extract a BiomeArray unit from Chunk

this now also properly validates data read from disk.

src/world/format/BiomeArray.php

@@ -0,0 +1,67 @@
+<?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\format;
+
+use function strlen;
+
+final class BiomeArray{
+
+	/** @var string */
+	private $payload;
+
+	/**
+	 * @param string $payload ZZZZXXXX key bits
+	 */
+	public function __construct(string $payload){
+		if(strlen($payload) !== 256){
+			throw new \InvalidArgumentException("Biome array is expected to be exactly 256 bytes");
+		}
+		$this->payload = $payload;
+	}
+
+	private static function idx(int $x, int $z) : int{
+		if($x >= 16 or $z >= 16){
+			throw new \InvalidArgumentException("x and z must be in the range 0-15");
+		}
+		return ($z << 4) | $x;
+	}
+
+	public function get(int $x, int $z) : int{
+		return ord($this->payload[self::idx($x, $z)]);
+	}
+
+	public function set(int $x, int $z, int $biomeId) : void{
+		if($biomeId < 0 or $biomeId >= 256){
+			throw new \InvalidArgumentException("Biome ID must be in the range 0-255");
+		}
+		$this->payload[self::idx($x, $z)] = chr($biomeId);
+	}
+
+	/**
+	 * @return string ZZZZXXXX key bits
+	 */
+	public function getData() : string{
+		return $this->payload;
+	}
+}

src/world/format/Chunk.php

@@ -87,7 +87,7 @@ class Chunk{
 	 */
 	protected $heightMap;
 
-	/** @var string */
+	/** @var BiomeArray */
 	protected $biomeIds;
 
 	/** @var CompoundTag[]|null */
@@ -102,7 +102,7 @@ class Chunk{
 	 * @param CompoundTag[] $tiles
 	 * @param int[]         $heightMap
 	 */
-	public function __construct(int $chunkX, int $chunkZ, array $subChunks = [], ?array $entities = null, ?array $tiles = null, string $biomeIds = "", array $heightMap = []){
+	public function __construct(int $chunkX, int $chunkZ, array $subChunks = [], ?array $entities = null, ?array $tiles = null, ?BiomeArray $biomeIds = null, array $heightMap = []){
 		$this->x = $chunkX;
 		$this->z = $chunkZ;
 
@@ -120,12 +120,7 @@ class Chunk{
 			$this->heightMap = \SplFixedArray::fromArray(array_fill(0, 256, $val));
 		}
 
-		if(strlen($biomeIds) === 256){
+		$this->biomeIds = $biomeIds ?? new BiomeArray(str_repeat("\x00", 256));
-			$this->biomeIds = $biomeIds;
-		}else{
-			assert($biomeIds === "", "Wrong BiomeIds value count, expected 256, got " . strlen($biomeIds));
-			$this->biomeIds = str_repeat("\x00", 256);
-		}
 
 		$this->NBTtiles = $tiles;
 		$this->NBTentities = $entities;
@@ -359,7 +354,7 @@ class Chunk{
 	 * @return int 0-255
 	 */
 	public function getBiomeId(int $x, int $z) : int{
-		return ord($this->biomeIds[($z << 4) | $x]);
+		return $this->biomeIds->get($x, $z);
 	}
 
 	/**
@@ -370,7 +365,7 @@ class Chunk{
 	 * @param int $biomeId 0-255
 	 */
 	public function setBiomeId(int $x, int $z, int $biomeId) : void{
-		$this->biomeIds[($z << 4) | $x] = chr($biomeId & 0xff);
+		$this->biomeIds->set($x, $z, $biomeId);
 		$this->dirtyFlags |= self::DIRTY_FLAG_BIOMES;
 	}
 
@@ -550,7 +545,7 @@ class Chunk{
 	}
 
 	public function getBiomeIdArray() : string{
-		return $this->biomeIds;
+		return $this->biomeIds->getData();
 	}
 
 	/**

src/world/format/io/FastChunkSerializer.php

@@ -25,6 +25,7 @@ namespace pocketmine\world\format\io;
 
 use pocketmine\block\BlockLegacyIds;
 use pocketmine\utils\BinaryStream;
+use pocketmine\world\format\BiomeArray;
 use pocketmine\world\format\Chunk;
 use pocketmine\world\format\LightArray;
 use pocketmine\world\format\PalettedBlockArray;
@@ -111,7 +112,7 @@ final class FastChunkSerializer{
 		$terrainGenerated = (bool) ($flags & 1);
 
 		$subChunks = [];
-		$biomeIds = "";
+		$biomeIds = null;
 		$heightMap = [];
 		if($terrainGenerated){
 			$count = $stream->getByte();
@@ -132,7 +133,7 @@ final class FastChunkSerializer{
 				);
 			}
 
-			$biomeIds = $stream->get(256);
+			$biomeIds = new BiomeArray($stream->get(256));
 			if($lightPopulated){
 				$heightMap = array_values(unpack("S*", $stream->get(512)));
 			}

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

@@ -33,6 +33,7 @@ use pocketmine\utils\Binary;
 use pocketmine\utils\BinaryDataException;
 use pocketmine\utils\BinaryStream;
 use pocketmine\utils\Utils;
+use pocketmine\world\format\BiomeArray;
 use pocketmine\world\format\Chunk;
 use pocketmine\world\format\io\BaseWorldProvider;
 use pocketmine\world\format\io\ChunkUtils;
@@ -232,8 +233,8 @@ class LevelDB extends BaseWorldProvider implements WritableWorldProvider{
 		/** @var SubChunk[] $subChunks */
 		$subChunks = [];
 
-		/** @var string $biomeIds */
+		/** @var BiomeArray|null $biomeArray */
-		$biomeIds = "";
+		$biomeArray = null;
 
 		$chunkVersion = ord($this->db->get($index . self::TAG_VERSION));
 		$hasBeenUpgraded = $chunkVersion < self::CURRENT_LEVEL_CHUNK_VERSION;
@@ -326,7 +327,7 @@ class LevelDB extends BaseWorldProvider implements WritableWorldProvider{
 
 					try{
 						$binaryStream->get(512); //heightmap, discard it
-						$biomeIds = $binaryStream->get(256);
+						$biomeArray = new BiomeArray($binaryStream->get(256)); //never throws
 					}catch(BinaryDataException $e){
 						throw new CorruptedChunkException($e->getMessage(), 0, $e);
 					}
@@ -360,7 +361,7 @@ class LevelDB extends BaseWorldProvider implements WritableWorldProvider{
 
 				try{
 					$binaryStream->get(256); //heightmap, discard it
-					$biomeIds = ChunkUtils::convertBiomeColors(array_values(unpack("N*", $binaryStream->get(1024))));
+					$biomeArray = new BiomeArray(ChunkUtils::convertBiomeColors(array_values(unpack("N*", $binaryStream->get(1024))))); //never throws
 				}catch(BinaryDataException $e){
 					throw new CorruptedChunkException($e->getMessage(), 0, $e);
 				}
@@ -398,7 +399,7 @@ class LevelDB extends BaseWorldProvider implements WritableWorldProvider{
 			$subChunks,
 			$entities,
 			$tiles,
-			$biomeIds
+			$biomeArray
 		);
 
 		//TODO: tile ticks, biome states (?)

src/world/format/io/region/LegacyAnvilChunkTrait.php

@@ -25,9 +25,11 @@ namespace pocketmine\world\format\io\region;
 
 use pocketmine\nbt\BigEndianNbtSerializer;
 use pocketmine\nbt\NbtDataException;
+use pocketmine\nbt\tag\ByteArrayTag;
 use pocketmine\nbt\tag\CompoundTag;
 use pocketmine\nbt\tag\IntArrayTag;
 use pocketmine\nbt\tag\ListTag;
+use pocketmine\world\format\BiomeArray;
 use pocketmine\world\format\Chunk;
 use pocketmine\world\format\io\ChunkUtils;
 use pocketmine\world\format\io\exception\CorruptedChunkException;
@@ -72,10 +74,18 @@ trait LegacyAnvilChunkTrait{
 			}
 		}
 
+		$makeBiomeArray = function(string $biomeIds) : BiomeArray{
+			try{
+				return new BiomeArray($biomeIds);
+			}catch(\InvalidArgumentException $e){
+				throw new CorruptedChunkException($e->getMessage(), 0, $e);
+			}
+		};
+		$biomeArray = null;
 		if($chunk->hasTag("BiomeColors", IntArrayTag::class)){
-			$biomeIds = ChunkUtils::convertBiomeColors($chunk->getIntArray("BiomeColors")); //Convert back to original format
+			$biomeArray = $makeBiomeArray(ChunkUtils::convertBiomeColors($chunk->getIntArray("BiomeColors"))); //Convert back to original format
-		}else{
+		}elseif($chunk->hasTag("Biomes", ByteArrayTag::class)){
-			$biomeIds = $chunk->getByteArray("Biomes", "");
+			$biomeArray = $makeBiomeArray($chunk->getByteArray("Biomes"));
 		}
 
 		$result = new Chunk(
@@ -84,7 +94,7 @@ trait LegacyAnvilChunkTrait{
 			$subChunks,
 			$chunk->hasTag("Entities", ListTag::class) ? self::getCompoundList("Entities", $chunk->getListTag("Entities")) : [],
 			$chunk->hasTag("TileEntities", ListTag::class) ? self::getCompoundList("TileEntities", $chunk->getListTag("TileEntities")) : [],
-			$biomeIds
+			$biomeArray
 		);
 		$result->setPopulated($chunk->getByte("TerrainPopulated", 0) !== 0);
 		$result->setGenerated();

src/world/format/io/region/McRegion.php

@@ -29,6 +29,7 @@ use pocketmine\nbt\NbtDataException;
 use pocketmine\nbt\tag\ByteArrayTag;
 use pocketmine\nbt\tag\IntArrayTag;
 use pocketmine\nbt\tag\ListTag;
+use pocketmine\world\format\BiomeArray;
 use pocketmine\world\format\Chunk;
 use pocketmine\world\format\io\ChunkUtils;
 use pocketmine\world\format\io\exception\CorruptedChunkException;
@@ -69,12 +70,18 @@ class McRegion extends RegionWorldProvider{
 			$subChunks[$y] = new SubChunk(BlockLegacyIds::AIR << 4, [SubChunkConverter::convertSubChunkFromLegacyColumn($fullIds, $fullData, $y)]);
 		}
 
+		$makeBiomeArray = function(string $biomeIds) : BiomeArray{
+			try{
+				return new BiomeArray($biomeIds);
+			}catch(\InvalidArgumentException $e){
+				throw new CorruptedChunkException($e->getMessage(), 0, $e);
+			}
+		};
+		$biomeIds = null;
 		if($chunk->hasTag("BiomeColors", IntArrayTag::class)){
-			$biomeIds = ChunkUtils::convertBiomeColors($chunk->getIntArray("BiomeColors")); //Convert back to original format
+			$biomeIds = $makeBiomeArray(ChunkUtils::convertBiomeColors($chunk->getIntArray("BiomeColors"))); //Convert back to original format
 		}elseif($chunk->hasTag("Biomes", ByteArrayTag::class)){
-			$biomeIds = $chunk->getByteArray("Biomes");
+			$biomeIds = $makeBiomeArray($chunk->getByteArray("Biomes"));
-		}else{
-			$biomeIds = "";
 		}
 
 		$result = new Chunk(