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// RangeCoder.cs
//
// Copyright (C) 2009 Bartek Jasicki based on LZMA SDK
//
// This file is part of Grubng
//
// Grubng is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
using System;
namespace Grubng
{
sealed class RangeEncoder : IDisposable
{
public const uint kTopValue = (1 << 24);
System.IO.Stream Stream;
public UInt64 Low;
public uint Range;
uint _cacheSize;
byte _cache;
/// <summary>
/// Check if resources are disposed.
/// </summary>
bool disposedres;
public void SetStream(System.IO.Stream stream)
{
this.DisposeCheck();
Stream = stream;
}
public void ReleaseStream()
{
this.DisposeCheck();
Stream.Close();
}
public void Init()
{
this.DisposeCheck();
Low = 0;
Range = 0xFFFFFFFF;
_cacheSize = 1;
_cache = 0;
}
public void FlushData()
{
this.DisposeCheck();
for (int i = 0; i < 5; i++)
ShiftLow();
}
public void FlushStream()
{
this.DisposeCheck();
Stream.Flush();
}
public void ShiftLow()
{
this.DisposeCheck();
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)
{
this.DisposeCheck();
for (int i = numTotalBits - 1; i >= 0; i--)
{
Range >>= 1;
if (((v >> i) & 1) == 1)
Low += Range;
if (Range < kTopValue)
{
Range <<= 8;
ShiftLow();
}
}
}
/// <summary>
/// Check for dispose. If was called, throw exception
/// </summary>
void DisposeCheck()
{
if (this.disposedres)
{
throw new ObjectDisposedException(GetType().Name);
}
}
/// <summary>
/// Function dispose unmanaged resources.
/// </summary>
public void Dispose()
{
if (!this.disposedres)
{
this.Stream.Dispose();
this.disposedres = true;
}
}
}
}
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