implemented CPZ7 archives.

ArcFormats/ArcFormats.csproj

@@ -104,6 +104,8 @@
     <Compile Include="BlackRainbow\ArcSPPAK.cs" />
     <Compile Include="Cadath\ArcDAF.cs" />
     <Compile Include="Cadath\ImageCGF.cs" />
+    <Compile Include="Cmvs\CpzHeader.cs" />
+    <Compile Include="Cmvs\HuffmanDecoder.cs" />
     <Compile Include="Crowd\ImageCRZ.cs" />
     <Compile Include="CsWare\ImageBPC.cs" />
     <Compile Include="Cyberworks\ArcApp.cs" />

ArcFormats/Cmvs/ArcCPZ.cs

@@ -2,7 +2,7 @@
 //! \date       Tue Nov 24 11:27:23 2015
 //! \brief      Purple Software resource archive.
 //
-// Copyright (C) 2015-2016 by morkt
+// Copyright (C) 2015-2017 by morkt
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to
@@ -29,7 +29,6 @@ using System.ComponentModel.Composition;
 using System.IO;
 using System.Linq;
 using GameRes.Utility;
-using System.Security.Cryptography;
 
 namespace GameRes.Formats.Purple
 {
@@ -41,6 +40,7 @@ namespace GameRes.Formats.Purple
         public Cmvs.Md5Variant  Md5Variant;
         public uint             DecoderFactor;
         public uint             EntryInitKey;
+        public uint             EntrySubKey = 0x5C29E87B;
         public byte             EntryTailKey;
         public byte             EntryKeyPos = 9;
         public uint             IndexSeed = 0x2A65CB4E;
@@ -57,17 +57,6 @@ namespace GameRes.Formats.Purple
         public uint Key;
     }
 
-    internal class CpzHeader
-    {
-        public int      DirCount;
-        public int      DirEntriesSize;
-        public int      FileEntriesSize;
-        public uint[]   CmvsMd5 = new uint[4];
-        public uint     MasterKey;
-        public bool     IsEncrypted;
-        public uint     EntryKey;
-    }
-
     internal class CpzArchive : ArcFile
     {
         public CpzHeader    Header;
@@ -98,7 +87,7 @@ namespace GameRes.Formats.Purple
 
         public CpzOpener ()
         {
-            Signatures = new uint[] { 0x355A5043, 0x365A5043 };
+            Signatures = new uint[] { 0x355A5043, 0x365A5043, 0x375A5043 };
         }
 
         public static Dictionary<string, CmvsScheme> KnownSchemes = new Dictionary<string, CmvsScheme>();
@@ -113,75 +102,40 @@ namespace GameRes.Formats.Purple
         {
             if (null == KnownSchemes)
                 throw new OperationCanceledException ("Outdated encryption schemes database");
-            var header = file.View.ReadBytes (0, 0x3C);
+
-            var checksum = file.View.ReadUInt32 (0x3C);
+            var cpz = CpzHeader.Parse (file);
-            if (checksum != CheckSum (header, 0, 0x3C, 0x923A564Cu))
+            if (null == cpz)
-                return null;
-            int version = header[3] - '0';
-            CpzHeader cpz = 5 == version ? ReadHeaderV5 (header) : ReadHeaderV6 (header);
-            int index_size = cpz.DirEntriesSize + cpz.FileEntriesSize;
-            var index = file.View.ReadBytes (0x40, (uint)index_size);
-            if (index.Length != index_size)
                 return null;
 
-            using (var md5 = MD5.Create())
+            var index = file.View.ReadBytes (cpz.IndexOffset, cpz.IndexSize);
-            {
+            if (!cpz.VerifyIndex (index))
-                var hash = md5.ComputeHash (index);
-                if (!header.Skip (0x10).Take (0x10).SequenceEqual (hash))
                 return null;
+
+            int file_table_size = cpz.DirEntriesSize + cpz.FileEntriesSize;
+            if (cpz.IndexKeySize > 24)
+            {
+                var index_key = UnpackIndexKey (index, file_table_size, cpz.IndexKeySize);
+                for (int i = 0; i < file_table_size; ++i)
+                {
+                    index[i] ^= index_key[(i + 3) % 0x3FF];
                 }
+            }
+
+            var index_copy = new CowArray<byte> (index, 0, file_table_size).ToArray();
             var cmvs_md5 = cpz.CmvsMd5.Clone() as uint[];
-            foreach (var scheme in KnownSchemes.Values.Where (s => s.Version == version))
+            foreach (var scheme in KnownSchemes.Values.Where (s => s.Version == cpz.Version))
             {
                 var arc = ReadIndex (file, scheme, cpz, index);
                 if (null != arc)
                     return arc;
                 // both CmvsMd5 and index was altered by ReadIndex in decryption attempt
                 Array.Copy (cmvs_md5, cpz.CmvsMd5, 4);
-                file.View.Read (0x40, index, 0, (uint)index_size);
+                Array.Copy (index, index_copy, file_table_size);
             }
             throw new UnknownEncryptionScheme();
         }
 
-        CpzHeader ReadHeaderV5 (byte[] header)
+        internal ArcFile ReadIndex (ArcView file, CmvsScheme scheme, CpzHeader cpz, byte[] index)
-        {
-            uint entry_key = 0x37ACF831 ^ LittleEndian.ToUInt32 (header, 0x38);
-            var cpz = new CpzHeader
-            {
-                DirCount        = -0x1C5AC27 ^ LittleEndian.ToInt32 (header, 4),
-                DirEntriesSize  = 0x37F298E7 ^ LittleEndian.ToInt32 (header, 8),
-                FileEntriesSize = 0x7A6F3A2C ^ LittleEndian.ToInt32 (header, 0x0C),
-                MasterKey       = 0xAE7D39BF ^ LittleEndian.ToUInt32 (header, 0x30),
-                IsEncrypted     = 0 != (0xFB73A955 ^ LittleEndian.ToUInt32 (header, 0x34)),
-                EntryKey        = 0,
-            };
-            cpz.CmvsMd5[0] = 0x43DE7C19 ^ LittleEndian.ToUInt32 (header, 0x20);
-            cpz.CmvsMd5[1] = 0xCC65F415 ^ LittleEndian.ToUInt32 (header, 0x24);
-            cpz.CmvsMd5[2] = 0xD016A93C ^ LittleEndian.ToUInt32 (header, 0x28);
-            cpz.CmvsMd5[3] = 0x97A3BA9A ^ LittleEndian.ToUInt32 (header, 0x2C);
-            return cpz;
-        }
-
-        CpzHeader ReadHeaderV6 (byte[] header)
-        {
-            uint entry_key = 0x37ACF832 ^ LittleEndian.ToUInt32 (header, 0x38);
-            var cpz = new CpzHeader
-            {
-                DirCount        = -0x1C5AC26 ^ LittleEndian.ToInt32 (header, 4),
-                DirEntriesSize  = 0x37F298E8 ^ LittleEndian.ToInt32 (header, 8),
-                FileEntriesSize = 0x7A6F3A2D ^ LittleEndian.ToInt32 (header, 0x0C),
-                MasterKey       = 0xAE7D39B7 ^ LittleEndian.ToUInt32 (header, 0x30),
-                IsEncrypted     = 0 != (0xFB73A956 ^ LittleEndian.ToUInt32 (header, 0x34)),
-                EntryKey        = 0x7DA8F173 * Binary.RotR (entry_key, 5) + 0x13712765,
-            };
-            cpz.CmvsMd5[0] = 0x43DE7C1A ^ LittleEndian.ToUInt32 (header, 0x20);
-            cpz.CmvsMd5[1] = 0xCC65F416 ^ LittleEndian.ToUInt32 (header, 0x24);
-            cpz.CmvsMd5[2] = 0xD016A93D ^ LittleEndian.ToUInt32 (header, 0x28);
-            cpz.CmvsMd5[3] = 0x97A3BA9B ^ LittleEndian.ToUInt32 (header, 0x2C);
-            return cpz;
-        }
-
-        ArcFile ReadIndex (ArcView file, CmvsScheme scheme, CpzHeader cpz, byte[] index)
         {
             var cmvs_md5 = Cmvs.MD5.Create (scheme.Md5Variant);
             cmvs_md5.Compute (cpz.CmvsMd5);
@@ -200,7 +154,7 @@ namespace GameRes.Formats.Purple
             DecryptIndexDirectory (index, cpz.DirEntriesSize, key);
 
             decoder.Init (cpz.MasterKey, cpz.CmvsMd5[2]);
-            int base_offset = 0x40 + index.Length;
+            uint base_offset = cpz.IndexOffset + cpz.IndexSize;
             int dir_offset = 0;
             var dir = new List<Entry>();
             for (int i = 0; i < cpz.DirCount; ++i)
@@ -239,16 +193,20 @@ namespace GameRes.Formats.Purple
                 for (int j = 0; j < file_count; ++j)
                 {
                     int entry_size = LittleEndian.ToInt32 (index, cur_offset);
-                    if (entry_size > index.Length || entry_size <= 0x18)
+                    if (entry_size > index.Length || entry_size <= cpz.EntryNameOffset)
                         return null;
-                    var name = Binary.GetCString (index, cur_offset+0x18, cur_entries_end-(cur_offset+0x18));
+                    int name_offset = cur_offset + cpz.EntryNameOffset;
+                    var name = Binary.GetCString (index, name_offset, cur_entries_end - name_offset);
                     if (!is_root_dir)
                         name = Path.Combine (dir_name, name);
                     var entry = FormatCatalog.Instance.Create<CpzEntry> (name);
                     entry.Offset    = LittleEndian.ToInt64 (index, cur_offset+4) + base_offset;
                     entry.Size      = LittleEndian.ToUInt32 (index, cur_offset+0xC);
-                    entry.CheckSum  = LittleEndian.ToUInt32 (index, cur_offset+0x10);
+                    int key_offset = cur_offset + 0x10;
-                    entry.Key       = LittleEndian.ToUInt32 (index, cur_offset+0x14) + dir_key;
+                    if (cpz.IsLongSize)
+                        key_offset += 4;
+                    entry.CheckSum  = LittleEndian.ToUInt32 (index, key_offset);
+                    entry.Key       = LittleEndian.ToUInt32 (index, key_offset+4) + dir_key;
                     if (!entry.CheckPlacement (file.MaxOffset))
                         return null;
                     dir.Add (entry);
@@ -271,7 +229,8 @@ namespace GameRes.Formats.Purple
             var data = carc.File.View.ReadBytes (entry.Offset, entry.Size);
             if (carc.Header.IsEncrypted)
             {
-                uint key = (carc.Header.MasterKey ^ cent.Key) + (uint)carc.Header.DirCount - 0x5C29E87B;
+                uint key = (carc.Header.MasterKey ^ cent.Key) + (uint)carc.Header.DirCount;
+                key -= carc.Decoder.Scheme.EntrySubKey;
                 key ^= carc.Header.EntryKey;
                 carc.Decoder.DecryptEntry (data, carc.Header.CmvsMd5, key);
             }
@@ -282,6 +241,21 @@ namespace GameRes.Formats.Purple
             return new BinMemoryStream (data, entry.Name);
         }
 
+        internal byte[] UnpackIndexKey (byte[] data, int offset, int length)
+        {
+            int key_offset = offset + 20;
+            int packed_offset = offset + 24;
+            int packed_length = length - 24;
+            for (int i = 0; i < packed_length; ++i)
+            {
+                data[packed_offset + i] ^= data[key_offset + (i & 3)];
+            }
+            int unpacked_length = data.ToInt32 (offset + 16);
+            var output = new byte[unpacked_length];
+            var decoder = new HuffmanDecoder (data, packed_offset, packed_length, output);
+            return decoder.Unpack();
+        }
+
         void DecryptIndexStage1 (byte[] data, uint key, CmvsScheme scheme)
         {
             var secret = scheme.Cpz5Secret;
@@ -367,33 +341,6 @@ namespace GameRes.Formats.Purple
             }
         }
 
-        public static uint CheckSum (byte[] data, int index, int length, uint crc)
-        {
-            if (null == data)
-                throw new ArgumentNullException ("data");
-            if (index < 0 || index > data.Length)
-                throw new ArgumentOutOfRangeException ("index");
-            if (length < 0 || length > data.Length || length > data.Length-index)
-                throw new ArgumentException ("length");
-            int dwords = length / 4;
-            if (dwords > 0)
-            {
-                unsafe
-                {
-                    fixed (byte* raw = &data[index])
-                    {
-                        uint* raw32 = (uint*)raw;
-                        for (int i = 0; i < dwords; ++i)
-                            crc += raw32[i];
-                    }
-                }
-                index += length & -4;
-            }
-            for (int i = 0; i < (length & 3); ++i)
-                crc += data[index+i];
-            return crc;
-        }
-
         byte[] UnpackPs2 (byte[] data)
         {
             DecryptPs2 (data);
@@ -471,6 +418,8 @@ namespace GameRes.Formats.Purple
         protected byte[]        m_decode_table = new byte[0x100];
         protected CmvsScheme    m_scheme;
 
+        public CmvsScheme Scheme { get { return m_scheme; } }
+
         public Cpz5Decoder (CmvsScheme scheme, uint key, uint summand)
         {
             m_scheme = scheme;

ArcFormats/Cmvs/CmvsMD5.cs

@@ -27,7 +27,7 @@ using GameRes.Utility;
 
 namespace GameRes.Formats.Cmvs
 {
-    public enum Md5Variant { A, B, Chrono, Memoria, Natsu }
+    public enum Md5Variant { A, B, Chrono, Memoria, Natsu, Aoi }
 
     public abstract class MD5 : Cryptography.MD5Base
     {
@@ -45,6 +45,7 @@ namespace GameRes.Formats.Cmvs
             case Md5Variant.Chrono: return new Md5Chrono();
             case Md5Variant.Memoria: return new Md5Memoria();
             case Md5Variant.Natsu: return new Md5Natsu();
+            case Md5Variant.Aoi: return new Md5Aoi();
             default: throw new System.ArgumentException ("Unknown MD5 variant", "variant");
             }
         }
@@ -151,4 +152,23 @@ namespace GameRes.Formats.Cmvs
             data[3] = m_state[0] ^ 0xE3F9A742;
         }
     }
+
+    public class Md5Aoi : MD5
+    {
+        protected override void InitState ()
+        {
+            m_state[0] = 0xC74A2B02;
+            m_state[1] = 0xE7C8AB8F;
+            m_state[2] = 0x38BEBC4E;
+            m_state[3] = 0x7531A4C3;
+        }
+
+        protected override void SetResult (uint[] data)
+        {
+            data[0] = m_state[2] ^ 0x53A76D2E;
+            data[1] = m_state[1] + 0x5BB17FDA;
+            data[2] = m_state[0] + 0x6853E14D;
+            data[3] = m_state[3] ^ 0xF5C6A9A3;
+        }
+    }
 }

ArcFormats/Cmvs/CpzHeader.cs

@@ -0,0 +1,175 @@
+//! \file       CpzHeader.cs
+//! \date       2017 Nov 27
+//! \brief      CPZ archives header class.
+//
+// Copyright (C) 2017 by morkt
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Security.Cryptography;
+using GameRes.Utility;
+
+namespace GameRes.Formats.Purple
+{
+    internal class CpzHeader
+    {
+        public int      Version;
+        public int      DirCount;
+        public int      DirEntriesSize;
+        public int      FileEntriesSize;
+        public uint[]   CmvsMd5 = new uint[4];
+        public uint     MasterKey;
+        public bool     IsEncrypted;
+        public uint     EntryKey;
+        public int      IndexKeySize;
+        public uint     Checksum;
+
+        public uint     InitChecksum = 0x923A564Cu;
+        public uint     IndexOffset;
+        public uint     IndexSize;
+        public IEnumerable<byte> IndexMd5;
+        public int      EntryNameOffset;
+
+        public bool IsLongSize { get { return Version > 6; } }
+
+        public static CpzHeader Parse (ArcView file)
+        {
+            var cpz = new CpzHeader { Version = file.View.ReadByte (3) - '0' };
+            int checksum_length;
+            byte[] header;
+            if (cpz.Version < 7)
+            {
+                header = file.View.ReadBytes (0, 0x40);
+                if (cpz.Version < 6)
+                    cpz.ParseV5 (header);
+                else
+                    cpz.ParseV6 (header);
+                cpz.IndexOffset = 0x40;
+                cpz.IndexSize = (uint)(cpz.DirEntriesSize + cpz.FileEntriesSize);
+                cpz.Checksum = header.ToUInt32 (0x3C);
+                checksum_length = 0x3C;
+            }
+            else
+            {
+                header = file.View.ReadBytes (0, 0x48);
+                cpz.ParseV7 (header);
+                cpz.IndexOffset = 0x48;
+                cpz.IndexSize = (uint)(cpz.DirEntriesSize + cpz.FileEntriesSize + cpz.IndexKeySize);
+                cpz.Checksum = header.ToUInt32 (0x44);
+                checksum_length = 0x40;
+            }
+            if (cpz.Checksum != CheckSum (header, 0, checksum_length, cpz.InitChecksum))
+                return null;
+
+            cpz.IndexMd5 = header.Skip (0x10).Take (0x10).ToArray();
+            return cpz;
+        }
+
+        private void ParseV5 (byte[] header)
+        {
+            DirCount        = -0x1C5AC27 ^ LittleEndian.ToInt32 (header, 4);
+            DirEntriesSize  = 0x37F298E7 ^ LittleEndian.ToInt32 (header, 8);
+            FileEntriesSize = 0x7A6F3A2C ^ LittleEndian.ToInt32 (header, 0x0C);
+            MasterKey       = 0xAE7D39BF ^ LittleEndian.ToUInt32 (header, 0x30);
+            IsEncrypted     = 0 != (0xFB73A955 ^ LittleEndian.ToUInt32 (header, 0x34));
+            EntryKey        = 0;
+            EntryNameOffset = 0x18;
+            CmvsMd5[0] = 0x43DE7C19 ^ LittleEndian.ToUInt32 (header, 0x20);
+            CmvsMd5[1] = 0xCC65F415 ^ LittleEndian.ToUInt32 (header, 0x24);
+            CmvsMd5[2] = 0xD016A93C ^ LittleEndian.ToUInt32 (header, 0x28);
+            CmvsMd5[3] = 0x97A3BA9A ^ LittleEndian.ToUInt32 (header, 0x2C);
+        }
+
+        private void ParseV6 (byte[] header)
+        {
+            uint entry_key  = 0x37ACF832 ^ LittleEndian.ToUInt32 (header, 0x38);
+            DirCount        = -0x1C5AC26 ^ LittleEndian.ToInt32 (header, 4);
+            DirEntriesSize  = 0x37F298E8 ^ LittleEndian.ToInt32 (header, 8);
+            FileEntriesSize = 0x7A6F3A2D ^ LittleEndian.ToInt32 (header, 0x0C);
+            MasterKey       = 0xAE7D39B7 ^ LittleEndian.ToUInt32 (header, 0x30);
+            IsEncrypted     = 0 != (0xFB73A956 ^ LittleEndian.ToUInt32 (header, 0x34));
+            EntryKey        = 0x7DA8F173 * Binary.RotR (entry_key, 5) + 0x13712765;
+            EntryNameOffset = 0x18;
+            CmvsMd5[0] = 0x43DE7C1A ^ LittleEndian.ToUInt32 (header, 0x20);
+            CmvsMd5[1] = 0xCC65F416 ^ LittleEndian.ToUInt32 (header, 0x24);
+            CmvsMd5[2] = 0xD016A93D ^ LittleEndian.ToUInt32 (header, 0x28);
+            CmvsMd5[3] = 0x97A3BA9B ^ LittleEndian.ToUInt32 (header, 0x2C);
+        }
+
+        private void ParseV7 (byte[] header)
+        {
+            ParseV6 (header);
+            var index_key_size = LittleEndian.ToInt32 (header, 0x40);
+            IndexKeySize = 0x65EF99F3 ^ index_key_size;
+            InitChecksum = (uint)index_key_size - 0x6DC5A9B4u;
+            EntryNameOffset = 0x1C;
+        }
+
+        public bool VerifyIndex (byte[] index)
+        {
+            if (index.Length != (int)IndexSize)
+                return false;
+            using (var md5 = MD5.Create())
+            {
+                var hash = md5.ComputeHash (index);
+                if (!hash.SequenceEqual (IndexMd5))
+                    return false;
+                if (Version > 6 && IndexKeySize > 0x10)
+                {
+                    int index_size = DirEntriesSize + FileEntriesSize;
+                    hash = md5.ComputeHash (index, index_size+0x10, IndexKeySize-0x10);
+                    if (!hash.SequenceEqual (index.Skip (index_size).Take (0x10)))
+                        return false;
+                }
+                return true;
+            }
+        }
+
+        public static uint CheckSum (byte[] data, int index, int length, uint crc)
+        {
+            if (null == data)
+                throw new ArgumentNullException ("data");
+            if (index < 0 || index > data.Length)
+                throw new ArgumentOutOfRangeException ("index");
+            if (length < 0 || length > data.Length || length > data.Length-index)
+                throw new ArgumentException ("length");
+            int dwords = length / 4;
+            if (dwords > 0)
+            {
+                unsafe
+                {
+                    fixed (byte* raw = &data[index])
+                    {
+                        uint* raw32 = (uint*)raw;
+                        for (int i = 0; i < dwords; ++i)
+                            crc += raw32[i];
+                    }
+                }
+                index += length & -4;
+            }
+            for (int i = 0; i < (length & 3); ++i)
+                crc += data[index+i];
+            return crc;
+        }
+    }
+}

ArcFormats/Cmvs/HuffmanDecoder.cs

@@ -0,0 +1,108 @@
+//! \file       HuffmanDecoder.cs
+//! \date       2017 Nov 27
+//! \brief      Custom Huffman decoder for CPZ archives.
+//
+// Copyright (C) 2017 by morkt
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//
+
+using System.IO;
+using GameRes.Utility;
+
+namespace GameRes.Formats.Purple
+{
+    internal sealed class HuffmanDecoder
+    {
+        byte[]          m_input;
+        byte[]          m_output;
+
+        int             m_src;
+        int             m_bits;
+        int             m_bit_count;
+
+        ushort[] lhs = new ushort[512];
+        ushort[] rhs = new ushort[512];
+        ushort token = 256;
+
+        public HuffmanDecoder (byte[] src, int index, int length, byte[] dst)
+        {
+            m_input = src;
+            m_output = dst;
+
+            m_src = index;
+            m_bit_count = 0;
+        }
+
+        public byte[] Unpack ()
+        {
+            int dst = 0;
+            token = 256;
+            ushort root = CreateTree();
+            while (dst < m_output.Length)
+            {
+                ushort symbol = root;
+                while (symbol >= 0x100)
+                {
+                    if (0 != GetBits (1))
+                        symbol = rhs[symbol];
+                    else
+                        symbol = lhs[symbol];
+                }
+                m_output[dst++] = (byte)symbol;
+            }
+            return m_output;
+        }
+
+        ushort CreateTree()
+        {
+            if (0 != GetBits (1))
+            {
+                ushort v = token++;
+                if (v >= 511)
+                    throw new InvalidDataException ("Invalid compressed data");
+                lhs[v] =  CreateTree();
+                rhs[v] =  CreateTree();
+                return v;
+            }
+            else
+            {
+                return (ushort)GetBits (8);
+            }
+        }
+
+        int GetBits (int count)
+        {
+            int bits = 0;
+            while (count --> 0)
+            {
+                if (0 == m_bit_count)
+                {
+                    m_bits = LittleEndian.ToInt32 (m_input, m_src);
+                    m_src += 4;
+                    m_bit_count = 32;
+                }
+                bits = bits << 1 | (m_bits & 1);
+                m_bits >>= 1;
+                --m_bit_count;
+            }
+            return bits;
+        }
+    }
+}