e32tools/e32lib/e32image/deflate/deflate.cpp
author Alex Gilkes <alex.gilkes@nokia.com>
Tue, 27 Oct 2009 16:36:35 +0000
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// Copyright (c) 1998-2009 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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// e32tools\petran\Szip\deflate.cpp
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// 
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//
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#include "deflate.h"
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#include "h_utl.h"
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#include "panic.h"
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class HDeflateHash
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	{
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public:
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	inline static HDeflateHash* NewLC(TInt aLinks);
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//
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	inline TInt First(const TUint8* aPtr,TInt aPos);
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	inline TInt Next(TInt aPos,TInt aOffset) const;
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private:
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	inline HDeflateHash();
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	inline static TInt Hash(const TUint8* aPtr);
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private:
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	typedef TUint16 TOffset;
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private:
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	TInt iHash[256];
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	TOffset iOffset[1];	// or more
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	};
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class MDeflater
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	{
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public:
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	void DeflateL(const TUint8* aBase,TInt aLength);
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	inline virtual ~MDeflater() { }; 
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private:
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	const TUint8* DoDeflateL(const TUint8* aBase,const TUint8* aEnd,HDeflateHash& aHash);
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	static TInt Match(const TUint8* aPtr,const TUint8* aEnd,TInt aPos,HDeflateHash& aHas);
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	void SegmentL(TInt aLength,TInt aDistance);
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	virtual void LitLenL(TInt aCode) =0;
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	virtual void OffsetL(TInt aCode) =0;
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	virtual void ExtraL(TInt aLen,TUint aBits) =0;
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	};
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class TDeflateStats : public MDeflater
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	{
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public:
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	inline TDeflateStats(TEncoding& aEncoding);
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	inline virtual ~TDeflateStats() { } 
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private:
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// from MDeflater
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	void LitLenL(TInt aCode);
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	void OffsetL(TInt aCode);
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	void ExtraL(TInt aLen,TUint aBits);
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private:
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	TEncoding& iEncoding;
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	};
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class TDeflater : public MDeflater
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	{
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public:
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	inline TDeflater(TBitOutput& aOutput,const TEncoding& aEncoding);
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	inline virtual ~TDeflater() { }; 
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private:
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// from MDeflater
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	void LitLenL(TInt aCode);
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	void OffsetL(TInt aCode);
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	void ExtraL(TInt aLen,TUint aBits);
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private:
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	TBitOutput& iOutput;
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	const TEncoding& iEncoding;
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	};
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// Class HDeflateHash
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inline HDeflateHash::HDeflateHash()
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	{TInt* p=iHash+256;do *--p=-KDeflateMaxDistance-1; while (p>iHash);}
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inline HDeflateHash* HDeflateHash::NewLC(TInt aLinks)
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	{
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	return new(HMem::Alloc(0,_FOFF(HDeflateHash,iOffset[Min(aLinks,KDeflateMaxDistance)]))) HDeflateHash;
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	}
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inline TInt HDeflateHash::Hash(const TUint8* aPtr)
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	{
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	TUint x=aPtr[0]|(aPtr[1]<<8)|(aPtr[2]<<16);
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	return (x*KDeflateHashMultiplier)>>KDeflateHashShift;
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	}
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inline TInt HDeflateHash::First(const TUint8* aPtr,TInt aPos)
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	{
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	TInt h=Hash(aPtr);
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	TInt offset=Min(aPos-iHash[h],KDeflateMaxDistance<<1);
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	iHash[h]=aPos;
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	iOffset[aPos&(KDeflateMaxDistance-1)]=TOffset(offset);
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	return offset;
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	}
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inline TInt HDeflateHash::Next(TInt aPos,TInt aOffset) const
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	{return aOffset+iOffset[(aPos-aOffset)&(KDeflateMaxDistance-1)];}
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// Class TDeflater
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//
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// generic deflation algorithm, can do either statistics and the encoder
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TInt MDeflater::Match(const TUint8* aPtr,const TUint8* aEnd,TInt aPos,HDeflateHash& aHash)
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	{
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	TInt offset=aHash.First(aPtr,aPos);
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	if (offset>KDeflateMaxDistance)
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		return 0;
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	TInt match=0;
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	aEnd=Min(aEnd,aPtr+KDeflateMaxLength);
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	TUint8 c=*aPtr;
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	do
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		{
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		const TUint8* p=aPtr-offset;
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		if (p[match>>16]==c)
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			{	// might be a better match
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			const TUint8* m=aPtr;
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			for (;;)
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				{
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				if (*p++!=*m++)
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					break;
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				if (m<aEnd)
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					continue;
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				return ((m-aPtr)<<16)|offset;
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				}
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			TInt l=m-aPtr-1;
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			if (l>match>>16)
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				{
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				match=(l<<16)|offset;
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				c=m[-1];
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				}
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			}
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		offset=aHash.Next(aPos,offset);
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		} while (offset<=KDeflateMaxDistance);
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	return match;
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	}
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const TUint8* MDeflater::DoDeflateL(const TUint8* aBase,const TUint8* aEnd,HDeflateHash& aHash)
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//
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// Apply the deflation algorithm to the data [aBase,aEnd)
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// Return a pointer after the last byte that was deflated (which may not be aEnd)
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//
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	{
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	const TUint8* ptr=aBase;
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	TInt prev=0;		// the previous deflation match
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	do
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		{
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		TInt match=Match(ptr,aEnd,ptr-aBase,aHash);
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// Extra deflation applies two optimisations which double the time taken
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// 1. If we have a match at p, then test for a better match at p+1 before using it
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// 2. When we have a match, add the hash links for all the data which will be skipped 
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		if (match>>16 < prev>>16)
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			{	// use the previous match--it was better
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			TInt len=prev>>16;
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			SegmentL(len,prev-(len<<16));
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			// fill in missing hash entries for better compression
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			const TUint8* e=ptr+len-2;
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			do 
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				{
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				++ptr;
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				if (ptr + 2 < aEnd)
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					aHash.First(ptr,ptr-aBase);
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				} while (ptr<e);
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			prev=0;
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			}
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		else if (match<=(KDeflateMinLength<<16))
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			LitLenL(*ptr);			// no deflation match here
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		else
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			{	// save this match and test the next position
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			if (prev)	// we had a match at ptr-1, but this is better
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				LitLenL(ptr[-1]);
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			prev=match;
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			}
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		++ptr;
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		} while (ptr+KDeflateMinLength-1<aEnd);
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	if (prev)
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		{		// emit the stored match
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		TInt len=prev>>16;
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		SegmentL(len,prev-(len<<16));
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		ptr+=len-1;
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		}
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	return ptr;
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	}
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void MDeflater::DeflateL(const TUint8* aBase,TInt aLength)
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//
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// The generic deflation algorithm
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//
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	{
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	const TUint8* end=aBase+aLength;
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	if (aLength>KDeflateMinLength)
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		{	// deflation kicks in if there is enough data
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		HDeflateHash* hash=HDeflateHash::NewLC(aLength);
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		if(hash==NULL)
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			Panic(EHuffmanOutOfMemory);
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		aBase=DoDeflateL(aBase,end,*hash);
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		delete hash;
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		}
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	while (aBase<end)					// emit remaining bytes
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		LitLenL(*aBase++);
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	LitLenL(TEncoding::EEos);	// eos marker
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	}
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void MDeflater::SegmentL(TInt aLength,TInt aDistance)
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//
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// Turn a (length,offset) pair into the deflation codes+extra bits before calling
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// the specific LitLen(), Offset() and Extra() functions.
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//
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	{
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	aLength-=KDeflateMinLength;
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	TInt extralen=0;
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	TUint len=aLength;
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	while (len>=8)
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		{
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		++extralen;
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		len>>=1;
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		}
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	LitLenL((extralen<<2)+len+TEncoding::ELiterals);
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	if (extralen)
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		ExtraL(extralen,aLength);
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//
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	aDistance--;
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	extralen=0;
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	TUint dist=aDistance;
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	while (dist>=8)
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		{
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		++extralen;
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		dist>>=1;
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		}
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	OffsetL((extralen<<2)+dist);
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	if (extralen)
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		ExtraL(extralen,aDistance);
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	}
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// Class TDeflateStats
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//
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// This class analyses the data stream to generate the frequency tables 
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// for the deflation algorithm
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inline TDeflateStats::TDeflateStats(TEncoding& aEncoding)
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	:iEncoding(aEncoding)
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	{}
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void TDeflateStats::LitLenL(TInt aCode)
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	{
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	++iEncoding.iLitLen[aCode];
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	}
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void TDeflateStats::OffsetL(TInt aCode)
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	{
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	++iEncoding.iDistance[aCode];
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	}
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void TDeflateStats::ExtraL(TInt,TUint)
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	{}
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// Class TDeflater
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//
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// Extends MDeflater to provide huffman encoding of the output
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inline TDeflater::TDeflater(TBitOutput& aOutput,const TEncoding& aEncoding)
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//
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// construct for encoding
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//
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	:iOutput(aOutput),iEncoding(aEncoding)
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	{}
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void TDeflater::LitLenL(TInt aCode)
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	{
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	iOutput.HuffmanL(iEncoding.iLitLen[aCode]);
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	}
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void TDeflater::OffsetL(TInt aCode)
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	{
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	iOutput.HuffmanL(iEncoding.iDistance[aCode]);
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	}
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void TDeflater::ExtraL(TInt aLen,TUint aBits)
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	{
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	iOutput.WriteL(aBits,aLen);
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	}
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void DoDeflateL(const TUint8* aBuf,TInt aLength,TBitOutput& aOutput,TEncoding& aEncoding)
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	{
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// analyse the data for symbol frequency 
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	TDeflateStats analyser(aEncoding);
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	analyser.DeflateL(aBuf,aLength);
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// generate the required huffman encodings
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	Huffman::HuffmanL(aEncoding.iLitLen,TEncoding::ELitLens,aEncoding.iLitLen);
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	Huffman::HuffmanL(aEncoding.iDistance,TEncoding::EDistances,aEncoding.iDistance);
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// Store the encoding table
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	Huffman::ExternalizeL(aOutput,aEncoding.iLitLen,KDeflationCodes);
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// generate the tables
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	Huffman::Encoding(aEncoding.iLitLen,TEncoding::ELitLens,aEncoding.iLitLen);
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	Huffman::Encoding(aEncoding.iDistance,TEncoding::EDistances,aEncoding.iDistance);
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// now finally deflate the data with the generated encoding
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	TDeflater deflater(aOutput,aEncoding);
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	deflater.DeflateL(aBuf,aLength);
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	aOutput.PadL(1);
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	}
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void DeflateL(const TUint8* aBuf, TInt aLength, TBitOutput& aOutput)
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	{
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	TEncoding* encoding=new TEncoding;
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	HMem::FillZ(encoding,sizeof(TEncoding));
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	DoDeflateL(aBuf,aLength,aOutput,*encoding);
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	}
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