lib/unistr/u16-check.c

   1 /* Check UTF-16 string.
   2    Copyright (C) 2002, 2006-2007, 2009-2021 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2002.
   4
   5    This program is free software: you can redistribute it and/or modify it
   6    under the terms of the GNU Lesser General Public License as published
   7    by the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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 License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include "unistr.h"
  22
  23 const uint16_t *
  24 u16_check (const uint16_t *s, size_t n)
  25 {
  26   const uint16_t *s_end = s + n;
  27
  28   while (s < s_end)
  29     {
  30       /* Keep in sync with unistr.h and u16-mbtouc-aux.c.  */
  31       uint16_t c = *s;
  32
  33       if (c < 0xd800 || c >= 0xe000)
  34         {
  35           s++;
  36           continue;
  37         }
  38       if (c < 0xdc00)
  39         {
  40           if (s + 2 <= s_end
  41               && s[1] >= 0xdc00 && s[1] < 0xe000)
  42             {
  43               s += 2;
  44               continue;
  45             }
  46         }
  47       /* invalid or incomplete multibyte character */
  48       return s;
  49     }
  50   return NULL;
  51 }