// Copyright (c) 2004-2009 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:

// Implementation of the Huffman technique for the elf2e32 tool

// @internalComponent

// @released

// 

//

#ifdef _MSC_VER

	#pragma warning(disable: 4710) // function not inlined

#endif

#include <cassert>

#include "huffman.h"

#include "errorhandler.h"

#include "farray.h"

/**

Function for overflow

@internalComponent

@released

*/

void TBitOutput::OverflowL()

{

}

/**

Construct a bit stream output object

Following construction the bit stream is ready for writing bits, but will first call

OverflowL() as the output buffer is 'full'. A derived class can detect this state as

Ptr() will return null.

*/

TBitOutput::TBitOutput():iCode(0),iBits(-8),iPtr(0),iEnd(0)

{

}

/**

Construct a bit stream output object over a buffer

Data will be written to the buffer until it is full, at which point OverflowL() will

be called. This should handle the data and then can Set() again to reset the buffer

for further output.

@param "TUint8* aBuf" The buffer for output

@param "TInt aSize" The size of the buffer in bytes

*/

TBitOutput::TBitOutput(TUint8* aBuf,TInt aSize):iCode(0),iBits(-8),iPtr(aBuf),iEnd(aBuf+aSize)

{

}

/**

Write a huffman code

This expects a huffman code value as generated by Huffman::Encoding()

@param "TUint aHuffCode" The huffman code write to the stream

@leave "OverflowL()" If the output buffer is full, OverflowL() is called

*/

void TBitOutput::HuffmanL(TUint aHuffCode)

{

	DoWriteL(aHuffCode<<(32-Huffman::KMaxCodeLength),aHuffCode>>Huffman::KMaxCodeLength);

}

/**

Write an arbitrary integer value

Write an unsigned integer using the number of bits specified. Only the low order bits of the

value are written to the output, most significant bit first.

@param "TUint aValue" The value to write to the stream

@param "TUint aLength" The number of bits to output

@leave "OverflowL()" If the output buffer is full, OverflowL() is called

*/

void TBitOutput::WriteL(TUint aValue,TInt aLength)

{

	if (aLength)

		DoWriteL(aValue<<=32-aLength,aLength);

}

/**

Pad the bitstream to the next byte boundary

Terminate the bitstream by padding the last byte with the requested value.

Following this operation the bitstream can continue to be used, the data will start at the

next byte.

@param "TUint aPadding" The bit value to pad the final byte with

@leave "OverflowL()" If the output buffer is full, OverflowL() is called

*/

void TBitOutput::PadL(TUint aPadding)

{

	if (iBits>-8)

		WriteL(aPadding?0xffffffffu:0,-iBits);

}

/**

Write the higher order bits to the stream

@internalComponent

@released

*/

void TBitOutput::DoWriteL(TUint aBits,TInt aSize)

{

	if (aSize>25)

	{

		// cannot process >25 bits in a single pass so do the top 8 bits first

		assert(aSize<=32);

		DoWriteL(aBits&0xff000000u,8);

		aBits<<=8;

		aSize-=8;

	}

	TInt bits=iBits;

	TUint code=iCode|(aBits>>(bits+8));

	bits+=aSize;

	if (bits>=0)

	{

		TUint8* p=iPtr;

		do

		{

			if (p==iEnd)

			{

				// run out of buffer space so invoke the overflow handler

				iPtr=p;

				OverflowL();

				p=iPtr;

				assert(p!=iEnd);

			}

			*p++=TUint8(code>>24);

			code<<=8;

			bits-=8;

		} while (bits>=0);

		iPtr=p;

	}

	iCode=code;

	iBits=bits;

}

/**

Constructor for class TFileOutput

@internalComponent

@released

*/

TFileOutput::TFileOutput(std::ofstream & os):iOutStream(os)

{

	Set(iBuf,KBufSize);

}

/**

Function to empty the buffer and reset the pointers

@internalComponent

@released

*/

void TFileOutput::OverflowL()

{

	FlushL();

	Set(iBuf,KBufSize);

}

/**

Function to write out the contents of the buffer

@internalComponent

@released

*/

void TFileOutput::FlushL()

{

	TInt len=Ptr()-iBuf;

	if (len)

	{

		iOutStream.write(reinterpret_cast<char *>(iBuf), len); // write extended header

		iDataCount += len;

	}

}

/**

Recursive function to calculate the code lengths from the node tree

@internalComponent

@released

*/

void HuffmanLengthsL(TUint32* aLengths,const TNode* aNodes,TInt aNode,TInt aLen)

{

	if (++aLen>Huffman::KMaxCodeLength)

		throw E32ImageCompressionError(HUFFMANBUFFEROVERFLOWERROR);

	const TNode& node=aNodes[aNode];

	TUint x=node.iLeft;

	if (x&KLeaf)

		aLengths[x&~KLeaf]=aLen;

	else

		HuffmanLengthsL(aLengths,aNodes,x,aLen);

	x=node.iRight;

	if (x&KLeaf)

		aLengths[x&~KLeaf]=aLen;

	else

		HuffmanLengthsL(aLengths,aNodes,x,aLen);

}

/**

Function to Insert the {aCount,aValue} pair into the already sorted array of nodes

@internalComponent

@released

*/

void InsertInOrder(TNode* aNodes, TInt aSize, TUint aCount, TInt aVal)

{

	// Uses Insertion sort following a binary search...

	TInt l=0, r=aSize;

	while (l < r)

	{

		TInt m = (l+r) >> 1;

		if (aNodes[m].iCount<aCount)

			r=m;

		else

			l=m+1;

	}

	memmove(aNodes+l+1,aNodes+l,sizeof(TNode)*(aSize-l));

	aNodes[l].iCount=aCount;

	aNodes[l].iRight=TUint16(aVal);

}

/**

Generate a Huffman code.

This generates a Huffman code for a given set of code frequencies. The output is a table of

code lengths which can be used to build canonincal encoding tables or decoding trees for use

with the TBitInput and TBitOutput classes.

Entries in the table with a frequency of zero will have a zero code length and thus no

associated huffman encoding. If each such symbol should have a maximum length encoding, they

must be given at least a frequency of 1.

For an alphabet of n symbols, this algorithm has a transient memory overhead of 8n, and a

time complexity of O(n*log(n)).

@param "const TUint32 aFrequency[]" The table of code frequencies

@param "TInt aNumCodes" The number of codes in the table

@param "TUint32 aHuffman[]" The table for the output code-length table. This must be the same

size as the frequency table, and can safely be the same table

@leave "KErrNoMemory" If memory used for code generation cannot be allocated

@panic "USER ???" If the number of codes exceeds Huffman::KMaxCodes

*/

void Huffman::HuffmanL(const TUint32 aFrequency[],TInt aNumCodes,TUint32 aHuffman[])

{

	if(TUint(aNumCodes)>TUint(KMaxCodes))

		throw E32ImageCompressionError(HUFFMANTOOMANYCODESERROR);

	// Sort the values into decreasing order of frequency

	TNode* nodes = new TNode[aNumCodes];

	TInt lCount=0;

	for (TInt ii=0;ii<aNumCodes;++ii)

	{

		TInt c=aFrequency[ii];

		if (c!=0)

			InsertInOrder(nodes,lCount++,c,ii|KLeaf);

	}

	// default code length is zero

	memset(aHuffman,0,aNumCodes*sizeof(TUint32));

	if (lCount==0)

	{

		// no codes with frequency>0. No code has a length

	}

	else if (lCount==1)

	{

		// special case for a single value (always encode as "0")

		aHuffman[nodes[0].iRight&~KLeaf]=1;

	}

	else

	{

		// Huffman algorithm: pair off least frequent nodes and reorder

		do

		{

			--lCount;

			TUint c=nodes[lCount].iCount + nodes[lCount-1].iCount;

			nodes[lCount].iLeft=nodes[lCount-1].iRight;

			// re-order the leaves now to reflect new combined frequency 'c'

			InsertInOrder(nodes,lCount-1,c,lCount);

		} while (lCount>1);

		// generate code lengths in aHuffman[]

		HuffmanLengthsL(aHuffman,nodes,1,0);

	}

	delete [] nodes;

	if(!IsValid(aHuffman,aNumCodes))

		throw E32ImageCompressionError(HUFFMANINVALIDCODINGERROR);

}

/**

Validate a Huffman encoding

This verifies that a Huffman coding described by the code lengths is valid. In particular,

it ensures that no code exceeds the maximum length and that it is possible to generate a

canonical coding for the specified lengths.

@param "const TUint32 aHuffman[]" The table of code lengths as generated by Huffman::HuffmanL()

@param "TInt aNumCodes" The number of codes in the table

@return True if the code is valid, otherwise false

*/

TBool Huffman::IsValid(const TUint32 aHuffman[],TInt aNumCodes)

{

	// The code is valid if one of the following holds:

	// (a) the code exactly fills the 'code space'

	// (b) there is only a single symbol with code length 1

	// (c) there are no encoded symbols

	//

	TUint remain=1<<KMaxCodeLength;

	TInt totlen=0;

	for (const TUint32* p=aHuffman+aNumCodes; p>aHuffman;)

	{

		TInt len=*--p;

		if (len>0)

		{

			totlen+=len;

			if (len>KMaxCodeLength)

				return 0;

			TUint c=1<<(KMaxCodeLength-len);

			if (c>remain)

				return 0;

			remain-=c;

		}

	}

	return remain==0 || totlen<=1;

}

/**

Create a canonical Huffman encoding table

This generates the huffman codes used by TBitOutput::HuffmanL() to write huffman encoded data.

The input is table of code lengths, as generated by Huffman::HuffmanL() and must represent a

valid huffman code.

@param "const TUint32 aHuffman[]" The table of code lengths as generated by Huffman::HuffmanL()

@param "TInt aNumCodes" The number of codes in the table

@param "TUint32 aEncodeTable[]" The table for the output huffman codes. This must be the same

size as the code-length table, and can safely be the same table.

@panic "USER ???" If the provided code is not a valid Huffman coding

@see IsValid()

@see HuffmanL()

*/

void Huffman::Encoding(const TUint32 aHuffman[],TInt aNumCodes,TUint32 aEncodeTable[])

{

	if (!IsValid(aHuffman,aNumCodes)) 

		throw E32ImageCompressionError(HUFFMANINVALIDCODINGERROR);

	TFixedArray<TInt,KMaxCodeLength> lenCount;

	lenCount.Reset();

	TInt ii;

	for (ii=0;ii<aNumCodes;++ii)

	{

		TInt len=aHuffman[ii]-1;

		if (len>=0)

			++lenCount[len];

	}

	TFixedArray<TUint,KMaxCodeLength> nextCode;

	TUint code=0;

	for (ii=0;ii<KMaxCodeLength;++ii)

	{

		code<<=1;

		nextCode[ii]=code;

		code+=lenCount[ii];

	}

	for (ii=0;ii<aNumCodes;++ii)

	{

		TInt len=aHuffman[ii];

		if (len==0)

			aEncodeTable[ii]=0;

		else

		{

			aEncodeTable[ii] = (nextCode[len-1]<<(KMaxCodeLength-len))|(len<<KMaxCodeLength);

			++nextCode[len-1];

		}

	}

}

/**

The encoding table for the externalised code

@internalComponent

@released

*/

const TUint32 HuffmanEncoding[]=

{

	0x10000000,

	0x1c000000,

	0x12000000,

	0x1d000000,

	0x26000000,

	0x26800000,

	0x2f000000,

	0x37400000,

	0x37600000,

	0x37800000,

	0x3fa00000,

	0x3fb00000,

	0x3fc00000,

	0x3fd00000,

	0x47e00000,

	0x47e80000,

	0x47f00000,

	0x4ff80000,

	0x57fc0000,

	0x5ffe0000,

	0x67ff0000,

	0x77ff8000,

	0x7fffa000,

	0x7fffb000,

	0x7fffc000,

	0x7fffd000,

	0x7fffe000,

	0x87fff000,

	0x87fff800

};

/**

Function to encode 0a as '0' and 0b as '1', return number of symbols created

@internalComponent

@released

*/

void EncodeRunLengthL(TBitOutput& aOutput, TInt aLength)

{

	if (aLength>0)

	{

		EncodeRunLengthL(aOutput,(aLength-1)>>1);

		aOutput.HuffmanL(HuffmanEncoding[1-(aLength&1)]);

	}

}

/**

Store a canonical huffman encoding in compact form

As the encoding is canonical, only the code lengths of each code needs to be saved.

Due to the nature of code length tables, these can usually be stored very compactly by

encoding the encoding itself, hence the use of the bit output stream.

@param "TBitOutput& aOutput" The output stream for the encoding

@param "const TUint32 aHuffman[]" The table of code lengths as generated by Huffman::HuffmanL()

@param "TInt aNumCodes" The number of huffman codes in the table

@leave "TBitOutput::HuffmanL()"

*/

void Huffman::ExternalizeL(TBitOutput& aOutput,const TUint32 aHuffman[],TInt aNumCodes)

{

	// We assume that the code length table is generated by the huffman generator,

	// in which case the maxmimum code length is 27 bits.

	//

	// We apply three transformations to the data:

	// 1. the data goes through a move-to-front coder

	// 2. apply a rle-0 coder which replace runs of '0' with streams of '0a' and '0b'

	// 3. encode the result using a predefined (average) huffman coding

	//

	// This can be done in a single pass over the data, avoiding the need for additional

	// memory.

	//

	// initialise the list for the MTF coder

	TFixedArray<TUint8,Huffman::KMetaCodes> list;

	TInt i;

	for (i=0;i<list.Count();++i)

		list[i]=TUint8(i);

	TInt last=0;

	TInt rl=0;

	const TUint32* p32=aHuffman;

	const TUint32* e32=p32+aNumCodes;

	while (p32<e32)

	{

		TInt c=*p32++;

		if (c==last)

			++rl;	// repeat of last symbol

		else

		{

			// encode run-length

			EncodeRunLengthL(aOutput,rl);

			rl=0;

			// find code in MTF list

			TInt j;

			for (j=1;list[j]!=c;++j)

				;

			// store this code

			aOutput.HuffmanL(HuffmanEncoding[j+1]);

			// adjust list for MTF algorithm

			while (--j>0)

				list[j+1]=list[j];

			list[1]=TUint8(last);

			last=c;

		}

	}

	// encod any remaining run-length

	EncodeRunLengthL(aOutput,rl);

}

const TInt KHuffTerminate=0x0001;

const TUint32 KBranch1=sizeof(TUint32)<<16;

/**

Function to write the subtree below aPtr and return the head

*/

TUint32* HuffmanSubTree(TUint32* aPtr,const TUint32* aValue,TUint32** aLevel)

{

	TUint32* l=*aLevel++;

	if (l>aValue)

	{

		TUint32* sub0=HuffmanSubTree(aPtr,aValue,aLevel);		// 0-tree first

		aPtr=HuffmanSubTree(sub0,aValue-(aPtr-sub0)-1,aLevel);	// 1-tree

		TInt branch0=(TUint8*)sub0-(TUint8*)(aPtr-1);

		*--aPtr=KBranch1|branch0;