timer.h

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//
// Timer.h
//
// $Id: //poco/Main/Foundation/include/Foundation/Timer.h#5 $
//
// Definition of the Timer and related classes.
//
// Copyright (c) 2004, Guenter Obiltschnig/Applied Informatics.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// 3. Redistributions in any form must be accompanied by information on
//    how to obtain complete source code for this software and any
//    accompanying software that uses this software.  The source code
//    must either be included in the distribution or be available for no
//    more than the cost of distribution plus a nominal fee, and must be
//    freely redistributable under reasonable conditions.  For an
//    executable file, complete source code means the source code for all
//    modules it contains.  It does not include source code for modules or
//    files that typically accompany the major components of the operating
//    system on which the executable file runs.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//


#ifndef Foundation_Timer_INCLUDED
#define Foundation_Timer_INCLUDED


#ifndef Foundation_Foundation_INCLUDED
#include "Foundation/Foundation.h"
#endif
#ifndef Foundation_Runnable_INCLUDED
#include "Foundation/Runnable.h"
#endif
#ifndef Foundation_Mutex_INCLUDED
#include "Foundation/Mutex.h"
#endif
#ifndef Foundation_Event_INCLUDED
#include "Foundation/Event.h"
#endif


Foundation_BEGIN


class AbstractTimerCallback;


class Foundation_API Timer: protected Runnable
	/// This class implements a thread-based timer.
	/// A timer starts a thread that first waits for a given start interval.
	/// Once that interval expires, the timer callback is called repeatedly
	/// in the given periodic interval. If the interval is 0, the timer is only
	/// called once.
	/// The timer callback method can stop the timer by setting the 
	/// timer's periodic interval to 0.
	///
	/// The timer callback runs in its own thread, so multithreading
	/// issues (proper synchronization) have to be considered when writing 
	/// the callback method.
	///
	/// The exact interval at which the callback is called depends on many 
	/// factors like operating system, CPU performance and system load and
	/// may differ from the specified interval.
	///
	/// The timer thread is taken from the global default thread pool, so
	/// there is a limit to the number of available concurrent timers.
{
public:
	Timer(long startInterval = 0, long periodicInterval = 0);
		/// Creates a new timer object. StartInterval and periodicInterval
		/// are given in milliseconds. If a periodicInterval of zero is 
		/// specified, the callback will only be called once, after the
		/// startInterval expires.
		/// To start the timer, call the Start() method.

	virtual ~Timer();
		/// Stops and destroys the timer.

	void start(const AbstractTimerCallback& method);
		/// Starts the timer.
		/// Create the TimerCallback as follows:
		///     TimerCallback<MyClass> callback(*this, &MyClass::onTimer);
		///     timer.start(callback);
		
	void stop();
		/// Stops the timer. If the callback method is currently running
		/// it will be allowed to finish first.
		/// WARNING: Never call this method from within the callback method,
		/// as a deadlock would result. To stop the timer from within the
		/// callback method, call restart(0).

	void restart();
		/// Restarts the periodic interval. If the callback method is already running,
		/// nothing will happen.

	void restart(long milliseconds);
		/// Sets a new periodic interval and restarts the timer.
		/// An interval of 0 will stop the timer.

	long getStartInterval() const;
		/// Returns the start interval.

	void setStartInterval(long milliseconds);
		/// Sets the start interval. Will only be 
		/// effective before start() is called.

	long getPeriodicInterval() const;
		/// Returns the periodic interval.

	void setPeriodicInterval(long milliseconds);
		/// Sets the periodic interval. If the timer is already running
		/// the new interval will be effective when the current interval
		/// expires.

protected:
	void run();

private:
	volatile long _startInterval;
	volatile long _periodicInterval;
	Event         _wakeUp;
	Event         _done;
	AbstractTimerCallback* _pCallback;
	mutable FastMutex      _mutex;
};


class Foundation_API AbstractTimerCallback
	/// This is the base class for all instantiations of
	/// the TimerCallback template.
{
public:
	AbstractTimerCallback();
	AbstractTimerCallback(const AbstractTimerCallback& callback);
	virtual ~AbstractTimerCallback();
	
	AbstractTimerCallback& operator = (const AbstractTimerCallback& callback);

	virtual void invoke(Timer& timer) const = 0;
	virtual AbstractTimerCallback* clone() const = 0;
};


template <class C> 
class TimerCallback: public AbstractTimerCallback
	/// This template class implements an adapter that sits between
	/// a Timer and an object's method invoked by the timer.
	/// It is quite similar in concept to the RunnableAdapter, but provides 
	/// some Timer specific additional methods.
	/// See the Timer class for information on how
	/// to use this template class.
{
public:
	typedef void (C::*Callback)(Timer&);

	TimerCallback(C& object, Callback method): _pObject(&object), _method(method)
	{
	}

	TimerCallback(const TimerCallback& callback): _pObject(callback._pObject), _method(callback._method)
	{
	}

	~TimerCallback()
	{
	}

	TimerCallback& operator = (const TimerCallback& callback)
	{
		if (&callback != this)
		{
			_pObject = callback._pObject;
			_method  = callback._method;
		}
		return *this;
	}

	void invoke(Timer& timer) const
	{
		(_pObject->*_method)(timer);
	}

	AbstractTimerCallback* clone() const
	{
		return new TimerCallback(*this);
	}

private:
	TimerCallback();

	C*       _pObject;
	Callback _method;
};


Foundation_END


#endif // Foundation_Timer_INCLUDED