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58 lines
1.4 KiB
C++
58 lines
1.4 KiB
C++
//
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// CRC.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 18/09/2016.
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// Copyright 2016 Thomas Harte. All rights reserved.
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//
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#ifndef CRC_hpp
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#define CRC_hpp
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#include <cstdint>
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namespace NumberTheory {
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/*! Provides a class capable of accumulating a CRC16 from source data. */
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class CRC16 {
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public:
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/*!
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Instantiates a CRC16 that will compute the CRC16 specified by the supplied
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@c polynomial and @c reset_value.
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*/
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CRC16(uint16_t polynomial, uint16_t reset_value) :
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reset_value_(reset_value), value_(reset_value) {
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for(int c = 0; c < 256; c++) {
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uint16_t shift_value = static_cast<uint16_t>(c << 8);
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for(int b = 0; b < 8; b++) {
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uint16_t exclusive_or = (shift_value&0x8000) ? polynomial : 0x0000;
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shift_value = static_cast<uint16_t>(shift_value << 1) ^ exclusive_or;
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}
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xor_table[c] = static_cast<uint16_t>(shift_value);
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}
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}
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/// Resets the CRC to the reset value.
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inline void reset() { value_ = reset_value_; }
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/// Updates the CRC to include @c byte.
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inline void add(uint8_t byte) {
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value_ = static_cast<uint16_t>((value_ << 8) ^ xor_table[(value_ >> 8) ^ byte]);
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}
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/// @returns The current value of the CRC.
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inline uint16_t get_value() const { return value_; }
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/// Sets the current value of the CRC.
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inline void set_value(uint16_t value) { value_ = value; }
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private:
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const uint16_t reset_value_;
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uint16_t xor_table[256];
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uint16_t value_;
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};
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}
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#endif /* CRC_hpp */
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