lib/unistr/u16-strmbtouc.c

   1 /* Look at first character in UTF-16 string.
   2    Copyright (C) 1999-2000, 2002, 2006-2007, 2009-2021 Free Software
   3    Foundation, Inc.
   4    Written by Bruno Haible <bruno@clisp.org>, 2002.
   5
   6    This program is free software: you can redistribute it and/or modify it
   7    under the terms of the GNU Lesser General Public License as published
   8    by the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public License
  17    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  18
  19 #include <config.h>
  20
  21 /* Specification.  */
  22 #include "unistr.h"
  23
  24 int
  25 u16_strmbtouc (ucs4_t *puc, const uint16_t *s)
  26 {
  27   /* Keep in sync with unistr.h and u16-mbtouc-aux.c.  */
  28   uint16_t c = *s;
  29
  30   if (c < 0xd800 || c >= 0xe000)
  31     {
  32       *puc = c;
  33       return (c != 0 ? 1 : 0);
  34     }
  35   if (c < 0xdc00)
  36     {
  37       if (s[1] >= 0xdc00 && s[1] < 0xe000)
  38         {
  39           *puc = 0x10000 + ((c - 0xd800) << 10) + (s[1] - 0xdc00);
  40           return 2;
  41         }
  42     }
  43   /* invalid or incomplete multibyte character */
  44   return -1;
  45 }