/*

* Copyright (c) 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: 

*

*/

#ifndef __DMSGQUEUE_H_

#define __DMSGQUEUE_H_

#include <e32def.h>             // For TUint32

#include <e32cmn.h>             // For TDesC8

#include <klib.h>        // For DBase

class NFastMutex;

/*

* Ring buffer for messages.

*/

NONSHARABLE_CLASS( DMsgQueue ) : public DBase

    {

    public:

        /*

        * Constructor

        * @param aSize, maximum size of the queue.

        */

        DMsgQueue( const TUint16 aSize );

        /*

        * Destructor

        */

        ~DMsgQueue();

        /* 

        * Adds the message in the end of the ringbuffer queue.

        * If queue overflows throws fault.

        * @param aMessage, message to be added

        */

        void Add( const TDesC8& aMessage );

        /* 

        * Returns the count of the messages in the queue

        * @return count of the messages in the queue.

        */

        TUint16 Count();

        /*

        * Returns a reference to first message ( iOutputIndex ) in the ring buffer.

        * If queue is messed up throws fault.

        * NOTE! Responsibility to deallocate the memory is transferred to caller.

        * @return reference to message

        */

        TDes8& Get();

        /*

        * Rolls back the ringbuffer.

        * Message must be the last message get from the queue.

        * NOTE! Responsibility to deallocate the memory is transferred to queue.

        * @param aMsgToRoll

        */

        void RollBack( const TDesC8& aMsgToRoll );

    private:

        // Added convention:

        // Prefix "iSh" means shared member variable

        // Prefix "gSh" means shared global variable

        // Index where to add next message pointer.

        TUint16     iShInputIndex;

        // Index where to get next message pointer.

        TUint16     iShOutputIndex;

        // Count of items in the array.

        TUint16     iShCount;

        // Size of the ring buffer. Written only once in constructor.

        TUint16     iSize;

        // Owned

        NFastMutex* iQueueMutex;

        // Owned, memory allocated for the buffer.

        TDes8**     iShRingBuffer;

    };

#endif /* __DMSGQUEUE_H_ */