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https://github.com/RfidResearchGroup/proxmark3.git
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35 lines
914 B
C
35 lines
914 B
C
#include <stdint.h>
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#include <stddef.h>
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#include "crc32.h"
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#define htole32(x) (x)
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#define CRC32_PRESET 0xFFFFFFFF
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static void crc32_byte (uint32_t *crc, const uint8_t value);
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static void crc32_byte (uint32_t *crc, const uint8_t value) {
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/* x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1 */
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const uint32_t poly = 0xEDB88320;
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*crc ^= value;
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for (int current_bit = 7; current_bit >= 0; current_bit--) {
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int bit_out = (*crc) & 0x00000001;
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*crc >>= 1;
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if (bit_out)
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*crc ^= poly;
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}
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}
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void crc32 (const uint8_t *data, const size_t len, uint8_t *crc) {
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uint32_t desfire_crc = CRC32_PRESET;
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for (size_t i = 0; i < len; i++) {
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crc32_byte (&desfire_crc, data[i]);
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}
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*((uint32_t *)(crc)) = htole32 (desfire_crc);
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}
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void crc32_append (uint8_t *data, const size_t len) {
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crc32 (data, len, data + len);
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}
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