// Copyright (c) 2006-2009 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:

// Purpose: Kernel-side tracking of debug agent information associated

// with each process being debugged.

// 

//

#ifndef D_DEBUG_AGENT_H

#define D_DEBUG_AGENT_H

#include <rm_debug_api.h>

#include "d_driver_event_info.h"

/**

* Handles events from the kernel, filters them according to the debug agent's requests, 

* and signals these events to the user side in FIFO-style. 

* @see TKernelEventAction

* @see TEventInfo

*/

class DDebugAgent : public DBase

	{

public:

	static DDebugAgent* New(TUint64 aId);

	~DDebugAgent();

	TInt SetEventAction(Debug::TEventType aEvent, Debug::TKernelEventAction aEventAction);

	void GetEvent(TClientDataRequest<Debug::TEventInfo>* aAsyncGetValueRequest, DThread* aClientThread);

	TInt EventAction(Debug::TEventType aEvent);

	TInt CancelGetEvent(void);

	void NotifyEvent(const TDriverEventInfo& aEventInfo);

	TUint64 Id();

protected:

	DDebugAgent(TUint64 aId);

	TInt Construct();

private:

	void QueueEvent(const TDriverEventInfo& aEventInfo);

	TBool BufferEmpty() const;

	TBool BufferFull() const;

	TBool BufferCanStoreEvent() const;

	TBool BufferAtCriticalLevel() const;

	void IncrementHeadPosition(void);

	void IncrementTailPosition(void);

	TInt NumberOfEmptySlots() const;

	void LockEventQueue(void);

	void UnlockEventQueue(void);

private:

	TUint64	iId;

	Debug::TKernelEventAction iEventActions[Debug::EEventsLast];

	/**

	* Object used to write events back to DSS thread

	* @see TEventInfo

	*/

	TClientDataRequest<Debug::TEventInfo>* iRequestGetEventStatus;

	DThread* iClientThread;

	/** 

	* Ring buffer of pending events. Access to it is controlled by 

	* @see iEventQueueLock

	*/

	RArray<TDriverEventInfo> iEventQueue;

	/**

	* Ring buffer head. Points to the next empty slot in iEventQueue

	* @see iEventQueue

	*/

	TInt iHead;	

	/**

	* Ring buffer tail. Points to the oldest full slot in iEventQueue

	* @see iEventQueue 

	*/

	TInt iTail;

	/** 

	* Control access to event queue.

	* @see iEventQueue

	*/

	DSemaphore* iEventQueueLock;

	/**

	* Keeps track of how many free slots are available in the event queue.

	* @see iEventQueue

	*/

	TInt iFreeSlots;

	/**

	* Boolean to indicate if we have told the agent that we are ignoring trace events

	* @see QueueEvent

	*/

	TBool iIgnoringTrace;

	/**

	* Used to control the delivery of events to the client so that only 

	* when more requests than deliveries have taken place can we deliver the 

	* next event

	* 

	* Incremented when a request for event takes place

	* @see GetEvent

	* 

	* Decremented when an event is delivered. 

	* @see NotifyEvent

	* 

	* Cleared when event requests are cancelled

	* @see CancelGetEvent

	* 

	*/

	TInt   iEventBalance;

	/**

	* Length of kernel-event queue.

	* This is a power of two for efficiency when using the 

	* remainder operator

	* @see DDebugAgent::iEventQueue

	*/

	static const TUint KNumberOfEventsToQueue = 128;

	/**

	* This determines the number of events at which we stop accepting 

	* low priority events into the event queue.

	* @see DDebugAgent::BufferAtCriticalLevel

	* @see DDebugAgent::iEventQueue

	*/

	static const TUint KCriticalBufferSize = 64;

	/**

	* If we encounter an event that will take down the agent (eg a process critical thread crashing)

	* we use this flag to stop trying to deliver thread death notifications to it.

	*/

	TBool iAgentDying;

	};

#endif // D_DEBUG_AGENT_H