stdlib/mblen.c

   1 /* Copyright (C) 1991, 1997, 1998 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 #include <gconv.h>
  22 #include <wcsmbs/wcsmbsload.h>
  23
  24
  25 /* Return the length of the multibyte character (if there is one)
  26    at S which is no longer than N characters.
  27    The ISO C standard says that the `mblen' function must not change
  28    the global state.  */
  29 int
  30 mblen (const char *s, size_t n)
  31 {
  32   mbstate_t state;
  33   int result;
  34
  35   /* If S is NULL the function has to return null or not null
  36      depending on the encoding having a state depending encoding or
  37      not.  */
  38   if (s == NULL)
  39     {
  40       /* Make sure we use the correct value.  */
  41       update_conversion_ptrs ();
  42
  43       result = __wcsmbs_gconv_fcts.towc->stateful;
  44     }
  45   else if (*s == '\0')
  46     /* According to the ISO C 89 standard this is the expected behaviour.
  47        Idiotic, but true.  */
  48     result = 0;
  49   else
  50     {
  51       state.count = 0;
  52       state.value = 0;
  53
  54       result = __mbrtowc (NULL, s, n, &state);
  55
  56       /* The `mbrtowc' functions tell us more than we need.  Fold the -1
  57          and -2 result into -1.  */
  58       if (result < 0)
  59         result = -1;
  60     }
  61
  62   return result;
  63 }