code: protected void writeReference(long offset, Object reference) {
          assert referenceMessageSize != 0 : "References are not in use";
          // Is there a way to compute the element offset once and just
          // arithmetic?
          UnsafeRefArrayAccess.spElement(references, UnsafeRefArrayAccess.calcElementOffset(offset), reference);
      }
docs: Write a reference to the given position
  @param offset index into the reference array
  @param reference