--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/kernel/eka/memmodel/epoc/flexible/mmu/mrefcntobj.h	Mon Oct 19 15:55:17 2009 +0100
@@ -0,0 +1,120 @@
+// 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