stdlib/mblen.c

   1 /* Copyright (C) 1991, 1997, 1998, 1999, 2000 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #include <wchar.h>
  22 #include <gconv.h>
  23 #include <wcsmbs/wcsmbsload.h>
  24
  25
  26 /* Internal state.  */
  27 static mbstate_t state;
  28
  29 /* Return the length of the multibyte character (if there is one)
  30    at S which is no longer than N characters.
  31    The ISO C standard says that the `mblen' function must not change
  32    the state of the `mbtowc' function.  */
  33 int
  34 mblen (const char *s, size_t n)
  35 {
  36   int result;
  37
  38   /* If S is NULL the function has to return null or not null
  39      depending on the encoding having a state depending encoding or
  40      not.  */
  41   if (s == NULL)
  42     {
  43       /* Make sure we use the correct value.  */
  44       update_conversion_ptrs ();
  45
  46       /* Reset the state.  */
  47       memset (&state, '\0', sizeof state);
  48
  49       result = __wcsmbs_gconv_fcts.towc->__stateful;
  50     }
  51   else if (*s == '\0')
  52     /* According to the ISO C 89 standard this is the expected behaviour.  */
  53     result = 0;
  54   else
  55     {
  56       memset (&state, '\0', sizeof state);
  57
  58       result = __mbrtowc (NULL, s, n, &state);
  59
  60       /* The `mbrtowc' functions tell us more than we need.  Fold the -1
  61          and -2 result into -1.  */
  62       if (result < 0)
  63         result = -1;
  64     }
  65
  66   return result;
  67 }