mavlink_channels.h

#pragma once

#include <cstdint>
#include <mutex>

namespace mavsdk {

class MAVLinkChannels {
public:
    static MAVLinkChannels& Instance()
    {
        // This should be thread-safe in C++11.
        static MAVLinkChannels instance;

        return instance;
    }

    // delete copy and move constructors and assign operators
    MAVLinkChannels(MAVLinkChannels const&) = delete; // Copy construct
    MAVLinkChannels(MAVLinkChannels&&) = delete; // Move construct
    MAVLinkChannels& operator=(MAVLinkChannels const&) = delete; // Copy assign
    MAVLinkChannels& operator=(MAVLinkChannels&&) = delete; // Move assign

    MAVLinkChannels();
    ~MAVLinkChannels();

    /**
     * Check out a free channel and mark it as used.
     *
     * @param new_channel: the channel assigned to use
     * @return true if a free channel was available.
     */
    bool checkout_free_channel(uint8_t& new_channel);

    /**
     * Check a used channel back in and mark it as free again.
     *
     * @param used_channel: the channel that is returned
     */
    void checkin_used_channel(uint8_t used_channel);

    uint8_t get_max_channels() { return MAX_CHANNELS; }

private:
    // It is not clear what the limit of the number of channels is, except UINT8_MAX.
    static constexpr uint8_t MAX_CHANNELS = 32;

    bool _channels_used[MAX_CHANNELS];
    std::mutex _channels_used_mutex;
};

} // namespace mavsdk