/*

* Copyright (c) 2006 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "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 <hash.h>

#include <e32math.h>

#include "stunassert.h"

#include "ctransactionidgenerator.h"

// ======== MEMBER FUNCTIONS ========

// ---------------------------------------------------------------------------

// CTransactionIDGenerator::NewL

// ---------------------------------------------------------------------------

//

CTransactionIDGenerator* CTransactionIDGenerator::NewL()

    {    

    return new ( ELeave ) CTransactionIDGenerator();

    }

// ---------------------------------------------------------------------------

// CTransactionIDGenerator::CTransactionIDGenerator

// ---------------------------------------------------------------------------

//

CTransactionIDGenerator::CTransactionIDGenerator()

    {

    TUint ticks = User::TickCount();

    TTime now;

    now.UniversalTime();

    TInt64 us = now.Int64();

    iSeed = static_cast<TInt64>( ticks ) + us;

    iCounter = I64LOW( us ) - ticks;

    }

// ---------------------------------------------------------------------------

// CTransactionIDGenerator::CTransactionIDGenerator

// Dummy implementation, as copy constructor is declared private and not used.

// ---------------------------------------------------------------------------

//

CTransactionIDGenerator::CTransactionIDGenerator(

    const CTransactionIDGenerator& /*aTransactionIDGenerator*/ ) :

    CBase()

    {    

    }

// ---------------------------------------------------------------------------

// CTransactionIDGenerator::~CTransactionIDGenerator

// ---------------------------------------------------------------------------

//

CTransactionIDGenerator::~CTransactionIDGenerator()

    {

    }

// ---------------------------------------------------------------------------

// CTransactionIDGenerator::GetIDL

// CMD5 exists only during hash computing, to save memory.

// ---------------------------------------------------------------------------

//

void CTransactionIDGenerator::GetIDL( TAny* aObject,

                                      TInt aObjectSize,

                                      TNATFWUNSAFTransactionID& aTransactionID )

    {

    ++iCounter;

    HBufC8* data = BuildInputDataLC( aObject, aObjectSize );

    CMD5* md5 = CMD5::NewL();

    CleanupStack::PushL( md5 );

    TPtrC8 hash = md5->Hash( *data );

    __STUN_ASSERT_L( md5->HashSize() >= KMaxNATFWUNSAFTransactionIdLength,

                     KErrUnderflow );

    TPtrC8 ptrToHash = hash.Left(KMaxNATFWUNSAFTransactionIdLength);

    aTransactionID = ptrToHash;

    CleanupStack::PopAndDestroy( md5 );

    CleanupStack::PopAndDestroy( data );

    }

// ---------------------------------------------------------------------------

// CTransactionIDGenerator::BuildInputDataL

// ---------------------------------------------------------------------------

//

HBufC8* CTransactionIDGenerator::BuildInputDataLC( TAny* aObject,

                                                   TInt aObjectSize )

    {

    const TInt KAmountOfRandomNbrsToFill = 10;

    //Size of the input data buffer. It contains the following items:

    //

    //item                        item's size

    //----                        -----------

    //iCounter                       sizeof( iCounter )

    //aObject's state              aObjectSize    

    //checksum of this               sizeof( TUint16 )

    //clock info                  sizeof( TInt64 ) + sizeof( TUint )

    //system info                  sizeof( TUint16 ) + sizeof( TUint8 )

    //KAmountOfRandomNbrsToFill

    //random integer values     KAmountOfRandomNbrsToFill * sizeof( TInt )

    TInt dataSize = sizeof( iCounter ) + aObjectSize +

                    sizeof( TUint16 ) + sizeof( TInt64 ) + sizeof( TUint ) +

                    sizeof( TUint16 ) + sizeof( TUint8 ) +

                    KAmountOfRandomNbrsToFill * sizeof( TInt );

    HBufC8* buf = HBufC8::NewLC( dataSize );

    TPtr8 ptr = buf->Des();

    ptr.Append( reinterpret_cast<const TUint8*>( &iCounter ),

                sizeof( iCounter ) );

    ptr.Append( reinterpret_cast<const TUint8*>( aObject ), aObjectSize );

    ComputeChecksum( ptr, this, sizeof( this ) );

    AddClockInfo( ptr );

    AddSystemInfo( ptr );    

    TInt random = 0;

    TInt randomNumberSize = sizeof( random );

    while ( ptr.Size() <= ( ptr.MaxSize() - randomNumberSize ) )

        {

        random = Math::Rand( iSeed );

        ptr.Append( reinterpret_cast<const TUint8*>( &random ),

                    sizeof( random ) );

        }

    return buf;

    }

// -----------------------------------------------------------------------------

// CTransactionIDGenerator::AddClockInfo

// -----------------------------------------------------------------------------

//

void CTransactionIDGenerator::AddClockInfo( TDes8& aBuf ) const

    {

    TTime now;

    now.UniversalTime();

    TInt64 timeAsInt = now.Int64();

    aBuf.Append( reinterpret_cast<const TUint8*>( &timeAsInt ),

                 sizeof( timeAsInt ) );

    TUint ticks = User::TickCount();

    aBuf.Append( reinterpret_cast<const TUint8*>( &ticks ), sizeof( ticks ) );

    }

// -----------------------------------------------------------------------------

// CTransactionIDGenerator::AddSystemInfo

// -----------------------------------------------------------------------------

//

void CTransactionIDGenerator::AddSystemInfo( TDes8& aBuf ) const

    {

    TInt biggestBlock = 0;

    TInt totalAvailable = User::Available( biggestBlock );

    TInt value = biggestBlock + totalAvailable - User::CountAllocCells();

    ComputeChecksum( aBuf, &value, sizeof( value ) );

    TTimeIntervalSeconds inactivity = User::InactivityTime();

    if ( inactivity.Int() > 0 )

        {

        TUint8 byteVal = static_cast<TUint8>( inactivity.Int() & 0xff );

        aBuf.Append( &byteVal, sizeof( byteVal ) );

        }

    }

// ---------------------------------------------------------------------------

// CTransactionIDGenerator::ComputeChecksum

// ---------------------------------------------------------------------------

//

void CTransactionIDGenerator::ComputeChecksum( TDes8& aBuf,

                                               const TAny* aPtr,

                                               TInt aLength ) const

    {

    __STUN_ASSERT_RETURN( aPtr != NULL, KErrArgument );

    TUint16 cs = 0;

    Mem::Crc( cs, aPtr, aLength );

    aBuf.Append( reinterpret_cast<const TUint8*>( &cs ), sizeof( cs ) );

    }