/*

* 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);

	}