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Diffstat (limited to 'CPP/7zip/Compress/Huffman/HuffmanDecoder.h')
-rwxr-xr-x | CPP/7zip/Compress/Huffman/HuffmanDecoder.h | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/CPP/7zip/Compress/Huffman/HuffmanDecoder.h b/CPP/7zip/Compress/Huffman/HuffmanDecoder.h new file mode 100755 index 00000000..57115197 --- /dev/null +++ b/CPP/7zip/Compress/Huffman/HuffmanDecoder.h @@ -0,0 +1,88 @@ +// Compress/HuffmanDecoder.h + +#ifndef __COMPRESS_HUFFMANDECODER_H +#define __COMPRESS_HUFFMANDECODER_H + +#include "../../../Common/Types.h" + +namespace NCompress { +namespace NHuffman { + +const int kNumTableBits = 9; + +template <int kNumBitsMax, UInt32 m_NumSymbols> +class CDecoder +{ + UInt32 m_Limits[kNumBitsMax + 1]; // m_Limits[i] = value limit for symbols with length = i + UInt32 m_Positions[kNumBitsMax + 1]; // m_Positions[i] = index in m_Symbols[] of first symbol with length = i + UInt32 m_Symbols[m_NumSymbols]; + Byte m_Lengths[1 << kNumTableBits]; // Table oh length for short codes. + +public: + + bool SetCodeLengths(const Byte *codeLengths) + { + int lenCounts[kNumBitsMax + 1], tmpPositions[kNumBitsMax + 1]; + int i; + for(i = 1; i <= kNumBitsMax; i++) + lenCounts[i] = 0; + UInt32 symbol; + for (symbol = 0; symbol < m_NumSymbols; symbol++) + { + int len = codeLengths[symbol]; + if (len > kNumBitsMax) + return false; + lenCounts[len]++; + m_Symbols[symbol] = 0xFFFFFFFF; + } + lenCounts[0] = 0; + m_Positions[0] = m_Limits[0] = 0; + UInt32 startPos = 0; + UInt32 index = 0; + const UInt32 kMaxValue = (1 << kNumBitsMax); + for (i = 1; i <= kNumBitsMax; i++) + { + startPos += lenCounts[i] << (kNumBitsMax - i); + if (startPos > kMaxValue) + return false; + m_Limits[i] = (i == kNumBitsMax) ? kMaxValue : startPos; + m_Positions[i] = m_Positions[i - 1] + lenCounts[i - 1]; + tmpPositions[i] = m_Positions[i]; + if(i <= kNumTableBits) + { + UInt32 limit = (m_Limits[i] >> (kNumBitsMax - kNumTableBits)); + for (; index < limit; index++) + m_Lengths[index] = (Byte)i; + } + } + for (symbol = 0; symbol < m_NumSymbols; symbol++) + { + int len = codeLengths[symbol]; + if (len != 0) + m_Symbols[tmpPositions[len]++] = symbol; + } + return true; + } + + template <class TBitDecoder> + UInt32 DecodeSymbol(TBitDecoder *bitStream) + { + int numBits; + UInt32 value = bitStream->GetValue(kNumBitsMax); + if (value < m_Limits[kNumTableBits]) + numBits = m_Lengths[value >> (kNumBitsMax - kNumTableBits)]; + else + for (numBits = kNumTableBits + 1; value >= m_Limits[numBits]; numBits++); + bitStream->MovePos(numBits); + UInt32 index = m_Positions[numBits] + + ((value - m_Limits[numBits - 1]) >> (kNumBitsMax - numBits)); + if (index >= m_NumSymbols) + // throw CDecoderException(); // test it + return 0xFFFFFFFF; + return m_Symbols[index]; + } +}; + +}} + +#endif |