generation: drop AsyncWorker thread-local storage in favour of a more specialized storage

src/world/generator/ThreadLocalGeneratorContext.php

@@ -0,0 +1,63 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\world\generator;
+
+use pocketmine\world\SimpleChunkManager;
+
+/**
+ * Manages thread-local caches for generators and the things needed to support them
+ */
+final class ThreadLocalGeneratorContext{
+	/**
+	 * @var self[]
+	 * @phpstan-var array<int, self>
+	 */
+	private static $contexts = [];
+
+	public static function register(self $context, int $worldId) : void{
+		self::$contexts[$worldId] = $context;
+	}
+
+	public static function unregister(int $worldId) : void{
+		unset(self::$contexts[$worldId]);
+	}
+
+	public static function fetch(int $worldId) : ?self{
+		return self::$contexts[$worldId] ?? null;
+	}
+
+	/** @var Generator */
+	private $generator;
+	/** @var SimpleChunkManager */
+	private $chunkManager;
+
+	public function __construct(Generator $generator, SimpleChunkManager $chunkManager){
+		$this->generator = $generator;
+		$this->chunkManager = $chunkManager;
+	}
+
+	public function getGenerator() : Generator{ return $this->generator; }
+
+	public function getChunkManager() : SimpleChunkManager{ return $this->chunkManager; }
+}