projects / proxmark3-svn / blame
| Commit | Line | Data |
|---|---|---|
| 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 | //----------------------------------------------------------------------------- | |
| 68d9d60a | 8 | #include "crc.h" |
| 73d04bb4 | 9 | #include <stdint.h> |
| 10 | #include <stddef.h> | |
| 68d9d60a | 11 | |
| fdd9395d OM |
12 | #define BITMASK(X) (1 << (X)) |
| 13 | ||
| 14 | uint32_t reflect(uint32_t v, int b) { | |
| 15 | uint32_t t = v; | |
| 16 | for (int i = 0; i < b; ++i) { | |
| 17 | if (t & 1) | |
| 18 | v |= BITMASK((b - 1) - i); | |
| 19 | else | |
| 20 | v &= ~BITMASK((b - 1) - i); | |
| 21 | t >>= 1; | |
| 22 | } | |
| 23 | return v; | |
| 24 | } | |
| 25 | ||
| 68d9d60a | 26 | void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor) |
| 27 | { | |
| 28 | crc->order = order; | |
| 29 | crc->polynom = polynom; | |
| 30 | crc->initial_value = initial_value; | |
| 31 | crc->final_xor = final_xor; | |
| 32 | crc->mask = (1L<<order)-1; | |
| 33 | crc_clear(crc); | |
| 34 | } | |
| 35 | ||
| 36 | void crc_update(crc_t *crc, uint32_t data, int data_width) | |
| 37 | { | |
| 38 | int i; | |
| 39 | for(i=0; i<data_width; i++) { | |
| 40 | int oldstate = crc->state; | |
| 41 | crc->state = crc->state >> 1; | |
| 42 | if( (oldstate^data) & 1 ) { | |
| 43 | crc->state ^= crc->polynom; | |
| 44 | } | |
| 45 | data >>= 1; | |
| 46 | } | |
| 47 | } | |
| 48 | ||
| 49 | void crc_clear(crc_t *crc) | |
| 50 | { | |
| 51 | crc->state = crc->initial_value & crc->mask; | |
| 52 | } | |
| 53 | ||
| 54 | uint32_t crc_finish(crc_t *crc) | |
| 55 | { | |
| 56 | return ( crc->state ^ crc->final_xor ) & crc->mask; | |
| 57 | } | |
| 73d04bb4 | 58 | |
| e74fc2ec | 59 | //credits to iceman |
| 60 | uint32_t CRC8Maxim(uint8_t *buff, size_t size) | |
| 73d04bb4 | 61 | { |
| 62 | crc_t crc; | |
| 63 | crc_init(&crc, 9, 0x8c, 0x00, 0x00); | |
| 64 | crc_clear(&crc); | |
| 65 | ||
| 66 | for (size_t i=0; i < size; ++i){ | |
| 67 | crc_update(&crc, buff[i], 8); | |
| 68 | } | |
| 69 | return crc_finish(&crc); | |
| 70 | } | |
| fdd9395d OM |
71 | |
| 72 | // width=8 poly=0x1d, init=0xc7 (0xe3 - WRONG! but it mentioned in MAD datasheet) refin=false refout=false xorout=0x00 name="CRC-8/MIFARE-MAD" | |
| 73 | uint32_t CRC8Mad(uint8_t *buff, size_t size) { | |
| 74 | crc_t crc; | |
| 75 | crc_init(&crc, 8, reflect(0x1d, 8), reflect(0xc7, 8), 0); | |
| 76 | for (int i = 0; i < size; ++i) | |
| 77 | crc_update(&crc, reflect(buff[i], 8), 8); | |
| 78 | ||
| 79 | return reflect(crc_finish(&crc), 8); | |
| 80 | } |