2 .\" The Regents of the University of California. All rights reserved.
4 .\" This code is derived from software contributed to Berkeley by
5 .\" Paul Borman at Krystal Technologies.
7 .\" Redistribution and use in source and binary forms, with or without
8 .\" modification, are permitted provided that the following conditions
10 .\" 1. Redistributions of source code must retain the above copyright
11 .\" notice, this list of conditions and the following disclaimer.
12 .\" 2. Redistributions in binary form must reproduce the above copyright
13 .\" notice, this list of conditions and the following disclaimer in the
14 .\" documentation and/or other materials provided with the distribution.
15 .\" 3. All advertising materials mentioning features or use of this software
16 .\" must display the following acknowledgement:
17 .\" This product includes software developed by the University of
18 .\" California, Berkeley and its contributors.
19 .\" 4. Neither the name of the University nor the names of its contributors
20 .\" may be used to endorse or promote products derived from this software
21 .\" without specific prior written permission.
23 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 .\" @(#)utf2.4 8.1 (Berkeley) 6/4/93
36 .\" $FreeBSD: src/lib/libc/locale/utf8.5,v 1.1.2.1 2002/10/24 11:00:52 tjr Exp $
43 .Nd "UTF-8, a transformation format of ISO 10646"
50 encoding represents UCS-4 characters as a sequence of octets, using
51 between 1 and 6 for each character.
52 It is backwards compatible with
54 so 0x00-0x7f refer to the
57 The multibyte encoding of non-
60 consist entirely of bytes whose high order bit is set.
62 encoding is represented by the following table:
64 [0x00000000 - 0x0000007f] [00000000.0bbbbbbb] -> 0bbbbbbb
65 [0x00000080 - 0x000007ff] [00000bbb.bbbbbbbb] -> 110bbbbb, 10bbbbbb
66 [0x00000800 - 0x0000ffff] [bbbbbbbb.bbbbbbbb] ->
67 1110bbbb, 10bbbbbb, 10bbbbbb
68 [0x00010000 - 0x001fffff] [00000000.000bbbbb.bbbbbbbb.bbbbbbbb] ->
69 11110bbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
70 [0x00200000 - 0x03ffffff] [000000bb.bbbbbbbb.bbbbbbbb.bbbbbbbb] ->
71 111110bb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
72 [0x04000000 - 0x7fffffff] [0bbbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb] ->
73 1111110b, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
76 If more than a single representation of a value exists (for example,
77 0x00; 0xC0 0x80; 0xE0 0x80 0x80) the shortest representation is always
79 Longer ones are detected as an error as they pose a potential
80 security risk, and destroy the 1:1 character:octet sequence mapping.
84 encoding supersedes the
87 The only differences between the two are that
89 handles the full 31-bit character set of
94 is limited to a 16-bit character set,
97 accepts redundant, non-"shortest form" representations of characters.
103 .%T "UTF-8, a transformation format of ISO 10646"
110 encoding is compatible with RFC 2279.