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<?php
/**
 * Zend Framework (http://framework.zend.com/)
 *
 * @link      http://github.com/zendframework/zf2 for the canonical source repository
 * @copyright Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd New BSD License
 */

namespace Zend\Authentication\Storage;

interface StorageInterface
{
    /**
     * Returns true if and only if storage is empty
     *
     * @throws \Zend\Authentication\Exception\ExceptionInterface If it is impossible to determine whether storage is empty
     * @return bool
     */
    public function isEmpty();

    /**
     * Returns the contents of storage
     *
     * Behavior is undefined when storage is empty.
     *
     * @throws \Zend\Authentication\Exception\ExceptionInterface If reading contents from storage is impossible
     * @return mixed
     */
    public function read();

    /**
     * Writes $contents to storage
     *
     * @param  mixed $contents
     * @throws \Zend\Authentication\Exception\ExceptionInterface If writing $contents to storage is impossible
     * @return void
     */
    public function write($contents);

    /**
     * Clears contents from storage
     *
     * @throws \Zend\Authentication\Exception\ExceptionInterface If clearing contents from storage is impossible
     * @return void
     */
    public function clear();
}