BitSet.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\serializer;
 
use function array_pad;
use function array_slice;
use function array_values;
use function count;
use function intdiv;
 
class BitSet{
    private const INT_BITS = PHP_INT_SIZE * 8;
    private const SHIFT = 7;
 
    public function __construct(
        private readonly int $length,
        private array $parts = []
    ){
        $expectedPartsCount = self::getExpectedPartsCount($length);
        $partsCount = count($parts);
 
        if($partsCount > $expectedPartsCount){
            throw new \InvalidArgumentException("Too many parts");
        }elseif($partsCount < $expectedPartsCount){
            $parts = array_pad($parts, $expectedPartsCount, 0);
        }
 
        $this->parts = array_values($parts);
    }
 
    public function get(int $index) : bool{
        [$partIndex, $bitIndex] = $this->getPartIndex($index);
 
        return ($this->parts[$partIndex] & (1 << $bitIndex)) !== 0;
    }
 
    public function set(int $index, bool $value) : void{
        [$partIndex, $bitIndex] = $this->getPartIndex($index);
 
        if($value){
            $this->parts[$partIndex] |= 1 << $bitIndex;
        }else{
            $this->parts[$partIndex] &= ~(1 << $bitIndex);
        }
    }
 
    private function getPartIndex(int $index) : array{
        if($index < 0 or $index >= $this->length){
            throw new \InvalidArgumentException("Index out of bounds");
        }
 
        return [
            intdiv($index, self::INT_BITS),
            $index % self::INT_BITS
        ];
    }
 
    public function getPartsCount() : int{
        return count($this->parts);
    }
 
    private static function getExpectedPartsCount(int $length) : int{
        return intdiv($length + self::INT_BITS - 1, self::INT_BITS);
    }
 
    public static function read(PacketSerializer $in, int $length) : self{
        $result = [0];
 
        $currentIndex = 0;
        $currentShift = 0;
 
        for($i = 0; $i < $length; $i += self::SHIFT){
            $b = $in->getByte();
            $bits = $b & 0x7f;
 
            $result[$currentIndex] |= $bits << $currentShift; //extra bits will be discarded
            $nextShift = $currentShift + self::SHIFT;
            if($nextShift >= self::INT_BITS){
                $nextShift -= self::INT_BITS;
                $rightShift = self::SHIFT - $nextShift;
                $result[++$currentIndex] = $bits >> $rightShift;
            }
            $currentShift = $nextShift;
 
            if(($b & 0x80) === 0){
                return new self($length, array_slice($result, 0, self::getExpectedPartsCount($length)));
            }
        }
 
        return new self($length, array_slice($result, 0, self::getExpectedPartsCount($length)));
    }
 
    public function write(PacketSerializer $out) : void{
        $parts = $this->parts;
        $length = $this->length;
 
        $currentIndex = 0;
        $currentShift = 0;
 
        for($i = 0; $i < $length; $i += self::SHIFT){
            $bits = $parts[$currentIndex] >> $currentShift;
            $nextShift = $currentShift + self::SHIFT;
            if($nextShift >= self::INT_BITS){
                $nextShift -= self::INT_BITS;
                $bits |= ($parts[++$currentIndex] ?? 0) << (self::SHIFT - $nextShift);
            }
            $currentShift = $nextShift;
 
            $last = $i + self::SHIFT >= $length;
            $bits |= $last ? 0 : 0x80;
 
            $out->putByte($bits);
            if($last){
                break;
            }
        }
    }
 
    public function getLength() : int{
        return $this->length;
    }
}