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bd20f8f4 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//-----------------------------------------------------------------------------
3e134b4c 8// the Check value below in the comments is CRC of the string '123456789'
9//
68d9d60a 10#include "crc.h"
11
3e134b4c 12void crc_init_ref(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor, bool refin, bool refout) {
13 crc_init(crc, order, polynom, initial_value, final_xor);
14 crc->refin = refin;
15 crc->refout = refout;
16 crc_clear(crc);
17}
18
19void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor) {
68d9d60a 20 crc->order = order;
3e134b4c 21 crc->topbit = BITMASK( order-1 );
68d9d60a 22 crc->polynom = polynom;
23 crc->initial_value = initial_value;
24 crc->final_xor = final_xor;
25 crc->mask = (1L<<order)-1;
3e134b4c 26 crc->refin = FALSE;
27 crc->refout = FALSE;
68d9d60a 28 crc_clear(crc);
29}
30
3e134b4c 31void crc_clear(crc_t *crc) {
32 crc->state = crc->initial_value & crc->mask;
33 if (crc->refin)
34 crc->state = reflect(crc->state, crc->order);
35}
36
37void crc_update(crc_t *crc, uint32_t indata, int data_width){
38
39 //reflected
40 if (crc->refin) indata = reflect(indata, data_width);
41
42 // Bring the next byte into the remainder.
43 crc->state ^= indata << (crc->order - data_width);
44
45 for( uint8_t bit = data_width; bit > 0; --bit) {
46 // Try to divide the current data bit.
47 if (crc->state & crc->topbit)
48 crc->state = (crc->state << 1) ^ crc->polynom;
49 else
50 crc->state = (crc->state << 1);
68d9d60a 51 }
52}
53
3e134b4c 54uint32_t crc_finish(crc_t *crc) {
55 uint32_t val = crc->state;
56 if (crc->refout) val = reflect(val, crc->order);
57 return ( val ^ crc->final_xor ) & crc->mask;
68d9d60a 58}
59
3e134b4c 60/*
61static void print_crc(crc_t *crc) {
62 printf(" Order %d\n Poly %x\n Init %x\n Final %x\n Mask %x\n topbit %x\n RefIn %s\n RefOut %s\n State %x\n",
63 crc->order,
64 crc->polynom,
65 crc->initial_value,
66 crc->final_xor,
67 crc->mask,
68 crc->topbit,
69 (crc->refin) ? "TRUE":"FALSE",
70 (crc->refout) ? "TRUE":"FALSE",
71 crc->state
72 );
68d9d60a 73}
3e134b4c 74*/
73d04bb4 75
3e134b4c 76// width=8 poly=0x31 init=0x00 refin=true refout=true xorout=0x00 check=0xA1 name="CRC-8/MAXIM"
6bb7609c 77uint32_t CRC8Maxim(uint8_t *buff, size_t size) {
73d04bb4 78 crc_t crc;
3e134b4c 79 crc_init_ref(&crc, 8, 0x31, 0, 0, TRUE, TRUE);
80 for ( int i=0; i < size; ++i)
81 crc_update(&crc, buff[i], 8);
82 return crc_finish(&crc);
83}
84
73d04bb4 85
3e134b4c 86// width=4 poly=0xC, reversed poly=0x7 init=0x5 refin=true refout=true xorout=0x0000 check= name="CRC-4/LEGIC"
87// width=8 poly=0x63, reversed poly=0x8D init=0x55 refin=true refout=true xorout=0x0000 check=0xC6 name="CRC-8/LEGIC"
88// the CRC needs to be reversed before returned.
89uint32_t CRC8Legic(uint8_t *buff, size_t size) {
90 crc_t crc;
91 crc_init_ref(&crc, 8, 0x63, 0x55, 0, TRUE, TRUE);
92 for ( int i = 0; i < size; ++i)
73d04bb4 93 crc_update(&crc, buff[i], 8);
3e134b4c 94 return reflect(crc_finish(&crc), 8);
95}
ee4e2816 96
3e134b4c 97// This CRC-16 is used in Legic Advant systems.
98// width=8 poly=0xB400, reversed poly=0x init=depends refin=true refout=true xorout=0x0000 check= name="CRC-16/LEGIC"
99uint32_t CRC16Legic(uint8_t *buff, size_t size, uint8_t uidcrc) {
ee4e2816 100
3e134b4c 101 #define CRC16_POLY_LEGIC 0xB400
514ddaa2 102 uint16_t initial = reflect(uidcrc, 8);
103 //uint16_t initial = uidcrc;
3e134b4c 104 initial |= initial << 8;
ee4e2816 105 crc_t crc;
3e134b4c 106 crc_init_ref(&crc, 16, CRC16_POLY_LEGIC, initial, 0, TRUE, TRUE);
107 for ( int i=0; i < size; ++i)
ee4e2816 108 crc_update(&crc, buff[i], 8);
3e134b4c 109 return reflect(crc_finish(&crc), 16);
ee4e2816 110}
111
3e134b4c 112//w=16 poly=0x3d65 init=0x0000 refin=true refout=true xorout=0xffff check=0xea82 name="CRC-16/DNP"
113uint32_t CRC16_DNP(uint8_t *buff, size_t size) {
114 crc_t crc;
115 crc_init_ref(&crc, 16, 0x3d65, 0, 0xffff, TRUE, TRUE);
116 for ( int i=0; i < size; ++i)
117 crc_update(&crc, buff[i], 8);
118
119 return BSWAP_16(crc_finish(&crc));
120}
6bb7609c 121
3e134b4c 122//width=16 poly=0x1021 init=0x1d0f refin=false refout=false xorout=0x0000 check=0xe5cc name="CRC-16/AUG-CCITT"
123uint32_t CRC16_CCITT(uint8_t *buff, size_t size) {
124 crc_t crc;
125 crc_init(&crc, 16, 0x1021, 0x1d0f, 0);
126 for ( int i=0; i < size; ++i)
127 crc_update(&crc, buff[i], 8);
128 return crc_finish(&crc);
129}
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