code: public void putDocumentInCache(int n, Source source)
    {
  
      int cachedNode = getNode(source);
  
      if (DTM.NULL != cachedNode)
      {
        if (!(cachedNode == n))
          throw new RuntimeException(
            "Programmer's Error!  "
            + "putDocumentInCache found reparse of doc: "
            + source.getSystemId());
        return;
      }
      if (null != source.getSystemId())
      {
        m_sourceTree.addElement(new SourceTree(n, source.getSystemId()));
      }
    }
docs: Put the source tree root node in the document cache.
  TODO: This function needs to be a LOT more sophisticated.
  
  @param n The node to cache.
  @param source The Source object to cache.