lzoutwindow.cs

LZMA 是 7-Zip 程序中 7z 格式 的默认压缩算法。LZMA 能提供给用户极高的压缩比及较快的压缩速度

// LzOutWindow.cs

namespace SevenZip.Compression.LZ
{
	public class OutWindow
	{
		byte[] _buffer = null;
		uint _pos;
		uint _windowSize = 0;
		uint _streamPos;
		System.IO.Stream _stream;

		public void Create(uint windowSize)
		{
			if (_windowSize != windowSize)
			{
				// System.GC.Collect();
				_buffer = new byte[windowSize];
			}
			_windowSize = windowSize;
			_pos = 0;
			_streamPos = 0;
		}

		public void Init(System.IO.Stream stream, bool solid)
		{
			ReleaseStream();
			_stream = stream;
			if (!solid)
			{
				_streamPos = 0;
				_pos = 0;
			}
		}

		public void Init(System.IO.Stream stream) { Init(stream, false); }

		public void ReleaseStream()
		{
			Flush();
			_stream = null;
		}

		public void Flush()
		{
			uint size = _pos - _streamPos;
			if (size == 0)
				return;
			_stream.Write(_buffer, (int)_streamPos, (int)size);
			if (_pos >= _windowSize)
				_pos = 0;
			_streamPos = _pos;
		}

		public void CopyBlock(uint distance, uint len)
		{
			uint pos = _pos - distance - 1;
			if (pos >= _windowSize)
				pos += _windowSize;
			for (; len > 0; len--)
			{
				if (pos >= _windowSize)
					pos = 0;
				_buffer[_pos++] = _buffer[pos++];
				if (_pos >= _windowSize)
					Flush();
			}
		}

		public void PutByte(byte b)
		{
			_buffer[_pos++] = b;
			if (_pos >= _windowSize)
				Flush();
		}

		public byte GetByte(uint distance)
		{
			uint pos = _pos - distance - 1;
			if (pos >= _windowSize)
				pos += _windowSize;
			return _buffer[pos];
		}
	}
}