code: public static DTDSubset readInternalSubset(WstxInputData srcData,
                                                 WstxInputSource input,
                                                 ReaderConfig cfg,
                                                 boolean constructFully,
                                                 int xmlVersion)
          throws XMLStreamException
      {
          FullDTDReader r = new FullDTDReader(input, cfg, constructFully, xmlVersion);
          // Need to read using the same low-level reader interface:
          r.copyBufferStateFrom(srcData);
          DTDSubset ss;
  
          try {
              ss = r.parseDTD();
          } finally {
              /* And then need to restore changes back to owner (line nrs etc);
               * effectively means that we'll stop reading external DTD subset,
               * if so.
               */
              srcData.copyBufferStateFrom(r);
          }
          return ss;
      }
docs: Method called to read in the internal subset definition.