1: <?php
  2: /**
  3:  * CCacheDependency class file.
  4:  *
  5:  * @author Qiang Xue <qiang.xue@gmail.com>
  6:  * @link http://www.yiiframework.com/
  7:  * @copyright 2008-2013 Yii Software LLC
  8:  * @license http://www.yiiframework.com/license/
  9:  */
 10: 
 11: /**
 12:  * CCacheDependency is the base class for cache dependency classes.
 13:  *
 14:  * CCacheDependency implements the {@link ICacheDependency} interface.
 15:  * Child classes should override its {@link generateDependentData} for
 16:  * actual dependency checking.
 17:  *
 18:  * @property boolean $hasChanged Whether the dependency has changed.
 19:  * @property mixed $dependentData The data used to determine if dependency has been changed.
 20:  * This data is available after {@link evaluateDependency} is called.
 21:  *
 22:  * @author Qiang Xue <qiang.xue@gmail.com>
 23:  * @package system.caching.dependencies
 24:  * @since 1.0
 25:  */
 26: class CCacheDependency extends CComponent implements ICacheDependency
 27: {
 28:     /**
 29:      * @var boolean Whether this dependency is reusable or not.
 30:      * If set to true, dependent data for this cache dependency will only be generated once per request.
 31:      * You can then use the same cache dependency for multiple separate cache calls on the same page
 32:      * without the overhead of re-evaluating the dependency each time.
 33:      * Defaults to false;
 34:      * @since 1.1.11
 35:      */
 36:     public $reuseDependentData=false;
 37: 
 38:     /**
 39:      * @var array cached data for reusable dependencies.
 40:      * @since 1.1.11
 41:      */
 42:     private static $_reusableData=array();
 43: 
 44:     private $_hash;
 45:     private $_data;
 46: 
 47:     /**
 48:      * Evaluates the dependency by generating and saving the data related with dependency.
 49:      * This method is invoked by cache before writing data into it.
 50:      */
 51:     public function evaluateDependency()
 52:     {
 53:         if ($this->reuseDependentData)
 54:         {
 55:             $hash=$this->getHash();
 56:             if(!isset(self::$_reusableData[$hash]['dependentData']))
 57:                 self::$_reusableData[$hash]['dependentData']=$this->generateDependentData();
 58:             $this->_data=self::$_reusableData[$hash]['dependentData'];
 59:         }
 60:         else
 61:             $this->_data=$this->generateDependentData();
 62:     }
 63: 
 64:     /**
 65:      * @return boolean whether the dependency has changed.
 66:      */
 67:     public function getHasChanged()
 68:     {
 69:         if ($this->reuseDependentData)
 70:         {
 71:             $hash=$this->getHash();
 72:             if(!isset(self::$_reusableData[$hash]['dependentData']))
 73:                 self::$_reusableData[$hash]['dependentData']=$this->generateDependentData();
 74:             return self::$_reusableData[$hash]['dependentData']!=$this->_data;
 75:         }
 76:         else
 77:             return $this->generateDependentData()!=$this->_data;
 78:     }
 79: 
 80:     /**
 81:      * @return mixed the data used to determine if dependency has been changed.
 82:      * This data is available after {@link evaluateDependency} is called.
 83:      */
 84:     public function getDependentData()
 85:     {
 86:         return $this->_data;
 87:     }
 88: 
 89:     /**
 90:      * Resets cached data for reusable dependencies.
 91:      * @since 1.1.14
 92:      */
 93:     public static function resetReusableData()
 94:     {
 95:         self::$_reusableData=array();
 96:     }
 97: 
 98:     /**
 99:      * Generates the data needed to determine if dependency has been changed.
100:      * Derived classes should override this method to generate actual dependent data.
101:      * @return mixed the data needed to determine if dependency has been changed.
102:      */
103:     protected function generateDependentData()
104:     {
105:         return null;
106:     }
107:     /**
108:      * Generates a unique hash that identifies this cache dependency.
109:      * @return string the hash for this cache dependency
110:      */
111:     private function getHash()
112:     {
113:         if($this->_hash===null)
114:             $this->_hash=sha1(serialize($this));
115:         return $this->_hash;
116:     }
117: }