ChunkSelector.php

<?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\player;
 
use pocketmine\world\World;
use const M_SQRT2;
 
//TODO: turn this into an interface?
final class ChunkSelector{
 
    public function selectChunks(int $radius, int $centerX, int $centerZ) : \Generator{
        for($subRadius = 0; $subRadius < $radius; $subRadius++){
            $subRadiusSquared = $subRadius ** 2;
            $nextSubRadiusSquared = ($subRadius + 1) ** 2;
            $minX = (int) ($subRadius / M_SQRT2);
 
            $lastZ = 0;
 
            for($x = $subRadius; $x >= $minX; --$x){
                for($z = $lastZ; $z <= $x; ++$z){
                    $distanceSquared = ($x ** 2 + $z ** 2);
                    if($distanceSquared < $subRadiusSquared){
                        continue;
                    }elseif($distanceSquared >= $nextSubRadiusSquared){
                        break; //skip to next X
                    }
 
                    $lastZ = $z;
                    //If the chunk is in the radius, others at the same offsets in different quadrants are also guaranteed to be.
 
                    /* Top right quadrant */
                    yield $subRadius => World::chunkHash($centerX + $x, $centerZ + $z);
                    /* Top left quadrant */
                    yield $subRadius => World::chunkHash($centerX - $x - 1, $centerZ + $z);
                    /* Bottom right quadrant */
                    yield $subRadius => World::chunkHash($centerX + $x, $centerZ - $z - 1);
                    /* Bottom left quadrant */
                    yield $subRadius => World::chunkHash($centerX - $x - 1, $centerZ - $z - 1);
 
                    if($x !== $z){
                        /* Top right quadrant mirror */
                        yield $subRadius => World::chunkHash($centerX + $z, $centerZ + $x);
                        /* Top left quadrant mirror */
                        yield $subRadius => World::chunkHash($centerX - $z - 1, $centerZ + $x);
                        /* Bottom right quadrant mirror */
                        yield $subRadius => World::chunkHash($centerX + $z, $centerZ - $x - 1);
                        /* Bottom left quadrant mirror */
                        yield $subRadius => World::chunkHash($centerX - $z - 1, $centerZ - $x - 1);
                    }
                }
            }
        }
    }
}