PX4-Autopilot/src/modules/uORB/Subscription.hpp

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/**
 * @file Subscription.h
 *
 */

#pragma once

#include <assert.h>

#include <uORB/uORB.h>
#include <containers/List.hpp>

namespace uORB
{

/**
 * Base subscription warapper class, used in list traversal
 * of various subscriptions.
 */
class __EXPORT SubscriptionBase
{
public:
// methods

	/**
	 * Constructor
	 *
	 * @param meta The uORB metadata (usually from the ORB_ID()
	 * 	macro) for the topic.
	 *
	 * @param interval  The minimum interval in milliseconds
	 * 	between updates
	 */
	SubscriptionBase(const struct orb_metadata *meta,
		unsigned interval=0) :
		_meta(meta),
		_handle() {
		setHandle(orb_subscribe(getMeta()));
		orb_set_interval(getHandle(), interval);
	}

	/**
	 * Check if there is a new update.
	 * */
	bool updated() {
		bool isUpdated = false;
		orb_check(_handle, &isUpdated);
		return isUpdated;
	}

	/**
	 * Update the struct
	 * @param data The uORB message struct we are updating.
	 */
	void update(void * data) {
		if (updated()) {
			orb_copy(_meta, _handle, data);
		}
	}

	/**
	 * Deconstructor
	 */
	virtual ~SubscriptionBase() {
		orb_unsubscribe(_handle);
	}
// accessors
	const struct orb_metadata *getMeta() { return _meta; }
	int getHandle() { return _handle; }
protected:
// accessors
	void setHandle(int handle) { _handle = handle; }
// attributes
	const struct orb_metadata *_meta;
	int _handle;
};

/**
 * alias class name so it is clear that the base class
 */
typedef SubscriptionBase SubscriptionTiny;

/**
 * The publication base class as a list node.
 */
class __EXPORT SubscriptionNode :

	public SubscriptionBase,
	public ListNode<SubscriptionNode *>
{
public:
	/**
	 * Constructor
	 *
	 *
	 * @param meta The uORB metadata (usually from the ORB_ID()
	 * 	macro) for the topic.
	 * @param interval  The minimum interval in milliseconds
	 * 	between updates
	 * @param list 	A pointer to a list of subscriptions
	 * 	that this should be appended to.
	 */
	SubscriptionNode(const struct orb_metadata *meta,
		unsigned interval=0,
		List<SubscriptionNode *> * list=nullptr) :
		SubscriptionBase(meta, interval),
		_interval(interval) {
		if (list != nullptr) list->add(this);
	}

	/**
	 * This function is the callback for list traversal
	 * updates, a child class must implement it.
	 */
	virtual void update() = 0;
// accessors
	unsigned getInterval() { return _interval; }
protected:
// attributes
	unsigned _interval;

};

/**
 * Subscription wrapper class
 */
template<class T>
class __EXPORT Subscription :
	public T, // this must be first!
	public SubscriptionNode
{
public:
	/**
	 * Constructor
	 *
	 * @param meta The uORB metadata (usually from
	 * 	the ORB_ID() macro) for the topic.
	 * @param interval  The minimum interval in milliseconds
	 * 	between updates
	 * @param list A list interface for adding to
	 * 	list during construction
	 */
	Subscription(const struct orb_metadata *meta,
		unsigned interval=0,
		List<SubscriptionNode *> * list=nullptr);
	/**
	 * Deconstructor
	 */
	virtual ~Subscription();


	/**
	 * Create an update function that uses the embedded struct.
	 */
	void update() {
		SubscriptionBase::update(getDataVoidPtr());
	}

	/*
	 * XXX
	 * This function gets the T struct, assuming
	 * the struct is the first base class, this
	 * should use dynamic cast, but doesn't
	 * seem to be available
	 */
	void *getDataVoidPtr();
	T getData();
};

} // namespace uORB