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157 lines
4.9 KiB
C++
157 lines
4.9 KiB
C++
//
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// NotificationQueue.h
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//
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// Library: Foundation
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// Package: Notifications
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// Module: NotificationQueue
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//
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// Definition of the NotificationQueue class.
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//
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// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
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// and Contributors.
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//
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// SPDX-License-Identifier: BSL-1.0
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//
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#ifndef Foundation_NotificationQueue_INCLUDED
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#define Foundation_NotificationQueue_INCLUDED
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#include <deque>
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#include "Poco/Event.h"
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#include "Poco/Foundation.h"
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#include "Poco/Mutex.h"
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#include "Poco/Notification.h"
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namespace Poco
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{
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class NotificationCenter;
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class Foundation_API NotificationQueue
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/// A NotificationQueue object provides a way to implement asynchronous
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/// notifications. This is especially useful for sending notifications
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/// from one thread to another, for example from a background thread to
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/// the main (user interface) thread.
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///
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/// The NotificationQueue can also be used to distribute work from
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/// a controlling thread to one or more worker threads. Each worker thread
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/// repeatedly calls waitDequeueNotification() and processes the
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/// returned notification. Special care must be taken when shutting
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/// down a queue with worker threads waiting for notifications.
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/// The recommended sequence to shut down and destroy the queue is to
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/// 1. set a termination flag for every worker thread
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/// 2. call the wakeUpAll() method
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/// 3. join each worker thread
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/// 4. destroy the notification queue.
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{
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public:
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NotificationQueue();
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/// Creates the NotificationQueue.
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~NotificationQueue();
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/// Destroys the NotificationQueue.
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void enqueueNotification(Notification::Ptr pNotification);
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/// Enqueues the given notification by adding it to
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/// the end of the queue (FIFO).
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/// The queue takes ownership of the notification, thus
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/// a call like
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/// notificationQueue.enqueueNotification(new MyNotification);
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/// does not result in a memory leak.
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void enqueueUrgentNotification(Notification::Ptr pNotification);
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/// Enqueues the given notification by adding it to
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/// the front of the queue (LIFO). The event therefore gets processed
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/// before all other events already in the queue.
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/// The queue takes ownership of the notification, thus
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/// a call like
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/// notificationQueue.enqueueUrgentNotification(new MyNotification);
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/// does not result in a memory leak.
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Notification * dequeueNotification();
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/// Dequeues the next pending notification.
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/// Returns 0 (null) if no notification is available.
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/// The caller gains ownership of the notification and
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/// is expected to release it when done with it.
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///
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/// It is highly recommended that the result is immediately
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/// assigned to a Notification::Ptr, to avoid potential
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/// memory management issues.
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Notification * waitDequeueNotification();
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/// Dequeues the next pending notification.
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/// If no notification is available, waits for a notification
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/// to be enqueued.
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/// The caller gains ownership of the notification and
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/// is expected to release it when done with it.
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/// This method returns 0 (null) if wakeUpWaitingThreads()
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/// has been called by another thread.
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///
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/// It is highly recommended that the result is immediately
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/// assigned to a Notification::Ptr, to avoid potential
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/// memory management issues.
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Notification * waitDequeueNotification(long milliseconds);
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/// Dequeues the next pending notification.
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/// If no notification is available, waits for a notification
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/// to be enqueued up to the specified time.
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/// Returns 0 (null) if no notification is available.
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/// The caller gains ownership of the notification and
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/// is expected to release it when done with it.
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///
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/// It is highly recommended that the result is immediately
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/// assigned to a Notification::Ptr, to avoid potential
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/// memory management issues.
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void dispatch(NotificationCenter & notificationCenter);
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/// Dispatches all queued notifications to the given
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/// notification center.
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void wakeUpAll();
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/// Wakes up all threads that wait for a notification.
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bool empty() const;
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/// Returns true iff the queue is empty.
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int size() const;
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/// Returns the number of notifications in the queue.
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void clear();
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/// Removes all notifications from the queue.
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bool hasIdleThreads() const;
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/// Returns true if the queue has at least one thread waiting
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/// for a notification.
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static NotificationQueue & defaultQueue();
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/// Returns a reference to the default
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/// NotificationQueue.
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protected:
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Notification::Ptr dequeueOne();
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private:
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typedef std::deque<Notification::Ptr> NfQueue;
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struct WaitInfo
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{
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Notification::Ptr pNf;
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Event nfAvailable;
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};
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typedef std::deque<WaitInfo *> WaitQueue;
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NfQueue _nfQueue;
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WaitQueue _waitQueue;
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mutable FastMutex _mutex;
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};
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} // namespace Poco
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#endif // Foundation_NotificationQueue_INCLUDED
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