sl@0: /*
sl@0: * Copyright (c) 2003-2009 Nokia Corporation and/or its subsidiary(-ies).
sl@0: * All rights reserved.
sl@0: * This component and the accompanying materials are made available
sl@0: * under the terms of the License "Eclipse Public License v1.0"
sl@0: * which accompanies this distribution, and is available
sl@0: * at the URL "http://www.eclipse.org/legal/epl-v10.html".
sl@0: *
sl@0: * Initial Contributors:
sl@0: * Nokia Corporation - initial contribution.
sl@0: *
sl@0: * Contributors:
sl@0: *
sl@0: * Description: 
sl@0: * TWindowSlider class implementation
sl@0: *
sl@0: */
sl@0: 
sl@0: 
sl@0: /**
sl@0:  @file 
sl@0:  @internalComponent
sl@0: */
sl@0:  
sl@0: #ifndef __WINDOWSLIDER_H__
sl@0: #define __WINDOWSLIDER_H__
sl@0: 
sl@0: #include <e32std.h>
sl@0: 
sl@0: class TInteger; 
sl@0: /** Utility class used by our fast exponentiation routines.\n\n
sl@0:  * See HAC 14.85 for an explanation of how window sliding helps speed things up.
sl@0:  * @internalComponent
sl@0:  */
sl@0: class TWindowSlider
sl@0: {
sl@0: public:
sl@0: 	/** 
sl@0: 	 * @param aExp The exponent you are using.
sl@0: 	 * @param aWindowSize The window size.  Leave as default value for the
sl@0: 	 * constructor to pick a window size appropriate for the given aExp
sl@0: 	 * @internalComponent
sl@0: 	 */
sl@0: 	TWindowSlider(const TInteger& aExp, TUint aWindowSize=0);
sl@0: 	/**
sl@0: 	 * Finds the next "window" as defined by HAC 14.85.  The actual bitstring
sl@0: 	 * value is in iValue and it's length in iLength.  These remain valid until
sl@0: 	 * the next call to FindNextWindow()
sl@0: 	 */
sl@0: 	void FindNextWindow(TUint aBegin);
sl@0: 	inline TUint WindowSize(void) {return iSize;}
sl@0: 	inline TUint Value(void) {return iValue;}
sl@0: 	inline TUint Length(void) {return iLength;}
sl@0: 
sl@0: private:
sl@0: 	const TInteger& iExp; ///the exponent all this is being calculated on
sl@0: 	TUint iSize;  ///The size of the sliding window
sl@0: 	TUint iValue; ///the value found by the most recent FindNextWindow() call
sl@0: 	TUint iLength;///the bit length of the iValue
sl@0: };
sl@0: 
sl@0: #endif