diff --git a/ArcFormats/CommonStreams.cs b/ArcFormats/CommonStreams.cs
index 03e42a45..84b5aea0 100644
--- a/ArcFormats/CommonStreams.cs
+++ b/ArcFormats/CommonStreams.cs
@@ -27,6 +27,80 @@ using System;
 using System.IO;
 namespace GameRes.Formats
 {
+    /// <summary>
+    /// Base class for various filter streams.
+    /// </summary>
+    public class ProxyStream : Stream
+    {
+        Stream      m_stream;
+        bool        m_should_dispose;
+
+        public ProxyStream (Stream input, bool leave_open = false)
+        {
+            m_stream = input;
+            m_should_dispose = !leave_open;
+        }
+
+        public Stream BaseStream { get { return m_stream; } }
+
+        public override bool CanRead  { get { return m_stream.CanRead; } }
+        public override bool CanSeek  { get { return m_stream.CanSeek; } }
+        public override bool CanWrite { get { return m_stream.CanWrite; } }
+        public override long Length   { get { return m_stream.Length; } }
+        public override long Position
+        {
+            get { return m_stream.Position; }
+            set { m_stream.Position = value; }
+        }
+
+        public override int Read (byte[] buffer, int offset, int count)
+        {
+            return m_stream.Read (buffer, offset, count);
+        }
+
+        public override int ReadByte ()
+        {
+            return m_stream.ReadByte();
+        }
+
+        public override void Flush()
+        {
+            m_stream.Flush();
+        }
+
+        public override long Seek (long offset, SeekOrigin origin)
+        {
+            return m_stream.Seek (offset, origin);
+        }
+
+        public override void SetLength (long length)
+        {
+            m_stream.SetLength (length);
+        }
+
+        public override void Write (byte[] buffer, int offset, int count)
+        {
+            m_stream.Write (buffer, offset, count);
+        }
+
+        public override void WriteByte (byte value)
+        {
+            m_stream.WriteByte (value);
+        }
+
+        bool _proxy_disposed = false;
+        protected override void Dispose (bool disposing)
+        {
+            if (!_proxy_disposed)
+            {
+                if (m_should_dispose && disposing)
+                    m_stream.Dispose();
+                _proxy_disposed = true;
+                base.Dispose (disposing);
+            }
+        }
+    }
+
     public class PrefixStream : Stream
     {
         byte[]  m_header;