diff --git a/libmspack/mspack.cs b/libmspack/mspack.cs
index 318a26f..d45839a 100644
--- a/libmspack/mspack.cs
+++ b/libmspack/mspack.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Runtime.Serialization;
 
 namespace SabreTools.Compression.libmspack
 {
@@ -16,7 +17,25 @@ namespace SabreTools.Compression.libmspack
         /// </summary>
         /// <param name="sys">A custom mspack_system structure, or NULL to use the default</param>
         /// <returns>A <see cref="mscab_decompressor"/> or NULL</returns>
-        public static mscab_decompressor mspack_create_cab_decompressor(mspack_system sys) => throw new NotImplementedException();
+        public static mscab_decompressor mspack_create_cab_decompressor(mspack_system sys)
+        {
+            if (sys == null)
+                return null;
+
+            var self = new mscab_decompressor
+            {
+                system = sys,
+                d = null,
+                error = MSPACK_ERR.MSPACK_ERR_OK,
+
+                searchbuf_size = 32768,
+                fix_mszip = 0,
+                buf_size = 4096,
+                salvage = 0,
+            };
+
+            return self;
+        }
 
         /// <summary>
         /// Destroys an existing CAB compressor.
@@ -28,7 +47,21 @@ namespace SabreTools.Compression.libmspack
         /// Destroys an existing CAB decompressor.
         /// </summary>
         /// <param name="self">The <see cref="mscab_decompressor"/> to destroy</param>
-        public static void mspack_destroy_cab_decompressor(mscab_decompressor self) => throw new NotImplementedException();
+        public static void mspack_destroy_cab_decompressor(mscab_decompressor self)
+        {
+            if (self != null)
+            {
+                mspack_system sys = self.system;
+                if (self.d != null)
+                {
+                    if (self.d.infh != null) sys.close(self.d.infh);
+                    cabd_free_decomp(self);
+                    //sys.free(self.d);
+                }
+
+                //sys.free(self);
+            }
+        }
 
         /// <summary>
         /// Creates a new CHM compressor.
@@ -120,7 +153,18 @@ namespace SabreTools.Compression.libmspack
         /// </summary>
         /// <param name="sys">A custom mspack_system structure, or NULL to use the default</param>
         /// <returns>A <see cref="msszdd_decompressor"/> or NULL</returns>
-        public static msszdd_decompressor mspack_create_szdd_decompressor(mspack_system sys) => throw new NotImplementedException();
+        public static msszdd_decompressor mspack_create_szdd_decompressor(mspack_system sys)
+        {
+            msszdd_decompressor self = null;
+
+            if (sys == null) sys = new mspack_default_system();
+
+            self = new msszdd_decompressor();
+            self.system = sys;
+            self.error = MSPACK_ERR.MSPACK_ERR_OK;
+
+            return self;
+        }
 
         /// <summary>
         /// Destroys an existing SZDD compressor.
@@ -132,7 +176,14 @@ namespace SabreTools.Compression.libmspack
         /// Destroys an existing SZDD decompressor.
         /// </summary>
         /// <param name="self">The <see cref="msszdd_decompressor"/> to destroy</param>
-        public static void mspack_destroy_szdd_decompressor(msszdd_decompressor self) => throw new NotImplementedException();
+        public static void mspack_destroy_szdd_decompressor(msszdd_decompressor self)
+        {
+            if (self != null)
+            {
+                mspack_system sys = self.system;
+                //sys.free(self);
+            }
+        }
 
         /// <summary>
         /// Creates a new KWAJ compressor.
diff --git a/libmspack/msszdd_decompressor.cs b/libmspack/msszdd_decompressor.cs
index de22af0..10d377a 100644
--- a/libmspack/msszdd_decompressor.cs
+++ b/libmspack/msszdd_decompressor.cs
@@ -1,3 +1,6 @@
+using System.Linq;
+using static SabreTools.Compression.libmspack.szdd;
+
 namespace SabreTools.Compression.libmspack
 {
     /// <summary>
@@ -7,7 +10,7 @@ namespace SabreTools.Compression.libmspack
     /// </summary>
     /// <see cref="mspack_create_szdd_decompressor()"/>
     /// <see cref="mspack_destroy_szdd_decompressor()"/>
-    public abstract class msszdd_decompressor
+    public unsafe class msszdd_decompressor
     {
         public mspack_system system { get; set; }
 
@@ -19,7 +22,7 @@ namespace SabreTools.Compression.libmspack
         /// If the file opened is a valid SZDD file, all headers will be read and
         /// a msszddd_header structure will be returned.
         ///
-        /// In the case of an error occuring, NULL is returned and the error code
+        /// In the case of an error occuring, null is returned and the error code
         /// is available from last_error().
         ///
         /// The filename pointer should be considered "in use" until close() is
@@ -29,9 +32,26 @@ namespace SabreTools.Compression.libmspack
         /// The filename of the SZDD compressed file. This is
         /// passed directly to mspack_system::open().
         /// </param>
-        /// <returns>A pointer to a msszddd_header structure, or NULL on failure</returns>
+        /// <returns>A pointer to a msszddd_header structure, or null on failure</returns>
         /// <see cref="close(msszddd_header)"/> 
-        public abstract msszddd_header open(in string filename);
+        public msszddd_header open(in string filename)
+        {
+            mspack_system sys = this.system;
+
+            mspack_file fh = sys.open(filename, MSPACK_SYS_OPEN.MSPACK_SYS_OPEN_READ);
+            msszddd_header hdr = new msszddd_header();
+            hdr.fh = fh;
+            this.error = szddd_read_headers(sys, fh, hdr);
+
+            if (this.error != MSPACK_ERR.MSPACK_ERR_OK)
+            {
+                if (fh != null) sys.close(fh);
+                //sys.free(hdr);
+                hdr = null;
+            }
+
+            return hdr;
+        }
 
         /// <summary>
         /// Closes a previously opened SZDD file.
@@ -42,7 +62,69 @@ namespace SabreTools.Compression.libmspack
         /// The SZDD header pointer is now invalid and cannot be used again.
         /// </summary>
         /// <param name="szdd">The SZDD file to close</param>
-        public abstract void close(msszddd_header szdd);
+        public void close(msszddd_header szdd)
+        {
+            if (this.system == null) return;
+
+            // Close the file handle associated
+            this.system.close(szdd.fh);
+
+            // Free the memory associated
+            //this.system.free(hdr);
+
+            this.error = MSPACK_ERR.MSPACK_ERR_OK;
+        }
+
+        private static readonly byte[] szdd_signature_expand = new byte[8]
+        {
+            0x53, 0x5A, 0x44, 0x44, 0x88, 0xF0, 0x27, 0x33
+        };
+
+        private static readonly byte[] szdd_signature_qbasic = new byte[8]
+        {
+            0x53, 0x5A, 0x20, 0x88, 0xF0, 0x27, 0x33, 0xD1
+        };
+
+        /// <summary>
+        /// Reads the headers of an SZDD format file
+        /// </summary>
+        /// <param name="sys"></param>
+        /// <param name="fh"></param>
+        /// <param name="hdr"></param>
+        /// <returns></returns>
+        private static MSPACK_ERR szddd_read_headers(mspack_system sys, mspack_file fh, msszddd_header hdr)
+        {
+            byte[] buf = new byte[8];
+            byte* bufPtr = libmspack.system.GetArrayPointer<byte>(buf);
+
+            // Read and check signature
+            if (sys.read(fh, buffer: bufPtr, 8) != 8) return MSPACK_ERR.MSPACK_ERR_READ;
+
+            if (buf.SequenceEqual(szdd_signature_expand))
+            {
+                // Common SZDD
+                hdr.format = MSSZDD_FMT.MSSZDD_FMT_NORMAL;
+
+                // Read the rest of the header
+                if (sys.read(fh, bufPtr, 6) != 6) return MSPACK_ERR.MSPACK_ERR_READ;
+                if (buf[0] != 0x41) return MSPACK_ERR.MSPACK_ERR_DATAFORMAT;
+                hdr.missing_char = (char)buf[1];
+                hdr.length = EndGetI32(&buf[2]);
+            }
+            else if (buf.SequenceEqual(szdd_signature_qbasic))
+            {
+                // Special QBasic SZDD
+                hdr.format = MSSZDD_FMT.MSSZDD_FMT_QBASIC;
+                if (sys.read(fh, bufPtr, 4) != 4) return MSPACK_ERR.MSPACK_ERR_READ;
+                hdr.missing_char = '\0';
+                hdr.length = EndGetI32(buf);
+            }
+            else
+            {
+                return MSPACK_ERR.MSPACK_ERR_SIGNATURE;
+            }
+            return MSPACK_ERR.MSPACK_ERR_OK;
+        }
 
         /// <summary>
         /// Extracts the compressed data from a SZDD file.
@@ -56,7 +138,38 @@ namespace SabreTools.Compression.libmspack
         /// is passed directly to mspack_system::open().
         /// </param>
         /// <returns>An error code, or MSPACK_ERR_OK if successful</returns>
-        public abstract MSPACK_ERR extract(msszddd_header szdd, in string filename);
+        public MSPACK_ERR extract(msszddd_header szdd, in string filename)
+        {
+            if (szdd == null) return this.error = MSPACK_ERR.MSPACK_ERR_ARGS;
+            mspack_system sys = this.system;
+
+            mspack_file fh = szdd.fh;
+
+            // Seek to the compressed data
+            long data_offset = (szdd.format == MSSZDD_FMT.MSSZDD_FMT_NORMAL) ? 14 : 12;
+            if (sys.seek(fh, data_offset, MSPACK_SYS_SEEK.MSPACK_SYS_SEEK_START) != 0)
+            {
+                return this.error = MSPACK_ERR.MSPACK_ERR_SEEK;
+            }
+
+            // Open file for output
+            mspack_file outfh;
+            if ((outfh = sys.open(filename, MSPACK_SYS_OPEN.MSPACK_SYS_OPEN_WRITE)) == null)
+            {
+                return this.error = MSPACK_ERR.MSPACK_ERR_OPEN;
+            }
+
+            // Decompress the data
+            this.error = lzss_decompress(sys, fh, outfh, SZDD_INPUT_SIZE,
+                                          szdd.format == MSSZDD_FMT.MSSZDD_FMT_NORMAL
+                                          ? LZSS_MODE.LZSS_MODE_EXPAND
+                                          : LZSS_MODE.LZSS_MODE_QBASIC);
+
+            // Close output file
+            sys.close(outfh);
+
+            return this.error;
+        }
 
         /// <summary>
         /// Decompresses an SZDD file to an output file in one step.
@@ -76,7 +189,15 @@ namespace SabreTools.Compression.libmspack
         /// is passed directly to mspack_system::open().
         /// </param>
         /// <returns>An error code, or MSPACK_ERR_OK if successful</returns>
-        public abstract MSPACK_ERR decompress(in string input, in string output);
+        public MSPACK_ERR decompress(in string input, in string output)
+        {
+            msszddd_header hdr;
+
+            if ((hdr = open(input)) == null) return this.error;
+            MSPACK_ERR error = extract(hdr, output);
+            close(hdr);
+            return this.error = error;
+        }
 
         /// <summary>
         /// Returns the error code set by the most recently called method.
@@ -88,6 +209,9 @@ namespace SabreTools.Compression.libmspack
         /// <see cref="open(in string)"/> 
         /// <see cref="extract(msszddd_header, in string)"/> 
         /// <see cref="decompress(in string, in string)"/> 
-        public abstract MSPACK_ERR last_error();
+        public MSPACK_ERR last_error()
+        {
+            return this.error;
+        }
     }
 }
\ No newline at end of file
diff --git a/libmspack/system.cs b/libmspack/system.cs
index a8bbffe..0cb029a 100644
--- a/libmspack/system.cs
+++ b/libmspack/system.cs
@@ -9,12 +9,12 @@
 
 namespace SabreTools.Compression.libmspack
 {
-    public static class system
+    public unsafe static class system
     {
         /// <summary>
         /// Returns the length of a file opened for reading
         /// </summary>
-        public unsafe static MSPACK_ERR mspack_sys_filelen(mspack_system system, mspack_file file, long* length)
+        public static MSPACK_ERR mspack_sys_filelen(mspack_system system, mspack_file file, long* length)
         {
             if (system == null || file == null || length == null) return MSPACK_ERR.MSPACK_ERR_OPEN;
 
@@ -38,5 +38,18 @@ namespace SabreTools.Compression.libmspack
 
             return MSPACK_ERR.MSPACK_ERR_OK;
         }
+
+        public static T* CreateArray<T>(int length)
+        {
+            T[] buf = new T[length];
+            return GetArrayPointer(buf);
+        }
+
+        public static T* GetArrayPointer<T>(T[] arr)
+        {
+            var bufRef = __makeref(arr);
+            var bufPtr = **(System.IntPtr**)&bufRef;
+            return (T*)bufPtr.ToPointer();
+        }
     }
 }
\ No newline at end of file
diff --git a/libmspack/szdd.cs b/libmspack/szdd.cs
index 73f8861..d416f90 100644
--- a/libmspack/szdd.cs
+++ b/libmspack/szdd.cs
@@ -9,7 +9,7 @@
 
 namespace SabreTools.Compression.libmspack
 {
-    public static class SZDD
+    public static class szdd
     {
         /// <summary>
         /// Input buffer size during decompression - not worth parameterising IMHO