mayhem-firmware/firmware/common/bit_pattern.hpp

/*
 * 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);
    }

    uint64_t value() const {
        return history;
    }

   private:
    uint64_t history{0};
};

class BitPattern {
   public:
    constexpr BitPattern()
        : code_{0},
          mask_{0},
          maximum_hanning_distance_{0} {
    }

    constexpr BitPattern(
        const uint64_t code,
        const size_t code_length,
        const size_t maximum_hanning_distance = 0)
        : code_{code},
          mask_{(1ULL << code_length) - 1ULL},
          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_popcountll(delta_bits);
        return (count <= maximum_hanning_distance_);
    }

   private:
    uint64_t code_;
    uint64_t mask_;
    size_t maximum_hanning_distance_;
};

#endif /*__BIT_PATTERN_H__*/