tor-browser

RangeCoder.cs (4190B)

---

using System;

namespace SevenZip.Compression.RangeCoder
{
class Encoder
{
	public const uint kTopValue = (1 << 24);

	System.IO.Stream Stream;

	public UInt64 Low;
	public uint Range;
	uint _cacheSize;
	byte _cache;

	long StartPosition;

	public void SetStream(System.IO.Stream stream)
	{
		Stream = stream;
	}

	public void ReleaseStream()
	{
		Stream = null;
	}

	public void Init()
	{
		StartPosition = Stream.Position;

		Low = 0;
		Range = 0xFFFFFFFF;
		_cacheSize = 1;
		_cache = 0;
	}

	public void FlushData()
	{
		for (int i = 0; i < 5; i++)
			ShiftLow();
	}

	public void FlushStream()
	{
		Stream.Flush();
	}

	public void CloseStream()
	{
		Stream.Close();
	}

	public void Encode(uint start, uint size, uint total)
	{
		Low += start * (Range /= total);
		Range *= size;
		while (Range < kTopValue)
		{
			Range <<= 8;
			ShiftLow();
		}
	}

	public void ShiftLow()
	{
		if ((uint)Low < (uint)0xFF000000 || (uint)(Low >> 32) == 1)
		{
			byte temp = _cache;
			do
			{
				Stream.WriteByte((byte)(temp + (Low >> 32)));
				temp = 0xFF;
			}
			while (--_cacheSize != 0);
			_cache = (byte)(((uint)Low) >> 24);
		}
		_cacheSize++;
		Low = ((uint)Low) << 8;
	}

	public void EncodeDirectBits(uint v, int numTotalBits)
	{
		for (int i = numTotalBits - 1; i >= 0; i--)
		{
			Range >>= 1;
			if (((v >> i) & 1) == 1)
				Low += Range;
			if (Range < kTopValue)
			{
				Range <<= 8;
				ShiftLow();
			}
		}
	}

	public void EncodeBit(uint size0, int numTotalBits, uint symbol)
	{
		uint newBound = (Range >> numTotalBits) * size0;
		if (symbol == 0)
			Range = newBound;
		else
		{
			Low += newBound;
			Range -= newBound;
		}
		while (Range < kTopValue)
		{
			Range <<= 8;
			ShiftLow();
		}
	}

	public long GetProcessedSizeAdd()
	{
		return _cacheSize +
			Stream.Position - StartPosition + 4;
		// (long)Stream.GetProcessedSize();
	}
}

class Decoder
{
	public const uint kTopValue = (1 << 24);
	public uint Range;
	public uint Code;
	// public Buffer.InBuffer Stream = new Buffer.InBuffer(1 << 16);
	public System.IO.Stream Stream;

	public void Init(System.IO.Stream stream)
	{
		// Stream.Init(stream);
		Stream = stream;

		Code = 0;
		Range = 0xFFFFFFFF;
		for (int i = 0; i < 5; i++)
			Code = (Code << 8) | (byte)Stream.ReadByte();
	}

	public void ReleaseStream()
	{
		// Stream.ReleaseStream();
		Stream = null;
	}

	public void CloseStream()
	{
		Stream.Close();
	}

	public void Normalize()
	{
		while (Range < kTopValue)
		{
			Code = (Code << 8) | (byte)Stream.ReadByte();
			Range <<= 8;
		}
	}

	public void Normalize2()
	{
		if (Range < kTopValue)
		{
			Code = (Code << 8) | (byte)Stream.ReadByte();
			Range <<= 8;
		}
	}

	public uint GetThreshold(uint total)
	{
		return Code / (Range /= total);
	}

	public void Decode(uint start, uint size, uint total)
	{
		Code -= start * Range;
		Range *= size;
		Normalize();
	}

	public uint DecodeDirectBits(int numTotalBits)
	{
		uint range = Range;
		uint code = Code;
		uint result = 0;
		for (int i = numTotalBits; i > 0; i--)
		{
			range >>= 1;
			/*
			result <<= 1;
			if (code >= range)
			{
				code -= range;
				result |= 1;
			}
			*/
			uint t = (code - range) >> 31;
			code -= range & (t - 1);
			result = (result << 1) | (1 - t);

			if (range < kTopValue)
			{
				code = (code << 8) | (byte)Stream.ReadByte();
				range <<= 8;
			}
		}
		Range = range;
		Code = code;
		return result;
	}

	public uint DecodeBit(uint size0, int numTotalBits)
	{
		uint newBound = (Range >> numTotalBits) * size0;
		uint symbol;
		if (Code < newBound)
		{
			symbol = 0;
			Range = newBound;
		}
		else
		{
			symbol = 1;
			Code -= newBound;
			Range -= newBound;
		}
		Normalize();
		return symbol;
	}

	// ulong GetProcessedSize() {return Stream.GetProcessedSize(); }
}
}