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<?php
/*
* 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!
*/
namespace TYPO3\CMS\Core\Locking;
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;
/**
* Semaphore locking
*/
class SemaphoreLockStrategy implements LockingStrategyInterface
{
use BlockSerializationTrait;
public const FILE_LOCK_FOLDER = 'lock/';
public const DEFAULT_PRIORITY = 25;
/**
* @var int Identifier used for this lock
*/
protected $id;
/**
* @var resource|\SysvSemaphore|null Semaphore Resource used for this lock
*/
protected $resource;
/**
* @var string
*/
protected $filePath = '';
/**
* @var bool TRUE if lock is acquired
*/
protected $isAcquired = false;
/**
* @param string $subject ID to identify this lock in the system
* @throws LockCreateException
*/
public function __construct($subject)
{
/*
* Tests if the directory for semaphore locks is available.
* If not, the directory will be created. The lock path is usually
* below typo3temp/var, typo3temp/var itself should exist already (or root-path/var/ respectively)
*/
if ($GLOBALS['TYPO3_CONF_VARS']['SYS']['locking']['strategies'][self::class]['lockFileDir'] ?? false) {
$path = Environment::getProjectPath() . '/'
. trim($GLOBALS['TYPO3_CONF_VARS']['SYS']['locking']['strategies'][self::class]['lockFileDir'], ' /')
. '/';
} else {
$path = Environment::getVarPath() . '/' . self::FILE_LOCK_FOLDER;
}
if (!is_dir($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 === -1) {
throw new LockCreateException('Cannot create key for semaphore using path ' . $this->filePath, 1396278734);
}
}
/**
* Destructor
*/
public function __destruct()
{
$this->release();
// We do not call sem_remove() since this would remove the resource for other processes,
// we leave that to the system. This is not clean, but there's no other way to determine when
// a semaphore is no longer needed as a website is generally running endlessly
// and we have no way to detect if there is a process currently waiting on that lock
// or if the server is shutdown
}
/**
* Release the lock
*
* @return bool Returns TRUE on success or FALSE on failure
*/
public function release()
{
if (!$this->isAcquired) {
return true;
}
$this->isAcquired = false;
return (bool)@sem_release($this->resource);
}
/**
* Get status of this lock
*
* @return bool Returns TRUE if lock is acquired by this locker, FALSE otherwise
*/
public function isAcquired()
{
return $this->isAcquired;
}
/**
* @return int LOCK_CAPABILITY_* elements combined with bit-wise OR
*/
public static function getCapabilities()
{
if (function_exists('sem_get')) {
return self::LOCK_CAPABILITY_EXCLUSIVE;
}
return 0;
}
/**
* Try to acquire a lock
*
* @param int $mode LOCK_CAPABILITY_EXCLUSIVE
* @return bool Returns TRUE if the lock was acquired successfully
* @throws LockAcquireException if a semaphore could not be retrieved
*/
public function acquire($mode = self::LOCK_CAPABILITY_EXCLUSIVE)
{
if ($this->isAcquired) {
return true;
}
$resource = sem_get($this->id, 1);
if ($resource === false) {
throw new LockAcquireException('Unable to get semaphore with id ' . $this->id, 1313828196);
}
$this->resource = $resource;
$this->isAcquired = (bool)sem_acquire($this->resource);
return $this->isAcquired;
}
/**
* @return int Returns a priority for the method. 0 to 100, 100 is highest
*/
public static function getPriority()
{
return $GLOBALS['TYPO3_CONF_VARS']['SYS']['locking']['strategies'][self::class]['priority']
?? self::DEFAULT_PRIORITY;
}
/**
* Destroys the resource associated with the lock
*/
public function destroy()
{
if ($this->resource) {
sem_remove($this->resource);
@unlink($this->filePath);
}
}
}