stdlib/mblen.c

   1 /* Copyright (C) 1991,1997,1998,1999,2000,2002 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       const struct gconv_fcts *fcts;
  44
  45       /* Get the conversion functions.  */
  46       fcts = get_gconv_fcts (_NL_CURRENT_DATA (LC_CTYPE));
  47
  48       /* Reset the state.  */
  49       memset (&state, '\0', sizeof state);
  50
  51       result = fcts->towc->__stateful;
  52     }
  53   else if (*s == '\0')
  54     /* According to the ISO C 89 standard this is the expected behaviour.  */
  55     result = 0;
  56   else
  57     {
  58       memset (&state, '\0', sizeof state);
  59
  60       result = __mbrtowc (NULL, s, n, &state);
  61
  62       /* The `mbrtowc' functions tell us more than we need.  Fold the -1
  63          and -2 result into -1.  */
  64       if (result < 0)
  65         result = -1;
  66     }
  67
  68   return result;
  69 }