git.zerfleddert.de Git - proxmark3-svn/blob - common/crc.c

   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 "util.h"
  10 #include <stdio.h>
  11 #include <stdint.h>
  12 #include <stddef.h>
  13
  14 void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor)
  15 {
  16         crc->order = order;
  17         crc->polynom = polynom;
  18         crc->initial_value = initial_value;
  19         crc->final_xor = final_xor;
  20         crc->mask = (1L<<order)-1;
  21         crc_clear(crc);
  22 }
  23
  24 void crc_update(crc_t *crc, uint32_t data, int data_width)
  25 {
  26         for( int i=0; i < data_width; i++) {
  27                 int oldstate = crc->state;
  28                 crc->state = crc->state >> 1;
  29                 if( (oldstate^data) & 1 ) {
  30                         crc->state ^= crc->polynom;
  31                 }
  32                 data >>= 1;
  33         }
  34 }
  35
  36 void crc_clear(crc_t *crc)
  37 {
  38         crc->state = crc->initial_value & crc->mask;
  39 }
  40
  41 uint32_t crc_finish(crc_t *crc)
  42 {
  43         return ( crc->state ^ crc->final_xor ) & crc->mask;
  44 }
  45
  46 //credits to iceman
  47 uint32_t CRC8Maxim(uint8_t *buff, size_t size)
  48 {
  49         crc_t crc;
  50         crc_init(&crc, 9, 0x8c, 0x00, 0x00);
  51         crc_clear(&crc);
  52
  53         for (size_t i=0; i < size; ++i)
  54                 crc_update(&crc, buff[i], 8);
  55
  56         return crc_finish(&crc);
  57 }
  58
  59 uint32_t CRC8Legic(uint8_t *buff, size_t size) {
  60
  61         // Poly 0x63,   reversed poly 0xC6,  Init 0x55,  Final 0x00
  62         crc_t crc;
  63         crc_init(&crc, 8, 0xC6, 0x55, 0);
  64         crc_clear(&crc);
  65
  66         for ( int i = 0; i < size; ++i)
  67                 crc_update(&crc, buff[i], 8);
  68         return SwapBits(crc_finish(&crc), 8);
  69 }
  70
  71 uint32_t SwapBits(uint32_t value, int nrbits) {
  72         uint32_t newvalue = 0;
  73         for(int i = 0; i < nrbits; i++) {
  74                 newvalue ^= ((value >> i) & 1) << (nrbits - 1 - i);
  75         }
  76         return newvalue;
  77 }