stdlib/mblen.c

   1 /* Copyright (C) 1991-2022 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 /* Internal state.  */
  26 static mbstate_t state;
  27
  28 /* Return the length of the multibyte character (if there is one)
  29    at S which is no longer than N characters.
  30    The ISO C standard says that the `mblen' function must not change
  31    the state of the `mbtowc' function.  */
  32 int
  33 mblen (const char *s, size_t n)
  34 {
  35   int result;
  36
  37   /* If S is NULL the function has to return null or not null
  38      depending on the encoding having a state depending encoding or
  39      not.  */
  40   if (s == NULL)
  41     {
  42       const struct gconv_fcts *fcts;
  43
  44       /* Get the conversion functions.  */
  45       fcts = get_gconv_fcts (_NL_CURRENT_DATA (LC_CTYPE));
  46
  47       /* Reset the state.  */
  48       memset (&state, '\0', sizeof state);
  49
  50       result = fcts->towc->__stateful;
  51     }
  52   else if (*s == '\0')
  53     /* According to the ISO C 89 standard this is the expected behaviour.  */
  54     result = 0;
  55   else
  56     {
  57       memset (&state, '\0', sizeof state);
  58
  59       result = __mbrtowc (NULL, s, n, &state);
  60
  61       /* The `mbrtowc' functions tell us more than we need.  Fold the -1
  62          and -2 result into -1.  */
  63       if (result < 0)
  64         result = -1;
  65     }
  66
  67   return result;
  68 }