1/* Copyright (C) 1995-2022 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 <wchar.h>
19
20#ifndef WCSNCMP
21# define WCSNCMP wcsncmp
22#endif
23
24/* Compare no more than N characters of S1 and S2,
25 returning less than, equal to or greater than zero
26 if S1 is lexicographically less than, equal to or
27 greater than S2. */
28int
29WCSNCMP (const wchar_t *s1, const wchar_t *s2, size_t n)
30{
31 wchar_t c1 = L'\0';
32 wchar_t c2 = L'\0';
33
34 if (n >= 4)
35 {
36 size_t n4 = n >> 2;
37 do
38 {
39 c1 = *s1++;
40 c2 = *s2++;
41 if (c1 == L'\0' || c1 != c2)
42 return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
43 c1 = *s1++;
44 c2 = *s2++;
45 if (c1 == L'\0' || c1 != c2)
46 return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
47 c1 = *s1++;
48 c2 = *s2++;
49 if (c1 == L'\0' || c1 != c2)
50 return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
51 c1 = *s1++;
52 c2 = *s2++;
53 if (c1 == L'\0' || c1 != c2)
54 return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
55 } while (--n4 > 0);
56 n &= 3;
57 }
58
59 while (n > 0)
60 {
61 c1 = *s1++;
62 c2 = *s2++;
63 if (c1 == L'\0' || c1 != c2)
64 return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
65 n--;
66 }
67
68 return 0;
69}
70

source code of glibc/wcsmbs/wcsncmp.c