From 24262179f3f1b9e735c3656bd5c0543f2428d1ec Mon Sep 17 00:00:00 2001
From: Crsky <crskycode@hotmail.com>
Date: Mon, 14 Apr 2025 02:38:00 +0800
Subject: [PATCH] (Valkyria): Support V1 resource archive

---
 ArcFormats/Valkyria/ArcDAT.cs | 78 +++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)

diff --git a/ArcFormats/Valkyria/ArcDAT.cs b/ArcFormats/Valkyria/ArcDAT.cs
index ede8dacb..ac2c6eec 100644
--- a/ArcFormats/Valkyria/ArcDAT.cs
+++ b/ArcFormats/Valkyria/ArcDAT.cs
@@ -23,8 +23,11 @@
 // IN THE SOFTWARE.
 //
 
+using System;
 using System.Collections.Generic;
 using System.ComponentModel.Composition;
+using System.IO;
+using System.Linq;
 
 namespace GameRes.Formats.Valkyria
 {
@@ -40,6 +43,8 @@ namespace GameRes.Formats.Valkyria
         public override ArcFile TryOpen (ArcView file)
         {
             uint index_size = file.View.ReadUInt32 (0);
+            if (0 == index_size)
+                return TryOpenV1 (file);
             if (0 == index_size || index_size >= file.MaxOffset)
                 return null;
             int count = (int)index_size / 0x10C;
@@ -62,5 +67,78 @@ namespace GameRes.Formats.Valkyria
             }
             return new ArcFile (file, this, dir);
         }
+
+        private ArcFile TryOpenV1(ArcView file)
+        {
+            var index_size = file.View.ReadUInt32 (4);
+            if (0 == index_size || index_size >= file.MaxOffset)
+                return null;
+            int count = (int)index_size / 0x10C;
+            if (index_size != (uint)count * 0x10Cu || !IsSaneCount (count))
+                return null;
+            var dir_path = Path.GetDirectoryName (file.Name);
+            if (null == dir_path)
+                return null;
+            var arc_key = ReadArcKey (dir_path);
+            if (null == arc_key)
+                return null;
+            uint index_offset = 8;
+            long base_offset = index_offset + index_size;
+            var dir = new List<Entry> (count);
+            for (int i = 0; i < count; ++i)
+            {
+                var name = file.View.ReadString (index_offset, 0x104);
+                var key = GetEntryKey (arc_key, file.View.ReadBytes (index_offset, 0x104));
+                index_offset += 0x104;
+                var entry = FormatCatalog.Instance.Create<Entry> (name);
+                entry.Offset = base_offset + (file.View.ReadUInt32 (index_offset) ^ key);
+                entry.Size = file.View.ReadUInt32 (index_offset + 4) ^ key;
+                if (!entry.CheckPlacement (file.MaxOffset))
+                    return null;
+                index_offset += 8;
+                dir.Add (entry);
+            }
+            return new ArcFile (file, this, dir);
+        }
+
+        private static byte[] ReadArcKey (string dir_path)
+        {
+            var file_path = Path.Combine (dir_path, "system.dat");
+            if (!File.Exists (file_path))
+                return null;
+            var info = new byte[260];
+            using (var fs = File.OpenRead (file_path))
+            {
+                fs.Position = 0x10E;
+                fs.Read (info, 0, 260);
+                fs.Close ();
+            }
+            var key = new byte[4];
+            var len = info.TakeWhile (x => x != 0).Count ();
+            for (int i = len, j = 0; i != 0; i--)
+            {
+                key[j] += info[i];
+                if (++j == 4)
+                    j = 0;
+            }
+            return key;
+        }
+
+        private static uint GetEntryKey (byte[] arc_key, byte[] name)
+        {
+            var key = new byte[4];
+            var len = name.TakeWhile (x => x != 0).Count ();
+            for (int i = len, j = 0; i != 0; i--)
+            {
+                key[j] += name[i];
+                if (++j == 4)
+                    j = 0;
+            }
+            key[0] += arc_key[3];
+            key[1] += arc_key[2];
+            key[2] += arc_key[1];
+            key[3] += arc_key[0];
+            return BitConverter.ToUInt32 (key, 0);
+        }
     }
 }