docs: private void deliverUnsafe() {
      // Try to acquire the lock
      if (lock.getAndIncrement() != 0) {
        return;
      }
  
      do {
        // Optimization: the inner loop will eager process any accumulated state, so reset the lock
        // for just this iteration. (If another event occurs during processing, it can increment the
        // lock to enqueue another iteration).
        lock.lazySet(1);
  
        // Process the upstream message if one exists.
        pollUpstream();
  
        // Eagerly notify of onComplete/onError disregarding demand.
        // NOTE: this will purposely leave wip set to avoid further deliveries.
        if (maybeFinish()) {
          return;
        }
  
        // Deliver as many messages as possible
        int demandSnapshot = numRequested.get();
        int delivered = 0;
  
        while (delivered < demandSnapshot) {
          // Deliver a message if we can
          if (reframer.hasFullFrame()) {
            delivered++;
            outerResponseObserver.onResponse(reframer.pop());
          } else {
            // Otherwise request more from upstream (if we haven't done so already)
            if (!awaitingInner) {
              awaitingInner = true;
              innerController.request(1);
            }
            break;
          }
  
          if (maybeFinish()) {
            return;
          }
        }
  
        // update the counter in bulk
        if (delivered != 0) {
          numRequested.addAndGet(-delivered);
        }
      } while (lock.decrementAndGet() != 0);
    }