From cdab3e967a36cb85ef10b91c3a39369e077164d4 Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <odigiman@gmail.com>
Date: Mon, 8 Jul 2019 14:37:48 +0100
Subject: [PATCH] Extract a LightArray unit from SubChunk

---
 src/pocketmine/world/format/Chunk.php         |  4 +-
 src/pocketmine/world/format/EmptySubChunk.php | 12 +--
 src/pocketmine/world/format/LightArray.php    | 85 +++++++++++++++++++
 src/pocketmine/world/format/SubChunk.php      | 84 +++++-------------
 .../world/format/SubChunkInterface.php        | 16 ++--
 .../world/format/io/FastChunkSerializer.php   |  7 +-
 6 files changed, 124 insertions(+), 84 deletions(-)
 create mode 100644 src/pocketmine/world/format/LightArray.php

diff --git a/src/pocketmine/world/format/Chunk.php b/src/pocketmine/world/format/Chunk.php
index e6b2c2e6c..a0851eafb 100644
--- a/src/pocketmine/world/format/Chunk.php
+++ b/src/pocketmine/world/format/Chunk.php
@@ -224,7 +224,7 @@ class Chunk{
 		$char = chr(($level & 0x0f) | ($level << 4));
 		$data = str_repeat($char, 2048);
 		for($y = $this->getHighestSubChunkIndex(); $y >= 0; --$y){
-			$this->getSubChunk($y, true)->setBlockSkyLightArray($data);
+			$this->getSubChunk($y, true)->setBlockSkyLightArray(new LightArray($data));
 		}
 	}
 
@@ -260,7 +260,7 @@ class Chunk{
 		$char = chr(($level & 0x0f) | ($level << 4));
 		$data = str_repeat($char, 2048);
 		for($y = $this->getHighestSubChunkIndex(); $y >= 0; --$y){
-			$this->getSubChunk($y, true)->setBlockLightArray($data);
+			$this->getSubChunk($y, true)->setBlockLightArray(new LightArray($data));
 		}
 	}
 
diff --git a/src/pocketmine/world/format/EmptySubChunk.php b/src/pocketmine/world/format/EmptySubChunk.php
index 8606f1d39..7cc607e87 100644
--- a/src/pocketmine/world/format/EmptySubChunk.php
+++ b/src/pocketmine/world/format/EmptySubChunk.php
@@ -73,19 +73,19 @@ class EmptySubChunk implements SubChunkInterface{
 		return -1;
 	}
 
-	public function getBlockLightArray() : string{
-		return str_repeat("\x00", 2048);
+	public function getBlockLightArray() : LightArray{
+		return new LightArray(str_repeat("\x00", 2048));
 	}
 
-	public function setBlockLightArray(string $data) : void{
+	public function setBlockLightArray(LightArray $data) : void{
 
 	}
 
-	public function getBlockSkyLightArray() : string{
-		return str_repeat("\xff", 2048);
+	public function getBlockSkyLightArray() : LightArray{
+		return new LightArray(str_repeat("\xff", 2048));
 	}
 
-	public function setBlockSkyLightArray(string $data) : void{
+	public function setBlockSkyLightArray(LightArray $data) : void{
 
 	}
 }
diff --git a/src/pocketmine/world/format/LightArray.php b/src/pocketmine/world/format/LightArray.php
new file mode 100644
index 000000000..8822ddc12
--- /dev/null
+++ b/src/pocketmine/world/format/LightArray.php
@@ -0,0 +1,85 @@
+<?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 chr;
+use function define;
+use function defined;
+use function ord;
+use function str_repeat;
+use function strlen;
+
+if(!defined(__NAMESPACE__ . '\ZERO_NIBBLE_ARRAY')){
+	define(__NAMESPACE__ . '\ZERO_NIBBLE_ARRAY', str_repeat("\x00", 2048));
+}
+if(!defined(__NAMESPACE__ . '\FIFTEEN_NIBBLE_ARRAY')){
+	define(__NAMESPACE__ . '\FIFTEEN_NIBBLE_ARRAY', str_repeat("\xff", 2048));
+}
+
+final class LightArray{
+
+	public const ZERO = ZERO_NIBBLE_ARRAY;
+	public const FIFTEEN = FIFTEEN_NIBBLE_ARRAY;
+
+	/** @var string */
+	private $data;
+
+	public function __construct(?string $payload){
+		if($payload !== null and ($len = strlen($payload)) !== 2048){
+			throw new \InvalidArgumentException("Payload size must be 2048 bytes, but got $len bytes");
+		}
+
+		$this->data = $payload ?? self::ZERO;
+		$this->collectGarbage();
+	}
+
+	public function get(int $x, int $y, int $z) : int{
+		return (ord($this->data{($x << 7) | ($z << 3) | ($y >> 1)}) >> (($y & 1) << 2)) & 0xf;
+	}
+
+	public function set(int $x, int $y, int $z, int $level) : void{
+		$i = ($x << 7) | ($z << 3) | ($y >> 1);
+
+		$shift = ($y & 1) << 2;
+		$byte = ord($this->data{$i});
+		$this->data{$i} = chr(($byte & ~(0xf << $shift)) | (($level & 0xf) << $shift));
+	}
+
+	public function collectGarbage() : void{
+		/*
+		 * This strange looking code is designed to exploit PHP's copy-on-write behaviour. Assigning will copy a
+		 * reference to the const instead of duplicating the whole string. The string will only be duplicated when
+		 * modified, which is perfect for this purpose.
+		 */
+		if($this->data === ZERO_NIBBLE_ARRAY){
+			$this->data = ZERO_NIBBLE_ARRAY;
+		}elseif($this->data === FIFTEEN_NIBBLE_ARRAY){
+			$this->data = FIFTEEN_NIBBLE_ARRAY;
+		}
+	}
+
+	public function getData() : string{
+		return $this->data;
+	}
+}
diff --git a/src/pocketmine/world/format/SubChunk.php b/src/pocketmine/world/format/SubChunk.php
index e9c132145..19021fd77 100644
--- a/src/pocketmine/world/format/SubChunk.php
+++ b/src/pocketmine/world/format/SubChunk.php
@@ -25,53 +25,28 @@ namespace pocketmine\world\format;
 
 use pocketmine\block\BlockLegacyIds;
 use function array_values;
-use function assert;
-use function chr;
-use function define;
-use function defined;
-use function ord;
-use function str_repeat;
-use function strlen;
-
-if(!defined(__NAMESPACE__ . '\ZERO_NIBBLE_ARRAY')){
-	define(__NAMESPACE__ . '\ZERO_NIBBLE_ARRAY', str_repeat("\x00", 2048));
-}
-if(!defined(__NAMESPACE__ . '\FIFTEEN_NIBBLE_ARRAY')){
-	define(__NAMESPACE__ . '\FIFTEEN_NIBBLE_ARRAY', str_repeat("\xff", 2048));
-}
 
 class SubChunk implements SubChunkInterface{
 	/** @var PalettedBlockArray[] */
 	private $blockLayers;
 
-	/** @var string */
+	/** @var LightArray */
 	protected $blockLight;
-	/** @var string */
+	/** @var LightArray */
 	protected $skyLight;
 
-	private static function assignData(&$target, string $data, string $default) : void{
-		if($data === "" or $data === $default){
-			$target = $default;
-		}elseif(strlen($data) !== 2048){
-			assert(false, "Invalid length given, expected 2048, got " . strlen($data));
-			$target = $default;
-		}else{
-			$target = $data;
-		}
-	}
-
 	/**
 	 * SubChunk constructor.
 	 *
 	 * @param PalettedBlockArray[] $blocks
-	 * @param string               $skyLight
-	 * @param string               $blockLight
+	 * @param LightArray|null      $skyLight
+	 * @param LightArray|null      $blockLight
 	 */
-	public function __construct(array $blocks, string $skyLight = "", string $blockLight = ""){
+	public function __construct(array $blocks, ?LightArray $skyLight = null, ?LightArray $blockLight = null){
 		$this->blockLayers = $blocks;
 
-		self::assignData($this->skyLight, $skyLight, FIFTEEN_NIBBLE_ARRAY);
-		self::assignData($this->blockLight, $blockLight, ZERO_NIBBLE_ARRAY);
+		$this->skyLight = $skyLight ?? new LightArray(LightArray::FIFTEEN);
+		$this->blockLight = $blockLight ?? new LightArray(LightArray::ZERO);
 	}
 
 	public function isEmpty(bool $checkLight = true) : bool{
@@ -85,8 +60,8 @@ class SubChunk implements SubChunkInterface{
 		}
 		return
 			(!$checkLight or (
-				$this->skyLight === FIFTEEN_NIBBLE_ARRAY and
-				$this->blockLight === ZERO_NIBBLE_ARRAY
+				$this->skyLight->getData() === LightArray::FIFTEEN and
+				$this->blockLight->getData() === LightArray::ZERO
 			)
 		);
 	}
@@ -113,29 +88,21 @@ class SubChunk implements SubChunkInterface{
 	}
 
 	public function getBlockLight(int $x, int $y, int $z) : int{
-		return (ord($this->blockLight{($x << 7) | ($z << 3) | ($y >> 1)}) >> (($y & 1) << 2)) & 0xf;
+		return $this->blockLight->get($x, $y, $z);
 	}
 
 	public function setBlockLight(int $x, int $y, int $z, int $level) : bool{
-		$i = ($x << 7) | ($z << 3) | ($y >> 1);
-
-		$shift = ($y & 1) << 2;
-		$byte = ord($this->blockLight{$i});
-		$this->blockLight{$i} = chr(($byte & ~(0xf << $shift)) | (($level & 0xf) << $shift));
+		$this->blockLight->set($x, $y, $z, $level);
 
 		return true;
 	}
 
 	public function getBlockSkyLight(int $x, int $y, int $z) : int{
-		return (ord($this->skyLight{($x << 7) | ($z << 3) | ($y >> 1)}) >> (($y & 1) << 2)) & 0xf;
+		return $this->skyLight->get($x, $y, $z);
 	}
 
 	public function setBlockSkyLight(int $x, int $y, int $z, int $level) : bool{
-		$i = ($x << 7) | ($z << 3) | ($y >> 1);
-
-		$shift = ($y & 1) << 2;
-		$byte = ord($this->skyLight{$i});
-		$this->skyLight{$i} = chr(($byte & ~(0xf << $shift)) | (($level & 0xf) << $shift));
+		$this->skyLight->set($x, $y, $z, $level);
 
 		return true;
 	}
@@ -153,23 +120,19 @@ class SubChunk implements SubChunkInterface{
 		return -1; //highest block not in this subchunk
 	}
 
-	public function getBlockSkyLightArray() : string{
-		assert(strlen($this->skyLight) === 2048, "Wrong length of skylight array, expecting 2048 bytes, got " . strlen($this->skyLight));
+	public function getBlockSkyLightArray() : LightArray{
 		return $this->skyLight;
 	}
 
-	public function setBlockSkyLightArray(string $data) : void{
-		assert(strlen($data) === 2048, "Wrong length of skylight array, expecting 2048 bytes, got " . strlen($data));
+	public function setBlockSkyLightArray(LightArray $data) : void{
 		$this->skyLight = $data;
 	}
 
-	public function getBlockLightArray() : string{
-		assert(strlen($this->blockLight) === 2048, "Wrong length of light array, expecting 2048 bytes, got " . strlen($this->blockLight));
+	public function getBlockLightArray() : LightArray{
 		return $this->blockLight;
 	}
 
-	public function setBlockLightArray(string $data) : void{
-		assert(strlen($data) === 2048, "Wrong length of light array, expecting 2048 bytes, got " . strlen($data));
+	public function setBlockLightArray(LightArray $data) : void{
 		$this->blockLight = $data;
 	}
 
@@ -190,16 +153,7 @@ class SubChunk implements SubChunkInterface{
 		}
 		$this->blockLayers = array_values($this->blockLayers);
 
-		/*
-		 * This strange looking code is designed to exploit PHP's copy-on-write behaviour. Assigning will copy a
-		 * reference to the const instead of duplicating the whole string. The string will only be duplicated when
-		 * modified, which is perfect for this purpose.
-		 */
-		if($this->skyLight === ZERO_NIBBLE_ARRAY){
-			$this->skyLight = ZERO_NIBBLE_ARRAY;
-		}
-		if($this->blockLight === ZERO_NIBBLE_ARRAY){
-			$this->blockLight = ZERO_NIBBLE_ARRAY;
-		}
+		$this->skyLight->collectGarbage();
+		$this->blockLight->collectGarbage();
 	}
 }
diff --git a/src/pocketmine/world/format/SubChunkInterface.php b/src/pocketmine/world/format/SubChunkInterface.php
index fff078c9b..bb7c5f01d 100644
--- a/src/pocketmine/world/format/SubChunkInterface.php
+++ b/src/pocketmine/world/format/SubChunkInterface.php
@@ -101,22 +101,22 @@ interface SubChunkInterface{
 	public function getHighestBlockAt(int $x, int $z) : int;
 
 	/**
-	 * @return string
+	 * @return LightArray
 	 */
-	public function getBlockSkyLightArray() : string;
+	public function getBlockSkyLightArray() : LightArray;
 
 	/**
-	 * @param string $data
+	 * @param LightArray $data
 	 */
-	public function setBlockSkyLightArray(string $data) : void;
+	public function setBlockSkyLightArray(LightArray $data) : void;
 
 	/**
-	 * @return string
+	 * @return LightArray
 	 */
-	public function getBlockLightArray() : string;
+	public function getBlockLightArray() : LightArray;
 
 	/**
-	 * @param string $data
+	 * @param LightArray $data
 	 */
-	public function setBlockLightArray(string $data) : void;
+	public function setBlockLightArray(LightArray $data) : void;
 }
diff --git a/src/pocketmine/world/format/io/FastChunkSerializer.php b/src/pocketmine/world/format/io/FastChunkSerializer.php
index 670d26afc..a4ab01c5c 100644
--- a/src/pocketmine/world/format/io/FastChunkSerializer.php
+++ b/src/pocketmine/world/format/io/FastChunkSerializer.php
@@ -26,6 +26,7 @@ namespace pocketmine\world\format\io;
 use pocketmine\utils\BinaryStream;
 use pocketmine\world\format\Chunk;
 use pocketmine\world\format\EmptySubChunk;
+use pocketmine\world\format\LightArray;
 use pocketmine\world\format\PalettedBlockArray;
 use pocketmine\world\format\SubChunk;
 use function array_values;
@@ -82,8 +83,8 @@ final class FastChunkSerializer{
 				}
 
 				if($chunk->isLightPopulated()){
-					$subStream->put($subChunk->getBlockSkyLightArray());
-					$subStream->put($subChunk->getBlockLightArray());
+					$subStream->put($subChunk->getBlockSkyLightArray()->getData());
+					$subStream->put($subChunk->getBlockLightArray()->getData());
 				}
 			}
 			$stream->putByte($count);
@@ -134,7 +135,7 @@ final class FastChunkSerializer{
 					$layers[] = PalettedBlockArray::fromData($bitsPerBlock, $words, $palette);
 				}
 				$subChunks[$y] = new SubChunk(
-					$layers, $lightPopulated ? $stream->get(2048) : "", $lightPopulated ? $stream->get(2048) : "" //blocklight
+					$layers, $lightPopulated ? new LightArray($stream->get(2048)) : null, $lightPopulated ? new LightArray($stream->get(2048)) : null
 				);
 			}