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https://github.com/RfidResearchGroup/proxmark3.git
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56 lines
1.4 KiB
C
56 lines
1.4 KiB
C
//-----------------------------------------------------------------------------
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// This code is licensed to you under the terms of the GNU GPL, version 2 or,
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// at your option, any later version. See the LICENSE.txt file for the text of
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// the license.
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//-----------------------------------------------------------------------------
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// Generic CRC calculation code.
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//-----------------------------------------------------------------------------
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#include "crc.h"
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#include <stdint.h>
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#include <stddef.h>
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void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor)
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{
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crc->order = order;
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crc->polynom = polynom;
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crc->initial_value = initial_value;
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crc->final_xor = final_xor;
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crc->mask = (1L<<order)-1;
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crc_clear(crc);
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}
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void crc_update(crc_t *crc, uint32_t data, int data_width)
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{
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int i;
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for(i=0; i<data_width; i++) {
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int oldstate = crc->state;
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crc->state = crc->state >> 1;
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if( (oldstate^data) & 1 ) {
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crc->state ^= crc->polynom;
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}
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data >>= 1;
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}
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}
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void crc_clear(crc_t *crc)
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{
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crc->state = crc->initial_value & crc->mask;
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}
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uint32_t crc_finish(crc_t *crc)
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{
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return ( crc->state ^ crc->final_xor ) & crc->mask;
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}
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//credits to iceman
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uint32_t CRC8Maxim(uint8_t *buff, size_t size)
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{
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crc_t crc;
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crc_init(&crc, 9, 0x8c, 0x00, 0x00);
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crc_clear(&crc);
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for (size_t i=0; i < size; ++i){
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crc_update(&crc, buff[i], 8);
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}
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return crc_finish(&crc);
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}
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