locale/FreeBSD/multibyte.3

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  32 .\"     @(#)multibyte.3 8.1 (Berkeley) 6/4/93
  33 .\" $FreeBSD: src/lib/libc/locale/multibyte.3,v 1.28 2007/01/09 00:28:00 imp Exp $
  34 .\"
  35 .Dd April 8, 2004
  36 .Dt MULTIBYTE 3
  37 .Os
  38 .Sh NAME
  39 .Nm multibyte
  40 .Nd multibyte and wide character manipulation functions
  41 .Sh LIBRARY
  42 .Lb libc
  43 .Sh SYNOPSIS
  44 .In limits.h
  45 .In stdlib.h
  46 .In wchar.h
  47 .Sh DESCRIPTION
  48 The basic elements of some written natural languages, such as Chinese,
  49 cannot be represented uniquely with single C
  50 .Vt char Ns s .
  51 The C standard supports two different ways of dealing with
  52 extended natural language encodings:
  53 wide characters and
  54 multibyte characters.
  55 Wide characters are an internal representation
  56 which allows each basic element to map
  57 to a single object of type
  58 .Vt wchar_t .
  59 Multibyte characters are used for input and output
  60 and code each basic element as a sequence of C
  61 .Vt char Ns s .
  62 Individual basic elements may map into one or more
  63 (up to
  64 .Dv MB_LEN_MAX )
  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
  74 .Vt wchar_t
  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.
  88 Some functions (e.g.,
  89 .Xr mblen 3 ,
  90 .Xr mbtowc 3
  91 and
  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
  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
 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
 129 .Sh SEE ALSO
 130 .Xr mklocale 1 ,
 131 .Xr setlocale 3 ,
 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 ,
 139 .Xr utf8 5
 140 .Sh STANDARDS
 141 These functions conform to
 142 .St -isoC-99 .