stdlib/mbtowc.c

   1 /* Copyright (C) 1991, 1992, 1995-1999, 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 /* Common state for all non-restartable conversion functions.  */
  27 mbstate_t __no_r_state attribute_hidden;
  28
  29 /* Convert the multibyte character at S, which is no longer
  30    than N characters, to its `wchar_t' representation, placing
  31    this n *PWC and returning its length.
  32
  33    Attention: this function should NEVER be intentionally used.
  34    The interface is completely stupid.  The state is shared between
  35    all conversion functions.  You should use instead the restartable
  36    version `mbrtowc'.  */
  37 int
  38 mbtowc (wchar_t *pwc, const char *s, size_t n)
  39 {
  40   int result;
  41
  42   /* If S is NULL the function has to return null or not null
  43      depending on the encoding having a state depending encoding or
  44      not.  */
  45   if (s == NULL)
  46     {
  47       const struct gconv_fcts *fcts;
  48
  49       /* Get the conversion functions.  */
  50       fcts = get_gconv_fcts (_NL_CURRENT_DATA (LC_CTYPE));
  51
  52       /* This is an extension in the Unix standard which does not directly
  53          violate ISO C.  */
  54       memset (&__no_r_state, '\0', sizeof __no_r_state);
  55
  56       result = fcts->towc->__stateful;
  57     }
  58   else if (*s == '\0')
  59     {
  60       if (pwc != NULL)
  61         *pwc = L'\0';
  62       result = 0;
  63     }
  64   else
  65     {
  66       result = __mbrtowc (pwc, s, n, &__no_r_state);
  67
  68       /* The `mbrtowc' functions tell us more than we need.  Fold the -1
  69          and -2 result into -1.  */
  70       if (result < 0)
  71         result = -1;
  72     }
  73
  74   return result;
  75 }