mirror of
https://github.com/Proxmark/proxmark3.git
synced 2024-11-23 14:00:18 -08:00
81 lines
2.0 KiB
C
81 lines
2.0 KiB
C
//-----------------------------------------------------------------------------
|
|
// This code is licensed to you under the terms of the GNU GPL, version 2 or,
|
|
// at your option, any later version. See the LICENSE.txt file for the text of
|
|
// the license.
|
|
//-----------------------------------------------------------------------------
|
|
// Generic CRC calculation code.
|
|
//-----------------------------------------------------------------------------
|
|
#include "crc.h"
|
|
#include <stdint.h>
|
|
#include <stddef.h>
|
|
|
|
#define BITMASK(X) (1 << (X))
|
|
|
|
uint32_t reflect(uint32_t v, int b) {
|
|
uint32_t t = v;
|
|
for (int i = 0; i < b; ++i) {
|
|
if (t & 1)
|
|
v |= BITMASK((b - 1) - i);
|
|
else
|
|
v &= ~BITMASK((b - 1) - i);
|
|
t >>= 1;
|
|
}
|
|
return v;
|
|
}
|
|
|
|
void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor)
|
|
{
|
|
crc->order = order;
|
|
crc->polynom = polynom;
|
|
crc->initial_value = initial_value;
|
|
crc->final_xor = final_xor;
|
|
crc->mask = (1L<<order)-1;
|
|
crc_clear(crc);
|
|
}
|
|
|
|
void crc_update(crc_t *crc, uint32_t data, int data_width)
|
|
{
|
|
int i;
|
|
for(i=0; i<data_width; i++) {
|
|
int oldstate = crc->state;
|
|
crc->state = crc->state >> 1;
|
|
if( (oldstate^data) & 1 ) {
|
|
crc->state ^= crc->polynom;
|
|
}
|
|
data >>= 1;
|
|
}
|
|
}
|
|
|
|
void crc_clear(crc_t *crc)
|
|
{
|
|
crc->state = crc->initial_value & crc->mask;
|
|
}
|
|
|
|
uint32_t crc_finish(crc_t *crc)
|
|
{
|
|
return ( crc->state ^ crc->final_xor ) & crc->mask;
|
|
}
|
|
|
|
//credits to iceman
|
|
uint32_t CRC8Maxim(uint8_t *buff, size_t size)
|
|
{
|
|
crc_t crc;
|
|
crc_init(&crc, 9, 0x8c, 0x00, 0x00);
|
|
crc_clear(&crc);
|
|
|
|
for (size_t i=0; i < size; ++i){
|
|
crc_update(&crc, buff[i], 8);
|
|
}
|
|
return crc_finish(&crc);
|
|
}
|
|
|
|
// 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"
|
|
uint32_t CRC8Mad(uint8_t *buff, size_t size) {
|
|
crc_t crc;
|
|
crc_init(&crc, 8, reflect(0x1d, 8), reflect(0xc7, 8), 0);
|
|
for (int i = 0; i < size; ++i)
|
|
crc_update(&crc, reflect(buff[i], 8), 8);
|
|
|
|
return reflect(crc_finish(&crc), 8);
|
|
}
|