locale/FreeBSD/mbrlen.3

   1 .\" Copyright (c) 2002 Tim J. Robbins
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  25 .\" $FreeBSD: src/lib/libc/locale/mbrlen.3,v 1.6 2002/11/29 17:35:09 ru Exp $
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  27 .Dd November 11, 2002
  28 .Dt MBRLEN 3
  29 .Os
  30 .Sh NAME
  31 .Nm mbrlen
  32 .Nd "get number of bytes in a character (restartable)"
  33 .Sh LIBRARY
  34 .Lb libc
  35 .Sh SYNOPSIS
  36 .In wchar.h
  37 .Ft size_t
  38 .Fn mbrlen "const char * restrict s" "size_t n" "mbstate_t * restrict ps"
  39 .Sh DESCRIPTION
  40 The
  41 .Fn mbrlen
  42 function determines the number of bytes constituting the
  43 multibyte character sequence pointed to by
  44 .Fa s ,
  45 examining at most
  46 .Fa n
  47 bytes.
  48 .Pp
  49 The
  50 .Vt mbstate_t
  51 argument,
  52 .Fa ps ,
  53 is used to keep track of the shift state.
  54 If it is
  55 .Dv NULL ,
  56 .Fn mbrlen
  57 uses an internal, static
  58 .Vt mbstate_t
  59 object.
  60 .Pp
  61 It is equivalent to:
  62 .Pp
  63 .Dl "mbrtowc(NULL, s, n, ps);"
  64 .Pp
  65 Except that when
  66 .Fa ps
  67 is a
  68 .Dv NULL
  69 pointer,
  70 .Fn mbrlen
  71 uses its own static, internal
  72 .Vt mbstate_t
  73 object to keep track of the shift state.
  74 .Sh RETURN VALUES
  75 The
  76 .Fn mbrlen
  77 functions returns:
  78 .Bl -tag -width indent
  79 .It 0
  80 The first
  81 .Fa n
  82 or fewer bytes of
  83 .Fa s
  84 represent the null wide character
  85 .Pq Li "L'\e0'" .
  86 .It >0
  87 The first
  88 .Fa n
  89 or fewer bytes of
  90 .Fa s
  91 represent a valid character,
  92 .Fn mbrtowc
  93 returns the length (in bytes) of the multibyte sequence.
  94 .It Po Vt size_t Pc Ns \-2
  95 The first
  96 .Fa n
  97 bytes of
  98 .Fa s
  99 are an incomplete multibyte sequence.
 100 .It Po Vt size_t Pc Ns \-1
 101 The byte sequence pointed to by
 102 .Fa s
 103 is an invalid multibyte sequence.
 104 .El
 105 .Sh EXAMPLES
 106 A function which calculates the number of characters in a multibyte
 107 character string:
 108 .Bd -literal -offset indent
 109 size_t
 110 nchars(const char *s)
 111 {
 112         size_t charlen, chars;
 113         mbstate_t mbs;
 114
 115         chars = 0;
 116         memset(&mbs, 0, sizeof(mbs));
 117         while ((charlen = mbrlen(s, MB_CUR_MAX, &mbs)) != 0 &&
 118             charlen != (size_t)-1 && charlen != (size_t)-2) {
 119                 s += charlen;
 120                 chars++;
 121         }
 122
 123         return (chars);
 124 }
 125 .Ed
 126 .Sh ERRORS
 127 The
 128 .Fn mbrlen
 129 function will fail if:
 130 .Bl -tag -width Er
 131 .\".It Bq Er EINVAL
 132 .\"Invalid argument.
 133 .It Bq Er EILSEQ
 134 An invalid multibyte sequence was detected.
 135 .El
 136 .Sh SEE ALSO
 137 .Xr mblen 3 ,
 138 .Xr mbrtowc 3
 139 .Sh STANDARDS
 140 The
 141 .Fn mbrlen
 142 function conforms to
 143 .St -isoC-99 .
 144 .Sh BUGS
 145 The current implementation does not support shift states.