1/* Compare UTF-16 strings.
2   Copyright (C) 1999, 2002, 2006, 2009-2010 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 <http://www.gnu.org/licenses/>.  */
17
18#include <config.h>
19
20/* Specification.  */
21#include "unistr.h"
22
23int
24u16_strncmp (const uint16_t *s1, const uint16_t *s2, size_t n)
25{
26  /* Note that the UTF-16 encoding does NOT preserve lexicographic order.
27     Namely, if uc1 is a 16-bit character and [uc2a,uc2b] is a surrogate pair,
28     we must enforce uc1 < [uc2a,uc2b], even if uc1 > uc2a.  */
29  for (; n > 0;)
30    {
31      uint16_t c1 = *s1++;
32      uint16_t c2 = *s2++;
33      if (c1 != 0 && c1 == c2)
34        {
35          n--;
36          continue;
37        }
38      if (c1 < 0xd800 || c1 >= 0xe000)
39        {
40          if (!(c2 < 0xd800 || c2 >= 0xe000))
41            /* c2 is a surrogate, but c1 is not.  */
42            return -1;
43        }
44      else
45        {
46          if (c2 < 0xd800 || c2 >= 0xe000)
47            /* c1 is a surrogate, but c2 is not.  */
48            return 1;
49        }
50      return (int)c1 - (int)c2;
51      /* > 0 if c1 > c2, < 0 if c1 < c2, = 0 if c1 and c2 are both 0. */
52    }
53  return 0;
54}
55