Struct TimerQueue 

pub struct TimerQueue<K, I = Instant> { /* private fields */ }

Pending timers, earliest first.

Cancellation does not remove from the middle of the heap. Each key carries a generation counter; setting or clearing bumps it, and an entry whose generation is stale is discarded when it surfaces. Cancellation is common — every response cancels something — so making it O(1) and paying at pop time is the right trade.

Implementations

impl<K: Clone + Eq + Hash, I: Ord + Copy + Add<Duration, Output = I>> TimerQueue<K, I>

pub fn new() -> Self

An empty queue.

pub fn len(&self) -> usize

How many entries are held, including stale ones not yet discarded.

pub fn is_empty(&self) -> bool

Whether nothing is scheduled.

pub fn set(&mut self, key: K, now: I, after: Duration)

Schedule a timer for after from now, replacing any previous instance of the same key.

now is the caller’s, not this queue’s. That is the whole difference between a queue a tokio driver can use and one that any driver can: a caller on virtual time hands its own clock in, and nothing here has an opinion about what an instant means.

pub fn clear(&mut self, key: &K)

Cancel a timer.

pub fn forget(&mut self, key: &K)

Forget one timer key and its generation counter.

The heap entry, if any, becomes stale and is discarded when it reaches the front. This is the constant-time termination path for callers that can enumerate their small timer set; Self::forget_matching remains the general full-map operation.

pub fn clear_matching(&mut self, matches: impl Fn(&K) -> bool)

Cancel every timer whose key matches.

The general form of “cancel everything belonging to this transaction”, which is what termination means — expressed as a predicate because the queue does not know what part of a key identifies a transaction.

pub fn next_deadline(&mut self) -> Option<I>

When the next live timer is due, if any.

Discards stale entries as it looks, so a queue full of cancelled timers does not keep waking the loop.

pub fn take_due(&mut self, now: I) -> Vec<K>

Take every timer due at or before now, earliest first.

pub fn forget_matching(&mut self, matches: impl Fn(&K) -> bool)

Forget every key that matches, generation counters and all.

Trait Implementations

impl<K: Debug, I: Debug> Debug for TimerQueue<K, I>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<K: Eq, I: Ord> Default for TimerQueue<K, I>

fn default() -> Self

Returns the “default value” for a type.