source: XMLIO_V2/external/src/POCO/Foundation.save/Poco/PriorityNotificationQueue.h @ 80

//
// PriorityNotificationQueue.h
//
// $Id: //poco/1.3/Foundation/include/Poco/PriorityNotificationQueue.h#3 $
//
// Library: Foundation
// Package: Notifications
// Module:  PriorityNotificationQueue
//
// Definition of the PriorityNotificationQueue 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
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_PriorityNotificationQueue_INCLUDED
#define Foundation_PriorityNotificationQueue_INCLUDED


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


namespace Poco {


class NotificationCenter;


class Foundation_API PriorityNotificationQueue
        /// A PriorityNotificationQueue object provides a way to implement 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 PriorityNotificationQueue is quite similar to the NotificationQueue class.
        /// The only difference to NotificationQueue is that each Notification is tagged
        /// with a priority value. When inserting a Notification into the queue, the
        /// Notification is inserted according to the given priority value, with 
        /// lower priority values being inserted before higher priority
        /// values. Therefore, the lower the numerical priority value, the higher
        /// the actual notification priority. 
        ///
        /// Notifications are dequeued in order of their priority.
        /// 
        /// The PriorityNotificationQueue can also be used to distribute work from
        /// a controlling thread to one or more worker threads. Each worker thread
        /// repeatedly calls waitDequeueNotification() and processes the
        /// returned notification. Special care must be taken when shutting
        /// down a queue with worker threads waiting for notifications.
        /// The recommended sequence to shut down and destroy the queue is to
        ///   1. set a termination flag for every worker thread
        ///   2. call the wakeUpAll() method
        ///   3. join each worker thread
        ///   4. destroy the notification queue.
{
public:
        PriorityNotificationQueue();
                /// Creates the PriorityNotificationQueue.

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

        void enqueueNotification(Notification::Ptr pNotification, int priority);
                /// Enqueues the given notification by adding it to
                /// the queue according to the given priority.
                /// Lower priority values are inserted before higher priority values.
                /// The queue takes ownership of the notification, thus
                /// a call like
                ///     notificationQueue.enqueueNotification(new MyNotification, 1);
                /// does not result in a memory leak.
                
        Notification* dequeueNotification();
                /// Dequeues the next pending notification.
                /// 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 wakeUpAll()
                /// 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.

        void dispatch(NotificationCenter& notificationCenter);
                /// Dispatches all queued notifications to the given
                /// notification center.

        void wakeUpAll();
                /// Wakes up all threads that wait for a notification.
        
        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.
                
        bool hasIdleThreads() const;    
                /// Returns true if the queue has at least one thread waiting 
                /// for a notification.
                
        static PriorityNotificationQueue& defaultQueue();
                /// Returns a reference to the default
                /// PriorityNotificationQueue.

protected:
        Notification::Ptr dequeueOne();
        
private:
        typedef std::multimap<int, Notification::Ptr> NfQueue;
        struct WaitInfo
        {
                Notification::Ptr pNf;
                Event nfAvailable;
        };
        typedef std::deque<WaitInfo*> WaitQueue;

        NfQueue           _nfQueue;
        WaitQueue         _waitQueue;
        mutable FastMutex _mutex;
};


} // namespace Poco


#endif // Foundation_PriorityNotificationQueue_INCLUDED