/modules/auth/classes/model/_auth_nodelete/user/token.php

<?php defined('SYSPATH') OR die('No direct access allowed.');

class Model_Auth_User_Token extends ORM {

	// Relationships
	protected $_belongs_to = array('user' => array());

	// Current timestamp
	protected $_now;

	/**
	 * Handles garbage collection and deleting of expired objects.
	 */
	public function __construct($id = NULL)
	{
		parent::__construct($id);

		// Set the now, we use this a lot
		$this->_now = time();

		if (mt_rand(1, 100) === 1)
		{
			// Do garbage collection
			$this->delete_expired();
		}

		if ($this->expires < $this->_now)
		{
			// This object has expired
			$this->delete();
		}
	}

	/**
	 * Overload saving to set the created time and to create a new token
	 * when the object is saved.
	 */
	public function save()
	{
		if ($this->loaded() === FALSE)
		{
			// Set the created time, token, and hash of the user agent
			$this->created = $this->_now;
			$this->user_agent = sha1(Request::$user_agent);
		}

		// Create a new token each time the token is saved
		$this->token = $this->create_token();

		return parent::save();
	}

	/**
	 * Deletes all expired tokens.
	 *
	 * @return  void
	 */
	public function delete_expired()
	{
		// Delete all expired tokens
		DB::delete($this->_table_name)
			->where('expires', '<', $this->_now)
			->execute($this->_db);

		return $this;
	}

	/**
	 * Finds a new unique token, using a loop to make sure that the token does
	 * not already exist in the database. This could potentially become an
	 * infinite loop, but the chances of that happening are very unlikely.
	 *
	 * @return  string
	 */
	protected function create_token()
	{
		while (TRUE)
		{
			// Create a random token
			$token = text::random('alnum', 32);

			// Make sure the token does not already exist
			$count = DB::select('id')
				->where('token', '=', $token)
				->from($this->_table_name)
				->execute($this->_db)
				->count();
			if ($count === 0)
			{
				// A unique token has been found
				return $token;
			}
		}
	}

} // End Auth User Token Model