From 25f06a1c98c446e3ae4e6f0ab5bb989f77d29c83 Mon Sep 17 00:00:00 2001
From: scientificworld <scientificworld@users.noreply.github.com>
Date: Wed, 7 Jan 2026 12:02:14 +0800
Subject: [PATCH] chore: code enhancement

---
 ArcFormats/Nexas/ArcPAC.cs | 15 +++++++++++----
 Legacy/Duke/ArcDAT.cs      |  5 ++++-
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/ArcFormats/Nexas/ArcPAC.cs b/ArcFormats/Nexas/ArcPAC.cs
index c62c6977..2aa5fded 100644
--- a/ArcFormats/Nexas/ArcPAC.cs
+++ b/ArcFormats/Nexas/ArcPAC.cs
@@ -45,7 +45,14 @@ namespace GameRes.Formats.NeXAS
         None2,
         Zstd,
         ZstdOrNone,
-        NeedDecryptionOnly = 0xFDFD, // magic number, no actual meaning
+        NeedDecryptionOnly = 0xFDFD, // internal magic number
+    }
+
+    internal interface INexasIndexReader
+    {
+        Compression PackType { get; }
+
+        List<Entry> Read ();
     }
 
     public class PacArchive : ArcFile
@@ -82,7 +89,7 @@ namespace GameRes.Formats.NeXAS
                 return null;
 
             List<Entry> dir = null;
-            dynamic reader = new IndexReader (file, PacEncoding.Get<Encoding>());
+            INexasIndexReader reader = new IndexReader (file, PacEncoding.Get<Encoding>());
             try
             {
                 dir = reader.Read();
@@ -103,7 +110,7 @@ namespace GameRes.Formats.NeXAS
             return new PacArchive (file, this, dir, reader.PackType);
         }
 
-        internal sealed class IndexReader
+        internal sealed class IndexReader : INexasIndexReader
         {
             ArcView     m_file;
             int         m_count;
@@ -205,7 +212,7 @@ namespace GameRes.Formats.NeXAS
             }
         }
 
-        internal sealed class OldIndexReader
+        internal sealed class OldIndexReader : INexasIndexReader
         {
             ArcView     m_file;
             uint        m_header_size;
diff --git a/Legacy/Duke/ArcDAT.cs b/Legacy/Duke/ArcDAT.cs
index 2a5d70d3..ffb6f9ee 100644
--- a/Legacy/Duke/ArcDAT.cs
+++ b/Legacy/Duke/ArcDAT.cs
@@ -42,8 +42,11 @@ namespace GameRes.Formats.Duke
 
         public override ArcFile TryOpen (ArcView file)
         {
+            if (!file.Name.HasExtension (".dat"))
+                return null;
+
             int count = (int)(file.View.ReadUInt32 (0) ^ 0xfa261efb);
-            if (!file.Name.HasExtension (".dat") || !IsSaneCount (count))
+            if (!IsSaneCount (count))
                 return null;
 
             uint index_offset = 4;