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bc0b3a1800
Instead of just deleting it, turn the original page into a general overview of the multibyte character conversion functions, somewhat similar to stdio(3).
153 lines
5.2 KiB
Groff
153 lines
5.2 KiB
Groff
.\" Copyright (c) 2002, 2003 Tim J. Robbins. All rights reserved.
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.\" Copyright (c) 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Donn Seeley of BSDI.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)multibyte.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd December 7, 2003
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.Dt MULTIBYTE 3
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.Os
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.Sh NAME
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.Nm multibyte
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.Nd multibyte and wide character manipulation functions
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In limits.h
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.In stdlib.h
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.In wchar.h
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.Sh DESCRIPTION
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The basic elements of some written natural languages, such as Chinese,
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cannot be represented uniquely with single C
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.Va char Ns s .
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The C standard supports two different ways of dealing with
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extended natural language encodings:
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wide characters and
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multibyte characters.
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Wide characters are an internal representation
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which allows each basic element to map
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to a single object of type
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.Va wchar_t .
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Multibyte characters are used for input and output
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and code each basic element as a sequence of C
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.Va char Ns s .
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Individual basic elements may map into one or more
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(up to
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.Dv MB_LEN_MAX )
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bytes in a multibyte character.
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.Pp
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The current locale
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.Pq Xr setlocale 3
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governs the interpretation of wide and multibyte characters.
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The locale category
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.Dv LC_CTYPE
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specifically controls this interpretation.
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The
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.Va wchar_t
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type is wide enough to hold the largest value
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in the wide character representations for all locales.
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.Pp
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Multibyte strings may contain
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.Sq shift
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indicators to switch to and from
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particular modes within the given representation.
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If explicit bytes are used to signal shifting,
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these are not recognized as separate characters
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but are lumped with a neighboring character.
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There is always a distinguished
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.Sq initial
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shift state.
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Some functions (e.g.
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.Fn mblen ,
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.Fn mbtowc
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and
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.Fn wctomb )
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maintain static shift state internally, whereas
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others store in an
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.Vt mbstate_t
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object passed by the caller.
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Shift states are undefined after a call to
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.Fn setlocale
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with the
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.Dv LC_CTYPE
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or
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.Dv LC_ALL
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categories.
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.Pp
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For convenience in processing,
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the wide character with value 0
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(the null wide character)
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is recognized as the wide character string terminator,
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and the character with value 0
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(the null byte)
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is recognized as the multibyte character string terminator.
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Null bytes are not permitted within multibyte characters.
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.Pp
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The C library provides the following functions for dealing with
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multibyte characters:
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.Bl -column "Description"
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.It Sy "Function Description"
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.It "mblen get number of bytes in a character"
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.It "mbrlen get number of bytes in a character (restartable)"
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.It "mbrtowc convert a character to a wide-character code (restartable)"
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.It "mbsrtowcs convert a character string to a wide-character string (restartable)"
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.It "mbstowcs convert a character string to a wide-character string"
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.It "mbtowc convert a character to a wide-character code"
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.It "wcrtomb convert a wide-character code to a character (restartable)"
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.It "wcstombs convert a wide-character string to a character string"
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.It "wcsrtombs convert a wide-character string to a character string (restartable)"
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.It "wctomb convert a wide-character code to a character"
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.El
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.Sh SEE ALSO
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.Xr mklocale 1 ,
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.Xr stdio 3 ,
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.Xr setlocale 3 ,
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.Xr big5 5 ,
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.Xr euc 5 ,
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.Xr gb18030 5 ,
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.Xr gb2312 5 ,
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.Xr gbk 5 ,
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.Xr mskanji 5 ,
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.Xr utf2 5 ,
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.Xr utf8 5
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.Sh STANDARDS
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These functions conform to
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.St -isoC
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and
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.St -isoC-99
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as documented in their individual manual pages.
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.Sh BUGS
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The current implementation does not support shift states.
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