wcsmbs/c16rtomb.c

   1 /* Copyright (C) 2011-2024 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 <uchar.h>
  19 #include <wchar.h>
  20
  21
  22 /* This is the private state used if PS is NULL.  */
  23 static mbstate_t state;
  24
  25 size_t
  26 c16rtomb (char *s, char16_t c16, mbstate_t *ps)
  27 {
  28   wchar_t wc = c16;
  29
  30   if (ps == NULL)
  31     ps = &state;
  32
  33   if (s == NULL)
  34     {
  35       /* Reset any state relating to surrogate pairs.  */
  36       ps->__count &= 0x7fffffff;
  37       ps->__value.__wch = 0;
  38       wc = 0;
  39     }
  40
  41   if (ps->__count & 0x80000000)
  42     {
  43       /* The previous call passed in the first surrogate of a
  44          surrogate pair.  */
  45       ps->__count &= 0x7fffffff;
  46       if (wc >= 0xdc00 && wc < 0xe000)
  47         wc = (0x10000
  48               + ((ps->__value.__wch & 0x3ff) << 10)
  49               + (wc & 0x3ff));
  50       else
  51         /* This is not a low surrogate; ensure an EILSEQ error by
  52            trying to decode the high surrogate as a wide character on
  53            its own.  */
  54         wc = ps->__value.__wch;
  55       ps->__value.__wch = 0;
  56     }
  57   else if (wc >= 0xd800 && wc < 0xdc00)
  58     {
  59       /* The high part of a surrogate pair.  */
  60       ps->__count |= 0x80000000;
  61       ps->__value.__wch = wc;
  62       return 0;
  63     }
  64
  65   return wcrtomb (s, wc, ps);
  66 }