Keep only base/extractor.[cc|h].

third_party/lzma/v4_65/files/CS/7zip/Common/OutBuffer.cs

-// OutBuffer.cs
-
-namespace SevenZip.Buffer
-{
-        public class OutBuffer
-        {
-                byte[] m_Buffer;
-                uint m_Pos;
-                uint m_BufferSize;
-                System.IO.Stream m_Stream;
-                ulong m_ProcessedSize;
-
-                public OutBuffer(uint bufferSize)
-                {
-                        m_Buffer = new byte[bufferSize];
-                        m_BufferSize = bufferSize;
-                }
-
-                public void SetStream(System.IO.Stream stream) { m_Stream = stream; }
-                public void FlushStream() { m_Stream.Flush(); }
-                public void CloseStream() { m_Stream.Close(); }
-                public void ReleaseStream() { m_Stream = null; }
-
-                public void Init()
-                {
-                        m_ProcessedSize = 0;
-                        m_Pos = 0;
-                }
-
-                public void WriteByte(byte b)
-                {
-                        m_Buffer[m_Pos++] = b;
-                        if (m_Pos >= m_BufferSize)
-                                FlushData();
-                }
-
-                public void FlushData()
-                {
-                        if (m_Pos == 0)
-                                return;
-                        m_Stream.Write(m_Buffer, 0, (int)m_Pos);
-                        m_Pos = 0;
-                }
-
-                public ulong GetProcessedSize() { return m_ProcessedSize + m_Pos; }
-        }
-}