1/*
2 * CRC64 using the polynomial from ECMA-182
3 *
4 * This file is similar to xz_crc32.c. See the comments there.
5 *
6 * Authors: Lasse Collin <lasse.collin@tukaani.org>
7 *          Igor Pavlov <https://7-zip.org/>
8 *
9 * This file has been put into the public domain.
10 * You can do whatever you want with this file.
11 */
12
13#include "xz_private.h"
14
15#ifndef STATIC_RW_DATA
16#	define STATIC_RW_DATA static
17#endif
18
19STATIC_RW_DATA uint64_t xz_crc64_table[256];
20
21XZ_EXTERN void xz_crc64_init(void)
22{
23	/*
24	 * The ULL suffix is needed for -std=gnu89 compatibility
25	 * on 32-bit platforms.
26	 */
27	const uint64_t poly = 0xC96C5795D7870F42ULL;
28
29	uint32_t i;
30	uint32_t j;
31	uint64_t r;
32
33	for (i = 0; i < 256; ++i) {
34		r = i;
35		for (j = 0; j < 8; ++j)
36			r = (r >> 1) ^ (poly & ~((r & 1) - 1));
37
38		xz_crc64_table[i] = r;
39	}
40
41	return;
42}
43
44XZ_EXTERN uint64_t xz_crc64(const uint8_t *buf, size_t size, uint64_t crc)
45{
46	crc = ~crc;
47
48	while (size != 0) {
49		crc = xz_crc64_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
50		--size;
51	}
52
53	return ~crc;
54}
55