src/lib/CRC/crc.cpp

   1 #include "crc.h"
   2
   3 GENERIC_CRC8::GENERIC_CRC8(uint8_t poly)
   4 {
   5     uint8_t crc;
   6
   7     for (uint16_t i = 0; i < crclen; i++)
   8     {
   9         crc = i;
  10         for (uint8_t j = 0; j < 8; j++)
  11         {
  12             crc = (crc << 1) ^ ((crc & 0x80) ? poly : 0);
  13         }
  14         crc8tab[i] = crc & 0xFF;
  15     }
  16 }
  17
  18 uint8_t ICACHE_RAM_ATTR GENERIC_CRC8::calc(const uint8_t data)
  19 {
  20     return crc8tab[data];
  21 }
  22
  23 uint8_t ICACHE_RAM_ATTR GENERIC_CRC8::calc(const uint8_t *data, uint16_t len, uint8_t crc)
  24 {
  25     while (len--)
  26     {
  27         crc = crc8tab[crc ^ *data++];
  28     }
  29     return crc;
  30 }
  31
  32 void Crc2Byte::init(uint8_t bits, uint16_t poly)
  33 {
  34     if (bits == _bits && poly == _poly)
  35         return;
  36     _poly = poly;
  37     _bits = bits;
  38     _bitmask = (1 << _bits) - 1;
  39     uint16_t highbit = 1 << (_bits - 1);
  40     uint16_t crc;
  41     for (uint16_t i = 0; i < crclen; i++)
  42     {
  43         crc = i << (bits - 8);
  44         for (uint8_t j = 0; j < 8; j++)
  45         {
  46             crc = (crc << 1) ^ ((crc & highbit) ? poly : 0);
  47         }
  48         _crctab[i] = crc;
  49     }
  50 }
  51
  52 uint16_t ICACHE_RAM_ATTR Crc2Byte::calc(uint8_t *data, uint8_t len, uint16_t crc)
  53 {
  54     while (len--)
  55     {
  56         crc = (crc << 8) ^ _crctab[((crc >> (_bits - 8)) ^ (uint16_t) *data++) & 0x00FF];
  57     }
  58     return crc & _bitmask;
  59 }