diff --git a/libmspack/msoab_compressor.cs b/libmspack/msoab_compressor.cs
index d1ed2bf..bbe93ca 100644
--- a/libmspack/msoab_compressor.cs
+++ b/libmspack/msoab_compressor.cs
@@ -9,6 +9,8 @@ namespace SabreTools.Compression.libmspack
     /// <see cref="mspack_destroy_oab_compressor()"/> 
     public abstract class msoab_compressor
     {
+        public mspack_system system { get; set; }
+
         /// <summary>
         /// Compress a full OAB file.
         ///
diff --git a/libmspack/msoab_decompressor.cs b/libmspack/msoab_decompressor.cs
index 82432c4..a9f2466 100644
--- a/libmspack/msoab_decompressor.cs
+++ b/libmspack/msoab_decompressor.cs
@@ -9,6 +9,10 @@ namespace SabreTools.Compression.libmspack
     /// <see cref="mspack_destroy_oab_decompressor()"/> 
     public abstract class msoab_decompressor
     {
+        public mspack_system system { get; set; }
+
+        public int buf_size { get; set; }
+
         /// <summary>
         /// Decompresses a full Offline Address Book file.
         ///
@@ -56,7 +60,7 @@ namespace SabreTools.Compression.libmspack
         /// </param>
         /// <returns>An error code, or MSPACK_ERR_OK if successful</returns>
         public abstract MSPACK_ERR decompress_incremental(in string input, in string @base, in string output);
-    
+
         /// <summary>
         /// Sets an OAB decompression engine parameter. Available only in OAB
         /// decompressor version 2 and above.
diff --git a/libmspack/oab.cs b/libmspack/oab.cs
new file mode 100644
index 0000000..f868a43
--- /dev/null
+++ b/libmspack/oab.cs
@@ -0,0 +1,32 @@
+namespace SabreTools.Compression.libmspack
+{
+    public static class oab
+    {
+        public const int oabhead_VersionHi = 0x0000;
+        public const int oabhead_VersionLo = 0x0004;
+        public const int oabhead_BlockMax = 0x0008;
+        public const int oabhead_TargetSize = 0x000c;
+        public const int oabhead_SIZEOF = 0x0010;
+
+        public const int oabblk_Flags = 0x0000;
+        public const int oabblk_CompSize = 0x0004;
+        public const int oabblk_UncompSize = 0x0008;
+        public const int oabblk_CRC = 0x000c;
+        public const int oabblk_SIZEOF = 0x0010;
+
+        public const int patchhead_VersionHi = 0x0000;
+        public const int patchhead_VersionLo = 0x0004;
+        public const int patchhead_BlockMax = 0x0008;
+        public const int patchhead_SourceSize = 0x000c;
+        public const int patchhead_TargetSize = 0x0010;
+        public const int patchhead_SourceCRC = 0x0014;
+        public const int patchhead_TargetCRC = 0x0018;
+        public const int patchhead_SIZEOF = 0x001c;
+
+        public const int patchblk_PatchSize = 0x0000;
+        public const int patchblk_TargetSize = 0x0004;
+        public const int patchblk_SourceSize = 0x0008;
+        public const int patchblk_CRC = 0x000c;
+        public const int patchblk_SIZEOF = 0x0010;
+    }
+}
\ No newline at end of file