doc/html/pcreunicode.html

<html>
<head>
<title>pcreunicode specification</title>
</head>
<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
<h1>pcreunicode man page</h1>
<p>
Return to the <a href="index.html">PCRE index page</a>.
</p>
<p>
This page is part of the PCRE HTML documentation. It was generated automatically
from the original man page. If there is any nonsense in it, please consult the
man page, in case the conversion went wrong.
<br>
<br><b>
UTF-8, UTF-16, UTF-32, AND UNICODE PROPERTY SUPPORT
</b><br>
<P>
As well as UTF-8 support, PCRE also supports UTF-16 (from release 8.30) and
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>
with the PCRE_UTF8 option flag, or the pattern must start with the sequence
(*UTF8) or (*UTF). 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 of individual 1-byte characters.
</P>
<br><b>
UTF-16 AND UTF-32 SUPPORT
</b><br>
<P>
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
to testing the PCRE_UTF[8|16|32] flag occasionally, so should not be very big.
</P>
<br><b>
UNICODE PROPERTY SUPPORT
</b><br>
<P>
If PCRE is built with Unicode character property support (which implies UTF
support), the escape sequences \p{..}, \P{..}, and \X can be used.
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
number, the Unicode script names such as Arabic or Han, and the derived
properties Any and L&. Full lists is given in the
<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,
\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
compatibility with Perl 5.6. PCRE does not support this.
<a name="utf8strings"></a></P>
<br><b>
Validity of UTF-8 strings
</b><br>
<P>
When you set the PCRE_UTF8 flag, the byte strings passed as patterns and
subjects are (by default) checked for validity on entry to the relevant
functions. The entire string is checked before any other processing takes
place. From release 7.3 of PCRE, the check is according the rules of RFC 3629,
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
values (0 to 0x7FFFFFFF). The current check allows only values in the range U+0
to U+10FFFF, excluding the surrogate area and the non-characters.
</P>
<P>
Characters in the "Surrogate Area" of Unicode are reserved for use by UTF-16,
where they are used in pairs to encode codepoints with values greater than
0xFFFF. The code points that are encoded by UTF-16 pairs are available
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 and
UTF-32.)
</P>
<P>
Also excluded are the "Non-Character" code points, which are U+FDD0 to U+FDEF
and the last two code points in each plane, U+??FFFE and U+??FFFF.
</P>
<P>
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
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
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, 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>
Excluded are the "Non-Character" code points, which are U+FDD0 to U+FDEF
and the last two code points in each plane, U+??FFFE and U+??FFFF.
</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
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.
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, and the
"Non-Character" code points, which are U+FDD0 to U+FDEF and the last two
characters in each plane, U+??FFFE and U+??FFFF.
</P>
<P>
If an invalid UTF-32 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>pcre32_exec()</b> and
<b>pcre32_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
the PCRE_NO_UTF32_CHECK flag at compile time or at run time, PCRE assumes that
the pattern or subject it is given (respectively) contains only valid UTF-32
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>
<br><b>
General comments about UTF modes
</b><br>
<P>
1. Codepoints less than 256 can be specified in patterns by either braced or
unbraced hexadecimal escape sequences (for example, \x{b3} or \xb3). Larger
values have to use braced sequences.
</P>
<P>
2. Octal numbers up to \777 are recognized, and in UTF-8 mode they match
two-byte characters for values greater than \177.
</P>
<P>
3. Repeat quantifiers apply to complete UTF characters, not to individual
data units, for example: \x{100}{3}.
</P>
<P>
4. The dot metacharacter matches one UTF character instead of a single data
unit.
</P>
<P>
5. The escape sequence \C can be used to match a single byte in UTF-8 mode, or
a single 16-bit data unit in UTF-16 mode, or a single 32-bit data unit in
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>
documentation). The use of \C is not supported in the alternative matching
function <b>pcre[16|32]_dfa_exec()</b>, nor is it supported in UTF mode by the
JIT optimization of <b>pcre[16|32]_exec()</b>. If JIT optimization is requested
for a UTF pattern that contains \C, it will not succeed, and so the matching
will be carried out by the normal interpretive function.
</P>
<P>
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
recognizes as digits, spaces, or word characters remain the same set as in
non-UTF mode, all with values less than 256. This remains true even when PCRE
is built to include Unicode property support, because to do otherwise would
slow down PCRE in many common cases. Note in particular that this applies to
\b and \B, because they are defined in terms of \w and \W. If you really
want to test for a wider sense of, say, "digit", you can use explicit Unicode
property tests such as \p{Nd}. Alternatively, if you set the PCRE_UCP option,
the way that the character escapes work is changed so that Unicode properties
are used to determine which characters match. There are more details in the
section on
<a href="pcrepattern.html#genericchartypes">generic character types</a>
in the
<a href="pcrepattern.html"><b>pcrepattern</b></a>
documentation.
</P>
<P>
7. Similarly, characters that match the POSIX named character classes are all
low-valued characters, unless the PCRE_UCP option is set.
</P>
<P>
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
PCRE_UCP is set.
</P>
<P>
9. Case-insensitive matching applies only to characters whose values are less
than 128, unless PCRE is built with Unicode property support. A few Unicode
characters such as Greek sigma have more than two codepoints that are
case-equivalent. Up to and including PCRE release 8.31, only one-to-one case
mappings were supported, but later releases (with Unicode property support) do
treat as case-equivalent all versions of characters such as Greek sigma.
</P>
<br><b>
AUTHOR
</b><br>
<P>
Philip Hazel
<br>
University Computing Service
<br>
Cambridge CB2 3QH, England.
<br>
</P>
<br><b>
REVISION
</b><br>
<P>
Last updated: 11 November 2012
<br>
Copyright &copy; 1997-2012 University of Cambridge.
<br>
<p>
Return to the <a href="index.html">PCRE index page</a>.
</p>
1	<html>
2	<head>
3	<title>pcreunicode specification</title>
4	</head>
5	<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6	<h1>pcreunicode man page</h1>
7	<p>
8	Return to the <a href="index.html">PCRE index page</a>.
9	</p>
10	<p>
11	This page is part of the PCRE HTML documentation. It was generated automatically
12	from the original man page. If there is any nonsense in it, please consult the
13	man page, in case the conversion went wrong.
14	<br>
15	<br><b>
16	UTF-8, UTF-16, UTF-32, AND UNICODE PROPERTY SUPPORT
17	</b><br>
18	<P>
19	As well as UTF-8 support, PCRE also supports UTF-16 (from release 8.30) and
20	UTF-32 (from release 8.32), by means of two additional libraries. They can be
21	built as well as, or instead of, the 8-bit library.
22	</P>
23	<br><b>
24	UTF-8 SUPPORT
25	</b><br>
26	<P>
27	In order process UTF-8 strings, you must build PCRE's 8-bit library with UTF
28	support, and, in addition, you must call
29	<a href="pcre_compile.html"><b>pcre_compile()</b></a>
30	with the PCRE_UTF8 option flag, or the pattern must start with the sequence
31	(UTF8) or (UTF). When either of these is the case, both the pattern and any
32	subject strings that are matched against it are treated as UTF-8 strings
33	instead of strings of individual 1-byte characters.
34	</P>
35	<br><b>
36	UTF-16 AND UTF-32 SUPPORT
37	</b><br>
38	<P>
39	In order process UTF-16 or UTF-32 strings, you must build PCRE's 16-bit or
40	32-bit library with UTF support, and, in addition, you must call
41	<a href="pcre16_compile.html"><b>pcre16_compile()</b></a>
42	or
43	<a href="pcre32_compile.html"><b>pcre32_compile()</b></a>
44	with the PCRE_UTF16 or PCRE_UTF32 option flag, as appropriate. Alternatively,
45	the pattern must start with the sequence (UTF16), (UTF32), as appropriate, or
46	(*UTF), which can be used with either library. When UTF mode is set, both the
47	pattern and any subject strings that are matched against it are treated as
48	UTF-16 or UTF-32 strings instead of strings of individual 16-bit or 32-bit
49	characters.
50	</P>
51	<br><b>
52	UTF SUPPORT OVERHEAD
53	</b><br>
54	<P>
55	If you compile PCRE with UTF support, but do not use it at run time, the
56	library will be a bit bigger, but the additional run time overhead is limited
57	to testing the PCRE_UTF[8\|16\|32] flag occasionally, so should not be very big.
58	</P>
59	<br><b>
60	UNICODE PROPERTY SUPPORT
61	</b><br>
62	<P>
63	If PCRE is built with Unicode character property support (which implies UTF
64	support), the escape sequences \p{..}, \P{..}, and \X can be used.
65	The available properties that can be tested are limited to the general
66	category properties such as Lu for an upper case letter or Nd for a decimal
67	number, the Unicode script names such as Arabic or Han, and the derived
68	properties Any and L&. Full lists is given in the
69	<a href="pcrepattern.html"><b>pcrepattern</b></a>
70	and
71	<a href="pcresyntax.html"><b>pcresyntax</b></a>
72	documentation. Only the short names for properties are supported. For example,
73	\p{L} matches a letter. Its Perl synonym, \p{Letter}, is not supported.
74	Furthermore, in Perl, many properties may optionally be prefixed by "Is", for
75	compatibility with Perl 5.6. PCRE does not support this.
76	<a name="utf8strings"></a></P>
77	<br><b>
78	Validity of UTF-8 strings
79	</b><br>
80	<P>
81	When you set the PCRE_UTF8 flag, the byte strings passed as patterns and
82	subjects are (by default) checked for validity on entry to the relevant
83	functions. The entire string is checked before any other processing takes
84	place. From release 7.3 of PCRE, the check is according the rules of RFC 3629,
85	which are themselves derived from the Unicode specification. Earlier releases
86	of PCRE followed the rules of RFC 2279, which allows the full range of 31-bit
87	values (0 to 0x7FFFFFFF). The current check allows only values in the range U+0
88	to U+10FFFF, excluding the surrogate area and the non-characters.
89	</P>
90	<P>
91	Characters in the "Surrogate Area" of Unicode are reserved for use by UTF-16,
92	where they are used in pairs to encode codepoints with values greater than
93	0xFFFF. The code points that are encoded by UTF-16 pairs are available
94	independently in the UTF-8 and UTF-32 encodings. (In other words, the whole
95	surrogate thing is a fudge for UTF-16 which unfortunately messes up UTF-8 and
96	UTF-32.)
97	</P>
98	<P>
99	Also excluded are the "Non-Character" code points, which are U+FDD0 to U+FDEF
100	and the last two code points in each plane, U+??FFFE and U+??FFFF.
101	</P>
102	<P>
103	If an invalid UTF-8 string is passed to PCRE, an error return is given. At
104	compile time, the only additional information is the offset to the first byte
105	of the failing character. The run-time functions <b>pcre_exec()</b> and
106	<b>pcre_dfa_exec()</b> also pass back this information, as well as a more
107	detailed reason code if the caller has provided memory in which to do this.
108	</P>
109	<P>
110	In some situations, you may already know that your strings are valid, and
111	therefore want to skip these checks in order to improve performance, for
112	example in the case of a long subject string that is being scanned repeatedly.
113	If you set the PCRE_NO_UTF8_CHECK flag at compile time or at run time, PCRE
114	assumes that the pattern or subject it is given (respectively) contains only
115	valid UTF-8 codes. In this case, it does not diagnose an invalid UTF-8 string.
116	</P>
117	<P>
118	Note that passing PCRE_NO_UTF8_CHECK to <b>pcre_compile()</b> just disables the
119	check for the pattern; it does not also apply to subject strings. If you want
120	to disable the check for a subject string you must pass this option to
121	<b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>.
122	</P>
123	<P>
124	If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, the result
125	is undefined and your program may crash.
126	<a name="utf16strings"></a></P>
127	<br><b>
128	Validity of UTF-16 strings
129	</b><br>
130	<P>
131	When you set the PCRE_UTF16 flag, the strings of 16-bit data units that are
132	passed as patterns and subjects are (by default) checked for validity on entry
133	to the relevant functions. Values other than those in the surrogate range
134	U+D800 to U+DFFF are independent code points. Values in the surrogate range
135	must be used in pairs in the correct manner.
136	</P>
137	<P>
138	Excluded are the "Non-Character" code points, which are U+FDD0 to U+FDEF
139	and the last two code points in each plane, U+??FFFE and U+??FFFF.
140	</P>
141	<P>
142	If an invalid UTF-16 string is passed to PCRE, an error return is given. At
143	compile time, the only additional information is the offset to the first data
144	unit of the failing character. The run-time functions <b>pcre16_exec()</b> and
145	<b>pcre16_dfa_exec()</b> also pass back this information, as well as a more
146	detailed reason code if the caller has provided memory in which to do this.
147	</P>
148	<P>
149	In some situations, you may already know that your strings are valid, and
150	therefore want to skip these checks in order to improve performance. If you set
151	the PCRE_NO_UTF16_CHECK flag at compile time or at run time, PCRE assumes that
152	the pattern or subject it is given (respectively) contains only valid UTF-16
153	sequences. In this case, it does not diagnose an invalid UTF-16 string.
154	However, if an invalid string is passed, the result is undefined.
155	<a name="utf32strings"></a></P>
156	<br><b>
157	Validity of UTF-32 strings
158	</b><br>
159	<P>
160	When you set the PCRE_UTF32 flag, the strings of 32-bit data units that are
161	passed as patterns and subjects are (by default) checked for validity on entry
162	to the relevant functions. This check allows only values in the range U+0
163	to U+10FFFF, excluding the surrogate area U+D800 to U+DFFF, and the
164	"Non-Character" code points, which are U+FDD0 to U+FDEF and the last two
165	characters in each plane, U+??FFFE and U+??FFFF.
166	</P>
167	<P>
168	If an invalid UTF-32 string is passed to PCRE, an error return is given. At
169	compile time, the only additional information is the offset to the first data
170	unit of the failing character. The run-time functions <b>pcre32_exec()</b> and
171	<b>pcre32_dfa_exec()</b> also pass back this information, as well as a more
172	detailed reason code if the caller has provided memory in which to do this.
173	</P>
174	<P>
175	In some situations, you may already know that your strings are valid, and
176	therefore want to skip these checks in order to improve performance. If you set
177	the PCRE_NO_UTF32_CHECK flag at compile time or at run time, PCRE assumes that
178	the pattern or subject it is given (respectively) contains only valid UTF-32
179	sequences. In this case, it does not diagnose an invalid UTF-32 string.
180	However, if an invalid string is passed, the result is undefined.
181	</P>
182	<br><b>
183	General comments about UTF modes
184	</b><br>
185	<P>
186	1. Codepoints less than 256 can be specified in patterns by either braced or
187	unbraced hexadecimal escape sequences (for example, \x{b3} or \xb3). Larger
188	values have to use braced sequences.
189	</P>
190	<P>
191	2. Octal numbers up to \777 are recognized, and in UTF-8 mode they match
192	two-byte characters for values greater than \177.
193	</P>
194	<P>
195	3. Repeat quantifiers apply to complete UTF characters, not to individual
196	data units, for example: \x{100}{3}.
197	</P>
198	<P>
199	4. The dot metacharacter matches one UTF character instead of a single data
200	unit.
201	</P>
202	<P>
203	5. The escape sequence \C can be used to match a single byte in UTF-8 mode, or
204	a single 16-bit data unit in UTF-16 mode, or a single 32-bit data unit in
205	UTF-32 mode, but its use can lead to some strange effects because it breaks up
206	multi-unit characters (see the description of \C in the
207	<a href="pcrepattern.html"><b>pcrepattern</b></a>
208	documentation). The use of \C is not supported in the alternative matching
209	function <b>pcre[16\|32]_dfa_exec()</b>, nor is it supported in UTF mode by the
210	JIT optimization of <b>pcre[16\|32]_exec()</b>. If JIT optimization is requested
211	for a UTF pattern that contains \C, it will not succeed, and so the matching
212	will be carried out by the normal interpretive function.
213	</P>
214	<P>
215	6. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
216	test characters of any code value, but, by default, the characters that PCRE
217	recognizes as digits, spaces, or word characters remain the same set as in
218	non-UTF mode, all with values less than 256. This remains true even when PCRE
219	is built to include Unicode property support, because to do otherwise would
220	slow down PCRE in many common cases. Note in particular that this applies to
221	\b and \B, because they are defined in terms of \w and \W. If you really
222	want to test for a wider sense of, say, "digit", you can use explicit Unicode
223	property tests such as \p{Nd}. Alternatively, if you set the PCRE_UCP option,
224	the way that the character escapes work is changed so that Unicode properties
225	are used to determine which characters match. There are more details in the
226	section on
227	<a href="pcrepattern.html#genericchartypes">generic character types</a>
228	in the
229	<a href="pcrepattern.html"><b>pcrepattern</b></a>
230	documentation.
231	</P>
232	<P>
233	7. Similarly, characters that match the POSIX named character classes are all
234	low-valued characters, unless the PCRE_UCP option is set.
235	</P>
236	<P>
237	8. However, the horizontal and vertical white space matching escapes (\h, \H,
238	\v, and \V) do match all the appropriate Unicode characters, whether or not
239	PCRE_UCP is set.
240	</P>
241	<P>
242	9. Case-insensitive matching applies only to characters whose values are less
243	than 128, unless PCRE is built with Unicode property support. A few Unicode
244	characters such as Greek sigma have more than two codepoints that are
245	case-equivalent. Up to and including PCRE release 8.31, only one-to-one case
246	mappings were supported, but later releases (with Unicode property support) do
247	treat as case-equivalent all versions of characters such as Greek sigma.
248	</P>
249	<br><b>
250	AUTHOR
251	</b><br>
252	<P>
253	Philip Hazel
254	<br>
255	University Computing Service
256	<br>
257	Cambridge CB2 3QH, England.
258	<br>
259	</P>
260	<br><b>
261	REVISION
262	</b><br>
263	<P>
264	Last updated: 11 November 2012
265	<br>
266	Copyright © 1997-2012 University of Cambridge.
267	<br>
268	<p>
269	Return to the <a href="index.html">PCRE index page</a>.
270	</p>