Method nextMsgNoTimeout

nats.go:5429–5485

nextMsgNoTimeout works similarly to Subscription.NextMsg() but will not time out. It is only used internally for non-timeout subscription iterator.

()

// nextMsgNoTimeout works similarly to Subscription.NextMsg() but will not
// time out. It is only used internally for non-timeout subscription iterator.
func (s *Subscription) nextMsgNoTimeout() (*Msg, error) {
	if s == nil {
		return nil, ErrBadSubscription
	}

	s.mu.Lock()
	err := s.validateNextMsgState(false)
	if err != nil {
		s.mu.Unlock()
		return nil, err
	}

	// snapshot
	mch := s.mch
	s.mu.Unlock()

	var ok bool
	var msg *Msg

	// If something is available right away, let's optimize that case.
	select {
	case msg, ok = <-mch:
		if !ok {
			return nil, s.getNextMsgErr()
		}
		if err := s.processNextMsgDelivered(msg); err != nil {
			return nil, err
		} else {
			return msg, nil
		}
	default:
	}

	if s.errCh != nil {
		select {
		case msg, ok = <-mch:
			if !ok {
				return nil, s.getNextMsgErr()
			}
			if err := s.processNextMsgDelivered(msg); err != nil {
				return nil, err
			}
		case err := <-s.errCh:
			return nil, err
		}
	} else {
		msg, ok = <-mch
		if !ok {
			return nil, s.getNextMsgErr()
		}
		if err := s.processNextMsgDelivered(msg); err != nil {
			return nil, err
		}
	}

	return msg, nil
}