diff --git a/libmspack/cab.cs b/libmspack/cab.cs
new file mode 100644
index 0000000..a71792f
--- /dev/null
+++ b/libmspack/cab.cs
@@ -0,0 +1,75 @@
+namespace SabreTools.Compression.libmspack
+{
+    public static class cab
+    {
+        /* structure offsets */
+        public const byte cfhead_Signature = 0x00;
+        public const byte cfhead_CabinetSize = 0x08;
+        public const byte cfhead_FileOffset = 0x10;
+        public const byte cfhead_MinorVersion = 0x18;
+        public const byte cfhead_MajorVersion = 0x19;
+        public const byte cfhead_NumFolders = 0x1A;
+        public const byte cfhead_NumFiles = 0x1C;
+        public const byte cfhead_Flags = 0x1E;
+        public const byte cfhead_SetID = 0x20;
+        public const byte cfhead_CabinetIndex = 0x22;
+        public const byte cfhead_SIZEOF = 0x24;
+        public const byte cfheadext_HeaderReserved = 0x00;
+        public const byte cfheadext_FolderReserved = 0x02;
+        public const byte cfheadext_DataReserved = 0x03;
+        public const byte cfheadext_SIZEOF = 0x04;
+        public const byte cffold_DataOffset = 0x00;
+        public const byte cffold_NumBlocks = 0x04;
+        public const byte cffold_CompType = 0x06;
+        public const byte cffold_SIZEOF = 0x08;
+        public const byte cffile_UncompressedSize = 0x00;
+        public const byte cffile_FolderOffset = 0x04;
+        public const byte cffile_FolderIndex = 0x08;
+        public const byte cffile_Date = 0x0A;
+        public const byte cffile_Time = 0x0C;
+        public const byte cffile_Attribs = 0x0E;
+        public const byte cffile_SIZEOF = 0x10;
+        public const byte cfdata_CheckSum = 0x00;
+        public const byte cfdata_CompressedSize = 0x04;
+        public const byte cfdata_UncompressedSize = 0x06;
+        public const byte cfdata_SIZEOF = 0x08;
+
+        /* flags */
+        public const ushort cffoldCOMPTYPE_MASK = 0x000f;
+        public const ushort cffoldCOMPTYPE_NONE = 0x0000;
+        public const ushort cffoldCOMPTYPE_MSZIP = 0x0001;
+        public const ushort cffoldCOMPTYPE_QUANTUM = 0x0002;
+        public const ushort cffoldCOMPTYPE_LZX = 0x0003;
+        public const ushort cfheadPREV_CABINET = 0x0001;
+        public const ushort cfheadNEXT_CABINET = 0x0002;
+        public const ushort cfheadRESERVE_PRESENT = 0x0004;
+        public const ushort cffileCONTINUED_FROM_PREV = 0xFFFD;
+        public const ushort cffileCONTINUED_TO_NEXT = 0xFFFE;
+        public const ushort cffileCONTINUED_PREV_AND_NEXT = 0xFFFF;
+
+        /* CAB data blocks are <= 32768 bytes in uncompressed form. Uncompressed
+         * blocks have zero growth. MSZIP guarantees that it won't grow above
+         * uncompressed size by more than 12 bytes. LZX guarantees it won't grow
+         * more than 6144 bytes. Quantum has no documentation, but the largest
+         * block seen in the wild is 337 bytes above uncompressed size.
+         */
+        public const int CAB_BLOCKMAX = 32768;
+        public const int CAB_INPUTMAX = CAB_BLOCKMAX + 6144;
+
+        /* input buffer needs to be CAB_INPUTMAX + 1 byte to allow for max-sized block
+         * plus 1 trailer byte added by cabd_sys_read_block() for Quantum alignment.
+         *
+         * When MSCABD_PARAM_SALVAGE is set, block size is not checked so can be
+         * up to 65535 bytes, so max input buffer size needed is 65535 + 1
+         */
+        public const int CAB_INPUTMAX_SALVAGE = 65535;
+        public const int CAB_INPUTBUF = CAB_INPUTMAX_SALVAGE + 1;
+
+        /* There are no more than 65535 data blocks per folder, so a folder cannot
+         * be more than 32768*65535 bytes in length. As files cannot span more than
+         * one folder, this is also their max offset, length and offset+length limit.
+         */
+        public const int CAB_FOLDERMAX = 65535;
+        public const int CAB_LENGTHMAX = CAB_BLOCKMAX * CAB_FOLDERMAX;
+    }
+}
\ No newline at end of file
diff --git a/libmspack/mscab_compressor.cs b/libmspack/mscab_compressor.cs
index 3b58868..f6429a6 100644
--- a/libmspack/mscab_compressor.cs
+++ b/libmspack/mscab_compressor.cs
@@ -6,5 +6,7 @@ namespace SabreTools.Compression.libmspack
     public class mscab_compressor
     {
         public int dummy { get; set; }
+
+        public mspack_system system { get; set; }
     }
 }
\ No newline at end of file
diff --git a/libmspack/mscab_decompressor.cs b/libmspack/mscab_decompressor.cs
index 1e4462a..00d380e 100644
--- a/libmspack/mscab_decompressor.cs
+++ b/libmspack/mscab_decompressor.cs
@@ -9,6 +9,22 @@ namespace SabreTools.Compression.libmspack
     /// <see cref="mspack_destroy_cab_decompressor()"/>
     public abstract class mscab_decompressor
     {
+        public mscabd_decompress_state d { get; set; }
+
+        public mspack_system system { get; set; }
+
+        public int buf_size { get; set; }
+
+        public int searchbuf_size { get; set; }
+
+        public int fix_mszip { get; set; }
+
+        public int salvage { get; set; }
+
+        public MSPACK_ERR error { get; set; }
+
+        public MSPACK_ERR read_error { get; set; }
+
         /// <summary>
         /// Opens a cabinet file and reads its contents.
         /// 
diff --git a/libmspack/mscabd_cabinet.cs b/libmspack/mscabd_cabinet.cs
index 01954dc..5806e92 100644
--- a/libmspack/mscabd_cabinet.cs
+++ b/libmspack/mscabd_cabinet.cs
@@ -111,5 +111,15 @@ namespace SabreTools.Compression.libmspack
         /// <see cref="nextinfo"/> 
         /// <see cref="header_resv"/> 
         public MSCAB_HDR flags { get; set; }
+
+        /// <summary>
+        /// Offset to data blocks
+        /// </summary>
+        public long blocks_off { get; set; }
+
+        /// <summary>
+        /// Reserved space in data blocks
+        /// </summary>
+        public int block_resv { get; set; }
     }
 }
\ No newline at end of file
diff --git a/libmspack/mscabd_decompress_state.cs b/libmspack/mscabd_decompress_state.cs
new file mode 100644
index 0000000..39e27bf
--- /dev/null
+++ b/libmspack/mscabd_decompress_state.cs
@@ -0,0 +1,85 @@
+using static SabreTools.Compression.libmspack.cab;
+
+namespace SabreTools.Compression.libmspack
+{
+    public abstract unsafe class mscabd_decompress_state
+    {
+        /// <summary>
+        /// Current folder we're extracting from
+        /// </summary>
+        public mscabd_folder folder { get; set; }
+
+        /// <summary>
+        /// Current folder split we're in
+        /// </summary>
+        public mscabd_folder_data data { get; set; }
+
+        /// <summary>
+        /// Uncompressed offset within folder
+        /// </summary>
+        public uint offset { get; set; }
+
+        /// <summary>
+        /// Which block are we decompressing?
+        /// </summary>
+        public uint block { get; set; }
+
+        /// <summary>
+        /// Cumulative sum of block output sizes
+        /// </summary>
+        public long outlen { get; set; }
+
+        /// <summary>
+        /// Special I/O code for decompressor
+        /// </summary>
+        public mspack_system sys { get; set; }
+
+        /// <summary>
+        /// Type of compression used by folder
+        /// </summary>
+        public MSCAB_COMP comp_type { get; set; }
+
+        /// <summary>
+        /// Decompressor code
+        /// </summary>
+        /// <param name="data"></param>
+        /// <param name="offset"></param>
+        /// <returns></returns>
+        public abstract int decompress(void* data, long offset);
+
+        /// <summary>
+        /// Decompressor state
+        /// </summary>
+        public void* state { get; set; }
+
+        /// <summary>
+        /// Cabinet where input data comes from
+        /// </summary>
+        public mscabd_cabinet incab { get; set; }
+
+        /// <summary>
+        /// Input file handle
+        /// </summary>
+        public mspack_file infh { get; set; }
+
+        /// <summary>
+        /// Output file handle
+        /// </summary>
+        public mspack_file outfh { get; set; }
+
+        /// <summary>
+        /// Input data consumed
+        /// </summary>
+        public byte* i_ptr { get; set; }
+
+        /// <summary>
+        /// Input data end
+        /// </summary>
+        public byte* i_end { get; set; }
+
+        /// <summary>
+        /// One input block of data
+        /// </summary>
+        public byte[] input { get; set; } = new byte[CAB_INPUTBUF];
+    }
+}
\ No newline at end of file
diff --git a/libmspack/mscabd_folder.cs b/libmspack/mscabd_folder.cs
index 3ee9ac4..33ccdaf 100644
--- a/libmspack/mscabd_folder.cs
+++ b/libmspack/mscabd_folder.cs
@@ -34,5 +34,20 @@ namespace SabreTools.Compression.libmspack
         /// one cabinet.
         /// </summary>
         public uint num_blocks { get; set; }
+
+        /// <summary>
+        /// Where are the data blocks?
+        /// </summary>
+        public mscabd_folder_data data { get; set; }
+
+        /// <summary>
+        /// First file needing backwards merge
+        /// </summary>
+        public mscabd_file merge_prev { get; set; }
+
+        /// <summary>
+        /// First file needing forwards merge
+        /// </summary>
+        public mscabd_file merge_next { get; set; }
     }
 }
\ No newline at end of file
diff --git a/libmspack/mscabd_folder_data.cs b/libmspack/mscabd_folder_data.cs
new file mode 100644
index 0000000..91a2442
--- /dev/null
+++ b/libmspack/mscabd_folder_data.cs
@@ -0,0 +1,20 @@
+namespace SabreTools.Compression.libmspack
+{
+    /// <summary>
+    /// There is one of these for every cabinet a folder spans
+    /// </summary>
+    public class mscabd_folder_data
+    {
+        public mscabd_folder_data next { get; set; }
+
+        /// <summary>
+        /// Cabinet file of this folder span
+        /// </summary>
+        public mscabd_cabinet cab { get; set; }
+
+        /// <summary>
+        /// Cabinet offset of first datablock
+        /// </summary>
+        public long offset { get; set; }
+    }
+}
\ No newline at end of file