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 size_t num = n;
40
41 while (num >= 8) { /* 8, compare size, the number of chars of one uint64_t data */
42 if (*(const uint64_t *)(s1) != *(const uint64_t *)(s2)) {
43 goto L8_byte_diff;
44 }
45 s1 += 8; /* 8, compare size, the number of chars of one uint64_t data */
46 s2 += 8; /* 8, compare size, the number of chars of one uint64_t data */
47 num -= 8; /* 8, compare size, the number of chars of one uint64_t data */
48 }
49 if (num == 0) {
50 return 0;
51 }
52
53 /* L4_byte_cmp */
54 if (num >= 4) { /* 4, compare size, the number of chars of one uint32_t data */
55 if (*(const uint32_t *)(s1) != *(const uint32_t *)(s2)) {
56 goto L4_byte_diff;
57 }
58 s1 += 4; /* 4, compare size, the number of chars of one uint32_t data */
59 s2 += 4; /* 4, compare size, the number of chars of one uint32_t data */
60 num -= 4; /* 4, compare size, the number of chars of one uint32_t data */
61 }
62 if (num == 0) {
63 return 0;
64 }
65 L4_byte_diff:
66 for (; num && (*s1 == *s2); num--, s1++, s2++) {
67 }
68 return num ? *s1 - *s2 : 0;
69
70 L8_byte_diff:
71 if (*(const uint32_t *)(s1) != *(const uint32_t *)(s2)) {
72 goto L4_byte_diff;
73 }
74 s1 += 4; /* 4, compare size, the number of chars of one uint32_t data */
75 s2 += 4; /* 4, compare size, the number of chars of one uint32_t data */
76 num -= 4; /* 4, compare size, the number of chars of one uint32_t data */
77 goto L4_byte_diff;
78 }