Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

3 files changed, 1215 insertions, 0 deletions

diff --git a/third_party/rust/mio-extras/src/channel.rs b/third_party/rust/mio-extras/src/channel.rs
new file mode 100644
index 0000000000..561317ecbf
--- /dev/null
+++ b/third_party/rust/mio-extras/src/channel.rs
@@ -0,0 +1,431 @@
+//! Thread safe communication channel implementing `Evented`
+use lazycell::{AtomicLazyCell, LazyCell};
+use mio::{Evented, Poll, PollOpt, Ready, Registration, SetReadiness, Token};
+use std::any::Any;
+use std::error;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::{mpsc, Arc};
+use std::{fmt, io};
+
+/// Creates a new asynchronous channel, where the `Receiver` can be registered
+/// with `Poll`.
+pub fn channel<T>() -> (Sender<T>, Receiver<T>) {
+    let (tx_ctl, rx_ctl) = ctl_pair();
+    let (tx, rx) = mpsc::channel();
+
+    let tx = Sender { tx, ctl: tx_ctl };
+
+    let rx = Receiver { rx, ctl: rx_ctl };
+
+    (tx, rx)
+}
+
+/// Creates a new synchronous, bounded channel where the `Receiver` can be
+/// registered with `Poll`.
+pub fn sync_channel<T>(bound: usize) -> (SyncSender<T>, Receiver<T>) {
+    let (tx_ctl, rx_ctl) = ctl_pair();
+    let (tx, rx) = mpsc::sync_channel(bound);
+
+    let tx = SyncSender { tx, ctl: tx_ctl };
+
+    let rx = Receiver { rx, ctl: rx_ctl };
+
+    (tx, rx)
+}
+
+fn ctl_pair() -> (SenderCtl, ReceiverCtl) {
+    let inner = Arc::new(Inner {
+        pending: AtomicUsize::new(0),
+        senders: AtomicUsize::new(1),
+        set_readiness: AtomicLazyCell::new(),
+    });
+
+    let tx = SenderCtl {
+        inner: Arc::clone(&inner),
+    };
+
+    let rx = ReceiverCtl {
+        registration: LazyCell::new(),
+        inner,
+    };
+
+    (tx, rx)
+}
+
+/// Tracks messages sent on a channel in order to update readiness.
+struct SenderCtl {
+    inner: Arc<Inner>,
+}
+
+/// Tracks messages received on a channel in order to track readiness.
+struct ReceiverCtl {
+    registration: LazyCell<Registration>,
+    inner: Arc<Inner>,
+}
+
+/// The sending half of a channel.
+pub struct Sender<T> {
+    tx: mpsc::Sender<T>,
+    ctl: SenderCtl,
+}
+
+/// The sending half of a synchronous channel.
+pub struct SyncSender<T> {
+    tx: mpsc::SyncSender<T>,
+    ctl: SenderCtl,
+}
+
+/// The receiving half of a channel.
+pub struct Receiver<T> {
+    rx: mpsc::Receiver<T>,
+    ctl: ReceiverCtl,
+}
+
+/// An error returned from the `Sender::send` or `SyncSender::send` function.
+pub enum SendError<T> {
+    /// An IO error.
+    Io(io::Error),
+
+    /// The receiving half of the channel has disconnected.
+    Disconnected(T),
+}
+
+/// An error returned from the `SyncSender::try_send` function.
+pub enum TrySendError<T> {
+    /// An IO error.
+    Io(io::Error),
+
+    /// Data could not be sent because it would require the callee to block.
+    Full(T),
+
+    /// The receiving half of the channel has disconnected.
+    Disconnected(T),
+}
+
+struct Inner {
+    // The number of outstanding messages for the receiver to read
+    pending: AtomicUsize,
+    // The number of sender handles
+    senders: AtomicUsize,
+    // The set readiness handle
+    set_readiness: AtomicLazyCell<SetReadiness>,
+}
+
+impl<T> Sender<T> {
+    /// Attempts to send a value on this channel, returning it back if it could not be sent.
+    pub fn send(&self, t: T) -> Result<(), SendError<T>> {
+        self.tx.send(t).map_err(SendError::from).and_then(|_| {
+            self.ctl.inc()?;
+            Ok(())
+        })
+    }
+}
+
+impl<T> Clone for Sender<T> {
+    fn clone(&self) -> Sender<T> {
+        Sender {
+            tx: self.tx.clone(),
+            ctl: self.ctl.clone(),
+        }
+    }
+}
+
+impl<T> SyncSender<T> {
+    /// Sends a value on this synchronous channel.
+    ///
+    /// This function will *block* until space in the internal buffer becomes
+    /// available or a receiver is available to hand off the message to.
+    pub fn send(&self, t: T) -> Result<(), SendError<T>> {
+        self.tx.send(t).map_err(From::from).and_then(|_| {
+            self.ctl.inc()?;
+            Ok(())
+        })
+    }
+
+    /// Attempts to send a value on this channel without blocking.
+    ///
+    /// This method differs from `send` by returning immediately if the channel's
+    /// buffer is full or no receiver is waiting to acquire some data.
+    pub fn try_send(&self, t: T) -> Result<(), TrySendError<T>> {
+        self.tx.try_send(t).map_err(From::from).and_then(|_| {
+            self.ctl.inc()?;
+            Ok(())
+        })
+    }
+}
+
+impl<T> Clone for SyncSender<T> {
+    fn clone(&self) -> SyncSender<T> {
+        SyncSender {
+            tx: self.tx.clone(),
+            ctl: self.ctl.clone(),
+        }
+    }
+}
+
+impl<T> Receiver<T> {
+    /// Attempts to return a pending value on this receiver without blocking.
+    pub fn try_recv(&self) -> Result<T, mpsc::TryRecvError> {
+        self.rx.try_recv().and_then(|res| {
+            let _ = self.ctl.dec();
+            Ok(res)
+        })
+    }
+}
+
+impl<T> Evented for Receiver<T> {
+    fn register(
+        &self,
+        poll: &Poll,
+        token: Token,
+        interest: Ready,
+        opts: PollOpt,
+    ) -> io::Result<()> {
+        self.ctl.register(poll, token, interest, opts)
+    }
+
+    fn reregister(
+        &self,
+        poll: &Poll,
+        token: Token,
+        interest: Ready,
+        opts: PollOpt,
+    ) -> io::Result<()> {
+        self.ctl.reregister(poll, token, interest, opts)
+    }
+
+    fn deregister(&self, poll: &Poll) -> io::Result<()> {
+        self.ctl.deregister(poll)
+    }
+}
+
+/*
+ *
+ * ===== SenderCtl / ReceiverCtl =====
+ *
+ */
+
+impl SenderCtl {
+    /// Call to track that a message has been sent
+    fn inc(&self) -> io::Result<()> {
+        let cnt = self.inner.pending.fetch_add(1, Ordering::Acquire);
+
+        if 0 == cnt {
+            // Toggle readiness to readable
+            if let Some(set_readiness) = self.inner.set_readiness.borrow() {
+                set_readiness.set_readiness(Ready::readable())?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl Clone for SenderCtl {
+    fn clone(&self) -> SenderCtl {
+        self.inner.senders.fetch_add(1, Ordering::Relaxed);
+        SenderCtl {
+            inner: Arc::clone(&self.inner),
+        }
+    }
+}
+
+impl Drop for SenderCtl {
+    fn drop(&mut self) {
+        if self.inner.senders.fetch_sub(1, Ordering::Release) == 1 {
+            let _ = self.inc();
+        }
+    }
+}
+
+impl ReceiverCtl {
+    fn dec(&self) -> io::Result<()> {
+        let first = self.inner.pending.load(Ordering::Acquire);
+
+        if first == 1 {
+            // Unset readiness
+            if let Some(set_readiness) = self.inner.set_readiness.borrow() {
+                set_readiness.set_readiness(Ready::empty())?;
+            }
+        }
+
+        // Decrement
+        let second = self.inner.pending.fetch_sub(1, Ordering::AcqRel);
+
+        if first == 1 && second > 1 {
+            // There are still pending messages. Since readiness was
+            // previously unset, it must be reset here
+            if let Some(set_readiness) = self.inner.set_readiness.borrow() {
+                set_readiness.set_readiness(Ready::readable())?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl Evented for ReceiverCtl {
+    fn register(
+        &self,
+        poll: &Poll,
+        token: Token,
+        interest: Ready,
+        opts: PollOpt,
+    ) -> io::Result<()> {
+        if self.registration.borrow().is_some() {
+            return Err(io::Error::new(
+                io::ErrorKind::Other,
+                "receiver already registered",
+            ));
+        }
+
+        let (registration, set_readiness) = Registration::new2();
+        poll.register(&registration, token, interest, opts)?;
+
+        if self.inner.pending.load(Ordering::Relaxed) > 0 {
+            // TODO: Don't drop readiness
+            let _ = set_readiness.set_readiness(Ready::readable());
+        }
+
+        self.registration
+            .fill(registration)
+            .expect("unexpected state encountered");
+        self.inner
+            .set_readiness
+            .fill(set_readiness)
+            .expect("unexpected state encountered");
+
+        Ok(())
+    }
+
+    fn reregister(
+        &self,
+        poll: &Poll,
+        token: Token,
+        interest: Ready,
+        opts: PollOpt,
+    ) -> io::Result<()> {
+        match self.registration.borrow() {
+            Some(registration) => poll.reregister(registration, token, interest, opts),
+            None => Err(io::Error::new(
+                io::ErrorKind::Other,
+                "receiver not registered",
+            )),
+        }
+    }
+
+    fn deregister(&self, poll: &Poll) -> io::Result<()> {
+        match self.registration.borrow() {
+            Some(registration) => poll.deregister(registration),
+            None => Err(io::Error::new(
+                io::ErrorKind::Other,
+                "receiver not registered",
+            )),
+        }
+    }
+}
+
+/*
+ *
+ * ===== Error conversions =====
+ *
+ */
+
+impl<T> From<mpsc::SendError<T>> for SendError<T> {
+    fn from(src: mpsc::SendError<T>) -> SendError<T> {
+        SendError::Disconnected(src.0)
+    }
+}
+
+impl<T> From<io::Error> for SendError<T> {
+    fn from(src: io::Error) -> SendError<T> {
+        SendError::Io(src)
+    }
+}
+
+impl<T> From<mpsc::TrySendError<T>> for TrySendError<T> {
+    fn from(src: mpsc::TrySendError<T>) -> TrySendError<T> {
+        match src {
+            mpsc::TrySendError::Full(v) => TrySendError::Full(v),
+            mpsc::TrySendError::Disconnected(v) => TrySendError::Disconnected(v),
+        }
+    }
+}
+
+impl<T> From<mpsc::SendError<T>> for TrySendError<T> {
+    fn from(src: mpsc::SendError<T>) -> TrySendError<T> {
+        TrySendError::Disconnected(src.0)
+    }
+}
+
+impl<T> From<io::Error> for TrySendError<T> {
+    fn from(src: io::Error) -> TrySendError<T> {
+        TrySendError::Io(src)
+    }
+}
+
+/*
+ *
+ * ===== Implement Error, Debug and Display for Errors =====
+ *
+ */
+
+impl<T: Any> error::Error for SendError<T> {
+    fn description(&self) -> &str {
+        match *self {
+            SendError::Io(ref io_err) => io_err.description(),
+            SendError::Disconnected(..) => "Disconnected",
+        }
+    }
+}
+
+impl<T: Any> error::Error for TrySendError<T> {
+    fn description(&self) -> &str {
+        match *self {
+            TrySendError::Io(ref io_err) => io_err.description(),
+            TrySendError::Full(..) => "Full",
+            TrySendError::Disconnected(..) => "Disconnected",
+        }
+    }
+}
+
+impl<T> fmt::Debug for SendError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        format_send_error(self, f)
+    }
+}
+
+impl<T> fmt::Display for SendError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        format_send_error(self, f)
+    }
+}
+
+impl<T> fmt::Debug for TrySendError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        format_try_send_error(self, f)
+    }
+}
+
+impl<T> fmt::Display for TrySendError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        format_try_send_error(self, f)
+    }
+}
+
+#[inline]
+fn format_send_error<T>(e: &SendError<T>, f: &mut fmt::Formatter) -> fmt::Result {
+    match *e {
+        SendError::Io(ref io_err) => write!(f, "{}", io_err),
+        SendError::Disconnected(..) => write!(f, "Disconnected"),
+    }
+}
+
+#[inline]
+fn format_try_send_error<T>(e: &TrySendError<T>, f: &mut fmt::Formatter) -> fmt::Result {
+    match *e {
+        TrySendError::Io(ref io_err) => write!(f, "{}", io_err),
+        TrySendError::Full(..) => write!(f, "Full"),
+        TrySendError::Disconnected(..) => write!(f, "Disconnected"),
+    }
+}
diff --git a/third_party/rust/mio-extras/src/lib.rs b/third_party/rust/mio-extras/src/lib.rs
new file mode 100644
index 0000000000..69a000556c
--- /dev/null
+++ b/third_party/rust/mio-extras/src/lib.rs
@@ -0,0 +1,33 @@
+//! Extra components for use with Mio.
+#![deny(missing_docs)]
+extern crate lazycell;
+extern crate mio;
+extern crate slab;
+
+#[macro_use]
+extern crate log;
+
+pub mod channel;
+pub mod timer;
+
+// Conversion utilities
+mod convert {
+    use std::time::Duration;
+
+    const NANOS_PER_MILLI: u32 = 1_000_000;
+    const MILLIS_PER_SEC: u64 = 1_000;
+
+    /// Convert a `Duration` to milliseconds, rounding up and saturating at
+    /// `u64::MAX`.
+    ///
+    /// The saturating is fine because `u64::MAX` milliseconds are still many
+    /// million years.
+    pub fn millis(duration: Duration) -> u64 {
+        // Round up.
+        let millis = (duration.subsec_nanos() + NANOS_PER_MILLI - 1) / NANOS_PER_MILLI;
+        duration
+            .as_secs()
+            .saturating_mul(MILLIS_PER_SEC)
+            .saturating_add(u64::from(millis))
+    }
+}
diff --git a/third_party/rust/mio-extras/src/timer.rs b/third_party/rust/mio-extras/src/timer.rs
new file mode 100644
index 0000000000..876026c99c
--- /dev/null
+++ b/third_party/rust/mio-extras/src/timer.rs
@@ -0,0 +1,751 @@
+//! Timer optimized for I/O related operations
+use crate::convert;
+use lazycell::LazyCell;
+use mio::{Evented, Poll, PollOpt, Ready, Registration, SetReadiness, Token};
+use slab::Slab;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+use std::{cmp, fmt, io, iter, thread, u64, usize};
+
+/// A timer.
+///
+/// Typical usage goes like this:
+///
+/// * register the timer with a `mio::Poll`.
+/// * set a timeout, by calling `Timer::set_timeout`.  Here you provide some
+///   state to be associated with this timeout.
+/// * poll the `Poll`, to learn when a timeout has occurred.
+/// * retrieve state associated with the timeout by calling `Timer::poll`.
+///
+/// You can omit use of the `Poll` altogether, if you like, and just poll the
+/// `Timer` directly.
+pub struct Timer<T> {
+    // Size of each tick in milliseconds
+    tick_ms: u64,
+    // Slab of timeout entries
+    entries: Slab<Entry<T>>,
+    // Timeout wheel. Each tick, the timer will look at the next slot for
+    // timeouts that match the current tick.
+    wheel: Vec<WheelEntry>,
+    // Tick 0's time instant
+    start: Instant,
+    // The current tick
+    tick: Tick,
+    // The next entry to possibly timeout
+    next: Token,
+    // Masks the target tick to get the slot
+    mask: u64,
+    // Set on registration with Poll
+    inner: LazyCell<Inner>,
+}
+
+/// Used to create a `Timer`.
+pub struct Builder {
+    // Approximate duration of each tick
+    tick: Duration,
+    // Number of slots in the timer wheel
+    num_slots: usize,
+    // Max number of timeouts that can be in flight at a given time.
+    capacity: usize,
+}
+
+/// A timeout, as returned by `Timer::set_timeout`.
+///
+/// Use this as the argument to `Timer::cancel_timeout`, to cancel this timeout.
+#[derive(Clone, Debug)]
+pub struct Timeout {
+    // Reference into the timer entry slab
+    token: Token,
+    // Tick that it should match up with
+    tick: u64,
+}
+
+struct Inner {
+    registration: Registration,
+    set_readiness: SetReadiness,
+    wakeup_state: WakeupState,
+    wakeup_thread: thread::JoinHandle<()>,
+}
+
+impl Drop for Inner {
+    fn drop(&mut self) {
+        // 1. Set wakeup state to TERMINATE_THREAD
+        self.wakeup_state.store(TERMINATE_THREAD, Ordering::Release);
+        // 2. Wake him up
+        self.wakeup_thread.thread().unpark();
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+struct WheelEntry {
+    next_tick: Tick,
+    head: Token,
+}
+
+// Doubly linked list of timer entries. Allows for efficient insertion /
+// removal of timeouts.
+struct Entry<T> {
+    state: T,
+    links: EntryLinks,
+}
+
+#[derive(Copy, Clone)]
+struct EntryLinks {
+    tick: Tick,
+    prev: Token,
+    next: Token,
+}
+
+type Tick = u64;
+
+const TICK_MAX: Tick = u64::MAX;
+
+// Manages communication with wakeup thread
+type WakeupState = Arc<AtomicUsize>;
+
+const TERMINATE_THREAD: usize = 0;
+const EMPTY: Token = Token(usize::MAX);
+
+impl Builder {
+    /// Set the tick duration.  Default is 100ms.
+    pub fn tick_duration(mut self, duration: Duration) -> Builder {
+        self.tick = duration;
+        self
+    }
+
+    /// Set the number of slots.  Default is 256.
+    pub fn num_slots(mut self, num_slots: usize) -> Builder {
+        self.num_slots = num_slots;
+        self
+    }
+
+    /// Set the capacity.  Default is 65536.
+    pub fn capacity(mut self, capacity: usize) -> Builder {
+        self.capacity = capacity;
+        self
+    }
+
+    /// Build a `Timer` with the parameters set on this `Builder`.
+    pub fn build<T>(self) -> Timer<T> {
+        Timer::new(
+            convert::millis(self.tick),
+            self.num_slots,
+            self.capacity,
+            Instant::now(),
+        )
+    }
+}
+
+impl Default for Builder {
+    fn default() -> Builder {
+        Builder {
+            tick: Duration::from_millis(100),
+            num_slots: 1 << 8,
+            capacity: 1 << 16,
+        }
+    }
+}
+
+impl<T> Timer<T> {
+    fn new(tick_ms: u64, num_slots: usize, capacity: usize, start: Instant) -> Timer<T> {
+        let num_slots = num_slots.next_power_of_two();
+        let capacity = capacity.next_power_of_two();
+        let mask = (num_slots as u64) - 1;
+        let wheel = iter::repeat(WheelEntry {
+            next_tick: TICK_MAX,
+            head: EMPTY,
+        })
+        .take(num_slots)
+        .collect();
+
+        Timer {
+            tick_ms,
+            entries: Slab::with_capacity(capacity),
+            wheel,
+            start,
+            tick: 0,
+            next: EMPTY,
+            mask,
+            inner: LazyCell::new(),
+        }
+    }
+
+    /// Set a timeout.
+    ///
+    /// When the timeout occurs, the given state becomes available via `poll`.
+    pub fn set_timeout(&mut self, delay_from_now: Duration, state: T) -> Timeout {
+        let delay_from_start = self.start.elapsed() + delay_from_now;
+        self.set_timeout_at(delay_from_start, state)
+    }
+
+    fn set_timeout_at(&mut self, delay_from_start: Duration, state: T) -> Timeout {
+        let mut tick = duration_to_tick(delay_from_start, self.tick_ms);
+        trace!(
+            "setting timeout; delay={:?}; tick={:?}; current-tick={:?}",
+            delay_from_start,
+            tick,
+            self.tick
+        );
+
+        // Always target at least 1 tick in the future
+        if tick <= self.tick {
+            tick = self.tick + 1;
+        }
+
+        self.insert(tick, state)
+    }
+
+    fn insert(&mut self, tick: Tick, state: T) -> Timeout {
+        // Get the slot for the requested tick
+        let slot = (tick & self.mask) as usize;
+        let curr = self.wheel[slot];
+
+        // Insert the new entry
+        let entry = Entry::new(state, tick, curr.head);
+        let token = Token(self.entries.insert(entry));
+
+        if curr.head != EMPTY {
+            // If there was a previous entry, set its prev pointer to the new
+            // entry
+            self.entries[curr.head.into()].links.prev = token;
+        }
+
+        // Update the head slot
+        self.wheel[slot] = WheelEntry {
+            next_tick: cmp::min(tick, curr.next_tick),
+            head: token,
+        };
+
+        self.schedule_readiness(tick);
+
+        trace!("inserted timout; slot={}; token={:?}", slot, token);
+
+        // Return the new timeout
+        Timeout { token, tick }
+    }
+
+    /// Cancel a timeout.
+    ///
+    /// If the timeout has not yet occurred, the return value holds the
+    /// associated state.
+    pub fn cancel_timeout(&mut self, timeout: &Timeout) -> Option<T> {
+        let links = match self.entries.get(timeout.token.into()) {
+            Some(e) => e.links,
+            None => return None,
+        };
+
+        // Sanity check
+        if links.tick != timeout.tick {
+            return None;
+        }
+
+        self.unlink(&links, timeout.token);
+        Some(self.entries.remove(timeout.token.into()).state)
+    }
+
+    /// Poll for an expired timer.
+    ///
+    /// The return value holds the state associated with the first expired
+    /// timer, if any.
+    pub fn poll(&mut self) -> Option<T> {
+        let target_tick = current_tick(self.start, self.tick_ms);
+        self.poll_to(target_tick)
+    }
+
+    fn poll_to(&mut self, mut target_tick: Tick) -> Option<T> {
+        trace!(
+            "tick_to; target_tick={}; current_tick={}",
+            target_tick,
+            self.tick
+        );
+
+        if target_tick < self.tick {
+            target_tick = self.tick;
+        }
+
+        while self.tick <= target_tick {
+            let curr = self.next;
+
+            trace!("ticking; curr={:?}", curr);
+
+            if curr == EMPTY {
+                self.tick += 1;
+
+                let slot = self.slot_for(self.tick);
+                self.next = self.wheel[slot].head;
+
+                // Handle the case when a slot has a single timeout which gets
+                // canceled before the timeout expires. In this case, the
+                // slot's head is EMPTY but there is a value for next_tick. Not
+                // resetting next_tick here causes the timer to get stuck in a
+                // loop.
+                if self.next == EMPTY {
+                    self.wheel[slot].next_tick = TICK_MAX;
+                }
+            } else {
+                let slot = self.slot_for(self.tick);
+
+                if curr == self.wheel[slot].head {
+                    self.wheel[slot].next_tick = TICK_MAX;
+                }
+
+                let links = self.entries[curr.into()].links;
+
+                if links.tick <= self.tick {
+                    trace!("triggering; token={:?}", curr);
+
+                    // Unlink will also advance self.next
+                    self.unlink(&links, curr);
+
+                    // Remove and return the token
+                    return Some(self.entries.remove(curr.into()).state);
+                } else {
+                    let next_tick = self.wheel[slot].next_tick;
+                    self.wheel[slot].next_tick = cmp::min(next_tick, links.tick);
+                    self.next = links.next;
+                }
+            }
+        }
+
+        // No more timeouts to poll
+        if let Some(inner) = self.inner.borrow() {
+            trace!("unsetting readiness");
+            let _ = inner.set_readiness.set_readiness(Ready::empty());
+
+            if let Some(tick) = self.next_tick() {
+                self.schedule_readiness(tick);
+            }
+        }
+
+        None
+    }
+
+    fn unlink(&mut self, links: &EntryLinks, token: Token) {
+        trace!(
+            "unlinking timeout; slot={}; token={:?}",
+            self.slot_for(links.tick),
+            token
+        );
+
+        if links.prev == EMPTY {
+            let slot = self.slot_for(links.tick);
+            self.wheel[slot].head = links.next;
+        } else {
+            self.entries[links.prev.into()].links.next = links.next;
+        }
+
+        if links.next != EMPTY {
+            self.entries[links.next.into()].links.prev = links.prev;
+
+            if token == self.next {
+                self.next = links.next;
+            }
+        } else if token == self.next {
+            self.next = EMPTY;
+        }
+    }
+
+    fn schedule_readiness(&self, tick: Tick) {
+        if let Some(inner) = self.inner.borrow() {
+            // Coordinate setting readiness w/ the wakeup thread
+            let mut curr = inner.wakeup_state.load(Ordering::Acquire);
+
+            loop {
+                if curr as Tick <= tick {
+                    // Nothing to do, wakeup is already scheduled
+                    return;
+                }
+
+                // Attempt to move the wakeup time forward
+                trace!("advancing the wakeup time; target={}; curr={}", tick, curr);
+                let actual =
+                    inner
+                        .wakeup_state
+                        .compare_and_swap(curr, tick as usize, Ordering::Release);
+
+                if actual == curr {
+                    // Signal to the wakeup thread that the wakeup time has
+                    // been changed.
+                    trace!("unparking wakeup thread");
+                    inner.wakeup_thread.thread().unpark();
+                    return;
+                }
+
+                curr = actual;
+            }
+        }
+    }
+
+    // Next tick containing a timeout
+    fn next_tick(&self) -> Option<Tick> {
+        if self.next != EMPTY {
+            let slot = self.slot_for(self.entries[self.next.into()].links.tick);
+
+            if self.wheel[slot].next_tick == self.tick {
+                // There is data ready right now
+                return Some(self.tick);
+            }
+        }
+
+        self.wheel.iter().map(|e| e.next_tick).min()
+    }
+
+    fn slot_for(&self, tick: Tick) -> usize {
+        (self.mask & tick) as usize
+    }
+}
+
+impl<T> Default for Timer<T> {
+    fn default() -> Timer<T> {
+        Builder::default().build()
+    }
+}
+
+impl<T> Evented for Timer<T> {
+    fn register(
+        &self,
+        poll: &Poll,
+        token: Token,
+        interest: Ready,
+        opts: PollOpt,
+    ) -> io::Result<()> {
+        if self.inner.borrow().is_some() {
+            return Err(io::Error::new(
+                io::ErrorKind::Other,
+                "timer already registered",
+            ));
+        }
+
+        let (registration, set_readiness) = Registration::new2();
+        poll.register(&registration, token, interest, opts)?;
+        let wakeup_state = Arc::new(AtomicUsize::new(usize::MAX));
+        let thread_handle = spawn_wakeup_thread(
+            Arc::clone(&wakeup_state),
+            set_readiness.clone(),
+            self.start,
+            self.tick_ms,
+        );
+
+        self.inner
+            .fill(Inner {
+                registration,
+                set_readiness,
+                wakeup_state,
+                wakeup_thread: thread_handle,
+            })
+            .expect("timer already registered");
+
+        if let Some(next_tick) = self.next_tick() {
+            self.schedule_readiness(next_tick);
+        }
+
+        Ok(())
+    }
+
+    fn reregister(
+        &self,
+        poll: &Poll,
+        token: Token,
+        interest: Ready,
+        opts: PollOpt,
+    ) -> io::Result<()> {
+        match self.inner.borrow() {
+            Some(inner) => poll.reregister(&inner.registration, token, interest, opts),
+            None => Err(io::Error::new(
+                io::ErrorKind::Other,
+                "receiver not registered",
+            )),
+        }
+    }
+
+    fn deregister(&self, poll: &Poll) -> io::Result<()> {
+        match self.inner.borrow() {
+            Some(inner) => poll.deregister(&inner.registration),
+            None => Err(io::Error::new(
+                io::ErrorKind::Other,
+                "receiver not registered",
+            )),
+        }
+    }
+}
+
+impl fmt::Debug for Inner {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("Inner")
+            .field("registration", &self.registration)
+            .field("wakeup_state", &self.wakeup_state.load(Ordering::Relaxed))
+            .finish()
+    }
+}
+
+fn spawn_wakeup_thread(
+    state: WakeupState,
+    set_readiness: SetReadiness,
+    start: Instant,
+    tick_ms: u64,
+) -> thread::JoinHandle<()> {
+    thread::spawn(move || {
+        let mut sleep_until_tick = state.load(Ordering::Acquire) as Tick;
+
+        loop {
+            if sleep_until_tick == TERMINATE_THREAD as Tick {
+                return;
+            }
+
+            let now_tick = current_tick(start, tick_ms);
+
+            trace!(
+                "wakeup thread: sleep_until_tick={:?}; now_tick={:?}",
+                sleep_until_tick,
+                now_tick
+            );
+
+            if now_tick < sleep_until_tick {
+                // Calling park_timeout with u64::MAX leads to undefined
+                // behavior in pthread, causing the park to return immediately
+                // and causing the thread to tightly spin. Instead of u64::MAX
+                // on large values, simply use a blocking park.
+                match tick_ms.checked_mul(sleep_until_tick - now_tick) {
+                    Some(sleep_duration) => {
+                        trace!(
+                            "sleeping; tick_ms={}; now_tick={}; sleep_until_tick={}; duration={:?}",
+                            tick_ms,
+                            now_tick,
+                            sleep_until_tick,
+                            sleep_duration
+                        );
+                        thread::park_timeout(Duration::from_millis(sleep_duration));
+                    }
+                    None => {
+                        trace!(
+                            "sleeping; tick_ms={}; now_tick={}; blocking sleep",
+                            tick_ms,
+                            now_tick
+                        );
+                        thread::park();
+                    }
+                }
+                sleep_until_tick = state.load(Ordering::Acquire) as Tick;
+            } else {
+                let actual =
+                    state.compare_and_swap(sleep_until_tick as usize, usize::MAX, Ordering::AcqRel)
+                        as Tick;
+
+                if actual == sleep_until_tick {
+                    trace!("setting readiness from wakeup thread");
+                    let _ = set_readiness.set_readiness(Ready::readable());
+                    sleep_until_tick = usize::MAX as Tick;
+                } else {
+                    sleep_until_tick = actual as Tick;
+                }
+            }
+        }
+    })
+}
+
+fn duration_to_tick(elapsed: Duration, tick_ms: u64) -> Tick {
+    // Calculate tick rounding up to the closest one
+    let elapsed_ms = convert::millis(elapsed);
+    elapsed_ms.saturating_add(tick_ms / 2) / tick_ms
+}
+
+fn current_tick(start: Instant, tick_ms: u64) -> Tick {
+    duration_to_tick(start.elapsed(), tick_ms)
+}
+
+impl<T> Entry<T> {
+    fn new(state: T, tick: u64, next: Token) -> Entry<T> {
+        Entry {
+            state,
+            links: EntryLinks {
+                tick,
+                prev: EMPTY,
+                next,
+            },
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use std::time::{Duration, Instant};
+
+    #[test]
+    pub fn test_timeout_next_tick() {
+        let mut t = timer();
+        let mut tick;
+
+        t.set_timeout_at(Duration::from_millis(100), "a");
+
+        tick = ms_to_tick(&t, 50);
+        assert_eq!(None, t.poll_to(tick));
+
+        tick = ms_to_tick(&t, 100);
+        assert_eq!(Some("a"), t.poll_to(tick));
+        assert_eq!(None, t.poll_to(tick));
+
+        tick = ms_to_tick(&t, 150);
+        assert_eq!(None, t.poll_to(tick));
+
+        tick = ms_to_tick(&t, 200);
+        assert_eq!(None, t.poll_to(tick));
+
+        assert_eq!(count(&t), 0);
+    }
+
+    #[test]
+    pub fn test_clearing_timeout() {
+        let mut t = timer();
+        let mut tick;
+
+        let to = t.set_timeout_at(Duration::from_millis(100), "a");
+        assert_eq!("a", t.cancel_timeout(&to).unwrap());
+
+        tick = ms_to_tick(&t, 100);
+        assert_eq!(None, t.poll_to(tick));
+
+        tick = ms_to_tick(&t, 200);
+        assert_eq!(None, t.poll_to(tick));
+
+        assert_eq!(count(&t), 0);
+    }
+
+    #[test]
+    pub fn test_multiple_timeouts_same_tick() {
+        let mut t = timer();
+        let mut tick;
+
+        t.set_timeout_at(Duration::from_millis(100), "a");
+        t.set_timeout_at(Duration::from_millis(100), "b");
+
+        let mut rcv = vec![];
+
+        tick = ms_to_tick(&t, 100);
+        rcv.push(t.poll_to(tick).unwrap());
+        rcv.push(t.poll_to(tick).unwrap());
+
+        assert_eq!(None, t.poll_to(tick));
+
+        rcv.sort();
+        assert!(rcv == ["a", "b"], "actual={:?}", rcv);
+
+        tick = ms_to_tick(&t, 200);
+        assert_eq!(None, t.poll_to(tick));
+
+        assert_eq!(count(&t), 0);
+    }
+
+    #[test]
+    pub fn test_multiple_timeouts_diff_tick() {
+        let mut t = timer();
+        let mut tick;
+
+        t.set_timeout_at(Duration::from_millis(110), "a");
+        t.set_timeout_at(Duration::from_millis(220), "b");
+        t.set_timeout_at(Duration::from_millis(230), "c");
+        t.set_timeout_at(Duration::from_millis(440), "d");
+        t.set_timeout_at(Duration::from_millis(560), "e");
+
+        tick = ms_to_tick(&t, 100);
+        assert_eq!(Some("a"), t.poll_to(tick));
+        assert_eq!(None, t.poll_to(tick));
+
+        tick = ms_to_tick(&t, 200);
+        assert_eq!(Some("c"), t.poll_to(tick));
+        assert_eq!(Some("b"), t.poll_to(tick));
+        assert_eq!(None, t.poll_to(tick));
+
+        tick = ms_to_tick(&t, 300);
+        assert_eq!(None, t.poll_to(tick));
+
+        tick = ms_to_tick(&t, 400);
+        assert_eq!(Some("d"), t.poll_to(tick));
+        assert_eq!(None, t.poll_to(tick));
+
+        tick = ms_to_tick(&t, 500);
+        assert_eq!(None, t.poll_to(tick));
+
+        tick = ms_to_tick(&t, 600);
+        assert_eq!(Some("e"), t.poll_to(tick));
+        assert_eq!(None, t.poll_to(tick));
+    }
+
+    #[test]
+    pub fn test_catching_up() {
+        let mut t = timer();
+
+        t.set_timeout_at(Duration::from_millis(110), "a");
+        t.set_timeout_at(Duration::from_millis(220), "b");
+        t.set_timeout_at(Duration::from_millis(230), "c");
+        t.set_timeout_at(Duration::from_millis(440), "d");
+
+        let tick = ms_to_tick(&t, 600);
+        assert_eq!(Some("a"), t.poll_to(tick));
+        assert_eq!(Some("c"), t.poll_to(tick));
+        assert_eq!(Some("b"), t.poll_to(tick));
+        assert_eq!(Some("d"), t.poll_to(tick));
+        assert_eq!(None, t.poll_to(tick));
+    }
+
+    #[test]
+    pub fn test_timeout_hash_collision() {
+        let mut t = timer();
+        let mut tick;
+
+        t.set_timeout_at(Duration::from_millis(100), "a");
+        t.set_timeout_at(Duration::from_millis(100 + TICK * SLOTS as u64), "b");
+
+        tick = ms_to_tick(&t, 100);
+        assert_eq!(Some("a"), t.poll_to(tick));
+        assert_eq!(1, count(&t));
+
+        tick = ms_to_tick(&t, 200);
+        assert_eq!(None, t.poll_to(tick));
+        assert_eq!(1, count(&t));
+
+        tick = ms_to_tick(&t, 100 + TICK * SLOTS as u64);
+        assert_eq!(Some("b"), t.poll_to(tick));
+        assert_eq!(0, count(&t));
+    }
+
+    #[test]
+    pub fn test_clearing_timeout_between_triggers() {
+        let mut t = timer();
+        let mut tick;
+
+        let a = t.set_timeout_at(Duration::from_millis(100), "a");
+        let _ = t.set_timeout_at(Duration::from_millis(100), "b");
+        let _ = t.set_timeout_at(Duration::from_millis(200), "c");
+
+        tick = ms_to_tick(&t, 100);
+        assert_eq!(Some("b"), t.poll_to(tick));
+        assert_eq!(2, count(&t));
+
+        t.cancel_timeout(&a);
+        assert_eq!(1, count(&t));
+
+        assert_eq!(None, t.poll_to(tick));
+
+        tick = ms_to_tick(&t, 200);
+        assert_eq!(Some("c"), t.poll_to(tick));
+        assert_eq!(0, count(&t));
+    }
+
+    const TICK: u64 = 100;
+    const SLOTS: usize = 16;
+    const CAPACITY: usize = 32;
+
+    fn count<T>(timer: &Timer<T>) -> usize {
+        timer.entries.len()
+    }
+
+    fn timer() -> Timer<&'static str> {
+        Timer::new(TICK, SLOTS, CAPACITY, Instant::now())
+    }
+
+    fn ms_to_tick<T>(timer: &Timer<T>, ms: u64) -> u64 {
+        ms / timer.tick_ms
+    }
+}