portapack-mayhem/firmware/common/bit_pattern.hpp
Jared Boone 0789d50fdf Rework BitHistory, BitPattern, PacketBuilder.
Templatize PacketBuilder to optionally bit unstuff, and have flexible packet termination behavior.
2015-11-09 14:38:09 -08:00

74 lines
1.8 KiB
C++

/*
* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
*
* This file is part of PortaPack.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifndef __BIT_PATTERN_H__
#define __BIT_PATTERN_H__
#include <cstdint>
#include <cstddef>
class BitHistory {
public:
void add(const uint_fast8_t bit) {
history = (history << 1) | (bit & 1);
}
uint32_t value() const {
return history;
}
private:
uint32_t history { 0 };
};
class BitPattern {
public:
constexpr BitPattern(
) : code_ { 0 },
mask_ { 0 },
maximum_hanning_distance_ { 0 }
{
}
constexpr BitPattern(
const uint32_t code,
const size_t code_length,
const size_t maximum_hanning_distance = 0
) : code_ { code },
mask_ { (1U << code_length) - 1U },
maximum_hanning_distance_ { maximum_hanning_distance }
{
}
bool operator()(const BitHistory& history, const size_t) const {
const auto delta_bits = (history.value() ^ code_) & mask_;
const size_t count = __builtin_popcountl(delta_bits);
return (count <= maximum_hanning_distance_);
}
private:
uint32_t code_;
uint32_t mask_;
size_t maximum_hanning_distance_;
};
#endif/*__BIT_PATTERN_H__*/