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