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114 lines
3.2 KiB
C++
Executable File
114 lines
3.2 KiB
C++
Executable File
// Compress/HuffmanDecoder.h
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#pragma once
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#ifndef __COMPRESS_HUFFMANDECODER_H
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#define __COMPRESS_HUFFMANDECODER_H
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namespace NCompress {
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namespace NHuffman {
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class CDecoderException{};
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const UINT32 kValueTableBits = 8;
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template <int kNumBitsInLongestCode>
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class CDecoder
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{
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UINT32 m_Limitits[kNumBitsInLongestCode + 1]; // m_Limitits[i] = value limit for symbols with length = i
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UINT32 m_Positions[kNumBitsInLongestCode + 1]; // m_Positions[i] = index in m_Symbols[] of first symbol with length = i
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UINT32 m_NumSymbols;
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UINT32 *m_Symbols; // symbols: at first with len = 1 then 2, ... 15.
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BYTE m_Lengths[1 << kValueTableBits];
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public:
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CDecoder(UINT32 numSymbols):
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m_NumSymbols(numSymbols)
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{ m_Symbols = new UINT32[m_NumSymbols]; }
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~CDecoder()
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{ delete []m_Symbols; }
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void SetNumSymbols(UINT32 numSymbols)
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{ m_NumSymbols = numSymbols; }
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void SetCodeLengths(const BYTE *codeLengths);
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template <class TBitDecoder>
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UINT32 DecodeSymbol(TBitDecoder *bitStream)
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{
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UINT32 numBits;
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UINT32 value = bitStream->GetValue(kNumBitsInLongestCode);
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if (value < m_Limitits[kValueTableBits])
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numBits = m_Lengths[value >> (kNumBitsInLongestCode - kValueTableBits)];
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else if (value < m_Limitits[10])
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if (value < m_Limitits[9])
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numBits = 9;
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else
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numBits = 10;
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else if (value < m_Limitits[11])
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numBits = 11;
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else if (value < m_Limitits[12])
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numBits = 12;
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else
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for (numBits = 13; numBits < kNumBitsInLongestCode; numBits++)
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if (value < m_Limitits[numBits])
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break;
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bitStream->MovePos(numBits);
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UINT32 index = m_Positions[numBits] +
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((value - m_Limitits[numBits - 1]) >> (kNumBitsInLongestCode - numBits));
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if (index >= m_NumSymbols)
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throw CDecoderException(); // test it
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return m_Symbols[index];
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}
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};
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template <int kNumBitsInLongestCode>
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void CDecoder<kNumBitsInLongestCode>::SetCodeLengths(const BYTE *codeLengths)
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{
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int lenCounts[kNumBitsInLongestCode + 1], tmpPositions[kNumBitsInLongestCode + 1];
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int i;
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for(i = 1; i <= kNumBitsInLongestCode; i++)
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lenCounts[i] = 0;
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UINT32 symbol;
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for (symbol = 0; symbol < m_NumSymbols; symbol++)
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{
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BYTE codeLength = codeLengths[symbol];
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if (codeLength > kNumBitsInLongestCode)
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throw CDecoderException();
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lenCounts[codeLength]++;
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}
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lenCounts[0] = 0;
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tmpPositions[0] = m_Positions[0] = m_Limitits[0] = 0;
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UINT32 startPos = 0;
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UINT32 index = 0;
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const UINT32 kMaxValue = (1 << kNumBitsInLongestCode);
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for (i = 1; i <= kNumBitsInLongestCode; i++)
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{
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startPos += lenCounts[i] << (kNumBitsInLongestCode - i);
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if (startPos > kMaxValue)
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throw CDecoderException();
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m_Limitits[i] = startPos;
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m_Positions[i] = m_Positions[i - 1] + lenCounts[i - 1];
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tmpPositions[i] = m_Positions[i];
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if(i <= kValueTableBits)
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{
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UINT32 limit = (m_Limitits[i] >> (kNumBitsInLongestCode - kValueTableBits)); // change it
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memset(m_Lengths + index, BYTE(i), limit - index);
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index = limit;
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}
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}
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// if (startPos != kMaxValue)
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// throw CDecoderException();
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for (symbol = 0; symbol < m_NumSymbols; symbol++)
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if (codeLengths[symbol] != 0)
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m_Symbols[tmpPositions[codeLengths[symbol]]++] = symbol;
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}
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}}
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#endif
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