Order by time without duplicates

Order by time.cpp

inline int64_t get_monotonous_click() {
  static std::atomic<int64_t> last_click{0};

  int64_t timestamp{
    std::chrono::system_clock::now().time_since_epoch()
      / std::chrono::microseconds(1)};
  int64_t old_click{last_click.load()};
  int64_t new_click{0};
  do {
    new_click = std::max(timestamp, old_click + 1);
  } while (!std::atomic_compare_exchange_weak(
             &last_click, &old_click, new_click));
  return new_click;
}