// Copyright (c) 2010 Nokia Corporation and/or its subsidiary(-ies).+
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// All rights reserved.+
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// This component and the accompanying materials are made available+
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// under the terms of "Eclipse Public License v1.0"+
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// which accompanies this distribution, and is available+
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// at the URL "http://www.eclipse.org/legal/epl-v10.html".+
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//+
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// Initial Contributors:+
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// Nokia Corporation - initial contribution.+
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//+
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// Contributors:+
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//+
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// Description:+
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// dictionarycompression.cpp+
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//+
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/** +
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* @file dictionarycompression.cpp+
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*+
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* @internalComponent+
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* @released+
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*/+
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+
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#include "dictionarycompression.h"+
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+
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RDictionaryCompressionBitStream::RDictionaryCompressionBitStream() :+
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	iNumberOfBitsUsedForDictionaryTokens(0),+
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	iOffsetToFirstBit(-1),+
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	iOffsetToCurrentBit(-1),+
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	iOffsetOnePastLastBit(-1),+
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	iOwnsBitBuffer(false),+
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	iBuffer(NULL)+
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	{+
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	}+
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+
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void RDictionaryCompressionBitStream::OpenL(+
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				TInt aNumberOfBitsUsedForDictionaryTokens,+
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				TInt aOffsetToFirstBit,+
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				TInt aOffsetOnePastLastBit,+
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				TBool aTransferringOwnershipOfBuffer,+
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				TUint8* aBuffer)+
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	{+
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	iNumberOfBitsUsedForDictionaryTokens = aNumberOfBitsUsedForDictionaryTokens;+
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	iOffsetToFirstBit = aOffsetToFirstBit;+
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	iOffsetToCurrentBit = aOffsetToFirstBit;+
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	iOffsetOnePastLastBit = aOffsetOnePastLastBit;+
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	iOwnsBitBuffer = aTransferringOwnershipOfBuffer;+
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	iBuffer = aBuffer;+
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+
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	assert(aBuffer!=NULL);+
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	assert(aOffsetToFirstBit >= 0);+
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	assert(aOffsetToFirstBit<=aOffsetOnePastLastBit);+
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	}+
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+
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void RDictionaryCompressionBitStream::Close()+
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	{+
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	if (iOwnsBitBuffer)+
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		{+
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		iOwnsBitBuffer=EFalse;+
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		delete [] iBuffer;+
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		}+
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	iBuffer=NULL;+
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	}+
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+
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TBool RDictionaryCompressionBitStream::EndOfStreamL() const+
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	{+
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	assert(iBuffer!=NULL);+
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	assert(iOffsetToFirstBit >= 0);+
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	assert(iOffsetToCurrentBit>=iOffsetToFirstBit);+
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	assert(iOffsetToCurrentBit<=iOffsetOnePastLastBit);+
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	return iOffsetToCurrentBit>=iOffsetOnePastLastBit;+
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	}+
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+
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TInt RDictionaryCompressionBitStream::IndexOfDictionaryEntryL()+
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	{+
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	// 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+
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	assert(iBuffer!=NULL);+
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	assert(!EndOfStreamL());+
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	if (!CurrentBitIsOn())+
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		{+
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		++iOffsetToCurrentBit;+
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		return ReadIntegerL(iNumberOfBitsUsedForDictionaryTokens);+
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		}+
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	return KErrNotFound;+
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	}+
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+
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void RDictionaryCompressionBitStream::ReadL(Ptr8 aBufferToAppendTo,TBool aCalypsoFileFormat)+
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	{+
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	// can only be called if IndexOfDictionaryEntry returned a negative value+
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	assert(iBuffer!=NULL);+
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	assert(!EndOfStreamL());+
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	TInt numberOfConsecutivePrefixBits=0;+
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	TInt i;+
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	for (i=0; i<4; ++i)+
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		{+
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		const TBool currentBitIsOn=CurrentBitIsOn();+
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		++iOffsetToCurrentBit; // increment this regardless whether the current bit is on+
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		if (!currentBitIsOn)+
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			{+
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			break;+
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			}+
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		++numberOfConsecutivePrefixBits;+
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		}+
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	assert(numberOfConsecutivePrefixBits>0);+
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	assert(numberOfConsecutivePrefixBits<=4);+
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	TInt numberOfBytesToRead = numberOfConsecutivePrefixBits;+
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	if (numberOfConsecutivePrefixBits==3)+
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		{+
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		numberOfBytesToRead=3+ReadIntegerL(3);+
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		}+
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	else if (numberOfConsecutivePrefixBits==4)+
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		{+
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		numberOfBytesToRead=ReadIntegerL(8);+
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		if (!aCalypsoFileFormat)+
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			{+
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			numberOfBytesToRead+=3+(1<<3);+
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			}+
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		}+
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+
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	const TInt numberOfBitsOffByteBoundary=iOffsetToCurrentBit%8;+
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	const TUint8* currentByte=iBuffer+(iOffsetToCurrentBit/8);+
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	assert((numberOfBytesToRead + aBufferToAppendTo.GetLength()) <= aBufferToAppendTo.GetMaxLength());+
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	for (i=0; i<numberOfBytesToRead; ++i, ++currentByte)+
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		{+
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		TUint byte=*currentByte;+
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		assert(numberOfBitsOffByteBoundary>=0);+
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		if (numberOfBitsOffByteBoundary>0)+
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			{+
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			byte>>=numberOfBitsOffByteBoundary;+
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			byte|=(*(currentByte+1)<<(8-numberOfBitsOffByteBoundary));+
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			byte&=0xff;+
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			}+
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		aBufferToAppendTo.Append(byte,1);+
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		}+
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	iOffsetToCurrentBit+=numberOfBytesToRead*8;+
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	assert(numberOfBitsOffByteBoundary==iOffsetToCurrentBit%8);+
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	}+
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+
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TBool RDictionaryCompressionBitStream::CurrentBitIsOn() const+
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	{+
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	// does not increment the current bit-position+
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	assert(iBuffer!=NULL);+
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	return iBuffer[iOffsetToCurrentBit/8]&(1<<(iOffsetToCurrentBit%8));+
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	}+
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+
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TUint RDictionaryCompressionBitStream::ReadIntegerL(TInt aNumberOfBits)+
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	{+
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	// increments the current bit-position+
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	assert(iBuffer!=NULL);+
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	TInt integer=0;+
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	TInt numberOfBitsLeftToRead=aNumberOfBits;+
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//	FOREVER+
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	while(1)+
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		{+
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		const TInt offsetToFirstBitToReadInCurrentByte=iOffsetToCurrentBit%8;+
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		const TInt offsetOnePastLastBitToReadInCurrentByte=Min(8,offsetToFirstBitToReadInCurrentByte+numberOfBitsLeftToRead);+
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		const TInt numberOfBitsReadFromCurrentByte=offsetOnePastLastBitToReadInCurrentByte-offsetToFirstBitToReadInCurrentByte;+
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		assert(numberOfBitsReadFromCurrentByte>0);+
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		const TUint bitsReadFromCurrentByte=((iBuffer[iOffsetToCurrentBit/8]>>offsetToFirstBitToReadInCurrentByte)&((1<<numberOfBitsReadFromCurrentByte)-1));+
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		integer|=(bitsReadFromCurrentByte<<(aNumberOfBits-numberOfBitsLeftToRead));+
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		iOffsetToCurrentBit+=numberOfBitsReadFromCurrentByte;+
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		numberOfBitsLeftToRead-=numberOfBitsReadFromCurrentByte;+
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		assert(numberOfBitsLeftToRead>=0);+
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		if (numberOfBitsLeftToRead<=0)+
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			{+
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			break;+
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			}+
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		}+
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	return integer;+
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	}+
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+
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