d92b0a82cc
"A long time ago in a galaxy far, far away...." we started NFC subsystem refactoring. Starring: - @gornekich - NFC refactoring project lead, architect, senior developer - @gsurkov - architect, senior developer - @RebornedBrain - senior developer Supporting roles: - @skotopes, @DrZlo13, @hedger - general architecture advisors, code review - @Astrrra, @doomwastaken, @Hellitron, @ImagineVagon333 - quality assurance Special thanks: @bettse, @pcunning, @nxv, @noproto, @AloneLiberty and everyone else who has been helping us all this time and contributing valuable knowledges, ideas and source code.
58 lines
1.8 KiB
C
58 lines
1.8 KiB
C
#include "iso14443_crc.h"
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#include <core/check.h>
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#define ISO14443_3A_CRC_INIT (0x6363U)
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#define ISO14443_3B_CRC_INIT (0xFFFFU)
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static uint16_t
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iso14443_crc_calculate(Iso14443CrcType type, const uint8_t* data, size_t data_size) {
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uint16_t crc;
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if(type == Iso14443CrcTypeA) {
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crc = ISO14443_3A_CRC_INIT;
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} else if(type == Iso14443CrcTypeB) {
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crc = ISO14443_3B_CRC_INIT;
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} else {
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furi_crash("Wrong ISO14443 CRC type");
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}
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for(size_t i = 0; i < data_size; i++) {
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uint8_t byte = data[i];
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byte ^= (uint8_t)(crc & 0xff);
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byte ^= byte << 4;
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crc = (crc >> 8) ^ (((uint16_t)byte) << 8) ^ (((uint16_t)byte) << 3) ^ (byte >> 4);
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}
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return type == Iso14443CrcTypeA ? crc : ~crc;
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}
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void iso14443_crc_append(Iso14443CrcType type, BitBuffer* buf) {
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const uint8_t* data = bit_buffer_get_data(buf);
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const size_t data_size = bit_buffer_get_size_bytes(buf);
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const uint16_t crc = iso14443_crc_calculate(type, data, data_size);
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bit_buffer_append_bytes(buf, (const uint8_t*)&crc, ISO14443_CRC_SIZE);
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}
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bool iso14443_crc_check(Iso14443CrcType type, const BitBuffer* buf) {
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const size_t data_size = bit_buffer_get_size_bytes(buf);
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if(data_size <= ISO14443_CRC_SIZE) return false;
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uint16_t crc_received;
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bit_buffer_write_bytes_mid(
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buf, &crc_received, data_size - ISO14443_CRC_SIZE, ISO14443_CRC_SIZE);
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const uint8_t* data = bit_buffer_get_data(buf);
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const uint16_t crc_calc = iso14443_crc_calculate(type, data, data_size - ISO14443_CRC_SIZE);
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return (crc_calc == crc_received);
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}
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void iso14443_crc_trim(BitBuffer* buf) {
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const size_t data_size = bit_buffer_get_size_bytes(buf);
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furi_assert(data_size > ISO14443_CRC_SIZE);
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bit_buffer_set_size_bytes(buf, data_size - ISO14443_CRC_SIZE);
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}
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