diff --git a/ArcFormats/ArcFormats.csproj b/ArcFormats/ArcFormats.csproj
index a1d326a3..4dec5d1d 100644
--- a/ArcFormats/ArcFormats.csproj
+++ b/ArcFormats/ArcFormats.csproj
@@ -75,6 +75,7 @@
+
diff --git a/ArcFormats/ArcNEKO.cs b/ArcFormats/ArcNEKO.cs
new file mode 100644
index 00000000..19b89a5e
--- /dev/null
+++ b/ArcFormats/ArcNEKO.cs
@@ -0,0 +1,194 @@
+//! \file ArcNEKO.cs
+//! \date Fri Mar 13 02:27:53 2015
+//! \brief Nekopack archive format implementation.
+//
+// Copyright (C) 2015 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 GameRes.Utility;
+
+namespace GameRes.Formats.Neko
+{
+ public class NekoArchive : ArcFile
+ {
+ public uint Key { get; private set; }
+
+ public NekoArchive (ArcView arc, ArchiveFormat impl, ICollection dir, uint key)
+ : base (arc, impl, dir)
+ {
+ Key = key;
+ }
+ }
+
+ [Export(typeof(ArchiveFormat))]
+ public class PakOpener : ArchiveFormat
+ {
+ public override string Tag { get { return "NEKO"; } }
+ public override string Description { get { return "NekoPack resource archive"; } }
+ public override uint Signature { get { return 0x4f4b454e; } } // "NEKO"
+ public override bool IsHierarchic { get { return false; } }
+ public override bool CanCreate { get { return false; } }
+
+ public PakOpener ()
+ {
+ Extensions = new string[] { "dat" };
+ }
+
+ public override ArcFile TryOpen (ArcView file)
+ {
+ if (!file.View.AsciiEqual (4, "PACK"))
+ return null;
+ uint id = file.View.ReadUInt32 (8);
+ int length;
+ byte[] index = ReadBlock (file.View, id, 0x10, out length);
+ int total = 0;
+ long offset = 0x18 + length;
+ var dir = new List();
+ int index_pos = 0;
+ for (int remaining = length; remaining > 0;)
+ {
+ int count = LittleEndian.ToInt32 (index, index_pos+4);
+ if (count <= 0 || count > remaining/8-1)
+ return null;
+ total += count;
+ dir.Capacity = total;
+ index_pos += 8;
+ for (int j = 0; j < count; ++j)
+ {
+ var entry = new Entry
+ { Offset = offset, Size = LittleEndian.ToUInt32 (index, index_pos+4) };
+ if (!entry.CheckPlacement (file.MaxOffset))
+ return null;
+ index_pos += 8;
+ offset += entry.Size + 8;
+ dir.Add (entry);
+ }
+ remaining -= 8 + count * 8;
+ }
+ int i = 0;
+ byte[] buffer = new byte[0x10];
+ foreach (var entry in dir)
+ {
+ file.View.Read (entry.Offset, buffer, 0, 0x10);
+ uint hash = LittleEndian.ToUInt32 (buffer, 0);
+ if (0 != hash)
+ {
+ ulong key = KeyFromHash (hash);
+ Decrypt (key, buffer, 8, 8);
+ }
+ uint signature = LittleEndian.ToUInt32 (buffer, 8);
+ var res = FormatCatalog.Instance.LookupSignature (signature);
+ string ext = "";
+ if (res.Any())
+ {
+ ext = res.First().Extensions.First();
+ entry.Type = res.First().Type;
+ }
+ else if (0x474e4d8a == signature)
+ ext = "mng";
+ if (!string.IsNullOrEmpty (ext))
+ entry.Name = string.Format ("{0:D4}.{1}", i, ext);
+ else
+ entry.Name = i.ToString ("D4");
+ ++i;
+ }
+ return new NekoArchive (file, this, dir, id);
+ }
+
+ public override Stream OpenEntry (ArcFile arc, Entry entry)
+ {
+ var pak = arc as NekoArchive;
+ if (null == pak)
+ return arc.File.CreateStream (entry.Offset, entry.Size);
+ int length;
+ var data = ReadBlock (arc.File.View, pak.Key, entry.Offset, out length);
+ return new MemoryStream (data, false);
+ }
+
+ static ulong KeyFromHash (uint hash)
+ {
+ uint v2 = hash ^ (hash + 1566083941u);
+ uint v3 = v2 ^ (hash - 899497514u);
+ ulong result = v3 ^ (v2 - 1894007588u);
+ return result | (result ^ (v3 + 1812433253u)) << 32;
+ }
+
+ static uint CalcParity (uint a1, uint a2)
+ {
+ uint v1 = (a2 ^ ((a2 ^ ((a2 ^ ((a2 ^ a1) + 1566083941u)) - 899497514u)) - 1894007588u)) + 1812433253u;
+ int v2 = (int)(((a2 ^ ((a2 ^ a1) + 1566083941u)) - 899497514u) >> 27);
+ return v1 << v2 | v1 >> (32-v2);
+ }
+
+ static ulong Decrypt (ulong key, byte[] buf, int offset, int length)
+ {
+ unsafe
+ {
+ fixed (byte* data = buf)
+ {
+ ulong* first = (ulong*)(data + offset);
+ ulong* last = first + length/8;
+ while (first != last)
+ {
+ ulong v = *first ^ key;
+ key = _m_paddw (key, v);
+ *first++ = v;
+ }
+ return key;
+ }
+ }
+ }
+
+ static ulong _m_paddw (ulong x, ulong y)
+ {
+ ulong mask = 0xffff;
+ ulong r = ((x & mask) + (y & mask)) & mask;
+ mask <<= 16;
+ r |= ((x & mask) + (y & mask)) & mask;
+ mask <<= 16;
+ r |= ((x & mask) + (y & mask)) & mask;
+ mask <<= 16;
+ r |= ((x & mask) + (y & mask)) & mask;
+ return r;
+ }
+
+ static byte[] ReadBlock (ArcView.Frame view, uint id, long offset, out int length)
+ {
+ uint hash = view.ReadUInt32 (offset);
+ length = view.ReadInt32 (offset+4);
+
+ int aligned_size = (length+7) & ~7;
+ byte[] buffer = new byte[aligned_size];
+ view.Read (offset+8, buffer, 0, (uint)length);
+ if (0 != hash)
+ {
+ ulong key = KeyFromHash (hash);
+ Decrypt (key, buffer, 0, aligned_size);
+ }
+ return buffer;
+ }
+ }
+}