1 // SPDX-License-Identifier: 0BSD <<
2 <<
3 /* 1 /*
4 * CRC32 using the polynomial from IEEE-802.3 2 * CRC32 using the polynomial from IEEE-802.3
5 * 3 *
6 * Authors: Lasse Collin <lasse.collin@tukaani 4 * Authors: Lasse Collin <lasse.collin@tukaani.org>
7 * Igor Pavlov <https://7-zip.org/> 5 * Igor Pavlov <https://7-zip.org/>
>> 6 *
>> 7 * This file has been put into the public domain.
>> 8 * You can do whatever you want with this file.
8 */ 9 */
9 10
10 /* 11 /*
11 * This is not the fastest implementation, but 12 * This is not the fastest implementation, but it is pretty compact.
12 * The fastest versions of xz_crc32() on moder 13 * The fastest versions of xz_crc32() on modern CPUs without hardware
13 * accelerated CRC instruction are 3-5 times a 14 * accelerated CRC instruction are 3-5 times as fast as this version,
14 * but they are bigger and use more memory for 15 * but they are bigger and use more memory for the lookup table.
15 */ 16 */
16 17
17 #include "xz_private.h" 18 #include "xz_private.h"
18 19
19 /* 20 /*
20 * STATIC_RW_DATA is used in the pre-boot envi 21 * STATIC_RW_DATA is used in the pre-boot environment on some architectures.
21 * See <linux/decompress/mm.h> for details. 22 * See <linux/decompress/mm.h> for details.
22 */ 23 */
23 #ifndef STATIC_RW_DATA 24 #ifndef STATIC_RW_DATA
24 # define STATIC_RW_DATA static 25 # define STATIC_RW_DATA static
25 #endif 26 #endif
26 27
27 STATIC_RW_DATA uint32_t xz_crc32_table[256]; 28 STATIC_RW_DATA uint32_t xz_crc32_table[256];
28 29
29 void xz_crc32_init(void) !! 30 XZ_EXTERN void xz_crc32_init(void)
30 { 31 {
31 const uint32_t poly = 0xEDB88320; !! 32 const uint32_t poly = CRC32_POLY_LE;
32 33
33 uint32_t i; 34 uint32_t i;
34 uint32_t j; 35 uint32_t j;
35 uint32_t r; 36 uint32_t r;
36 37
37 for (i = 0; i < 256; ++i) { 38 for (i = 0; i < 256; ++i) {
38 r = i; 39 r = i;
39 for (j = 0; j < 8; ++j) 40 for (j = 0; j < 8; ++j)
40 r = (r >> 1) ^ (poly & 41 r = (r >> 1) ^ (poly & ~((r & 1) - 1));
41 42
42 xz_crc32_table[i] = r; 43 xz_crc32_table[i] = r;
43 } 44 }
44 45
45 return; 46 return;
46 } 47 }
47 48
48 uint32_t xz_crc32(const uint8_t *buf, size_t s !! 49 XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc)
49 { 50 {
50 crc = ~crc; 51 crc = ~crc;
51 52
52 while (size != 0) { 53 while (size != 0) {
53 crc = xz_crc32_table[*buf++ ^ 54 crc = xz_crc32_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
54 --size; 55 --size;
55 } 56 }
56 57
57 return ~crc; 58 return ~crc;
58 } 59 }
59 60
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