mirror of
https://github.com/eried/portapack-mayhem.git
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108 lines
2.5 KiB
C++
108 lines
2.5 KiB
C++
/*
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* Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
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*
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* This file is part of PortaPack.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#ifndef __CRC_H__
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#define __CRC_H__
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#include <cstddef>
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#include <cstdint>
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/* Inspired by
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* http://www.barrgroup.com/Embedded-Systems/How-To/CRC-Calculation-C-Code
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*
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* ...then munged into a shape resembling boost::crc_basic.
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* http://www.boost.org/doc/libs/release/libs/crc/
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*/
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template<typename T>
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class CRC {
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public:
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constexpr CRC(
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const T truncated_polynomial,
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const T initial_remainder = 0,
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const T final_xor_value = 0
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) : truncated_polynomial { truncated_polynomial },
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initial_remainder { initial_remainder },
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final_xor_value { final_xor_value },
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remainder { initial_remainder }
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{
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}
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T get_initial_remainder() const {
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return initial_remainder;
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}
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void reset(T new_initial_remainder) {
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remainder = new_initial_remainder;
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}
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void reset() {
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remainder = initial_remainder;
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}
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void process_bit(bool bit) {
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remainder ^= bit << (width() - 1);
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if( remainder & top_bit() ) {
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remainder = (remainder << 1) ^ truncated_polynomial;
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} else {
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remainder = (remainder << 1);
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}
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}
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void process_byte(const uint8_t data) {
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remainder ^= data << (width() - 8);
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for(size_t bit=0; bit<8; bit++) {
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if( remainder & top_bit() ) {
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remainder = (remainder << 1) ^ truncated_polynomial;
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} else {
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remainder = (remainder << 1);
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}
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}
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}
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void process_bytes(const uint8_t* const data, const size_t length) {
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for(size_t i=0; i<length; i++) {
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process_byte(data[i]);
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}
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}
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T checksum() const {
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return remainder ^ final_xor_value;
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}
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private:
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const T truncated_polynomial;
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const T initial_remainder;
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const T final_xor_value;
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T remainder;
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static constexpr size_t width() {
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return 8 * sizeof(T);
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}
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static constexpr T top_bit() {
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return 1U << (width() - 1);
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}
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};
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#endif/*__CRC_H__*/
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