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//
// TimedNotificationQueue.h
//
// Library: Foundation
// Package: Notifications
// Module: TimedNotificationQueue
//
// Definition of the TimedNotificationQueue class.
//
// Copyright (c) 2009, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#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 "Poco/Clock.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.
///
/// The Timestamp is converted to an equivalent Clock value.
void enqueueNotification(Notification::Ptr pNotification, Clock clock);
/// Enqueues the given notification by adding it to
/// the queue according to the given clock value.
/// Lower clock 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:
typedef std::multimap<Clock, Notification::Ptr> NfQueue;
Notification::Ptr dequeueOne(NfQueue::iterator& it);
bool wait(Clock::ClockDiff interval);
private:
NfQueue _nfQueue;
Event _nfAvailable;
mutable FastMutex _mutex;
};
} // namespace Poco
#endif // Foundation_TimedNotificationQueue_INCLUDED
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