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Timer.h

//
// Timer.h
//
// $Id: //poco/1.3/Foundation/include/Poco/Timer.h#6 $
//
// Library: Foundation
// Package: Threading
// Module:  Timer
//
// Definition of the Timer and related classes.
//
// Copyright (c) 2004-2006, 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_Timer_INCLUDED
#define Foundation_Timer_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Runnable.h"
#include "Poco/Mutex.h"
#include "Poco/Event.h"
#include "Poco/Thread.h"
#include "Poco/Timestamp.h"


namespace Poco {


class AbstractTimerCallback;
class ThreadPool;


00058 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 time needed to execute the timer callback is not included
      /// in the interval between invocations. For example, if the interval
      /// is 500 milliseconds, and the callback needs 400 milliseconds to
      /// execute, the callback function is nevertheless called every 500
      /// milliseconds. If the callback takes longer to execute than the
      /// interval, the callback function will be immediately called again
      /// once it returns.
      ///
      /// The timer thread is taken from a 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);
            ///
            /// The timer thread is taken from the global default thread pool.

      void start(const AbstractTimerCallback& method, Thread::Priority priority);
            /// Starts the timer in a thread with the given priority.
            /// Create the TimerCallback as follows:
            ///     TimerCallback<MyClass> callback(*this, &MyClass::onTimer);
            ///     timer.start(callback);
            ///
            /// The timer thread is taken from the global default thread pool.

      void start(const AbstractTimerCallback& method, ThreadPool& threadPool);
            /// Starts the timer.
            /// Create the TimerCallback as follows:
            ///     TimerCallback<MyClass> callback(*this, &MyClass::onTimer);
            ///     timer.start(callback);

      void start(const AbstractTimerCallback& method, Thread::Priority priority, ThreadPool& threadPool);
            /// Starts the timer in a thread with the given priority.
            /// 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;
      Timestamp              _nextInvocation;
      mutable FastMutex      _mutex;
      
      Timer(const Timer&);
      Timer& operator = (const Timer&);
};


00172 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> 
00189 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;
};


} // namespace Poco


#endif // Foundation_Timer_INCLUDED

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