fix command help

[proxmark3-svn] / common / crc.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>

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);
}