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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\LockAcquireWouldBlockException;
use TYPO3\CMS\Core\Locking\Exception\LockCreateException;
use TYPO3\CMS\Core\Security\BlockSerializationTrait;
use TYPO3\CMS\Core\Utility\GeneralUtility;
/**
* flock() locking
*/
class FileLockStrategy implements LockingStrategyInterface
{
use BlockSerializationTrait;
public const FILE_LOCK_FOLDER = 'lock/';
public const DEFAULT_PRIORITY = 75;
/**
* @var resource File pointer if using flock method
*/
protected $filePointer;
/**
* @var string File used for locking
*/
protected $filePath;
/**
* @var bool True if lock is acquired
*/
protected $isAcquired = false;
/**
* @param string $subject ID to identify this lock in the system
* @throws LockCreateException if the lock could not be created
*/
public function __construct($subject)
{
/*
* Tests if the directory for file 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 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 ' . $path, 1395140007);
}
}
if (!is_writable($path)) {
throw new LockCreateException('Cannot write to directory ' . $path, 1396278700);
}
$this->filePath = $path . 'flock_' . md5((string)$subject);
}
/**
* Destructor:
* Releases lock automatically when instance is destroyed and release resources
*/
public function __destruct()
{
$this->release();
}
/**
* Try to acquire an exclusive lock
*
* @param int $mode LOCK_CAPABILITY_EXCLUSIVE or LOCK_CAPABILITY_SHARED or self::LOCK_CAPABILITY_NOBLOCK
* @return bool Returns TRUE if the lock was acquired successfully
* @throws LockAcquireException if the lock could not be acquired
* @throws LockAcquireWouldBlockException if the acquire would have blocked and NOBLOCK was set
*/
public function acquire($mode = self::LOCK_CAPABILITY_EXCLUSIVE)
{
if ($this->isAcquired) {
return true;
}
$filePointer = fopen($this->filePath, 'c');
if ($filePointer === false) {
throw new LockAcquireException('Lock file could not be opened', 1294586099);
}
$this->filePointer = $filePointer;
GeneralUtility::fixPermissions($this->filePath);
$operation = $mode & self::LOCK_CAPABILITY_EXCLUSIVE ? LOCK_EX : LOCK_SH;
if ($mode & self::LOCK_CAPABILITY_NOBLOCK) {
$operation |= LOCK_NB;
}
$wouldBlock = 0;
$this->isAcquired = flock($this->filePointer, $operation, $wouldBlock);
if (!$this->isAcquired) {
// Make sure to cleanup any dangling resources for this process/thread, which are not needed any longer
fclose($this->filePointer);
}
if ($mode & self::LOCK_CAPABILITY_NOBLOCK && !$this->isAcquired && $wouldBlock) {
throw new LockAcquireWouldBlockException('Failed to acquire lock because the request would block.', 1428700748);
}
return $this->isAcquired;
}
/**
* Release the lock
*
* @return bool Returns TRUE on success or FALSE on failure
*/
public function release()
{
if (!$this->isAcquired) {
return true;
}
$success = true;
if (is_resource($this->filePointer)) {
if (flock($this->filePointer, LOCK_UN) === false) {
$success = false;
}
fclose($this->filePointer);
}
$this->isAcquired = false;
return $success;
}
/**
* 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 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;
}
/**
* @return int LOCK_CAPABILITY_* elements combined with bit-wise OR
*/
public static function getCapabilities()
{
if (PHP_SAPI === 'isapi') {
// From php docs: When using a multi-threaded server API like ISAPI you may not be able to rely on flock()
// to protect files against other PHP scripts running in parallel threads of the same server instance!
return 0;
}
$capabilities = self::LOCK_CAPABILITY_EXCLUSIVE | self::LOCK_CAPABILITY_SHARED | self::LOCK_CAPABILITY_NOBLOCK;
return $capabilities;
}
/**
* Destroys the resource associated with the lock
*/
public function destroy()
{
@unlink($this->filePath);
}
}