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   1  <?php
   2  
   3  /**
   4   * Abstract class representing Definition cache managers that implements
   5   * useful common methods and is a factory.
   6   * @todo Create a separate maintenance file advanced users can use to
   7   *       cache their custom HTMLDefinition, which can be loaded
   8   *       via a configuration directive
   9   * @todo Implement memcached
  10   */
  11  abstract class HTMLPurifier_DefinitionCache
  12  {
  13  
  14      public $type;
  15  
  16      /**
  17       * @param $name Type of definition objects this instance of the
  18       *      cache will handle.
  19       */
  20      public function __construct($type) {
  21          $this->type = $type;
  22      }
  23  
  24      /**
  25       * Generates a unique identifier for a particular configuration
  26       * @param Instance of HTMLPurifier_Config
  27       */
  28      public function generateKey($config) {
  29          return $config->version . ',' . // possibly replace with function calls
  30                 $config->getBatchSerial($this->type) . ',' .
  31                 $config->get($this->type, 'DefinitionRev');
  32      }
  33  
  34      /**
  35       * Tests whether or not a key is old with respect to the configuration's
  36       * version and revision number.
  37       * @param $key Key to test
  38       * @param $config Instance of HTMLPurifier_Config to test against
  39       */
  40      public function isOld($key, $config) {
  41          if (substr_count($key, ',') < 2) return true;
  42          list($version, $hash, $revision) = explode(',', $key, 3);
  43          $compare = version_compare($version, $config->version);
  44          // version mismatch, is always old
  45          if ($compare != 0) return true;
  46          // versions match, ids match, check revision number
  47          if (
  48              $hash == $config->getBatchSerial($this->type) &&
  49              $revision < $config->get($this->type, 'DefinitionRev')
  50          ) return true;
  51          return false;
  52      }
  53  
  54      /**
  55       * Checks if a definition's type jives with the cache's type
  56       * @note Throws an error on failure
  57       * @param $def Definition object to check
  58       * @return Boolean true if good, false if not
  59       */
  60      public function checkDefType($def) {
  61          if ($def->type !== $this->type) {
  62              trigger_error("Cannot use definition of type {$def->type} in cache for {$this->type}");
  63              return false;
  64          }
  65          return true;
  66      }
  67  
  68      /**
  69       * Adds a definition object to the cache
  70       */
  71      abstract public function add($def, $config);
  72  
  73      /**
  74       * Unconditionally saves a definition object to the cache
  75       */
  76      abstract public function set($def, $config);
  77  
  78      /**
  79       * Replace an object in the cache
  80       */
  81      abstract public function replace($def, $config);
  82  
  83      /**
  84       * Retrieves a definition object from the cache
  85       */
  86      abstract public function get($config);
  87  
  88      /**
  89       * Removes a definition object to the cache
  90       */
  91      abstract public function remove($config);
  92  
  93      /**
  94       * Clears all objects from cache
  95       */
  96      abstract public function flush($config);
  97  
  98      /**
  99       * Clears all expired (older version or revision) objects from cache
 100       * @note Be carefuly implementing this method as flush. Flush must
 101       *       not interfere with other Definition types, and cleanup()
 102       *       should not be repeatedly called by userland code.
 103       */
 104      abstract public function cleanup($config);
 105  
 106  }
 107  
 108  // vim: et sw=4 sts=4