// Copyright (c) 2001-2009 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 <e32std.h>

#include <baflpan.h>

#include "BADICTIONARYCOMPRESSION.H"

RDictionaryCompressionBitStream::RDictionaryCompressionBitStream() :

	iNumberOfBitsUsedForDictionaryTokens(0),

	iOffsetToFirstBit(-1),

	iOffsetToCurrentBit(-1),

	iOffsetOnePastLastBit(-1),

	iOwnsBitBuffer(EFalse),

	iBuffer(NULL),

	iAssertObj()

	{

	}

void RDictionaryCompressionBitStream::OpenL(

				TInt aNumberOfBitsUsedForDictionaryTokens,

				TInt aOffsetToFirstBit,

				TInt aOffsetOnePastLastBit,

				TBool aTransferringOwnershipOfBuffer,

				TUint8* aBuffer,

				const TBaAssert& aAssertObj)

	{

	iNumberOfBitsUsedForDictionaryTokens = aNumberOfBitsUsedForDictionaryTokens;

	iOffsetToFirstBit = aOffsetToFirstBit;

	iOffsetToCurrentBit = aOffsetToFirstBit;

	iOffsetOnePastLastBit = aOffsetOnePastLastBit;

	iOwnsBitBuffer = aTransferringOwnershipOfBuffer;

	iBuffer = aBuffer;

	iAssertObj = aAssertObj;

	iAssertObj.AssertDebL(aBuffer!=NULL,EBafPanicNullPointer);

	iAssertObj.AssertDebL(aOffsetToFirstBit>=0,EBafPanicNegativeOffsetToFirstBit1);

	iAssertObj.AssertDebL(aOffsetToFirstBit<=aOffsetOnePastLastBit,EBafPanicNegativeLengthOfBitBuffer);

	}

void RDictionaryCompressionBitStream::Close()

	{

	if (iOwnsBitBuffer)

		{

		iOwnsBitBuffer=EFalse;

		delete [] iBuffer;

		}

	iBuffer=NULL;

	}

TBool RDictionaryCompressionBitStream::EndOfStreamL() const

	{

	__ASSERT_DEBUG(iBuffer!=NULL,Panic(EBafPanicNotConstructed1));

	iAssertObj.AssertDebL(iOffsetToFirstBit>=0,EBafPanicNegativeOffsetToFirstBit2);

	iAssertObj.AssertDebL(iOffsetToCurrentBit>=iOffsetToFirstBit,EBafPanicBadCurrentBitPosition1);

	iAssertObj.AssertDebL(iOffsetToCurrentBit<=iOffsetOnePastLastBit,EBafPanicBadCurrentBitPosition2);

	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_DEBUG(iBuffer!=NULL,Panic(EBafPanicNotConstructed2));

	iAssertObj.AssertDebL(!EndOfStreamL(),EBafPanicEndOfStream1);

	if (!CurrentBitIsOn())

		{

		++iOffsetToCurrentBit;

		return ReadIntegerL(iNumberOfBitsUsedForDictionaryTokens);

		}

	return KErrNotFound;

	}

void RDictionaryCompressionBitStream::ReadL(TDes8& aBufferToAppendTo,TBool aCalypsoFileFormat)

	{

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

	__ASSERT_DEBUG(iBuffer!=NULL,Panic(EBafPanicNotConstructed3));

	iAssertObj.AssertDebL(!EndOfStreamL(),EBafPanicEndOfStream2);

	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;

		}

	iAssertObj.AssertDebL(numberOfConsecutivePrefixBits>0,EBafPanicBadNumberOfConsecutivePrefixBits1);

	iAssertObj.AssertDebL(numberOfConsecutivePrefixBits<=4,EBafPanicBadNumberOfConsecutivePrefixBits2);

	TInt numberOfBytesToRead;

	if (numberOfConsecutivePrefixBits==3)

		{

		numberOfBytesToRead=3+ReadIntegerL(3);

		}

	else if (numberOfConsecutivePrefixBits==4)

		{

		numberOfBytesToRead=ReadIntegerL(8);

		if (!aCalypsoFileFormat)

			{

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

			}

		}

	else

		{

		numberOfBytesToRead=numberOfConsecutivePrefixBits;

		}

	const TInt numberOfBitsOffByteBoundary=iOffsetToCurrentBit%8;

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

	iAssertObj.AssertDebL(

		(numberOfBytesToRead + aBufferToAppendTo.Length()) <= aBufferToAppendTo.MaxLength(),

		EBafPanicBufLength);

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

		{

		TUint byte=*currentByte;

		iAssertObj.AssertDebL(numberOfBitsOffByteBoundary>=0,EBafPanicBadNumberOfBitsOffByteBoundary1);

		if (numberOfBitsOffByteBoundary>0)

			{

			byte>>=numberOfBitsOffByteBoundary;

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

			byte&=0xff;

			}

		aBufferToAppendTo.Append(byte);

		}

	iOffsetToCurrentBit+=numberOfBytesToRead*8;

	iAssertObj.AssertDebL(numberOfBitsOffByteBoundary==iOffsetToCurrentBit%8,EBafPanicBadNumberOfBitsOffByteBoundary2);

	}

TBool RDictionaryCompressionBitStream::CurrentBitIsOn() const

	{

	// does not increment the current bit-position

	__ASSERT_DEBUG(iBuffer!=NULL,Panic(EBafPanicNotConstructed4));

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

	}

TUint RDictionaryCompressionBitStream::ReadIntegerL(TInt aNumberOfBits)

	{

	// increments the current bit-position

	__ASSERT_DEBUG(iBuffer!=NULL,Panic(EBafPanicNotConstructed5));

	TInt integer=0;

	TInt numberOfBitsLeftToRead=aNumberOfBits;

	FOREVER

		{

		const TInt offsetToFirstBitToReadInCurrentByte=iOffsetToCurrentBit%8;

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

		const TInt numberOfBitsReadFromCurrentByte=offsetOnePastLastBitToReadInCurrentByte-offsetToFirstBitToReadInCurrentByte;

		iAssertObj.AssertDebL(numberOfBitsReadFromCurrentByte>0,EBafPanicBadNumberOfBitsReadFromCurrentByte);

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

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

		iOffsetToCurrentBit+=numberOfBitsReadFromCurrentByte;

		numberOfBitsLeftToRead-=numberOfBitsReadFromCurrentByte;

		iAssertObj.AssertDebL(numberOfBitsLeftToRead>=0,EBafPanicBadNumberOfBitsLeftToRead);

		if (numberOfBitsLeftToRead<=0)

			{

			break;

			}

		}

	return integer;

	}