// Copyright (c) 2010 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:

// dictionarycompression.cpp

//

/** 

* @file dictionarycompression.cpp

*

* @internalComponent

* @released

*/

#include "dictionarycompression.h"

RDictionaryCompressionBitStream::RDictionaryCompressionBitStream() :

	iNumberOfBitsUsedForDictionaryTokens(0),

	iOffsetToFirstBit(-1),

	iOffsetToCurrentBit(-1),

	iOffsetOnePastLastBit(-1),

	iOwnsBitBuffer(false),

	iBuffer(NULL)

	{

	}

void RDictionaryCompressionBitStream::OpenL(

				TInt aNumberOfBitsUsedForDictionaryTokens,

				TInt aOffsetToFirstBit,

				TInt aOffsetOnePastLastBit,

				TBool aTransferringOwnershipOfBuffer,

				TUint8* aBuffer)

	{

	iNumberOfBitsUsedForDictionaryTokens = aNumberOfBitsUsedForDictionaryTokens;

	iOffsetToFirstBit = aOffsetToFirstBit;

	iOffsetToCurrentBit = aOffsetToFirstBit;

	iOffsetOnePastLastBit = aOffsetOnePastLastBit;

	iOwnsBitBuffer = aTransferringOwnershipOfBuffer;

	iBuffer = aBuffer;

	assert(aBuffer!=NULL);

	assert(aOffsetToFirstBit >= 0);

	assert(aOffsetToFirstBit<=aOffsetOnePastLastBit);

	}

void RDictionaryCompressionBitStream::Close()

	{

	if (iOwnsBitBuffer)

		{

		iOwnsBitBuffer=EFalse;

		delete [] iBuffer;

		}

	iBuffer=NULL;

	}

TBool RDictionaryCompressionBitStream::EndOfStreamL() const

	{

	assert(iBuffer!=NULL);

	assert(iOffsetToFirstBit >= 0);

	assert(iOffsetToCurrentBit>=iOffsetToFirstBit);

	assert(iOffsetToCurrentBit<=iOffsetOnePastLastBit);

	return iOffsetToCurrentBit>=iOffsetOnePastLastBit;

	}

TInt RDictionaryCompressionBitStream::IndexOfDictionaryEntryL()

	{

	// increments the current bit-position if it returns a value >=0; returns KErrNotFound if the next thing in the stream is plain data rather than the index of a dictionary entry

	assert(iBuffer!=NULL);

	assert(!EndOfStreamL());

	if (!CurrentBitIsOn())

		{

		++iOffsetToCurrentBit;

		return ReadIntegerL(iNumberOfBitsUsedForDictionaryTokens);

		}

	return KErrNotFound;

	}

void RDictionaryCompressionBitStream::ReadL(Ptr8 aBufferToAppendTo,TBool aCalypsoFileFormat)

	{

	// can only be called if IndexOfDictionaryEntry returned a negative value

	assert(iBuffer!=NULL);

	assert(!EndOfStreamL());

	TInt numberOfConsecutivePrefixBits=0;

	TInt i;

	for (i=0; i<4; ++i)

		{

		const TBool currentBitIsOn=CurrentBitIsOn();

		++iOffsetToCurrentBit; // increment this regardless whether the current bit is on

		if (!currentBitIsOn)

			{

			break;

			}

		++numberOfConsecutivePrefixBits;

		}

	assert(numberOfConsecutivePrefixBits>0);

	assert(numberOfConsecutivePrefixBits<=4);

	TInt numberOfBytesToRead = numberOfConsecutivePrefixBits;

	if (numberOfConsecutivePrefixBits==3)

		{

		numberOfBytesToRead=3+ReadIntegerL(3);

		}

	else if (numberOfConsecutivePrefixBits==4)

		{

		numberOfBytesToRead=ReadIntegerL(8);

		if (!aCalypsoFileFormat)

			{

			numberOfBytesToRead+=3+(1<<3);

			}

		}

	const TInt numberOfBitsOffByteBoundary=iOffsetToCurrentBit%8;

	const TUint8* currentByte=iBuffer+(iOffsetToCurrentBit/8);

	assert((numberOfBytesToRead + aBufferToAppendTo.GetLength()) <= aBufferToAppendTo.GetMaxLength());

	for (i=0; i<numberOfBytesToRead; ++i, ++currentByte)

		{

		TUint byte=*currentByte;

		assert(numberOfBitsOffByteBoundary>=0);

		if (numberOfBitsOffByteBoundary>0)

			{

			byte>>=numberOfBitsOffByteBoundary;

			byte|=(*(currentByte+1)<<(8-numberOfBitsOffByteBoundary));

			byte&=0xff;

			}

		aBufferToAppendTo.Append(byte,1);

		}

	iOffsetToCurrentBit+=numberOfBytesToRead*8;

	assert(numberOfBitsOffByteBoundary==iOffsetToCurrentBit%8);

	}

TBool RDictionaryCompressionBitStream::CurrentBitIsOn() const

	{

	// does not increment the current bit-position

	assert(iBuffer!=NULL);

	return iBuffer[iOffsetToCurrentBit/8]&(1<<(iOffsetToCurrentBit%8));

	}

TUint RDictionaryCompressionBitStream::ReadIntegerL(TInt aNumberOfBits)

	{

	// increments the current bit-position

	assert(iBuffer!=NULL);

	TInt integer=0;

	TInt numberOfBitsLeftToRead=aNumberOfBits;

//	FOREVER

	while(1)

		{

		const TInt offsetToFirstBitToReadInCurrentByte=iOffsetToCurrentBit%8;

		const TInt offsetOnePastLastBitToReadInCurrentByte=Min(8,offsetToFirstBitToReadInCurrentByte+numberOfBitsLeftToRead);

		const TInt numberOfBitsReadFromCurrentByte=offsetOnePastLastBitToReadInCurrentByte-offsetToFirstBitToReadInCurrentByte;

		assert(numberOfBitsReadFromCurrentByte>0);

		const TUint bitsReadFromCurrentByte=((iBuffer[iOffsetToCurrentBit/8]>>offsetToFirstBitToReadInCurrentByte)&((1<<numberOfBitsReadFromCurrentByte)-1));

		integer|=(bitsReadFromCurrentByte<<(aNumberOfBits-numberOfBitsLeftToRead));

		iOffsetToCurrentBit+=numberOfBitsReadFromCurrentByte;

		numberOfBitsLeftToRead-=numberOfBitsReadFromCurrentByte;

		assert(numberOfBitsLeftToRead>=0);

		if (numberOfBitsLeftToRead<=0)

			{

			break;

			}

		}

	return integer;

	}