LibRaw expects more
        data) or a positive number equal to the file position (bytes from file
        beginning) where the unpacking error occurred.</li>
    </ul>
    <p>The callback function is intended for information purposes: it notifies
      the user or the program code that processing is impossible.</p>
    <p>If the user does not set his or her own handler, the standard one (output
      of error message in stderr) will be used.</p>
    <p>One can set the null handler by passing NULL to set_da