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<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* Class representing a lock
*
* The methods available for a specific lock type are only known by it's factory.
*
* @package core
* @copyright Damyon Wiese 2013
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
namespace core\lock;
defined('MOODLE_INTERNAL') || die();
/**
* Class representing a lock
*
* The methods available for a specific lock type are only known by it's factory.
*
* @package core
* @category lock
* @copyright Damyon Wiese 2013
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class lock {
/** @var string|int $key A unique key representing a held lock */
protected $key = '';
/** @var lock_factory $factory The factory that generated this lock */
protected $factory;
/** @var bool $released Has this lock been released? If a lock falls out of scope without being released - show a warning. */
protected $released;
/** @var string $caller Where was this called from? Stored for when a warning is shown */
protected $caller = 'unknown';
/**
* Construct a lock containing the unique key required to release it.
* @param mixed $key - The lock key. The type of this is up to the lock_factory being used.
* For file locks this is a file handle. For MySQL this is a string.
* @param lock_factory $factory - The factory that generated this lock.
*/
public function __construct($key, $factory) {
$this->factory = $factory;
$this->key = $key;
$this->released = false;
$caller = debug_backtrace(true, 2)[1];
if ($caller && array_key_exists('file', $caller ) ) {
$this->caller = $caller['file'] . ' on line ' . $caller['line'];
} else if ($caller && array_key_exists('class', $caller)) {
$this->caller = $caller['class'] . $caller['type'] . $caller['function'];
}
}
/**
* Return the unique key representing this lock.
* @return string|int lock key.
*/
public function get_key() {
return $this->key;
}
/**
* Extend the lifetime of this lock. Not supported by all factories.
* @param int $maxlifetime - the new lifetime for the lock (in seconds).
* @return bool
*/
public function extend($maxlifetime = 86400) {
if ($this->factory) {
return $this->factory->extend_lock($this, $maxlifetime);
}
return false;
}
/**
* Release this lock
* @return bool
*/
public function release() {
$this->released = true;
if (empty($this->factory)) {
return false;
}
$result = $this->factory->release_lock($this);
// Release any held references to the factory.
unset($this->factory);
$this->factory = null;
$this->key = '';
return $result;
}
/**
* Print debugging if this lock falls out of scope before being released.
*/
public function __destruct() {
if (!$this->released && defined('PHPUNIT_TEST')) {
$key = $this->key;
$this->release();
throw new \coding_exception("A lock was created but not released at:\n" .
$this->caller . "\n\n" .
" Code should look like:\n\n" .
" \$factory = \core\lock\lock_config::get_lock_factory('type');\n" .
" \$lock = \$factory->get_lock($key);\n" .
" \$lock->release(); // Locks must ALWAYS be released like this.\n\n");
}
}
}