/*

* Copyright (c) 2003-2009 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: 

* TWindowSlider class implementation

*

*/

/**

 @file 

 @internalComponent

*/

#ifndef __WINDOWSLIDER_H__

#define __WINDOWSLIDER_H__

#include <e32std.h>

class TInteger; 

/** Utility class used by our fast exponentiation routines.\n\n

 * See HAC 14.85 for an explanation of how window sliding helps speed things up.

 * @internalComponent

 */

class TWindowSlider

{

public:

	/** 

	 * @param aExp The exponent you are using.

	 * @param aWindowSize The window size.  Leave as default value for the

	 * constructor to pick a window size appropriate for the given aExp

	 * @internalComponent

	 */

	TWindowSlider(const TInteger& aExp, TUint aWindowSize=0);

	/**

	 * Finds the next "window" as defined by HAC 14.85.  The actual bitstring

	 * value is in iValue and it's length in iLength.  These remain valid until

	 * the next call to FindNextWindow()

	 */

	void FindNextWindow(TUint aBegin);

	inline TUint WindowSize(void) {return iSize;}

	inline TUint Value(void) {return iValue;}

	inline TUint Length(void) {return iLength;}

private:

	const TInteger& iExp; ///the exponent all this is being calculated on

	TUint iSize;  ///The size of the sliding window

	TUint iValue; ///the value found by the most recent FindNextWindow() call

	TUint iLength;///the bit length of the iValue

};

#endif