portapack-mayhem/firmware/baseband/packet_builder.hpp

/*
 * Copyright (C) 2014 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 __PACKET_BUILDER_H__
#define __PACKET_BUILDER_H__

#include <cstdint>
#include <cstddef>
#include <bitset>
#include <functional>

#include "bit_pattern.hpp"
#include "baseband_packet.hpp"

struct NeverMatch {
    bool operator()(const BitHistory&, const size_t) const {
        return false;
    }
};

struct FixedLength {
    bool operator()(const BitHistory&, const size_t symbols_received) const {
        return symbols_received >= length;
    }

    const size_t length;
};

template <typename PreambleMatcher, typename UnstuffMatcher, typename EndMatcher>
class PacketBuilder {
   public:
    using PayloadHandlerFunc = std::function<void(const baseband::Packet& packet)>;

    PacketBuilder(
        const PreambleMatcher preamble_matcher,
        const UnstuffMatcher unstuff_matcher,
        const EndMatcher end_matcher,
        PayloadHandlerFunc payload_handler)
        : payload_handler{std::move(payload_handler)},
          preamble(preamble_matcher),
          unstuff(unstuff_matcher),
          end(end_matcher) {
    }

    void configure(
        const PreambleMatcher preamble_matcher,
        const UnstuffMatcher unstuff_matcher) {
        preamble = preamble_matcher;
        unstuff = unstuff_matcher;

        reset_state();
    }

    void execute(
        const uint_fast8_t symbol) {
        bit_history.add(symbol);

        switch (state) {
            case State::Preamble:
                if (preamble(bit_history, packet.size())) {
                    state = State::Payload;
                }
                break;

            case State::Payload:
                if (!unstuff(bit_history, packet.size())) {
                    packet.add(symbol);
                }

                if (end(bit_history, packet.size())) {
                    // NOTE: This check is to avoid std::function nullptr check, which
                    // brings in "_ZSt25__throw_bad_function_callv" and a lot of extra code.
                    // TODO: Make payload_handler known at compile time.
                    if (payload_handler) {
                        packet.set_timestamp(Timestamp::now());
                        payload_handler(packet);
                    }
                    reset_state();
                } else {
                    if (packet_truncated()) {
                        reset_state();
                    }
                }
                break;

            default:
                reset_state();
                break;
        }
    }

   private:
    enum State {
        Preamble,
        Payload,
    };

    bool packet_truncated() const {
        return packet.size() >= packet.capacity();
    }

    const PayloadHandlerFunc payload_handler;

    BitHistory bit_history{};
    PreambleMatcher preamble{};
    UnstuffMatcher unstuff{};
    EndMatcher end{};

    State state{State::Preamble};
    baseband::Packet packet{};

    void reset_state() {
        packet.clear();
        state = State::Preamble;
    }
};

#endif /*__PACKET_BUILDER_H__*/