From 181dd3a7248cfd8b175dae10832f979fb780db89 Mon Sep 17 00:00:00 2001
From: MishaIac <47920105+MishaIac@users.noreply.github.com>
Date: Sun, 1 Feb 2026 13:14:09 +0200
Subject: [PATCH] Add support for NEKO WORKs Unity PACK/EXFS resource archive

Tested on Nie no Hakoniwa (Steam version)
---
 ArcFormats/ArcFormats.csproj    |  1 +
 ArcFormats/NEKOWORKs/ArcPACK.cs | 99 +++++++++++++++++++++++++++++++++
 2 files changed, 100 insertions(+)
 create mode 100644 ArcFormats/NEKOWORKs/ArcPACK.cs

diff --git a/ArcFormats/ArcFormats.csproj b/ArcFormats/ArcFormats.csproj
index 03512193..09a44aec 100644
--- a/ArcFormats/ArcFormats.csproj
+++ b/ArcFormats/ArcFormats.csproj
@@ -221,6 +221,7 @@
     <Compile Include="MAGES\ImageBIN.cs" />
     <Compile Include="Mugi\ArcBIN.cs" />
     <Compile Include="Musica\ArcPAK.cs" />
+    <Compile Include="NEKOWORKs\ArcPACK.cs" />
     <Compile Include="NipponIchi\ArcCASN.cs" />
     <Compile Include="NipponIchi\ArcPSFS.cs" />
     <Compile Include="NipponIchi\ImageNMT.cs" />
diff --git a/ArcFormats/NEKOWORKs/ArcPACK.cs b/ArcFormats/NEKOWORKs/ArcPACK.cs
new file mode 100644
index 00000000..38962c74
--- /dev/null
+++ b/ArcFormats/NEKOWORKs/ArcPACK.cs
@@ -0,0 +1,99 @@
+//! \file       ArcPACK.cs
+//! \date       2026 Feb 01
+//! \brief      NEKO WORKs Unity PACK resource archive.
+//
+// Copyright (C) 2026 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 GameRes.Formats;
+
+namespace GameRes.Formats.NEKOWORKs
+{
+    [Export(typeof(ArchiveFormat))]
+    public class NekoWorksPackOpener : ArchiveFormat
+    {
+        public override string Tag { get { return "PACK/EXFS"; } }
+        public override string Description { get { return "NEKO WORKs resource archive"; } }
+        public override uint Signature { get { return 0x53465845; } } // 'EXFS'
+        public override bool IsHierarchic { get { return true; } }
+        public override bool CanWrite { get { return false; } }
+
+        public override ArcFile TryOpen(ArcView file)
+        {
+            if (!file.View.AsciiEqual(0, "EXFS"))
+                return null;
+
+            int fileCount = file.View.ReadInt32(0x0C);
+            uint infoOffset = file.View.ReadUInt32(0x10);
+            uint infoSize = file.View.ReadUInt32(0x18);
+            uint nameBlockSize = file.View.ReadUInt32(0x20);
+            uint baseDataOffset = file.View.ReadUInt32(0x28);
+
+            if (!IsSaneCount(fileCount))
+                return null;
+
+            long namesOffset = infoOffset + infoSize;
+            if (namesOffset + nameBlockSize > file.MaxOffset)
+                return null;
+
+            byte[] nameData = file.View.ReadBytes(namesOffset, nameBlockSize);
+            var nameList = new List<string>(fileCount);
+            int start = 0;
+            for (int i = 0; i < nameData.Length; ++i)
+            {
+                if (nameData[i] == (byte)'\n')
+                {
+                    if (i > start)
+                        nameList.Add(System.Text.Encoding.UTF8.GetString(nameData, start, i - start));
+                    start = i + 1;
+                }
+            }
+
+            if (nameList.Count < fileCount)
+                return null;
+
+            var dir = new List<Entry>(fileCount);
+            long indexOffset = infoOffset;
+
+            for (int i = 0; i < fileCount; ++i)
+            {
+                long entryPos = indexOffset + i * 0x20;
+
+                uint dataOffset = file.View.ReadUInt32(entryPos + 0x10);
+                uint dataSize = file.View.ReadUInt32(entryPos + 0x18);
+
+                var entry = Create<Entry>(nameList[i]);
+                entry.Offset = baseDataOffset + dataOffset;
+                entry.Size = dataSize;
+
+                if (!entry.CheckPlacement(file.MaxOffset))
+                    return null;
+
+                dir.Add(entry);
+            }
+
+            return new ArcFile(file, this, dir);
+        }
+    }
+}