diff --git a/ArcFormats/ArcFormats.csproj b/ArcFormats/ArcFormats.csproj
index 67e6df49..1350f3ee 100644
--- a/ArcFormats/ArcFormats.csproj
+++ b/ArcFormats/ArcFormats.csproj
@@ -117,6 +117,7 @@
+
diff --git a/ArcFormats/Littlewitch/ArcDAT.cs b/ArcFormats/Littlewitch/ArcDAT.cs
new file mode 100644
index 00000000..707c6ad7
--- /dev/null
+++ b/ArcFormats/Littlewitch/ArcDAT.cs
@@ -0,0 +1,254 @@
+//! \file ArcDAT.cs
+//! \date 2017 Oct 27
+//! \brief RepiPack resource archive.
+//
+// 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.ComponentModel.Composition;
+using System.IO;
+using System.Linq;
+using System.Text;
+using GameRes.Compression;
+using GameRes.Cryptography;
+using GameRes.Utility;
+
+namespace GameRes.Formats.Littlewitch
+{
+ [Serializable]
+ public class RepiScheme : ResourceScheme
+ {
+ public IDictionary KnownSchemes;
+ }
+
+ internal class RepiEntry : PackedEntry
+ {
+ public bool HasEncryptionKey;
+
+ public byte[] CreateKey ()
+ {
+ var name_bytes = Encodings.cp932.GetBytes (Name.ToLowerInvariant());
+ int name_length = name_bytes.Length;
+ var md5 = new MD5();
+ Array.Reverse (name_bytes);
+ var key = new byte[1024];
+ int key_pos = 0;
+ md5.Initialize();
+ for (int i = 0; i < 64; ++i)
+ {
+ int name_pos = i % name_length;
+ md5.Update (name_bytes, name_pos, name_length - name_pos);
+ md5.Final();
+ Buffer.BlockCopy (md5.State, 0, key, key_pos, 16);
+ key_pos += 16;
+ }
+ return key;
+ }
+ }
+
+ [Export(typeof(ArchiveFormat))]
+ public class DatOpener : ArchiveFormat
+ {
+ public override string Tag { get { return "DAT/RepiPack"; } }
+ public override string Description { get { return "Littlewitch engine resource archive"; } }
+ public override uint Signature { get { return 0x69706552; } } // 'Repi'
+ public override bool IsHierarchic { get { return false; } }
+ public override bool CanWrite { get { return false; } }
+
+ static readonly string ListFileName = "littlewitch.lst";
+
+ public override ArcFile TryOpen (ArcView file)
+ {
+ if (!file.View.AsciiEqual (4, "Pack"))
+ return null;
+ int version = file.View.ReadInt32 (8);
+ if (version != 5)
+ return null;
+ uint name_length = file.View.ReadUInt32 (0xC);
+ if (name_length < 4)
+ return null;
+ uint name_key = file.View.ReadUInt32 (0x10);
+ var key = FindKey (file.Name, name_key);
+ if (null == key)
+ return null;
+ int count = file.View.ReadInt32 (0x10 + name_length);
+ if (!IsSaneCount (count))
+ return null;
+ var index = file.View.ReadBytes (0x14 + name_length, (uint)count * 0x20);
+ int pos = 0;
+ var dir = new List (count);
+ var name_builder = new StringBuilder();
+ for (int i = 0; i < count; ++i)
+ {
+ DecryptData (index, pos, 0x20, key[2], key[1]);
+ var entry = EntryFromMd5 (index, pos, name_builder);
+ entry.Offset = index.ToUInt32 (pos+0x10);
+ entry.Size = index.ToUInt32 (pos+0x14);
+ entry.UnpackedSize = index.ToUInt32 (pos+0x18);
+ if (!entry.CheckPlacement (file.MaxOffset))
+ return null;
+ entry.IsPacked = entry.Size != entry.UnpackedSize;
+ dir.Add (entry);
+ pos += 0x20;
+ }
+ return new ArcFile (file, this, dir);
+ }
+
+ public override Stream OpenEntry (ArcFile arc, Entry entry)
+ {
+ var rent = entry as RepiEntry;
+ if (null == rent || !rent.HasEncryptionKey)
+ return arc.File.CreateStream (entry.Offset, entry.Size);
+ var key = rent.CreateKey();
+ uint enc_length = Math.Min ((uint)key.Length, entry.Size);
+ byte[] encrypted = arc.File.View.ReadBytes (entry.Offset, enc_length);
+ DecryptEntry (encrypted, key);
+ Stream input;
+ if (enc_length == entry.Size)
+ {
+ input = new BinMemoryStream (encrypted, entry.Name);
+ }
+ else
+ {
+ input = arc.File.CreateStream (entry.Offset + enc_length, entry.Size - enc_length);
+ input = new PrefixStream (encrypted, input);
+ }
+ if (rent.IsPacked)
+ {
+ input = new LzssStream (input);
+ }
+ return input;
+ }
+
+ static void DecryptEntry (byte[] data, byte[] key)
+ {
+ for (int i = 0; i < data.Length; ++i)
+ {
+ data[i] ^= key[i];
+ }
+ }
+
+ static unsafe void DecryptData (byte[] data, int pos, int length, uint key, uint seed)
+ {
+ if (pos < 0 || pos + length > data.Length)
+ throw new ArgumentOutOfRangeException ("pos", "Invalid byte array index.");
+ fixed (byte* data8 = &data[pos])
+ {
+ uint* data32 = (uint*)data8;
+ for (int count = length / 4; count > 0; --count)
+ {
+ *data32 ^= key;
+ key += Binary.RotL (*data32, 16) ^ seed;
+ data32++;
+ }
+ }
+ }
+
+ RepiEntry EntryFromMd5 (byte[] data, int pos, StringBuilder builder)
+ {
+ var key = new CowArray (data, pos, 16).ToArray();
+ string name;
+ if (KnownNames.TryGetValue (key, out name))
+ {
+ var entry = FormatCatalog.Instance.Create (name);
+ entry.HasEncryptionKey = true;
+ return entry;
+ }
+ builder.Clear();
+ for (int i = 0; i < 16; ++i)
+ {
+ builder.AppendFormat ("{0:x2}", key[i]);
+ }
+ return new RepiEntry { Name = builder.ToString() };
+ }
+
+ static uint[] FindKey (string arc_name, uint arc_key)
+ {
+ arc_name = Path.GetFileName (arc_name);
+ var name_bytes = Encodings.cp932.GetBytes (arc_name);
+ arc_key ^= name_bytes.ToUInt32 (0);
+ return DatScheme.KnownSchemes.Values.FirstOrDefault (k => k[0] == arc_key);
+ }
+
+ static RepiScheme DatScheme = new RepiScheme { KnownSchemes = new Dictionary() };
+
+ public override ResourceScheme Scheme
+ {
+ get { return DatScheme; }
+ set { DatScheme = (RepiScheme)value; }
+ }
+
+ internal Dictionary KnownNames { get { return s_known_file_names.Value; } }
+
+ static Lazy> s_known_file_names = new Lazy> (ReadFileList);
+
+ static Dictionary ReadFileList ()
+ {
+ var dict = new Dictionary (new Md5Comparer());
+ try
+ {
+ var md5 = new MD5();
+ FormatCatalog.Instance.ReadFileList (ListFileName, name => {
+ var name_bytes = Encodings.cp932.GetBytes (name.ToLowerInvariant());
+ var hash = md5.ComputeHash (name_bytes);
+ dict[hash] = name;
+ });
+ }
+ catch (Exception X)
+ {
+ System.Diagnostics.Trace.WriteLine (X.Message, "[RepiPack]");
+ }
+ return dict;
+ }
+ }
+
+ internal class Md5Comparer : IEqualityComparer
+ {
+ public bool Equals (byte[] left, byte[] right)
+ {
+ if (left == null || right == null)
+ return left == right;
+ if (left.Length != right.Length)
+ return false;
+ for (int i = 0; i < left.Length; ++i)
+ {
+ if (left[i] != right[i])
+ return false;
+ }
+ return true;
+ }
+
+ public int GetHashCode (byte[] key)
+ {
+ if (null == key)
+ throw new ArgumentNullException ("key");
+ if (key.Length < 16)
+ throw new ArgumentException ("Invalid key length.", "key");
+ var hash = key.ToInt32 (0);
+ hash ^= key.ToInt32 (4);
+ hash ^= key.ToInt32 (8);
+ hash ^= key.ToInt32 (12);
+ return hash;
+ }
+ }
+}