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Task.h

//
// Task.h
//
// $Id: //poco/1.4/Foundation/include/Poco/Task.h#2 $
//
// Library: Foundation
// Package: Tasks
// Module:  Tasks
//
// Definition of the Task class.
//
// 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_Task_INCLUDED
#define Foundation_Task_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Runnable.h"
#include "Poco/RefCountedObject.h"
#include "Poco/Mutex.h"
#include "Poco/Event.h"


namespace Poco {


class TaskManager;
class Notification;
class NotificationCenter;


00058 class Foundation_API Task: public Runnable, public RefCountedObject
      /// A Task is a subclass of Runnable that has a name 
      /// and supports progress reporting and cancellation.
      ///
      /// A TaskManager object can be used to take care of the
      /// lifecycle of a Task.
{
public:
      enum TaskState
      {
            TASK_IDLE,
            TASK_STARTING,
            TASK_RUNNING,
            TASK_CANCELLING,
            TASK_FINISHED
      };
      
      Task(const std::string& name);
            /// Creates the Task.

      const std::string& name() const;
            /// Returns the task's name.  
            
      float progress() const;
            /// Returns the task's progress.
            /// The value will be between 0.0 (just started)
            /// and 1.0 (completed).

      virtual void cancel();
            /// Requests the task to cancel itself. For cancellation
            /// to work, the task's runTask() method must periodically
            /// call isCancelled() and react accordingly.
            ///
            /// Can be overridden to implement custom behavior,
            /// but the base class implementation of cancel() should
            /// be called to ensure proper behavior.

      bool isCancelled() const;
            /// Returns true if cancellation of the task has been
            /// requested. 
            ///
            /// A Task's runTask() method should periodically
            /// call this method and stop whatever it is doing in an
            /// orderly way when this method returns true.

      TaskState state() const;
            /// Returns the task's current state.

      void reset();
            /// Sets the task's progress to zero and clears the
            /// cancel flag.
            
      virtual void runTask() = 0;
            /// Do whatever the task needs to do. Must
            /// be overridden by subclasses.
            
      void run();
            /// Calls the task's runTask() method and notifies the owner
            /// of the task's start and completion.

protected:
      bool sleep(long milliseconds);
            /// Suspends the current thread for the specified
            /// amount of time.
            ///
            /// If the task is cancelled while it is sleeping,
            /// sleep() will return immediately and the return
            /// value will be true. If the time interval
            /// passes without the task being cancelled, the
            /// return value is false.
            ///
            /// A Task should use this method in favor of Thread::sleep().

      void setProgress(float progress);
            /// Sets the task's progress.
            /// The value should be between 0.0 (just started)
            /// and 1.0 (completed).

      virtual void postNotification(Notification* pNf);
            /// Posts a notification to the task manager's
            /// notification center.
            ///
            /// A task can use this method to post custom
            /// notifications about its progress.

      void setOwner(TaskManager* pOwner);
            /// Sets the (optional) owner of the task.
            
      TaskManager* getOwner() const;
            /// Returns the owner of the task, which may be NULL.

      void setState(TaskState state);
            /// Sets the task's state.

      virtual ~Task();
            /// Destroys the Task.
            
private:
      Task();
      Task(const Task&);
      Task& operator = (const Task&);
      
      std::string       _name;
      TaskManager*      _pOwner;
      float             _progress;
      TaskState         _state;
      Event             _cancelEvent;
      mutable FastMutex _mutex;
      
      friend class TaskManager;
};


//
// inlines
//
00174 inline const std::string& Task::name() const
{
      return _name;
}


00180 inline float Task::progress() const
{
      FastMutex::ScopedLock lock(_mutex);

      return _progress;
}


00188 inline bool Task::isCancelled() const
{
      return _state == TASK_CANCELLING;
}


00194 inline Task::TaskState Task::state() const
{
      return _state;
}


00200 inline TaskManager* Task::getOwner() const
{
      FastMutex::ScopedLock lock(_mutex);

      return _pOwner;
}


} // namespace Poco


#endif // Foundation_Task_INCLUDED

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