Bit stream on top of the IO.Stream

ArcFormats/BitStream.cs

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+//! \file       BitStream.cs
+//! \date       Sat Aug 22 21:33:39 2015
+//! \brief      Bit stream on top of the IO.Stream
+//
+// Copyright (C) 2015 by morkt
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//
+
+using System;
+using System.Diagnostics;
+using System.IO;
+
+namespace GameRes.Formats
+{
+    public class MsbBitStream : IDisposable
+    {
+        Stream      m_input;
+        bool        m_should_dispose;
+
+        public Stream Input { get { return m_input; } }
+
+        public MsbBitStream (Stream file, bool leave_open = false)
+        {
+            m_input = file;
+            m_should_dispose = !leave_open;
+        }
+
+        int m_bits = 0;
+        int m_cached_bits = 0;
+
+        public int GetNextBit ()
+        {
+            return GetBits (1);
+        }
+
+        public int GetBits (int count)
+        {
+            Debug.Assert (count <= 24, "MsbBitStream does not support sequences longer than 24 bits");
+            while (m_cached_bits < count)
+            {
+                int b = m_input.ReadByte();
+                if (-1 == b)
+                    return -1;
+                m_bits = (m_bits << 8) | b;
+                m_cached_bits += 8;
+            }
+            int mask = (1 << count) - 1;
+            m_cached_bits -= count;
+            return (m_bits >> m_cached_bits) & mask;
+        }
+
+        #region IDisposable Members
+        bool m_disposed = false;
+
+        public void Dispose ()
+        {
+            Dispose (true);
+            GC.SuppressFinalize (this);
+        }
+
+        protected virtual void Dispose (bool disposing)
+        {
+            if (!m_disposed)
+            {
+                if (disposing && m_should_dispose && null != m_input)
+                    m_input.Dispose();
+                m_disposed = true;
+            }
+        }
+        #endregion
+    }
+}