unleashed-firmware/lib/nfc/helpers/iso14443_crc.c
2024-03-25 13:53:32 +03:00

63 lines
1.9 KiB
C

#include "iso14443_crc.h"
#include <core/check.h>
#define ISO14443_3A_CRC_INIT (0x6363U)
#define ISO14443_3B_CRC_INIT (0xFFFFU)
static uint16_t
iso14443_crc_calculate(Iso14443CrcType type, const uint8_t* data, size_t data_size) {
uint16_t crc;
if(type == Iso14443CrcTypeA) {
crc = ISO14443_3A_CRC_INIT;
} else if(type == Iso14443CrcTypeB) {
crc = ISO14443_3B_CRC_INIT;
} else {
furi_crash("Wrong ISO14443 CRC type");
}
for(size_t i = 0; i < data_size; i++) {
uint8_t byte = data[i];
byte ^= (uint8_t)(crc & 0xff);
byte ^= byte << 4;
crc = (crc >> 8) ^ (((uint16_t)byte) << 8) ^ (((uint16_t)byte) << 3) ^ (byte >> 4);
}
return type == Iso14443CrcTypeA ? crc : ~crc;
}
void iso14443_crc_append(Iso14443CrcType type, BitBuffer* buf) {
furi_check(buf);
const uint8_t* data = bit_buffer_get_data(buf);
const size_t data_size = bit_buffer_get_size_bytes(buf);
const uint16_t crc = iso14443_crc_calculate(type, data, data_size);
bit_buffer_append_bytes(buf, (const uint8_t*)&crc, ISO14443_CRC_SIZE);
}
bool iso14443_crc_check(Iso14443CrcType type, const BitBuffer* buf) {
furi_check(buf);
const size_t data_size = bit_buffer_get_size_bytes(buf);
if(data_size <= ISO14443_CRC_SIZE) return false;
uint16_t crc_received;
bit_buffer_write_bytes_mid(
buf, &crc_received, data_size - ISO14443_CRC_SIZE, ISO14443_CRC_SIZE);
const uint8_t* data = bit_buffer_get_data(buf);
const uint16_t crc_calc = iso14443_crc_calculate(type, data, data_size - ISO14443_CRC_SIZE);
return (crc_calc == crc_received);
}
void iso14443_crc_trim(BitBuffer* buf) {
furi_check(buf);
const size_t data_size = bit_buffer_get_size_bytes(buf);
furi_check(data_size > ISO14443_CRC_SIZE);
bit_buffer_set_size_bytes(buf, data_size - ISO14443_CRC_SIZE);
}