PdxUnreadData internalReadUnreadFields(PdxUnreadData ud) {
    int[] unreadIndexes = generateUnreadDataFieldIndexes();
    if (unreadIndexes.length > 0) {
      UnreadPdxType unreadLocalPdxType =
          new UnreadPdxType(pdxReader.getPdxType(), unreadIndexes);
      tr.defineUnreadType(pdxClass, unreadLocalPdxType);
      ud.initialize(unreadLocalPdxType, pdxReader);
      return ud;
    } else {
      // Remember that this type does not have any unread data.
      UnreadPdxType unreadLocalPdxType = new UnreadPdxType(pdxReader.getPdxType(), null);
      tr.defineUnreadType(pdxClass, unreadLocalPdxType);
      return null;
    }
  }
Returns the indexes of the fields not read during deserialization.

@return the indexes of the unread fields
geode-core/src/main/java/org/apache/geode/pdx/internal/TrackingPdxReaderImpl.java