9.5/_semaphore_lock_strategy_8php_source.html

<?php

namespace ‪TYPO3\CMS\Core\Locking;


/*

 * This file is part of the TYPO3 CMS project.

 *

 * It is free software; you can redistribute it and/or modify it under

 * the terms of the GNU General Public License, either version 2

 * of the License, or any later version.

 *

 * For the full copyright and license information, please read the

 * LICENSE.txt file that was distributed with this source code.

 *

 * The TYPO3 project - inspiring people to share!

 */


use ‪TYPO3\CMS\Core\Core\Environment;

use ‪TYPO3\CMS\Core\Locking\Exception\LockAcquireException;

use ‪TYPO3\CMS\Core\Locking\Exception\LockCreateException;

use ‪TYPO3\CMS\Core\Security\BlockSerializationTrait;

use ‪TYPO3\CMS\Core\Utility\GeneralUtility;


class ‪SemaphoreLockStrategy implements ‪LockingStrategyInterface

{

    use ‪BlockSerializationTrait;


    const ‪FILE_LOCK_FOLDER = 'lock/';


    protected ‪$id;


    protected ‪$resource;


    protected ‪$filePath = '';


    protected ‪$isAcquired = false;


    public function ‪__construct($subject)

    {

        $path = ‪Environment::getVarPath() . '/' . ‪self::FILE_LOCK_FOLDER;

        if (!is_dir($path)) {

            // Not using mkdir_deep on purpose here, if typo3temp/var itself

            // does not exist, this issue should be solved on a different

            // level of the application.

            if (!GeneralUtility::mkdir($path)) {

                throw new ‪LockCreateException('Cannot create directory ' . $path, 1460976250);

            }

        }

        if (!is_writable($path)) {

            throw new ‪LockCreateException('Cannot write to directory ' . $path, 1460976320);

        }

        $this->filePath = $path . 'sem_' . md5((string)$subject);

        touch($this->filePath);

        $this->id = ftok($this->filePath, 'A');

        if ($this->id === false) {

            throw new ‪LockCreateException('Cannot create key for semaphore using path ' . $this->filePath, 1396278734);

        }

    }


    public function ‪__destruct()

    {

        $this->‪release();

        // We do not call sem_remove() since this would remove the resource for other processes,

        // we leave that to the system. This is not clean, but there's no other way to determine when

        // a semaphore is no longer needed as a website is generally running endlessly

        // and we have no way to detect if there is a process currently waiting on that lock

        // or if the server is shutdown

    }


    public function ‪release()

    {

        if (!$this->‪isAcquired) {

            return true;

        }

        $this->‪isAcquired = false;

        return (bool)@sem_release($this->resource);

    }


    public function ‪isAcquired()

    {

        return ‪$this->isAcquired;

    }


    public static function ‪getCapabilities()

    {

        if (function_exists('sem_get')) {

            return ‪self::LOCK_CAPABILITY_EXCLUSIVE;

        }

        return 0;

    }


    public function ‪acquire($mode = self::LOCK_CAPABILITY_EXCLUSIVE)

    {

        if ($this->‪isAcquired) {

            return true;

        }


        $this->resource = sem_get($this->id, 1);

        if ($this->resource === false) {

            throw new LockAcquireException('Unable to get semaphore with id ' . $this->id, 1313828196);

        }


        $this->‪isAcquired = (bool)sem_acquire($this->resource);

        return ‪$this->isAcquired;

    }


    public static function ‪getPriority()

    {

        return 25;

    }


    public function ‪destroy()

    {

        if ($this->resource) {

            sem_remove($this->resource);

            @unlink($this->filePath);

        }

    }

}