Introduce a reference counting file store

osu.Game/IO/FileInfo.cs

@@ -0,0 +1,24 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System.IO;
+using SQLite.Net.Attributes;
+
+namespace osu.Game.IO
+{
+    public class FileInfo
+    {
+        [PrimaryKey, AutoIncrement]
+        public int ID { get; set; }
+
+        public string Filename { get; set; }
+
+        [Indexed(Unique = true)]
+        public string Hash { get; set; }
+
+        public string StoragePath => Path.Combine(Hash.Remove(1), Hash.Remove(2), Hash);
+
+        [Indexed]
+        public int ReferenceCount { get; set; }
+    }
+}