[rabbitmq-discuss] Are there any unused delivery tag values?

[Lowell.Boggs at emc.com]

Delivery tags are uint64_t data.

Is zero a valid delivery tag?  Is (uint64_t)(-1)?

I'm interested in knowing whether I need to keep extra bools laying around to keep track of the "has been auto-acked" or not flag.

Thanks,
   Lowell