diff --git a/libmspack/msszdd_compressor.cs b/libmspack/msszdd_compressor.cs
index 0cf1d97..6ddc6f2 100644
--- a/libmspack/msszdd_compressor.cs
+++ b/libmspack/msszdd_compressor.cs
@@ -9,6 +9,10 @@ namespace SabreTools.Compression.libmspack
     /// <see cref="mspack_destroy_szdd_compressor()"/>
     public abstract class msszdd_compressor
     {
+        public mspack_system system { get; set; }
+
+        public MSPACK_ERR error { get; set; }
+
         /// <summary>
         /// Reads an input file and creates a compressed output file in the
         /// SZDD compressed file format. The SZDD compression format is quick
diff --git a/libmspack/msszdd_decompressor.cs b/libmspack/msszdd_decompressor.cs
index 3f922ee..de22af0 100644
--- a/libmspack/msszdd_decompressor.cs
+++ b/libmspack/msszdd_decompressor.cs
@@ -9,6 +9,10 @@ namespace SabreTools.Compression.libmspack
     /// <see cref="mspack_destroy_szdd_decompressor()"/>
     public abstract class msszdd_decompressor
     {
+        public mspack_system system { get; set; }
+
+        public MSPACK_ERR error { get; set; }
+
         /// <summary>
         /// Opens a SZDD file and reads the header.
         ///
diff --git a/libmspack/msszddd_header.cs b/libmspack/msszddd_header.cs
index 6996845..74cdb1f 100644
--- a/libmspack/msszddd_header.cs
+++ b/libmspack/msszddd_header.cs
@@ -7,6 +7,8 @@ namespace SabreTools.Compression.libmspack
     /// </summary>
     public class msszddd_header
     {
+        public mspack_file fh { get; set; }
+
         /// <summary>
         /// The file format
         /// </summary>
diff --git a/libmspack/szdd.cs b/libmspack/szdd.cs
new file mode 100644
index 0000000..73f8861
--- /dev/null
+++ b/libmspack/szdd.cs
@@ -0,0 +1,19 @@
+/* This file is part of libmspack.
+ * (C) 2003-2004 Stuart Caie.
+ *
+ * libmspack is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License (LGPL) version 2.1
+ *
+ * For further details, see the file COPYING.LIB distributed with libmspack
+ */
+
+namespace SabreTools.Compression.libmspack
+{
+    public static class SZDD
+    {
+        /// <summary>
+        /// Input buffer size during decompression - not worth parameterising IMHO
+        /// </summary>
+        public const int SZDD_INPUT_SIZE = 2048;
+    }
+}
\ No newline at end of file