/*

* Copyright (c) 1998-2009 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of the License "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: 

* e32tools\petran\Szip\deflate.cpp

*

*/

#include "deflate.h"

#include "h_utl.h"

#include "panic.h"

class HDeflateHash

	{

public:

	inline static HDeflateHash* NewLC(TInt aLinks);

//

	inline TInt First(const TUint8* aPtr,TInt aPos);

	inline TInt Next(TInt aPos,TInt aOffset) const;

private:

	inline HDeflateHash();

	inline static TInt Hash(const TUint8* aPtr);

private:

	typedef TUint16 TOffset;

private:

	TInt iHash[256];

	TOffset iOffset[1];	// or more

	};

class MDeflater

	{

public:

	void DeflateL(const TUint8* aBase,TInt aLength);

	inline virtual ~MDeflater() { }; 

private:

	const TUint8* DoDeflateL(const TUint8* aBase,const TUint8* aEnd,HDeflateHash& aHash);

	static TInt Match(const TUint8* aPtr,const TUint8* aEnd,TInt aPos,HDeflateHash& aHas);

	void SegmentL(TInt aLength,TInt aDistance);

	virtual void LitLenL(TInt aCode) =0;

	virtual void OffsetL(TInt aCode) =0;

	virtual void ExtraL(TInt aLen,TUint aBits) =0;

	};

class TDeflateStats : public MDeflater

	{

public:

	inline TDeflateStats(TEncoding& aEncoding);

	inline virtual ~TDeflateStats() { } 

private:

// from MDeflater

	void LitLenL(TInt aCode);

	void OffsetL(TInt aCode);

	void ExtraL(TInt aLen,TUint aBits);

private:

	TEncoding& iEncoding;

	};

class TDeflater : public MDeflater

	{

public:

	inline TDeflater(TBitOutput& aOutput,const TEncoding& aEncoding);

	inline virtual ~TDeflater() { }; 

private:

// from MDeflater

	void LitLenL(TInt aCode);

	void OffsetL(TInt aCode);

	void ExtraL(TInt aLen,TUint aBits);

private:

	TBitOutput& iOutput;

	const TEncoding& iEncoding;

	};

// Class HDeflateHash

inline HDeflateHash::HDeflateHash()

	{TInt* p=iHash+256;do *--p=-KDeflateMaxDistance-1; while (p>iHash);}

inline HDeflateHash* HDeflateHash::NewLC(TInt aLinks)

	{

	return new(HMem::Alloc(0,_FOFF(HDeflateHash,iOffset[Min(aLinks,KDeflateMaxDistance)]))) HDeflateHash;

	}

inline TInt HDeflateHash::Hash(const TUint8* aPtr)

	{

	TUint x=aPtr[0]|(aPtr[1]<<8)|(aPtr[2]<<16);

	return (x*KDeflateHashMultiplier)>>KDeflateHashShift;

	}

inline TInt HDeflateHash::First(const TUint8* aPtr,TInt aPos)

	{

	TInt h=Hash(aPtr);

	TInt offset=Min(aPos-iHash[h],KDeflateMaxDistance<<1);

	iHash[h]=aPos;

	iOffset[aPos&(KDeflateMaxDistance-1)]=TOffset(offset);

	return offset;

	}

inline TInt HDeflateHash::Next(TInt aPos,TInt aOffset) const

	{return aOffset+iOffset[(aPos-aOffset)&(KDeflateMaxDistance-1)];}

// Class TDeflater

//

// generic deflation algorithm, can do either statistics and the encoder

TInt MDeflater::Match(const TUint8* aPtr,const TUint8* aEnd,TInt aPos,HDeflateHash& aHash)

	{

	TInt offset=aHash.First(aPtr,aPos);

	if (offset>KDeflateMaxDistance)

		return 0;

	TInt match=0;

	aEnd=Min(aEnd,aPtr+KDeflateMaxLength);

	TUint8 c=*aPtr;

	do

		{

		const TUint8* p=aPtr-offset;

		if (p[match>>16]==c)

			{	// might be a better match

			const TUint8* m=aPtr;

			for (;;)

				{

				if (*p++!=*m++)

					break;

				if (m<aEnd)

					continue;

				return ((m-aPtr)<<16)|offset;

				}

			TInt l=m-aPtr-1;

			if (l>match>>16)

				{

				match=(l<<16)|offset;

				c=m[-1];

				}

			}

		offset=aHash.Next(aPos,offset);

		} while (offset<=KDeflateMaxDistance);

	return match;

	}

const TUint8* MDeflater::DoDeflateL(const TUint8* aBase,const TUint8* aEnd,HDeflateHash& aHash)

//

// Apply the deflation algorithm to the data [aBase,aEnd)

// Return a pointer after the last byte that was deflated (which may not be aEnd)

//

	{

	const TUint8* ptr=aBase;

	TInt prev=0;		// the previous deflation match

	do

		{

		TInt match=Match(ptr,aEnd,ptr-aBase,aHash);

// Extra deflation applies two optimisations which double the time taken

// 1. If we have a match at p, then test for a better match at p+1 before using it

// 2. When we have a match, add the hash links for all the data which will be skipped 

		if (match>>16 < prev>>16)

			{	// use the previous match--it was better

			TInt len=prev>>16;

			SegmentL(len,prev-(len<<16));

			// fill in missing hash entries for better compression

			const TUint8* e=ptr+len-2;

			do 

				{

				++ptr;

				if (ptr + 2 < aEnd)

					aHash.First(ptr,ptr-aBase);

				} while (ptr<e);

			prev=0;

			}

		else if (match<=(KDeflateMinLength<<16))

			LitLenL(*ptr);			// no deflation match here

		else

			{	// save this match and test the next position

			if (prev)	// we had a match at ptr-1, but this is better

				LitLenL(ptr[-1]);

			prev=match;

			}

		++ptr;

		} while (ptr+KDeflateMinLength-1<aEnd);

	if (prev)

		{		// emit the stored match

		TInt len=prev>>16;

		SegmentL(len,prev-(len<<16));

		ptr+=len-1;

		}

	return ptr;

	}

void MDeflater::DeflateL(const TUint8* aBase,TInt aLength)

//

// The generic deflation algorithm

//

	{

	const TUint8* end=aBase+aLength;

	if (aLength>KDeflateMinLength)

		{	// deflation kicks in if there is enough data

		HDeflateHash* hash=HDeflateHash::NewLC(aLength);

		if(hash==NULL)

			Panic(EHuffmanOutOfMemory);

		aBase=DoDeflateL(aBase,end,*hash);

		delete hash;

		}

	while (aBase<end)					// emit remaining bytes

		LitLenL(*aBase++);

	LitLenL(TEncoding::EEos);	// eos marker

	}

void MDeflater::SegmentL(TInt aLength,TInt aDistance)

//

// Turn a (length,offset) pair into the deflation codes+extra bits before calling

// the specific LitLen(), Offset() and Extra() functions.

//

	{

	aLength-=KDeflateMinLength;

	TInt extralen=0;

	TUint len=aLength;

	while (len>=8)

		{

		++extralen;

		len>>=1;

		}

	LitLenL((extralen<<2)+len+TEncoding::ELiterals);

	if (extralen)

		ExtraL(extralen,aLength);

//

	aDistance--;

	extralen=0;

	TUint dist=aDistance;

	while (dist>=8)

		{

		++extralen;

		dist>>=1;

		}

	OffsetL((extralen<<2)+dist);

	if (extralen)

		ExtraL(extralen,aDistance);

	}

// Class TDeflateStats

//

// This class analyses the data stream to generate the frequency tables 

// for the deflation algorithm

inline TDeflateStats::TDeflateStats(TEncoding& aEncoding)

	:iEncoding(aEncoding)

	{}

void TDeflateStats::LitLenL(TInt aCode)

	{

	++iEncoding.iLitLen[aCode];

	}

void TDeflateStats::OffsetL(TInt aCode)

	{

	++iEncoding.iDistance[aCode];

	}

void TDeflateStats::ExtraL(TInt,TUint)

	{}

// Class TDeflater

//

// Extends MDeflater to provide huffman encoding of the output

inline TDeflater::TDeflater(TBitOutput& aOutput,const TEncoding& aEncoding)

//

// construct for encoding

//

	:iOutput(aOutput),iEncoding(aEncoding)

	{}

void TDeflater::LitLenL(TInt aCode)

	{

	iOutput.HuffmanL(iEncoding.iLitLen[aCode]);

	}

void TDeflater::OffsetL(TInt aCode)

	{

	iOutput.HuffmanL(iEncoding.iDistance[aCode]);

	}

void TDeflater::ExtraL(TInt aLen,TUint aBits)

	{

	iOutput.WriteL(aBits,aLen);

	}

void DoDeflateL(const TUint8* aBuf,TInt aLength,TBitOutput& aOutput,TEncoding& aEncoding)

	{

// analyse the data for symbol frequency 

	TDeflateStats analyser(aEncoding);

	analyser.DeflateL(aBuf,aLength);

// generate the required huffman encodings

	Huffman::HuffmanL(aEncoding.iLitLen,TEncoding::ELitLens,aEncoding.iLitLen);

	Huffman::HuffmanL(aEncoding.iDistance,TEncoding::EDistances,aEncoding.iDistance);

// Store the encoding table

	Huffman::ExternalizeL(aOutput,aEncoding.iLitLen,KDeflationCodes);

// generate the tables

	Huffman::Encoding(aEncoding.iLitLen,TEncoding::ELitLens,aEncoding.iLitLen);

	Huffman::Encoding(aEncoding.iDistance,TEncoding::EDistances,aEncoding.iDistance);

// now finally deflate the data with the generated encoding

	TDeflater deflater(aOutput,aEncoding);

	deflater.DeflateL(aBuf,aLength);

	aOutput.PadL(1);

	}

void DeflateL(const TUint8* aBuf, TInt aLength, TBitOutput& aOutput)

	{

	TEncoding* encoding=new TEncoding;

	HMem::FillZ(encoding,sizeof(TEncoding));

	DoDeflateL(aBuf,aLength,aOutput,*encoding);

	}