diff --git a/ArcFormats/ArcGSP.cs b/ArcFormats/ArcGSP.cs
index f87e0457..d490935e 100644
--- a/ArcFormats/ArcGSP.cs
+++ b/ArcFormats/ArcGSP.cs
@@ -65,4 +65,53 @@ namespace GameRes.Formats.BlackRainbow
             return new ArcFile (file, this, dir);
         }
     }
+
+    [Export(typeof(ArchiveFormat))]
+    public class DatOpener : ArchiveFormat
+    {
+        public override string         Tag { get { return "BR/DAT"; } }
+        public override string Description { get { return "BlackRainbow resource archive"; } }
+        public override uint     Signature { get { return 0; } }
+        public override bool  IsHierarchic { get { return false; } }
+        public override bool     CanCreate { get { return false; } }
+
+        public DatOpener ()
+        {
+            Extensions = new string[] { "dat", "pak" };
+        }
+
+        public override ArcFile TryOpen (ArcView file)
+        {
+            uint sig = file.View.ReadUInt32 (0);
+            if (sig != 2 && sig != 4 && sig != 5)
+                return null;
+            int count = file.View.ReadInt32 (8);
+            if (count <= 0 || count > 0x1ffff)
+                return null;
+            uint base_offset = file.View.ReadUInt32 (0x0c);
+            uint index_offset = 0x10;
+            uint index_size = 4u * (uint)count;
+            if (index_size > file.View.Reserve (index_offset, index_size))
+                return null;
+            var index = new List<uint> (count);
+            for (int i = 0; i < count; ++i)
+            {
+                uint offset = file.View.ReadUInt32 (index_offset);
+                if (offset != 0xffffffff)
+                    index.Add (base_offset + offset);
+                index_offset += 4;
+            }
+            var dir = new List<Entry> (index.Count);
+            for (int i = 0; i < index.Count; ++i)
+            {
+                long offset = index[i];
+                string name = file.View.ReadString (offset, 0x20);
+                var entry = FormatCatalog.Instance.CreateEntry (name);
+                entry.Offset = offset + 0x24;
+                entry.Size   = file.View.ReadUInt32 (offset+0x20);
+                dir.Add (entry);
+            }
+            return new ArcFile (file, this, dir);
+        }
+    }
 }