stdlib/mbtowc.c

   1 /* Copyright (C) 1991-2020 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, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <stdlib.h>
  19 #include <string.h>
  20 #include <wchar.h>
  21 #include <gconv.h>
  22 #include <wcsmbs/wcsmbsload.h>
  23
  24
  25 /* Convert the multibyte character at S, which is no longer
  26    than N characters, to its `wchar_t' representation, placing
  27    this n *PWC and returning its length.
  28
  29    Attention: this function should NEVER be intentionally used.
  30    The interface is completely stupid.  The state is shared between
  31    all conversion functions.  You should use instead the restartable
  32    version `mbrtowc'.  */
  33 int
  34 mbtowc (wchar_t *pwc, const char *s, size_t n)
  35 {
  36   int result;
  37   static mbstate_t state;
  38
  39   /* If S is NULL the function has to return null or not null
  40      depending on the encoding having a state depending encoding or
  41      not.  */
  42   if (s == NULL)
  43     {
  44       const struct gconv_fcts *fcts;
  45
  46       /* Get the conversion functions.  */
  47       fcts = get_gconv_fcts (_NL_CURRENT_DATA (LC_CTYPE));
  48
  49       /* This is an extension in the Unix standard which does not directly
  50          violate ISO C.  */
  51       memset (&state, '\0', sizeof state);
  52
  53       result = fcts->towc->__stateful;
  54     }
  55   else if (*s == '\0')
  56     {
  57       if (pwc != NULL)
  58         *pwc = L'\0';
  59       result = 0;
  60     }
  61   else
  62     {
  63       result = __mbrtowc (pwc, s, n, &state);
  64
  65       /* The `mbrtowc' functions tell us more than we need.  Fold the -1
  66          and -2 result into -1.  */
  67       if (result < 0)
  68         result = -1;
  69     }
  70
  71   return result;
  72 }