60 lines
1.3 KiB
C#
60 lines
1.3 KiB
C#
using System;
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namespace SevenZip.Compression.RangeCoder
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{
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struct BitTreeDecoder
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{
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BitDecoder[] Models;
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int NumBitLevels;
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public BitTreeDecoder(int numBitLevels)
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{
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NumBitLevels = numBitLevels;
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Models = new BitDecoder[1 << numBitLevels];
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}
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public void Init()
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{
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for (uint i = 1; i < (1 << NumBitLevels); i++)
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Models[i].Init();
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}
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public uint Decode(RangeCoder.Decoder rangeDecoder)
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{
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uint m = 1;
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for (int bitIndex = NumBitLevels; bitIndex > 0; bitIndex--)
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m = (m << 1) + Models[m].Decode(rangeDecoder);
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return m - ((uint)1 << NumBitLevels);
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}
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public uint ReverseDecode(RangeCoder.Decoder rangeDecoder)
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{
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uint m = 1;
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uint symbol = 0;
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for (int bitIndex = 0; bitIndex < NumBitLevels; bitIndex++)
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{
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uint bit = Models[m].Decode(rangeDecoder);
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m <<= 1;
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m += bit;
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symbol |= (bit << bitIndex);
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}
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return symbol;
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}
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public static uint ReverseDecode(BitDecoder[] Models, UInt32 startIndex,
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RangeCoder.Decoder rangeDecoder, int NumBitLevels)
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{
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uint m = 1;
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uint symbol = 0;
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for (int bitIndex = 0; bitIndex < NumBitLevels; bitIndex++)
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{
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uint bit = Models[startIndex + m].Decode(rangeDecoder);
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m <<= 1;
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m += bit;
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symbol |= (bit << bitIndex);
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}
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return symbol;
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}
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}
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}
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