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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <stdlib.h>
  21 #include <string.h>
  22 #include <wchar.h>
  23 #include <gconv.h>
  24 #include <wcsmbs/wcsmbsload.h>
  25
  26
  27 /* Convert the multibyte character at S, which is no longer
  28    than N characters, to its `wchar_t' representation, placing
  29    this n *PWC and returning its length.
  30
  31    Attention: this function should NEVER be intentionally used.
  32    The interface is completely stupid.  The state is shared between
  33    all conversion functions.  You should use instead the restartable
  34    version `mbrtowc'.  */
  35 int
  36 mbtowc (wchar_t *pwc, const char *s, size_t n)
  37 {
  38   int result;
  39   static mbstate_t state;
  40
  41   /* If S is NULL the function has to return null or not null
  42      depending on the encoding having a state depending encoding or
  43      not.  */
  44   if (s == NULL)
  45     {
  46       const struct gconv_fcts *fcts;
  47
  48       /* Get the conversion functions.  */
  49       fcts = get_gconv_fcts (_NL_CURRENT_DATA (LC_CTYPE));
  50
  51       /* This is an extension in the Unix standard which does not directly
  52          violate ISO C.  */
  53       memset (&state, '\0', sizeof state);
  54
  55       result = fcts->towc->__stateful;
  56     }
  57   else if (*s == '\0')
  58     {
  59       if (pwc != NULL)
  60         *pwc = L'\0';
  61       result = 0;
  62     }
  63   else
  64     {
  65       result = __mbrtowc (pwc, s, n, &state);
  66
  67       /* The `mbrtowc' functions tell us more than we need.  Fold the -1
  68          and -2 result into -1.  */
  69       if (result < 0)
  70         result = -1;
  71     }
  72
  73   return result;
  74 }