1 files changed, 172 insertions, 0 deletions
diff --git a/includes/filerepo/backend/lockmanager/LockManager.php b/includes/filerepo/backend/lockmanager/LockManager.php
new file mode 100644
index 000000000000..92dcc3811136
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+++ b/includes/filerepo/backend/lockmanager/LockManager.php
@@ -0,0 +1,172 @@
+<?php
+/**
+ * @file
+ * @ingroup LockManager
+ * @author Aaron Schulz
+ */
+
+/**
+ * Class for handling resource locking.
+ * Locks on resource keys can either be shared or exclusive.
+ * 
+ * Implementations must keep track of what is locked by this proccess
+ * in-memory and support nested locking calls (using reference counting).
+ * At least LOCK_UW and LOCK_EX must be implemented. LOCK_SH can be a no-op.
+ * Locks should either be non-blocking or have low wait timeouts.
+ * 
+ * Subclasses should avoid throwing exceptions at all costs.
+ *
+ * @ingroup LockManager
+ * @since 1.19
+ */
+abstract class LockManager {
+	/* Lock types; stronger locks have higher values */
+	const LOCK_SH = 1; // shared lock (for reads)
+	const LOCK_UW = 2; // shared lock (for reads used to write elsewhere)
+	const LOCK_EX = 3; // exclusive lock (for writes)
+
+	/** @var Array Mapping of lock types to the type actually used */
+	protected $lockTypeMap = array(
+		self::LOCK_SH => self::LOCK_SH,
+		self::LOCK_UW => self::LOCK_EX, // subclasses may use self::LOCK_SH
+		self::LOCK_EX => self::LOCK_EX
+	);
+
+	/**
+	 * Construct a new instance from configuration
+	 *
+	 * @param $config Array
+	 */
+	public function __construct( array $config ) {}
+
+	/**
+	 * Lock the resources at the given abstract paths
+	 * 
+	 * @param $paths Array List of resource names
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @return Status 
+	 */
+	final public function lock( array $paths, $type = self::LOCK_EX ) {
+		$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
+		return $this->doLock( $keys, $this->lockTypeMap[$type] );
+	}
+
+	/**
+	 * Unlock the resources at the given abstract paths
+	 * 
+	 * @param $paths Array List of storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @return Status 
+	 */
+	final public function unlock( array $paths, $type = self::LOCK_EX ) {
+		$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
+		return $this->doUnlock( $keys, $this->lockTypeMap[$type] );
+	}
+
+	/**
+	 * Get the base 36 SHA-1 of a string, padded to 31 digits
+	 * 
+	 * @param $path string
+	 * @return string
+	 */
+	final protected static function sha1Base36( $path ) {
+		return wfBaseConvert( sha1( $path ), 16, 36, 31 );
+	}
+
+	/**
+	 * Lock resources with the given keys and lock type
+	 * 
+	 * @param $key Array List of keys to lock (40 char hex hashes)
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @return string
+	 */
+	abstract protected function doLock( array $keys, $type );
+
+	/**
+	 * Unlock resources with the given keys and lock type
+	 * 
+	 * @param $key Array List of keys to unlock (40 char hex hashes)
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @return string
+	 */
+	abstract protected function doUnlock( array $keys, $type );
+}
+
+/**
+ * LockManager helper class to handle scoped locks, which
+ * release when an object is destroyed or goes out of scope.
+ *
+ * @ingroup LockManager
+ * @since 1.19
+ */
+class ScopedLock {
+	/** @var LockManager */
+	protected $manager;
+	/** @var Status */
+	protected $status;
+	/** @var Array List of resource paths*/
+	protected $paths;
+
+	protected $type; // integer lock type
+
+	/**
+	 * @param $manager LockManager
+	 * @param $paths Array List of storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @param $status Status
+	 */
+	protected function __construct(
+		LockManager $manager, array $paths, $type, Status $status
+	) {
+	   $this->manager = $manager;
+	   $this->paths = $paths;
+	   $this->status = $status;
+	   $this->type = $type;
+	}
+
+	protected function __clone() {}
+
+	/**
+	 * Get a ScopedLock object representing a lock on resource paths.
+	 * Any locks are released once this object goes out of scope.
+	 * The status object is updated with any errors or warnings.
+	 * 
+	 * @param $manager LockManager
+	 * @param $paths Array List of storage paths
+	 * @param $type integer LockManager::LOCK_* constant
+	 * @param $status Status
+	 * @return ScopedLock|null Returns null on failure
+	 */
+	public static function factory(
+		LockManager $manager, array $paths, $type, Status $status
+	) {
+		$lockStatus = $manager->lock( $paths, $type );
+		$status->merge( $lockStatus );
+		if ( $lockStatus->isOK() ) {
+			return new self( $manager, $paths, $type, $status );
+		}
+		return null;
+	}
+
+	function __destruct() {
+		$wasOk = $this->status->isOK();
+		$this->status->merge( $this->manager->unlock( $this->paths, $this->type ) );
+		if ( $wasOk ) {
+			// Make sure status is OK, despite any unlockFiles() fatals
+			$this->status->setResult( true, $this->status->value );
+		}
+	}
+}
+
+/**
+ * Simple version of LockManager that does nothing
+ */
+class NullLockManager extends LockManager {
+	protected function doLock( array $keys, $type ) {
+		return Status::newGood();
+	}
+
+	protected function doUnlock( array $keys, $type ) {
+		return Status::newGood();
+	}
+}