private function loadCacheMetaData()
    {
        if (isset($this->metaData)) {
            return;
        }

        $metaFile = $this->cacheDirectory . '/cache.meta';
        $this->metaData = array();

        if (file_exists($metaFile)) {
            $this->metaData = unserialize(file_get_contents($metaFile));
        }
    }