diff --git a/libmspack/qtm.cs b/libmspack/qtm.cs
new file mode 100644
index 0000000..df1c3a2
--- /dev/null
+++ b/libmspack/qtm.cs
@@ -0,0 +1,60 @@
+namespace SabreTools.Compression.libmspack
+{
+    public static class qtm
+    {
+        public const int QTM_FRAME_SIZE = 32768;
+
+        /// <summary>
+        /// Allocates Quantum decompression state for decoding the given stream.
+        ///
+        /// - returns NULL if window_bits is outwith the range 10 to 21 (inclusive).
+        ///
+        /// - uses system->alloc() to allocate memory
+        ///
+        /// - returns NULL if not enough memory
+        ///
+        /// - window_bits is the size of the Quantum window, from 1Kb (10) to 2Mb (21).
+        ///
+        /// - input_buffer_size is the number of bytes to use to store bitstream data.
+        /// </summary>
+        /// <param name="system"></param>
+        /// <param name="input"></param>
+        /// <param name="output"></param>
+        /// <param name="window_bits"></param>
+        /// <param name="input_buffer_size"></param>
+        /// <returns></returns>
+        public static qtmd_stream qtmd_init(mspack_system system, mspack_file input, mspack_file output, int window_bits, int input_buffer_size) => null;
+    
+        /// <summary>
+        /// Decompresses, or decompresses more of, a Quantum stream.
+        ///
+        /// - out_bytes of data will be decompressed and the function will return
+        ///   with an MSPACK_ERR_OK return code.
+        ///
+        /// - decompressing will stop as soon as out_bytes is reached. if the true
+        ///   amount of bytes decoded spills over that amount, they will be kept for
+        ///   a later invocation of qtmd_decompress().
+        ///
+        /// - the output bytes will be passed to the system->write() function given in
+        ///   qtmd_init(), using the output file handle given in qtmd_init(). More
+        ///   than one call may be made to system->write()
+        ///
+        /// - Quantum will read input bytes as necessary using the system->read()
+        ///   function given in qtmd_init(), using the input file handle given in
+        ///   qtmd_init(). This will continue until system->read() returns 0 bytes,
+        ///   or an error.
+        /// </summary>
+        /// <param name="qtm"></param>
+        /// <param name="out_bytes"></param>
+        /// <returns></returns>
+        public static MSPACK_ERR qtmd_decompress(qtmd_stream qtm, long out_bytes) => MSPACK_ERR.MSPACK_ERR_OK;
+
+        /// <summary>
+        /// Frees all state associated with a Quantum data stream
+        ///
+        /// - calls system->free() using the system pointer given in qtmd_init()
+        /// </summary>
+        /// <param name="qtm"></param>
+        public static void qtmd_free(qtmd_stream qtm) { }
+    }
+}
\ No newline at end of file
diff --git a/libmspack/qtmd_model.cs b/libmspack/qtmd_model.cs
new file mode 100644
index 0000000..e331261
--- /dev/null
+++ b/libmspack/qtmd_model.cs
@@ -0,0 +1,11 @@
+namespace SabreTools.Compression.libmspack
+{
+    public unsafe class qtmd_model
+    {
+        public int shiftsleft { get; set; }
+
+        public int entries { get; set; }
+
+        public qtmd_modelsym** syms { get; set; }
+    }
+}
\ No newline at end of file
diff --git a/libmspack/qtmd_modelsym.cs b/libmspack/qtmd_modelsym.cs
new file mode 100644
index 0000000..149c610
--- /dev/null
+++ b/libmspack/qtmd_modelsym.cs
@@ -0,0 +1,9 @@
+namespace SabreTools.Compression.libmspack
+{
+    public class qtmd_modelsym
+    {
+        public ushort sym { get; set; }
+
+        public ushort cumfreq { get; set; }
+    }
+}
\ No newline at end of file
diff --git a/libmspack/qtmd_stream.cs b/libmspack/qtmd_stream.cs
new file mode 100644
index 0000000..0c063f3
--- /dev/null
+++ b/libmspack/qtmd_stream.cs
@@ -0,0 +1,160 @@
+namespace SabreTools.Compression.libmspack
+{
+    public unsafe class qtmd_stream
+    {
+        /// <summary>
+        /// I/O routines
+        /// </summary>
+        public mspack_system sys { get; set; }
+
+        /// <summary>
+        /// Input file handle
+        /// </summary>
+        public mspack_file input { get; set; }
+
+        /// <summary>
+        /// Output file handle
+        /// </summary>
+        public mspack_file output { get; set; }
+
+        /// <summary>
+        /// Decoding window
+        /// </summary>
+        public byte* window { get; set; }
+
+        /// <summary>
+        /// Window size
+        /// </summary>
+        public uint window_size { get; set; }
+
+        /// <summary>
+        /// Decompression offset within window
+        /// </summary>
+        public uint window_posn { get; set; }
+
+        /// <summary>
+        /// Bytes remaining for current frame
+        /// </summary>
+        public uint frame_todo { get; set; }
+
+        /// <summary>
+        /// High arith coding state
+        /// </summary>
+        public ushort H { get; set; }
+
+        /// <summary>
+        /// Low arith coding state
+        /// </summary>
+        public ushort L { get; set; }
+
+        /// <summary>
+        /// Current arith coding state
+        /// </summary>
+        public ushort C { get; set; }
+
+        /// <summary>
+        /// Have we started decoding a new frame?
+        /// </summary>
+        public byte header_read { get; set; }
+
+        public MSPACK_ERR error { get; set; }
+
+        #region I/O buffering
+
+        public byte* inbuf { get; set; }
+
+        public byte* i_ptr { get; set; }
+
+        public byte* i_end { get; set; }
+
+        public byte* o_ptr { get; set; }
+
+        public byte* o_end { get; set; }
+
+        public uint bit_buffer { get; set; }
+
+        public uint inbuf_size { get; set; }
+
+        public byte bits_left { get; set; }
+
+        public byte input_end { get; set; }
+
+        #endregion
+
+        #region Models
+
+        #region Four literal models, each representing 64 symbols
+
+        /// <summary>
+        /// model0 for literals from   0 to  63 (selector = 0)
+        /// </summary>
+        public qtmd_model model0 { get; set; }
+
+        /// <summary>
+        /// model1 for literals from  64 to 127 (selector = 1)
+        /// </summary>
+        public qtmd_model model1 { get; set; }
+
+        /// <summary>
+        /// model2 for literals from 128 to 191 (selector = 2)
+        /// </summary>
+        public qtmd_model model2 { get; set; }
+
+        /// <summary>
+        /// model3 for literals from 129 to 255 (selector = 3)
+        /// </summary>
+        public qtmd_model model3 { get; set; }
+
+        #endregion
+
+        #region Three match models
+
+        /// <summary>
+        /// model4 for match with fixed length of 3 bytes
+        /// </summary>
+        public qtmd_model model4 { get; set; }
+
+        /// <summary>
+        /// model5 for match with fixed length of 4 bytes
+        /// </summary>
+        public qtmd_model model5 { get; set; }
+
+        /// <summary>
+        /// model6 for variable length match, encoded with model6len model
+        /// </summary>
+        public qtmd_model model6 { get; set; }
+
+        public qtmd_model model6len { get; set; }
+
+        #endregion
+
+        /// <summary>
+        /// selector model. 0-6 to say literal (0,1,2,3) or match (4,5,6)
+        /// </summary>
+        public qtmd_model model7 { get; set; }
+
+        #endregion
+
+        #region Symbol arrays for all models
+
+        public qtmd_modelsym[] m0sym { get; set; } = new qtmd_modelsym[64 + 1];
+
+        public qtmd_modelsym[] m1sym { get; set; } = new qtmd_modelsym[64 + 1];
+
+        public qtmd_modelsym[] m2sym { get; set; } = new qtmd_modelsym[64 + 1];
+
+        public qtmd_modelsym[] m3sym { get; set; } = new qtmd_modelsym[64 + 1];
+
+        public qtmd_modelsym[] m4sym { get; set; } = new qtmd_modelsym[24 + 1];
+
+        public qtmd_modelsym[] m5sym { get; set; } = new qtmd_modelsym[36 + 1];
+
+        public qtmd_modelsym[] m6sym { get; set; } = new qtmd_modelsym[42 + 1];
+
+        public qtmd_modelsym[] m6lsym { get; set; } = new qtmd_modelsym[27 + 1];
+
+        public qtmd_modelsym[] m7sym { get; set; } = new qtmd_modelsym[7 + 1];
+
+        #endregion
+    }
+}
\ No newline at end of file