locale/FreeBSD/multibyte.3

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  36 .\"     @(#)multibyte.3 8.1 (Berkeley) 6/4/93
  37 .\" $FreeBSD: src/lib/libc/locale/multibyte.3,v 1.27 2004/10/17 02:29:15 tjr Exp $
  38 .\"
  39 .Dd April 8, 2004
  40 .Dt MULTIBYTE 3
  41 .Os
  42 .Sh NAME
  43 .Nm multibyte
  44 .Nd multibyte and wide character manipulation functions
  45 .Sh LIBRARY
  46 .Lb libc
  47 .Sh SYNOPSIS
  48 .In limits.h
  49 .In stdlib.h
  50 .In wchar.h
  51 .Sh DESCRIPTION
  52 The basic elements of some written natural languages, such as Chinese,
  53 cannot be represented uniquely with single C
  54 .Vt char Ns s .
  55 The C standard supports two different ways of dealing with
  56 extended natural language encodings:
  57 wide characters and
  58 multibyte characters.
  59 Wide characters are an internal representation
  60 which allows each basic element to map
  61 to a single object of type
  62 .Vt wchar_t .
  63 Multibyte characters are used for input and output
  64 and code each basic element as a sequence of C
  65 .Vt char Ns s .
  66 Individual basic elements may map into one or more
  67 (up to
  68 .Dv MB_LEN_MAX )
  69 bytes in a multibyte character.
  70 .Pp
  71 The current locale
  72 .Pq Xr setlocale 3
  73 governs the interpretation of wide and multibyte characters.
  74 The locale category
  75 .Dv LC_CTYPE
  76 specifically controls this interpretation.
  77 The
  78 .Vt wchar_t
  79 type is wide enough to hold the largest value
  80 in the wide character representations for all locales.
  81 .Pp
  82 Multibyte strings may contain
  83 .Sq shift
  84 indicators to switch to and from
  85 particular modes within the given representation.
  86 If explicit bytes are used to signal shifting,
  87 these are not recognized as separate characters
  88 but are lumped with a neighboring character.
  89 There is always a distinguished
  90 .Sq initial
  91 shift state.
  92 Some functions (e.g.,
  93 .Xr mblen 3 ,
  94 .Xr mbtowc 3
  95 and
  96 .Xr wctomb 3 )
  97 maintain static shift state internally, whereas
  98 others store it in an
  99 .Vt mbstate_t
 100 object passed by the caller.
 101 Shift states are undefined after a call to
 102 .Xr setlocale 3
 103 with the
 104 .Dv LC_CTYPE
 105 or
 106 .Dv LC_ALL
 107 categories.
 108 .Pp
 109 For convenience in processing,
 110 the wide character with value 0
 111 (the null wide character)
 112 is recognized as the wide character string terminator,
 113 and the character with value 0
 114 (the null byte)
 115 is recognized as the multibyte character string terminator.
 116 Null bytes are not permitted within multibyte characters.
 117 .Pp
 118 The C library provides the following functions for dealing with
 119 multibyte characters:
 120 .Bl -column "Description"
 121 .It Sy "Function        Description"
 122 .It Xr mblen 3 Ta "get number of bytes in a character"
 123 .It Xr mbrlen 3 Ta "get number of bytes in a character (restartable)"
 124 .It Xr mbrtowc 3 Ta "convert a character to a wide-character code (restartable)"
 125 .It Xr mbsrtowcs 3 Ta "convert a character string to a wide-character string (restartable)"
 126 .It Xr mbstowcs 3 Ta "convert a character string to a wide-character string"
 127 .It Xr mbtowc 3 Ta "convert a character to a wide-character code"
 128 .It Xr wcrtomb 3 Ta "convert a wide-character code to a character (restartable)"
 129 .It Xr wcstombs 3 Ta "convert a wide-character string to a character string"
 130 .It Xr wcsrtombs 3 Ta "convert a wide-character string to a character string (restartable)"
 131 .It Xr wctomb 3 Ta "convert a wide-character code to a character"
 132 .El
 133 .Sh SEE ALSO
 134 .Xr mklocale 1 ,
 135 .Xr setlocale 3 ,
 136 .Xr stdio 3 ,
 137 .Xr big5 5 ,
 138 .Xr euc 5 ,
 139 .Xr gb18030 5 ,
 140 .Xr gb2312 5 ,
 141 .Xr gbk 5 ,
 142 .Xr mskanji 5 ,
 143 .Xr utf8 5
 144 .Sh STANDARDS
 145 These functions conform to
 146 .St -isoC-99 .