1 /* Copyright (C) 1991, 1996, 1997, 2003 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 <http://www.gnu.org/licenses/>. */
17
18 #include <string.h>
19 #include "memcopy.h"
20
21 /* Compare no more than N characters of S1 and S2,
22 returning less than, equal to or greater than zero
23 if S1 is lexicographically less than, equal to or
24 greater than S2. */
strncmp(const char * s1,const char * s2,size_t n)25 int strncmp (const char *s1, const char *s2, size_t n)
26 {
27 unsigned reg_char c1 = '\0';
28 unsigned reg_char c2 = '\0';
29
30 if (n >= 4)
31 {
32 size_t n4 = n >> 2;
33 do
34 {
35 c1 = (unsigned char) *s1++;
36 c2 = (unsigned char) *s2++;
37 if (c1 == '\0' || c1 != c2)
38 return c1 - c2;
39 c1 = (unsigned char) *s1++;
40 c2 = (unsigned char) *s2++;
41 if (c1 == '\0' || c1 != c2)
42 return c1 - c2;
43 c1 = (unsigned char) *s1++;
44 c2 = (unsigned char) *s2++;
45 if (c1 == '\0' || c1 != c2)
46 return c1 - c2;
47 c1 = (unsigned char) *s1++;
48 c2 = (unsigned char) *s2++;
49 if (c1 == '\0' || c1 != c2)
50 return c1 - c2;
51 } while (--n4 > 0);
52 n &= 3;
53 }
54
55 while (n > 0)
56 {
57 c1 = (unsigned char) *s1++;
58 c2 = (unsigned char) *s2++;
59 if (c1 == '\0' || c1 != c2)
60 return c1 - c2;
61 n--;
62 }
63
64 return c1 - c2;
65 }
66 libc_hidden_weak(strncmp)
67