poco/Foundation/include/Poco/TimedNotificationQueue.h

//
// TimedNotificationQueue.h
//
// $Id: //poco/1.4/Foundation/include/Poco/TimedNotificationQueue.h#1 $
//
// Library: Foundation
// Package: Notifications
// Module:  TimedNotificationQueue
//
// Definition of the TimedNotificationQueue class.
//
// Copyright (c) 2009, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
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// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_TimedNotificationQueue_INCLUDED
#define Foundation_TimedNotificationQueue_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Notification.h"
#include "Poco/Mutex.h"
#include "Poco/Event.h"
#include "Poco/Timestamp.h"
#include <map>


namespace Poco {


class Foundation_API TimedNotificationQueue
	/// A TimedNotificationQueue object provides a way to implement timed, asynchronous
	/// notifications. This is especially useful for sending notifications
	/// from one thread to another, for example from a background thread to 
	/// the main (user interface) thread. 
	///
	/// The TimedNotificationQueue is quite similar to the NotificationQueue class.
	/// The only difference to NotificationQueue is that each Notification is tagged
	/// with a Timestamp. When inserting a Notification into the queue, the
	/// Notification is inserted according to the given Timestamp, with 
	/// lower Timestamp values being inserted before higher ones.
	///
	/// Notifications are dequeued in order of their timestamps.
	///
	/// TimedNotificationQueue has some restrictions regarding multithreaded use.
	/// While multiple threads may enqueue notifications, only one thread at a
	/// time may dequeue notifications from the queue.
	///
	/// If two threads try to dequeue a notification simultaneously, the results
	/// are undefined.
{
public:
	TimedNotificationQueue();
		/// Creates the TimedNotificationQueue.

	~TimedNotificationQueue();
		/// Destroys the TimedNotificationQueue.

	void enqueueNotification(Notification::Ptr pNotification, Timestamp timestamp);
		/// Enqueues the given notification by adding it to
		/// the queue according to the given timestamp.
		/// Lower timestamp values are inserted before higher ones.
		/// The queue takes ownership of the notification, thus
		/// a call like
		///     notificationQueue.enqueueNotification(new MyNotification, someTime);
		/// does not result in a memory leak.

	Notification* dequeueNotification();
		/// Dequeues the next pending notification with a timestamp
		/// less than or equal to the current time.
		/// Returns 0 (null) if no notification is available.
		/// The caller gains ownership of the notification and
		/// is expected to release it when done with it.
		///
		/// It is highly recommended that the result is immediately
		/// assigned to a Notification::Ptr, to avoid potential
		/// memory management issues.
		
	Notification* waitDequeueNotification();
		/// Dequeues the next pending notification.
		/// If no notification is available, waits for a notification
		/// to be enqueued.
		/// The caller gains ownership of the notification and
		/// is expected to release it when done with it.
		/// This method returns 0 (null) if wakeUpWaitingThreads()
		/// has been called by another thread.
		///
		/// It is highly recommended that the result is immediately
		/// assigned to a Notification::Ptr, to avoid potential
		/// memory management issues.

	Notification* waitDequeueNotification(long milliseconds);
		/// Dequeues the next pending notification.
		/// If no notification is available, waits for a notification
		/// to be enqueued up to the specified time.
		/// Returns 0 (null) if no notification is available.
		/// The caller gains ownership of the notification and
		/// is expected to release it when done with it.
		///
		/// It is highly recommended that the result is immediately
		/// assigned to a Notification::Ptr, to avoid potential
		/// memory management issues.

	bool empty() const;
		/// Returns true iff the queue is empty.
		
	int size() const;
		/// Returns the number of notifications in the queue.

	void clear();
		/// Removes all notifications from the queue.
		///
		/// Calling clear() while another thread executes one of
		/// the dequeue member functions will result in undefined
		/// behavior.

protected:
	typedef std::multimap<Timestamp, Notification::Ptr> NfQueue;
	Notification::Ptr dequeueOne(NfQueue::iterator& it);
	bool wait(Timestamp::TimeDiff interval);
	
private:
	NfQueue _nfQueue;
	Event _nfAvailable;
	mutable FastMutex _mutex;
};


} // namespace Poco


#endif // Foundation_TimedNotificationQueue_INCLUDED