diff --git a/common/rdr/MemOutStream.h b/common/rdr/MemOutStream.h
new file mode 100644
index 0000000..ee3e950
--- /dev/null
+++ b/common/rdr/MemOutStream.h
@@ -0,0 +1,83 @@
+/* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
+ * 
+ * This 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 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * This software 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 software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+//
+// A MemOutStream grows as needed when data is written to it.
+//
+
+#ifndef __RDR_MEMOUTSTREAM_H__
+#define __RDR_MEMOUTSTREAM_H__
+
+#include <rdr/OutStream.h>
+
+namespace rdr {
+
+  class MemOutStream : public OutStream {
+
+  public:
+
+    MemOutStream(int len=1024) {
+      start = ptr = new U8[len];
+      end = start + len;
+    }
+
+    virtual ~MemOutStream() {
+      delete [] start;
+    }
+
+    void writeBytes(const void* data, int length) {
+      check(length);
+      memcpy(ptr, data, length);
+      ptr += length;
+    }
+
+    int length() { return ptr - start; }
+    void clear() { ptr = start; };
+    void clearAndZero() { memset(start, 0, ptr-start); clear(); }
+    void reposition(int pos) { ptr = start + pos; }
+
+    // data() returns a pointer to the buffer.
+
+    const void* data() { return (const void*)start; }
+
+  private:
+
+    // overrun() either doubles the buffer or adds enough space for nItems of
+    // size itemSize bytes.
+
+    int overrun(int itemSize, int nItems) {
+      int len = ptr - start + itemSize * nItems;
+      if (len < (end - start) * 2)
+        len = (end - start) * 2;
+
+      U8* newStart = new U8[len];
+      memcpy(newStart, start, ptr - start);
+      ptr = newStart + (ptr - start);
+      delete [] start;
+      start = newStart;
+      end = newStart + len;
+
+      return nItems;
+    }
+
+    U8* start;
+  };
+
+}
+
+#endif