1: <?php
  2: /**
  3:  * This class loops through a given list of storage drivers to search for a
  4:  * cached value.  This driver allows for use of caching backends on top of
  5:  * persistent backends.
  6:  *
  7:  * Copyright 2010-2012 Horde LLC (http://www.horde.org/)
  8:  *
  9:  * See the enclosed file COPYING for license information (LGPL). If you
 10:  * did not receive this file, see http://www.horde.org/licenses/lgpl21.
 11:  *
 12:  * @author   Michael Slusarz <slusarz@horde.org>
 13:  * @category Horde
 14:  * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
 15:  * @package  Cache
 16:  */
 17: class Horde_Cache_Storage_Stack extends Horde_Cache_Storage_Base
 18: {
 19:     /**
 20:      * Stack of cache drivers.
 21:      *
 22:      * @var string
 23:      */
 24:     protected $_stack = array();
 25: 
 26:     /**
 27:      * Constructor.
 28:      *
 29:      * @param array $params  Parameters:
 30:      * <pre>
 31:      * 'stack' - (array) [REQUIRED] An array of storage instances to loop
 32:      *           through, in order of priority. The last entry is considered
 33:      *           the 'master' driver, for purposes of writes.
 34:      * </pre>
 35:      *
 36:      * @throws InvalidArgumentException
 37:      */
 38:     public function __construct(array $params = array())
 39:     {
 40:         if (!isset($params['stack'])) {
 41:             throw new InvalidArgumentException('Missing stack parameter.');
 42:         }
 43:         $this->_stack = $params['stack'];
 44:         unset($params['stack']);
 45: 
 46:         parent::__construct($params);
 47:     }
 48: 
 49:     /**
 50:      */
 51:     public function get($key, $lifetime = 0)
 52:     {
 53:         foreach ($this->_stack as $val) {
 54:             $result = $val->get($key, $lifetime);
 55:             if ($result !== false) {
 56:                 return $result;
 57:             }
 58:         }
 59: 
 60:         return false;
 61:     }
 62: 
 63:     /**
 64:      */
 65:     public function set($key, $data, $lifetime = 0)
 66:     {
 67:         /* Do writes in *reverse* order - it is OK if a write to one of the
 68:          * non-master backends fails. */
 69:         $master = true;
 70: 
 71:         foreach (array_reverse($this->_stack) as $val) {
 72:             $result = $val->set($key, $data, $lifetime);
 73:             if ($result === false) {
 74:                 if ($master) {
 75:                     return;
 76:                 }
 77: 
 78:                 /* Attempt to invalidate cache if write failed. */
 79:                 $val->expire($key);
 80:             }
 81:             $master = false;
 82:         }
 83:     }
 84: 
 85:     /**
 86:      */
 87:     public function exists($key, $lifetime = 0)
 88:     {
 89:         foreach ($this->_stack as $val) {
 90:             $result = $val->exists($key, $lifetime);
 91:             if ($result === true) {
 92:                 break;
 93:             }
 94:         }
 95: 
 96:         return $result;
 97:     }
 98: 
 99:     /**
100:      */
101:     public function expire($key)
102:     {
103:         /* Only report success from master. */
104:         $master = $success = true;
105: 
106:         foreach (array_reverse($this->_stack) as $val) {
107:             $result = $val->expire($key);
108:             if ($master && ($result === false)) {
109:                 $success = false;
110:             }
111:             $master = false;
112:         }
113: 
114:         return $success;
115:     }
116: 
117:     /**
118:      */
119:     public function clear()
120:     {
121:         /* Only report errors from master. */
122:         $exception = null;
123:         $master = true;
124: 
125:         foreach (array_reverse($this->_stack) as $val) {
126:             try {
127:                 $val->clear();
128:             } catch (Horde_Cache_Exception $e) {
129:                 if ($master) {
130:                     $exception = $e;
131:                 }
132:             }
133:             $master = false;
134:         }
135: 
136:         if ($exception) {
137:             throw $exception;
138:         }
139:     }
140: 
141: }
142: