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