Added ConcurrentCache, a thread-safe Cache.

OpenRA.Game/OpenRA.Game.csproj

@@ -144,6 +144,7 @@
     <Compile Include="Player.cs" />
     <Compile Include="Primitives\MergedStream.cs" />
     <Compile Include="Primitives\SpatiallyPartitioned.cs" />
+    <Compile Include="Primitives\ConcurrentCache.cs" />
     <Compile Include="Selection.cs" />
     <Compile Include="Server\Connection.cs" />
     <Compile Include="Server\Exts.cs" />

OpenRA.Game/Primitives/Cache.cs

@@ -9,7 +9,6 @@
 #endregion
 
 using System;
-using System.Collections;
 using System.Collections.Generic;
 
 namespace OpenRA.Primitives
@@ -23,6 +22,7 @@ namespace OpenRA.Primitives
 		{
 			if (loader == null)
 				throw new ArgumentNullException("loader");
+
 			this.loader = loader;
 			cache = new Dictionary<T, U>(c);
 		}
@@ -32,13 +32,7 @@ namespace OpenRA.Primitives
 
 		public U this[T key]
 		{
-			get
+			get { return cache.GetOrAdd(key, loader); }
-			{
-				U result;
-				if (!cache.TryGetValue(key, out result))
-					cache.Add(key, result = loader(key));
-				return result;
-			}
 		}
 
 		public bool ContainsKey(T key) { return cache.ContainsKey(key); }
@@ -47,6 +41,6 @@ namespace OpenRA.Primitives
 		public ICollection<T> Keys { get { return cache.Keys; } }
 		public ICollection<U> Values { get { return cache.Values; } }
 		public IEnumerator<KeyValuePair<T, U>> GetEnumerator() { return cache.GetEnumerator(); }
-		IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
+		System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return GetEnumerator(); }
 	}
 }

OpenRA.Game/Primitives/ConcurrentCache.cs

@@ -0,0 +1,47 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2015 The OpenRA Developers (see AUTHORS)
+ * 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. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+
+namespace OpenRA.Primitives
+{
+	public class ConcurrentCache<T, U> : IReadOnlyDictionary<T, U>
+	{
+		readonly ConcurrentDictionary<T, U> cache;
+		readonly Func<T, U> loader;
+
+		public ConcurrentCache(Func<T, U> loader, IEqualityComparer<T> c)
+		{
+			if (loader == null)
+				throw new ArgumentNullException("loader");
+
+			this.loader = loader;
+			cache = new ConcurrentDictionary<T, U>(c);
+		}
+
+		public ConcurrentCache(Func<T, U> loader)
+			: this(loader, EqualityComparer<T>.Default) { }
+
+		public U this[T key]
+		{
+			get { return cache.GetOrAdd(key, loader); }
+		}
+
+		public bool ContainsKey(T key) { return cache.ContainsKey(key); }
+		public bool TryGetValue(T key, out U value) { return cache.TryGetValue(key, out value); }
+		public int Count { get { return cache.Count; } }
+		public ICollection<T> Keys { get { return cache.Keys; } }
+		public ICollection<U> Values { get { return cache.Values; } }
+		public IEnumerator<KeyValuePair<T, U>> GetEnumerator() { return cache.GetEnumerator(); }
+		System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return GetEnumerator(); }
+	}
+}