code: public void purge(int gcBefore)
      {
          int j = 0;
          for (int i = 0; i < size; i++)
          {
              if (delTimes[i] >= gcBefore)
                  setInternal(j++, starts[i], ends[i], markedAts[i], delTimes[i]);
          }
          size = j;
      }
docs: Removes all range tombstones whose local deletion time is older than gcBefore.