AOO410/main/svtools/source/filter/igif/decode.cxx

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 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
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// MARKER(update_precomp.py): autogen include statement, do not remove
#include "precompiled_svtools.hxx"

#include "decode.hxx"

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

struct GIFLZWTableEntry
{
	GIFLZWTableEntry*	pPrev;
	GIFLZWTableEntry*	pFirst;
	sal_uInt8				nData;
};

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

GIFLZWDecompressor::GIFLZWDecompressor( sal_uInt8 cDataSize ) :
			nInputBitsBuf		( 0 ),
			nOutBufDataLen		( 0 ),
			nInputBitsBufSize	( 0 ),
			bEOIFound			( sal_False ),
			nDataSize			( cDataSize )
{
	pOutBuf	= new sal_uInt8[ 4096 ];

	nClearCode = 1 << nDataSize;
	nEOICode = nClearCode + 1;
	nTableSize = nEOICode + 1;
	nCodeSize = nDataSize + 1;
	nOldCode = 0xffff;
	pOutBufData = pOutBuf + 4096;

	pTable = new GIFLZWTableEntry[ 4098 ];

	for( sal_uInt16 i = 0; i < nTableSize; i++ )
	{
		pTable[i].pPrev = NULL;
		pTable[i].pFirst = pTable + i;
		pTable[i].nData = (sal_uInt8) i;
	}
}

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

GIFLZWDecompressor::~GIFLZWDecompressor()
{
	delete[] pOutBuf;
	delete[] pTable;
}

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

HPBYTE GIFLZWDecompressor::DecompressBlock( HPBYTE pSrc, sal_uInt8 cBufSize,
											sal_uLong& rCount, sal_Bool& rEOI )
{
	sal_uLong	nTargetSize = 4096;
	sal_uLong	nCount = 0;
	HPBYTE	pTarget = (HPBYTE) rtl_allocateMemory( nTargetSize );
	HPBYTE	pTmpTarget = pTarget;

	nBlockBufSize = cBufSize;
	nBlockBufPos = 0;
	pBlockBuf = pSrc;

	while( ProcessOneCode() )
	{
		nCount += nOutBufDataLen;

		if( nCount > nTargetSize )
		{
			sal_uLong	nNewSize = nTargetSize << 1;
			sal_uLong	nOffset = pTmpTarget - pTarget;
			HPBYTE	pTmp = (HPBYTE) rtl_allocateMemory( nNewSize );

			memcpy( pTmp, pTarget, nTargetSize );
			rtl_freeMemory( pTarget );

			nTargetSize = nNewSize;
			pTmpTarget = ( pTarget = pTmp ) + nOffset;
		}

		memcpy( pTmpTarget, pOutBufData, nOutBufDataLen );
		pTmpTarget += nOutBufDataLen;
		pOutBufData += nOutBufDataLen;
		nOutBufDataLen = 0;

		if ( bEOIFound )
			break;
	}

	rCount = nCount;
	rEOI = bEOIFound;

	return pTarget;
}

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

void GIFLZWDecompressor::AddToTable( sal_uInt16 nPrevCode, sal_uInt16 nCodeFirstData )
{
	GIFLZWTableEntry* pE;

	if( nTableSize < 4096 )
	{
		pE = pTable + nTableSize;
		pE->pPrev = pTable + nPrevCode;
		pE->pFirst = pE->pPrev->pFirst;
		pE->nData = pTable[ nCodeFirstData ].pFirst->nData;
		nTableSize++;

		if ( ( nTableSize == (sal_uInt16) (1 << nCodeSize) ) && ( nTableSize < 4096 ) )
			nCodeSize++;
	}
}

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

sal_Bool GIFLZWDecompressor::ProcessOneCode()
{
	GIFLZWTableEntry*	pE;
	sal_uInt16				nCode;
	sal_Bool				bRet = sal_False;
	sal_Bool				bEndOfBlock = sal_False;

	while( nInputBitsBufSize < nCodeSize )
	{
		if( nBlockBufPos >= nBlockBufSize )
		{
			bEndOfBlock = sal_True;
			break;
		}

		nInputBitsBuf |= ( (sal_uLong) pBlockBuf[ nBlockBufPos++ ] ) << nInputBitsBufSize;
		nInputBitsBufSize += 8;
	}

	if ( !bEndOfBlock )
	{
		// Einen Code aus dem Eingabe-Buffer holen:
		nCode = sal::static_int_cast< sal_uInt16 >(
            ( (sal_uInt16) nInputBitsBuf ) & ( ~( 0xffff << nCodeSize ) ));
		nInputBitsBuf >>= nCodeSize;
		nInputBitsBufSize = nInputBitsBufSize - nCodeSize;

		if ( nCode < nClearCode )
		{
			if ( nOldCode != 0xffff )
				AddToTable( nOldCode, nCode );
		}
		else if ( ( nCode > nEOICode ) && ( nCode <= nTableSize ) )
		{
			if ( nCode == nTableSize )
				AddToTable( nOldCode, nOldCode );
			else
				AddToTable( nOldCode, nCode );
		}
		else
		{
			if ( nCode == nClearCode )
			{
				nTableSize = nEOICode + 1;
				nCodeSize = nDataSize + 1;
				nOldCode = 0xffff;
				nOutBufDataLen = 0;
			}
			else
				bEOIFound = sal_True;

			return sal_True;
		}

		nOldCode = nCode;

		// Zeichen(/-folge) des Codes nCode in den Ausgabe-Buffer schreiben:
		pE = pTable + nCode;
		do
		{
			nOutBufDataLen++;
			*(--pOutBufData) = pE->nData;
			pE = pE->pPrev;
		}
		while( pE );

		bRet = sal_True;
	}

	return bRet;
}