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https://github.com/ddnet/ddnet.git
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278 lines
6.3 KiB
C++
278 lines
6.3 KiB
C++
#include <base/system.h>
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#include "huffman.h"
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struct CHuffmanConstructNode
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{
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unsigned short m_NodeId;
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int m_Frequency;
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};
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void CHuffman::Setbits_r(CNode *pNode, int Bits, unsigned Depth)
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{
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if(pNode->m_aLeafs[1] != 0xffff)
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Setbits_r(&m_aNodes[pNode->m_aLeafs[1]], Bits|(1<<Depth), Depth+1);
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if(pNode->m_aLeafs[0] != 0xffff)
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Setbits_r(&m_aNodes[pNode->m_aLeafs[0]], Bits, Depth+1);
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if(pNode->m_NumBits)
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{
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pNode->m_Bits = Bits;
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pNode->m_NumBits = Depth;
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}
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}
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// TODO: this should be something faster, but it's enough for now
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static void BubbleSort(CHuffmanConstructNode **ppList, int Size)
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{
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int Changed = 1;
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CHuffmanConstructNode *pTemp;
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while(Changed)
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{
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Changed = 0;
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for(int i = 0; i < Size-1; i++)
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{
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if(ppList[i]->m_Frequency < ppList[i+1]->m_Frequency)
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{
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pTemp = ppList[i];
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ppList[i] = ppList[i+1];
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ppList[i+1] = pTemp;
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Changed = 1;
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}
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}
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Size--;
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}
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}
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void CHuffman::ConstructTree(const unsigned *pFrequencies)
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{
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CHuffmanConstructNode aNodesLeftStorage[HUFFMAN_MAX_SYMBOLS];
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CHuffmanConstructNode *apNodesLeft[HUFFMAN_MAX_SYMBOLS];
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int NumNodesLeft = HUFFMAN_MAX_SYMBOLS;
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// add the symbols
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for(int i = 0; i < HUFFMAN_MAX_SYMBOLS; i++)
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{
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m_aNodes[i].m_NumBits = 0xFFFFFFFF;
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m_aNodes[i].m_Symbol = i;
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m_aNodes[i].m_aLeafs[0] = -1;
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m_aNodes[i].m_aLeafs[1] = -1;
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if(i == HUFFMAN_EOF_SYMBOL)
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aNodesLeftStorage[i].m_Frequency = 1;
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else
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aNodesLeftStorage[i].m_Frequency = pFrequencies[i];
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aNodesLeftStorage[i].m_NodeId = i;
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apNodesLeft[i] = &aNodesLeftStorage[i];
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}
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m_NumNodes = HUFFMAN_MAX_SYMBOLS;
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// construct the table
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while(NumNodesLeft > 1)
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{
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// we can't rely on stdlib's qsort for this, it can generate different results on different implementations
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BubbleSort(apNodesLeft, NumNodesLeft);
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m_aNodes[m_NumNodes].m_NumBits = 0;
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m_aNodes[m_NumNodes].m_aLeafs[0] = apNodesLeft[NumNodesLeft-1]->m_NodeId;
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m_aNodes[m_NumNodes].m_aLeafs[1] = apNodesLeft[NumNodesLeft-2]->m_NodeId;
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apNodesLeft[NumNodesLeft-2]->m_NodeId = m_NumNodes;
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apNodesLeft[NumNodesLeft-2]->m_Frequency = apNodesLeft[NumNodesLeft-1]->m_Frequency + apNodesLeft[NumNodesLeft-2]->m_Frequency;
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m_NumNodes++;
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NumNodesLeft--;
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}
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// set start node
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m_pStartNode = &m_aNodes[m_NumNodes-1];
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// build symbol bits
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Setbits_r(m_pStartNode, 0, 0);
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}
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void CHuffman::Init(const unsigned *pFrequencies)
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{
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int i;
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// make sure to cleanout every thing
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mem_zero(this, sizeof(*this));
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// construct the tree
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ConstructTree(pFrequencies);
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// build decode LUT
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for(i = 0; i < HUFFMAN_LUTSIZE; i++)
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{
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unsigned Bits = i;
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int k;
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CNode *pNode = m_pStartNode;
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for(k = 0; k < HUFFMAN_LUTBITS; k++)
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{
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pNode = &m_aNodes[pNode->m_aLeafs[Bits&1]];
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Bits >>= 1;
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if(!pNode)
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break;
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if(pNode->m_NumBits)
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{
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m_apDecodeLut[i] = pNode;
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break;
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}
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}
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if(k == HUFFMAN_LUTBITS)
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m_apDecodeLut[i] = pNode;
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}
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}
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//***************************************************************
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int CHuffman::Compress(const void *pInput, int InputSize, void *pOutput, int OutputSize)
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{
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// this macro loads a symbol for a byte into bits and bitcount
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#define HUFFMAN_MACRO_LOADSYMBOL(Sym) \
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Bits |= m_aNodes[Sym].m_Bits << Bitcount; \
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Bitcount += m_aNodes[Sym].m_NumBits;
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// this macro writes the symbol stored in bits and bitcount to the dst pointer
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#define HUFFMAN_MACRO_WRITE() \
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while(Bitcount >= 8) \
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{ \
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*pDst++ = (unsigned char)(Bits&0xff); \
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if(pDst == pDstEnd) \
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return -1; \
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Bits >>= 8; \
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Bitcount -= 8; \
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}
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// setup buffer pointers
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const unsigned char *pSrc = (const unsigned char *)pInput;
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const unsigned char *pSrcEnd = pSrc + InputSize;
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unsigned char *pDst = (unsigned char *)pOutput;
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unsigned char *pDstEnd = pDst + OutputSize;
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// symbol variables
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unsigned Bits = 0;
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unsigned Bitcount = 0;
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// make sure that we have data that we want to compress
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if(InputSize)
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{
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// {A} load the first symbol
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int Symbol = *pSrc++;
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while(pSrc != pSrcEnd)
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{
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// {B} load the symbol
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HUFFMAN_MACRO_LOADSYMBOL(Symbol)
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// {C} fetch next symbol, this is done here because it will reduce dependency in the code
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Symbol = *pSrc++;
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// {B} write the symbol loaded at
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HUFFMAN_MACRO_WRITE()
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}
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// write the last symbol loaded from {C} or {A} in the case of only 1 byte input buffer
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HUFFMAN_MACRO_LOADSYMBOL(Symbol)
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HUFFMAN_MACRO_WRITE()
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}
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// write EOF symbol
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HUFFMAN_MACRO_LOADSYMBOL(HUFFMAN_EOF_SYMBOL)
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HUFFMAN_MACRO_WRITE()
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// write out the last bits
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*pDst++ = Bits;
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// return the size of the output
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return (int)(pDst - (const unsigned char *)pOutput);
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// remove macros
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#undef HUFFMAN_MACRO_LOADSYMBOL
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#undef HUFFMAN_MACRO_WRITE
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}
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//***************************************************************
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int CHuffman::Decompress(const void *pInput, int InputSize, void *pOutput, int OutputSize)
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{
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// setup buffer pointers
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unsigned char *pDst = (unsigned char *)pOutput;
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unsigned char *pSrc = (unsigned char *)pInput;
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unsigned char *pDstEnd = pDst + OutputSize;
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unsigned char *pSrcEnd = pSrc + InputSize;
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unsigned Bits = 0;
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unsigned Bitcount = 0;
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CNode *pEof = &m_aNodes[HUFFMAN_EOF_SYMBOL];
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CNode *pNode = 0;
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while(1)
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{
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// {A} try to load a node now, this will reduce dependency at location {D}
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pNode = 0;
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if(Bitcount >= HUFFMAN_LUTBITS)
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pNode = m_apDecodeLut[Bits&HUFFMAN_LUTMASK];
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// {B} fill with new bits
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while(Bitcount < 24 && pSrc != pSrcEnd)
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{
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Bits |= (*pSrc++) << Bitcount;
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Bitcount += 8;
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}
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// {C} load symbol now if we didn't that earlier at location {A}
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if(!pNode)
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pNode = m_apDecodeLut[Bits&HUFFMAN_LUTMASK];
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// {D} check if we hit a symbol already
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if(pNode->m_NumBits)
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{
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// remove the bits for that symbol
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Bits >>= pNode->m_NumBits;
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Bitcount -= pNode->m_NumBits;
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}
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else
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{
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// remove the bits that the lut checked up for us
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Bits >>= HUFFMAN_LUTBITS;
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Bitcount -= HUFFMAN_LUTBITS;
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// walk the tree bit by bit
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while(1)
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{
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// traverse tree
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pNode = &m_aNodes[pNode->m_aLeafs[Bits&1]];
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// remove bit
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Bitcount--;
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Bits >>= 1;
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// check if we hit a symbol
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if(pNode->m_NumBits)
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break;
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// no more bits, decoding error
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if(Bitcount == 0)
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return -1;
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}
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}
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// check for eof
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if(pNode == pEof)
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break;
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// output character
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if(pDst == pDstEnd)
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return -1;
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*pDst++ = pNode->m_Symbol;
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}
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// return the size of the decompressed buffer
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return (int)(pDst - (const unsigned char *)pOutput);
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}
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