stdlib/mblen.c

   1 /* Copyright (C) 1991, 1997 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <stdlib.h>
  20 #include <wchar.h>
  21
  22
  23 /* Return the length of the multibyte character (if there is one)
  24    at S which is no longer than N characters.
  25    The ISO C standard says that the `mblen' function must not change
  26    the global state.  */
  27 int
  28 mblen (const char *s, size_t n)
  29 {
  30   mbstate_t state;
  31   int result;
  32
  33   /* If S is NULL the function has to return null or not null
  34      depending on the encoding having a state depending encoding or
  35      not.  This is nonsense because any multibyte encoding has a
  36      state.  The ISO C amendment 1 corrects this while introducing the
  37      restartable functions.  We simply say here all encodings have a
  38      state.  */
  39   if (s == NULL)
  40     return 1;
  41
  42   state.count = 0;
  43   state.value = 0;
  44
  45   result = __mbrtowc (NULL, s, n, &state);
  46
  47   /* The `mbrtowc' functions tell us more than we need.  Fold the -1
  48      and -2 result into -1.  */
  49   if (result < 0)
  50     result = -1;
  51
  52   return result;
  53 }