owncloud/core

<?php
/**
 * @author Robin Appelman <icewind@owncloud.com>
 *
 * @copyright Copyright (c) 2018, ownCloud GmbH
 * @license AGPL-3.0
 *
 * This code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program 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, version 3,
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */

namespace OC\Lock;

use OCP\Lock\ILockingProvider;

/**
 * Base locking provider that keeps track of locks acquired during the current request
 * to release any left over locks at the end of the request
 */
abstract class AbstractLockingProvider implements ILockingProvider {
    protected $ttl; // how long until we clear stray locks in seconds

    protected $acquiredLocks = [
        'shared' => [],
        'exclusive' => []
    ];

    /**
     * Check if we've locally acquired a lock
     *
     * @param string $path
     * @param int $type
     * @return bool
     */
    protected function hasAcquiredLock($path, $type) {
        if ($type === self::LOCK_SHARED) {
            return isset($this->acquiredLocks['shared'][$path]) && $this->acquiredLocks['shared'][$path] > 0;
        } else {
            return isset($this->acquiredLocks['exclusive'][$path]) && $this->acquiredLocks['exclusive'][$path] === true;
        }
    }

    /**
     * Mark a locally acquired lock
     *
     * @param string $path
     * @param int $type self::LOCK_SHARED or self::LOCK_EXCLUSIVE
     */
    protected function markAcquire($path, $type) {
        if ($type === self::LOCK_SHARED) {
            if (!isset($this->acquiredLocks['shared'][$path])) {
                $this->acquiredLocks['shared'][$path] = 0;
            }
            $this->acquiredLocks['shared'][$path]++;
        } else {
            $this->acquiredLocks['exclusive'][$path] = true;
        }
    }

    /**
     * Mark a release of a locally acquired lock
     *
     * @param string $path
     * @param int $type self::LOCK_SHARED or self::LOCK_EXCLUSIVE
     */
    protected function markRelease($path, $type) {
        if ($type === self::LOCK_SHARED) {
            if (isset($this->acquiredLocks['shared'][$path]) and $this->acquiredLocks['shared'][$path] > 0) {
                $this->acquiredLocks['shared'][$path]--;
                if ($this->acquiredLocks['shared'][$path] === 0) {
                    unset($this->acquiredLocks['shared'][$path]);
                }
            }
        } elseif ($type === self::LOCK_EXCLUSIVE) {
            unset($this->acquiredLocks['exclusive'][$path]);
        }
    }

    /**
     * Change the type of an existing tracked lock
     *
     * @param string $path
     * @param int $targetType self::LOCK_SHARED or self::LOCK_EXCLUSIVE
     */
    protected function markChange($path, $targetType) {
        if ($targetType === self::LOCK_SHARED) {
            unset($this->acquiredLocks['exclusive'][$path]);
            if (!isset($this->acquiredLocks['shared'][$path])) {
                $this->acquiredLocks['shared'][$path] = 0;
            }
            $this->acquiredLocks['shared'][$path]++;
        } elseif ($targetType === self::LOCK_EXCLUSIVE) {
            $this->acquiredLocks['exclusive'][$path] = true;
            $this->acquiredLocks['shared'][$path]--;
            if ($this->acquiredLocks['shared'][$path] === 0) {
                unset($this->acquiredLocks['shared'][$path]);
            }
        }
    }

    /**
     * release all lock acquired by this instance which were marked using the mark* methods
     */
    public function releaseAll() {
        foreach ($this->acquiredLocks['shared'] as $path => $count) {
            \OCP\Util::writeLog('core', "cleaning $count stray shared locks for $path", \OCP\Util::INFO);
            for ($i = 0; $i < $count; $i++) {
                $this->releaseLock($path, self::LOCK_SHARED);
            }
        }

        foreach ($this->acquiredLocks['exclusive'] as $path => $hasLock) {
            \OCP\Util::writeLog('core', "cleaning stray exclusive locks for $path", \OCP\Util::INFO);
            $this->releaseLock($path, self::LOCK_EXCLUSIVE);
        }
    }

    protected function getOwnSharedLockCount($path) {
        return isset($this->acquiredLocks['shared'][$path]) ? $this->acquiredLocks['shared'][$path] : 0;
    }
}