s read structures in j_decompress_ptr object passed as *p.
        This object is used by libjpeg for JPEG data reading from datastream.
        <p>Returns -1 on error and 0 on success.</p>
      </dd>
    </dl>
    <p><a name="datastream_methods_other"></a></p>
    <h5>Other methods</h5>
    <p>This group of methods includes several supplementary calls. These calls
      are used to temporary switch to another data stream (file and/or memory
      buffer).</p>
    <dl>
      <dt><strong>virtual const char*