/*

 * Copyright (c) 2002-2009 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 "arc4.h"

 #include "../common/inlines.h"

 #include <e32base.h>

 #include <cryptostrength.h>

 #ifdef SYMBIAN_ENABLE_SPLIT_HEADERS

 /** The size of the substitution box (i.e. lookup table) in bytes. */

 const TInt KSBoxSize = 256;

 #endif

 inline TUint8 CARC4::GenerateByte()

 	{

 	TUint8 a = iState[ix];

 	iy = (TUint8)((iy + a) & 0xff);

 	TUint8 b = iState[iy];

 	iState[ix] = b;

 	iState[iy] = a;

 	ix = (TUint8)((ix + 1) & 0xff);

 	return (iState[(a + b) & 0xff]);

 	}

 CARC4::CARC4(const TDesC8& aKey, TUint aDiscardBytes)

 	: ix(1), iy(0), iDiscardBytes(aDiscardBytes)

 	{

 	iKey.Copy(aKey);

 	GenerateSBox();

 	}

 EXPORT_C CARC4* CARC4::NewL(const TDesC8& aKey, TUint aDiscardBytes)

 	{

 	CARC4* self = NewLC(aKey, aDiscardBytes);

 	CleanupStack::Pop(self);

 	return self;

 	}

 EXPORT_C CARC4* CARC4::NewLC(const TDesC8& aKey, TUint aDiscardBytes)

 	{

 	CARC4* self = new(ELeave)CARC4(aKey, aDiscardBytes);

 	CleanupStack::PushL(self);

 	TCrypto::IsSymmetricWeakEnoughL(BytesToBits(aKey.Size()));

 	return self;

 	}

 void CARC4::DoProcess(TDes8& aData)

 	{

 	TInt blockLen = aData.Size();

 	if (blockLen > 0)

 		{

 		TUint8* blockPtr = (TUint8*)&aData[0];	

 		do

 			{

 			*blockPtr++ ^= GenerateByte();

 			} 

 		while (--blockLen);

 		}

 	}

 void CARC4::Reset()

 	{

 	ix = 1;

 	iy = 0;

 	GenerateSBox();

 	}

 TInt CARC4::KeySize() const

 	{

 	return (iKey.Size());

 	}

 void CARC4::DiscardBytes(TInt aDiscardBytes)

 	{	

 	if (aDiscardBytes > 0)

 		{

 		do

 			{

 			GenerateByte();

 			}

 		while(--aDiscardBytes);

 		}

 	}

 void CARC4::GenerateSBox(void)

 	{

 	TUint keyBytes = iKey.Size();

 	TInt i = 0;

 	for (; i < KSBoxSize; i++)

 		iState[i] = (TUint8)i;

 	TUint keyIndex = 0, stateIndex = 0;

 	i = 0;

 	for (; i < KSBoxSize; i++)

 		{

 		TUint a = iState[i];

 		stateIndex += iKey[keyIndex] + a;

 		stateIndex &= 0xff;

 		iState[i] = iState[stateIndex];

 		iState[stateIndex] = (TUint8)a;

 		if (++keyIndex >= (TUint)keyBytes)

 			keyIndex = 0;

 		}

 	DiscardBytes(iDiscardBytes);

 	}