interface/modules/zend_modules/library/Zend/Authentication/Storage/Chain.php

   1 <?php
   2 /**
   3  * Zend Framework (http://framework.zend.com/)
   4  *
   5  * @link      http://github.com/zendframework/zf2 for the canonical source repository
   6  * @copyright Copyright (c) 2005-2013 Zend Technologies USA Inc. (http://www.zend.com)
   7  * @license   http://framework.zend.com/license/new-bsd New BSD License
   8  */
   9
  10 namespace Zend\Authentication\Storage;
  11
  12 use Zend\Authentication\Storage\StorageInterface;
  13 use Zend\Stdlib\PriorityQueue;
  14
  15 class Chain implements StorageInterface
  16 {
  17     /**
  18      * Contains all storage that this authentication method uses. A storage
  19      * placed in the priority queue with a higher priority is always used
  20      * before using a storage with a lower priority.
  21      *
  22      * @var PriorityQueue
  23      */
  24     protected $storageChain;
  25
  26     /**
  27      * Initializes the priority queue.
  28      */
  29     public function __construct()
  30     {
  31         $this->storageChain = new PriorityQueue();
  32     }
  33
  34     /**
  35      * @param StorageInterface $storage
  36      * @param int          $priority
  37      */
  38     public function add(StorageInterface $storage, $priority = 1)
  39     {
  40         $this->storageChain->insert($storage, $priority);
  41     }
  42
  43     /**
  44      * Loop over the queue of storage until a storage is found that is non-empty. If such
  45      * storage is not found, then this chain storage itself is empty.
  46      *
  47      * In case a non-empty storage is found then this chain storage is also non-empty. Report
  48      * that, but also make sure that all storage with higher priorty that are empty
  49      * are filled.
  50      *
  51      * @see StorageInterface::isEmpty()
  52      */
  53     public function isEmpty()
  54     {
  55         $storageWithHigherPriority = array();
  56
  57         // Loop invariant: $storageWithHigherPriority contains all storage with higher priorty
  58         // than the current one.
  59         foreach ($this->storageChain as $storage) {
  60             if ($storage->isEmpty()) {
  61                 $storageWithHigherPriority[] = $storage;
  62                 continue;
  63             }
  64
  65             $storageValue = $storage->read();
  66             foreach ($storageWithHigherPriority as $higherPriorityStorage) {
  67                 $higherPriorityStorage->write($storageValue);
  68             }
  69
  70             return false;
  71         }
  72
  73         return true;
  74     }
  75
  76     /**
  77      * If the chain is non-empty then the storage with the top priority is guaranteed to be
  78      * filled. Return its value.
  79      *
  80      * @see StorageInterface::read()
  81      */
  82     public function read()
  83     {
  84         return $this->storageChain->top()->read();
  85     }
  86
  87     /**
  88      * Write the new $contents to all storage in the chain.
  89      *
  90      * @see StorageInterface::write()
  91      */
  92     public function write($contents)
  93     {
  94         foreach ($this->storageChain as $storage) {
  95             $storage->write($contents);
  96         }
  97     }
  98
  99     /**
 100      * Clear all storage in the chain.
 101      *
 102      * @see StorageInterface::clear()
 103      */
 104     public function clear()
 105     {
 106         foreach ($this->storageChain as $storage) {
 107             $storage->clear();
 108         }
 109     }
 110 }