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 // the Check value below in the comments is CRC of the string '123456789'
   9 //
  10 #include "crc.h"
  11
  12 #include "commonutil.h"
  13
  14 void crc_init_ref(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor, bool refin, bool refout) {
  15     crc_init(crc, order, polynom, initial_value, final_xor);
  16     crc->refin = refin;
  17     crc->refout = refout;
  18     crc_clear(crc);
  19 }
  20
  21 void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor) {
  22     crc->order = order;
  23     crc->topbit = BITMASK(order - 1);
  24     crc->polynom = polynom;
  25     crc->initial_value = initial_value;
  26     crc->final_xor = final_xor;
  27     crc->mask = (1L << order) - 1;
  28     crc->refin = false;
  29     crc->refout = false;
  30     crc_clear(crc);
  31 }
  32
  33 void crc_clear(crc_t *crc) {
  34
  35     crc->state = crc->initial_value & crc->mask;
  36     if (crc->refin)
  37         crc->state = reflect(crc->state, crc->order);
  38 }
  39
  40 void crc_update2(crc_t *crc, uint32_t data, int data_width) {
  41
  42     if (crc->refin)
  43         data = reflect(data, data_width);
  44
  45     // Bring the next byte into the remainder.
  46     crc->state ^= data << (crc->order - data_width);
  47
  48     for (uint8_t bit = data_width; bit > 0; --bit) {
  49
  50         if (crc->state & crc->topbit)
  51             crc->state = (crc->state << 1) ^ crc->polynom;
  52         else
  53             crc->state = (crc->state << 1);
  54     }
  55 }
  56
  57 void crc_update(crc_t *crc, uint32_t data, int data_width) {
  58     if (crc->refin)
  59         data = reflect(data, data_width);
  60
  61     int i;
  62     for (i = 0; i < data_width; i++) {
  63         int oldstate = crc->state;
  64         crc->state = crc->state >> 1;
  65         if ((oldstate ^ data) & 1) {
  66             crc->state ^= crc->polynom;
  67         }
  68         data >>= 1;
  69     }
  70 }
  71
  72 uint32_t crc_finish(crc_t *crc) {
  73     uint32_t val = crc->state;
  74     if (crc->refout)
  75         val = reflect(val, crc->order);
  76     return (val ^ crc->final_xor) & crc->mask;
  77 }
  78
  79 /*
  80 static void print_crc(crc_t *crc) {
  81     printf(" Order  %d\n Poly   %x\n Init   %x\n Final  %x\n Mask   %x\n topbit %x\n RefIn  %s\n RefOut %s\n State  %x\n",
  82         crc->order,
  83         crc->polynom,
  84         crc->initial_value,
  85         crc->final_xor,
  86         crc->mask,
  87         crc->topbit,
  88         (crc->refin) ? "TRUE":"FALSE",
  89         (crc->refout) ? "TRUE":"FALSE",
  90         crc->state
  91     );
  92 }
  93 */
  94
  95 // width=8  poly=0x31  init=0x00  refin=true  refout=true  xorout=0x00  check=0xA1  name="CRC-8/MAXIM"
  96 uint32_t CRC8Maxim(uint8_t *buff, size_t size) {
  97     crc_t crc;
  98     crc_init_ref(&crc, 8, 0x31, 0, 0, true, true);
  99     for (size_t i = 0; i < size; ++i)
 100         crc_update2(&crc, buff[i], 8);
 101     return crc_finish(&crc);
 102 }
 103 // 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"
 104 uint32_t CRC8Mad(uint8_t *buff, size_t size) {
 105     crc_t crc;
 106     crc_init_ref(&crc, 8, 0x1d, 0xc7, 0, false, false);
 107     for (size_t i = 0; i < size; ++i)
 108         crc_update2(&crc, buff[i], 8);
 109     return crc_finish(&crc);
 110 }
 111 // width=4  poly=0xC, reversed poly=0x7  init=0x5   refin=true  refout=true  xorout=0x0000  check=  name="CRC-4/LEGIC"
 112 uint32_t CRC4Legic(uint8_t *buff, size_t size) {
 113     crc_t crc;
 114     crc_init_ref(&crc, 4, 0x19 >> 1, 0x5, 0, true, true);
 115     crc_update2(&crc, 1, 1); /* CMD_READ */
 116     crc_update2(&crc, buff[0], 8);
 117     crc_update2(&crc, buff[1], 8);
 118     return reflect(crc_finish(&crc), 4);
 119 }
 120 // width=8  poly=0x63, reversed poly=0x8D  init=0x55  refin=true  refout=true  xorout=0x0000  check=0xC6  name="CRC-8/LEGIC"
 121 // the CRC needs to be reversed before returned.
 122 uint32_t CRC8Legic(uint8_t *buff, size_t size) {
 123     crc_t crc;
 124     crc_init_ref(&crc, 8, 0x63, 0x55, 0, true, true);
 125     for (size_t i = 0; i < size; ++i)
 126         crc_update2(&crc, buff[i], 8);
 127     return reflect8(crc_finish(&crc));
 128 }
 129 // width=8  poly=0x107, init=0x2C  refin=true  refout=true  xorout=0x0000  check=0 name="CRC-8/CARDX"
 130 uint32_t CRC8Cardx(uint8_t *buff, size_t size) {
 131     crc_t crc;
 132     crc_init_ref(&crc, 8, 0x107, 0x2C, 0, true, true);
 133     for (size_t i = 0; i < size; ++i)
 134         crc_update2(&crc, buff[i], 8);
 135     return crc_finish(&crc);
 136 }