1 /*
2 * Copyright (c) 2021-2021 Huawei Device Co., Ltd. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without modification,
5 * are permitted provided that the following conditions are met:
6 *
7 * 1. Redistributions of source code must retain the above copyright notice, this list of
8 * conditions and the following disclaimer.
9 *
10 * 2. Redistributions in binary form must reproduce the above copyright notice, this list
11 * of conditions and the following disclaimer in the documentation and/or other materials
12 * provided with the distribution.
13 *
14 * 3. Neither the name of the copyright holder nor the names of its contributors may be used
15 * to endorse or promote products derived from this software without specific prior written
16 * permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
20 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
21 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
22 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
23 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
24 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
25 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
26 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
27 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
28 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31 #include <string.h>
32 #include <stdint.h>
33
memcmp(const void * str1,const void * str2,size_t n)34 int memcmp(const void *str1, const void *str2, size_t n)
35 {
36
37 const unsigned char *s1 = str1;
38 const unsigned char *s2 = str2;
39
40 while (n >= 8) {
41 if (*(const uint64_t *)(s1) != *(const uint64_t *)(s2)) {
42 goto L8_byte_diff;
43 }
44 s1 += 8;
45 s2 += 8;
46 n -= 8;
47 }
48 if (n == 0) return 0;
49
50
51 /* L4_byte_cmp */
52 if (n >= 4) {
53 if (*(const uint32_t *)(s1) != *(const uint32_t *)(s2)) {
54 goto L4_byte_diff;
55 }
56 s1 += 4;
57 s2 += 4;
58 n -= 4;
59 }
60 if (n == 0) return 0;
61
62 L4_byte_diff:
63 for (; n && (*s1 == *s2); n--, s1++, s2++);
64 return n ? *s1 - *s2 : 0;
65
66 L8_byte_diff:
67 if (*(const uint32_t *)(s1) != *(const uint32_t *)(s2)) {
68 goto L4_byte_diff;
69 }
70 s1 += 4;
71 s2 += 4;
72 n -= 4;
73 goto L4_byte_diff;
74 }