@Override
  public PdxUnreadFields readUnreadFields() {
    PdxUnreadData result = new PdxUnreadData();
    setReadUnreadFieldsCalled(result);
    return result;
  }
@param idx of the variable length field
@return the offset to the variable length field
geode-core/src/main/java/org/apache/geode/pdx/internal/PdxReaderImpl.java