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[proxmark3-svn] / 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
27 *((uint32_t *)(crc)) = htole32 (desfire_crc);
28 }
29
30 void crc32_append (uint8_t *data, const size_t len) {
31 crc32_ex (data, len, data + len);
32 }
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