func()

in semaphore/semaphore.go [40:83]

• 36 lines of code
• 9 McCabe index (conditional complexity)

func (s *Weighted) Acquire(ctx context.Context, n int64) error {
	s.mu.Lock()
	if s.size-s.cur >= n && s.waiters.Len() == 0 {
		s.cur += n
		s.mu.Unlock()
		return nil
	}

	if n > s.size {
		// Don't make other Acquire calls block on one that's doomed to fail.
		s.mu.Unlock()
		<-ctx.Done()
		return ctx.Err()
	}

	ready := make(chan struct{})
	w := waiter{n: n, ready: ready}
	elem := s.waiters.PushBack(w)
	s.mu.Unlock()

	select {
	case <-ctx.Done():
		err := ctx.Err()
		s.mu.Lock()
		select {
		case <-ready:
			// Acquired the semaphore after we were canceled.  Rather than trying to
			// fix up the queue, just pretend we didn't notice the cancelation.
			err = nil
		default:
			isFront := s.waiters.Front() == elem
			s.waiters.Remove(elem)
			// If we're at the front and there're extra tokens left, notify other waiters.
			if isFront && s.size > s.cur {
				s.notifyWaiters()
			}
		}
		s.mu.Unlock()
		return err

	case <-ready:
		return nil
	}
}