stdlib/mbtowc.c

   1 /* Copyright (C) 1991, 92, 95, 96, 97, 98, 99 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 <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;
  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       /* Make sure we use the correct value.  */
  48       update_conversion_ptrs ();
  49
  50       /* This is an extension in the Unix standard which does not directly
  51          violate ISO C.  */
  52       memset (&__no_r_state, '\0', sizeof __no_r_state);
  53
  54       result = __wcsmbs_gconv_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, &__no_r_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 }