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<?php
/*
* This file is part of the Symfony package.
*
* (c) Fabien Potencier <fabien@symfony.com>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace Symfony\Component\Lock\Store;
use Symfony\Component\Lock\Exception\InvalidArgumentException;
use Symfony\Component\Lock\Exception\LockConflictedException;
use Symfony\Component\Lock\Key;
use Symfony\Component\Lock\StoreInterface;
/**
* SemaphoreStore is a StoreInterface implementation using Semaphore as store engine.
*
* @author Jérémy Derussé <jeremy@derusse.com>
*/
class SemaphoreStore implements StoreInterface
{
/**
* Returns whether or not the store is supported.
*
* @return bool
*
* @internal
*/
public static function isSupported()
{
return \extension_loaded('sysvsem');
}
public function __construct()
{
if (!static::isSupported()) {
throw new InvalidArgumentException('Semaphore extension (sysvsem) is required');
}
}
/**
* {@inheritdoc}
*/
public function save(Key $key)
{
$this->lock($key, false);
}
/**
* {@inheritdoc}
*/
public function waitAndSave(Key $key)
{
$this->lock($key, true);
}
private function lock(Key $key, $blocking)
{
if ($key->hasState(__CLASS__)) {
return;
}
$keyId = crc32($key);
$resource = sem_get($keyId);
$acquired = @sem_acquire($resource, !$blocking);
while ($blocking && !$acquired) {
$resource = sem_get($keyId);
$acquired = @sem_acquire($resource);
}
if (!$acquired) {
throw new LockConflictedException();
}
$key->setState(__CLASS__, $resource);
}
/**
* {@inheritdoc}
*/
public function delete(Key $key)
{
// The lock is maybe not acquired.
if (!$key->hasState(__CLASS__)) {
return;
}
$resource = $key->getState(__CLASS__);
sem_remove($resource);
$key->removeState(__CLASS__);
}
/**
* {@inheritdoc}
*/
public function putOffExpiration(Key $key, $ttl)
{
// do nothing, the semaphore locks forever.
}
/**
* {@inheritdoc}
*/
public function exists(Key $key)
{
return $key->hasState(__CLASS__);
}
}
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