--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/crypto/weakcryptospi/source/bigint/windowslider.cpp	Fri Nov 06 13:21:00 2009 +0200
@@ -0,0 +1,73 @@
+/*
+* 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: 
+*
+*/
+
+
+#include <bigint.h>
+#include "windowslider.h"
+#include "../common/inlines.h"
+
+TWindowSlider::TWindowSlider(const TInteger& aExp, TUint aWindowSize)
+	: iExp(aExp), iSize(aWindowSize)
+	{
+	if(iSize == 0)
+		{
+		TUint expLen = iExp.BitCount();
+		//These numbers are more or less arbitrary and can be tuned for empirical
+		//performance results if desired.  It's a trade off between amount of
+		//precomputation (more if larger iSize) and number of iterations
+		//(more if smaller iSize).  The current defaults were obtained
+		//from crypto++
+		if( expLen <= 17 )
+			iSize = 1;
+		else if( expLen <= 24 )
+			iSize = 2;
+		else if( expLen <= 70 )
+			iSize = 3;
+		else if( expLen <= 197 )
+			iSize = 4;
+		else if( expLen <= 539 )
+			iSize = 5;
+		else if( expLen <= 1434 )
+			iSize = 6;
+		else 
+			iSize = 7;
+		}
+	assert(iSize>=1 && iSize<=7);
+	}
+
+void TWindowSlider::FindNextWindow(TUint aBegin)
+	{
+	assert(iExp.Bit(aBegin)); //initial bit must be 1
+	TInt end = aBegin;
+	TUint temp = 0;
+	iValue = 0;
+	TUint j = 0;
+	for(TInt i=aBegin; i>=0 && j<iSize; i--, j++)
+		{
+		TUint saveMask = WORD_BITS - j - 1;
+		temp |= iExp.Bit(i) << saveMask;
+		if( temp & (1 << saveMask) )
+			{
+			end = i;
+			iValue |= temp; //last valid substring
+			}
+		}
+
+	iLength = aBegin - end + 1;
+	iValue >>= (WORD_BITS - iLength);
+	}
+