wrap up block_id_map in a class

src/data/bedrock/LegacyBlockIdToStringIdMap.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\data\bedrock;
+
+use pocketmine\utils\AssumptionFailedError;
+use pocketmine\utils\SingletonTrait;
+use function file_get_contents;
+use function is_array;
+use function is_int;
+use function is_string;
+use function json_decode;
+
+final class LegacyBlockIdToStringIdMap{
+	use SingletonTrait;
+
+	/**
+	 * @var string[]
+	 * @phpstan-var array<int, string>
+	 */
+	private $legacyToString = [];
+	/**
+	 * @var int[]
+	 * @phpstan-var array<string, int>
+	 */
+	private $stringToLegacy = [];
+
+	public function __construct(){
+		$stringToLegacyId = json_decode(file_get_contents(\pocketmine\RESOURCE_PATH . 'vanilla/block_id_map.json'), true);
+		if(!is_array($stringToLegacyId)){
+			throw new AssumptionFailedError("Invalid format of block_id_map");
+		}
+		foreach($stringToLegacyId as $stringId => $legacyId){
+			if(!is_string($stringId) or !is_int($legacyId)){
+				throw new AssumptionFailedError("Block ID map should have string keys and int values");
+			}
+			$this->legacyToString[$legacyId] = $stringId;
+			$this->stringToLegacy[$stringId] = $legacyId;
+		}
+	}
+
+	public function legacyToString(int $legacy) : ?string{
+		return $this->legacyToString[$legacy] ?? null;
+	}
+
+	public function stringToLegacy(string $string) : ?int{
+		return $this->stringToLegacy[$string] ?? null;
+	}
+}

src/network/mcpe/convert/RuntimeBlockMapping.php

@@ -24,6 +24,7 @@ declare(strict_types=1);
 namespace pocketmine\network\mcpe\convert;
 
 use pocketmine\block\BlockLegacyIds;
+use pocketmine\data\bedrock\LegacyBlockIdToStringIdMap;
 use pocketmine\nbt\NBT;
 use pocketmine\nbt\tag\CompoundTag;
 use pocketmine\nbt\tag\ListTag;
@@ -31,7 +32,6 @@ use pocketmine\network\mcpe\protocol\types\CacheableNbt;
 use pocketmine\network\mcpe\serializer\NetworkNbtSerializer;
 use function file_get_contents;
 use function getmypid;
-use function json_decode;
 use function mt_rand;
 use function mt_srand;
 use function shuffle;
@@ -77,7 +77,7 @@ final class RuntimeBlockMapping{
 	}
 
 	private function setupLegacyMappings() : void{
-		$legacyIdMap = json_decode(file_get_contents(\pocketmine\RESOURCE_PATH . "vanilla/block_id_map.json"), true);
+		$legacyIdMap = LegacyBlockIdToStringIdMap::getInstance();
 		$legacyStateMap = (new NetworkNbtSerializer())->read(file_get_contents(\pocketmine\RESOURCE_PATH . "vanilla/r12_to_current_block_map.nbt"))->getTag();
 		if(!($legacyStateMap instanceof ListTag) or $legacyStateMap->getTagType() !== NBT::TAG_Compound){
 			throw new \RuntimeException("Invalid legacy states mapping table, expected TAG_List<TAG_Compound> root");
@@ -93,7 +93,10 @@ final class RuntimeBlockMapping{
 		/** @var CompoundTag $pair */
 		foreach($legacyStateMap as $pair){
 			$oldState = $pair->getCompoundTag("old");
-			$id = $legacyIdMap[$oldState->getString("name")];
+			$id = $legacyIdMap->stringToLegacy($oldState->getString("name"));
+			if($id === null){
+				throw new \RuntimeException("State does not have a legacy ID");
+			}
 			$data = $oldState->getShort("val");
 			if($data > 15){
 				//we can't handle metadata with more than 4 bits

src/world/format/io/leveldb/LevelDB.php

@@ -24,6 +24,7 @@ declare(strict_types=1);
 namespace pocketmine\world\format\io\leveldb;
 
 use pocketmine\block\BlockLegacyIds;
+use pocketmine\data\bedrock\LegacyBlockIdToStringIdMap;
 use pocketmine\nbt\LittleEndianNbtSerializer;
 use pocketmine\nbt\NbtDataException;
 use pocketmine\nbt\tag\CompoundTag;
@@ -45,7 +46,6 @@ use pocketmine\world\format\io\WritableWorldProvider;
 use pocketmine\world\format\PalettedBlockArray;
 use pocketmine\world\format\SubChunk;
 use pocketmine\world\generator\Generator;
-use function array_flip;
 use function array_map;
 use function array_values;
 use function chr;
@@ -53,9 +53,7 @@ use function count;
 use function defined;
 use function extension_loaded;
 use function file_exists;
-use function file_get_contents;
 use function is_dir;
-use function json_decode;
 use function mkdir;
 use function ord;
 use function str_repeat;
@@ -153,11 +151,6 @@ class LevelDB extends BaseWorldProvider implements WritableWorldProvider{
 	}
 
 	protected function deserializePaletted(BinaryStream $stream) : PalettedBlockArray{
-		static $stringToLegacyId = null;
-		if($stringToLegacyId === null){
-			$stringToLegacyId = json_decode(file_get_contents(\pocketmine\RESOURCE_PATH . 'vanilla/block_id_map.json'), true);
-		}
-
 		$bitsPerBlock = $stream->getByte() >> 1;
 
 		try{
@@ -167,12 +160,13 @@ class LevelDB extends BaseWorldProvider implements WritableWorldProvider{
 		}
 		$nbt = new LittleEndianNbtSerializer();
 		$palette = [];
+		$idMap = LegacyBlockIdToStringIdMap::getInstance();
 		for($i = 0, $paletteSize = $stream->getLInt(); $i < $paletteSize; ++$i){
 			$offset = $stream->getOffset();
 			$tag = $nbt->read($stream->getBuffer(), $offset)->mustGetCompoundTag();
 			$stream->setOffset($offset);
 
-			$id = $stringToLegacyId[$tag->getString("name")] ?? BlockLegacyIds::INFO_UPDATE;
+			$id = $idMap->stringToLegacy($tag->getString("name")) ?? BlockLegacyIds::INFO_UPDATE;
 			$data = $tag->getShort("val");
 			$palette[] = ($id << 4) | $data;
 		}
@@ -419,10 +413,7 @@ class LevelDB extends BaseWorldProvider implements WritableWorldProvider{
 	}
 
 	protected function writeChunk(Chunk $chunk) : void{
-		static $idMap = null;
-		if($idMap === null){
-			$idMap = array_flip(json_decode(file_get_contents(\pocketmine\RESOURCE_PATH . 'vanilla/block_id_map.json'), true));
-		}
+		$idMap = LegacyBlockIdToStringIdMap::getInstance();
 		$index = LevelDB::chunkIndex($chunk->getX(), $chunk->getZ());
 
 		$write = new \LevelDBWriteBatch();
@@ -449,7 +440,7 @@ class LevelDB extends BaseWorldProvider implements WritableWorldProvider{
 						$tags = [];
 						foreach($palette as $p){
 							$tags[] = new TreeRoot(CompoundTag::create()
-								->setString("name", $idMap[$p >> 4] ?? "minecraft:info_update")
+								->setString("name", $idMap->legacyToString($p >> 4) ?? "minecraft:info_update")
 								->setInt("oldid", $p >> 4) //PM only (debugging), vanilla doesn't have this
 								->setShort("val", $p & 0xf));
 						}