+#include <stdint.h>
+#include <stddef.h>
+#include "crc32.h"
+
+#define htole32(x) (x)
+#define CRC32_PRESET 0xFFFFFFFF
+
+
+static void crc32_byte (uint32_t *crc, const uint8_t value);
+
+static void crc32_byte (uint32_t *crc, const uint8_t value) {
+ /* x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1 */
+ const uint32_t poly = 0xEDB88320;
+
+ *crc ^= value;
+ for (int current_bit = 7; current_bit >= 0; current_bit--) {
+ int bit_out = (*crc) & 0x00000001;
+ *crc >>= 1;
+ if (bit_out)
+ *crc ^= poly;
+ }
+}
+
+void crc32 (const uint8_t *data, const size_t len, uint8_t *crc) {
+ uint32_t desfire_crc = CRC32_PRESET;
+ for (size_t i = 0; i < len; i++) {
+ crc32_byte (&desfire_crc, data[i]);
+ }
+
+ *((uint32_t *)(crc)) = htole32 (desfire_crc);
+}
+
+void crc32_append (uint8_t *data, const size_t len) {
+ crc32 (data, len, data + len);
+}