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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 {


00054 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.
            ///
            /// 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:
00139       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

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