Struct Reading 

struct Reading {
    subject: Subject,
    frames: Vec<SeatUpdate>,
    _task: AbortOnDrop,
}

The subscribe read this connection is waiting on, and what arrived for it while it ran.

A read off the loop cannot let its seat’s updates overtake its record. The record is encoded while those frames are already in flight, so they are held here and handed on after the snapshot: a frame is never drawn over a page that has not arrived. The seq each carries is what tells the client which the snapshot already covers.

Fields

subject: Subject

frames: Vec<SeatUpdate>

_task: AbortOnDrop

Held for its drop: dropping the reading aborts the task, which is what a release and the end of the connection both do.