extracted a HeightArray type from Chunk

src/world/format/Chunk.php

@@ -81,10 +81,7 @@ class Chunk{
 	/** @var Entity[] */
 	protected $entities = [];
 
-	/**
+	/** @var HeightArray */
-	 * @var \SplFixedArray|int[]
-	 * @phpstan-var \SplFixedArray<int>
-	 */
 	protected $heightMap;
 
 	/** @var BiomeArray */
@@ -100,9 +97,8 @@ class Chunk{
 	 * @param SubChunk[]    $subChunks
 	 * @param CompoundTag[] $entities
 	 * @param CompoundTag[] $tiles
-	 * @param int[]         $heightMap
 	 */
-	public function __construct(int $chunkX, int $chunkZ, array $subChunks = [], ?array $entities = null, ?array $tiles = null, ?BiomeArray $biomeIds = null, array $heightMap = []){
+	public function __construct(int $chunkX, int $chunkZ, array $subChunks = [], ?array $entities = null, ?array $tiles = null, ?BiomeArray $biomeIds = null, ?HeightArray $heightMap = null){
 		$this->x = $chunkX;
 		$this->z = $chunkZ;
 
@@ -112,14 +108,8 @@ class Chunk{
 			$this->subChunks[$y] = $subChunks[$y] ?? new SubChunk(BlockLegacyIds::AIR << 4, []);
 		}
 
-		if(count($heightMap) === 256){
+		$val = ($this->subChunks->getSize() * 16);
-			$this->heightMap = \SplFixedArray::fromArray($heightMap);
+		$this->heightMap = $heightMap ?? new HeightArray(array_fill(0, 256, $val));
-		}else{
-			assert(count($heightMap) === 0, "Wrong HeightMap value count, expected 256, got " . count($heightMap));
-			$val = ($this->subChunks->getSize() * 16);
-			$this->heightMap = \SplFixedArray::fromArray(array_fill(0, 256, $val));
-		}
-
 		$this->biomeIds = $biomeIds ?? new BiomeArray(str_repeat("\x00", 256));
 
 		$this->NBTtiles = $tiles;
@@ -258,7 +248,7 @@ class Chunk{
 	 * @param int $z 0-15
 	 */
 	public function getHeightMap(int $x, int $z) : int{
-		return $this->heightMap[($z << 4) | $x];
+		return $this->heightMap->get($x, $z);
 	}
 
 	/**
@@ -268,7 +258,7 @@ class Chunk{
 	 * @param int $z 0-15
 	 */
 	public function setHeightMap(int $x, int $z, int $value) : void{
-		$this->heightMap[($z << 4) | $x] = $value;
+		$this->heightMap->set($x, $z, $value);
 	}
 
 	/**
@@ -552,18 +542,14 @@ class Chunk{
 	 * @return int[]
 	 */
 	public function getHeightMapArray() : array{
-		return $this->heightMap->toArray();
+		return $this->heightMap->getValues();
 	}
 
 	/**
 	 * @param int[] $values
-	 * @throws \InvalidArgumentException
 	 */
 	public function setHeightMapArray(array $values) : void{
-		if(count($values) !== 256){
+		$this->heightMap = new HeightArray($values);
-			throw new \InvalidArgumentException("Expected exactly 256 values");
-		}
-		$this->heightMap = \SplFixedArray::fromArray($values);
 	}
 
 	public function isDirty() : bool{

src/world/format/HeightArray.php

@@ -0,0 +1,73 @@
+<?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 count;
+
+final class HeightArray{
+
+	/**
+	 * @var \SplFixedArray|int[]
+	 * @phpstan-var \SplFixedArray<int>
+	 */
+	private $array;
+
+	/**
+	 * @param int[] $values ZZZZXXXX key bit order
+	 * @phpstan-param list<int> $values
+	 */
+	public function __construct(array $values){
+		if(count($values) !== 256){
+			throw new \InvalidArgumentException("Expected exactly 256 values");
+		}
+		$this->array = \SplFixedArray::fromArray($values);
+	}
+
+	private static function idx(int $x, int $z) : int{
+		if($x < 0 or $x >= 16 or $z < 0 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 $this->array[self::idx($x, $z)];
+	}
+
+	public function set(int $x, int $z, int $height) : void{
+		$this->array[self::idx($x, $z)] = $height;
+	}
+
+	/**
+	 * @return int[] ZZZZXXXX key bit order
+	 * @phpstan-return list<int>
+	 */
+	public function getValues() : array{
+		return $this->array->toArray();
+	}
+
+	public function __clone(){
+		$this->array = clone $this->array;
+	}
+}

src/world/format/io/FastChunkSerializer.php

@@ -27,6 +27,7 @@ use pocketmine\block\BlockLegacyIds;
 use pocketmine\utils\BinaryStream;
 use pocketmine\world\format\BiomeArray;
 use pocketmine\world\format\Chunk;
+use pocketmine\world\format\HeightArray;
 use pocketmine\world\format\LightArray;
 use pocketmine\world\format\PalettedBlockArray;
 use pocketmine\world\format\SubChunk;
@@ -120,7 +121,7 @@ final class FastChunkSerializer{
 
 		$subChunks = [];
 		$biomeIds = null;
-		$heightMap = [];
+		$heightMap = null;
 		if($terrainGenerated){
 			$count = $stream->getByte();
 			for($subCount = 0; $subCount < $count; ++$subCount){
@@ -142,7 +143,7 @@ final class FastChunkSerializer{
 
 			$biomeIds = new BiomeArray($stream->get(256));
 			if($lightPopulated){
-				$heightMap = array_values(unpack("S*", $stream->get(512)));
+				$heightMap = new HeightArray(array_values(unpack("S*", $stream->get(512))));
 			}
 		}