common/crc32.c

   1 #include <stdint.h>
   2 #include <stddef.h>
   3 #include "crc32.h"
   4
   5 #define htole32(x) (x)
   6 #define CRC32_PRESET 0xFFFFFFFF
   7
   8
   9 static void crc32_byte (uint32_t *crc, const uint8_t value);
  10
  11 static void crc32_byte (uint32_t *crc, const uint8_t value) {
  12     /* x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1 */
  13     const uint32_t poly = 0xEDB88320;
  14
  15     *crc ^= value;
  16     for (int current_bit = 7; current_bit >= 0; current_bit--) {
  17         int bit_out = (*crc) & 0x00000001;
  18         *crc >>= 1;
  19         if (bit_out)
  20             *crc ^= poly;
  21     }
  22 }
  23
  24 void crc32 (const uint8_t *data, const size_t len, uint8_t *crc) {
  25     uint32_t desfire_crc = CRC32_PRESET;
  26     for (size_t i = 0; i < len; i++) {
  27         crc32_byte (&desfire_crc, data[i]);
  28     }
  29
  30     *((uint32_t *)(crc)) = htole32 (desfire_crc);
  31 }
  32
  33 void crc32_append (uint8_t *data, const size_t len) {
  34     crc32 (data, len, data + len);
  35 }