uber 开源的限流算法，代码不多，尝试理解但是没怎么理解。有没有大佬指点一二.主要不理解的点在于这个 for 循环

// Take blocks to ensure that the time spent between multiple // Take calls is on average time.Second/rate. func (t *limiter) Take() time.Time {  newState := state{}  taken := false  for !taken {   now := t.clock.Now()    previousStatePointer := atomic.LoadPointer(&t.state)   oldState := (*state)(previousStatePointer)    newState = state{}   newState.last = now    // If this is our first request, then we allow it.   if oldState.last.IsZero() {    taken = atomic.CompareAndSwapPointer(&t.state, previousStatePointer, unsafe.Pointer(&newState))    continue   }    // sleepFor calculates how much time we should sleep based on   // the perRequest budget and how long the last request took.   // Since the request may take longer than the budget, this number   // can get negative, and is summed across requests.   newState.sleepFor += t.perRequest - now.Sub(oldState.last)   // We shouldn't allow sleepFor to get too negative, since it would mean that   // a service that slowed down a lot for a short period of time would get   // a much higher RPS following that.   if newState.sleepFor < t.maxSlack {    newState.sleepFor = t.maxSlack   }   if newState.sleepFor > 0 {    newState.last = newState.last.Add(newState.sleepFor)   }   taken = atomic.CompareAndSwapPointer(&t.state, previousStatePointer, unsafe.Pointer(&newState))  }  t.clock.Sleep(newState.sleepFor)  return newState.last }