code: public void add(int deltaHi, int deltaLo) {
          while (true) {
              long encoded = get();
              long update = encode(getHi(encoded) + deltaHi, getLo(encoded) + deltaLo);
              if (compareAndSet(encoded, update))
                  return;
          }
      }
docs: Atomically adds the given deltas to the current hi and lo values.
  
  @param deltaHi the delta to apply to the hi value
  @param deltaLo the delta to apply to the lo value