1<?php
2/**
3 * Resource locking handling.
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License along
16 * with this program; if not, write to the Free Software Foundation, Inc.,
17 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
18 * http://www.gnu.org/copyleft/gpl.html
19 *
20 * @file
21 * @ingroup LockManager
22 */
23
24/**
25 * Self-releasing locks
26 *
27 * LockManager helper class to handle scoped locks, which
28 * release when an object is destroyed or goes out of scope.
29 *
30 * @ingroup LockManager
31 * @since 1.19
32 */
33class ScopedLock {
34	/** @var LockManager */
35	protected $manager;
36
37	/** @var StatusValue */
38	protected $status;
39
40	/** @var array Map of lock types to resource paths */
41	protected $pathsByType;
42
43	/**
44	 * @param LockManager $manager
45	 * @param array $pathsByType Map of lock types to path lists
46	 * @param StatusValue $status
47	 */
48	protected function __construct(
49		LockManager $manager, array $pathsByType, StatusValue $status
50	) {
51		$this->manager = $manager;
52		$this->pathsByType = $pathsByType;
53		$this->status = $status;
54	}
55
56	/**
57	 * Get a ScopedLock object representing a lock on resource paths.
58	 * Any locks are released once this object goes out of scope.
59	 * The StatusValue object is updated with any errors or warnings.
60	 *
61	 * @param LockManager $manager
62	 * @param array $paths List of storage paths or map of lock types to path lists
63	 * @param int|string $type LockManager::LOCK_* constant or "mixed" and $paths
64	 *   can be a map of types to paths (since 1.22). Otherwise $type should be an
65	 *   integer and $paths should be a list of paths.
66	 * @param StatusValue $status
67	 * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.22)
68	 * @return ScopedLock|null Returns null on failure
69	 */
70	public static function factory(
71		LockManager $manager, array $paths, $type, StatusValue $status, $timeout = 0
72	) {
73		$pathsByType = is_int( $type ) ? [ $type => $paths ] : $paths;
74		$lockStatus = $manager->lockByType( $pathsByType, $timeout );
75		$status->merge( $lockStatus );
76		if ( $lockStatus->isOK() ) {
77			return new self( $manager, $pathsByType, $status );
78		}
79
80		return null;
81	}
82
83	/**
84	 * Release a scoped lock and set any errors in the attatched StatusValue object.
85	 * This is useful for early release of locks before function scope is destroyed.
86	 * This is the same as setting the lock object to null.
87	 *
88	 * @param ScopedLock|null &$lock
89	 * @since 1.21
90	 */
91	public static function release( ScopedLock &$lock = null ) {
92		$lock = null;
93	}
94
95	/**
96	 * Release the locks when this goes out of scope
97	 */
98	public function __destruct() {
99		$wasOk = $this->status->isOK();
100		$this->status->merge( $this->manager->unlockByType( $this->pathsByType ) );
101		if ( $wasOk ) {
102			// Make sure StatusValue is OK, despite any unlockFiles() fatals
103			$this->status->setResult( true, $this->status->value );
104		}
105	}
106}
107