| 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 <stdint.h> |
| 10 | #include <stddef.h> |
| 11 | |
| 12 | void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor) |
| 13 | { |
| 14 | crc->order = order; |
| 15 | crc->polynom = polynom; |
| 16 | crc->initial_value = initial_value; |
| 17 | crc->final_xor = final_xor; |
| 18 | crc->mask = (1L<<order)-1; |
| 19 | crc_clear(crc); |
| 20 | } |
| 21 | |
| 22 | void crc_update(crc_t *crc, uint32_t data, int data_width) |
| 23 | { |
| 24 | int i; |
| 25 | for(i=0; i<data_width; i++) { |
| 26 | int oldstate = crc->state; |
| 27 | crc->state = crc->state >> 1; |
| 28 | if( (oldstate^data) & 1 ) { |
| 29 | crc->state ^= crc->polynom; |
| 30 | } |
| 31 | data >>= 1; |
| 32 | } |
| 33 | } |
| 34 | |
| 35 | void crc_clear(crc_t *crc) |
| 36 | { |
| 37 | crc->state = crc->initial_value & crc->mask; |
| 38 | } |
| 39 | |
| 40 | uint32_t crc_finish(crc_t *crc) |
| 41 | { |
| 42 | return ( crc->state ^ crc->final_xor ) & crc->mask; |
| 43 | } |
| 44 | |
| 45 | //credits to iceman |
| 46 | uint32_t CRC8Maxim(uint8_t *buff, size_t size) |
| 47 | { |
| 48 | crc_t crc; |
| 49 | crc_init(&crc, 9, 0x8c, 0x00, 0x00); |
| 50 | crc_clear(&crc); |
| 51 | |
| 52 | for (size_t i=0; i < size; ++i){ |
| 53 | crc_update(&crc, buff[i], 8); |
| 54 | } |
| 55 | return crc_finish(&crc); |
| 56 | } |