Server: Removed identifiers array

This is completely unnecessary and adds extra complexity for no good reason. Maybe it was used historically, but nowadays it is only used to identify players to send async-prepared batch packets to.

There are two alternative ways to do that:
1. use spl_object_hash() as the targets array in CompressBatchedTask
2. use ServerScheduler's object storage to retain references to the Player[] array.

I've opted for the second method.

Removing these identifiers allows great code simplification in removePlayer() and removes the need for those old stupid hacks.

This also includes a backwards-compatibility break by removing the $identifier parameter of Server->addPlayer().

src/pocketmine/Server.php

@@ -264,9 +264,6 @@ class Server{
 	/** @var Player[] */
 	private $playerList = [];
 
-	/** @var string[] */
-	private $identifiers = [];
-
 	/** @var Level[] */
 	private $levels = [];
 
@@ -899,20 +896,7 @@ class Server{
 	 * @param Player $player
 	 */
 	public function removePlayer(Player $player){
-		if(isset($this->identifiers[$hash = spl_object_hash($player)])){
-			$identifier = $this->identifiers[$hash];
-			unset($this->players[$identifier]);
-			unset($this->identifiers[$hash]);
-			return;
-		}
-
-		foreach($this->players as $identifier => $p){
-			if($player === $p){
-				unset($this->players[$identifier]);
-				unset($this->identifiers[spl_object_hash($player)]);
-				break;
-			}
-		}
+		unset($this->players[spl_object_hash($player)]);
 	}
 
 	/**
@@ -1899,14 +1883,9 @@ class Server{
 		}
 		Timings::$playerNetworkTimer->startTiming();
 
-		$targets = [];
-		foreach($players as $p){
-			if($p->isConnected()){
-				$targets[] = $this->identifiers[spl_object_hash($p)];
-			}
-		}
+		$targets = array_filter($players, function(Player $player) : bool{ return $player->isConnected(); });
 
-		if(count($targets) > 0){
+		if(!empty($targets)){
 			$pk = new BatchPacket();
 
 			foreach($packets as $p){
@@ -1931,17 +1910,19 @@ class Server{
 		Timings::$playerNetworkTimer->stopTiming();
 	}
 
-	public function broadcastPacketsCallback(BatchPacket $pk, array $identifiers, bool $immediate = false){
+	/**
+	 * @param BatchPacket $pk
+	 * @param Player[]    $players
+	 * @param bool        $immediate
+	 */
+	public function broadcastPacketsCallback(BatchPacket $pk, array $players, bool $immediate = false){
 		if(!$pk->isEncoded){
 			$pk->encode();
 		}
 
-		foreach($identifiers as $i){
-			if(isset($this->players[$i])){
-				$this->players[$i]->sendDataPacket($pk, false, $immediate);
-			}
+		foreach($players as $i){
+			$i->sendDataPacket($pk, false, $immediate);
 		}
-
 	}
 
 
@@ -2317,9 +2298,8 @@ class Server{
 		unset($this->loggedInPlayers[$player->getRawUniqueId()]);
 	}
 
-	public function addPlayer(string $identifier, Player $player){
-		$this->players[$identifier] = $player;
-		$this->identifiers[spl_object_hash($player)] = $identifier;
+	public function addPlayer(Player $player){
+		$this->players[spl_object_hash($player)] = $player;
 	}
 
 	public function addOnlinePlayer(Player $player){

src/pocketmine/network/CompressBatchedTask.php

@@ -24,6 +24,7 @@ declare(strict_types=1);
 namespace pocketmine\network;
 
 use pocketmine\network\mcpe\protocol\BatchPacket;
+use pocketmine\Player;
 use pocketmine\scheduler\AsyncTask;
 use pocketmine\Server;
 
@@ -31,7 +32,6 @@ class CompressBatchedTask extends AsyncTask{
 
 	public $level = 7;
 	public $data;
-	public $targets;
 
 	/**
 	 * @param BatchPacket $batch
@@ -39,8 +39,8 @@ class CompressBatchedTask extends AsyncTask{
 	 */
 	public function __construct(BatchPacket $batch, array $targets){
 		$this->data = $batch->payload;
-		$this->targets = serialize($targets);
 		$this->level = $batch->getCompressionLevel();
+		$this->storeLocal($targets);
 	}
 
 	public function onRun(){
@@ -57,6 +57,10 @@ class CompressBatchedTask extends AsyncTask{
 	public function onCompletion(Server $server){
 		$pk = new BatchPacket($this->getResult());
 		$pk->isEncoded = true;
-		$server->broadcastPacketsCallback($pk, unserialize($this->targets));
+
+		/** @var Player[] $targets */
+		$targets = $this->fetchLocal();
+
+		$server->broadcastPacketsCallback($pk, $targets);
 	}
 }

src/pocketmine/network/mcpe/RakLibInterface.php

@@ -134,7 +134,7 @@ class RakLibInterface implements ServerInstance, AdvancedSourceInterface{
 		$this->players[$identifier] = $player;
 		$this->identifiersACK[$identifier] = 0;
 		$this->identifiers[spl_object_hash($player)] = $identifier;
-		$this->server->addPlayer($identifier, $player);
+		$this->server->addPlayer($player);
 	}
 
 	public function handleEncapsulated(string $identifier, EncapsulatedPacket $packet, int $flags) : void{