diff -r 000000000000 -r 83f4b4db085c toolsandutils/e32tools/elf2e32/source/huffman.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolsandutils/e32tools/elf2e32/source/huffman.cpp	Tue Feb 02 01:39:43 2010 +0200
@@ -0,0 +1,917 @@
+// 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 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:
+// 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;
+	}
+	else if (l==aValue)
+	{
+		TUint term0=*aValue--;						// 0-term
+		aPtr=HuffmanSubTree(aPtr,aValue,aLevel);	// 1-tree
+		*--aPtr=KBranch1|(term0>>16);
+	}
+	else	// l<iNext
+	{
+		TUint term0=*aValue--;						// 0-term
+		TUint term1=*aValue--;
+		*--aPtr=(term1>>16<<16)|(term0>>16);
+	}
+	return aPtr;
+}
+
+/**
+Create a canonical Huffman decoding tree
+
+This generates the huffman decoding tree used by TBitInput::HuffmanL() to read 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 aDecodeTree[]" The space for the decoding tree. This must be the same
+size as the code-length table, and can safely be the same memory
+@param "TInt aSymbolBase" the base value for the output 'symbols' from the decoding tree, by default
+this is zero.
+
+@panic "USER ???" If the provided code is not a valid Huffman coding
+
+@see IsValid()
+@see HuffmanL()
+*/
+void Huffman::Decoding(const TUint32 aHuffman[],TInt aNumCodes,TUint32 aDecodeTree[],TInt aSymbolBase)
+{
+	if(!IsValid(aHuffman,aNumCodes))
+		throw E32ImageCompressionError(HUFFMANINVALIDCODINGERROR);
+
+	TFixedArray<TInt,KMaxCodeLength> counts;
+	counts.Reset();
+	TInt codes=0;
+	TInt ii;
+	for (ii=0;ii<aNumCodes;++ii)
+	{
+		TInt len=aHuffman[ii];
+		aDecodeTree[ii]=len;
+		if (--len>=0)
+		{
+			++counts[len];
+			++codes;
+		}
+	}
+
+	TFixedArray<TUint32*,KMaxCodeLength> level;
+	TUint32* lit=aDecodeTree+codes;
+	for (ii=0;ii<KMaxCodeLength;++ii)
+	{
+		level[ii]=lit;
+		lit-=counts[ii];
+	}
+	
+	aSymbolBase=(aSymbolBase<<17)+(KHuffTerminate<<16);
+	for (ii=0;ii<aNumCodes;++ii)
+	{
+		TUint len=TUint8(aDecodeTree[ii]);
+		if (len)
+			*--level[len-1]|=(ii<<17)+aSymbolBase;
+	}
+	
+	if (codes==1)	// codes==1 special case: tree isn't complete
+	{
+		TUint term=aDecodeTree[0]>>16;
+		aDecodeTree[0]=term|(term<<16); // 0- and 1-terminate at root
+	}
+	else if (codes>1)
+		HuffmanSubTree(aDecodeTree+codes-1,aDecodeTree+codes-1,&level[0]);
+}
+
+/**
+The decoding tree for the externalised code
+*/
+const TUint32 HuffmanDecoding[]=
+{
+	0x0004006c,
+	0x00040064,
+	0x0004005c,
+	0x00040050,
+	0x00040044,
+	0x0004003c,
+	0x00040034,
+	0x00040021,
+	0x00040023,
+	0x00040025,
+	0x00040027,
+	0x00040029,
+	0x00040014,
+	0x0004000c,
+	0x00040035,
+	0x00390037,
+	0x00330031,
+	0x0004002b,
+	0x002f002d,
+	0x001f001d,
+	0x001b0019,
+	0x00040013,
+	0x00170015,
+	0x0004000d,
+	0x0011000f,
+	0x000b0009,
+	0x00070003,
+	0x00050001
+};
+
+
+/**
+Restore a canonical huffman encoding from a bit stream
+
+The encoding must have been stored using Huffman::ExternalizeL(). The resulting
+code-length table can be used to create an encoding table using Huffman::Encoding()
+or a decoding tree using Huffman::Decoding().
+	
+@param "TBitInput& aInput" The input stream with the encoding
+@param "TUint32 aHuffman[]" The internalized code-length table is placed here
+@param "TInt aNumCodes" The number of huffman codes in the table
+
+@leave "TBitInput::HuffmanL()"
+
+@see ExternalizeL()
+See ExternalizeL for a description of the format
+*/
+void Huffman::InternalizeL(TBitInput& aInput,TUint32 aHuffman[],TInt aNumCodes)
+{
+	// initialise move-to-front list
+	TFixedArray<TUint8,Huffman::KMetaCodes> list;
+	for (TInt i=0;i<list.Count();++i)
+		list[i]=TUint8(i);
+
+	TInt last=0;
+	// extract codes, reverse rle-0 and mtf encoding in one pass
+	TUint32* p=aHuffman;
+	const TUint32* end=aHuffman+aNumCodes;
+	TInt rl=0;
+	while (p+rl<end)
+	{
+		TInt c=aInput.HuffmanL(HuffmanDecoding);
+		if (c<2)
+		{
+			// one of the zero codes used by RLE-0
+			// update he run-length
+			rl+=rl+c+1;
+		}
+		else
+		{
+			while (rl>0)
+			{
+				if (p>end)
+				{
+					throw E32ImageCompressionError(HUFFMANINVALIDCODINGERROR);
+				}
+				*p++=last;
+				--rl;
+			}
+			--c;
+			list[0]=TUint8(last);
+			last=list[c];
+			
+			memmove((void * const)&list[1],(const void * const)&list[0],(size_t)c);
+			if (p>end)
+			{
+				throw E32ImageCompressionError(HUFFMANINVALIDCODINGERROR);
+			}
+			*p++=last;
+		}
+	}
+	while (rl>0)
+	{
+		if (p>end)
+		{
+			throw E32ImageCompressionError(HUFFMANINVALIDCODINGERROR);
+		}
+		*p++=last;
+		--rl;
+	}
+}
+
+/**
+bit-stream input class
+Reverse the byte-order of a 32 bit value
+This generates optimal ARM code (4 instructions)
+*/
+inline TUint reverse(TUint aVal)
+{
+	TUint v=(aVal<<16)|(aVal>>16);
+	v^=aVal;
+	v&=0xff00ffff;
+	aVal=(aVal>>8)|(aVal<<24);
+	return aVal^(v>>8);
+}
+
+/**
+Construct a bit stream input object
+
+Following construction the bit stream is ready for reading bits, but will
+immediately call UnderflowL() as the input buffer is empty.
+*/
+TBitInput::TBitInput():iCount(0),iRemain(0)
+{
+
+}
+
+/**
+Construct a bit stream input object over a buffer
+
+Following construction the bit stream is ready for reading bits from the specified buffer.
+
+@param "const TUint8* aPtr" The address of the buffer containing the bit stream
+@param "TInt aLength" The length of the bitstream in bits
+@param "TInt aOffset" The bit offset from the start of the buffer to the bit stream (defaults to zero)
+*/
+TBitInput::TBitInput(const TUint8* aPtr, TInt aLength, TInt aOffset)
+{
+	Set(aPtr,aLength,aOffset);
+}
+
+/**
+Set the memory buffer to use for input.
+
+Bits will be read from this buffer until it is empty, at which point UnderflowL() will be called.
+	
+@param "const TUint8* aPtr" The address of the buffer containing the bit stream
+@param "TInt aLength" The length of the bitstream in bits
+@param "TInt aOffset" The bit offset from the start of the buffer to the bit stream (defaults to zero)
+*/
+void TBitInput::Set(const TUint8* aPtr, TInt aLength, TInt aOffset)
+{
+	TUint p=(TUint)aPtr;
+	p+=aOffset>>3;			// nearest byte to the specified bit offset
+	aOffset&=7;				// bit offset within the byte
+	const TUint32* ptr=(const TUint32*)(p&~3);	// word containing this byte
+	aOffset+=(p&3)<<3;		// bit offset within the word
+	if (aLength==0)
+		iCount=0;
+	else
+	{
+		// read the first few bits of the stream
+		iBits=reverse(*ptr++)<<aOffset;
+		aOffset=32-aOffset;
+		aLength-=aOffset;
+		if (aLength<0)
+			aOffset+=aLength;
+		iCount=aOffset;
+	}
+	iRemain=aLength;
+	iPtr=ptr;
+}
+
+#ifndef __HUFFMAN_MACHINE_CODED__
+
+/**
+Read a single bit from the input
+
+Return the next bit in the input stream. This will call UnderflowL() if there are no more
+bits available.
+
+@return The next bit in the stream
+
+@leave "UnderflowL()" It the bit stream is exhausted more UnderflowL is called to get more
+data
+*/
+TUint TBitInput::ReadL()
+{
+	TInt c=iCount;
+	TUint bits=iBits;
+	if (--c<0)
+		return ReadL(1);
+	iCount=c;
+	iBits=bits<<1;
+	return bits>>31;
+}
+
+/**
+Read a multi-bit value from the input
+
+Return the next few bits as an unsigned integer. The last bit read is the least significant
+bit of the returned value, and the value is zero extended to return a 32-bit result.
+
+A read of zero bits will always reaturn zero.
+	
+This will call UnderflowL() if there are not enough bits available.
+
+@param "TInt aSize" The number of bits to read
+
+@return The bits read from the stream
+
+@leave "UnderflowL()" It the bit stream is exhausted more UnderflowL is called to get more
+data
+*/
+TUint TBitInput::ReadL(TInt aSize)
+{
+	if (!aSize)
+		return 0;
+	TUint val=0;
+	TUint bits=iBits;
+	iCount-=aSize;
+	while (iCount<0)
+	{
+		// need more bits
+#ifdef __CPU_X86
+		// X86 does not allow shift-by-32
+		if (iCount+aSize!=0)
+			val|=bits>>(32-(iCount+aSize))<<(-iCount);	// scrub low order bits
+#else
+		val|=bits>>(32-(iCount+aSize))<<(-iCount);	// scrub low order bits
+#endif
+		aSize=-iCount;	// bits still required
+		if (iRemain>0)
+		{
+			bits=reverse(*iPtr++);
+			iCount+=32;
+			iRemain-=32;
+			if (iRemain<0)
+				iCount+=iRemain;
+		}
+		else
+		{
+			UnderflowL();
+			bits=iBits;
+			iCount-=aSize;
+		}
+	}
+
+#ifdef __CPU_X86
+	// X86 does not allow shift-by-32
+	iBits=aSize==32?0:bits<<aSize;
+#else
+	iBits=bits<<aSize;
+#endif
+
+	return val|(bits>>(32-aSize));
+}
+
+/**
+Read and decode a Huffman Code
+
+Interpret the next bits in the input as a Huffman code in the specified decoding.
+The decoding tree should be the output from Huffman::Decoding().
+
+@param "const TUint32* aTree" The huffman decoding tree
+
+@return The symbol that was decoded
+	
+@leave "UnderflowL()" It the bit stream is exhausted more UnderflowL is called to get more
+data
+*/
+TUint TBitInput::HuffmanL(const TUint32* aTree)
+{
+	TUint huff=0;
+	do
+	{
+		aTree=(const TUint32*)(((TUint8*)aTree)+(huff>>16));
+		huff=*aTree;
+		if (ReadL()==0)
+			huff<<=16;
+	} while ((huff&0x10000u)==0);
+	
+	return huff>>17;
+}
+
+#endif
+
+/**
+Handle an empty input buffer
+
+This virtual function is called when the input buffer is empty and more bits are required.
+It should reset the input buffer with more data using Set().
+
+A derived class can replace this to read the data from a file (for example) before reseting
+the input buffer.
+
+@leave "KErrUnderflow" The default implementation leaves
+*/
+void TBitInput::UnderflowL()
+{
+	throw E32ImageCompressionError(HUFFMANBUFFEROVERFLOWERROR);
+}
+