Module pump 

The task that feeds frames of the stream to a core and the events of the core to the emitter.

Functions

drain_backlog

Waits until the emitter has nothing buffered, or deadline has passed.

run_pump

Reads frames from rx until cancel, runs them through core, and gives the events to emitter. after runs after every frame with the core locked out, so a connector can act on what the core noted (a book to ask for again).