Source: ../../ospf/delay_queue.hh

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// -*- c-basic-offset: 4; tab-width: 8; indent-tabs-mode: t -*-
// vim:set sts=4 ts=8:

// Copyright (c) 2001-2005 International Computer Science Institute
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software")
// to deal in the Software without restriction, subject to the conditions
// listed in the XORP LICENSE file. These conditions include: you must
// preserve this copyright notice, and you cannot mention the copyright
// holders in advertising related to the Software without their permission.
// The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This
// notice is a summary of the XORP LICENSE file; the license in that file is
// legally binding.

// $XORP: xorp/ospf/delay_queue.hh,v 1.5 2005/09/05 01:04:25 atanu Exp $

#ifndef __OSPF_DELAY_QUEUE_HH__
#define __OSPF_DELAY_QUEUE_HH__

/**
 * Entries can be added to the queue at any rate. The callback is
 * invoked at the specified period to remove an entry from the queue.
 */
template <typename _Entry>
class DelayQueue {
public:
    typedef typename XorpCallback1<void, _Entry>::RefPtr DelayCallback;

    DelayQueue(EventLoop& eventloop, uint32_t delay, DelayCallback forward)
	: _eventloop(eventloop), _delay(delay), _forward(forward)
    {}

    /**
     * Add an entry to the queue. If the entry is already on the queue
     * it is not added again.
     */
    void add(_Entry entry);

    /**
     * Start the timer running but don't add anything to the queue.
     */
    void fire();

private:
    EventLoop& _eventloop;
    deque<_Entry> _queue;
    const uint32_t _delay;	// Delay in seconds.
    DelayCallback _forward;	// Invoked to forward an entry from the queue.
    XorpTimer	_timer;		// Timer that services the queue.

    /**
     * Invoked from the timer to take the next entry from the queue.
     */
    void next();
};

template <typename _Entry>
void
DelayQueue<_Entry>::add(_Entry entry)
{
    // If this entry is already on the queue just return.
    if (_queue.end() != find(_queue.begin(), _queue.end(), entry))
	return;

    // If the timer is running push this entry to the back of the
    // queue and return.
    if (_timer.scheduled()) {
	_queue.push_back(entry);
	return;
    }

    // If the timer isn't running then we have been idle for more than
    // delay seconds. Forward this entry immediately and start the
    // timer. Start the timer first in case this code is re-entered.

    _timer = _eventloop.new_oneoff_after(TimeVal(_delay, 0),
					 callback(this, &DelayQueue::next));

    _forward->dispatch(entry);
}

template <typename _Entry>
void
DelayQueue<_Entry>::fire()
{
    if (_timer.scheduled())
	return;
    
    _timer = _eventloop.new_oneoff_after(TimeVal(_delay, 0),
					 callback(this, &DelayQueue::next));
}

template <typename _Entry>
void
DelayQueue<_Entry>::next()
{
    if (_queue.empty())
	return;

    _timer = _eventloop.new_oneoff_after(TimeVal(_delay, 0),
					 callback(this, &DelayQueue::next));
    
    _Entry entry = _queue.front();
    _queue.pop_front();

    _forward->dispatch(entry);
}

#endif // __OSPF_DELAY_QUEUE_HH__