DataPacket.php

<?php
 
/*
 * This file is part of BedrockProtocol.
 * Copyright (C) 2014-2022 PocketMine Team <https://github.com/pmmp/BedrockProtocol>
 *
 * BedrockProtocol 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.
 */
 
declare(strict_types=1);
 
namespace pocketmine\network\mcpe\protocol;
 
use pmmp\encoding\ByteBufferReader;
use pmmp\encoding\ByteBufferWriter;
use pmmp\encoding\DataDecodeException;
use pmmp\encoding\VarInt;
use function get_class;
 
abstract class DataPacket implements Packet{
 
    public const NETWORK_ID = 0;
 
    public const PID_MASK = 0x3ff; //10 bits
 
    private const SUBCLIENT_ID_MASK = 0x03; //2 bits
    private const SENDER_SUBCLIENT_ID_SHIFT = 10;
    private const RECIPIENT_SUBCLIENT_ID_SHIFT = 12;
 
    public int $senderSubId = 0;
    public int $recipientSubId = 0;
 
    public function pid() : int{
        return $this::NETWORK_ID;
    }
 
    public function getName() : string{
        return (new \ReflectionClass($this))->getShortName();
    }
 
    public function canBeSentBeforeLogin() : bool{
        return false;
    }
 
    final public function decode(ByteBufferReader $in) : void{
        try{
            $this->decodeHeader($in);
            $this->decodePayload($in);
        }catch(DataDecodeException | PacketDecodeException $e){
            throw PacketDecodeException::wrap($e, $this->getName());
        }
    }
 
    protected function decodeHeader(ByteBufferReader $in) : void{
        $header = VarInt::readUnsignedInt($in);
        $pid = $header & self::PID_MASK;
        if($pid !== static::NETWORK_ID){
            //TODO: this means a logical error in the code, but how to prevent it from happening?
            throw new PacketDecodeException("Expected " . static::NETWORK_ID . " for packet ID, got $pid");
        }
        $this->senderSubId = ($header >> self::SENDER_SUBCLIENT_ID_SHIFT) & self::SUBCLIENT_ID_MASK;
        $this->recipientSubId = ($header >> self::RECIPIENT_SUBCLIENT_ID_SHIFT) & self::SUBCLIENT_ID_MASK;
 
    }
 
    abstract protected function decodePayload(ByteBufferReader $in) : void;
 
    final public function encode(ByteBufferWriter $out) : void{
        $this->encodeHeader($out);
        $this->encodePayload($out);
    }
 
    protected function encodeHeader(ByteBufferWriter $out) : void{
        VarInt::writeUnsignedInt($out,
            static::NETWORK_ID |
            ($this->senderSubId << self::SENDER_SUBCLIENT_ID_SHIFT) |
            ($this->recipientSubId << self::RECIPIENT_SUBCLIENT_ID_SHIFT)
        );
    }
 
    abstract protected function encodePayload(ByteBufferWriter $out) : void;
 
    public function __get($name){
        throw new \Error("Undefined property: " . get_class($this) . "::\$" . $name);
    }
 
    public function __set($name, $value) : void{
        throw new \Error("Undefined property: " . get_class($this) . "::\$" . $name);
    }
}