[apple/libc.git] / locale / FreeBSD / utf8.5

.\" Copyright (c) 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Paul Borman at Krystal Technologies.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"	@(#)utf2.4	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/locale/utf8.5,v 1.6 2004/10/17 02:29:15 tjr Exp $
.\"
.Dd April 7, 2004
.Dt UTF8 5
.Os
.Sh NAME
.Nm utf8
.Nd "UTF-8, a transformation format of ISO 10646"
.Sh SYNOPSIS
.Nm ENCODING
.Qq UTF-8
.Sh DESCRIPTION
The
.Nm UTF-8
encoding represents UCS-4 characters as a sequence of octets, using
between 1 and 6 for each character.
It is backwards compatible with
.Tn ASCII ,
so 0x00-0x7f refer to the
.Tn ASCII
character set.
The multibyte encoding of
.No non- Ns Tn ASCII
characters
consist entirely of bytes whose high order bit is set.
The actual
encoding is represented by the following table:
.Bd -literal
[0x00000000 - 0x0000007f] [00000000.0bbbbbbb] -> 0bbbbbbb
[0x00000080 - 0x000007ff] [00000bbb.bbbbbbbb] -> 110bbbbb, 10bbbbbb
[0x00000800 - 0x0000ffff] [bbbbbbbb.bbbbbbbb] ->
	1110bbbb, 10bbbbbb, 10bbbbbb
[0x00010000 - 0x001fffff] [00000000.000bbbbb.bbbbbbbb.bbbbbbbb] ->
	11110bbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
[0x00200000 - 0x03ffffff] [000000bb.bbbbbbbb.bbbbbbbb.bbbbbbbb] ->
	111110bb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
[0x04000000 - 0x7fffffff] [0bbbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb] ->
	1111110b, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
.Ed
.Pp
If more than a single representation of a value exists (for example,
0x00; 0xC0 0x80; 0xE0 0x80 0x80) the shortest representation is always
used.
Longer ones are detected as an error as they pose a potential
security risk, and destroy the 1:1 character:octet sequence mapping.
.Sh SEE ALSO
.Xr euc 5
.Rs
.%A "Rob Pike"
.%A "Ken Thompson"
.%T "Hello World"
.%J "Proceedings of the Winter 1993 USENIX Technical Conference"
.%Q "USENIX Association"
.%D "January 1993"
.Re
.Rs
.%A "F. Yergeau"
.%T "UTF-8, a transformation format of ISO 10646"
.%O "RFC 2279"
.%D "January 1998"
.Re
.Rs
.%Q "The Unicode Consortium"
.%T "The Unicode Standard, Version 3.0"
.%D "2000"
.%O "as amended by the Unicode Standard Annex #27: Unicode 3.1 and by the Unicode Standard Annex #28: Unicode 3.2"
.Re
.Sh STANDARDS
The
.Nm
encoding is compatible with RFC 2279 and Unicode 3.2.
Commit	Line	Data
5b2abdfb	1	.\" Copyright (c) 1993
e9ce8d39 A	2	.\" The Regents of the University of California. All rights reserved.
e9ce8d39 A	3	.\"
5b2abdfb A	4	.\" This code is derived from software contributed to Berkeley by
	5	.\" Paul Borman at Krystal Technologies.
	6	.\"
e9ce8d39 A	7	.\" Redistribution and use in source and binary forms, with or without
	8	.\" modification, are permitted provided that the following conditions
	9	.\" are met:
	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.
	22	.\"
	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
	33	.\" SUCH DAMAGE.
	34	.\"
5b2abdfb	35	.\" @(#)utf2.4 8.1 (Berkeley) 6/4/93
3d9156a7	36	.\" $FreeBSD: src/lib/libc/locale/utf8.5,v 1.6 2004/10/17 02:29:15 tjr Exp $
e9ce8d39	37	.\"
3d9156a7	38	.Dd April 7, 2004
9385eb3d	39	.Dt UTF8 5
e9ce8d39 A	40	.Os
e9ce8d39 A	41	.Sh NAME
9385eb3d A	42	.Nm utf8
9385eb3d A	43	.Nd "UTF-8, a transformation format of ISO 10646"
e9ce8d39	44	.Sh SYNOPSIS
5b2abdfb	45	.Nm ENCODING
9385eb3d	46	.Qq UTF-8
e9ce8d39 A	47	.Sh DESCRIPTION
e9ce8d39 A	48	The
9385eb3d A	49	.Nm UTF-8
	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
	53	.Tn ASCII ,
	54	so 0x00-0x7f refer to the
	55	.Tn ASCII
	56	character set.
	57	The multibyte encoding of
	58	.No non- Ns Tn ASCII
	59	characters
	60	consist entirely of bytes whose high order bit is set.
	61	The actual
5b2abdfb	62	encoding is represented by the following table:
e9ce8d39	63	.Bd -literal
9385eb3d A	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] ->
5b2abdfb	69	11110bbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
9385eb3d	70	[0x00200000 - 0x03ffffff] [000000bb.bbbbbbbb.bbbbbbbb.bbbbbbbb] ->
5b2abdfb	71	111110bb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
9385eb3d	72	[0x04000000 - 0x7fffffff] [0bbbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb] ->
5b2abdfb A	73	1111110b, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
	74	.Ed
	75	.Pp
9385eb3d A	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
	78	used.
	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.
9385eb3d	81	.Sh SEE ALSO
3d9156a7	82	.Xr euc 5
9385eb3d A	83	.Rs
	84	.%A "Rob Pike"
	85	.%A "Ken Thompson"
	86	.%T "Hello World"
	87	.%J "Proceedings of the Winter 1993 USENIX Technical Conference"
	88	.%Q "USENIX Association"
	89	.%D "January 1993"
	90	.Re
	91	.Rs
	92	.%A "F. Yergeau"
	93	.%T "UTF-8, a transformation format of ISO 10646"
	94	.%O "RFC 2279"
	95	.%D "January 1998"
	96	.Re
	97	.Rs
	98	.%Q "The Unicode Consortium"
	99	.%T "The Unicode Standard, Version 3.0"
	100	.%D "2000"
	101	.%O "as amended by the Unicode Standard Annex #27: Unicode 3.1 and by the Unicode Standard Annex #28: Unicode 3.2"
	102	.Re
	103	.Sh STANDARDS
	104	The
	105	.Nm
	106	encoding is compatible with RFC 2279 and Unicode 3.2.