-/*
- * crc.c
- *
- * Generic CRC calculation code.
- *
- */
-
+//-----------------------------------------------------------------------------
+// This code is licensed to you under the terms of the GNU GPL, version 2 or,
+// at your option, any later version. See the LICENSE.txt file for the text of
+// the license.
+//-----------------------------------------------------------------------------
+// Generic CRC calculation code.
+//-----------------------------------------------------------------------------
#include "crc.h"
+#include <stdint.h>
+#include <stddef.h>
+
+#define BITMASK(X) (1 << (X))
+
+uint32_t reflect(uint32_t v, int b) {
+ uint32_t t = v;
+ for (int i = 0; i < b; ++i) {
+ if (t & 1)
+ v |= BITMASK((b - 1) - i);
+ else
+ v &= ~BITMASK((b - 1) - i);
+ t >>= 1;
+ }
+ return v;
+}
void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor)
{
{
return ( crc->state ^ crc->final_xor ) & crc->mask;
}
+
+//credits to iceman
+uint32_t CRC8Maxim(uint8_t *buff, size_t size)
+{
+ crc_t crc;
+ crc_init(&crc, 9, 0x8c, 0x00, 0x00);
+ crc_clear(&crc);
+
+ for (size_t i=0; i < size; ++i){
+ crc_update(&crc, buff[i], 8);
+ }
+ return crc_finish(&crc);
+}
+
+// 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"
+uint32_t CRC8Mad(uint8_t *buff, size_t size) {
+ crc_t crc;
+ crc_init(&crc, 8, reflect(0x1d, 8), reflect(0xc7, 8), 0);
+ for (int i = 0; i < size; ++i)
+ crc_update(&crc, reflect(buff[i], 8), 8);
+
+ return reflect(crc_finish(&crc), 8);
+}