common/crc32.c

   1 #include "crc32.h"
   2
   3 #define htole32(x) (x)
   4 #define CRC32_PRESET 0xFFFFFFFF
   5
   6 static void crc32_byte(uint32_t *crc, const uint8_t value);
   7
   8 static void crc32_byte(uint32_t *crc, const uint8_t value) {
   9     /* x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1 */
  10     const uint32_t poly = 0xEDB88320;
  11
  12     *crc ^= value;
  13     for (int current_bit = 7; current_bit >= 0; current_bit--) {
  14         int bit_out = (*crc) & 0x00000001;
  15         *crc >>= 1;
  16         if (bit_out)
  17             *crc ^= poly;
  18     }
  19 }
  20
  21 void crc32_ex(const uint8_t *data, const size_t len, uint8_t *crc) {
  22     uint32_t desfire_crc = CRC32_PRESET;
  23     for (size_t i = 0; i < len; i++) {
  24         crc32_byte(&desfire_crc, data[i]);
  25     }
  26     uint32_t crctmp = htole32(desfire_crc);
  27     for (size_t i = 0; i < sizeof(uint32_t); i++) {
  28         crc[i] = ((uint8_t *) &crctmp)[i];
  29     }
  30 }
  31
  32 void crc32_append(uint8_t *data, const size_t len) {
  33     crc32_ex(data, len, data + len);
  34 }