public function progress($downloadSize, $downloaded, $uploadSize, $uploaded, $handle = null)
    {
        $this->request->dispatch('curl.callback.progress', array(
            'request'       => $this->request,
            'handle'        => $handle,
            'download_size' => $downloadSize,
            'downloaded'    => $downloaded,
            'upload_size'   => $uploadSize,
            'uploaded'      => $uploaded
        ));
    }