pub(super) struct ThreadOwners {
    table: Table<Backend, 16>,
    hardware: Rc<RefCell<Hardware>>,
    next: u64,
}
impl ThreadOwners {
    pub(super) fn new() -> Self {
        let (table, hardware) = setup();
        Self {
            table,
            hardware,
            next: 0,
        }
    }
    pub(super) fn create(&mut self) -> ThreadId {
        let id = spawn(&mut self.table, self.next);
        self.next += 1;
        id
    }
    pub(super) fn record(&self, id: ThreadId) -> ThreadRecord {
        self.table.record(id).unwrap()
    }
    pub(super) fn activate(&mut self, id: ThreadId) {
        enter(&mut self.table, &self.hardware, id);
    }
    pub(super) fn yield_current(&mut self, id: ThreadId) {
        self.table.yield_current(id).unwrap();
        self.hardware.borrow_mut().sp = 0;
    }
    pub(super) fn exit(&mut self, id: ThreadId) {
        if self.record(id).state == State::Running {
            self.table.exit_current(id).unwrap();
            self.hardware.borrow_mut().sp = 0;
        } else {
            self.table.cancel(id).unwrap();
        }
    }
    pub(super) fn reap(&mut self, id: ThreadId) {
        if self.record(id).state != State::Dead {
            self.exit(id);
        }
        self.table.reap(id).unwrap();
    }
    pub(super) fn live(&self) -> usize {
        self.table.snapshot().live
    }
}