Codeigniter upload file name

Usually we can get the form data in Codeigniter by using $this->input->get('field_name') or $this->input->post('field_name') and that's fine.

In raw PHP we use $_FILES["fileToUpload"]["name"] to get the file name that the user trying to upload.

My question is: Is there any Codeigniter way to get the name of the file that needs to be uploaded?

I am trying to say that i need to get the file name that the user is trying to upload before trying to save it in my server using Codeigniter library instead of using raw PHP global $_FILES variable.

<?php

class Upload extends CI_Controller {

        public function __construct()
        {
                parent::__construct();
                $this->load->helper(array('form', 'url'));
        }

        public function index()
        {
                $this->load->view('upload_form', array('error' => ' ' ));
        }

        public function do_upload()
        {
                $config['upload_path']          = './uploads/';
                $config['allowed_types']        = 'gif|jpg|png';
                $config['max_size']             = 100;
                $config['max_width']            = 1024;
                $config['max_height']           = 768;

                $this->load->library('upload', $config);

                // get the user submitted file name here

                if ( ! $this->upload->do_upload('userfile'))
                {
                        $error = array('error' => $this->upload->display_errors());

                        $this->load->view('upload_form', $error);
                }
                else
                {
                        $data = array('upload_data' => $this->upload->data());

                        $this->load->view('upload_success', $data);
                }
        }
}
?>