nc-music / music

lib/Utility/Concurrency.php

<?php declare(strict_types=1);


/**

 * ownCloud - Music app

 *

 * This file is licensed under the Affero General Public License version 3 or

 * later. See the COPYING file.

 *

 * @author Pauli Järvinen <pauli.jarvinen@gmail.com>

 * @copyright Pauli Järvinen 2026

 */


namespace OCA\Music\Utility;


use OCA\Music\AppFramework\Core\Logger;

use OCA\Music\Db\Cache;


class Concurrency {

	private const SEMAPHORE_KEY_BASE = 0xa5e63947; // arbitrarily selected 32-bit base value


	public function __construct(private Cache $cache, private Logger $logger) {

	}


	public function mutexReserve(string $userId, string $key) : false|\SysvSemaphore {

		if (!\extension_loaded('sysvsem')) {

			$this->logger->warning('PHP extension sysvsem should be installed to guarantee correct behavior');

			return false;

		}


		$mutexKey = self::SEMAPHORE_KEY_BASE + $this->cache->forcedGetId($userId, "mutex_key.$key");

		$mutex = \sem_get($mutexKey);


		if ($mutex !== false) {

			\sem_acquire($mutex);

		} else {

			$this->logger->warning('Failed to acquire the semaphore');

		}


		return $mutex;

The expression return $mutex could return the type resource which is incompatible with the type-hinted return SysvSemaphore|false. Consider adding an additional type-check to rule them out.

	}


	public function mutexRelease(false|\SysvSemaphore $mutex) : void {

		if ($mutex !== false) {

			\sem_release($mutex);

		}

	}

}