imgtools/imglib/e32image/deflate/encode.cpp
author srilekhas <srilekhas@symbian.org>
Wed, 18 Aug 2010 11:18:38 +0100
changeset 627 cb3264f4c6e6
parent 0 044383f39525
permissions -rw-r--r--
Merge : re-applies missing part of fix for Bug 2901,Add export for s60ibymacros.pm
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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/*
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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 the License "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\encode.cpp
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*
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*/
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#include "huffman.h"
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#include "panic.h"
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#include <e32base.h>
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#include <e32base_private.h>
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#include "h_utl.h"
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#include <assert.h>
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#include "farray.h"
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#include <stdlib.h>
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void User::Invariant()
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	{
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	fprintf(stderr, "User::Invariant() called\n");
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	exit(1);
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	}
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// local definitions used for Huffman code generation
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typedef TUint16 THuff;		/** @internal */
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const THuff KLeaf=0x8000;	/** @internal */
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struct TNode
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/** @internal */
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	{
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	TUint iCount;
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	THuff iLeft;
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	THuff iRight;
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	};
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void HuffmanLengthsL(TUint32* aLengths,const TNode* aNodes,TInt aNode,TInt aLen)
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/** recursive function to calculate the code lengths from the node tree
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	@internal
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*/
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	{
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	if (++aLen>Huffman::KMaxCodeLength)
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		Panic(EHuffmanBufferOverflow);
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	const TNode& node=aNodes[aNode];
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	TUint x=node.iLeft;
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	if (x&KLeaf)
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		aLengths[x&~KLeaf]=aLen;
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	else
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		HuffmanLengthsL(aLengths,aNodes,x,aLen);
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	x=node.iRight;
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	if (x&KLeaf)
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		aLengths[x&~KLeaf]=aLen;
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	else
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		HuffmanLengthsL(aLengths,aNodes,x,aLen);
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	}
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void InsertInOrder(TNode* aNodes, TInt aSize, TUint aCount, TInt aVal)
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/**	Insert the {aCount,aValue} pair into the already sorted array of nodes
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	@internal
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*/
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	{
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	// Uses Insertion sort following a binary search...
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	TInt l=0, r=aSize;
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	while (l < r)
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		{
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		TInt m = (l+r) >> 1;
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		if (aNodes[m].iCount<aCount)
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			r=m;
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		else
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			l=m+1;
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		}
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	HMem::Copy(aNodes+l+1,aNodes+l,sizeof(TNode)*(aSize-l));
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	aNodes[l].iCount=aCount;
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	aNodes[l].iRight=TUint16(aVal);
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	}
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void Huffman::HuffmanL(const TUint32 aFrequency[],TInt aNumCodes,TUint32 aHuffman[])
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/** Generate a Huffman code
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	This generates a Huffman code for a given set of code frequencies. The output
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	is a table of code lengths which can be used to build canonincal encoding tables
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	or decoding trees for use with the TBitInput and TBitOutput classes.
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	Entries in the table with a frequency of zero will have a zero code length
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	and thus no associated huffman encoding. If each such symbol should have a
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	maximum length encoding, they must be given at least a frequency of 1.
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	For an alphabet of n symbols, this algorithm has a transient memory overhead
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	of 8n, and a time complexity of O(n*log(n)).
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	@param "const TUint32 aFrequency[]" The table of code frequencies
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	@param "TInt aNumCodes" The number of codes in the table
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	@param "TUint32 aHuffman[]" The table for the output code-length table. This must be
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		the same size as the frequency table, and can safely be the same table
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	@leave "KErrNoMemory" If memory used for code generation cannot be allocated
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  	@panic "USER ???" If the number of codes exceeds Huffman::KMaxCodes
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*/
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	{
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	if(TUint(aNumCodes)>TUint(KMaxCodes))
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		Panic(EHuffmanTooManyCodes);
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	// Sort the values into decreasing order of frequency
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	//
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	TNode* nodes = new TNode[aNumCodes];
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	if(nodes==NULL)
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		Panic(EHuffmanOutOfMemory);
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	TInt lCount=0;
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	for (TInt ii=0;ii<aNumCodes;++ii)
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		{
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		TInt c=aFrequency[ii];
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		if (c!=0)
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			InsertInOrder(nodes,lCount++,c,ii|KLeaf);
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		}
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	// default code length is zero
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	HMem::FillZ(aHuffman,aNumCodes*sizeof(TUint32));
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	if (lCount==0)
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		{
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		// no codes with frequency>0. No code has a length
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		}
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	else if (lCount==1)
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		{
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		// special case for a single value (always encode as "0")
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		aHuffman[nodes[0].iRight&~KLeaf]=1;
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		}
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	else
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		{
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		// Huffman algorithm: pair off least frequent nodes and reorder
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		//
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		do
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			{
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			--lCount;
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			TUint c=nodes[lCount].iCount + nodes[lCount-1].iCount;
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			nodes[lCount].iLeft=nodes[lCount-1].iRight;
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			// re-order the leaves now to reflect new combined frequency 'c'
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			InsertInOrder(nodes,lCount-1,c,lCount);
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			} while (lCount>1);
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		// generate code lengths in aHuffman[]
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		HuffmanLengthsL(aHuffman,nodes,1,0);
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		}
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	delete [] nodes;
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	if(!IsValid(aHuffman,aNumCodes))
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		Panic(EHuffmanInvalidCoding);
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	}
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TBool Huffman::IsValid(const TUint32 aHuffman[],TInt aNumCodes)
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/** Validate a Huffman encoding
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	This verifies that a Huffman coding described by the code lengths is valid.
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	In particular, it ensures that no code exceeds the maximum length and
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	that it is possible to generate a canonical coding for the specified lengths.
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	@param "const TUint32 aHuffman[]" The table of code lengths as generated by Huffman::HuffmanL()
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	@param "TInt aNumCodes" The number of codes in the table
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	@return True if the code is valid, otherwise false
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*/
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	{
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	// The code is valid if one of the following holds:
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	// (a) the code exactly fills the 'code space'
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	// (b) there is only a single symbol with code length 1
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	// (c) there are no encoded symbols
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	//
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	TUint remain=1<<KMaxCodeLength;
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	TInt totlen=0;
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	for (const TUint32* p=aHuffman+aNumCodes; p>aHuffman;)
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		{
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		TInt len=*--p;
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		if (len>0)
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			{
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			totlen+=len;
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			if (len>KMaxCodeLength)
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				return EFalse;
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			TUint c=1<<(KMaxCodeLength-len);
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			if (c>remain)
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				return EFalse;
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			remain-=c;
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			}
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		}
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	return remain==0 || totlen<=1;
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	}
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void Huffman::Encoding(const TUint32 aHuffman[],TInt aNumCodes,TUint32 aEncodeTable[])
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/** Create a canonical Huffman encoding table
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	This generates the huffman codes used by TBitOutput::HuffmanL() to write huffman
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	encoded data. The input is table of code lengths, as generated by Huffman::HuffmanL()
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	and must represent a valid huffman code.
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	@param "const TUint32 aHuffman[]" The table of code lengths as generated by Huffman::HuffmanL()
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	@param "TInt aNumCodes" The number of codes in the table
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	@param "TUint32 aEncodeTable[]" The table for the output huffman codes. This must be
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		the same size as the code-length table, and can safely be the same table
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	@panic "USER ???" If the provided code is not a valid Huffman coding
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	@see IsValid()
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	@see HuffmanL()
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*/
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	{
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	__ASSERT_ALWAYS(IsValid(aHuffman,aNumCodes),Panic(EHuffmanInvalidCoding));
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	TFixedArray<TInt,KMaxCodeLength> lenCount;
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	lenCount.Reset();
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	TInt ii;
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	for (ii=0;ii<aNumCodes;++ii)
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		{
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		TInt len=aHuffman[ii]-1;
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		if (len>=0)
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			++lenCount[len];
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		}
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	TFixedArray<TUint,KMaxCodeLength> nextCode;
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	TUint code=0;
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	for (ii=0;ii<KMaxCodeLength;++ii)
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		{
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		code<<=1;
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		nextCode[ii]=code;
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		code+=lenCount[ii];
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		}
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	for (ii=0;ii<aNumCodes;++ii)
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		{
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		TInt len=aHuffman[ii];
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		if (len==0)
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			aEncodeTable[ii]=0;
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		else
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			{
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			aEncodeTable[ii] = (nextCode[len-1]<<(KMaxCodeLength-len))|(len<<KMaxCodeLength);
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			++nextCode[len-1];
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			}
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		}
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	}
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/** the encoding table for the externalised code
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	@internal
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*/
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const TUint32 HuffmanEncoding[]=
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	{
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	0x10000000,
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	0x1c000000,
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	0x12000000,
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	0x1d000000,
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	0x26000000,
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	0x26800000,
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	0x2f000000,
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	0x37400000,
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	0x37600000,
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	0x37800000,
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	0x3fa00000,
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	0x3fb00000,
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	0x3fc00000,
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	0x3fd00000,
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	0x47e00000,
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	0x47e80000,
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	0x47f00000,
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	0x4ff80000,
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	0x57fc0000,
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	0x5ffe0000,
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	0x67ff0000,
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	0x77ff8000,
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	0x7fffa000,
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	0x7fffb000,
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	0x7fffc000,
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	0x7fffd000,
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	0x7fffe000,
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	0x87fff000,
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	0x87fff800
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	};
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void EncodeRunLengthL(TBitOutput& aOutput, TInt aLength)
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/** encode 0a as '0' and 0b as '1', return number of symbols created
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	@internal
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*/
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	{
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	if (aLength>0)
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		{
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		EncodeRunLengthL(aOutput,(aLength-1)>>1);
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		aOutput.HuffmanL(HuffmanEncoding[1-(aLength&1)]);
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		}
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	}
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void Huffman::ExternalizeL(TBitOutput& aOutput,const TUint32 aHuffman[],TInt aNumCodes)
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/** Store a canonical huffman encoding in compact form
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	As the encoding is canonical, only the code lengths of each code needs to be saved.
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	Due to the nature of code length tables, these can usually be stored very compactly
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	by encoding the encoding itself, hence the use of the bit output stream.
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	@param "TBitOutput& aOutput" The output stream for the encoding
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	@param "const TUint32 aHuffman[]" The table of code lengths as generated by Huffman::HuffmanL()
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	@param "TInt aNumCodes" The number of huffman codes in the table
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	@leave "TBitOutput::HuffmanL()"
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*/
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	{
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	// We assume that the code length table is generated by the huffman generator,
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	// in which case the maxmimum code length is 27 bits.
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	//
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	// We apply three transformations to the data:
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	// 1. the data goes through a move-to-front coder
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	// 2. apply a rle-0 coder which replace runs of '0' with streams of '0a' and '0b'
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	// 3. encode the result using a predefined (average) huffman coding
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	//
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	// This can be done in a single pass over the data, avoiding the need for additional
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	// memory.
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   330
	//
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	// initialise the list for the MTF coder
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	TFixedArray<TUint8,Huffman::KMetaCodes> list;
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	TInt i;
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	for (i=0;i<list.Count();++i)
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		list[i]=TUint8(i);
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	TInt last=0;
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	TInt rl=0;
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	const TUint32* p32=aHuffman;
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	const TUint32* e32=p32+aNumCodes;
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	while (p32<e32)
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		{
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		TInt c=*p32++;
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		if (c==last)
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			++rl;	// repeat of last symbol
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   346
		else
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			{
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			// encode run-length
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			EncodeRunLengthL(aOutput,rl);
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			rl=0;
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			// find code in MTF list
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			TInt j;
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			for (j=1;list[j]!=c;++j)
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   354
				;
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			// store this code
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   356
			aOutput.HuffmanL(HuffmanEncoding[j+1]);
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   357
			// adjust list for MTF algorithm
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			while (--j>0)
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				list[j+1]=list[j];
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			list[1]=TUint8(last);
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   361
			last=c;
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   362
			}
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   363
		}
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   364
	// encod any remaining run-length
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   365
	EncodeRunLengthL(aOutput,rl);
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   366
	}
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   367
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   368
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   369
TBitOutput::TBitOutput()
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   370
/** Construct a bit stream output object
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   371
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   372
	Following construction the bit stream is ready for writing bits, but will first call
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   373
	OverflowL() as the output buffer is 'full'. A derived class can detect this state as
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   374
	Ptr() will return null.
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   375
*/
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   376
	:iCode(0),iBits(-8),iPtr(0),iEnd(0)
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   377
	{}
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   378
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   379
TBitOutput::TBitOutput(TUint8* aBuf,TInt aSize)
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   380
/** Construct a bit stream output object over a buffer
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   381
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   382
	Data will be written to the buffer until it is full, at which point OverflowL() will
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diff changeset
   383
	be called. This should handle the data and then can Set() again to reset the buffer
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diff changeset
   384
	for further output.
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   385
	
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   386
	@param "TUint8* aBuf" The buffer for output
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   387
	@param "TInt aSize" The size of the buffer in bytes
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diff changeset
   388
*/
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   389
	:iCode(0),iBits(-8),iPtr(aBuf),iEnd(aBuf+aSize)
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diff changeset
   390
	{}
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   391
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   392
void TBitOutput::HuffmanL(TUint aHuffCode)
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   393
/** Write a huffman code
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   394
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   395
	This expects a huffman code value as generated by Huffman::Encoding()
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diff changeset
   396
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   397
	@param "TUint aHuffCode" The huffman code write to the stream
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diff changeset
   398
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   399
	@leave "OverflowL()" If the output buffer is full, OverflowL() is called
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diff changeset
   400
*/
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diff changeset
   401
	{
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   402
	DoWriteL(aHuffCode<<(32-Huffman::KMaxCodeLength),aHuffCode>>Huffman::KMaxCodeLength);
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diff changeset
   403
	}
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diff changeset
   404
044383f39525 Convert Build package from SFL to EPL
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diff changeset
   405
void TBitOutput::WriteL(TUint aValue,TInt aLength)
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diff changeset
   406
/** Write an arbitrary integer value
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diff changeset
   407
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   408
	Write an unsigned integer using the number of bits specified. Only
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diff changeset
   409
	the low order bits of the value are written to the output, most
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diff changeset
   410
	significant bit first.
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diff changeset
   411
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   412
	@param "TUint aValue" The value to write to the stream
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diff changeset
   413
	@param "TUint aLength" The number of bits to output
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diff changeset
   414
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   415
	@leave "OverflowL()" If the output buffer is full, OverflowL() is called
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diff changeset
   416
*/
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diff changeset
   417
	{
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diff changeset
   418
	if (aLength)
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   419
		DoWriteL(aValue<<=32-aLength,aLength);
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diff changeset
   420
	}
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diff changeset
   421
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diff changeset
   422
void TBitOutput::PadL(TUint aPadding)
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diff changeset
   423
/** Pad the bitstream to the next byte boundary
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diff changeset
   424
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   425
	Terminate the bitstream by padding the last byte with the requested value.
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diff changeset
   426
	Following this operation the bitstream can continue to be used, the data will
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parents:
diff changeset
   427
	start at the next byte.
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diff changeset
   428
044383f39525 Convert Build package from SFL to EPL
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diff changeset
   429
	@param "TUint aPadding" The bit value to pad the final byte with
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diff changeset
   430
044383f39525 Convert Build package from SFL to EPL
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   431
	@leave "OverflowL()" If the output buffer is full, OverflowL() is called
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diff changeset
   432
*/
044383f39525 Convert Build package from SFL to EPL
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diff changeset
   433
	{
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diff changeset
   434
	if (iBits>-8)
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parents:
diff changeset
   435
		WriteL(aPadding?0xffffffffu:0,-iBits);
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parents:
diff changeset
   436
	}
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diff changeset
   437
044383f39525 Convert Build package from SFL to EPL
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diff changeset
   438
void TBitOutput::DoWriteL(TUint aBits,TInt aSize)
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/** Write the higher order bits to the stream
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   440
	
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	@internal
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*/
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   443
	{
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   444
	if (aSize>25)
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   445
		{
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		// cannot process >25 bits in a single pass
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   447
		// so do the top 8 bits first
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   448
		ASSERT(aSize<=32);
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   449
		DoWriteL(aBits&0xff000000u,8);
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   450
		aBits<<=8;
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   451
		aSize-=8;
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   452
		}
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   453
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   454
	TInt bits=iBits;
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   455
	TUint code=iCode|(aBits>>(bits+8));
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   456
	bits+=aSize;
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   457
	if (bits>=0)
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   458
		{
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   459
		TUint8* p=iPtr;
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   460
		do
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   461
			{
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   462
			if (p==iEnd)
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   463
				{
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   464
				// run out of buffer space so invoke the overflow handler
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   465
				iPtr=p;
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   466
				OverflowL();
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   467
				p=iPtr;
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   468
				ASSERT(p!=iEnd);
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   469
				}
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   470
			*p++=TUint8(code>>24);
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   471
			code<<=8;
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   472
			bits-=8;
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   473
			} while (bits>=0);
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   474
		iPtr=p;
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   475
		}
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   476
	iCode=code;
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   477
	iBits=bits;
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   478
	}
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   479
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   480
void TBitOutput::OverflowL()
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   481
/** Handle a full output buffer
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   482
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   483
	This virtual function is called when the output buffer is full. It should deal
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   484
	with the data in the buffer before reseting the buffer using Set(), allowing
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   485
	further data to be written.
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diff changeset
   486
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   487
	A derived class can replace this to write the data to a file (for example)
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   488
	before marking the buffer as empty.
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diff changeset
   489
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   490
	@leave "KErrOverflow" The default implementation leaves
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   491
*/
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   492
	{
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   493
	Panic(EHuffmanBufferOverflow);
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   494
	}