Performance Fish

Source/PerformanceFish/Cache/ByMap.cs

@@ -0,0 +1,46 @@
+// Copyright (c) 2022 bradson
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+namespace PerformanceFish.Cache;
+public static class ByMap<T> where T : new()
+{
+	private static List<(Map map, T value)> _cache = new();
+	[ThreadStatic]
+	private static List<(Map map, T value)>? _cacheThreadStatic;
+
+	public static List<(Map map, T value)> GetCache
+		=> UnityData.IsInMainThread ? _cache
+		: _cacheThreadStatic ??= Utility.AddNew<List<(Map map, T value)>>();
+
+	public static List<(Map map, T value)> GetCacheDirectly => _cache;
+
+	static ByMap() => Utility.All.Add(_cache);
+
+	private static Func<Map, T> Initialize { get; }
+		= typeof(MapComponent).IsAssignableFrom(typeof(T))
+		? AccessTools.MethodDelegate<Func<Map, T>>(AccessTools.Method(typeof(Map), nameof(Map.GetComponent), Array.Empty<Type>(), new[] { typeof(T) }))
+		// missing T constraints cause the compiler to complain when trying to just use map => map.GetComponent<T>
+		: _ => new();
+
+	public static T GetFor(Map map)
+	{
+		var cache = GetCache;
+		for (var i = 0; i < cache.Count; i++)
+		{
+			var cacheEntry = cache[i];
+			if (cacheEntry.map == map)
+				return cacheEntry.value;
+
+			if (Find.Maps.Count <= i + 1
+				&& !Find.Maps.Contains(cacheEntry.map))
+			{
+				cache.RemoveAt(i);
+				i--;
+			}
+		}
+		cache.Add((map, Initialize(map)));
+		return cache[^1].value;
+	}
+}