portapack-mayhem/firmware/common/ais_packet.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 __AIS_PACKET_H__
#define __AIS_PACKET_H__

#include "baseband_packet.hpp"
#include "field_reader.hpp"

#include <cstdint>
#include <cstddef>
#include <string>

namespace ais {

struct DateTime {
    uint16_t year;
    uint8_t month;
    uint8_t day;
    uint8_t hour;
    uint8_t minute;
    uint8_t second;
};

template <size_t FieldSize, int32_t DegMax, uint32_t NAValue>
struct LatLonBase {
    constexpr LatLonBase()
        : LatLonBase{raw_not_available} {
    }

    constexpr LatLonBase(
        const int32_t raw)
        : raw_{raw} {
    }

    constexpr LatLonBase(
        const LatLonBase& other)
        : raw_{other.raw_} {
    }

    LatLonBase& operator=(const LatLonBase&) = default;

    int32_t normalized() const {
        return static_cast<int32_t>(raw() << sign_extend_shift) / (1 << sign_extend_shift);
    }

    int32_t raw() const {
        return raw_;
    }

    bool is_not_available() const {
        return raw() == raw_not_available;
    }

    bool is_valid() const {
        return (normalized() >= raw_valid_min) && (normalized() <= raw_valid_max);
    }

   private:
    int32_t raw_;

    static constexpr size_t sign_extend_shift = 32 - FieldSize;

    static constexpr int32_t raw_not_available = NAValue;
    static constexpr int32_t raw_valid_min = -DegMax * 60 * 10000;
    static constexpr int32_t raw_valid_max = DegMax * 60 * 10000;
};

using Latitude = LatLonBase<27, 90, 0x3412140>;
using Longitude = LatLonBase<28, 180, 0x6791AC0>;

using RateOfTurn = int8_t;
using SpeedOverGround = uint16_t;
using CourseOverGround = uint16_t;
using TrueHeading = uint16_t;

using MMSI = uint32_t;

class Packet {
   public:
    constexpr Packet(
        const baseband::Packet& packet)
        : packet_{packet},
          field_{packet_} {
    }

    size_t length() const;

    bool is_valid() const;

    Timestamp received_at() const;

    uint32_t message_id() const;
    MMSI user_id() const;
    MMSI source_id() const;

    uint32_t read(const size_t start_bit, const size_t length) const;

    std::string text(const size_t start_bit, const size_t character_count) const;

    DateTime datetime(const size_t start_bit) const;

    Latitude latitude(const size_t start_bit) const;
    Longitude longitude(const size_t start_bit) const;

    bool crc_ok() const;

   private:
    using Reader = FieldReader<baseband::Packet, BitRemapByteReverse>;
    using CRCReader = FieldReader<baseband::Packet, BitRemapNone>;

    const baseband::Packet packet_;
    const Reader field_;

    const size_t fcs_length = 16;

    size_t data_and_fcs_length() const;
    size_t data_length() const;

    bool length_valid() const;
};

} /* namespace ais */

#endif /*__AIS_PACKET_H__*/