locale/FreeBSD/mbrlen.3

   1 .\" Copyright (c) 2002-2004 Tim J. Robbins
   2 .\" All rights reserved.
   3 .\"
   4 .\" Redistribution and use in source and binary forms, with or without
   5 .\" modification, are permitted provided that the following conditions
   6 .\" are met:
   7 .\" 1. Redistributions of source code must retain the above copyright
   8 .\"    notice, this list of conditions and the following disclaimer.
   9 .\" 2. Redistributions in binary form must reproduce the above copyright
  10 .\"    notice, this list of conditions and the following disclaimer in the
  11 .\"    documentation and/or other materials provided with the distribution.
  12 .\"
  13 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  14 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  16 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  17 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  18 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  19 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  20 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  21 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  22 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  23 .\" SUCH DAMAGE.
  24 .\"
  25 .\" $FreeBSD: src/lib/libc/locale/mbrlen.3,v 1.8 2004/06/30 19:32:41 ru Exp $
  26 .\"
  27 .Dd April 7, 2004
  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 inspects at most
  43 .Fa n
  44 bytes pointed to by
  45 .Fa s
  46 to determine the number of bytes needed to complete the next
  47 multibyte character.
  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, which is initialized to the initial conversion state
  60 at program startup.
  61 .Pp
  62 It is equivalent to:
  63 .Pp
  64 .Dl "mbrtowc(NULL, s, n, ps);"
  65 .Pp
  66 Except that when
  67 .Fa ps
  68 is a
  69 .Dv NULL
  70 pointer,
  71 .Fn mbrlen
  72 uses its own static, internal
  73 .Vt mbstate_t
  74 object to keep track of the shift state.
  75 .Sh RETURN VALUES
  76 The
  77 .Fn mbrlen
  78 functions returns:
  79 .Bl -tag -width indent
  80 .It 0
  81 The next
  82 .Fa n
  83 or fewer bytes
  84 represent the null wide character
  85 .Pq Li "L'\e0'" .
  86 .It >0
  87 The next
  88 .Fa n
  89 or fewer bytes
  90 represent a valid character,
  91 .Fn mbrlen
  92 returns the number of bytes used to complete the multibyte character.
  93 .It Po Vt size_t Pc Ns \-2
  94 The next
  95 .Fa n
  96 contribute to, but do not complete, a valid multibyte character sequence,
  97 and all
  98 .Fa n
  99 bytes have been processed.
 100 .It Po Vt size_t Pc Ns \-1
 101 An encoding error has occurred.
 102 The next
 103 .Fa n
 104 or fewer bytes do not contribute to a valid multibyte character.
 105 .El
 106 .Sh EXAMPLES
 107 A function that calculates the number of characters in a multibyte
 108 character string:
 109 .Bd -literal -offset indent
 110 size_t
 111 nchars(const char *s)
 112 {
 113         size_t charlen, chars;
 114         mbstate_t mbs;
 115
 116         chars = 0;
 117         memset(&mbs, 0, sizeof(mbs));
 118         while ((charlen = mbrlen(s, MB_CUR_MAX, &mbs)) != 0 &&
 119             charlen != (size_t)-1 && charlen != (size_t)-2) {
 120                 s += charlen;
 121                 chars++;
 122         }
 123
 124         return (chars);
 125 }
 126 .Ed
 127 .Sh ERRORS
 128 The
 129 .Fn mbrlen
 130 function will fail if:
 131 .Bl -tag -width Er
 132 .It Bq Er EILSEQ
 133 An invalid multibyte sequence was detected.
 134 .It Bq Er EINVAL
 135 The conversion state is invalid.
 136 .El
 137 .Sh SEE ALSO
 138 .Xr mblen 3 ,
 139 .Xr mbrtowc 3 ,
 140 .Xr multibyte 3
 141 .Sh STANDARDS
 142 The
 143 .Fn mbrlen
 144 function conforms to
 145 .St -isoC-99 .