kopia lustrzana https://github.com/f4exb/sdrangel
83 wiersze
1.5 KiB
C++
83 wiersze
1.5 KiB
C++
// Copyright 2020 Mobilinkd LLC.
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#pragma once
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#include <cstdint>
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#include <array>
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#include <cstddef>
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namespace modemm17
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{
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struct CRC16
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{
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static const uint16_t MASK = 0xFFFF;
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static const uint16_t LSB = 0x0001;
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static const uint16_t MSB = 0x8000;
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CRC16(uint16_t poly = 0x5935, uint16_t init = 0xFFFF) :
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poly_(poly),
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init_(init)
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{
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reg_ = init_;
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}
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void reset()
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{
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reg_ = init_;
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for (size_t i = 0; i != 16; ++i)
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{
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auto bit = reg_ & LSB;
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if (bit) reg_ ^= poly_;
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reg_ >>= 1;
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if (bit) reg_ |= MSB;
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}
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reg_ &= MASK;
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}
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void operator()(uint8_t byte)
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{
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reg_ = crc(byte, reg_);
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}
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uint16_t crc(uint8_t byte, uint16_t reg)
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{
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for (size_t i = 0; i != 8; ++i)
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{
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auto msb = reg & MSB;
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reg = ((reg << 1) & MASK) | ((byte >> (7 - i)) & LSB);
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if (msb) reg ^= poly_;
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}
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return reg & MASK;
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}
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uint16_t get()
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{
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auto reg = reg_;
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for (size_t i = 0; i != 16; ++i)
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{
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auto msb = reg & MSB;
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reg = ((reg << 1) & MASK);
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if (msb) reg ^= poly_;
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}
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return reg;
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}
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std::array<uint8_t, 2> get_bytes()
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{
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auto crc = get();
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std::array<uint8_t, 2> result{uint8_t((crc >> 8) & 0xFF), uint8_t(crc & 0xFF)};
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return result;
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}
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private:
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uint16_t poly_;
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uint16_t init_;
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uint16_t reg_;
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};
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} // modemm17
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