118 lines
2.0 KiB
C#
118 lines
2.0 KiB
C#
using System;
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namespace SevenZip.Compression.RangeCoder
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{
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class Decoder
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{
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public const uint kTopValue = (1 << 24);
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public uint Range;
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public uint Code;
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// public Buffer.InBuffer Stream = new Buffer.InBuffer(1 << 16);
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public System.IO.Stream Stream;
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public void Init(System.IO.Stream stream)
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{
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// Stream.Init(stream);
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Stream = stream;
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Code = 0;
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Range = 0xFFFFFFFF;
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for (int i = 0; i < 5; i++)
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Code = (Code << 8) | (byte)Stream.ReadByte();
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}
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public void ReleaseStream()
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{
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// Stream.ReleaseStream();
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Stream = null;
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}
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public void CloseStream()
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{
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Stream.Close();
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}
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public void Normalize()
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{
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while (Range < kTopValue)
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{
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Code = (Code << 8) | (byte)Stream.ReadByte();
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Range <<= 8;
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}
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}
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public void Normalize2()
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{
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if (Range < kTopValue)
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{
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Code = (Code << 8) | (byte)Stream.ReadByte();
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Range <<= 8;
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}
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}
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public uint GetThreshold(uint total)
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{
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return Code / (Range /= total);
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}
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public void Decode(uint start, uint size, uint total)
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{
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Code -= start * Range;
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Range *= size;
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Normalize();
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}
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public uint DecodeDirectBits(int numTotalBits)
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{
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uint range = Range;
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uint code = Code;
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uint result = 0;
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for (int i = numTotalBits; i > 0; i--)
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{
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range >>= 1;
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/*
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result <<= 1;
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if (code >= range)
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{
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code -= range;
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result |= 1;
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}
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*/
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uint t = (code - range) >> 31;
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code -= range & (t - 1);
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result = (result << 1) | (1 - t);
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if (range < kTopValue)
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{
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code = (code << 8) | (byte)Stream.ReadByte();
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range <<= 8;
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}
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}
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Range = range;
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Code = code;
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return result;
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}
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public uint DecodeBit(uint size0, int numTotalBits)
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{
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uint newBound = (Range >> numTotalBits) * size0;
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uint symbol;
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if (Code < newBound)
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{
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symbol = 0;
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Range = newBound;
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}
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else
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{
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symbol = 1;
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Code -= newBound;
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Range -= newBound;
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}
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Normalize();
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return symbol;
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}
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// ulong GetProcessedSize() {return Stream.GetProcessedSize(); }
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}
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}
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