upload file to amazon S3 and CI upload class

Code:
function s3(){



    $config['upload_path'] = $_SERVER["DOCUMENT_ROOT"].'/temp/';

    $config['allowed_types'] = 'gif|jpg|png';

    $config['max_size'] = '1000000';

    $config['max_width']  = '1024000';

    $config['max_height']  = '768000';



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



    if ( ! $this->upload->do_upload())

    {

        $error = array('error' => $this->upload->display_errors());



        print_r($error);

        echo 'failure';

    }

    else

    {

       $data = array('upload_data' => $this->upload->data()); 

        $fn = $data['file_name'];

        $type = substr($fn, strrpos($fn, '.') + 1);



    $this->load->library('s3');

    $temp_file_path = $_SERVER["DOCUMENT_ROOT"]."/temp/" . $data['file_name'];

    $contents = read_file($temp_file_path); // will this blow up or timeout for large files?! 

    $newFileName = uniqid().".".substr($temp_file_path, strrpos($temp_file_path, '.') + 1);

     $contentPath = "mysite.com/Images"; 



    $this->s3->putObject($newFileName, $contents, $contentPath, 'private', $type);

    echo 'success';

    }

}