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1 | //----------------------------------------------------------------------------- | |
2 | // This code is licensed to you under the terms of the GNU GPL, version 2 or, | |
3 | // at your option, any later version. See the LICENSE.txt file for the text of | |
4 | // the license. | |
5 | //----------------------------------------------------------------------------- | |
6 | // Generic CRC calculation code. | |
7 | //----------------------------------------------------------------------------- | |
8 | #include "crc.h" | |
9 | #include "util.h" | |
10 | #include <stdio.h> | |
11 | #include <stdint.h> | |
12 | #include <stddef.h> | |
13 | ||
14 | void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor) | |
15 | { | |
16 | crc->order = order; | |
17 | crc->polynom = polynom; | |
18 | crc->initial_value = initial_value; | |
19 | crc->final_xor = final_xor; | |
20 | crc->mask = (1L<<order)-1; | |
21 | crc_clear(crc); | |
22 | } | |
23 | ||
24 | void crc_update(crc_t *crc, uint32_t data, int data_width) | |
25 | { | |
26 | for( int i=0; i < data_width; i++) { | |
27 | int oldstate = crc->state; | |
28 | crc->state = crc->state >> 1; | |
29 | if( (oldstate^data) & 1 ) { | |
30 | crc->state ^= crc->polynom; | |
31 | } | |
32 | data >>= 1; | |
33 | } | |
34 | } | |
35 | ||
36 | void crc_clear(crc_t *crc) | |
37 | { | |
38 | crc->state = crc->initial_value & crc->mask; | |
39 | } | |
40 | ||
41 | uint32_t crc_finish(crc_t *crc) | |
42 | { | |
43 | return ( crc->state ^ crc->final_xor ) & crc->mask; | |
44 | } | |
45 | ||
46 | //credits to iceman | |
47 | uint32_t CRC8Maxim(uint8_t *buff, size_t size) | |
48 | { | |
49 | crc_t crc; | |
50 | crc_init(&crc, 9, 0x8c, 0x00, 0x00); | |
51 | crc_clear(&crc); | |
52 | ||
53 | for (size_t i=0; i < size; ++i) | |
54 | crc_update(&crc, buff[i], 8); | |
55 | ||
56 | return crc_finish(&crc); | |
57 | } | |
58 | ||
59 | uint32_t CRC8Legic(uint8_t *buff, size_t size) { | |
60 | ||
61 | // Poly 0x63, reversed poly 0xC6, Init 0x55, Final 0x00 | |
62 | crc_t crc; | |
63 | crc_init(&crc, 8, 0xC6, 0x55, 0); | |
64 | crc_clear(&crc); | |
65 | ||
66 | for ( int i = 0; i < size; ++i) | |
67 | crc_update(&crc, buff[i], 8); | |
68 | return SwapBits(crc_finish(&crc), 8); | |
69 | } | |
70 | ||
71 | uint32_t SwapBits(uint32_t value, int nrbits) { | |
72 | uint32_t newvalue = 0; | |
73 | for(int i = 0; i < nrbits; i++) { | |
74 | newvalue ^= ((value >> i) & 1) << (nrbits - 1 - i); | |
75 | } | |
76 | return newvalue; | |
77 | } |