stdlib/mbtowc.c

   1 /* Copyright (C) 1991, 1992, 1995-1999, 2002, 2008
   2    Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  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 /* Convert the multibyte character at S, which is no longer
  27    than N characters, to its `wchar_t' representation, placing
  28    this n *PWC and returning its length.
  29
  30    Attention: this function should NEVER be intentionally used.
  31    The interface is completely stupid.  The state is shared between
  32    all conversion functions.  You should use instead the restartable
  33    version `mbrtowc'.  */
  34 int
  35 mbtowc (wchar_t *pwc, const char *s, size_t n)
  36 {
  37   int result;
  38   static mbstate_t state;
  39
  40   /* If S is NULL the function has to return null or not null
  41      depending on the encoding having a state depending encoding or
  42      not.  */
  43   if (s == NULL)
  44     {
  45       const struct gconv_fcts *fcts;
  46
  47       /* Get the conversion functions.  */
  48       fcts = get_gconv_fcts (_NL_CURRENT_DATA (LC_CTYPE));
  49
  50       /* This is an extension in the Unix standard which does not directly
  51          violate ISO C.  */
  52       memset (&state, '\0', sizeof state);
  53
  54       result = fcts->towc->__stateful;
  55     }
  56   else if (*s == '\0')
  57     {
  58       if (pwc != NULL)
  59         *pwc = L'\0';
  60       result = 0;
  61     }
  62   else
  63     {
  64       result = __mbrtowc (pwc, s, n, &state);
  65
  66       /* The `mbrtowc' functions tell us more than we need.  Fold the -1
  67          and -2 result into -1.  */
  68       if (result < 0)
  69         result = -1;
  70     }
  71
  72   return result;
  73 }