal escape sequence (such as \xb3) matches a two-byte	1. Codepoints less than 256 can be specified in patterns by either braced or
UTF-8 character if the value is greater than 127.	unbraced hexadecimal escape sequences (for example, \x{b3} or \xb3). Larger
	values have to use braced sequences.
</P>	</P>
<P>	<P>
2. Octal numbers up to \777 are recognized, and match two-byte UTF-8	2. Octal numbers up to \777 are recognized, and in UTF-8 mode they match
characters for values greater than \177.	two-byte characters for values greater than \177.
</P>	</P>
<P>	<P>
3. Repeat quantifiers apply to complete UTF-8 characters, not to individual	3. Repeat quantifiers apply to complete UTF characters, not to individual
bytes, for example: \x{100}{3}.	data units, for example: \x{100}{3}.
</P>	</P>
<P>	<P>
4. The dot metacharacter matches one UTF-8 character instead of a single byte.	4. The dot metacharacter matches one UTF character instead of a single data
	unit.
</P>	</P>
<P>	<P>
5. The escape sequence \C can be used to match a single byte in UTF-8 mode,	5. The escape sequence \C can be used to match a single byte in UTF-8 mode, or
but its use can lead to some strange effects because it breaks up multibyte	a single 16-bit data unit in UTF-16 mode, or a single 32-bit data unit in
characters (see the description of \C in the	UTF-32 mode, but its use can lead to some strange effects because it breaks up
	multi-unit characters (see the description of \C in the
<a href="pcrepattern.html"><b>pcrepattern</b></a>	<a href="pcrepattern.html"><b>pcrepattern</b></a>
documentation). The use of \C is not supported in the alternative matching	documentation). The use of \C is not supported in the alternative matching
function <b>pcre_dfa_exec()</b>, nor is it supported in UTF-8 mode by the JIT	function <b>pcre[16\|32]_dfa_exec()</b>, nor is it supported in UTF mode by the
optimization of <b>pcre_exec()</b>. If JIT optimization is requested for a UTF-8	JIT optimization of <b>pcre[16\|32]_exec()</b>. If JIT optimization is requested
pattern that contains \C, it will not succeed, and so the matching will be	for a UTF pattern that contains \C, it will not succeed, and so the matching
carried out by the normal interpretive function.	will be carried out by the normal interpretive function.
</P>	</P>
<P>	<P>
6. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly	6. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W 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 \b and \B,	slow down PCRE in many common cases. Note in particular that this applies to
because they are defined in terms of \w and \W. If you really want to test	\b and \B, because they are defined in terms of \w and \W. 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 \p{Nd}. Alternatively, if you set the PCRE_UCP option, the way that	property tests such as \p{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
<a href="pcrepattern.html#genericchartypes">generic character types</a>	<a href="pcrepattern.html#genericchartypes">generic character types</a>
in the	in the
<a href="pcrepattern.html"><b>pcrepattern</b></a>	<a href="pcrepattern.html"><b>pcrepattern</b></a>
Line 149 documentation.	Line 226 documentation.
low-valued characters, unless the PCRE_UCP option is set.	low-valued characters, unless the PCRE_UCP option is set.
</P>	</P>
<P>	<P>
8. However, the horizontal and vertical whitespace matching escapes (\h, \H,	8. However, the horizontal and vertical white space matching escapes (\h, \H,
\v, and \V) do match all the appropriate Unicode characters, whether or not	\v, and \V) do match all the appropriate Unicode characters, whether or not
PCRE_UCP is set.	PCRE_UCP is set.
</P>	</P>
<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.
</P>	</P>
<br><b>	<br><b>
AUTHOR	AUTHOR
Line 178 Cambridge CB2 3QH, England.	Line 253 Cambridge CB2 3QH, England.
REVISION	REVISION
</b><br>	</b><br>
<P>	<P>
Last updated: 19 October 2011	Last updated: 27 February 2013
<br>	<br>
Copyright © 1997-2011 University of Cambridge.	Copyright © 1997-2013 University of Cambridge.
<br>	<br>
<p>	<p>
Return to the <a href="index.html">PCRE index page</a>.	Return to the <a href="index.html">PCRE index page</a>.

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