API@RTK0.NET

<?php
class DrupalDatabaseCache implements DrupalCacheInterface {
  protected $bin;

  function __construct($bin) {
    $this->bin = $bin;
  }

  function get($cid) {
    $cids = array($cid);
    $cache = $this->getMultiple($cids);
    return reset($cache);
  }

  function getMultiple(&$cids) {
    try {
      // Garbage collection necessary when enforcing a minimum cache lifetime.
      $this->garbageCollection($this->bin);

      // When serving cached pages, the overhead of using db_select() was found
      // to add around 30% overhead to the request. Since $this->bin is a
      // variable, this means the call to db_query() here uses a concatenated
      // string. This is highly discouraged under any other circumstances, and
      // is used here only due to the performance overhead we would incur
      // otherwise. When serving an uncached page, the overhead of using
      // db_select() is a much smaller proportion of the request.
      $result = db_query('SELECT cid, data, created, expire, serialized FROM {' . db_escape_table($this->bin) . '} WHERE cid IN (:cids)', array(':cids' => $cids));
      $cache = array();
      foreach ($result as $item) {
        $item = $this->prepareItem($item);
        if ($item) {
          $cache[$item->cid] = $item;
        }
      }
      $cids = array_diff($cids, array_keys($cache));
      return $cache;
    }
    catch (Exception $e) {
      // If the database is never going to be available, cache requests should
      // return FALSE in order to allow exception handling to occur.
      return array();
    }
  }

  /**
   * Garbage collection for get() and getMultiple().
   *
   * @param $bin
   *   The bin being requested.
   */
  protected function garbageCollection() {
    global $user;

    // Garbage collection necessary when enforcing a minimum cache lifetime.
    $cache_flush = variable_get('cache_flush_' . $this->bin, 0);
    if ($cache_flush && ($cache_flush + variable_get('cache_lifetime', 0) <= REQUEST_TIME)) {
      // Reset the variable immediately to prevent a meltdown in heavy load situations.
      variable_set('cache_flush_' . $this->bin, 0);
      // Time to flush old cache data
      db_delete($this->bin)
        ->condition('expire', CACHE_PERMANENT, '<>')
        ->condition('expire', $cache_flush, '<=')
        ->execute();
    }
  }

  /**
   * Prepare a cached item.
   *
   * Checks that items are either permanent or did not expire, and unserializes
   * data as appropriate.
   *
   * @param $cache
   *   An item loaded from cache_get() or cache_get_multiple().
   * @return
   *   The item with data unserialized as appropriate or FALSE if there is no
   *   valid item to load.
   */
  protected function prepareItem($cache) {
    global $user;

    if (!isset($cache->data)) {
      return FALSE;
    }
    // If enforcing a minimum cache lifetime, validate that the data is
    // currently valid for this user before we return it by making sure the cache
    // entry was created before the timestamp in the current session's cache
    // timer. The cache variable is loaded into the $user object by _drupal_session_read()
    // in session.inc. If the data is permanent or we're not enforcing a minimum
    // cache lifetime always return the cached data.
    if ($cache->expire != CACHE_PERMANENT && variable_get('cache_lifetime', 0) && $user->cache > $cache->created) {
      // This cache data is too old and thus not valid for us, ignore it.
      return FALSE;
    }

    if ($cache->serialized) {
      $cache->data = unserialize($cache->data);
    }

    return $cache;
  }

  function set($cid, $data, $expire = CACHE_PERMANENT) {
    $fields = array(
      'serialized' => 0, 
      'created' => REQUEST_TIME, 
      'expire' => $expire,
    );
    if (!is_string($data)) {
      $fields['data'] = serialize($data);
      $fields['serialized'] = 1;
    }
    else {
      $fields['data'] = $data;
      $fields['serialized'] = 0;
    }

    try {
      db_merge($this->bin)
        ->key(array('cid' => $cid))
        ->fields($fields)
        ->execute();
    }
    catch (Exception $e) {
      // The database may not be available, so we'll ignore cache_set requests.
    }
  }

  function clear($cid = NULL, $wildcard = FALSE) {
    global $user;

    if (empty($cid)) {
      if (variable_get('cache_lifetime', 0)) {
        // We store the time in the current user's $user->cache variable which
        // will be saved into the sessions bin by _drupal_session_write(). We then
        // simulate that the cache was flushed for this user by not returning
        // cached data that was cached before the timestamp.
        $user->cache = REQUEST_TIME;

        $cache_flush = variable_get('cache_flush_' . $this->bin, 0);
        if ($cache_flush == 0) {
          // This is the first request to clear the cache, start a timer.
          variable_set('cache_flush_' . $this->bin, REQUEST_TIME);
        }
        elseif (REQUEST_TIME > ($cache_flush + variable_get('cache_lifetime', 0))) {
          // Clear the cache for everyone, cache_lifetime seconds have
          // passed since the first request to clear the cache.
          db_delete($this->bin)
            ->condition('expire', CACHE_PERMANENT, '<>')
            ->condition('expire', REQUEST_TIME, '<')
            ->execute();
          variable_set('cache_flush_' . $this->bin, 0);
        }
      }
      else {
        // No minimum cache lifetime, flush all temporary cache entries now.
        db_delete($this->bin)
          ->condition('expire', CACHE_PERMANENT, '<>')
          ->condition('expire', REQUEST_TIME, '<')
          ->execute();
      }
    }
    else {
      if ($wildcard) {
        if ($cid == '*') {
          db_truncate($this->bin)->execute();
        }
        else {
          db_delete($this->bin)
            ->condition('cid', db_like($cid) . '%', 'LIKE')
            ->execute();
        }
      }
      elseif (is_array($cid)) {
        // Delete in chunks when a large array is passed.
        do {
          db_delete($this->bin)
            ->condition('cid', array_splice($cid, 0, 1000), 'IN')
            ->execute();
        } while (count($cid));
      }
      else {
        db_delete($this->bin)
          ->condition('cid', $cid)
          ->execute();
      }
    }
  }

  function isEmpty() {
    $this->garbageCollection();
    $query = db_select($this->bin);
    $query->addExpression('1');
    $result = $query->range(0, 1)
      ->execute()
      ->fetchField();
    return empty($result);
  }
}
?>