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<?php

/**

 * CodeIgniter

 *

 * An open source application development framework for PHP

 *

 * This content is released under the MIT License (MIT)

 *

 * Copyright (c) 2014 - 2016, British Columbia Institute of Technology

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 *

 * @package	CodeIgniter

 * @author	EllisLab Dev Team

 * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)

 * @copyright	Copyright (c) 2014 - 2016, British Columbia Institute of Technology (http://bcit.ca/)

 * @license	http://opensource.org/licenses/MIT	MIT License

 * @link	https://codeigniter.com

 * @since	Version 3.0.0

 * @filesource

 */

defined('BASEPATH') OR exit('No direct script access allowed');

/**

 * CodeIgniter Session Memcached Driver

 *

 * @package	CodeIgniter

 * @subpackage	Libraries

 * @category	Sessions

 * @author	Andrey Andreev

 * @link	https://codeigniter.com/user_guide/libraries/sessions.html

 */

class CI_Session_memcached_driver extends CI_Session_driver implements SessionHandlerInterface {

	/**

	 * Memcached instance

	 *

	 * @var	Memcached

	 */

	protected $_memcached;

	/**

	 * Key prefix

	 *

	 * @var	string

	 */

	protected $_key_prefix = 'ci_session:';

	/**

	 * Lock key

	 *

	 * @var	string

	 */

	protected $_lock_key;

	// ------------------------------------------------------------------------

	/**

	 * Class constructor

	 *

	 * @param	array	$params	Configuration parameters

	 * @return	void

	 */

	public function __construct(&$params)

	{

		parent::__construct($params);

		if (empty($this->_config['save_path']))

		{

			log_message('error', 'Session: No Memcached save path configured.');

		}

		if ($this->_config['match_ip'] === TRUE)

		{

			$this->_key_prefix .= $_SERVER['REMOTE_ADDR'].':';

		}

	}

	// ------------------------------------------------------------------------

	/**

	 * Open

	 *

	 * Sanitizes save_path and initializes connections.

	 *

	 * @param	string	$save_path	Server path(s)

	 * @param	string	$name		Session cookie name, unused

	 * @return	bool

	 */

	public function open($save_path, $name)

	{

		$this->_memcached = new Memcached();

		$this->_memcached->setOption(Memcached::OPT_BINARY_PROTOCOL, TRUE); // required for touch() usage

		$server_list = array();

		foreach ($this->_memcached->getServerList() as $server)

		{

			$server_list[] = $server['host'].':'.$server['port'];

		}

		if ( ! preg_match_all('#,?([^,:]+)\:(\d{1,5})(?:\:(\d+))?#', $this->_config['save_path'], $matches, PREG_SET_ORDER))

		{

			$this->_memcached = NULL;

			log_message('error', 'Session: Invalid Memcached save path format: '.$this->_config['save_path']);

			return $this->_fail();

		}

		foreach ($matches as $match)

		{

			// If Memcached already has this server (or if the port is invalid), skip it

			if (in_array($match[1].':'.$match[2], $server_list, TRUE))

			{

				log_message('debug', 'Session: Memcached server pool already has '.$match[1].':'.$match[2]);

				continue;

			}

			if ( ! $this->_memcached->addServer($match[1], $match[2], isset($match[3]) ? $match[3] : 0))

			{

				log_message('error', 'Could not add '.$match[1].':'.$match[2].' to Memcached server pool.');

			}

			else

			{

				$server_list[] = $match[1].':'.$match[2];

			}

		}

		if (empty($server_list))

		{

			log_message('error', 'Session: Memcached server pool is empty.');

			return $this->_fail();

		}

		return $this->_success;

	}

	// ------------------------------------------------------------------------

	/**

	 * Read

	 *

	 * Reads session data and acquires a lock

	 *

	 * @param	string	$session_id	Session ID

	 * @return	string	Serialized session data

	 */

	public function read($session_id)

	{

		if (isset($this->_memcached) && $this->_get_lock($session_id))

		{

			// Needed by write() to detect session_regenerate_id() calls

			$this->_session_id = $session_id;

			$session_data = (string) $this->_memcached->get($this->_key_prefix.$session_id);

			$this->_fingerprint = md5($session_data);

			return $session_data;

		}

		return $this->_fail();

	}

	// ------------------------------------------------------------------------

	/**

	 * Write

	 *

	 * Writes (create / update) session data

	 *

	 * @param	string	$session_id	Session ID

	 * @param	string	$session_data	Serialized session data

	 * @return	bool

	 */

	public function write($session_id, $session_data)

	{

		if ( ! isset($this->_memcached))

		{

			return $this->_fail();

		}

		// Was the ID regenerated?

		elseif ($session_id !== $this->_session_id)

		{

			if ( ! $this->_release_lock() OR ! $this->_get_lock($session_id))

			{

				return $this->_fail();

			}

			$this->_fingerprint = md5('');

			$this->_session_id = $session_id;

		}

		if (isset($this->_lock_key))

		{

			$key = $this->_key_prefix.$session_id;

			$this->_memcached->replace($this->_lock_key, time(), 300);

			if ($this->_fingerprint !== ($fingerprint = md5($session_data)))

			{

				if (

					$this->_memcached->replace($key, $session_data, $this->_config['expiration'])

					OR ($this->_memcached->getResultCode() === Memcached::RES_NOTFOUND && $this->_memcached->set($key, $session_data, $this->_config['expiration']))

				)

				{

					$this->_fingerprint = $fingerprint;

					return $this->_success;

				}

				return $this->_fail();

			}

			if (

				$this->_memcached->touch($key, $this->_config['expiration'])

				OR ($this->_memcached->getResultCode() === Memcached::RES_NOTFOUND && $this->_memcached->set($key, $session_data, $this->_config['expiration']))

			)

			{

				return $this->_success;

			}

		}

		return $this->_fail();

	}

	// ------------------------------------------------------------------------

	/**

	 * Close

	 *

	 * Releases locks and closes connection.

	 *

	 * @return	bool

	 */

	public function close()

	{

		if (isset($this->_memcached))

		{

			$this->_release_lock();

			if ( ! $this->_memcached->quit())

			{

				return $this->_fail();

			}

			$this->_memcached = NULL;

			return $this->_success;

		}

		return $this->_fail();

	}

	// ------------------------------------------------------------------------

	/**

	 * Destroy

	 *

	 * Destroys the current session.

	 *

	 * @param	string	$session_id	Session ID

	 * @return	bool

	 */

	public function destroy($session_id)

	{

		if (isset($this->_memcached, $this->_lock_key))

		{

			$this->_memcached->delete($this->_key_prefix.$session_id);

			$this->_cookie_destroy();

			return $this->_success;

		}

		return $this->_fail();

	}

	// ------------------------------------------------------------------------

	/**

	 * Garbage Collector

	 *

	 * Deletes expired sessions

	 *

	 * @param	int 	$maxlifetime	Maximum lifetime of sessions

	 * @return	bool

	 */

	public function gc($maxlifetime)

	{

		// Not necessary, Memcached takes care of that.

		return $this->_success;

	}

	// ------------------------------------------------------------------------

	/**

	 * Get lock

	 *

	 * Acquires an (emulated) lock.

	 *

	 * @param	string	$session_id	Session ID

	 * @return	bool

	 */

	protected function _get_lock($session_id)

	{

		// PHP 7 reuses the SessionHandler object on regeneration,

		// so we need to check here if the lock key is for the

		// correct session ID.

		if ($this->_lock_key === $this->_key_prefix.$session_id.':lock')

		{

			if ( ! $this->_memcached->replace($this->_lock_key, time(), 300))

			{

				return ($this->_memcached->getResultCode() === Memcached::RES_NOTFOUND)

					? $this->_memcached->set($this->_lock_key, time(), 300)

					: FALSE;

			}

		}

		// 30 attempts to obtain a lock, in case another request already has it

		$lock_key = $this->_key_prefix.$session_id.':lock';

		$attempt = 0;

		do

		{

			if ($this->_memcached->get($lock_key))

			{

				sleep(1);

				continue;

			}

			if ( ! $this->_memcached->set($lock_key, time(), 300))

			{

				log_message('error', 'Session: Error while trying to obtain lock for '.$this->_key_prefix.$session_id);

				return FALSE;

			}

			$this->_lock_key = $lock_key;

			break;

		}

		while (++$attempt < 30);

		if ($attempt === 30)

		{

			log_message('error', 'Session: Unable to obtain lock for '.$this->_key_prefix.$session_id.' after 30 attempts, aborting.');

			return FALSE;

		}

		$this->_lock = TRUE;

		return TRUE;

	}

	// ------------------------------------------------------------------------

	/**

	 * Release lock

	 *

	 * Releases a previously acquired lock

	 *

	 * @return	bool

	 */

	protected function _release_lock()

	{

		if (isset($this->_memcached, $this->_lock_key) && $this->_lock)

		{

			if ( ! $this->_memcached->delete($this->_lock_key) && $this->_memcached->getResultCode() !== Memcached::RES_NOTFOUND)

			{

				log_message('error', 'Session: Error while trying to free lock for '.$this->_lock_key);

				return FALSE;

			}

			$this->_lock_key = NULL;

			$this->_lock = FALSE;

		}

		return TRUE;

	}

}