diff -r 000000000000 -r 2c201484c85f crypto/weakcrypto/source/bigint/windowslider.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/crypto/weakcrypto/source/bigint/windowslider.h Wed Jul 08 11:25:26 2009 +0100 @@ -0,0 +1,64 @@ +/* +* 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 + +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