NewQueue create a Queue that will store segments in dir and that will consume no more than maxSize on disk.

MaxWritesPending is the number of writes that can be pending at any given time.

Possible errors returned by a queue.

Possible errors returned by a queue.

Possible errors returned by a queue.

Possible errors returned by a queue.

Queue is a bounded, disk-backed, append-only type that combines Queue and log semantics.

SharedCount manages an integer value, which can be read/written concurrently.