PX4-Autopilot/platforms/common/uORB/SubscriptionCallback.hpp

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/**
 * @file SubscriptionCallback.hpp
 *
 */

#pragma once

#include <uORB/SubscriptionInterval.hpp>
#include <containers/List.hpp>
#include <px4_platform_common/px4_work_queue/WorkItem.hpp>

namespace uORB
{

// Subscription wrapper class with callbacks on new publications
class SubscriptionCallback : public SubscriptionInterval, public ListNode<SubscriptionCallback *>
{
public:
	/**
	 * Constructor
	 *
	 * @param meta The uORB metadata (usually from the ORB_ID() macro) for the topic.
	 * @param interval_us The requested maximum update interval in microseconds.
	 * @param instance The instance for multi sub.
	 */
	SubscriptionCallback(const orb_metadata *meta, uint32_t interval_us = 0, uint8_t instance = 0) :
		SubscriptionInterval(meta, interval_us, instance)
	{
	}

	virtual ~SubscriptionCallback()
	{
		unregisterCallback();
	};

	bool registerCallback();

	void unregisterCallback();

	/**
	 * Change subscription instance
	 * @param instance The new multi-Subscription instance
	 */
	bool ChangeInstance(uint8_t instance)
	{
		bool ret = false;

		if (instance != get_instance()) {
			const bool registered = _registered;

			if (registered) {
				unregisterCallback();
			}

			if (_subscription.ChangeInstance(instance)) {
				ret = true;
			}

			if (registered) {
				registerCallback();
			}

		} else {
			// already on desired index
			return true;
		}

		return ret;
	}

	virtual void call() = 0;

	bool registered() const { return _registered; }

protected:

	bool _registered{false};

};

// Subscription with callback that schedules a WorkItem
class SubscriptionCallbackWorkItem : public SubscriptionCallback
{
public:
	/**
	 * Constructor
	 *
	 * @param work_item The WorkItem that will be scheduled immediately on new publications.
	 * @param meta The uORB metadata (usually from the ORB_ID() macro) for the topic.
	 * @param instance The instance for multi sub.
	 */
	SubscriptionCallbackWorkItem(px4::WorkItem *work_item, const orb_metadata *meta, uint8_t instance = 0) :
		SubscriptionCallback(meta, 0, instance),	// interval 0
		_work_item(work_item)
	{
	}

	virtual ~SubscriptionCallbackWorkItem() = default;

	void call() override
	{
		// schedule immediately if updated (queue depth or subscription interval)
		if ((_required_updates == 0)
		    || (Manager::updates_available(_subscription.get_node(), _subscription.get_last_generation()) >= _required_updates)) {
			if (updated()) {
				_work_item->ScheduleNow();
			}
		}
	}

	/**
	 * Optionally limit callback until more samples are available.
	 *
	 * @param required_updates Number of queued updates required before a callback can be called.
	 */
	void set_required_updates(uint8_t required_updates)
	{
		// TODO: constrain to queue depth?
		_required_updates = required_updates;
	}

private:
	px4::WorkItem *_work_item;

	uint8_t _required_updates{0};
};

} // namespace uORB