wcsmbs/c16rtomb.c

   1 /* Copyright (C) 2011-2019 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
   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, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <uchar.h>
  20 #include <wchar.h>
  21
  22
  23 /* This is the private state used if PS is NULL.  */
  24 static mbstate_t state;
  25
  26 size_t
  27 c16rtomb (char *s, char16_t c16, mbstate_t *ps)
  28 {
  29   wchar_t wc = c16;
  30
  31   if (ps == NULL)
  32     ps = &state;
  33
  34   if (s == NULL)
  35     {
  36       /* Reset any state relating to surrogate pairs.  */
  37       ps->__count &= 0x7fffffff;
  38       ps->__value.__wch = 0;
  39       wc = 0;
  40     }
  41
  42   if (ps->__count & 0x80000000)
  43     {
  44       /* The previous call passed in the first surrogate of a
  45          surrogate pair.  */
  46       ps->__count &= 0x7fffffff;
  47       if (wc >= 0xdc00 && wc < 0xe000)
  48         wc = (0x10000
  49               + ((ps->__value.__wch & 0x3ff) << 10)
  50               + (wc & 0x3ff));
  51       else
  52         /* This is not a low surrogate; ensure an EILSEQ error by
  53            trying to decode the high surrogate as a wide character on
  54            its own.  */
  55         wc = ps->__value.__wch;
  56       ps->__value.__wch = 0;
  57     }
  58   else if (wc >= 0xd800 && wc < 0xdc00)
  59     {
  60       /* The high part of a surrogate pair.  */
  61       ps->__count |= 0x80000000;
  62       ps->__value.__wch = wc;
  63       return 0;
  64     }
  65
  66   return wcrtomb (s, wc, ps);
  67 }