dope-runtime 0.2.1

Thin io_uring adaptor with "Manifolds"
Documentation 
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use std::cmp::Reverse;
use std::collections::{BinaryHeap, HashMap};
use std::{task::Waker, time::Instant};

use dambi::LocalCell;

pub(crate) struct TimerHeap {
    inner: LocalCell<TimerHeapInner>,
}

struct TimerHeapInner {
    next_id: u64,
    heap: BinaryHeap<Reverse<(Instant, u64)>>,
    entries: HashMap<u64, TimerEntry>,
}

struct TimerEntry {
    deadline: Instant,
    waker: Option<Waker>,
}

impl TimerHeap {
    pub(crate) fn new() -> Self {
        Self {
            inner: LocalCell::new(TimerHeapInner {
                next_id: 1,
                heap: BinaryHeap::new(),
                entries: HashMap::new(),
            }),
        }
    }

    pub(crate) fn register(&self, id: Option<u64>, deadline: Instant, waker: &Waker) -> u64 {
        let inner = self.inner.get_mut();

        if let Some(id) = id
            && let Some(ent) = inner.entries.get_mut(&id)
        {
            ent.deadline = deadline;
            ent.waker = Some(waker.clone());
            inner.heap.push(Reverse((deadline, id)));
            return id;
        }

        let id = inner.next_id;
        inner.next_id = inner.next_id.wrapping_add(1);

        inner.entries.insert(
            id,
            TimerEntry {
                deadline,
                waker: Some(waker.clone()),
            },
        );
        inner.heap.push(Reverse((deadline, id)));
        id
    }

    pub(crate) fn cancel(&self, id: u64) {
        let inner = self.inner.get_mut();
        let _ = inner.entries.remove(&id);
    }

    pub(crate) fn wake_due(&self) {
        let inner = self.inner.get_mut();
        if inner.heap.is_empty() {
            return;
        }
        let now = Instant::now();
        while let Some(Reverse((deadline, id))) = inner.heap.peek().copied() {
            if deadline > now {
                break;
            }
            let _ = inner.heap.pop();
            let Some(ent) = inner.entries.get(&id) else {
                continue;
            };
            if ent.deadline != deadline {
                continue;
            }
            let ent = inner.entries.remove(&id);
            if let Some(ent) = ent
                && let Some(w) = ent.waker
            {
                w.wake();
            }
        }
    }

    pub(crate) fn next_deadline(&self) -> Option<Instant> {
        let inner = self.inner.get_mut();
        loop {
            let Reverse((deadline, id)) = inner.heap.peek().copied()?;
            let Some(ent) = inner.entries.get(&id) else {
                let _ = inner.heap.pop();
                continue;
            };
            if ent.deadline == deadline {
                return Some(deadline);
            }
            let _ = inner.heap.pop();
        }
    }
}