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89 lines
2.5 KiB
C++
Executable File
89 lines
2.5 KiB
C++
Executable File
// Compress/HuffmanDecoder.h
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#ifndef __COMPRESS_HUFFMANDECODER_H
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#define __COMPRESS_HUFFMANDECODER_H
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#include "../../../Common/Types.h"
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namespace NCompress {
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namespace NHuffman {
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const int kNumTableBits = 9;
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template <int kNumBitsMax, UInt32 m_NumSymbols>
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class CDecoder
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{
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UInt32 m_Limits[kNumBitsMax + 1]; // m_Limits[i] = value limit for symbols with length = i
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UInt32 m_Positions[kNumBitsMax + 1]; // m_Positions[i] = index in m_Symbols[] of first symbol with length = i
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UInt32 m_Symbols[m_NumSymbols];
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Byte m_Lengths[1 << kNumTableBits]; // Table oh length for short codes.
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public:
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bool SetCodeLengths(const Byte *codeLengths)
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{
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int lenCounts[kNumBitsMax + 1], tmpPositions[kNumBitsMax + 1];
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int i;
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for(i = 1; i <= kNumBitsMax; 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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int len = codeLengths[symbol];
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if (len > kNumBitsMax)
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return false;
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lenCounts[len]++;
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m_Symbols[symbol] = 0xFFFFFFFF;
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}
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lenCounts[0] = 0;
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m_Positions[0] = m_Limits[0] = 0;
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UInt32 startPos = 0;
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UInt32 index = 0;
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const UInt32 kMaxValue = (1 << kNumBitsMax);
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for (i = 1; i <= kNumBitsMax; i++)
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{
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startPos += lenCounts[i] << (kNumBitsMax - i);
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if (startPos > kMaxValue)
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return false;
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m_Limits[i] = (i == kNumBitsMax) ? kMaxValue : 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 <= kNumTableBits)
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{
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UInt32 limit = (m_Limits[i] >> (kNumBitsMax - kNumTableBits));
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for (; index < limit; index++)
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m_Lengths[index] = (Byte)i;
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}
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}
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for (symbol = 0; symbol < m_NumSymbols; symbol++)
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{
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int len = codeLengths[symbol];
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if (len != 0)
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m_Symbols[tmpPositions[len]++] = symbol;
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}
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return true;
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}
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template <class TBitDecoder>
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UInt32 DecodeSymbol(TBitDecoder *bitStream)
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{
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int numBits;
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UInt32 value = bitStream->GetValue(kNumBitsMax);
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if (value < m_Limits[kNumTableBits])
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numBits = m_Lengths[value >> (kNumBitsMax - kNumTableBits)];
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else
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for (numBits = kNumTableBits + 1; value >= m_Limits[numBits]; numBits++);
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bitStream->MovePos(numBits);
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UInt32 index = m_Positions[numBits] +
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((value - m_Limits[numBits - 1]) >> (kNumBitsMax - numBits));
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if (index >= m_NumSymbols)
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// throw CDecoderException(); // test it
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return 0xFFFFFFFF;
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return m_Symbols[index];
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}
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};
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}}
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#endif
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