code: public static void skipInternalSubset(WstxInputData srcData, WstxInputSource input,
                                            ReaderConfig cfg)
          throws XMLStreamException
      {
          MinimalDTDReader r = new MinimalDTDReader(input, cfg);
          // Need to read from same source as the master (owning stream reader)
          r.copyBufferStateFrom(srcData);
          try {
              r.skipInternalSubset();
          } finally {
              /* And then need to restore changes back to srcData (line nrs etc);
               * effectively means that we'll stop reading internal DTD subset,
               * if so.
               */
              srcData.copyBufferStateFrom(r);
          }
      }
docs: Method that just skims
  through structure of internal subset, but without doing any sort
  of validation, or parsing of contents. Method may still throw an
  exception, if skipping causes EOF or there's an I/O problem.
  
  @param srcData Link back to the input buffer shared with the owning
  stream reader.