1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
/*********************************************************************
*
* Copyright (c) 2011-2013 Stephan Brumme. All rights reserved.
*
* This software is provided 'as-is', without any express or implied
* warranty. In no event will the authors be held liable for any damages
* arising from the use of this software.
*
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
*
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*
*********************************************************************/
/*
* http://create.stephan-brumme.com/crc32/
*/
#pragma once
#include <stdlib.h>
#include <stdint.h>
// define endianess and some integer data types
#if defined(_WIN32)
#define __LITTLE_ENDIAN 1234
#define __BIG_ENDIAN 4321
#define __BYTE_ORDER __LITTLE_ENDIAN
#else
// defines __BYTE_ORDER as __LITTLE_ENDIAN or __BIG_ENDIAN
#include <sys/param.h>
#endif
extern "C" const uint32_t
crc32c_8x256_table[8][256];
#if __BYTE_ORDER == __BIG_ENDIAN
// swap endianess
static inline uint32_t
swap(uint32_t x)
{
#if defined(__GNUC__) || defined(__clang__)
return __builtin_bswap32(x);
#else
return (x >> 24) |
((x >> 8) & 0x0000FF00) |
((x << 8) & 0x00FF0000) |
(x << 24);
#endif
}
#endif /* __BYTE_ORDER == __BIG_ENDIAN */
// compute CRC32C (Slicing-by-8 algorithm)
static inline uint32_t
crc32c_8bytes(const void *data, size_t length, uint32_t previousCrc32 = 0)
{
uint32_t crc = ~previousCrc32;
const uint32_t *current = (const uint32_t *)data;
// process eight bytes at once (Slicing-by-8)
while (length >= 8) {
#if __BYTE_ORDER == __BIG_ENDIAN
uint32_t one = *current++ ^ swap(crc);
uint32_t two = *current++;
crc = crc32c_8x256_table[0][ two & 0xFF] ^
crc32c_8x256_table[1][(two>> 8) & 0xFF] ^
crc32c_8x256_table[2][(two>>16) & 0xFF] ^
crc32c_8x256_table[3][ two>>24 ] ^
crc32c_8x256_table[4][ one & 0xFF] ^
crc32c_8x256_table[5][(one>> 8) & 0xFF] ^
crc32c_8x256_table[6][(one>>16) & 0xFF] ^
crc32c_8x256_table[7][ one>>24 ];
#else
uint32_t one = *current++ ^ crc;
uint32_t two = *current++;
crc = crc32c_8x256_table[0][ two>>24 ] ^
crc32c_8x256_table[1][(two>>16) & 0xFF] ^
crc32c_8x256_table[2][(two>> 8) & 0xFF] ^
crc32c_8x256_table[3][ two & 0xFF] ^
crc32c_8x256_table[4][ one>>24 ] ^
crc32c_8x256_table[5][(one>>16) & 0xFF] ^
crc32c_8x256_table[6][(one>> 8) & 0xFF] ^
crc32c_8x256_table[7][ one & 0xFF];
#endif
length -= 8;
}
const uint8_t *currentChar = (const uint8_t *)current;
// remaining 1 to 7 bytes (standard algorithm)
while (length-- > 0) {
crc = (crc >> 8) ^ crc32c_8x256_table[0][(crc & 0xFF) ^ *currentChar++];
}
return ~crc;
}
|
