[apple/libc.git] / locale / FreeBSD / multibyte.3

.\" Copyright (c) 2002-2004 Tim J. Robbins. All rights reserved.
.\" Copyright (c) 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Donn Seeley of BSDI.
.\"
.\" 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.
.\" 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.
.\"
.\"	@(#)multibyte.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/locale/multibyte.3,v 1.28 2007/01/09 00:28:00 imp Exp $
.\"
.Dd April 8, 2004
.Dt MULTIBYTE 3
.Os
.Sh NAME
.Nm multibyte
.Nd multibyte and wide character manipulation functions
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In limits.h
.In stdlib.h
.In wchar.h
.Sh DESCRIPTION
The basic elements of some written natural languages, such as Chinese,
cannot be represented uniquely with single C
.Vt char Ns s .
The C standard supports two different ways of dealing with
extended natural language encodings:
wide characters and
multibyte characters.
Wide characters are an internal representation
which allows each basic element to map
to a single object of type
.Vt wchar_t .
Multibyte characters are used for input and output
and code each basic element as a sequence of C
.Vt char Ns s .
Individual basic elements may map into one or more
(up to
.Dv MB_LEN_MAX )
bytes in a multibyte character.
.Pp
The current locale
.Pq Xr setlocale 3
governs the interpretation of wide and multibyte characters.
The locale category
.Dv LC_CTYPE
specifically controls this interpretation.
The
.Vt wchar_t
type is wide enough to hold the largest value
in the wide character representations for all locales.
.Pp
Multibyte strings may contain
.Sq shift
indicators to switch to and from
particular modes within the given representation.
If explicit bytes are used to signal shifting,
these are not recognized as separate characters
but are lumped with a neighboring character.
There is always a distinguished
.Sq initial
shift state.
Some functions (e.g.,
.Xr mblen 3 ,
.Xr mbtowc 3
and
.Xr wctomb 3 )
maintain static shift state internally, whereas
others store it in an
.Vt mbstate_t
object passed by the caller.
Shift states are undefined after a call to
.Xr setlocale 3
with the
.Dv LC_CTYPE
or
.Dv LC_ALL
categories.
.Pp
For convenience in processing,
the wide character with value 0
(the null wide character)
is recognized as the wide character string terminator,
and the character with value 0
(the null byte)
is recognized as the multibyte character string terminator.
Null bytes are not permitted within multibyte characters.
.Pp
The C library provides the following functions for dealing with
multibyte characters:
.Bl -column "Description"
.It Sy "Function	Description"
.It Xr mblen 3 Ta "get number of bytes in a character"
.It Xr mbrlen 3 Ta "get number of bytes in a character (restartable)"
.It Xr mbrtowc 3 Ta "convert a character to a wide-character code (restartable)"
.It Xr mbsrtowcs 3 Ta "convert a character string to a wide-character string (restartable)"
.It Xr mbstowcs 3 Ta "convert a character string to a wide-character string"
.It Xr mbtowc 3 Ta "convert a character to a wide-character code"
.It Xr wcrtomb 3 Ta "convert a wide-character code to a character (restartable)"
.It Xr wcstombs 3 Ta "convert a wide-character string to a character string"
.It Xr wcsrtombs 3 Ta "convert a wide-character string to a character string (restartable)"
.It Xr wctomb 3 Ta "convert a wide-character code to a character"
.El
.Sh SEE ALSO
.Xr mklocale 1 ,
.Xr setlocale 3 ,
.Xr stdio 3 ,
.Xr big5 5 ,
.Xr euc 5 ,
.Xr gb18030 5 ,
.Xr gb2312 5 ,
.Xr gbk 5 ,
.Xr mskanji 5 ,
.Xr utf8 5
.Sh STANDARDS
These functions conform to
.St -isoC-99 .
Commit	Line	Data
3d9156a7	1	.\" Copyright (c) 2002-2004 Tim J. Robbins. All rights reserved.
5b2abdfb A	2	.\" Copyright (c) 1993
	3	.\" The Regents of the University of California. All rights reserved.
	4	.\"
	5	.\" This code is derived from software contributed to Berkeley by
	6	.\" Donn Seeley of BSDI.
	7	.\"
	8	.\" Redistribution and use in source and binary forms, with or without
	9	.\" modification, are permitted provided that the following conditions
	10	.\" are met:
	11	.\" 1. Redistributions of source code must retain the above copyright
	12	.\" notice, this list of conditions and the following disclaimer.
	13	.\" 2. Redistributions in binary form must reproduce the above copyright
	14	.\" notice, this list of conditions and the following disclaimer in the
	15	.\" documentation and/or other materials provided with the distribution.
5b2abdfb A	16	.\" 4. Neither the name of the University nor the names of its contributors
	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" @(#)multibyte.3 8.1 (Berkeley) 6/4/93
1f2f436a	33	.\" $FreeBSD: src/lib/libc/locale/multibyte.3,v 1.28 2007/01/09 00:28:00 imp Exp $
5b2abdfb	34	.\"
3d9156a7	35	.Dd April 8, 2004
5b2abdfb A	36	.Dt MULTIBYTE 3
	37	.Os
	38	.Sh NAME
3d9156a7 A	39	.Nm multibyte
3d9156a7 A	40	.Nd multibyte and wide character manipulation functions
5b2abdfb A	41	.Sh LIBRARY
	42	.Lb libc
	43	.Sh SYNOPSIS
3d9156a7	44	.In limits.h
5b2abdfb	45	.In stdlib.h
3d9156a7	46	.In wchar.h
5b2abdfb	47	.Sh DESCRIPTION
3d9156a7	48	The basic elements of some written natural languages, such as Chinese,
5b2abdfb	49	cannot be represented uniquely with single C
3d9156a7	50	.Vt char Ns s .
5b2abdfb	51	The C standard supports two different ways of dealing with
3d9156a7 A	52	extended natural language encodings:
	53	wide characters and
	54	multibyte characters.
5b2abdfb A	55	Wide characters are an internal representation
	56	which allows each basic element to map
	57	to a single object of type
3d9156a7	58	.Vt wchar_t .
5b2abdfb A	59	Multibyte characters are used for input and output
5b2abdfb A	60	and code each basic element as a sequence of C
3d9156a7	61	.Vt char Ns s .
5b2abdfb A	62	Individual basic elements may map into one or more
5b2abdfb A	63	(up to
9385eb3d	64	.Dv MB_LEN_MAX )
5b2abdfb A	65	bytes in a multibyte character.
	66	.Pp
	67	The current locale
	68	.Pq Xr setlocale 3
	69	governs the interpretation of wide and multibyte characters.
	70	The locale category
	71	.Dv LC_CTYPE
	72	specifically controls this interpretation.
	73	The
3d9156a7	74	.Vt wchar_t
5b2abdfb A	75	type is wide enough to hold the largest value
	76	in the wide character representations for all locales.
	77	.Pp
	78	Multibyte strings may contain
	79	.Sq shift
	80	indicators to switch to and from
	81	particular modes within the given representation.
	82	If explicit bytes are used to signal shifting,
	83	these are not recognized as separate characters
	84	but are lumped with a neighboring character.
	85	There is always a distinguished
	86	.Sq initial
	87	shift state.
3d9156a7 A	88	Some functions (e.g.,
	89	.Xr mblen 3 ,
	90	.Xr mbtowc 3
5b2abdfb	91	and
3d9156a7 A	92	.Xr wctomb 3 )
	93	maintain static shift state internally, whereas
	94	others store it in an
	95	.Vt mbstate_t
	96	object passed by the caller.
	97	Shift states are undefined after a call to
	98	.Xr setlocale 3
5b2abdfb A	99	with the
	100	.Dv LC_CTYPE
	101	or
	102	.Dv LC_ALL
	103	categories.
	104	.Pp
	105	For convenience in processing,
	106	the wide character with value 0
	107	(the null wide character)
	108	is recognized as the wide character string terminator,
	109	and the character with value 0
	110	(the null byte)
	111	is recognized as the multibyte character string terminator.
	112	Null bytes are not permitted within multibyte characters.
	113	.Pp
3d9156a7 A	114	The C library provides the following functions for dealing with
	115	multibyte characters:
	116	.Bl -column "Description"
	117	.It Sy "Function Description"
	118	.It Xr mblen 3 Ta "get number of bytes in a character"
	119	.It Xr mbrlen 3 Ta "get number of bytes in a character (restartable)"
	120	.It Xr mbrtowc 3 Ta "convert a character to a wide-character code (restartable)"
	121	.It Xr mbsrtowcs 3 Ta "convert a character string to a wide-character string (restartable)"
	122	.It Xr mbstowcs 3 Ta "convert a character string to a wide-character string"
	123	.It Xr mbtowc 3 Ta "convert a character to a wide-character code"
	124	.It Xr wcrtomb 3 Ta "convert a wide-character code to a character (restartable)"
	125	.It Xr wcstombs 3 Ta "convert a wide-character string to a character string"
	126	.It Xr wcsrtombs 3 Ta "convert a wide-character string to a character string (restartable)"
	127	.It Xr wctomb 3 Ta "convert a wide-character code to a character"
	128	.El
9385eb3d	129	.Sh SEE ALSO
3d9156a7	130	.Xr mklocale 1 ,
5b2abdfb	131	.Xr setlocale 3 ,
3d9156a7 A	132	.Xr stdio 3 ,
	133	.Xr big5 5 ,
	134	.Xr euc 5 ,
	135	.Xr gb18030 5 ,
	136	.Xr gb2312 5 ,
	137	.Xr gbk 5 ,
	138	.Xr mskanji 5 ,
9385eb3d	139	.Xr utf8 5
5b2abdfb	140	.Sh STANDARDS
3d9156a7 A	141	These functions conform to
3d9156a7 A	142	.St -isoC-99 .