code: @Override
      public int getInContainerRowCount(BBContainer tupleData) {
          // according to TableOutputStream.cpp:TupleOutputStream::endRows() the row count is
          // at offset 4 (second integer)
          ByteBuffer bb = tupleData.b().duplicate();
          bb.position(getHeaderSize());
          bb.getInt(); // skip first four (partition id)
  
          return bb.getInt();
      }
docs: Get the row count if any, of the content wrapped in the given {@link BBContainer}
  @param tupleData
  @return the numbers of tuple data rows contained within a container