Caching creative inventory entries (#5703)

Due to the high cost of Item::serializeCompoundTag(), it's very costly to rebuild this every time we need it. This is sent during the pre-spawn step, where we need to minimize costs as much as possible.

src/network/mcpe/cache/CreativeInventoryCache.php

@@ -0,0 +1,69 @@
+<?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\network\mcpe\cache;
+
+use pocketmine\inventory\CreativeInventory;
+use pocketmine\network\mcpe\convert\TypeConverter;
+use pocketmine\network\mcpe\protocol\CreativeContentPacket;
+use pocketmine\network\mcpe\protocol\types\inventory\CreativeContentEntry;
+use pocketmine\utils\SingletonTrait;
+use function spl_object_id;
+
+final class CreativeInventoryCache{
+	use SingletonTrait;
+
+	/**
+	 * @var CreativeContentPacket[]
+	 * @phpstan-var array<int, CreativeContentPacket>
+	 */
+	private array $caches = [];
+
+	public function getCache(CreativeInventory $inventory) : CreativeContentPacket{
+		$id = spl_object_id($inventory);
+		if(!isset($this->caches[$id])){
+			$inventory->getDestructorCallbacks()->add(function() use ($id) : void{
+				unset($this->caches[$id]);
+			});
+			$inventory->getContentChangedCallbacks()->add(function() use ($id) : void{
+				unset($this->caches[$id]);
+			});
+			$this->caches[$id] = $this->buildCreativeInventoryCache($inventory);
+		}
+		return $this->caches[$id];
+	}
+
+	/**
+	 * Rebuild the cache for the given inventory.
+	 */
+	private function buildCreativeInventoryCache(CreativeInventory $inventory) : CreativeContentPacket{
+		$entries = [];
+		$typeConverter = TypeConverter::getInstance();
+		//creative inventory may have holes if items were unregistered - ensure network IDs used are always consistent
+		foreach($inventory->getAll() as $k => $item){
+			$entries[] = new CreativeContentEntry($k, $typeConverter->coreItemStackToNet($item));
+		}
+
+		return CreativeContentPacket::create($entries);
+	}
+}