1 | /* Copyright (C) 1991-2022 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 <string.h> |
19 | #include <memcopy.h> |
20 | |
21 | #undef strncmp |
22 | |
23 | #ifndef STRNCMP |
24 | #define STRNCMP strncmp |
25 | #endif |
26 | |
27 | /* Compare no more than N characters of S1 and S2, |
28 | returning less than, equal to or greater than zero |
29 | if S1 is lexicographically less than, equal to or |
30 | greater than S2. */ |
31 | int |
32 | STRNCMP (const char *s1, const char *s2, size_t n) |
33 | { |
34 | unsigned char c1 = '\0'; |
35 | unsigned char c2 = '\0'; |
36 | |
37 | if (n >= 4) |
38 | { |
39 | size_t n4 = n >> 2; |
40 | do |
41 | { |
42 | c1 = (unsigned char) *s1++; |
43 | c2 = (unsigned char) *s2++; |
44 | if (c1 == '\0' || c1 != c2) |
45 | return c1 - c2; |
46 | c1 = (unsigned char) *s1++; |
47 | c2 = (unsigned char) *s2++; |
48 | if (c1 == '\0' || c1 != c2) |
49 | return c1 - c2; |
50 | c1 = (unsigned char) *s1++; |
51 | c2 = (unsigned char) *s2++; |
52 | if (c1 == '\0' || c1 != c2) |
53 | return c1 - c2; |
54 | c1 = (unsigned char) *s1++; |
55 | c2 = (unsigned char) *s2++; |
56 | if (c1 == '\0' || c1 != c2) |
57 | return c1 - c2; |
58 | } while (--n4 > 0); |
59 | n &= 3; |
60 | } |
61 | |
62 | while (n > 0) |
63 | { |
64 | c1 = (unsigned char) *s1++; |
65 | c2 = (unsigned char) *s2++; |
66 | if (c1 == '\0' || c1 != c2) |
67 | return c1 - c2; |
68 | n--; |
69 | } |
70 | |
71 | return c1 - c2; |
72 | } |
73 | |
74 | libc_hidden_builtin_def (STRNCMP) |
75 | |