Move Lock to private namespace, add interface. Update PHPDoc.

2 files changed, 310 insertions, 2 deletions

diff --git a/lib/private/files/lock.php b/lib/private/files/lock.php
new file mode 100644
index 00000000000..b752b16f023
--- /dev/null
+++ b/lib/private/files/lock.php
@@ -0,0 +1,308 @@
+<?php
+/**
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or any later version.
+ *
+ * This library 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 AFFERO GENERAL PUBLIC LICENSE for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public
+ * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OC\Files;
+
+use OCP\Config;
+use OC\Files\Filesystem;
+
+/**
+ * Class Lock
+ * @package OC\Files
+ */
+class Lock implements \OCP\Files\Lock {
+
+	/** @var int $retries Number of lock retries to attempt */
+	public static $retries = 40;
+
+	/** @var int $retryInterval Milliseconds between retries */
+	public static $retryInterval = 50;
+
+	/** @var string $path Filename of the file as represented in storage */
+	protected $path;
+
+	/** @var array $stack A stack of lock data */
+	protected $stack = array();
+
+	/** @var resource $handle A file handle used to maintain a lock  */
+	protected $handle;
+
+	/** @var string $lockFile Filename of the lock file */
+	protected $lockFile;
+
+	/** @var resource $lockFileHandle The file handle used to maintain a lock on the lock file */
+	protected $lockFileHandle;
+
+	/**
+	 * Constructor for the lock instance
+	 * @param string $path Absolute pathname for a local file on which to obtain a lock
+	 */
+	public function __construct($path) {
+		$this->path = Filesystem::normalizePath($path);
+	}
+
+	protected function obtainReadLock($existingHandle = null) {
+		\OC_Log::write('lock', sprintf('INFO: Read lock requested for %s', $this->path), \OC_Log::DEBUG);
+		$timeout = Lock::$retries;
+
+		// Re-use an existing handle or get a new one
+		if(empty($existingHandle)) {
+			$handle = fopen($this->path, 'r');
+		}
+		else {
+			$handle = $existingHandle;
+		}
+
+		do {
+			if($this->isLockFileLocked($this->getLockFile($this->path))) {
+				\OC_Log::write('lock', sprintf('INFO: Read lock has locked lock file %s for %s', $this->getLockFile($this->path), $this->path), \OC_Log::DEBUG);
+				do {
+					usleep(Lock::$retryInterval);
+					$timeout--;
+				} while($this->isLockFileLocked($this->getLockFile($this->path)) && $timeout > 0);
+				\OC_Log::write('lock', sprintf('INFO: Lock file %s has become unlocked for %s', $this->getLockFile($this->path), $this->path), \OC_Log::DEBUG);
+			}
+		} while ((!$lockReturn = flock($handle, LOCK_SH | LOCK_NB, $wouldBlock)) && $timeout > 0);
+		if ($wouldBlock == true || $lockReturn == false || $timeout <= 0) {
+			\OC_Log::write('lock', sprintf('FAIL: Failed to acquire read lock for %s', $this->path), \OC_Log::DEBUG);
+			return false;
+		}
+		$this->handle = $handle;
+		\OC_Log::write('lock', sprintf('PASS: Acquired read lock for %s', $this->path), \OC_Log::DEBUG);
+		return true;
+	}
+
+	protected function obtainWriteLock($existingHandle = null) {
+		\OC_Log::write('lock', sprintf('INFO: Write lock requested for %s', $this->path), \OC_Log::DEBUG);
+
+		// Re-use an existing handle or get a new one
+		if (empty($existingHandle)) {
+			$handle = fopen($this->path, 'c');
+		}
+		else {
+			$handle = $existingHandle;
+		}
+
+		// If the file doesn't exist, but we can create a lock for it
+		if (!file_exists($this->path) && $this->lockLockFile($this->path)) {
+			$lockReturn = flock($handle, LOCK_EX | LOCK_NB, $wouldBlock);
+			if ($lockReturn == false || $wouldBlock == true) {
+				\OC_Log::write('lock', sprintf('FAIL: Write lock failed, unable to exclusively lock new file %s', $this->path), \OC_Log::DEBUG);
+				return false;
+			}
+			$this->handle = $handle;
+			return true;
+		}
+
+
+		// Since this file does exist, wait for locks to release to get an exclusive lock
+		$timeout = Lock::$retries;
+		$haveBlock = false;
+		while ((!$lockReturn = flock($handle, LOCK_EX | LOCK_NB, $wouldBlock)) && $timeout > 0) {
+			// We don't have a lock on the original file, try to get a lock on its lock file
+			if ($haveBlock || $haveBlock = $this->lockLockFile($this->lockFile)) {
+				usleep(Lock::$retryInterval);
+			}
+			else {
+				\OC_Log::write('lock', sprintf('FAIL: Write lock failed, unable to lock original %s or lock file', $this->path), \OC_Log::DEBUG);
+				return false;
+			}
+			$timeout--;
+		}
+		if ($wouldBlock == true || $lockReturn == false) {
+			\OC_Log::write('lock', sprintf('FAIL: Write lock failed due to timeout on %s', $this->path), \OC_Log::DEBUG);
+			return false;
+		}
+		\OC_Log::write('lock', sprintf('PASS: Write lock succeeded on %s', $this->path), \OC_Log::DEBUG);
+
+		return true;
+	}
+
+	/**
+	 * Create a lock file and lock it
+	 * Sets $this->lockFile to the specified lock file, indicating that the lock file is IN USE for this lock instance
+	 * Also sets $this->lockFileHandle to a file handle of the lock file
+	 * @param string $filename The name of the file to lock
+	 * @return bool False if lock can't be acquired, true if it can.
+	 */
+	protected function lockLockFile ( $filename ) {
+		$lockFile = $this->getLockFile($filename);
+		\OC_Log::write('lock', sprintf('INFO: Locking lock file %s for %s', $lockFile, $filename), \OC_Log::DEBUG);
+
+		// If we already manage the lockfile, success
+		if(!empty($this->lockFile)) {
+			\OC_Log::write('lock', sprintf('PASS: Lock file %s was locked by this request for %s', $lockFile, $filename), \OC_Log::DEBUG);
+			return true;
+		}
+
+		// Check if the lockfile exists, and if not, try to create it
+		\OC_Log::write('lock', sprintf('INFO: Does lock file %s already exist?  %s', $lockFile, file_exists($lockFile) ? 'yes' : 'no'), \OC_Log::DEBUG);
+		$handle = fopen($lockFile, 'c');
+		if(!$handle) {
+			\OC_Log::write('lock', sprintf('FAIL: Could not create lock file %s', $lockFile), \OC_Log::DEBUG);
+			return false;
+		}
+
+		// Attempt to acquire lock on lock file
+		$wouldBlock = false;
+		$timeout = self::$retries;
+		// Wait for lock over timeout
+		while((!$lockReturn = flock($handle, LOCK_EX | LOCK_NB, $wouldBlock)) && $timeout > 0) {
+			\OC_Log::write('lock', sprintf('FAIL: Could not acquire lock on lock file %s, %s timeout increments remain.', $lockFile, $timeout), \OC_Log::DEBUG);
+			usleep(self::$retryInterval);
+			$timeout--;
+		}
+		if ($wouldBlock == true || $lockReturn == false) {
+			\OC_Log::write('lock', sprintf('FAIL: Could not acquire lock on lock file %s', $lockFile), \OC_Log::DEBUG);
+			return false;
+		}
+		fwrite($handle, $filename);
+		\OC_Log::write('lock', sprintf('PASS: Wrote filename to lock lock file %s', $lockFile), \OC_Log::DEBUG);
+
+		$this->lockFile = $lockFile;
+		$this->lockFileHandle = $handle;
+
+		return true;
+	}
+
+	/**
+	 * Add a lock of a specific type to the stack
+	 * @param integer $lockType A constant representing the type of lock to queue
+	 * @param null|resource $existingHandle An existing file handle from an fopen()
+	 * @throws LockNotAcquiredException
+	 */
+	public function addLock($lockType, $existingHandle = null) {
+		if(!isset($this->stack[$lockType])) {
+			switch($lockType) {
+				case Lock::READ:
+					$result = $this->obtainReadLock($existingHandle);
+					break;
+				case Lock::WRITE:
+					$result = $this->obtainWriteLock($existingHandle);
+					break;
+				default:
+					$result = false;
+					break;
+			}
+			if($result) {
+				$this->stack[$lockType] = 0;
+			}
+			else {
+				throw new LockNotAcquiredException($this->path, $lockType);
+			}
+		}
+
+		\OC_Log::write('lock', sprintf('INFO: Incrementing lock type %d count for %s', $lockType, $this->path), \OC_Log::DEBUG);
+		$this->stack[$lockType]++;
+
+	}
+
+	/**
+	 * Release locks on handles and files
+	 */
+	public function release($lockType) {
+		if(isset($this->stack[$lockType])) {
+			$this->stack[$lockType]--;
+			if($this->stack[$lockType] <= 0) {
+				unset($this->stack[$lockType]);
+			}
+		}
+
+		if(count($this->stack) == 0) {
+			// No more locks needed on this file, release the handle and/or lockfile
+			$this->releaseAll();
+		}
+
+		return true;
+	}
+
+
+	/**
+	 * Get the lock file associated to a file
+	 * @param string $filename The filename of the file to create a lock file for
+	 * @return string The filename of the lock file
+	 */
+	public static function getLockFile($filename) {
+		static $locksDir = false;
+		if(!$locksDir) {
+			$dataDir = Config::getSystemValue('datadirectory');
+			$locksDir = $dataDir . '/.locks';
+			if(!file_exists($locksDir)) {
+				mkdir($locksDir);
+			}
+		}
+		$filename = Filesystem::normalizePath($filename);
+		return $locksDir . '/' . sha1($filename) . '.lock';
+	}
+
+	/**
+	 * Determine if a file has an associated and flocked lock file
+	 * @param string $lockFile The filename of the lock file to check
+	 * @return bool True if the lock file is flocked
+	 */
+	protected function isLockFileLocked($lockFile) {
+		if(file_exists($lockFile)) {
+			if($handle = fopen($lockFile, 'c')) {
+				if($lock = flock($handle, LOCK_EX | LOCK_NB)) {
+					// Got lock, not blocking, release and unlink
+					unlink($lockFile);
+					fclose($handle);
+					flock($lock, LOCK_UN);
+					return false;
+				}
+				else {
+					return true;
+				}
+			}
+			else {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * Release all queued locks on the file
+	 * @return bool
+	 */
+	public function releaseAll() {
+		$this->stack = array();
+		\OC_Log::write('lock', sprintf('INFO: Releasing locks on %s', $this->path), \OC_Log::DEBUG);
+		if (!empty($this->handle) && is_resource($this->handle)) {
+			flock($this->handle, LOCK_UN);
+			\OC_Log::write('lock', sprintf('INFO: Released lock handle %s on %s', $this->handle, $this->path), \OC_Log::DEBUG);
+			$this->handle = null;
+		}
+		if (!empty($this->lockFile) && file_exists($this->lockFile)) {
+			unlink($this->lockFile);
+			\OC_Log::write('lock', sprintf('INFO: Released lock file %s on %s', $this->lockFile, $this->path), \OC_Log::DEBUG);
+			$this->lockFile = null;
+		}
+		\OC_Log::write('lock', sprintf('FREE: Released locks on %s', $this->path), \OC_Log::DEBUG);
+		return true;
+	}
+
+	public function __destruct() {
+		// Only releaseAll if we have locks to release
+		if(!empty($this->handle) || !empty($this->lockFile)) {
+			\OC_Log::write('lock', sprintf('INFO: Destroying locks on %s', $this->path), \OC_Log::DEBUG);
+			$this->releaseAll();
+		}
+	}
+
+}
\ No newline at end of file
diff --git a/lib/private/files/storage/wrapper/lockingwrapper.php b/lib/private/files/storage/wrapper/lockingwrapper.php
index 4f41c528253..428c2c516a4 100644
--- a/lib/private/files/storage/wrapper/lockingwrapper.php
+++ b/lib/private/files/storage/wrapper/lockingwrapper.php
@@ -10,7 +10,7 @@
 namespace OC\Files\Storage\Wrapper;
 
 use OC\Files\Filesystem;
-use OCP\Files\Lock;
+use OC\Files\Lock;
 
 /**
  * Class LockingWrapper
@@ -23,7 +23,7 @@ use OCP\Files\Lock;
  */
 class LockingWrapper extends Wrapper {
 
-	/** @var array $locks Holds an array of lock instances indexed by path for this storage */
+	/** @var \OCP\Files\Lock[] $locks Holds an array of lock instances indexed by path for this storage */
 	protected $locks = array();
 
 	/**