// Copyright (c) 2007-2009 Nokia Corporation and/or its subsidiary(-ies).

// All rights reserved.

// This component and the accompanying materials are made available

// under the terms of the License "Eclipse Public License v1.0"

// which accompanies this distribution, and is available

// at the URL "http://www.eclipse.org/legal/epl-v10.html".

//

// Initial Contributors:

// Nokia Corporation - initial contribution.

//

// Contributors:

//

// Description:

//

/**

 @file

 @internalComponent

*/

#ifndef MREFCNTOBJ_H

#define MREFCNTOBJ_H

#include <klib.h>

/**

Base class for creating reference counted objects.

This provide basic reference counting and asynchronous cleanup

for derived classes. An object whose reference count reaches zero

will be destroyed.

*/

class DReferenceCountedObject : public DBase

	{

public:

	/**

	Constructs this object with an initial reference count of one.

	*/

	DReferenceCountedObject();

	/**

	Atomically increment this object's reference count.

	A fault is raised if the count was initially <= 0.

	@pre Calling thread must be in a critical section

	@pre #iReferenceCount>0

	*/

	void Open();

	/**

	Atomically increment this object's reference count if it 

	was initially > 0.

	This is for use in situations where a reference counted object 

	is found by looking in a list, and the list may contain

	objects which have had their reference counts decremented

	to zero and are in the process of being cleaned up. A failure

	to open a reference on these objects should be taken as an

	indication that the object should be ignored, and treated as

	though it were never found.

	@return True if the count was incremented.

			False if it wasn't: because it was initially <= 0.

	@pre Calling thread must be in a critical section

	*/

	TBool TryOpen();

	/**

	Decrement this object's reference count and if it reaches zero,

	delete this object.

	@pre Calling thread must be in a critical section.

	@pre No fast mutex can be held.

	@pre No mutexes with order greater less than KMutexOrdKernelHeap can be held.

	*/

	void Close();

	/**

	Decrement this object's reference count and if this reaches zero,

	queue this object for asynchronous deletion.

	@pre Calling thread must be in a critical section.

	@pre No fast mutex can be held.

	*/

	void AsyncClose();

protected:

	/**

	Destructor which asserts in debug builds that the object's reference count is zero.

	*/

	virtual ~DReferenceCountedObject();

	/**

	Return true if the preconditions for #Close are met.

	This is for use by derived classes which overload the #Close method.

	*/

	TBool CheckCloseIsSafe();

	/**

	Return true if the preconditions for #AsyncClose are met.

	This is for use by derived classes which overload the #AsyncClose method.

	*/

	TBool CheckAsyncCloseIsSafe();

protected:

	/**

	This object's reference count. Must always be >= 0.

	*/

	TInt iReferenceCount;

	};

FORCE_INLINE DReferenceCountedObject::DReferenceCountedObject()

	: iReferenceCount(1)

	{

	}

#endif