Move CachedTransform to OpenRA.Primitives.

OpenRA.Game/Primitives/CachedTransform.cs

@@ -0,0 +1,41 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+
+namespace OpenRA.Primitives
+{
+	public class CachedTransform<T, U>
+	{
+		readonly Func<T, U> transform;
+
+		bool initialized;
+		T lastInput;
+		U lastOutput;
+
+		public CachedTransform(Func<T, U> transform)
+		{
+			this.transform = transform;
+		}
+
+		public U Update(T input)
+		{
+			if (initialized && ((input == null && lastInput == null) || (input != null && input.Equals(lastInput))))
+				return lastOutput;
+
+			lastInput = input;
+			lastOutput = transform(input);
+			initialized = true;
+
+			return lastOutput;
+		}
+	}
+}