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.
53 lines
1.5 KiB
C
53 lines
1.5 KiB
C
#include "felica_crc.h"
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#include <furi/furi.h>
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#define FELICA_CRC_POLY (0x1021U) // Polynomial: x^16 + x^12 + x^5 + 1
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#define FELICA_CRC_INIT (0x0000U)
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uint16_t felica_crc_calculate(const uint8_t* data, size_t length) {
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uint16_t crc = FELICA_CRC_INIT;
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for(size_t i = 0; i < length; i++) {
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crc ^= ((uint16_t)data[i] << 8);
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for(size_t j = 0; j < 8; j++) {
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if(crc & 0x8000) {
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crc <<= 1;
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crc ^= FELICA_CRC_POLY;
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} else {
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crc <<= 1;
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}
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}
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}
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return (crc << 8) | (crc >> 8);
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}
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void felica_crc_append(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 = felica_crc_calculate(data, data_size);
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bit_buffer_append_bytes(buf, (const uint8_t*)&crc, FELICA_CRC_SIZE);
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}
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bool felica_crc_check(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 <= FELICA_CRC_SIZE) return false;
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uint16_t crc_received;
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bit_buffer_write_bytes_mid(buf, &crc_received, data_size - FELICA_CRC_SIZE, FELICA_CRC_SIZE);
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const uint8_t* data = bit_buffer_get_data(buf);
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const uint16_t crc_calc = felica_crc_calculate(data, data_size - FELICA_CRC_SIZE);
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return (crc_calc == crc_received);
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}
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void felica_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 > FELICA_CRC_SIZE);
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bit_buffer_set_size_bytes(buf, data_size - FELICA_CRC_SIZE);
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}
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