diff --git a/src/channel.rs b/src/channel.rs
new file mode 100644
index 0000000..ebcd652
--- /dev/null
+++ b/src/channel.rs
@@ -0,0 +1,1510 @@
+//! The channel interface.
+
+use std::fmt;
+use std::iter::FusedIterator;
+use std::mem;
+use std::panic::{RefUnwindSafe, UnwindSafe};
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+
+use crate::context::Context;
+use crate::counter;
+use crate::err::{
+    RecvError, RecvTimeoutError, SendError, SendTimeoutError, TryRecvError, TrySendError,
+};
+use crate::flavors;
+use crate::select::{Operation, SelectHandle, Token};
+
+/// Creates a channel of unbounded capacity.
+///
+/// This channel has a growable buffer that can hold any number of messages at a time.
+///
+/// # Examples
+///
+/// ```
+/// use std::thread;
+/// use crossbeam_channel::unbounded;
+///
+/// let (s, r) = unbounded();
+///
+/// // Computes the n-th Fibonacci number.
+/// fn fib(n: i32) -> i32 {
+///     if n <= 1 {
+///         n
+///     } else {
+///         fib(n - 1) + fib(n - 2)
+///     }
+/// }
+///
+/// // Spawn an asynchronous computation.
+/// thread::spawn(move || s.send(fib(20)).unwrap());
+///
+/// // Print the result of the computation.
+/// println!("{}", r.recv().unwrap());
+/// ```
+pub fn unbounded<T>() -> (Sender<T>, Receiver<T>) {
+    let (s, r) = counter::new(flavors::list::Channel::new());
+    let s = Sender {
+        flavor: SenderFlavor::List(s),
+    };
+    let r = Receiver {
+        flavor: ReceiverFlavor::List(r),
+    };
+    (s, r)
+}
+
+/// Creates a channel of bounded capacity.
+///
+/// This channel has a buffer that can hold at most `cap` messages at a time.
+///
+/// A special case is zero-capacity channel, which cannot hold any messages. Instead, send and
+/// receive operations must appear at the same time in order to pair up and pass the message over.
+///
+/// # Examples
+///
+/// A channel of capacity 1:
+///
+/// ```
+/// use std::thread;
+/// use std::time::Duration;
+/// use crossbeam_channel::bounded;
+///
+/// let (s, r) = bounded(1);
+///
+/// // This call returns immediately because there is enough space in the channel.
+/// s.send(1).unwrap();
+///
+/// thread::spawn(move || {
+///     // This call blocks the current thread because the channel is full.
+///     // It will be able to complete only after the first message is received.
+///     s.send(2).unwrap();
+/// });
+///
+/// thread::sleep(Duration::from_secs(1));
+/// assert_eq!(r.recv(), Ok(1));
+/// assert_eq!(r.recv(), Ok(2));
+/// ```
+///
+/// A zero-capacity channel:
+///
+/// ```
+/// use std::thread;
+/// use std::time::Duration;
+/// use crossbeam_channel::bounded;
+///
+/// let (s, r) = bounded(0);
+///
+/// thread::spawn(move || {
+///     // This call blocks the current thread until a receive operation appears
+///     // on the other side of the channel.
+///     s.send(1).unwrap();
+/// });
+///
+/// thread::sleep(Duration::from_secs(1));
+/// assert_eq!(r.recv(), Ok(1));
+/// ```
+pub fn bounded<T>(cap: usize) -> (Sender<T>, Receiver<T>) {
+    if cap == 0 {
+        let (s, r) = counter::new(flavors::zero::Channel::new());
+        let s = Sender {
+            flavor: SenderFlavor::Zero(s),
+        };
+        let r = Receiver {
+            flavor: ReceiverFlavor::Zero(r),
+        };
+        (s, r)
+    } else {
+        let (s, r) = counter::new(flavors::array::Channel::with_capacity(cap));
+        let s = Sender {
+            flavor: SenderFlavor::Array(s),
+        };
+        let r = Receiver {
+            flavor: ReceiverFlavor::Array(r),
+        };
+        (s, r)
+    }
+}
+
+/// Creates a receiver that delivers a message after a certain duration of time.
+///
+/// The channel is bounded with capacity of 1 and never gets disconnected. Exactly one message will
+/// be sent into the channel after `duration` elapses. The message is the instant at which it is
+/// sent.
+///
+/// # Examples
+///
+/// Using an `after` channel for timeouts:
+///
+/// ```
+/// use std::time::Duration;
+/// use crossbeam_channel::{after, select, unbounded};
+///
+/// let (s, r) = unbounded::<i32>();
+/// let timeout = Duration::from_millis(100);
+///
+/// select! {
+///     recv(r) -> msg => println!("received {:?}", msg),
+///     recv(after(timeout)) -> _ => println!("timed out"),
+/// }
+/// ```
+///
+/// When the message gets sent:
+///
+/// ```
+/// use std::thread;
+/// use std::time::{Duration, Instant};
+/// use crossbeam_channel::after;
+///
+/// // Converts a number of milliseconds into a `Duration`.
+/// let ms = |ms| Duration::from_millis(ms);
+///
+/// // Returns `true` if `a` and `b` are very close `Instant`s.
+/// let eq = |a, b| a + ms(50) > b && b + ms(50) > a;
+///
+/// let start = Instant::now();
+/// let r = after(ms(100));
+///
+/// thread::sleep(ms(500));
+///
+/// // This message was sent 100 ms from the start and received 500 ms from the start.
+/// assert!(eq(r.recv().unwrap(), start + ms(100)));
+/// assert!(eq(Instant::now(), start + ms(500)));
+/// ```
+pub fn after(duration: Duration) -> Receiver<Instant> {
+    Receiver {
+        flavor: ReceiverFlavor::At(Arc::new(flavors::at::Channel::new_timeout(duration))),
+    }
+}
+
+/// Creates a receiver that delivers a message at a certain instant in time.
+///
+/// The channel is bounded with capacity of 1 and never gets disconnected. Exactly one message will
+/// be sent into the channel at the moment in time `when`. The message is the instant at which it
+/// is sent, which is the same as `when`. If `when` is in the past, the message will be delivered
+/// instantly to the receiver.
+///
+/// # Examples
+///
+/// Using an `at` channel for timeouts:
+///
+/// ```
+/// use std::time::{Instant, Duration};
+/// use crossbeam_channel::{at, select, unbounded};
+///
+/// let (s, r) = unbounded::<i32>();
+/// let deadline = Instant::now() + Duration::from_millis(500);
+///
+/// select! {
+///     recv(r) -> msg => println!("received {:?}", msg),
+///     recv(at(deadline)) -> _ => println!("timed out"),
+/// }
+/// ```
+///
+/// When the message gets sent:
+///
+/// ```
+/// use std::time::{Duration, Instant};
+/// use crossbeam_channel::at;
+///
+/// // Converts a number of milliseconds into a `Duration`.
+/// let ms = |ms| Duration::from_millis(ms);
+///
+/// let start = Instant::now();
+/// let end = start + ms(100);
+///
+/// let r = at(end);
+///
+/// // This message was sent 100 ms from the start
+/// assert_eq!(r.recv().unwrap(), end);
+/// assert!(Instant::now() > start + ms(100));
+/// ```
+pub fn at(when: Instant) -> Receiver<Instant> {
+    Receiver {
+        flavor: ReceiverFlavor::At(Arc::new(flavors::at::Channel::new_deadline(when))),
+    }
+}
+
+/// Creates a receiver that never delivers messages.
+///
+/// The channel is bounded with capacity of 0 and never gets disconnected.
+///
+/// # Examples
+///
+/// Using a `never` channel to optionally add a timeout to [`select!`]:
+///
+/// ```
+/// use std::thread;
+/// use std::time::Duration;
+/// use crossbeam_channel::{after, select, never, unbounded};
+///
+/// let (s, r) = unbounded();
+///
+/// thread::spawn(move || {
+///     thread::sleep(Duration::from_secs(1));
+///     s.send(1).unwrap();
+/// });
+///
+/// // Suppose this duration can be a `Some` or a `None`.
+/// let duration = Some(Duration::from_millis(100));
+///
+/// // Create a channel that times out after the specified duration.
+/// let timeout = duration
+///     .map(|d| after(d))
+///     .unwrap_or(never());
+///
+/// select! {
+///     recv(r) -> msg => assert_eq!(msg, Ok(1)),
+///     recv(timeout) -> _ => println!("timed out"),
+/// }
+/// ```
+///
+/// [`select!`]: macro.select.html
+pub fn never<T>() -> Receiver<T> {
+    Receiver {
+        flavor: ReceiverFlavor::Never(flavors::never::Channel::new()),
+    }
+}
+
+/// Creates a receiver that delivers messages periodically.
+///
+/// The channel is bounded with capacity of 1 and never gets disconnected. Messages will be
+/// sent into the channel in intervals of `duration`. Each message is the instant at which it is
+/// sent.
+///
+/// # Examples
+///
+/// Using a `tick` channel to periodically print elapsed time:
+///
+/// ```
+/// use std::time::{Duration, Instant};
+/// use crossbeam_channel::tick;
+///
+/// let start = Instant::now();
+/// let ticker = tick(Duration::from_millis(100));
+///
+/// for _ in 0..5 {
+///     ticker.recv().unwrap();
+///     println!("elapsed: {:?}", start.elapsed());
+/// }
+/// ```
+///
+/// When messages get sent:
+///
+/// ```
+/// use std::thread;
+/// use std::time::{Duration, Instant};
+/// use crossbeam_channel::tick;
+///
+/// // Converts a number of milliseconds into a `Duration`.
+/// let ms = |ms| Duration::from_millis(ms);
+///
+/// // Returns `true` if `a` and `b` are very close `Instant`s.
+/// let eq = |a, b| a + ms(50) > b && b + ms(50) > a;
+///
+/// let start = Instant::now();
+/// let r = tick(ms(100));
+///
+/// // This message was sent 100 ms from the start and received 100 ms from the start.
+/// assert!(eq(r.recv().unwrap(), start + ms(100)));
+/// assert!(eq(Instant::now(), start + ms(100)));
+///
+/// thread::sleep(ms(500));
+///
+/// // This message was sent 200 ms from the start and received 600 ms from the start.
+/// assert!(eq(r.recv().unwrap(), start + ms(200)));
+/// assert!(eq(Instant::now(), start + ms(600)));
+///
+/// // This message was sent 700 ms from the start and received 700 ms from the start.
+/// assert!(eq(r.recv().unwrap(), start + ms(700)));
+/// assert!(eq(Instant::now(), start + ms(700)));
+/// ```
+pub fn tick(duration: Duration) -> Receiver<Instant> {
+    Receiver {
+        flavor: ReceiverFlavor::Tick(Arc::new(flavors::tick::Channel::new(duration))),
+    }
+}
+
+/// The sending side of a channel.
+///
+/// # Examples
+///
+/// ```
+/// use std::thread;
+/// use crossbeam_channel::unbounded;
+///
+/// let (s1, r) = unbounded();
+/// let s2 = s1.clone();
+///
+/// thread::spawn(move || s1.send(1).unwrap());
+/// thread::spawn(move || s2.send(2).unwrap());
+///
+/// let msg1 = r.recv().unwrap();
+/// let msg2 = r.recv().unwrap();
+///
+/// assert_eq!(msg1 + msg2, 3);
+/// ```
+pub struct Sender<T> {
+    flavor: SenderFlavor<T>,
+}
+
+/// Sender flavors.
+enum SenderFlavor<T> {
+    /// Bounded channel based on a preallocated array.
+    Array(counter::Sender<flavors::array::Channel<T>>),
+
+    /// Unbounded channel implemented as a linked list.
+    List(counter::Sender<flavors::list::Channel<T>>),
+
+    /// Zero-capacity channel.
+    Zero(counter::Sender<flavors::zero::Channel<T>>),
+}
+
+unsafe impl<T: Send> Send for Sender<T> {}
+unsafe impl<T: Send> Sync for Sender<T> {}
+
+impl<T> UnwindSafe for Sender<T> {}
+impl<T> RefUnwindSafe for Sender<T> {}
+
+impl<T> Sender<T> {
+    /// Attempts to send a message into the channel without blocking.
+    ///
+    /// This method will either send a message into the channel immediately or return an error if
+    /// the channel is full or disconnected. The returned error contains the original message.
+    ///
+    /// If called on a zero-capacity channel, this method will send the message only if there
+    /// happens to be a receive operation on the other side of the channel at the same time.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{bounded, TrySendError};
+    ///
+    /// let (s, r) = bounded(1);
+    ///
+    /// assert_eq!(s.try_send(1), Ok(()));
+    /// assert_eq!(s.try_send(2), Err(TrySendError::Full(2)));
+    ///
+    /// drop(r);
+    /// assert_eq!(s.try_send(3), Err(TrySendError::Disconnected(3)));
+    /// ```
+    pub fn try_send(&self, msg: T) -> Result<(), TrySendError<T>> {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.try_send(msg),
+            SenderFlavor::List(chan) => chan.try_send(msg),
+            SenderFlavor::Zero(chan) => chan.try_send(msg),
+        }
+    }
+
+    /// Blocks the current thread until a message is sent or the channel is disconnected.
+    ///
+    /// If the channel is full and not disconnected, this call will block until the send operation
+    /// can proceed. If the channel becomes disconnected, this call will wake up and return an
+    /// error. The returned error contains the original message.
+    ///
+    /// If called on a zero-capacity channel, this method will wait for a receive operation to
+    /// appear on the other side of the channel.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::Duration;
+    /// use crossbeam_channel::{bounded, SendError};
+    ///
+    /// let (s, r) = bounded(1);
+    /// assert_eq!(s.send(1), Ok(()));
+    ///
+    /// thread::spawn(move || {
+    ///     assert_eq!(r.recv(), Ok(1));
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     drop(r);
+    /// });
+    ///
+    /// assert_eq!(s.send(2), Ok(()));
+    /// assert_eq!(s.send(3), Err(SendError(3)));
+    /// ```
+    pub fn send(&self, msg: T) -> Result<(), SendError<T>> {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.send(msg, None),
+            SenderFlavor::List(chan) => chan.send(msg, None),
+            SenderFlavor::Zero(chan) => chan.send(msg, None),
+        }
+        .map_err(|err| match err {
+            SendTimeoutError::Disconnected(msg) => SendError(msg),
+            SendTimeoutError::Timeout(_) => unreachable!(),
+        })
+    }
+
+    /// Waits for a message to be sent into the channel, but only for a limited time.
+    ///
+    /// If the channel is full and not disconnected, this call will block until the send operation
+    /// can proceed or the operation times out. If the channel becomes disconnected, this call will
+    /// wake up and return an error. The returned error contains the original message.
+    ///
+    /// If called on a zero-capacity channel, this method will wait for a receive operation to
+    /// appear on the other side of the channel.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::Duration;
+    /// use crossbeam_channel::{bounded, SendTimeoutError};
+    ///
+    /// let (s, r) = bounded(0);
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     assert_eq!(r.recv(), Ok(2));
+    ///     drop(r);
+    /// });
+    ///
+    /// assert_eq!(
+    ///     s.send_timeout(1, Duration::from_millis(500)),
+    ///     Err(SendTimeoutError::Timeout(1)),
+    /// );
+    /// assert_eq!(
+    ///     s.send_timeout(2, Duration::from_secs(1)),
+    ///     Ok(()),
+    /// );
+    /// assert_eq!(
+    ///     s.send_timeout(3, Duration::from_millis(500)),
+    ///     Err(SendTimeoutError::Disconnected(3)),
+    /// );
+    /// ```
+    pub fn send_timeout(&self, msg: T, timeout: Duration) -> Result<(), SendTimeoutError<T>> {
+        self.send_deadline(msg, Instant::now() + timeout)
+    }
+
+    /// Waits for a message to be sent into the channel, but only until a given deadline.
+    ///
+    /// If the channel is full and not disconnected, this call will block until the send operation
+    /// can proceed or the operation times out. If the channel becomes disconnected, this call will
+    /// wake up and return an error. The returned error contains the original message.
+    ///
+    /// If called on a zero-capacity channel, this method will wait for a receive operation to
+    /// appear on the other side of the channel.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::{Duration, Instant};
+    /// use crossbeam_channel::{bounded, SendTimeoutError};
+    ///
+    /// let (s, r) = bounded(0);
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     assert_eq!(r.recv(), Ok(2));
+    ///     drop(r);
+    /// });
+    ///
+    /// let now = Instant::now();
+    ///
+    /// assert_eq!(
+    ///     s.send_deadline(1, now + Duration::from_millis(500)),
+    ///     Err(SendTimeoutError::Timeout(1)),
+    /// );
+    /// assert_eq!(
+    ///     s.send_deadline(2, now + Duration::from_millis(1500)),
+    ///     Ok(()),
+    /// );
+    /// assert_eq!(
+    ///     s.send_deadline(3, now + Duration::from_millis(2000)),
+    ///     Err(SendTimeoutError::Disconnected(3)),
+    /// );
+    /// ```
+    pub fn send_deadline(&self, msg: T, deadline: Instant) -> Result<(), SendTimeoutError<T>> {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.send(msg, Some(deadline)),
+            SenderFlavor::List(chan) => chan.send(msg, Some(deadline)),
+            SenderFlavor::Zero(chan) => chan.send(msg, Some(deadline)),
+        }
+    }
+
+    /// Returns `true` if the channel is empty.
+    ///
+    /// Note: Zero-capacity channels are always empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::unbounded;
+    ///
+    /// let (s, r) = unbounded();
+    /// assert!(s.is_empty());
+    ///
+    /// s.send(0).unwrap();
+    /// assert!(!s.is_empty());
+    /// ```
+    pub fn is_empty(&self) -> bool {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.is_empty(),
+            SenderFlavor::List(chan) => chan.is_empty(),
+            SenderFlavor::Zero(chan) => chan.is_empty(),
+        }
+    }
+
+    /// Returns `true` if the channel is full.
+    ///
+    /// Note: Zero-capacity channels are always full.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::bounded;
+    ///
+    /// let (s, r) = bounded(1);
+    ///
+    /// assert!(!s.is_full());
+    /// s.send(0).unwrap();
+    /// assert!(s.is_full());
+    /// ```
+    pub fn is_full(&self) -> bool {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.is_full(),
+            SenderFlavor::List(chan) => chan.is_full(),
+            SenderFlavor::Zero(chan) => chan.is_full(),
+        }
+    }
+
+    /// Returns the number of messages in the channel.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::unbounded;
+    ///
+    /// let (s, r) = unbounded();
+    /// assert_eq!(s.len(), 0);
+    ///
+    /// s.send(1).unwrap();
+    /// s.send(2).unwrap();
+    /// assert_eq!(s.len(), 2);
+    /// ```
+    pub fn len(&self) -> usize {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.len(),
+            SenderFlavor::List(chan) => chan.len(),
+            SenderFlavor::Zero(chan) => chan.len(),
+        }
+    }
+
+    /// If the channel is bounded, returns its capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{bounded, unbounded};
+    ///
+    /// let (s, _) = unbounded::<i32>();
+    /// assert_eq!(s.capacity(), None);
+    ///
+    /// let (s, _) = bounded::<i32>(5);
+    /// assert_eq!(s.capacity(), Some(5));
+    ///
+    /// let (s, _) = bounded::<i32>(0);
+    /// assert_eq!(s.capacity(), Some(0));
+    /// ```
+    pub fn capacity(&self) -> Option<usize> {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.capacity(),
+            SenderFlavor::List(chan) => chan.capacity(),
+            SenderFlavor::Zero(chan) => chan.capacity(),
+        }
+    }
+
+    /// Returns `true` if senders belong to the same channel.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use crossbeam_channel::unbounded;
+    ///
+    /// let (s, _) = unbounded::<usize>();
+    ///
+    /// let s2 = s.clone();
+    /// assert!(s.same_channel(&s2));
+    ///
+    /// let (s3, _) = unbounded();
+    /// assert!(!s.same_channel(&s3));
+    /// ```
+    pub fn same_channel(&self, other: &Sender<T>) -> bool {
+        match (&self.flavor, &other.flavor) {
+            (SenderFlavor::Array(ref a), SenderFlavor::Array(ref b)) => a == b,
+            (SenderFlavor::List(ref a), SenderFlavor::List(ref b)) => a == b,
+            (SenderFlavor::Zero(ref a), SenderFlavor::Zero(ref b)) => a == b,
+            _ => false,
+        }
+    }
+}
+
+impl<T> Drop for Sender<T> {
+    fn drop(&mut self) {
+        unsafe {
+            match &self.flavor {
+                SenderFlavor::Array(chan) => chan.release(|c| c.disconnect()),
+                SenderFlavor::List(chan) => chan.release(|c| c.disconnect()),
+                SenderFlavor::Zero(chan) => chan.release(|c| c.disconnect()),
+            }
+        }
+    }
+}
+
+impl<T> Clone for Sender<T> {
+    fn clone(&self) -> Self {
+        let flavor = match &self.flavor {
+            SenderFlavor::Array(chan) => SenderFlavor::Array(chan.acquire()),
+            SenderFlavor::List(chan) => SenderFlavor::List(chan.acquire()),
+            SenderFlavor::Zero(chan) => SenderFlavor::Zero(chan.acquire()),
+        };
+
+        Sender { flavor }
+    }
+}
+
+impl<T> fmt::Debug for Sender<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("Sender { .. }")
+    }
+}
+
+/// The receiving side of a channel.
+///
+/// # Examples
+///
+/// ```
+/// use std::thread;
+/// use std::time::Duration;
+/// use crossbeam_channel::unbounded;
+///
+/// let (s, r) = unbounded();
+///
+/// thread::spawn(move || {
+///     let _ = s.send(1);
+///     thread::sleep(Duration::from_secs(1));
+///     let _ = s.send(2);
+/// });
+///
+/// assert_eq!(r.recv(), Ok(1)); // Received immediately.
+/// assert_eq!(r.recv(), Ok(2)); // Received after 1 second.
+/// ```
+pub struct Receiver<T> {
+    flavor: ReceiverFlavor<T>,
+}
+
+/// Receiver flavors.
+enum ReceiverFlavor<T> {
+    /// Bounded channel based on a preallocated array.
+    Array(counter::Receiver<flavors::array::Channel<T>>),
+
+    /// Unbounded channel implemented as a linked list.
+    List(counter::Receiver<flavors::list::Channel<T>>),
+
+    /// Zero-capacity channel.
+    Zero(counter::Receiver<flavors::zero::Channel<T>>),
+
+    /// The after flavor.
+    At(Arc<flavors::at::Channel>),
+
+    /// The tick flavor.
+    Tick(Arc<flavors::tick::Channel>),
+
+    /// The never flavor.
+    Never(flavors::never::Channel<T>),
+}
+
+unsafe impl<T: Send> Send for Receiver<T> {}
+unsafe impl<T: Send> Sync for Receiver<T> {}
+
+impl<T> UnwindSafe for Receiver<T> {}
+impl<T> RefUnwindSafe for Receiver<T> {}
+
+impl<T> Receiver<T> {
+    /// Attempts to receive a message from the channel without blocking.
+    ///
+    /// This method will either receive a message from the channel immediately or return an error
+    /// if the channel is empty.
+    ///
+    /// If called on a zero-capacity channel, this method will receive a message only if there
+    /// happens to be a send operation on the other side of the channel at the same time.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{unbounded, TryRecvError};
+    ///
+    /// let (s, r) = unbounded();
+    /// assert_eq!(r.try_recv(), Err(TryRecvError::Empty));
+    ///
+    /// s.send(5).unwrap();
+    /// drop(s);
+    ///
+    /// assert_eq!(r.try_recv(), Ok(5));
+    /// assert_eq!(r.try_recv(), Err(TryRecvError::Disconnected));
+    /// ```
+    pub fn try_recv(&self) -> Result<T, TryRecvError> {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.try_recv(),
+            ReceiverFlavor::List(chan) => chan.try_recv(),
+            ReceiverFlavor::Zero(chan) => chan.try_recv(),
+            ReceiverFlavor::At(chan) => {
+                let msg = chan.try_recv();
+                unsafe {
+                    mem::transmute_copy::<Result<Instant, TryRecvError>, Result<T, TryRecvError>>(
+                        &msg,
+                    )
+                }
+            }
+            ReceiverFlavor::Tick(chan) => {
+                let msg = chan.try_recv();
+                unsafe {
+                    mem::transmute_copy::<Result<Instant, TryRecvError>, Result<T, TryRecvError>>(
+                        &msg,
+                    )
+                }
+            }
+            ReceiverFlavor::Never(chan) => chan.try_recv(),
+        }
+    }
+
+    /// Blocks the current thread until a message is received or the channel is empty and
+    /// disconnected.
+    ///
+    /// If the channel is empty and not disconnected, this call will block until the receive
+    /// operation can proceed. If the channel is empty and becomes disconnected, this call will
+    /// wake up and return an error.
+    ///
+    /// If called on a zero-capacity channel, this method will wait for a send operation to appear
+    /// on the other side of the channel.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::Duration;
+    /// use crossbeam_channel::{unbounded, RecvError};
+    ///
+    /// let (s, r) = unbounded();
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     s.send(5).unwrap();
+    ///     drop(s);
+    /// });
+    ///
+    /// assert_eq!(r.recv(), Ok(5));
+    /// assert_eq!(r.recv(), Err(RecvError));
+    /// ```
+    pub fn recv(&self) -> Result<T, RecvError> {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.recv(None),
+            ReceiverFlavor::List(chan) => chan.recv(None),
+            ReceiverFlavor::Zero(chan) => chan.recv(None),
+            ReceiverFlavor::At(chan) => {
+                let msg = chan.recv(None);
+                unsafe {
+                    mem::transmute_copy::<
+                        Result<Instant, RecvTimeoutError>,
+                        Result<T, RecvTimeoutError>,
+                    >(&msg)
+                }
+            }
+            ReceiverFlavor::Tick(chan) => {
+                let msg = chan.recv(None);
+                unsafe {
+                    mem::transmute_copy::<
+                        Result<Instant, RecvTimeoutError>,
+                        Result<T, RecvTimeoutError>,
+                    >(&msg)
+                }
+            }
+            ReceiverFlavor::Never(chan) => chan.recv(None),
+        }
+        .map_err(|_| RecvError)
+    }
+
+    /// Waits for a message to be received from the channel, but only for a limited time.
+    ///
+    /// If the channel is empty and not disconnected, this call will block until the receive
+    /// operation can proceed or the operation times out. If the channel is empty and becomes
+    /// disconnected, this call will wake up and return an error.
+    ///
+    /// If called on a zero-capacity channel, this method will wait for a send operation to appear
+    /// on the other side of the channel.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::Duration;
+    /// use crossbeam_channel::{unbounded, RecvTimeoutError};
+    ///
+    /// let (s, r) = unbounded();
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     s.send(5).unwrap();
+    ///     drop(s);
+    /// });
+    ///
+    /// assert_eq!(
+    ///     r.recv_timeout(Duration::from_millis(500)),
+    ///     Err(RecvTimeoutError::Timeout),
+    /// );
+    /// assert_eq!(
+    ///     r.recv_timeout(Duration::from_secs(1)),
+    ///     Ok(5),
+    /// );
+    /// assert_eq!(
+    ///     r.recv_timeout(Duration::from_secs(1)),
+    ///     Err(RecvTimeoutError::Disconnected),
+    /// );
+    /// ```
+    pub fn recv_timeout(&self, timeout: Duration) -> Result<T, RecvTimeoutError> {
+        self.recv_deadline(Instant::now() + timeout)
+    }
+
+    /// Waits for a message to be received from the channel, but only before a given deadline.
+    ///
+    /// If the channel is empty and not disconnected, this call will block until the receive
+    /// operation can proceed or the operation times out. If the channel is empty and becomes
+    /// disconnected, this call will wake up and return an error.
+    ///
+    /// If called on a zero-capacity channel, this method will wait for a send operation to appear
+    /// on the other side of the channel.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::{Instant, Duration};
+    /// use crossbeam_channel::{unbounded, RecvTimeoutError};
+    ///
+    /// let (s, r) = unbounded();
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     s.send(5).unwrap();
+    ///     drop(s);
+    /// });
+    ///
+    /// let now = Instant::now();
+    ///
+    /// assert_eq!(
+    ///     r.recv_deadline(now + Duration::from_millis(500)),
+    ///     Err(RecvTimeoutError::Timeout),
+    /// );
+    /// assert_eq!(
+    ///     r.recv_deadline(now + Duration::from_millis(1500)),
+    ///     Ok(5),
+    /// );
+    /// assert_eq!(
+    ///     r.recv_deadline(now + Duration::from_secs(5)),
+    ///     Err(RecvTimeoutError::Disconnected),
+    /// );
+    /// ```
+    pub fn recv_deadline(&self, deadline: Instant) -> Result<T, RecvTimeoutError> {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.recv(Some(deadline)),
+            ReceiverFlavor::List(chan) => chan.recv(Some(deadline)),
+            ReceiverFlavor::Zero(chan) => chan.recv(Some(deadline)),
+            ReceiverFlavor::At(chan) => {
+                let msg = chan.recv(Some(deadline));
+                unsafe {
+                    mem::transmute_copy::<
+                        Result<Instant, RecvTimeoutError>,
+                        Result<T, RecvTimeoutError>,
+                    >(&msg)
+                }
+            }
+            ReceiverFlavor::Tick(chan) => {
+                let msg = chan.recv(Some(deadline));
+                unsafe {
+                    mem::transmute_copy::<
+                        Result<Instant, RecvTimeoutError>,
+                        Result<T, RecvTimeoutError>,
+                    >(&msg)
+                }
+            }
+            ReceiverFlavor::Never(chan) => chan.recv(Some(deadline)),
+        }
+    }
+
+    /// Returns `true` if the channel is empty.
+    ///
+    /// Note: Zero-capacity channels are always empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::unbounded;
+    ///
+    /// let (s, r) = unbounded();
+    ///
+    /// assert!(r.is_empty());
+    /// s.send(0).unwrap();
+    /// assert!(!r.is_empty());
+    /// ```
+    pub fn is_empty(&self) -> bool {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.is_empty(),
+            ReceiverFlavor::List(chan) => chan.is_empty(),
+            ReceiverFlavor::Zero(chan) => chan.is_empty(),
+            ReceiverFlavor::At(chan) => chan.is_empty(),
+            ReceiverFlavor::Tick(chan) => chan.is_empty(),
+            ReceiverFlavor::Never(chan) => chan.is_empty(),
+        }
+    }
+
+    /// Returns `true` if the channel is full.
+    ///
+    /// Note: Zero-capacity channels are always full.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::bounded;
+    ///
+    /// let (s, r) = bounded(1);
+    ///
+    /// assert!(!r.is_full());
+    /// s.send(0).unwrap();
+    /// assert!(r.is_full());
+    /// ```
+    pub fn is_full(&self) -> bool {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.is_full(),
+            ReceiverFlavor::List(chan) => chan.is_full(),
+            ReceiverFlavor::Zero(chan) => chan.is_full(),
+            ReceiverFlavor::At(chan) => chan.is_full(),
+            ReceiverFlavor::Tick(chan) => chan.is_full(),
+            ReceiverFlavor::Never(chan) => chan.is_full(),
+        }
+    }
+
+    /// Returns the number of messages in the channel.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::unbounded;
+    ///
+    /// let (s, r) = unbounded();
+    /// assert_eq!(r.len(), 0);
+    ///
+    /// s.send(1).unwrap();
+    /// s.send(2).unwrap();
+    /// assert_eq!(r.len(), 2);
+    /// ```
+    pub fn len(&self) -> usize {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.len(),
+            ReceiverFlavor::List(chan) => chan.len(),
+            ReceiverFlavor::Zero(chan) => chan.len(),
+            ReceiverFlavor::At(chan) => chan.len(),
+            ReceiverFlavor::Tick(chan) => chan.len(),
+            ReceiverFlavor::Never(chan) => chan.len(),
+        }
+    }
+
+    /// If the channel is bounded, returns its capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{bounded, unbounded};
+    ///
+    /// let (_, r) = unbounded::<i32>();
+    /// assert_eq!(r.capacity(), None);
+    ///
+    /// let (_, r) = bounded::<i32>(5);
+    /// assert_eq!(r.capacity(), Some(5));
+    ///
+    /// let (_, r) = bounded::<i32>(0);
+    /// assert_eq!(r.capacity(), Some(0));
+    /// ```
+    pub fn capacity(&self) -> Option<usize> {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.capacity(),
+            ReceiverFlavor::List(chan) => chan.capacity(),
+            ReceiverFlavor::Zero(chan) => chan.capacity(),
+            ReceiverFlavor::At(chan) => chan.capacity(),
+            ReceiverFlavor::Tick(chan) => chan.capacity(),
+            ReceiverFlavor::Never(chan) => chan.capacity(),
+        }
+    }
+
+    /// A blocking iterator over messages in the channel.
+    ///
+    /// Each call to [`next`] blocks waiting for the next message and then returns it. However, if
+    /// the channel becomes empty and disconnected, it returns [`None`] without blocking.
+    ///
+    /// [`next`]: Iterator::next
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use crossbeam_channel::unbounded;
+    ///
+    /// let (s, r) = unbounded();
+    ///
+    /// thread::spawn(move || {
+    ///     s.send(1).unwrap();
+    ///     s.send(2).unwrap();
+    ///     s.send(3).unwrap();
+    ///     drop(s); // Disconnect the channel.
+    /// });
+    ///
+    /// // Collect all messages from the channel.
+    /// // Note that the call to `collect` blocks until the sender is dropped.
+    /// let v: Vec<_> = r.iter().collect();
+    ///
+    /// assert_eq!(v, [1, 2, 3]);
+    /// ```
+    pub fn iter(&self) -> Iter<'_, T> {
+        Iter { receiver: self }
+    }
+
+    /// A non-blocking iterator over messages in the channel.
+    ///
+    /// Each call to [`next`] returns a message if there is one ready to be received. The iterator
+    /// never blocks waiting for the next message.
+    ///
+    /// [`next`]: Iterator::next
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::Duration;
+    /// use crossbeam_channel::unbounded;
+    ///
+    /// let (s, r) = unbounded::<i32>();
+    ///
+    /// thread::spawn(move || {
+    ///     s.send(1).unwrap();
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     s.send(2).unwrap();
+    ///     thread::sleep(Duration::from_secs(2));
+    ///     s.send(3).unwrap();
+    /// });
+    ///
+    /// thread::sleep(Duration::from_secs(2));
+    ///
+    /// // Collect all messages from the channel without blocking.
+    /// // The third message hasn't been sent yet so we'll collect only the first two.
+    /// let v: Vec<_> = r.try_iter().collect();
+    ///
+    /// assert_eq!(v, [1, 2]);
+    /// ```
+    pub fn try_iter(&self) -> TryIter<'_, T> {
+        TryIter { receiver: self }
+    }
+
+    /// Returns `true` if receivers belong to the same channel.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use crossbeam_channel::unbounded;
+    ///
+    /// let (_, r) = unbounded::<usize>();
+    ///
+    /// let r2 = r.clone();
+    /// assert!(r.same_channel(&r2));
+    ///
+    /// let (_, r3) = unbounded();
+    /// assert!(!r.same_channel(&r3));
+    /// ```
+    pub fn same_channel(&self, other: &Receiver<T>) -> bool {
+        match (&self.flavor, &other.flavor) {
+            (ReceiverFlavor::Array(a), ReceiverFlavor::Array(b)) => a == b,
+            (ReceiverFlavor::List(a), ReceiverFlavor::List(b)) => a == b,
+            (ReceiverFlavor::Zero(a), ReceiverFlavor::Zero(b)) => a == b,
+            (ReceiverFlavor::At(a), ReceiverFlavor::At(b)) => Arc::ptr_eq(a, b),
+            (ReceiverFlavor::Tick(a), ReceiverFlavor::Tick(b)) => Arc::ptr_eq(a, b),
+            (ReceiverFlavor::Never(_), ReceiverFlavor::Never(_)) => true,
+            _ => false,
+        }
+    }
+}
+
+impl<T> Drop for Receiver<T> {
+    fn drop(&mut self) {
+        unsafe {
+            match &self.flavor {
+                ReceiverFlavor::Array(chan) => chan.release(|c| c.disconnect()),
+                ReceiverFlavor::List(chan) => chan.release(|c| c.disconnect()),
+                ReceiverFlavor::Zero(chan) => chan.release(|c| c.disconnect()),
+                ReceiverFlavor::At(_) => {}
+                ReceiverFlavor::Tick(_) => {}
+                ReceiverFlavor::Never(_) => {}
+            }
+        }
+    }
+}
+
+impl<T> Clone for Receiver<T> {
+    fn clone(&self) -> Self {
+        let flavor = match &self.flavor {
+            ReceiverFlavor::Array(chan) => ReceiverFlavor::Array(chan.acquire()),
+            ReceiverFlavor::List(chan) => ReceiverFlavor::List(chan.acquire()),
+            ReceiverFlavor::Zero(chan) => ReceiverFlavor::Zero(chan.acquire()),
+            ReceiverFlavor::At(chan) => ReceiverFlavor::At(chan.clone()),
+            ReceiverFlavor::Tick(chan) => ReceiverFlavor::Tick(chan.clone()),
+            ReceiverFlavor::Never(_) => ReceiverFlavor::Never(flavors::never::Channel::new()),
+        };
+
+        Receiver { flavor }
+    }
+}
+
+impl<T> fmt::Debug for Receiver<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("Receiver { .. }")
+    }
+}
+
+impl<'a, T> IntoIterator for &'a Receiver<T> {
+    type Item = T;
+    type IntoIter = Iter<'a, T>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter()
+    }
+}
+
+impl<T> IntoIterator for Receiver<T> {
+    type Item = T;
+    type IntoIter = IntoIter<T>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        IntoIter { receiver: self }
+    }
+}
+
+/// A blocking iterator over messages in a channel.
+///
+/// Each call to [`next`] blocks waiting for the next message and then returns it. However, if the
+/// channel becomes empty and disconnected, it returns [`None`] without blocking.
+///
+/// [`next`]: Iterator::next
+///
+/// # Examples
+///
+/// ```
+/// use std::thread;
+/// use crossbeam_channel::unbounded;
+///
+/// let (s, r) = unbounded();
+///
+/// thread::spawn(move || {
+///     s.send(1).unwrap();
+///     s.send(2).unwrap();
+///     s.send(3).unwrap();
+///     drop(s); // Disconnect the channel.
+/// });
+///
+/// // Collect all messages from the channel.
+/// // Note that the call to `collect` blocks until the sender is dropped.
+/// let v: Vec<_> = r.iter().collect();
+///
+/// assert_eq!(v, [1, 2, 3]);
+/// ```
+pub struct Iter<'a, T> {
+    receiver: &'a Receiver<T>,
+}
+
+impl<T> FusedIterator for Iter<'_, T> {}
+
+impl<T> Iterator for Iter<'_, T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.receiver.recv().ok()
+    }
+}
+
+impl<T> fmt::Debug for Iter<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("Iter { .. }")
+    }
+}
+
+/// A non-blocking iterator over messages in a channel.
+///
+/// Each call to [`next`] returns a message if there is one ready to be received. The iterator
+/// never blocks waiting for the next message.
+///
+/// [`next`]: Iterator::next
+///
+/// # Examples
+///
+/// ```
+/// use std::thread;
+/// use std::time::Duration;
+/// use crossbeam_channel::unbounded;
+///
+/// let (s, r) = unbounded::<i32>();
+///
+/// thread::spawn(move || {
+///     s.send(1).unwrap();
+///     thread::sleep(Duration::from_secs(1));
+///     s.send(2).unwrap();
+///     thread::sleep(Duration::from_secs(2));
+///     s.send(3).unwrap();
+/// });
+///
+/// thread::sleep(Duration::from_secs(2));
+///
+/// // Collect all messages from the channel without blocking.
+/// // The third message hasn't been sent yet so we'll collect only the first two.
+/// let v: Vec<_> = r.try_iter().collect();
+///
+/// assert_eq!(v, [1, 2]);
+/// ```
+pub struct TryIter<'a, T> {
+    receiver: &'a Receiver<T>,
+}
+
+impl<T> Iterator for TryIter<'_, T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.receiver.try_recv().ok()
+    }
+}
+
+impl<T> fmt::Debug for TryIter<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("TryIter { .. }")
+    }
+}
+
+/// A blocking iterator over messages in a channel.
+///
+/// Each call to [`next`] blocks waiting for the next message and then returns it. However, if the
+/// channel becomes empty and disconnected, it returns [`None`] without blocking.
+///
+/// [`next`]: Iterator::next
+///
+/// # Examples
+///
+/// ```
+/// use std::thread;
+/// use crossbeam_channel::unbounded;
+///
+/// let (s, r) = unbounded();
+///
+/// thread::spawn(move || {
+///     s.send(1).unwrap();
+///     s.send(2).unwrap();
+///     s.send(3).unwrap();
+///     drop(s); // Disconnect the channel.
+/// });
+///
+/// // Collect all messages from the channel.
+/// // Note that the call to `collect` blocks until the sender is dropped.
+/// let v: Vec<_> = r.into_iter().collect();
+///
+/// assert_eq!(v, [1, 2, 3]);
+/// ```
+pub struct IntoIter<T> {
+    receiver: Receiver<T>,
+}
+
+impl<T> FusedIterator for IntoIter<T> {}
+
+impl<T> Iterator for IntoIter<T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.receiver.recv().ok()
+    }
+}
+
+impl<T> fmt::Debug for IntoIter<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("IntoIter { .. }")
+    }
+}
+
+impl<T> SelectHandle for Sender<T> {
+    fn try_select(&self, token: &mut Token) -> bool {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.sender().try_select(token),
+            SenderFlavor::List(chan) => chan.sender().try_select(token),
+            SenderFlavor::Zero(chan) => chan.sender().try_select(token),
+        }
+    }
+
+    fn deadline(&self) -> Option<Instant> {
+        None
+    }
+
+    fn register(&self, oper: Operation, cx: &Context) -> bool {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.sender().register(oper, cx),
+            SenderFlavor::List(chan) => chan.sender().register(oper, cx),
+            SenderFlavor::Zero(chan) => chan.sender().register(oper, cx),
+        }
+    }
+
+    fn unregister(&self, oper: Operation) {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.sender().unregister(oper),
+            SenderFlavor::List(chan) => chan.sender().unregister(oper),
+            SenderFlavor::Zero(chan) => chan.sender().unregister(oper),
+        }
+    }
+
+    fn accept(&self, token: &mut Token, cx: &Context) -> bool {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.sender().accept(token, cx),
+            SenderFlavor::List(chan) => chan.sender().accept(token, cx),
+            SenderFlavor::Zero(chan) => chan.sender().accept(token, cx),
+        }
+    }
+
+    fn is_ready(&self) -> bool {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.sender().is_ready(),
+            SenderFlavor::List(chan) => chan.sender().is_ready(),
+            SenderFlavor::Zero(chan) => chan.sender().is_ready(),
+        }
+    }
+
+    fn watch(&self, oper: Operation, cx: &Context) -> bool {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.sender().watch(oper, cx),
+            SenderFlavor::List(chan) => chan.sender().watch(oper, cx),
+            SenderFlavor::Zero(chan) => chan.sender().watch(oper, cx),
+        }
+    }
+
+    fn unwatch(&self, oper: Operation) {
+        match &self.flavor {
+            SenderFlavor::Array(chan) => chan.sender().unwatch(oper),
+            SenderFlavor::List(chan) => chan.sender().unwatch(oper),
+            SenderFlavor::Zero(chan) => chan.sender().unwatch(oper),
+        }
+    }
+}
+
+impl<T> SelectHandle for Receiver<T> {
+    fn try_select(&self, token: &mut Token) -> bool {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.receiver().try_select(token),
+            ReceiverFlavor::List(chan) => chan.receiver().try_select(token),
+            ReceiverFlavor::Zero(chan) => chan.receiver().try_select(token),
+            ReceiverFlavor::At(chan) => chan.try_select(token),
+            ReceiverFlavor::Tick(chan) => chan.try_select(token),
+            ReceiverFlavor::Never(chan) => chan.try_select(token),
+        }
+    }
+
+    fn deadline(&self) -> Option<Instant> {
+        match &self.flavor {
+            ReceiverFlavor::Array(_) => None,
+            ReceiverFlavor::List(_) => None,
+            ReceiverFlavor::Zero(_) => None,
+            ReceiverFlavor::At(chan) => chan.deadline(),
+            ReceiverFlavor::Tick(chan) => chan.deadline(),
+            ReceiverFlavor::Never(chan) => chan.deadline(),
+        }
+    }
+
+    fn register(&self, oper: Operation, cx: &Context) -> bool {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.receiver().register(oper, cx),
+            ReceiverFlavor::List(chan) => chan.receiver().register(oper, cx),
+            ReceiverFlavor::Zero(chan) => chan.receiver().register(oper, cx),
+            ReceiverFlavor::At(chan) => chan.register(oper, cx),
+            ReceiverFlavor::Tick(chan) => chan.register(oper, cx),
+            ReceiverFlavor::Never(chan) => chan.register(oper, cx),
+        }
+    }
+
+    fn unregister(&self, oper: Operation) {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.receiver().unregister(oper),
+            ReceiverFlavor::List(chan) => chan.receiver().unregister(oper),
+            ReceiverFlavor::Zero(chan) => chan.receiver().unregister(oper),
+            ReceiverFlavor::At(chan) => chan.unregister(oper),
+            ReceiverFlavor::Tick(chan) => chan.unregister(oper),
+            ReceiverFlavor::Never(chan) => chan.unregister(oper),
+        }
+    }
+
+    fn accept(&self, token: &mut Token, cx: &Context) -> bool {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.receiver().accept(token, cx),
+            ReceiverFlavor::List(chan) => chan.receiver().accept(token, cx),
+            ReceiverFlavor::Zero(chan) => chan.receiver().accept(token, cx),
+            ReceiverFlavor::At(chan) => chan.accept(token, cx),
+            ReceiverFlavor::Tick(chan) => chan.accept(token, cx),
+            ReceiverFlavor::Never(chan) => chan.accept(token, cx),
+        }
+    }
+
+    fn is_ready(&self) -> bool {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.receiver().is_ready(),
+            ReceiverFlavor::List(chan) => chan.receiver().is_ready(),
+            ReceiverFlavor::Zero(chan) => chan.receiver().is_ready(),
+            ReceiverFlavor::At(chan) => chan.is_ready(),
+            ReceiverFlavor::Tick(chan) => chan.is_ready(),
+            ReceiverFlavor::Never(chan) => chan.is_ready(),
+        }
+    }
+
+    fn watch(&self, oper: Operation, cx: &Context) -> bool {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.receiver().watch(oper, cx),
+            ReceiverFlavor::List(chan) => chan.receiver().watch(oper, cx),
+            ReceiverFlavor::Zero(chan) => chan.receiver().watch(oper, cx),
+            ReceiverFlavor::At(chan) => chan.watch(oper, cx),
+            ReceiverFlavor::Tick(chan) => chan.watch(oper, cx),
+            ReceiverFlavor::Never(chan) => chan.watch(oper, cx),
+        }
+    }
+
+    fn unwatch(&self, oper: Operation) {
+        match &self.flavor {
+            ReceiverFlavor::Array(chan) => chan.receiver().unwatch(oper),
+            ReceiverFlavor::List(chan) => chan.receiver().unwatch(oper),
+            ReceiverFlavor::Zero(chan) => chan.receiver().unwatch(oper),
+            ReceiverFlavor::At(chan) => chan.unwatch(oper),
+            ReceiverFlavor::Tick(chan) => chan.unwatch(oper),
+            ReceiverFlavor::Never(chan) => chan.unwatch(oper),
+        }
+    }
+}
+
+/// Writes a message into the channel.
+pub unsafe fn write<T>(s: &Sender<T>, token: &mut Token, msg: T) -> Result<(), T> {
+    match &s.flavor {
+        SenderFlavor::Array(chan) => chan.write(token, msg),
+        SenderFlavor::List(chan) => chan.write(token, msg),
+        SenderFlavor::Zero(chan) => chan.write(token, msg),
+    }
+}
+
+/// Reads a message from the channel.
+pub unsafe fn read<T>(r: &Receiver<T>, token: &mut Token) -> Result<T, ()> {
+    match &r.flavor {
+        ReceiverFlavor::Array(chan) => chan.read(token),
+        ReceiverFlavor::List(chan) => chan.read(token),
+        ReceiverFlavor::Zero(chan) => chan.read(token),
+        ReceiverFlavor::At(chan) => {
+            mem::transmute_copy::<Result<Instant, ()>, Result<T, ()>>(&chan.read(token))
+        }
+        ReceiverFlavor::Tick(chan) => {
+            mem::transmute_copy::<Result<Instant, ()>, Result<T, ()>>(&chan.read(token))
+        }
+        ReceiverFlavor::Never(chan) => chan.read(token),
+    }
+}
diff --git a/src/context.rs b/src/context.rs
new file mode 100644
index 0000000..e2e8480
--- /dev/null
+++ b/src/context.rs
@@ -0,0 +1,191 @@
+//! Thread-local context used in select.
+
+use std::cell::Cell;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Arc;
+use std::thread::{self, Thread, ThreadId};
+use std::time::Instant;
+
+use crossbeam_utils::Backoff;
+
+use crate::select::Selected;
+
+/// Thread-local context used in select.
+#[derive(Debug, Clone)]
+pub struct Context {
+    inner: Arc<Inner>,
+}
+
+/// Inner representation of `Context`.
+#[derive(Debug)]
+struct Inner {
+    /// Selected operation.
+    select: AtomicUsize,
+
+    /// A slot into which another thread may store a pointer to its `Packet`.
+    packet: AtomicUsize,
+
+    /// Thread handle.
+    thread: Thread,
+
+    /// Thread id.
+    thread_id: ThreadId,
+}
+
+impl Context {
+    /// Creates a new context for the duration of the closure.
+    #[inline]
+    pub fn with<F, R>(f: F) -> R
+    where
+        F: FnOnce(&Context) -> R,
+    {
+        thread_local! {
+            /// Cached thread-local context.
+            static CONTEXT: Cell<Option<Context>> = Cell::new(Some(Context::new()));
+        }
+
+        let mut f = Some(f);
+        let mut f = move |cx: &Context| -> R {
+            let f = f.take().unwrap();
+            f(cx)
+        };
+
+        CONTEXT
+            .try_with(|cell| match cell.take() {
+                None => f(&Context::new()),
+                Some(cx) => {
+                    cx.reset();
+                    let res = f(&cx);
+                    cell.set(Some(cx));
+                    res
+                }
+            })
+            .unwrap_or_else(|_| f(&Context::new()))
+    }
+
+    /// Creates a new `Context`.
+    #[cold]
+    fn new() -> Context {
+        Context {
+            inner: Arc::new(Inner {
+                select: AtomicUsize::new(Selected::Waiting.into()),
+                packet: AtomicUsize::new(0),
+                thread: thread::current(),
+                thread_id: thread::current().id(),
+            }),
+        }
+    }
+
+    /// Resets `select` and `packet`.
+    #[inline]
+    fn reset(&self) {
+        self.inner
+            .select
+            .store(Selected::Waiting.into(), Ordering::Release);
+        self.inner.packet.store(0, Ordering::Release);
+    }
+
+    /// Attempts to select an operation.
+    ///
+    /// On failure, the previously selected operation is returned.
+    #[inline]
+    pub fn try_select(&self, select: Selected) -> Result<(), Selected> {
+        self.inner
+            .select
+            .compare_exchange(
+                Selected::Waiting.into(),
+                select.into(),
+                Ordering::AcqRel,
+                Ordering::Acquire,
+            )
+            .map(|_| ())
+            .map_err(|e| e.into())
+    }
+
+    /// Returns the selected operation.
+    #[inline]
+    pub fn selected(&self) -> Selected {
+        Selected::from(self.inner.select.load(Ordering::Acquire))
+    }
+
+    /// Stores a packet.
+    ///
+    /// This method must be called after `try_select` succeeds and there is a packet to provide.
+    #[inline]
+    pub fn store_packet(&self, packet: usize) {
+        if packet != 0 {
+            self.inner.packet.store(packet, Ordering::Release);
+        }
+    }
+
+    /// Waits until a packet is provided and returns it.
+    #[inline]
+    pub fn wait_packet(&self) -> usize {
+        let backoff = Backoff::new();
+        loop {
+            let packet = self.inner.packet.load(Ordering::Acquire);
+            if packet != 0 {
+                return packet;
+            }
+            backoff.snooze();
+        }
+    }
+
+    /// Waits until an operation is selected and returns it.
+    ///
+    /// If the deadline is reached, `Selected::Aborted` will be selected.
+    #[inline]
+    pub fn wait_until(&self, deadline: Option<Instant>) -> Selected {
+        // Spin for a short time, waiting until an operation is selected.
+        let backoff = Backoff::new();
+        loop {
+            let sel = Selected::from(self.inner.select.load(Ordering::Acquire));
+            if sel != Selected::Waiting {
+                return sel;
+            }
+
+            if backoff.is_completed() {
+                break;
+            } else {
+                backoff.snooze();
+            }
+        }
+
+        loop {
+            // Check whether an operation has been selected.
+            let sel = Selected::from(self.inner.select.load(Ordering::Acquire));
+            if sel != Selected::Waiting {
+                return sel;
+            }
+
+            // If there's a deadline, park the current thread until the deadline is reached.
+            if let Some(end) = deadline {
+                let now = Instant::now();
+
+                if now < end {
+                    thread::park_timeout(end - now);
+                } else {
+                    // The deadline has been reached. Try aborting select.
+                    return match self.try_select(Selected::Aborted) {
+                        Ok(()) => Selected::Aborted,
+                        Err(s) => s,
+                    };
+                }
+            } else {
+                thread::park();
+            }
+        }
+    }
+
+    /// Unparks the thread this context belongs to.
+    #[inline]
+    pub fn unpark(&self) {
+        self.inner.thread.unpark();
+    }
+
+    /// Returns the id of the thread this context belongs to.
+    #[inline]
+    pub fn thread_id(&self) -> ThreadId {
+        self.inner.thread_id
+    }
+}
diff --git a/src/counter.rs b/src/counter.rs
new file mode 100644
index 0000000..2eaf067
--- /dev/null
+++ b/src/counter.rs
@@ -0,0 +1,144 @@
+//! Reference counter for channels.
+
+use std::isize;
+use std::ops;
+use std::process;
+use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
+
+/// Reference counter internals.
+struct Counter<C> {
+    /// The number of senders associated with the channel.
+    senders: AtomicUsize,
+
+    /// The number of receivers associated with the channel.
+    receivers: AtomicUsize,
+
+    /// Set to `true` if the last sender or the last receiver reference deallocates the channel.
+    destroy: AtomicBool,
+
+    /// The internal channel.
+    chan: C,
+}
+
+/// Wraps a channel into the reference counter.
+pub fn new<C>(chan: C) -> (Sender<C>, Receiver<C>) {
+    let counter = Box::into_raw(Box::new(Counter {
+        senders: AtomicUsize::new(1),
+        receivers: AtomicUsize::new(1),
+        destroy: AtomicBool::new(false),
+        chan,
+    }));
+    let s = Sender { counter };
+    let r = Receiver { counter };
+    (s, r)
+}
+
+/// The sending side.
+pub struct Sender<C> {
+    counter: *mut Counter<C>,
+}
+
+impl<C> Sender<C> {
+    /// Returns the internal `Counter`.
+    fn counter(&self) -> &Counter<C> {
+        unsafe { &*self.counter }
+    }
+
+    /// Acquires another sender reference.
+    pub fn acquire(&self) -> Sender<C> {
+        let count = self.counter().senders.fetch_add(1, Ordering::Relaxed);
+
+        // Cloning senders and calling `mem::forget` on the clones could potentially overflow the
+        // counter. It's very difficult to recover sensibly from such degenerate scenarios so we
+        // just abort when the count becomes very large.
+        if count > isize::MAX as usize {
+            process::abort();
+        }
+
+        Sender {
+            counter: self.counter,
+        }
+    }
+
+    /// Releases the sender reference.
+    ///
+    /// Function `disconnect` will be called if this is the last sender reference.
+    pub unsafe fn release<F: FnOnce(&C) -> bool>(&self, disconnect: F) {
+        if self.counter().senders.fetch_sub(1, Ordering::AcqRel) == 1 {
+            disconnect(&self.counter().chan);
+
+            if self.counter().destroy.swap(true, Ordering::AcqRel) {
+                drop(Box::from_raw(self.counter));
+            }
+        }
+    }
+}
+
+impl<C> ops::Deref for Sender<C> {
+    type Target = C;
+
+    fn deref(&self) -> &C {
+        &self.counter().chan
+    }
+}
+
+impl<C> PartialEq for Sender<C> {
+    fn eq(&self, other: &Sender<C>) -> bool {
+        self.counter == other.counter
+    }
+}
+
+/// The receiving side.
+pub struct Receiver<C> {
+    counter: *mut Counter<C>,
+}
+
+impl<C> Receiver<C> {
+    /// Returns the internal `Counter`.
+    fn counter(&self) -> &Counter<C> {
+        unsafe { &*self.counter }
+    }
+
+    /// Acquires another receiver reference.
+    pub fn acquire(&self) -> Receiver<C> {
+        let count = self.counter().receivers.fetch_add(1, Ordering::Relaxed);
+
+        // Cloning receivers and calling `mem::forget` on the clones could potentially overflow the
+        // counter. It's very difficult to recover sensibly from such degenerate scenarios so we
+        // just abort when the count becomes very large.
+        if count > isize::MAX as usize {
+            process::abort();
+        }
+
+        Receiver {
+            counter: self.counter,
+        }
+    }
+
+    /// Releases the receiver reference.
+    ///
+    /// Function `disconnect` will be called if this is the last receiver reference.
+    pub unsafe fn release<F: FnOnce(&C) -> bool>(&self, disconnect: F) {
+        if self.counter().receivers.fetch_sub(1, Ordering::AcqRel) == 1 {
+            disconnect(&self.counter().chan);
+
+            if self.counter().destroy.swap(true, Ordering::AcqRel) {
+                drop(Box::from_raw(self.counter));
+            }
+        }
+    }
+}
+
+impl<C> ops::Deref for Receiver<C> {
+    type Target = C;
+
+    fn deref(&self) -> &C {
+        &self.counter().chan
+    }
+}
+
+impl<C> PartialEq for Receiver<C> {
+    fn eq(&self, other: &Receiver<C>) -> bool {
+        self.counter == other.counter
+    }
+}
diff --git a/src/err.rs b/src/err.rs
new file mode 100644
index 0000000..578acc6
--- /dev/null
+++ b/src/err.rs
@@ -0,0 +1,382 @@
+use std::error;
+use std::fmt;
+
+/// An error returned from the [`send`] method.
+///
+/// The message could not be sent because the channel is disconnected.
+///
+/// The error contains the message so it can be recovered.
+///
+/// [`send`]: super::Sender::send
+#[derive(PartialEq, Eq, Clone, Copy)]
+pub struct SendError<T>(pub T);
+
+/// An error returned from the [`try_send`] method.
+///
+/// The error contains the message being sent so it can be recovered.
+///
+/// [`try_send`]: super::Sender::try_send
+#[derive(PartialEq, Eq, Clone, Copy)]
+pub enum TrySendError<T> {
+    /// The message could not be sent because the channel is full.
+    ///
+    /// If this is a zero-capacity channel, then the error indicates that there was no receiver
+    /// available to receive the message at the time.
+    Full(T),
+
+    /// The message could not be sent because the channel is disconnected.
+    Disconnected(T),
+}
+
+/// An error returned from the [`send_timeout`] method.
+///
+/// The error contains the message being sent so it can be recovered.
+///
+/// [`send_timeout`]: super::Sender::send_timeout
+#[derive(PartialEq, Eq, Clone, Copy)]
+pub enum SendTimeoutError<T> {
+    /// The message could not be sent because the channel is full and the operation timed out.
+    ///
+    /// If this is a zero-capacity channel, then the error indicates that there was no receiver
+    /// available to receive the message and the operation timed out.
+    Timeout(T),
+
+    /// The message could not be sent because the channel is disconnected.
+    Disconnected(T),
+}
+
+/// An error returned from the [`recv`] method.
+///
+/// A message could not be received because the channel is empty and disconnected.
+///
+/// [`recv`]: super::Receiver::recv
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub struct RecvError;
+
+/// An error returned from the [`try_recv`] method.
+///
+/// [`try_recv`]: super::Receiver::try_recv
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub enum TryRecvError {
+    /// A message could not be received because the channel is empty.
+    ///
+    /// If this is a zero-capacity channel, then the error indicates that there was no sender
+    /// available to send a message at the time.
+    Empty,
+
+    /// The message could not be received because the channel is empty and disconnected.
+    Disconnected,
+}
+
+/// An error returned from the [`recv_timeout`] method.
+///
+/// [`recv_timeout`]: super::Receiver::recv_timeout
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub enum RecvTimeoutError {
+    /// A message could not be received because the channel is empty and the operation timed out.
+    ///
+    /// If this is a zero-capacity channel, then the error indicates that there was no sender
+    /// available to send a message and the operation timed out.
+    Timeout,
+
+    /// The message could not be received because the channel is empty and disconnected.
+    Disconnected,
+}
+
+/// An error returned from the [`try_select`] method.
+///
+/// Failed because none of the channel operations were ready.
+///
+/// [`try_select`]: super::Select::try_select
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub struct TrySelectError;
+
+/// An error returned from the [`select_timeout`] method.
+///
+/// Failed because none of the channel operations became ready before the timeout.
+///
+/// [`select_timeout`]: super::Select::select_timeout
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub struct SelectTimeoutError;
+
+/// An error returned from the [`try_ready`] method.
+///
+/// Failed because none of the channel operations were ready.
+///
+/// [`try_ready`]: super::Select::try_ready
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub struct TryReadyError;
+
+/// An error returned from the [`ready_timeout`] method.
+///
+/// Failed because none of the channel operations became ready before the timeout.
+///
+/// [`ready_timeout`]: super::Select::ready_timeout
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub struct ReadyTimeoutError;
+
+impl<T> fmt::Debug for SendError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "SendError(..)".fmt(f)
+    }
+}
+
+impl<T> fmt::Display for SendError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "sending on a disconnected channel".fmt(f)
+    }
+}
+
+impl<T: Send> error::Error for SendError<T> {}
+
+impl<T> SendError<T> {
+    /// Unwraps the message.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::unbounded;
+    ///
+    /// let (s, r) = unbounded();
+    /// drop(r);
+    ///
+    /// if let Err(err) = s.send("foo") {
+    ///     assert_eq!(err.into_inner(), "foo");
+    /// }
+    /// ```
+    pub fn into_inner(self) -> T {
+        self.0
+    }
+}
+
+impl<T> fmt::Debug for TrySendError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            TrySendError::Full(..) => "Full(..)".fmt(f),
+            TrySendError::Disconnected(..) => "Disconnected(..)".fmt(f),
+        }
+    }
+}
+
+impl<T> fmt::Display for TrySendError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            TrySendError::Full(..) => "sending on a full channel".fmt(f),
+            TrySendError::Disconnected(..) => "sending on a disconnected channel".fmt(f),
+        }
+    }
+}
+
+impl<T: Send> error::Error for TrySendError<T> {}
+
+impl<T> From<SendError<T>> for TrySendError<T> {
+    fn from(err: SendError<T>) -> TrySendError<T> {
+        match err {
+            SendError(t) => TrySendError::Disconnected(t),
+        }
+    }
+}
+
+impl<T> TrySendError<T> {
+    /// Unwraps the message.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::bounded;
+    ///
+    /// let (s, r) = bounded(0);
+    ///
+    /// if let Err(err) = s.try_send("foo") {
+    ///     assert_eq!(err.into_inner(), "foo");
+    /// }
+    /// ```
+    pub fn into_inner(self) -> T {
+        match self {
+            TrySendError::Full(v) => v,
+            TrySendError::Disconnected(v) => v,
+        }
+    }
+
+    /// Returns `true` if the send operation failed because the channel is full.
+    pub fn is_full(&self) -> bool {
+        match self {
+            TrySendError::Full(_) => true,
+            _ => false,
+        }
+    }
+
+    /// Returns `true` if the send operation failed because the channel is disconnected.
+    pub fn is_disconnected(&self) -> bool {
+        match self {
+            TrySendError::Disconnected(_) => true,
+            _ => false,
+        }
+    }
+}
+
+impl<T> fmt::Debug for SendTimeoutError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "SendTimeoutError(..)".fmt(f)
+    }
+}
+
+impl<T> fmt::Display for SendTimeoutError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            SendTimeoutError::Timeout(..) => "timed out waiting on send operation".fmt(f),
+            SendTimeoutError::Disconnected(..) => "sending on a disconnected channel".fmt(f),
+        }
+    }
+}
+
+impl<T: Send> error::Error for SendTimeoutError<T> {}
+
+impl<T> From<SendError<T>> for SendTimeoutError<T> {
+    fn from(err: SendError<T>) -> SendTimeoutError<T> {
+        match err {
+            SendError(e) => SendTimeoutError::Disconnected(e),
+        }
+    }
+}
+
+impl<T> SendTimeoutError<T> {
+    /// Unwraps the message.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::Duration;
+    /// use crossbeam_channel::unbounded;
+    ///
+    /// let (s, r) = unbounded();
+    ///
+    /// if let Err(err) = s.send_timeout("foo", Duration::from_secs(1)) {
+    ///     assert_eq!(err.into_inner(), "foo");
+    /// }
+    /// ```
+    pub fn into_inner(self) -> T {
+        match self {
+            SendTimeoutError::Timeout(v) => v,
+            SendTimeoutError::Disconnected(v) => v,
+        }
+    }
+
+    /// Returns `true` if the send operation timed out.
+    pub fn is_timeout(&self) -> bool {
+        match self {
+            SendTimeoutError::Timeout(_) => true,
+            _ => false,
+        }
+    }
+
+    /// Returns `true` if the send operation failed because the channel is disconnected.
+    pub fn is_disconnected(&self) -> bool {
+        match self {
+            SendTimeoutError::Disconnected(_) => true,
+            _ => false,
+        }
+    }
+}
+
+impl fmt::Display for RecvError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "receiving on an empty and disconnected channel".fmt(f)
+    }
+}
+
+impl error::Error for RecvError {}
+
+impl fmt::Display for TryRecvError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            TryRecvError::Empty => "receiving on an empty channel".fmt(f),
+            TryRecvError::Disconnected => "receiving on an empty and disconnected channel".fmt(f),
+        }
+    }
+}
+
+impl error::Error for TryRecvError {}
+
+impl From<RecvError> for TryRecvError {
+    fn from(err: RecvError) -> TryRecvError {
+        match err {
+            RecvError => TryRecvError::Disconnected,
+        }
+    }
+}
+
+impl TryRecvError {
+    /// Returns `true` if the receive operation failed because the channel is empty.
+    #[allow(clippy::trivially_copy_pass_by_ref)]
+    pub fn is_empty(&self) -> bool {
+        match self {
+            TryRecvError::Empty => true,
+            _ => false,
+        }
+    }
+
+    /// Returns `true` if the receive operation failed because the channel is disconnected.
+    #[allow(clippy::trivially_copy_pass_by_ref)]
+    pub fn is_disconnected(&self) -> bool {
+        match self {
+            TryRecvError::Disconnected => true,
+            _ => false,
+        }
+    }
+}
+
+impl fmt::Display for RecvTimeoutError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            RecvTimeoutError::Timeout => "timed out waiting on receive operation".fmt(f),
+            RecvTimeoutError::Disconnected => "channel is empty and disconnected".fmt(f),
+        }
+    }
+}
+
+impl error::Error for RecvTimeoutError {}
+
+impl From<RecvError> for RecvTimeoutError {
+    fn from(err: RecvError) -> RecvTimeoutError {
+        match err {
+            RecvError => RecvTimeoutError::Disconnected,
+        }
+    }
+}
+
+impl RecvTimeoutError {
+    /// Returns `true` if the receive operation timed out.
+    #[allow(clippy::trivially_copy_pass_by_ref)]
+    pub fn is_timeout(&self) -> bool {
+        match self {
+            RecvTimeoutError::Timeout => true,
+            _ => false,
+        }
+    }
+
+    /// Returns `true` if the receive operation failed because the channel is disconnected.
+    #[allow(clippy::trivially_copy_pass_by_ref)]
+    pub fn is_disconnected(&self) -> bool {
+        match self {
+            RecvTimeoutError::Disconnected => true,
+            _ => false,
+        }
+    }
+}
+
+impl fmt::Display for TrySelectError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "all operations in select would block".fmt(f)
+    }
+}
+
+impl error::Error for TrySelectError {}
+
+impl fmt::Display for SelectTimeoutError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "timed out waiting on select".fmt(f)
+    }
+}
+
+impl error::Error for SelectTimeoutError {}
diff --git a/src/flavors/array.rs b/src/flavors/array.rs
new file mode 100644
index 0000000..323a200
--- /dev/null
+++ b/src/flavors/array.rs
@@ -0,0 +1,641 @@
+//! Bounded channel based on a preallocated array.
+//!
+//! This flavor has a fixed, positive capacity.
+//!
+//! The implementation is based on Dmitry Vyukov's bounded MPMC queue.
+//!
+//! Source:
+//!   - http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue
+//!   - https://docs.google.com/document/d/1yIAYmbvL3JxOKOjuCyon7JhW4cSv1wy5hC0ApeGMV9s/pub
+//!
+//! Copyright & License:
+//!   - Copyright (c) 2010-2011 Dmitry Vyukov
+//!   - Simplified BSD License and Apache License, Version 2.0
+//!   - http://www.1024cores.net/home/code-license
+
+use std::cell::UnsafeCell;
+use std::marker::PhantomData;
+use std::mem::{self, MaybeUninit};
+use std::ptr;
+use std::sync::atomic::{self, AtomicUsize, Ordering};
+use std::time::Instant;
+
+use crossbeam_utils::{Backoff, CachePadded};
+
+use crate::context::Context;
+use crate::err::{RecvTimeoutError, SendTimeoutError, TryRecvError, TrySendError};
+use crate::select::{Operation, SelectHandle, Selected, Token};
+use crate::waker::SyncWaker;
+
+/// A slot in a channel.
+struct Slot<T> {
+    /// The current stamp.
+    stamp: AtomicUsize,
+
+    /// The message in this slot.
+    msg: UnsafeCell<MaybeUninit<T>>,
+}
+
+/// The token type for the array flavor.
+#[derive(Debug)]
+pub struct ArrayToken {
+    /// Slot to read from or write to.
+    slot: *const u8,
+
+    /// Stamp to store into the slot after reading or writing.
+    stamp: usize,
+}
+
+impl Default for ArrayToken {
+    #[inline]
+    fn default() -> Self {
+        ArrayToken {
+            slot: ptr::null(),
+            stamp: 0,
+        }
+    }
+}
+
+/// Bounded channel based on a preallocated array.
+pub struct Channel<T> {
+    /// The head of the channel.
+    ///
+    /// This value is a "stamp" consisting of an index into the buffer, a mark bit, and a lap, but
+    /// packed into a single `usize`. The lower bits represent the index, while the upper bits
+    /// represent the lap. The mark bit in the head is always zero.
+    ///
+    /// Messages are popped from the head of the channel.
+    head: CachePadded<AtomicUsize>,
+
+    /// The tail of the channel.
+    ///
+    /// This value is a "stamp" consisting of an index into the buffer, a mark bit, and a lap, but
+    /// packed into a single `usize`. The lower bits represent the index, while the upper bits
+    /// represent the lap. The mark bit indicates that the channel is disconnected.
+    ///
+    /// Messages are pushed into the tail of the channel.
+    tail: CachePadded<AtomicUsize>,
+
+    /// The buffer holding slots.
+    buffer: *mut Slot<T>,
+
+    /// The channel capacity.
+    cap: usize,
+
+    /// A stamp with the value of `{ lap: 1, mark: 0, index: 0 }`.
+    one_lap: usize,
+
+    /// If this bit is set in the tail, that means the channel is disconnected.
+    mark_bit: usize,
+
+    /// Senders waiting while the channel is full.
+    senders: SyncWaker,
+
+    /// Receivers waiting while the channel is empty and not disconnected.
+    receivers: SyncWaker,
+
+    /// Indicates that dropping a `Channel<T>` may drop values of type `T`.
+    _marker: PhantomData<T>,
+}
+
+impl<T> Channel<T> {
+    /// Creates a bounded channel of capacity `cap`.
+    pub fn with_capacity(cap: usize) -> Self {
+        assert!(cap > 0, "capacity must be positive");
+
+        // Compute constants `mark_bit` and `one_lap`.
+        let mark_bit = (cap + 1).next_power_of_two();
+        let one_lap = mark_bit * 2;
+
+        // Head is initialized to `{ lap: 0, mark: 0, index: 0 }`.
+        let head = 0;
+        // Tail is initialized to `{ lap: 0, mark: 0, index: 0 }`.
+        let tail = 0;
+
+        // Allocate a buffer of `cap` slots initialized
+        // with stamps.
+        let buffer = {
+            let mut boxed: Box<[Slot<T>]> = (0..cap)
+                .map(|i| {
+                    // Set the stamp to `{ lap: 0, mark: 0, index: i }`.
+                    Slot {
+                        stamp: AtomicUsize::new(i),
+                        msg: UnsafeCell::new(MaybeUninit::uninit()),
+                    }
+                })
+                .collect();
+            let ptr = boxed.as_mut_ptr();
+            mem::forget(boxed);
+            ptr
+        };
+
+        Channel {
+            buffer,
+            cap,
+            one_lap,
+            mark_bit,
+            head: CachePadded::new(AtomicUsize::new(head)),
+            tail: CachePadded::new(AtomicUsize::new(tail)),
+            senders: SyncWaker::new(),
+            receivers: SyncWaker::new(),
+            _marker: PhantomData,
+        }
+    }
+
+    /// Returns a receiver handle to the channel.
+    pub fn receiver(&self) -> Receiver<'_, T> {
+        Receiver(self)
+    }
+
+    /// Returns a sender handle to the channel.
+    pub fn sender(&self) -> Sender<'_, T> {
+        Sender(self)
+    }
+
+    /// Attempts to reserve a slot for sending a message.
+    fn start_send(&self, token: &mut Token) -> bool {
+        let backoff = Backoff::new();
+        let mut tail = self.tail.load(Ordering::Relaxed);
+
+        loop {
+            // Check if the channel is disconnected.
+            if tail & self.mark_bit != 0 {
+                token.array.slot = ptr::null();
+                token.array.stamp = 0;
+                return true;
+            }
+
+            // Deconstruct the tail.
+            let index = tail & (self.mark_bit - 1);
+            let lap = tail & !(self.one_lap - 1);
+
+            // Inspect the corresponding slot.
+            let slot = unsafe { &*self.buffer.add(index) };
+            let stamp = slot.stamp.load(Ordering::Acquire);
+
+            // If the tail and the stamp match, we may attempt to push.
+            if tail == stamp {
+                let new_tail = if index + 1 < self.cap {
+                    // Same lap, incremented index.
+                    // Set to `{ lap: lap, mark: 0, index: index + 1 }`.
+                    tail + 1
+                } else {
+                    // One lap forward, index wraps around to zero.
+                    // Set to `{ lap: lap.wrapping_add(1), mark: 0, index: 0 }`.
+                    lap.wrapping_add(self.one_lap)
+                };
+
+                // Try moving the tail.
+                match self.tail.compare_exchange_weak(
+                    tail,
+                    new_tail,
+                    Ordering::SeqCst,
+                    Ordering::Relaxed,
+                ) {
+                    Ok(_) => {
+                        // Prepare the token for the follow-up call to `write`.
+                        token.array.slot = slot as *const Slot<T> as *const u8;
+                        token.array.stamp = tail + 1;
+                        return true;
+                    }
+                    Err(t) => {
+                        tail = t;
+                        backoff.spin();
+                    }
+                }
+            } else if stamp.wrapping_add(self.one_lap) == tail + 1 {
+                atomic::fence(Ordering::SeqCst);
+                let head = self.head.load(Ordering::Relaxed);
+
+                // If the head lags one lap behind the tail as well...
+                if head.wrapping_add(self.one_lap) == tail {
+                    // ...then the channel is full.
+                    return false;
+                }
+
+                backoff.spin();
+                tail = self.tail.load(Ordering::Relaxed);
+            } else {
+                // Snooze because we need to wait for the stamp to get updated.
+                backoff.snooze();
+                tail = self.tail.load(Ordering::Relaxed);
+            }
+        }
+    }
+
+    /// Writes a message into the channel.
+    pub unsafe fn write(&self, token: &mut Token, msg: T) -> Result<(), T> {
+        // If there is no slot, the channel is disconnected.
+        if token.array.slot.is_null() {
+            return Err(msg);
+        }
+
+        let slot: &Slot<T> = &*(token.array.slot as *const Slot<T>);
+
+        // Write the message into the slot and update the stamp.
+        slot.msg.get().write(MaybeUninit::new(msg));
+        slot.stamp.store(token.array.stamp, Ordering::Release);
+
+        // Wake a sleeping receiver.
+        self.receivers.notify();
+        Ok(())
+    }
+
+    /// Attempts to reserve a slot for receiving a message.
+    fn start_recv(&self, token: &mut Token) -> bool {
+        let backoff = Backoff::new();
+        let mut head = self.head.load(Ordering::Relaxed);
+
+        loop {
+            // Deconstruct the head.
+            let index = head & (self.mark_bit - 1);
+            let lap = head & !(self.one_lap - 1);
+
+            // Inspect the corresponding slot.
+            let slot = unsafe { &*self.buffer.add(index) };
+            let stamp = slot.stamp.load(Ordering::Acquire);
+
+            // If the the stamp is ahead of the head by 1, we may attempt to pop.
+            if head + 1 == stamp {
+                let new = if index + 1 < self.cap {
+                    // Same lap, incremented index.
+                    // Set to `{ lap: lap, mark: 0, index: index + 1 }`.
+                    head + 1
+                } else {
+                    // One lap forward, index wraps around to zero.
+                    // Set to `{ lap: lap.wrapping_add(1), mark: 0, index: 0 }`.
+                    lap.wrapping_add(self.one_lap)
+                };
+
+                // Try moving the head.
+                match self.head.compare_exchange_weak(
+                    head,
+                    new,
+                    Ordering::SeqCst,
+                    Ordering::Relaxed,
+                ) {
+                    Ok(_) => {
+                        // Prepare the token for the follow-up call to `read`.
+                        token.array.slot = slot as *const Slot<T> as *const u8;
+                        token.array.stamp = head.wrapping_add(self.one_lap);
+                        return true;
+                    }
+                    Err(h) => {
+                        head = h;
+                        backoff.spin();
+                    }
+                }
+            } else if stamp == head {
+                atomic::fence(Ordering::SeqCst);
+                let tail = self.tail.load(Ordering::Relaxed);
+
+                // If the tail equals the head, that means the channel is empty.
+                if (tail & !self.mark_bit) == head {
+                    // If the channel is disconnected...
+                    if tail & self.mark_bit != 0 {
+                        // ...then receive an error.
+                        token.array.slot = ptr::null();
+                        token.array.stamp = 0;
+                        return true;
+                    } else {
+                        // Otherwise, the receive operation is not ready.
+                        return false;
+                    }
+                }
+
+                backoff.spin();
+                head = self.head.load(Ordering::Relaxed);
+            } else {
+                // Snooze because we need to wait for the stamp to get updated.
+                backoff.snooze();
+                head = self.head.load(Ordering::Relaxed);
+            }
+        }
+    }
+
+    /// Reads a message from the channel.
+    pub unsafe fn read(&self, token: &mut Token) -> Result<T, ()> {
+        if token.array.slot.is_null() {
+            // The channel is disconnected.
+            return Err(());
+        }
+
+        let slot: &Slot<T> = &*(token.array.slot as *const Slot<T>);
+
+        // Read the message from the slot and update the stamp.
+        let msg = slot.msg.get().read().assume_init();
+        slot.stamp.store(token.array.stamp, Ordering::Release);
+
+        // Wake a sleeping sender.
+        self.senders.notify();
+        Ok(msg)
+    }
+
+    /// Attempts to send a message into the channel.
+    pub fn try_send(&self, msg: T) -> Result<(), TrySendError<T>> {
+        let token = &mut Token::default();
+        if self.start_send(token) {
+            unsafe { self.write(token, msg).map_err(TrySendError::Disconnected) }
+        } else {
+            Err(TrySendError::Full(msg))
+        }
+    }
+
+    /// Sends a message into the channel.
+    pub fn send(&self, msg: T, deadline: Option<Instant>) -> Result<(), SendTimeoutError<T>> {
+        let token = &mut Token::default();
+        loop {
+            // Try sending a message several times.
+            let backoff = Backoff::new();
+            loop {
+                if self.start_send(token) {
+                    let res = unsafe { self.write(token, msg) };
+                    return res.map_err(SendTimeoutError::Disconnected);
+                }
+
+                if backoff.is_completed() {
+                    break;
+                } else {
+                    backoff.snooze();
+                }
+            }
+
+            if let Some(d) = deadline {
+                if Instant::now() >= d {
+                    return Err(SendTimeoutError::Timeout(msg));
+                }
+            }
+
+            Context::with(|cx| {
+                // Prepare for blocking until a receiver wakes us up.
+                let oper = Operation::hook(token);
+                self.senders.register(oper, cx);
+
+                // Has the channel become ready just now?
+                if !self.is_full() || self.is_disconnected() {
+                    let _ = cx.try_select(Selected::Aborted);
+                }
+
+                // Block the current thread.
+                let sel = cx.wait_until(deadline);
+
+                match sel {
+                    Selected::Waiting => unreachable!(),
+                    Selected::Aborted | Selected::Disconnected => {
+                        self.senders.unregister(oper).unwrap();
+                    }
+                    Selected::Operation(_) => {}
+                }
+            });
+        }
+    }
+
+    /// Attempts to receive a message without blocking.
+    pub fn try_recv(&self) -> Result<T, TryRecvError> {
+        let token = &mut Token::default();
+
+        if self.start_recv(token) {
+            unsafe { self.read(token).map_err(|_| TryRecvError::Disconnected) }
+        } else {
+            Err(TryRecvError::Empty)
+        }
+    }
+
+    /// Receives a message from the channel.
+    pub fn recv(&self, deadline: Option<Instant>) -> Result<T, RecvTimeoutError> {
+        let token = &mut Token::default();
+        loop {
+            // Try receiving a message several times.
+            let backoff = Backoff::new();
+            loop {
+                if self.start_recv(token) {
+                    let res = unsafe { self.read(token) };
+                    return res.map_err(|_| RecvTimeoutError::Disconnected);
+                }
+
+                if backoff.is_completed() {
+                    break;
+                } else {
+                    backoff.snooze();
+                }
+            }
+
+            if let Some(d) = deadline {
+                if Instant::now() >= d {
+                    return Err(RecvTimeoutError::Timeout);
+                }
+            }
+
+            Context::with(|cx| {
+                // Prepare for blocking until a sender wakes us up.
+                let oper = Operation::hook(token);
+                self.receivers.register(oper, cx);
+
+                // Has the channel become ready just now?
+                if !self.is_empty() || self.is_disconnected() {
+                    let _ = cx.try_select(Selected::Aborted);
+                }
+
+                // Block the current thread.
+                let sel = cx.wait_until(deadline);
+
+                match sel {
+                    Selected::Waiting => unreachable!(),
+                    Selected::Aborted | Selected::Disconnected => {
+                        self.receivers.unregister(oper).unwrap();
+                        // If the channel was disconnected, we still have to check for remaining
+                        // messages.
+                    }
+                    Selected::Operation(_) => {}
+                }
+            });
+        }
+    }
+
+    /// Returns the current number of messages inside the channel.
+    pub fn len(&self) -> usize {
+        loop {
+            // Load the tail, then load the head.
+            let tail = self.tail.load(Ordering::SeqCst);
+            let head = self.head.load(Ordering::SeqCst);
+
+            // If the tail didn't change, we've got consistent values to work with.
+            if self.tail.load(Ordering::SeqCst) == tail {
+                let hix = head & (self.mark_bit - 1);
+                let tix = tail & (self.mark_bit - 1);
+
+                return if hix < tix {
+                    tix - hix
+                } else if hix > tix {
+                    self.cap - hix + tix
+                } else if (tail & !self.mark_bit) == head {
+                    0
+                } else {
+                    self.cap
+                };
+            }
+        }
+    }
+
+    /// Returns the capacity of the channel.
+    pub fn capacity(&self) -> Option<usize> {
+        Some(self.cap)
+    }
+
+    /// Disconnects the channel and wakes up all blocked senders and receivers.
+    ///
+    /// Returns `true` if this call disconnected the channel.
+    pub fn disconnect(&self) -> bool {
+        let tail = self.tail.fetch_or(self.mark_bit, Ordering::SeqCst);
+
+        if tail & self.mark_bit == 0 {
+            self.senders.disconnect();
+            self.receivers.disconnect();
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Returns `true` if the channel is disconnected.
+    pub fn is_disconnected(&self) -> bool {
+        self.tail.load(Ordering::SeqCst) & self.mark_bit != 0
+    }
+
+    /// Returns `true` if the channel is empty.
+    pub fn is_empty(&self) -> bool {
+        let head = self.head.load(Ordering::SeqCst);
+        let tail = self.tail.load(Ordering::SeqCst);
+
+        // Is the tail equal to the head?
+        //
+        // Note: If the head changes just before we load the tail, that means there was a moment
+        // when the channel was not empty, so it is safe to just return `false`.
+        (tail & !self.mark_bit) == head
+    }
+
+    /// Returns `true` if the channel is full.
+    pub fn is_full(&self) -> bool {
+        let tail = self.tail.load(Ordering::SeqCst);
+        let head = self.head.load(Ordering::SeqCst);
+
+        // Is the head lagging one lap behind tail?
+        //
+        // Note: If the tail changes just before we load the head, that means there was a moment
+        // when the channel was not full, so it is safe to just return `false`.
+        head.wrapping_add(self.one_lap) == tail & !self.mark_bit
+    }
+}
+
+impl<T> Drop for Channel<T> {
+    fn drop(&mut self) {
+        // Get the index of the head.
+        let hix = self.head.load(Ordering::Relaxed) & (self.mark_bit - 1);
+
+        // Loop over all slots that hold a message and drop them.
+        for i in 0..self.len() {
+            // Compute the index of the next slot holding a message.
+            let index = if hix + i < self.cap {
+                hix + i
+            } else {
+                hix + i - self.cap
+            };
+
+            unsafe {
+                let p = {
+                    let slot = &mut *self.buffer.add(index);
+                    let msg = &mut *slot.msg.get();
+                    msg.as_mut_ptr()
+                };
+                p.drop_in_place();
+            }
+        }
+
+        // Finally, deallocate the buffer, but don't run any destructors.
+        unsafe {
+            // Create a slice from the buffer to make
+            // a fat pointer. Then, use Box::from_raw
+            // to deallocate it.
+            let ptr = std::slice::from_raw_parts_mut(self.buffer, self.cap) as *mut [Slot<T>];
+            Box::from_raw(ptr);
+        }
+    }
+}
+
+/// Receiver handle to a channel.
+pub struct Receiver<'a, T>(&'a Channel<T>);
+
+/// Sender handle to a channel.
+pub struct Sender<'a, T>(&'a Channel<T>);
+
+impl<T> SelectHandle for Receiver<'_, T> {
+    fn try_select(&self, token: &mut Token) -> bool {
+        self.0.start_recv(token)
+    }
+
+    fn deadline(&self) -> Option<Instant> {
+        None
+    }
+
+    fn register(&self, oper: Operation, cx: &Context) -> bool {
+        self.0.receivers.register(oper, cx);
+        self.is_ready()
+    }
+
+    fn unregister(&self, oper: Operation) {
+        self.0.receivers.unregister(oper);
+    }
+
+    fn accept(&self, token: &mut Token, _cx: &Context) -> bool {
+        self.try_select(token)
+    }
+
+    fn is_ready(&self) -> bool {
+        !self.0.is_empty() || self.0.is_disconnected()
+    }
+
+    fn watch(&self, oper: Operation, cx: &Context) -> bool {
+        self.0.receivers.watch(oper, cx);
+        self.is_ready()
+    }
+
+    fn unwatch(&self, oper: Operation) {
+        self.0.receivers.unwatch(oper);
+    }
+}
+
+impl<T> SelectHandle for Sender<'_, T> {
+    fn try_select(&self, token: &mut Token) -> bool {
+        self.0.start_send(token)
+    }
+
+    fn deadline(&self) -> Option<Instant> {
+        None
+    }
+
+    fn register(&self, oper: Operation, cx: &Context) -> bool {
+        self.0.senders.register(oper, cx);
+        self.is_ready()
+    }
+
+    fn unregister(&self, oper: Operation) {
+        self.0.senders.unregister(oper);
+    }
+
+    fn accept(&self, token: &mut Token, _cx: &Context) -> bool {
+        self.try_select(token)
+    }
+
+    fn is_ready(&self) -> bool {
+        !self.0.is_full() || self.0.is_disconnected()
+    }
+
+    fn watch(&self, oper: Operation, cx: &Context) -> bool {
+        self.0.senders.watch(oper, cx);
+        self.is_ready()
+    }
+
+    fn unwatch(&self, oper: Operation) {
+        self.0.senders.unwatch(oper);
+    }
+}
diff --git a/src/flavors/at.rs b/src/flavors/at.rs
new file mode 100644
index 0000000..a2b1b57
--- /dev/null
+++ b/src/flavors/at.rs
@@ -0,0 +1,202 @@
+//! Channel that delivers a message at a certain moment in time.
+//!
+//! Messages cannot be sent into this kind of channel; they are materialized on demand.
+
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::thread;
+use std::time::{Duration, Instant};
+
+use crate::context::Context;
+use crate::err::{RecvTimeoutError, TryRecvError};
+use crate::select::{Operation, SelectHandle, Token};
+use crate::utils;
+
+/// Result of a receive operation.
+pub type AtToken = Option<Instant>;
+
+/// Channel that delivers a message at a certain moment in time
+pub struct Channel {
+    /// The instant at which the message will be delivered.
+    delivery_time: Instant,
+
+    /// `true` if the message has been received.
+    received: AtomicBool,
+}
+
+impl Channel {
+    /// Creates a channel that delivers a message at a certain instant in time.
+    #[inline]
+    pub fn new_deadline(when: Instant) -> Self {
+        Channel {
+            delivery_time: when,
+            received: AtomicBool::new(false),
+        }
+    }
+    /// Creates a channel that delivers a message after a certain duration of time.
+    #[inline]
+    pub fn new_timeout(dur: Duration) -> Self {
+        Self::new_deadline(Instant::now() + dur)
+    }
+
+    /// Attempts to receive a message without blocking.
+    #[inline]
+    pub fn try_recv(&self) -> Result<Instant, TryRecvError> {
+        // We use relaxed ordering because this is just an optional optimistic check.
+        if self.received.load(Ordering::Relaxed) {
+            // The message has already been received.
+            return Err(TryRecvError::Empty);
+        }
+
+        if Instant::now() < self.delivery_time {
+            // The message was not delivered yet.
+            return Err(TryRecvError::Empty);
+        }
+
+        // Try receiving the message if it is still available.
+        if !self.received.swap(true, Ordering::SeqCst) {
+            // Success! Return delivery time as the message.
+            Ok(self.delivery_time)
+        } else {
+            // The message was already received.
+            Err(TryRecvError::Empty)
+        }
+    }
+
+    /// Receives a message from the channel.
+    #[inline]
+    pub fn recv(&self, deadline: Option<Instant>) -> Result<Instant, RecvTimeoutError> {
+        // We use relaxed ordering because this is just an optional optimistic check.
+        if self.received.load(Ordering::Relaxed) {
+            // The message has already been received.
+            utils::sleep_until(deadline);
+            return Err(RecvTimeoutError::Timeout);
+        }
+
+        // Wait until the message is received or the deadline is reached.
+        loop {
+            let now = Instant::now();
+
+            let deadline = match deadline {
+                // Check if we can receive the next message.
+                _ if now >= self.delivery_time => break,
+                // Check if the timeout deadline has been reached.
+                Some(d) if now >= d => return Err(RecvTimeoutError::Timeout),
+
+                // Sleep until one of the above happens
+                Some(d) if d < self.delivery_time => d,
+                _ => self.delivery_time,
+            };
+
+            thread::sleep(deadline - now);
+        }
+
+        // Try receiving the message if it is still available.
+        if !self.received.swap(true, Ordering::SeqCst) {
+            // Success! Return the message, which is the instant at which it was delivered.
+            Ok(self.delivery_time)
+        } else {
+            // The message was already received. Block forever.
+            utils::sleep_until(None);
+            unreachable!()
+        }
+    }
+
+    /// Reads a message from the channel.
+    #[inline]
+    pub unsafe fn read(&self, token: &mut Token) -> Result<Instant, ()> {
+        token.at.ok_or(())
+    }
+
+    /// Returns `true` if the channel is empty.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        // We use relaxed ordering because this is just an optional optimistic check.
+        if self.received.load(Ordering::Relaxed) {
+            return true;
+        }
+
+        // If the delivery time hasn't been reached yet, the channel is empty.
+        if Instant::now() < self.delivery_time {
+            return true;
+        }
+
+        // The delivery time has been reached. The channel is empty only if the message has already
+        // been received.
+        self.received.load(Ordering::SeqCst)
+    }
+
+    /// Returns `true` if the channel is full.
+    #[inline]
+    pub fn is_full(&self) -> bool {
+        !self.is_empty()
+    }
+
+    /// Returns the number of messages in the channel.
+    #[inline]
+    pub fn len(&self) -> usize {
+        if self.is_empty() {
+            0
+        } else {
+            1
+        }
+    }
+
+    /// Returns the capacity of the channel.
+    #[inline]
+    pub fn capacity(&self) -> Option<usize> {
+        Some(1)
+    }
+}
+
+impl SelectHandle for Channel {
+    #[inline]
+    fn try_select(&self, token: &mut Token) -> bool {
+        match self.try_recv() {
+            Ok(msg) => {
+                token.at = Some(msg);
+                true
+            }
+            Err(TryRecvError::Disconnected) => {
+                token.at = None;
+                true
+            }
+            Err(TryRecvError::Empty) => false,
+        }
+    }
+
+    #[inline]
+    fn deadline(&self) -> Option<Instant> {
+        // We use relaxed ordering because this is just an optional optimistic check.
+        if self.received.load(Ordering::Relaxed) {
+            None
+        } else {
+            Some(self.delivery_time)
+        }
+    }
+
+    #[inline]
+    fn register(&self, _oper: Operation, _cx: &Context) -> bool {
+        self.is_ready()
+    }
+
+    #[inline]
+    fn unregister(&self, _oper: Operation) {}
+
+    #[inline]
+    fn accept(&self, token: &mut Token, _cx: &Context) -> bool {
+        self.try_select(token)
+    }
+
+    #[inline]
+    fn is_ready(&self) -> bool {
+        !self.is_empty()
+    }
+
+    #[inline]
+    fn watch(&self, _oper: Operation, _cx: &Context) -> bool {
+        self.is_ready()
+    }
+
+    #[inline]
+    fn unwatch(&self, _oper: Operation) {}
+}
diff --git a/src/flavors/list.rs b/src/flavors/list.rs
new file mode 100644
index 0000000..532e8b6
--- /dev/null
+++ b/src/flavors/list.rs
@@ -0,0 +1,669 @@
+//! Unbounded channel implemented as a linked list.
+
+use std::cell::UnsafeCell;
+use std::marker::PhantomData;
+use std::mem::MaybeUninit;
+use std::ptr;
+use std::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
+use std::time::Instant;
+
+use crossbeam_utils::{Backoff, CachePadded};
+
+use crate::context::Context;
+use crate::err::{RecvTimeoutError, SendTimeoutError, TryRecvError, TrySendError};
+use crate::select::{Operation, SelectHandle, Selected, Token};
+use crate::waker::SyncWaker;
+
+// TODO(stjepang): Once we bump the minimum required Rust version to 1.28 or newer, re-apply the
+// following changes by @kleimkuhler:
+//
+// 1. https://github.com/crossbeam-rs/crossbeam-channel/pull/100
+// 2. https://github.com/crossbeam-rs/crossbeam-channel/pull/101
+
+// Bits indicating the state of a slot:
+// * If a message has been written into the slot, `WRITE` is set.
+// * If a message has been read from the slot, `READ` is set.
+// * If the block is being destroyed, `DESTROY` is set.
+const WRITE: usize = 1;
+const READ: usize = 2;
+const DESTROY: usize = 4;
+
+// Each block covers one "lap" of indices.
+const LAP: usize = 32;
+// The maximum number of messages a block can hold.
+const BLOCK_CAP: usize = LAP - 1;
+// How many lower bits are reserved for metadata.
+const SHIFT: usize = 1;
+// Has two different purposes:
+// * If set in head, indicates that the block is not the last one.
+// * If set in tail, indicates that the channel is disconnected.
+const MARK_BIT: usize = 1;
+
+/// A slot in a block.
+struct Slot<T> {
+    /// The message.
+    msg: UnsafeCell<MaybeUninit<T>>,
+
+    /// The state of the slot.
+    state: AtomicUsize,
+}
+
+impl<T> Slot<T> {
+    /// Waits until a message is written into the slot.
+    fn wait_write(&self) {
+        let backoff = Backoff::new();
+        while self.state.load(Ordering::Acquire) & WRITE == 0 {
+            backoff.snooze();
+        }
+    }
+}
+
+/// A block in a linked list.
+///
+/// Each block in the list can hold up to `BLOCK_CAP` messages.
+struct Block<T> {
+    /// The next block in the linked list.
+    next: AtomicPtr<Block<T>>,
+
+    /// Slots for messages.
+    slots: [Slot<T>; BLOCK_CAP],
+}
+
+impl<T> Block<T> {
+    /// Creates an empty block.
+    fn new() -> Block<T> {
+        // SAFETY: This is safe because:
+        //  [1] `Block::next` (AtomicPtr) may be safely zero initialized.
+        //  [2] `Block::slots` (Array) may be safely zero initialized because of [3, 4].
+        //  [3] `Slot::msg` (UnsafeCell) may be safely zero initialized because it
+        //       holds a MaybeUninit.
+        //  [4] `Slot::state` (AtomicUsize) may be safely zero initialized.
+        unsafe { MaybeUninit::zeroed().assume_init() }
+    }
+
+    /// Waits until the next pointer is set.
+    fn wait_next(&self) -> *mut Block<T> {
+        let backoff = Backoff::new();
+        loop {
+            let next = self.next.load(Ordering::Acquire);
+            if !next.is_null() {
+                return next;
+            }
+            backoff.snooze();
+        }
+    }
+
+    /// Sets the `DESTROY` bit in slots starting from `start` and destroys the block.
+    unsafe fn destroy(this: *mut Block<T>, start: usize) {
+        // It is not necessary to set the `DESTROY` bit in the last slot because that slot has
+        // begun destruction of the block.
+        for i in start..BLOCK_CAP - 1 {
+            let slot = (*this).slots.get_unchecked(i);
+
+            // Mark the `DESTROY` bit if a thread is still using the slot.
+            if slot.state.load(Ordering::Acquire) & READ == 0
+                && slot.state.fetch_or(DESTROY, Ordering::AcqRel) & READ == 0
+            {
+                // If a thread is still using the slot, it will continue destruction of the block.
+                return;
+            }
+        }
+
+        // No thread is using the block, now it is safe to destroy it.
+        drop(Box::from_raw(this));
+    }
+}
+
+/// A position in a channel.
+#[derive(Debug)]
+struct Position<T> {
+    /// The index in the channel.
+    index: AtomicUsize,
+
+    /// The block in the linked list.
+    block: AtomicPtr<Block<T>>,
+}
+
+/// The token type for the list flavor.
+#[derive(Debug)]
+pub struct ListToken {
+    /// The block of slots.
+    block: *const u8,
+
+    /// The offset into the block.
+    offset: usize,
+}
+
+impl Default for ListToken {
+    #[inline]
+    fn default() -> Self {
+        ListToken {
+            block: ptr::null(),
+            offset: 0,
+        }
+    }
+}
+
+/// Unbounded channel implemented as a linked list.
+///
+/// Each message sent into the channel is assigned a sequence number, i.e. an index. Indices are
+/// represented as numbers of type `usize` and wrap on overflow.
+///
+/// Consecutive messages are grouped into blocks in order to put less pressure on the allocator and
+/// improve cache efficiency.
+pub struct Channel<T> {
+    /// The head of the channel.
+    head: CachePadded<Position<T>>,
+
+    /// The tail of the channel.
+    tail: CachePadded<Position<T>>,
+
+    /// Receivers waiting while the channel is empty and not disconnected.
+    receivers: SyncWaker,
+
+    /// Indicates that dropping a `Channel<T>` may drop messages of type `T`.
+    _marker: PhantomData<T>,
+}
+
+impl<T> Channel<T> {
+    /// Creates a new unbounded channel.
+    pub fn new() -> Self {
+        Channel {
+            head: CachePadded::new(Position {
+                block: AtomicPtr::new(ptr::null_mut()),
+                index: AtomicUsize::new(0),
+            }),
+            tail: CachePadded::new(Position {
+                block: AtomicPtr::new(ptr::null_mut()),
+                index: AtomicUsize::new(0),
+            }),
+            receivers: SyncWaker::new(),
+            _marker: PhantomData,
+        }
+    }
+
+    /// Returns a receiver handle to the channel.
+    pub fn receiver(&self) -> Receiver<'_, T> {
+        Receiver(self)
+    }
+
+    /// Returns a sender handle to the channel.
+    pub fn sender(&self) -> Sender<'_, T> {
+        Sender(self)
+    }
+
+    /// Attempts to reserve a slot for sending a message.
+    fn start_send(&self, token: &mut Token) -> bool {
+        let backoff = Backoff::new();
+        let mut tail = self.tail.index.load(Ordering::Acquire);
+        let mut block = self.tail.block.load(Ordering::Acquire);
+        let mut next_block = None;
+
+        loop {
+            // Check if the channel is disconnected.
+            if tail & MARK_BIT != 0 {
+                token.list.block = ptr::null();
+                return true;
+            }
+
+            // Calculate the offset of the index into the block.
+            let offset = (tail >> SHIFT) % LAP;
+
+            // If we reached the end of the block, wait until the next one is installed.
+            if offset == BLOCK_CAP {
+                backoff.snooze();
+                tail = self.tail.index.load(Ordering::Acquire);
+                block = self.tail.block.load(Ordering::Acquire);
+                continue;
+            }
+
+            // If we're going to have to install the next block, allocate it in advance in order to
+            // make the wait for other threads as short as possible.
+            if offset + 1 == BLOCK_CAP && next_block.is_none() {
+                next_block = Some(Box::new(Block::<T>::new()));
+            }
+
+            // If this is the first message to be sent into the channel, we need to allocate the
+            // first block and install it.
+            if block.is_null() {
+                let new = Box::into_raw(Box::new(Block::<T>::new()));
+
+                if self
+                    .tail
+                    .block
+                    .compare_and_swap(block, new, Ordering::Release)
+                    == block
+                {
+                    self.head.block.store(new, Ordering::Release);
+                    block = new;
+                } else {
+                    next_block = unsafe { Some(Box::from_raw(new)) };
+                    tail = self.tail.index.load(Ordering::Acquire);
+                    block = self.tail.block.load(Ordering::Acquire);
+                    continue;
+                }
+            }
+
+            let new_tail = tail + (1 << SHIFT);
+
+            // Try advancing the tail forward.
+            match self.tail.index.compare_exchange_weak(
+                tail,
+                new_tail,
+                Ordering::SeqCst,
+                Ordering::Acquire,
+            ) {
+                Ok(_) => unsafe {
+                    // If we've reached the end of the block, install the next one.
+                    if offset + 1 == BLOCK_CAP {
+                        let next_block = Box::into_raw(next_block.unwrap());
+                        self.tail.block.store(next_block, Ordering::Release);
+                        self.tail.index.fetch_add(1 << SHIFT, Ordering::Release);
+                        (*block).next.store(next_block, Ordering::Release);
+                    }
+
+                    token.list.block = block as *const u8;
+                    token.list.offset = offset;
+                    return true;
+                },
+                Err(t) => {
+                    tail = t;
+                    block = self.tail.block.load(Ordering::Acquire);
+                    backoff.spin();
+                }
+            }
+        }
+    }
+
+    /// Writes a message into the channel.
+    pub unsafe fn write(&self, token: &mut Token, msg: T) -> Result<(), T> {
+        // If there is no slot, the channel is disconnected.
+        if token.list.block.is_null() {
+            return Err(msg);
+        }
+
+        // Write the message into the slot.
+        let block = token.list.block as *mut Block<T>;
+        let offset = token.list.offset;
+        let slot = (*block).slots.get_unchecked(offset);
+        slot.msg.get().write(MaybeUninit::new(msg));
+        slot.state.fetch_or(WRITE, Ordering::Release);
+
+        // Wake a sleeping receiver.
+        self.receivers.notify();
+        Ok(())
+    }
+
+    /// Attempts to reserve a slot for receiving a message.
+    fn start_recv(&self, token: &mut Token) -> bool {
+        let backoff = Backoff::new();
+        let mut head = self.head.index.load(Ordering::Acquire);
+        let mut block = self.head.block.load(Ordering::Acquire);
+
+        loop {
+            // Calculate the offset of the index into the block.
+            let offset = (head >> SHIFT) % LAP;
+
+            // If we reached the end of the block, wait until the next one is installed.
+            if offset == BLOCK_CAP {
+                backoff.snooze();
+                head = self.head.index.load(Ordering::Acquire);
+                block = self.head.block.load(Ordering::Acquire);
+                continue;
+            }
+
+            let mut new_head = head + (1 << SHIFT);
+
+            if new_head & MARK_BIT == 0 {
+                atomic::fence(Ordering::SeqCst);
+                let tail = self.tail.index.load(Ordering::Relaxed);
+
+                // If the tail equals the head, that means the channel is empty.
+                if head >> SHIFT == tail >> SHIFT {
+                    // If the channel is disconnected...
+                    if tail & MARK_BIT != 0 {
+                        // ...then receive an error.
+                        token.list.block = ptr::null();
+                        return true;
+                    } else {
+                        // Otherwise, the receive operation is not ready.
+                        return false;
+                    }
+                }
+
+                // If head and tail are not in the same block, set `MARK_BIT` in head.
+                if (head >> SHIFT) / LAP != (tail >> SHIFT) / LAP {
+                    new_head |= MARK_BIT;
+                }
+            }
+
+            // The block can be null here only if the first message is being sent into the channel.
+            // In that case, just wait until it gets initialized.
+            if block.is_null() {
+                backoff.snooze();
+                head = self.head.index.load(Ordering::Acquire);
+                block = self.head.block.load(Ordering::Acquire);
+                continue;
+            }
+
+            // Try moving the head index forward.
+            match self.head.index.compare_exchange_weak(
+                head,
+                new_head,
+                Ordering::SeqCst,
+                Ordering::Acquire,
+            ) {
+                Ok(_) => unsafe {
+                    // If we've reached the end of the block, move to the next one.
+                    if offset + 1 == BLOCK_CAP {
+                        let next = (*block).wait_next();
+                        let mut next_index = (new_head & !MARK_BIT).wrapping_add(1 << SHIFT);
+                        if !(*next).next.load(Ordering::Relaxed).is_null() {
+                            next_index |= MARK_BIT;
+                        }
+
+                        self.head.block.store(next, Ordering::Release);
+                        self.head.index.store(next_index, Ordering::Release);
+                    }
+
+                    token.list.block = block as *const u8;
+                    token.list.offset = offset;
+                    return true;
+                },
+                Err(h) => {
+                    head = h;
+                    block = self.head.block.load(Ordering::Acquire);
+                    backoff.spin();
+                }
+            }
+        }
+    }
+
+    /// Reads a message from the channel.
+    pub unsafe fn read(&self, token: &mut Token) -> Result<T, ()> {
+        if token.list.block.is_null() {
+            // The channel is disconnected.
+            return Err(());
+        }
+
+        // Read the message.
+        let block = token.list.block as *mut Block<T>;
+        let offset = token.list.offset;
+        let slot = (*block).slots.get_unchecked(offset);
+        slot.wait_write();
+        let msg = slot.msg.get().read().assume_init();
+
+        // Destroy the block if we've reached the end, or if another thread wanted to destroy but
+        // couldn't because we were busy reading from the slot.
+        if offset + 1 == BLOCK_CAP {
+            Block::destroy(block, 0);
+        } else if slot.state.fetch_or(READ, Ordering::AcqRel) & DESTROY != 0 {
+            Block::destroy(block, offset + 1);
+        }
+
+        Ok(msg)
+    }
+
+    /// Attempts to send a message into the channel.
+    pub fn try_send(&self, msg: T) -> Result<(), TrySendError<T>> {
+        self.send(msg, None).map_err(|err| match err {
+            SendTimeoutError::Disconnected(msg) => TrySendError::Disconnected(msg),
+            SendTimeoutError::Timeout(_) => unreachable!(),
+        })
+    }
+
+    /// Sends a message into the channel.
+    pub fn send(&self, msg: T, _deadline: Option<Instant>) -> Result<(), SendTimeoutError<T>> {
+        let token = &mut Token::default();
+        assert!(self.start_send(token));
+        unsafe {
+            self.write(token, msg)
+                .map_err(SendTimeoutError::Disconnected)
+        }
+    }
+
+    /// Attempts to receive a message without blocking.
+    pub fn try_recv(&self) -> Result<T, TryRecvError> {
+        let token = &mut Token::default();
+
+        if self.start_recv(token) {
+            unsafe { self.read(token).map_err(|_| TryRecvError::Disconnected) }
+        } else {
+            Err(TryRecvError::Empty)
+        }
+    }
+
+    /// Receives a message from the channel.
+    pub fn recv(&self, deadline: Option<Instant>) -> Result<T, RecvTimeoutError> {
+        let token = &mut Token::default();
+        loop {
+            // Try receiving a message several times.
+            let backoff = Backoff::new();
+            loop {
+                if self.start_recv(token) {
+                    unsafe {
+                        return self.read(token).map_err(|_| RecvTimeoutError::Disconnected);
+                    }
+                }
+
+                if backoff.is_completed() {
+                    break;
+                } else {
+                    backoff.snooze();
+                }
+            }
+
+            if let Some(d) = deadline {
+                if Instant::now() >= d {
+                    return Err(RecvTimeoutError::Timeout);
+                }
+            }
+
+            // Prepare for blocking until a sender wakes us up.
+            Context::with(|cx| {
+                let oper = Operation::hook(token);
+                self.receivers.register(oper, cx);
+
+                // Has the channel become ready just now?
+                if !self.is_empty() || self.is_disconnected() {
+                    let _ = cx.try_select(Selected::Aborted);
+                }
+
+                // Block the current thread.
+                let sel = cx.wait_until(deadline);
+
+                match sel {
+                    Selected::Waiting => unreachable!(),
+                    Selected::Aborted | Selected::Disconnected => {
+                        self.receivers.unregister(oper).unwrap();
+                        // If the channel was disconnected, we still have to check for remaining
+                        // messages.
+                    }
+                    Selected::Operation(_) => {}
+                }
+            });
+        }
+    }
+
+    /// Returns the current number of messages inside the channel.
+    pub fn len(&self) -> usize {
+        loop {
+            // Load the tail index, then load the head index.
+            let mut tail = self.tail.index.load(Ordering::SeqCst);
+            let mut head = self.head.index.load(Ordering::SeqCst);
+
+            // If the tail index didn't change, we've got consistent indices to work with.
+            if self.tail.index.load(Ordering::SeqCst) == tail {
+                // Erase the lower bits.
+                tail &= !((1 << SHIFT) - 1);
+                head &= !((1 << SHIFT) - 1);
+
+                // Fix up indices if they fall onto block ends.
+                if (tail >> SHIFT) & (LAP - 1) == LAP - 1 {
+                    tail = tail.wrapping_add(1 << SHIFT);
+                }
+                if (head >> SHIFT) & (LAP - 1) == LAP - 1 {
+                    head = head.wrapping_add(1 << SHIFT);
+                }
+
+                // Rotate indices so that head falls into the first block.
+                let lap = (head >> SHIFT) / LAP;
+                tail = tail.wrapping_sub((lap * LAP) << SHIFT);
+                head = head.wrapping_sub((lap * LAP) << SHIFT);
+
+                // Remove the lower bits.
+                tail >>= SHIFT;
+                head >>= SHIFT;
+
+                // Return the difference minus the number of blocks between tail and head.
+                return tail - head - tail / LAP;
+            }
+        }
+    }
+
+    /// Returns the capacity of the channel.
+    pub fn capacity(&self) -> Option<usize> {
+        None
+    }
+
+    /// Disconnects the channel and wakes up all blocked receivers.
+    ///
+    /// Returns `true` if this call disconnected the channel.
+    pub fn disconnect(&self) -> bool {
+        let tail = self.tail.index.fetch_or(MARK_BIT, Ordering::SeqCst);
+
+        if tail & MARK_BIT == 0 {
+            self.receivers.disconnect();
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Returns `true` if the channel is disconnected.
+    pub fn is_disconnected(&self) -> bool {
+        self.tail.index.load(Ordering::SeqCst) & MARK_BIT != 0
+    }
+
+    /// Returns `true` if the channel is empty.
+    pub fn is_empty(&self) -> bool {
+        let head = self.head.index.load(Ordering::SeqCst);
+        let tail = self.tail.index.load(Ordering::SeqCst);
+        head >> SHIFT == tail >> SHIFT
+    }
+
+    /// Returns `true` if the channel is full.
+    pub fn is_full(&self) -> bool {
+        false
+    }
+}
+
+impl<T> Drop for Channel<T> {
+    fn drop(&mut self) {
+        let mut head = self.head.index.load(Ordering::Relaxed);
+        let mut tail = self.tail.index.load(Ordering::Relaxed);
+        let mut block = self.head.block.load(Ordering::Relaxed);
+
+        // Erase the lower bits.
+        head &= !((1 << SHIFT) - 1);
+        tail &= !((1 << SHIFT) - 1);
+
+        unsafe {
+            // Drop all messages between head and tail and deallocate the heap-allocated blocks.
+            while head != tail {
+                let offset = (head >> SHIFT) % LAP;
+
+                if offset < BLOCK_CAP {
+                    // Drop the message in the slot.
+                    let slot = (*block).slots.get_unchecked(offset);
+                    let p = &mut *slot.msg.get();
+                    p.as_mut_ptr().drop_in_place();
+                } else {
+                    // Deallocate the block and move to the next one.
+                    let next = (*block).next.load(Ordering::Relaxed);
+                    drop(Box::from_raw(block));
+                    block = next;
+                }
+
+                head = head.wrapping_add(1 << SHIFT);
+            }
+
+            // Deallocate the last remaining block.
+            if !block.is_null() {
+                drop(Box::from_raw(block));
+            }
+        }
+    }
+}
+
+/// Receiver handle to a channel.
+pub struct Receiver<'a, T>(&'a Channel<T>);
+
+/// Sender handle to a channel.
+pub struct Sender<'a, T>(&'a Channel<T>);
+
+impl<T> SelectHandle for Receiver<'_, T> {
+    fn try_select(&self, token: &mut Token) -> bool {
+        self.0.start_recv(token)
+    }
+
+    fn deadline(&self) -> Option<Instant> {
+        None
+    }
+
+    fn register(&self, oper: Operation, cx: &Context) -> bool {
+        self.0.receivers.register(oper, cx);
+        self.is_ready()
+    }
+
+    fn unregister(&self, oper: Operation) {
+        self.0.receivers.unregister(oper);
+    }
+
+    fn accept(&self, token: &mut Token, _cx: &Context) -> bool {
+        self.try_select(token)
+    }
+
+    fn is_ready(&self) -> bool {
+        !self.0.is_empty() || self.0.is_disconnected()
+    }
+
+    fn watch(&self, oper: Operation, cx: &Context) -> bool {
+        self.0.receivers.watch(oper, cx);
+        self.is_ready()
+    }
+
+    fn unwatch(&self, oper: Operation) {
+        self.0.receivers.unwatch(oper);
+    }
+}
+
+impl<T> SelectHandle for Sender<'_, T> {
+    fn try_select(&self, token: &mut Token) -> bool {
+        self.0.start_send(token)
+    }
+
+    fn deadline(&self) -> Option<Instant> {
+        None
+    }
+
+    fn register(&self, _oper: Operation, _cx: &Context) -> bool {
+        self.is_ready()
+    }
+
+    fn unregister(&self, _oper: Operation) {}
+
+    fn accept(&self, token: &mut Token, _cx: &Context) -> bool {
+        self.try_select(token)
+    }
+
+    fn is_ready(&self) -> bool {
+        true
+    }
+
+    fn watch(&self, _oper: Operation, _cx: &Context) -> bool {
+        self.is_ready()
+    }
+
+    fn unwatch(&self, _oper: Operation) {}
+}
diff --git a/src/flavors/mod.rs b/src/flavors/mod.rs
new file mode 100644
index 0000000..299e78f
--- /dev/null
+++ b/src/flavors/mod.rs
@@ -0,0 +1,17 @@
+//! Channel flavors.
+//!
+//! There are six flavors:
+//!
+//! 1. `at` - Channel that delivers a message after a certain amount of time.
+//! 2. `array` - Bounded channel based on a preallocated array.
+//! 3. `list` - Unbounded channel implemented as a linked list.
+//! 4. `never` - Channel that never delivers messages.
+//! 5. `tick` - Channel that delivers messages periodically.
+//! 6. `zero` - Zero-capacity channel.
+
+pub mod array;
+pub mod at;
+pub mod list;
+pub mod never;
+pub mod tick;
+pub mod zero;
diff --git a/src/flavors/never.rs b/src/flavors/never.rs
new file mode 100644
index 0000000..e49d214
--- /dev/null
+++ b/src/flavors/never.rs
@@ -0,0 +1,110 @@
+//! Channel that never delivers messages.
+//!
+//! Messages cannot be sent into this kind of channel.
+
+use std::marker::PhantomData;
+use std::time::Instant;
+
+use crate::context::Context;
+use crate::err::{RecvTimeoutError, TryRecvError};
+use crate::select::{Operation, SelectHandle, Token};
+use crate::utils;
+
+/// This flavor doesn't need a token.
+pub type NeverToken = ();
+
+/// Channel that never delivers messages.
+pub struct Channel<T> {
+    _marker: PhantomData<T>,
+}
+
+impl<T> Channel<T> {
+    /// Creates a channel that never delivers messages.
+    #[inline]
+    pub fn new() -> Self {
+        Channel {
+            _marker: PhantomData,
+        }
+    }
+
+    /// Attempts to receive a message without blocking.
+    #[inline]
+    pub fn try_recv(&self) -> Result<T, TryRecvError> {
+        Err(TryRecvError::Empty)
+    }
+
+    /// Receives a message from the channel.
+    #[inline]
+    pub fn recv(&self, deadline: Option<Instant>) -> Result<T, RecvTimeoutError> {
+        utils::sleep_until(deadline);
+        Err(RecvTimeoutError::Timeout)
+    }
+
+    /// Reads a message from the channel.
+    #[inline]
+    pub unsafe fn read(&self, _token: &mut Token) -> Result<T, ()> {
+        Err(())
+    }
+
+    /// Returns `true` if the channel is empty.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        true
+    }
+
+    /// Returns `true` if the channel is full.
+    #[inline]
+    pub fn is_full(&self) -> bool {
+        true
+    }
+
+    /// Returns the number of messages in the channel.
+    #[inline]
+    pub fn len(&self) -> usize {
+        0
+    }
+
+    /// Returns the capacity of the channel.
+    #[inline]
+    pub fn capacity(&self) -> Option<usize> {
+        Some(0)
+    }
+}
+
+impl<T> SelectHandle for Channel<T> {
+    #[inline]
+    fn try_select(&self, _token: &mut Token) -> bool {
+        false
+    }
+
+    #[inline]
+    fn deadline(&self) -> Option<Instant> {
+        None
+    }
+
+    #[inline]
+    fn register(&self, _oper: Operation, _cx: &Context) -> bool {
+        self.is_ready()
+    }
+
+    #[inline]
+    fn unregister(&self, _oper: Operation) {}
+
+    #[inline]
+    fn accept(&self, token: &mut Token, _cx: &Context) -> bool {
+        self.try_select(token)
+    }
+
+    #[inline]
+    fn is_ready(&self) -> bool {
+        false
+    }
+
+    #[inline]
+    fn watch(&self, _oper: Operation, _cx: &Context) -> bool {
+        self.is_ready()
+    }
+
+    #[inline]
+    fn unwatch(&self, _oper: Operation) {}
+}
diff --git a/src/flavors/tick.rs b/src/flavors/tick.rs
new file mode 100644
index 0000000..e8e7020
--- /dev/null
+++ b/src/flavors/tick.rs
@@ -0,0 +1,167 @@
+//! Channel that delivers messages periodically.
+//!
+//! Messages cannot be sent into this kind of channel; they are materialized on demand.
+
+use std::thread;
+use std::time::{Duration, Instant};
+
+use crossbeam_utils::atomic::AtomicCell;
+
+use crate::context::Context;
+use crate::err::{RecvTimeoutError, TryRecvError};
+use crate::select::{Operation, SelectHandle, Token};
+
+/// Result of a receive operation.
+pub type TickToken = Option<Instant>;
+
+/// Channel that delivers messages periodically.
+pub struct Channel {
+    /// The instant at which the next message will be delivered.
+    delivery_time: AtomicCell<Instant>,
+
+    /// The time interval in which messages get delivered.
+    duration: Duration,
+}
+
+impl Channel {
+    /// Creates a channel that delivers messages periodically.
+    #[inline]
+    pub fn new(dur: Duration) -> Self {
+        Channel {
+            delivery_time: AtomicCell::new(Instant::now() + dur),
+            duration: dur,
+        }
+    }
+
+    /// Attempts to receive a message without blocking.
+    #[inline]
+    pub fn try_recv(&self) -> Result<Instant, TryRecvError> {
+        loop {
+            let now = Instant::now();
+            let delivery_time = self.delivery_time.load();
+
+            if now < delivery_time {
+                return Err(TryRecvError::Empty);
+            }
+
+            if self
+                .delivery_time
+                .compare_exchange(delivery_time, now + self.duration)
+                .is_ok()
+            {
+                return Ok(delivery_time);
+            }
+        }
+    }
+
+    /// Receives a message from the channel.
+    #[inline]
+    pub fn recv(&self, deadline: Option<Instant>) -> Result<Instant, RecvTimeoutError> {
+        loop {
+            let delivery_time = self.delivery_time.load();
+            let now = Instant::now();
+
+            if let Some(d) = deadline {
+                if d < delivery_time {
+                    if now < d {
+                        thread::sleep(d - now);
+                    }
+                    return Err(RecvTimeoutError::Timeout);
+                }
+            }
+
+            if self
+                .delivery_time
+                .compare_exchange(delivery_time, delivery_time.max(now) + self.duration)
+                .is_ok()
+            {
+                if now < delivery_time {
+                    thread::sleep(delivery_time - now);
+                }
+                return Ok(delivery_time);
+            }
+        }
+    }
+
+    /// Reads a message from the channel.
+    #[inline]
+    pub unsafe fn read(&self, token: &mut Token) -> Result<Instant, ()> {
+        token.tick.ok_or(())
+    }
+
+    /// Returns `true` if the channel is empty.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        Instant::now() < self.delivery_time.load()
+    }
+
+    /// Returns `true` if the channel is full.
+    #[inline]
+    pub fn is_full(&self) -> bool {
+        !self.is_empty()
+    }
+
+    /// Returns the number of messages in the channel.
+    #[inline]
+    pub fn len(&self) -> usize {
+        if self.is_empty() {
+            0
+        } else {
+            1
+        }
+    }
+
+    /// Returns the capacity of the channel.
+    #[inline]
+    pub fn capacity(&self) -> Option<usize> {
+        Some(1)
+    }
+}
+
+impl SelectHandle for Channel {
+    #[inline]
+    fn try_select(&self, token: &mut Token) -> bool {
+        match self.try_recv() {
+            Ok(msg) => {
+                token.tick = Some(msg);
+                true
+            }
+            Err(TryRecvError::Disconnected) => {
+                token.tick = None;
+                true
+            }
+            Err(TryRecvError::Empty) => false,
+        }
+    }
+
+    #[inline]
+    fn deadline(&self) -> Option<Instant> {
+        Some(self.delivery_time.load())
+    }
+
+    #[inline]
+    fn register(&self, _oper: Operation, _cx: &Context) -> bool {
+        self.is_ready()
+    }
+
+    #[inline]
+    fn unregister(&self, _oper: Operation) {}
+
+    #[inline]
+    fn accept(&self, token: &mut Token, _cx: &Context) -> bool {
+        self.try_select(token)
+    }
+
+    #[inline]
+    fn is_ready(&self) -> bool {
+        !self.is_empty()
+    }
+
+    #[inline]
+    fn watch(&self, _oper: Operation, _cx: &Context) -> bool {
+        self.is_ready()
+    }
+
+    #[inline]
+    fn unwatch(&self, _oper: Operation) {}
+}
diff --git a/src/flavors/zero.rs b/src/flavors/zero.rs
new file mode 100644
index 0000000..be647b5
--- /dev/null
+++ b/src/flavors/zero.rs
@@ -0,0 +1,466 @@
+//! Zero-capacity channel.
+//!
+//! This kind of channel is also known as *rendezvous* channel.
+
+use std::cell::UnsafeCell;
+use std::marker::PhantomData;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::time::Instant;
+
+use crossbeam_utils::Backoff;
+
+use crate::context::Context;
+use crate::err::{RecvTimeoutError, SendTimeoutError, TryRecvError, TrySendError};
+use crate::select::{Operation, SelectHandle, Selected, Token};
+use crate::utils::Spinlock;
+use crate::waker::Waker;
+
+/// A pointer to a packet.
+pub type ZeroToken = usize;
+
+/// A slot for passing one message from a sender to a receiver.
+struct Packet<T> {
+    /// Equals `true` if the packet is allocated on the stack.
+    on_stack: bool,
+
+    /// Equals `true` once the packet is ready for reading or writing.
+    ready: AtomicBool,
+
+    /// The message.
+    msg: UnsafeCell<Option<T>>,
+}
+
+impl<T> Packet<T> {
+    /// Creates an empty packet on the stack.
+    fn empty_on_stack() -> Packet<T> {
+        Packet {
+            on_stack: true,
+            ready: AtomicBool::new(false),
+            msg: UnsafeCell::new(None),
+        }
+    }
+
+    /// Creates an empty packet on the heap.
+    fn empty_on_heap() -> Box<Packet<T>> {
+        Box::new(Packet {
+            on_stack: false,
+            ready: AtomicBool::new(false),
+            msg: UnsafeCell::new(None),
+        })
+    }
+
+    /// Creates a packet on the stack, containing a message.
+    fn message_on_stack(msg: T) -> Packet<T> {
+        Packet {
+            on_stack: true,
+            ready: AtomicBool::new(false),
+            msg: UnsafeCell::new(Some(msg)),
+        }
+    }
+
+    /// Waits until the packet becomes ready for reading or writing.
+    fn wait_ready(&self) {
+        let backoff = Backoff::new();
+        while !self.ready.load(Ordering::Acquire) {
+            backoff.snooze();
+        }
+    }
+}
+
+/// Inner representation of a zero-capacity channel.
+struct Inner {
+    /// Senders waiting to pair up with a receive operation.
+    senders: Waker,
+
+    /// Receivers waiting to pair up with a send operation.
+    receivers: Waker,
+
+    /// Equals `true` when the channel is disconnected.
+    is_disconnected: bool,
+}
+
+/// Zero-capacity channel.
+pub struct Channel<T> {
+    /// Inner representation of the channel.
+    inner: Spinlock<Inner>,
+
+    /// Indicates that dropping a `Channel<T>` may drop values of type `T`.
+    _marker: PhantomData<T>,
+}
+
+impl<T> Channel<T> {
+    /// Constructs a new zero-capacity channel.
+    pub fn new() -> Self {
+        Channel {
+            inner: Spinlock::new(Inner {
+                senders: Waker::new(),
+                receivers: Waker::new(),
+                is_disconnected: false,
+            }),
+            _marker: PhantomData,
+        }
+    }
+
+    /// Returns a receiver handle to the channel.
+    pub fn receiver(&self) -> Receiver<'_, T> {
+        Receiver(self)
+    }
+
+    /// Returns a sender handle to the channel.
+    pub fn sender(&self) -> Sender<'_, T> {
+        Sender(self)
+    }
+
+    /// Attempts to reserve a slot for sending a message.
+    fn start_send(&self, token: &mut Token) -> bool {
+        let mut inner = self.inner.lock();
+
+        // If there's a waiting receiver, pair up with it.
+        if let Some(operation) = inner.receivers.try_select() {
+            token.zero = operation.packet;
+            true
+        } else if inner.is_disconnected {
+            token.zero = 0;
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Writes a message into the packet.
+    pub unsafe fn write(&self, token: &mut Token, msg: T) -> Result<(), T> {
+        // If there is no packet, the channel is disconnected.
+        if token.zero == 0 {
+            return Err(msg);
+        }
+
+        let packet = &*(token.zero as *const Packet<T>);
+        packet.msg.get().write(Some(msg));
+        packet.ready.store(true, Ordering::Release);
+        Ok(())
+    }
+
+    /// Attempts to pair up with a sender.
+    fn start_recv(&self, token: &mut Token) -> bool {
+        let mut inner = self.inner.lock();
+
+        // If there's a waiting sender, pair up with it.
+        if let Some(operation) = inner.senders.try_select() {
+            token.zero = operation.packet;
+            true
+        } else if inner.is_disconnected {
+            token.zero = 0;
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Reads a message from the packet.
+    pub unsafe fn read(&self, token: &mut Token) -> Result<T, ()> {
+        // If there is no packet, the channel is disconnected.
+        if token.zero == 0 {
+            return Err(());
+        }
+
+        let packet = &*(token.zero as *const Packet<T>);
+
+        if packet.on_stack {
+            // The message has been in the packet from the beginning, so there is no need to wait
+            // for it. However, after reading the message, we need to set `ready` to `true` in
+            // order to signal that the packet can be destroyed.
+            let msg = packet.msg.get().replace(None).unwrap();
+            packet.ready.store(true, Ordering::Release);
+            Ok(msg)
+        } else {
+            // Wait until the message becomes available, then read it and destroy the
+            // heap-allocated packet.
+            packet.wait_ready();
+            let msg = packet.msg.get().replace(None).unwrap();
+            drop(Box::from_raw(packet as *const Packet<T> as *mut Packet<T>));
+            Ok(msg)
+        }
+    }
+
+    /// Attempts to send a message into the channel.
+    pub fn try_send(&self, msg: T) -> Result<(), TrySendError<T>> {
+        let token = &mut Token::default();
+        let mut inner = self.inner.lock();
+
+        // If there's a waiting receiver, pair up with it.
+        if let Some(operation) = inner.receivers.try_select() {
+            token.zero = operation.packet;
+            drop(inner);
+            unsafe {
+                self.write(token, msg).ok().unwrap();
+            }
+            Ok(())
+        } else if inner.is_disconnected {
+            Err(TrySendError::Disconnected(msg))
+        } else {
+            Err(TrySendError::Full(msg))
+        }
+    }
+
+    /// Sends a message into the channel.
+    pub fn send(&self, msg: T, deadline: Option<Instant>) -> Result<(), SendTimeoutError<T>> {
+        let token = &mut Token::default();
+        let mut inner = self.inner.lock();
+
+        // If there's a waiting receiver, pair up with it.
+        if let Some(operation) = inner.receivers.try_select() {
+            token.zero = operation.packet;
+            drop(inner);
+            unsafe {
+                self.write(token, msg).ok().unwrap();
+            }
+            return Ok(());
+        }
+
+        if inner.is_disconnected {
+            return Err(SendTimeoutError::Disconnected(msg));
+        }
+
+        Context::with(|cx| {
+            // Prepare for blocking until a receiver wakes us up.
+            let oper = Operation::hook(token);
+            let packet = Packet::<T>::message_on_stack(msg);
+            inner
+                .senders
+                .register_with_packet(oper, &packet as *const Packet<T> as usize, cx);
+            inner.receivers.notify();
+            drop(inner);
+
+            // Block the current thread.
+            let sel = cx.wait_until(deadline);
+
+            match sel {
+                Selected::Waiting => unreachable!(),
+                Selected::Aborted => {
+                    self.inner.lock().senders.unregister(oper).unwrap();
+                    let msg = unsafe { packet.msg.get().replace(None).unwrap() };
+                    Err(SendTimeoutError::Timeout(msg))
+                }
+                Selected::Disconnected => {
+                    self.inner.lock().senders.unregister(oper).unwrap();
+                    let msg = unsafe { packet.msg.get().replace(None).unwrap() };
+                    Err(SendTimeoutError::Disconnected(msg))
+                }
+                Selected::Operation(_) => {
+                    // Wait until the message is read, then drop the packet.
+                    packet.wait_ready();
+                    Ok(())
+                }
+            }
+        })
+    }
+
+    /// Attempts to receive a message without blocking.
+    pub fn try_recv(&self) -> Result<T, TryRecvError> {
+        let token = &mut Token::default();
+        let mut inner = self.inner.lock();
+
+        // If there's a waiting sender, pair up with it.
+        if let Some(operation) = inner.senders.try_select() {
+            token.zero = operation.packet;
+            drop(inner);
+            unsafe { self.read(token).map_err(|_| TryRecvError::Disconnected) }
+        } else if inner.is_disconnected {
+            Err(TryRecvError::Disconnected)
+        } else {
+            Err(TryRecvError::Empty)
+        }
+    }
+
+    /// Receives a message from the channel.
+    pub fn recv(&self, deadline: Option<Instant>) -> Result<T, RecvTimeoutError> {
+        let token = &mut Token::default();
+        let mut inner = self.inner.lock();
+
+        // If there's a waiting sender, pair up with it.
+        if let Some(operation) = inner.senders.try_select() {
+            token.zero = operation.packet;
+            drop(inner);
+            unsafe {
+                return self.read(token).map_err(|_| RecvTimeoutError::Disconnected);
+            }
+        }
+
+        if inner.is_disconnected {
+            return Err(RecvTimeoutError::Disconnected);
+        }
+
+        Context::with(|cx| {
+            // Prepare for blocking until a sender wakes us up.
+            let oper = Operation::hook(token);
+            let packet = Packet::<T>::empty_on_stack();
+            inner
+                .receivers
+                .register_with_packet(oper, &packet as *const Packet<T> as usize, cx);
+            inner.senders.notify();
+            drop(inner);
+
+            // Block the current thread.
+            let sel = cx.wait_until(deadline);
+
+            match sel {
+                Selected::Waiting => unreachable!(),
+                Selected::Aborted => {
+                    self.inner.lock().receivers.unregister(oper).unwrap();
+                    Err(RecvTimeoutError::Timeout)
+                }
+                Selected::Disconnected => {
+                    self.inner.lock().receivers.unregister(oper).unwrap();
+                    Err(RecvTimeoutError::Disconnected)
+                }
+                Selected::Operation(_) => {
+                    // Wait until the message is provided, then read it.
+                    packet.wait_ready();
+                    unsafe { Ok(packet.msg.get().replace(None).unwrap()) }
+                }
+            }
+        })
+    }
+
+    /// Disconnects the channel and wakes up all blocked senders and receivers.
+    ///
+    /// Returns `true` if this call disconnected the channel.
+    pub fn disconnect(&self) -> bool {
+        let mut inner = self.inner.lock();
+
+        if !inner.is_disconnected {
+            inner.is_disconnected = true;
+            inner.senders.disconnect();
+            inner.receivers.disconnect();
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Returns the current number of messages inside the channel.
+    pub fn len(&self) -> usize {
+        0
+    }
+
+    /// Returns the capacity of the channel.
+    pub fn capacity(&self) -> Option<usize> {
+        Some(0)
+    }
+
+    /// Returns `true` if the channel is empty.
+    pub fn is_empty(&self) -> bool {
+        true
+    }
+
+    /// Returns `true` if the channel is full.
+    pub fn is_full(&self) -> bool {
+        true
+    }
+}
+
+/// Receiver handle to a channel.
+pub struct Receiver<'a, T>(&'a Channel<T>);
+
+/// Sender handle to a channel.
+pub struct Sender<'a, T>(&'a Channel<T>);
+
+impl<T> SelectHandle for Receiver<'_, T> {
+    fn try_select(&self, token: &mut Token) -> bool {
+        self.0.start_recv(token)
+    }
+
+    fn deadline(&self) -> Option<Instant> {
+        None
+    }
+
+    fn register(&self, oper: Operation, cx: &Context) -> bool {
+        let packet = Box::into_raw(Packet::<T>::empty_on_heap());
+
+        let mut inner = self.0.inner.lock();
+        inner
+            .receivers
+            .register_with_packet(oper, packet as usize, cx);
+        inner.senders.notify();
+        inner.senders.can_select() || inner.is_disconnected
+    }
+
+    fn unregister(&self, oper: Operation) {
+        if let Some(operation) = self.0.inner.lock().receivers.unregister(oper) {
+            unsafe {
+                drop(Box::from_raw(operation.packet as *mut Packet<T>));
+            }
+        }
+    }
+
+    fn accept(&self, token: &mut Token, cx: &Context) -> bool {
+        token.zero = cx.wait_packet();
+        true
+    }
+
+    fn is_ready(&self) -> bool {
+        let inner = self.0.inner.lock();
+        inner.senders.can_select() || inner.is_disconnected
+    }
+
+    fn watch(&self, oper: Operation, cx: &Context) -> bool {
+        let mut inner = self.0.inner.lock();
+        inner.receivers.watch(oper, cx);
+        inner.senders.can_select() || inner.is_disconnected
+    }
+
+    fn unwatch(&self, oper: Operation) {
+        let mut inner = self.0.inner.lock();
+        inner.receivers.unwatch(oper);
+    }
+}
+
+impl<T> SelectHandle for Sender<'_, T> {
+    fn try_select(&self, token: &mut Token) -> bool {
+        self.0.start_send(token)
+    }
+
+    fn deadline(&self) -> Option<Instant> {
+        None
+    }
+
+    fn register(&self, oper: Operation, cx: &Context) -> bool {
+        let packet = Box::into_raw(Packet::<T>::empty_on_heap());
+
+        let mut inner = self.0.inner.lock();
+        inner
+            .senders
+            .register_with_packet(oper, packet as usize, cx);
+        inner.receivers.notify();
+        inner.receivers.can_select() || inner.is_disconnected
+    }
+
+    fn unregister(&self, oper: Operation) {
+        if let Some(operation) = self.0.inner.lock().senders.unregister(oper) {
+            unsafe {
+                drop(Box::from_raw(operation.packet as *mut Packet<T>));
+            }
+        }
+    }
+
+    fn accept(&self, token: &mut Token, cx: &Context) -> bool {
+        token.zero = cx.wait_packet();
+        true
+    }
+
+    fn is_ready(&self) -> bool {
+        let inner = self.0.inner.lock();
+        inner.receivers.can_select() || inner.is_disconnected
+    }
+
+    fn watch(&self, oper: Operation, cx: &Context) -> bool {
+        let mut inner = self.0.inner.lock();
+        inner.senders.watch(oper, cx);
+        inner.receivers.can_select() || inner.is_disconnected
+    }
+
+    fn unwatch(&self, oper: Operation) {
+        let mut inner = self.0.inner.lock();
+        inner.senders.unwatch(oper);
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..e08ac08
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,368 @@
+//! Multi-producer multi-consumer channels for message passing.
+//!
+//! This crate is an alternative to [`std::sync::mpsc`] with more features and better performance.
+//!
+//! # Hello, world!
+//!
+//! ```
+//! use crossbeam_channel::unbounded;
+//!
+//! // Create a channel of unbounded capacity.
+//! let (s, r) = unbounded();
+//!
+//! // Send a message into the channel.
+//! s.send("Hello, world!").unwrap();
+//!
+//! // Receive the message from the channel.
+//! assert_eq!(r.recv(), Ok("Hello, world!"));
+//! ```
+//!
+//! # Channel types
+//!
+//! Channels can be created using two functions:
+//!
+//! * [`bounded`] creates a channel of bounded capacity, i.e. there is a limit to how many messages
+//!   it can hold at a time.
+//!
+//! * [`unbounded`] creates a channel of unbounded capacity, i.e. it can hold any number of
+//!   messages at a time.
+//!
+//! Both functions return a [`Sender`] and a [`Receiver`], which represent the two opposite sides
+//! of a channel.
+//!
+//! Creating a bounded channel:
+//!
+//! ```
+//! use crossbeam_channel::bounded;
+//!
+//! // Create a channel that can hold at most 5 messages at a time.
+//! let (s, r) = bounded(5);
+//!
+//! // Can send only 5 messages without blocking.
+//! for i in 0..5 {
+//!     s.send(i).unwrap();
+//! }
+//!
+//! // Another call to `send` would block because the channel is full.
+//! // s.send(5).unwrap();
+//! ```
+//!
+//! Creating an unbounded channel:
+//!
+//! ```
+//! use crossbeam_channel::unbounded;
+//!
+//! // Create an unbounded channel.
+//! let (s, r) = unbounded();
+//!
+//! // Can send any number of messages into the channel without blocking.
+//! for i in 0..1000 {
+//!     s.send(i).unwrap();
+//! }
+//! ```
+//!
+//! A special case is zero-capacity channel, which cannot hold any messages. Instead, send and
+//! receive operations must appear at the same time in order to pair up and pass the message over:
+//!
+//! ```
+//! use std::thread;
+//! use crossbeam_channel::bounded;
+//!
+//! // Create a zero-capacity channel.
+//! let (s, r) = bounded(0);
+//!
+//! // Sending blocks until a receive operation appears on the other side.
+//! thread::spawn(move || s.send("Hi!").unwrap());
+//!
+//! // Receiving blocks until a send operation appears on the other side.
+//! assert_eq!(r.recv(), Ok("Hi!"));
+//! ```
+//!
+//! # Sharing channels
+//!
+//! Senders and receivers can be cloned and sent to other threads:
+//!
+//! ```
+//! use std::thread;
+//! use crossbeam_channel::bounded;
+//!
+//! let (s1, r1) = bounded(0);
+//! let (s2, r2) = (s1.clone(), r1.clone());
+//!
+//! // Spawn a thread that receives a message and then sends one.
+//! thread::spawn(move || {
+//!     r2.recv().unwrap();
+//!     s2.send(2).unwrap();
+//! });
+//!
+//! // Send a message and then receive one.
+//! s1.send(1).unwrap();
+//! r1.recv().unwrap();
+//! ```
+//!
+//! Note that cloning only creates a new handle to the same sending or receiving side. It does not
+//! create a separate stream of messages in any way:
+//!
+//! ```
+//! use crossbeam_channel::unbounded;
+//!
+//! let (s1, r1) = unbounded();
+//! let (s2, r2) = (s1.clone(), r1.clone());
+//! let (s3, r3) = (s2.clone(), r2.clone());
+//!
+//! s1.send(10).unwrap();
+//! s2.send(20).unwrap();
+//! s3.send(30).unwrap();
+//!
+//! assert_eq!(r3.recv(), Ok(10));
+//! assert_eq!(r1.recv(), Ok(20));
+//! assert_eq!(r2.recv(), Ok(30));
+//! ```
+//!
+//! It's also possible to share senders and receivers by reference:
+//!
+//! ```
+//! use crossbeam_channel::bounded;
+//! use crossbeam_utils::thread::scope;
+//!
+//! let (s, r) = bounded(0);
+//!
+//! scope(|scope| {
+//!     // Spawn a thread that receives a message and then sends one.
+//!     scope.spawn(|_| {
+//!         r.recv().unwrap();
+//!         s.send(2).unwrap();
+//!     });
+//!
+//!     // Send a message and then receive one.
+//!     s.send(1).unwrap();
+//!     r.recv().unwrap();
+//! }).unwrap();
+//! ```
+//!
+//! # Disconnection
+//!
+//! When all senders or all receivers associated with a channel get dropped, the channel becomes
+//! disconnected. No more messages can be sent, but any remaining messages can still be received.
+//! Send and receive operations on a disconnected channel never block.
+//!
+//! ```
+//! use crossbeam_channel::{unbounded, RecvError};
+//!
+//! let (s, r) = unbounded();
+//! s.send(1).unwrap();
+//! s.send(2).unwrap();
+//! s.send(3).unwrap();
+//!
+//! // The only sender is dropped, disconnecting the channel.
+//! drop(s);
+//!
+//! // The remaining messages can be received.
+//! assert_eq!(r.recv(), Ok(1));
+//! assert_eq!(r.recv(), Ok(2));
+//! assert_eq!(r.recv(), Ok(3));
+//!
+//! // There are no more messages in the channel.
+//! assert!(r.is_empty());
+//!
+//! // Note that calling `r.recv()` does not block.
+//! // Instead, `Err(RecvError)` is returned immediately.
+//! assert_eq!(r.recv(), Err(RecvError));
+//! ```
+//!
+//! # Blocking operations
+//!
+//! Send and receive operations come in three flavors:
+//!
+//! * Non-blocking (returns immediately with success or failure).
+//! * Blocking (waits until the operation succeeds or the channel becomes disconnected).
+//! * Blocking with a timeout (blocks only for a certain duration of time).
+//!
+//! A simple example showing the difference between non-blocking and blocking operations:
+//!
+//! ```
+//! use crossbeam_channel::{bounded, RecvError, TryRecvError};
+//!
+//! let (s, r) = bounded(1);
+//!
+//! // Send a message into the channel.
+//! s.send("foo").unwrap();
+//!
+//! // This call would block because the channel is full.
+//! // s.send("bar").unwrap();
+//!
+//! // Receive the message.
+//! assert_eq!(r.recv(), Ok("foo"));
+//!
+//! // This call would block because the channel is empty.
+//! // r.recv();
+//!
+//! // Try receiving a message without blocking.
+//! assert_eq!(r.try_recv(), Err(TryRecvError::Empty));
+//!
+//! // Disconnect the channel.
+//! drop(s);
+//!
+//! // This call doesn't block because the channel is now disconnected.
+//! assert_eq!(r.recv(), Err(RecvError));
+//! ```
+//!
+//! # Iteration
+//!
+//! Receivers can be used as iterators. For example, method [`iter`] creates an iterator that
+//! receives messages until the channel becomes empty and disconnected. Note that iteration may
+//! block waiting for next message to arrive.
+//!
+//! ```
+//! use std::thread;
+//! use crossbeam_channel::unbounded;
+//!
+//! let (s, r) = unbounded();
+//!
+//! thread::spawn(move || {
+//!     s.send(1).unwrap();
+//!     s.send(2).unwrap();
+//!     s.send(3).unwrap();
+//!     drop(s); // Disconnect the channel.
+//! });
+//!
+//! // Collect all messages from the channel.
+//! // Note that the call to `collect` blocks until the sender is dropped.
+//! let v: Vec<_> = r.iter().collect();
+//!
+//! assert_eq!(v, [1, 2, 3]);
+//! ```
+//!
+//! A non-blocking iterator can be created using [`try_iter`], which receives all available
+//! messages without blocking:
+//!
+//! ```
+//! use crossbeam_channel::unbounded;
+//!
+//! let (s, r) = unbounded();
+//! s.send(1).unwrap();
+//! s.send(2).unwrap();
+//! s.send(3).unwrap();
+//! // No need to drop the sender.
+//!
+//! // Receive all messages currently in the channel.
+//! let v: Vec<_> = r.try_iter().collect();
+//!
+//! assert_eq!(v, [1, 2, 3]);
+//! ```
+//!
+//! # Selection
+//!
+//! The [`select!`] macro allows you to define a set of channel operations, wait until any one of
+//! them becomes ready, and finally execute it. If multiple operations are ready at the same time,
+//! a random one among them is selected.
+//!
+//! It is also possible to define a `default` case that gets executed if none of the operations are
+//! ready, either right away or for a certain duration of time.
+//!
+//! An operation is considered to be ready if it doesn't have to block. Note that it is ready even
+//! when it will simply return an error because the channel is disconnected.
+//!
+//! An example of receiving a message from two channels:
+//!
+//! ```
+//! use std::thread;
+//! use std::time::Duration;
+//! use crossbeam_channel::{select, unbounded};
+//!
+//! let (s1, r1) = unbounded();
+//! let (s2, r2) = unbounded();
+//!
+//! thread::spawn(move || s1.send(10).unwrap());
+//! thread::spawn(move || s2.send(20).unwrap());
+//!
+//! // At most one of these two receive operations will be executed.
+//! select! {
+//!     recv(r1) -> msg => assert_eq!(msg, Ok(10)),
+//!     recv(r2) -> msg => assert_eq!(msg, Ok(20)),
+//!     default(Duration::from_secs(1)) => println!("timed out"),
+//! }
+//! ```
+//!
+//! If you need to select over a dynamically created list of channel operations, use [`Select`]
+//! instead. The [`select!`] macro is just a convenience wrapper around [`Select`].
+//!
+//! # Extra channels
+//!
+//! Three functions can create special kinds of channels, all of which return just a [`Receiver`]
+//! handle:
+//!
+//! * [`after`] creates a channel that delivers a single message after a certain duration of time.
+//! * [`tick`] creates a channel that delivers messages periodically.
+//! * [`never`] creates a channel that never delivers messages.
+//!
+//! These channels are very efficient because messages get lazily generated on receive operations.
+//!
+//! An example that prints elapsed time every 50 milliseconds for the duration of 1 second:
+//!
+//! ```
+//! use std::time::{Duration, Instant};
+//! use crossbeam_channel::{after, select, tick};
+//!
+//! let start = Instant::now();
+//! let ticker = tick(Duration::from_millis(50));
+//! let timeout = after(Duration::from_secs(1));
+//!
+//! loop {
+//!     select! {
+//!         recv(ticker) -> _ => println!("elapsed: {:?}", start.elapsed()),
+//!         recv(timeout) -> _ => break,
+//!     }
+//! }
+//! ```
+//!
+//! [`send`]: Sender::send
+//! [`recv`]: Receiver::recv
+//! [`iter`]: Receiver::iter
+//! [`try_iter`]: Receiver::try_iter
+
+#![doc(test(
+    no_crate_inject,
+    attr(
+        deny(warnings, rust_2018_idioms),
+        allow(dead_code, unused_assignments, unused_variables)
+    )
+))]
+#![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
+#![cfg_attr(not(feature = "std"), no_std)]
+// matches! requires Rust 1.42
+#![allow(clippy::match_like_matches_macro)]
+
+use cfg_if::cfg_if;
+
+cfg_if! {
+    if #[cfg(feature = "std")] {
+        mod channel;
+        mod context;
+        mod counter;
+        mod err;
+        mod flavors;
+        mod select;
+        mod select_macro;
+        mod utils;
+        mod waker;
+
+        /// Crate internals used by the `select!` macro.
+        #[doc(hidden)]
+        pub mod internal {
+            pub use crate::select::SelectHandle;
+            pub use crate::select::{select, select_timeout, try_select};
+        }
+
+        pub use crate::channel::{after, at, never, tick};
+        pub use crate::channel::{bounded, unbounded};
+        pub use crate::channel::{IntoIter, Iter, TryIter};
+        pub use crate::channel::{Receiver, Sender};
+
+        pub use crate::select::{Select, SelectedOperation};
+
+        pub use crate::err::{ReadyTimeoutError, SelectTimeoutError, TryReadyError, TrySelectError};
+        pub use crate::err::{RecvError, RecvTimeoutError, TryRecvError};
+        pub use crate::err::{SendError, SendTimeoutError, TrySendError};
+    }
+}
diff --git a/src/select.rs b/src/select.rs
new file mode 100644
index 0000000..1488f80
--- /dev/null
+++ b/src/select.rs
@@ -0,0 +1,1251 @@
+//! Interface to the select mechanism.
+
+use std::fmt;
+use std::marker::PhantomData;
+use std::mem;
+use std::time::{Duration, Instant};
+
+use crossbeam_utils::Backoff;
+
+use crate::channel::{self, Receiver, Sender};
+use crate::context::Context;
+use crate::err::{ReadyTimeoutError, TryReadyError};
+use crate::err::{RecvError, SendError};
+use crate::err::{SelectTimeoutError, TrySelectError};
+use crate::flavors;
+use crate::utils;
+
+/// Temporary data that gets initialized during select or a blocking operation, and is consumed by
+/// `read` or `write`.
+///
+/// Each field contains data associated with a specific channel flavor.
+#[derive(Debug, Default)]
+pub struct Token {
+    pub at: flavors::at::AtToken,
+    pub array: flavors::array::ArrayToken,
+    pub list: flavors::list::ListToken,
+    pub never: flavors::never::NeverToken,
+    pub tick: flavors::tick::TickToken,
+    pub zero: flavors::zero::ZeroToken,
+}
+
+/// Identifier associated with an operation by a specific thread on a specific channel.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct Operation(usize);
+
+impl Operation {
+    /// Creates an operation identifier from a mutable reference.
+    ///
+    /// This function essentially just turns the address of the reference into a number. The
+    /// reference should point to a variable that is specific to the thread and the operation,
+    /// and is alive for the entire duration of select or blocking operation.
+    #[inline]
+    pub fn hook<T>(r: &mut T) -> Operation {
+        let val = r as *mut T as usize;
+        // Make sure that the pointer address doesn't equal the numerical representation of
+        // `Selected::{Waiting, Aborted, Disconnected}`.
+        assert!(val > 2);
+        Operation(val)
+    }
+}
+
+/// Current state of a select or a blocking operation.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Selected {
+    /// Still waiting for an operation.
+    Waiting,
+
+    /// The attempt to block the current thread has been aborted.
+    Aborted,
+
+    /// An operation became ready because a channel is disconnected.
+    Disconnected,
+
+    /// An operation became ready because a message can be sent or received.
+    Operation(Operation),
+}
+
+impl From<usize> for Selected {
+    #[inline]
+    fn from(val: usize) -> Selected {
+        match val {
+            0 => Selected::Waiting,
+            1 => Selected::Aborted,
+            2 => Selected::Disconnected,
+            oper => Selected::Operation(Operation(oper)),
+        }
+    }
+}
+
+impl Into<usize> for Selected {
+    #[inline]
+    fn into(self) -> usize {
+        match self {
+            Selected::Waiting => 0,
+            Selected::Aborted => 1,
+            Selected::Disconnected => 2,
+            Selected::Operation(Operation(val)) => val,
+        }
+    }
+}
+
+/// A receiver or a sender that can participate in select.
+///
+/// This is a handle that assists select in executing an operation, registration, deciding on the
+/// appropriate deadline for blocking, etc.
+pub trait SelectHandle {
+    /// Attempts to select an operation and returns `true` on success.
+    fn try_select(&self, token: &mut Token) -> bool;
+
+    /// Returns a deadline for an operation, if there is one.
+    fn deadline(&self) -> Option<Instant>;
+
+    /// Registers an operation for execution and returns `true` if it is now ready.
+    fn register(&self, oper: Operation, cx: &Context) -> bool;
+
+    /// Unregisters an operation for execution.
+    fn unregister(&self, oper: Operation);
+
+    /// Attempts to select an operation the thread got woken up for and returns `true` on success.
+    fn accept(&self, token: &mut Token, cx: &Context) -> bool;
+
+    /// Returns `true` if an operation can be executed without blocking.
+    fn is_ready(&self) -> bool;
+
+    /// Registers an operation for readiness notification and returns `true` if it is now ready.
+    fn watch(&self, oper: Operation, cx: &Context) -> bool;
+
+    /// Unregisters an operation for readiness notification.
+    fn unwatch(&self, oper: Operation);
+}
+
+impl<T: SelectHandle> SelectHandle for &T {
+    fn try_select(&self, token: &mut Token) -> bool {
+        (**self).try_select(token)
+    }
+
+    fn deadline(&self) -> Option<Instant> {
+        (**self).deadline()
+    }
+
+    fn register(&self, oper: Operation, cx: &Context) -> bool {
+        (**self).register(oper, cx)
+    }
+
+    fn unregister(&self, oper: Operation) {
+        (**self).unregister(oper);
+    }
+
+    fn accept(&self, token: &mut Token, cx: &Context) -> bool {
+        (**self).accept(token, cx)
+    }
+
+    fn is_ready(&self) -> bool {
+        (**self).is_ready()
+    }
+
+    fn watch(&self, oper: Operation, cx: &Context) -> bool {
+        (**self).watch(oper, cx)
+    }
+
+    fn unwatch(&self, oper: Operation) {
+        (**self).unwatch(oper)
+    }
+}
+
+/// Determines when a select operation should time out.
+#[derive(Clone, Copy, Eq, PartialEq)]
+enum Timeout {
+    /// No blocking.
+    Now,
+
+    /// Block forever.
+    Never,
+
+    /// Time out after the time instant.
+    At(Instant),
+}
+
+/// Runs until one of the operations is selected, potentially blocking the current thread.
+///
+/// Successful receive operations will have to be followed up by `channel::read()` and successful
+/// send operations by `channel::write()`.
+fn run_select(
+    handles: &mut [(&dyn SelectHandle, usize, *const u8)],
+    timeout: Timeout,
+) -> Option<(Token, usize, *const u8)> {
+    if handles.is_empty() {
+        // Wait until the timeout and return.
+        match timeout {
+            Timeout::Now => return None,
+            Timeout::Never => {
+                utils::sleep_until(None);
+                unreachable!();
+            }
+            Timeout::At(when) => {
+                utils::sleep_until(Some(when));
+                return None;
+            }
+        }
+    }
+
+    // Shuffle the operations for fairness.
+    utils::shuffle(handles);
+
+    // Create a token, which serves as a temporary variable that gets initialized in this function
+    // and is later used by a call to `channel::read()` or `channel::write()` that completes the
+    // selected operation.
+    let mut token = Token::default();
+
+    // Try selecting one of the operations without blocking.
+    for &(handle, i, ptr) in handles.iter() {
+        if handle.try_select(&mut token) {
+            return Some((token, i, ptr));
+        }
+    }
+
+    loop {
+        // Prepare for blocking.
+        let res = Context::with(|cx| {
+            let mut sel = Selected::Waiting;
+            let mut registered_count = 0;
+            let mut index_ready = None;
+
+            if let Timeout::Now = timeout {
+                cx.try_select(Selected::Aborted).unwrap();
+            }
+
+            // Register all operations.
+            for (handle, i, _) in handles.iter_mut() {
+                registered_count += 1;
+
+                // If registration returns `false`, that means the operation has just become ready.
+                if handle.register(Operation::hook::<&dyn SelectHandle>(handle), cx) {
+                    // Try aborting select.
+                    sel = match cx.try_select(Selected::Aborted) {
+                        Ok(()) => {
+                            index_ready = Some(*i);
+                            Selected::Aborted
+                        }
+                        Err(s) => s,
+                    };
+                    break;
+                }
+
+                // If another thread has already selected one of the operations, stop registration.
+                sel = cx.selected();
+                if sel != Selected::Waiting {
+                    break;
+                }
+            }
+
+            if sel == Selected::Waiting {
+                // Check with each operation for how long we're allowed to block, and compute the
+                // earliest deadline.
+                let mut deadline: Option<Instant> = match timeout {
+                    Timeout::Now => return None,
+                    Timeout::Never => None,
+                    Timeout::At(when) => Some(when),
+                };
+                for &(handle, _, _) in handles.iter() {
+                    if let Some(x) = handle.deadline() {
+                        deadline = deadline.map(|y| x.min(y)).or(Some(x));
+                    }
+                }
+
+                // Block the current thread.
+                sel = cx.wait_until(deadline);
+            }
+
+            // Unregister all registered operations.
+            for (handle, _, _) in handles.iter_mut().take(registered_count) {
+                handle.unregister(Operation::hook::<&dyn SelectHandle>(handle));
+            }
+
+            match sel {
+                Selected::Waiting => unreachable!(),
+                Selected::Aborted => {
+                    // If an operation became ready during registration, try selecting it.
+                    if let Some(index_ready) = index_ready {
+                        for &(handle, i, ptr) in handles.iter() {
+                            if i == index_ready && handle.try_select(&mut token) {
+                                return Some((i, ptr));
+                            }
+                        }
+                    }
+                }
+                Selected::Disconnected => {}
+                Selected::Operation(_) => {
+                    // Find the selected operation.
+                    for (handle, i, ptr) in handles.iter_mut() {
+                        // Is this the selected operation?
+                        if sel == Selected::Operation(Operation::hook::<&dyn SelectHandle>(handle))
+                        {
+                            // Try selecting this operation.
+                            if handle.accept(&mut token, cx) {
+                                return Some((*i, *ptr));
+                            }
+                        }
+                    }
+                }
+            }
+
+            None
+        });
+
+        // Return if an operation was selected.
+        if let Some((i, ptr)) = res {
+            return Some((token, i, ptr));
+        }
+
+        // Try selecting one of the operations without blocking.
+        for &(handle, i, ptr) in handles.iter() {
+            if handle.try_select(&mut token) {
+                return Some((token, i, ptr));
+            }
+        }
+
+        match timeout {
+            Timeout::Now => return None,
+            Timeout::Never => {}
+            Timeout::At(when) => {
+                if Instant::now() >= when {
+                    return None;
+                }
+            }
+        }
+    }
+}
+
+/// Runs until one of the operations becomes ready, potentially blocking the current thread.
+fn run_ready(
+    handles: &mut [(&dyn SelectHandle, usize, *const u8)],
+    timeout: Timeout,
+) -> Option<usize> {
+    if handles.is_empty() {
+        // Wait until the timeout and return.
+        match timeout {
+            Timeout::Now => return None,
+            Timeout::Never => {
+                utils::sleep_until(None);
+                unreachable!();
+            }
+            Timeout::At(when) => {
+                utils::sleep_until(Some(when));
+                return None;
+            }
+        }
+    }
+
+    // Shuffle the operations for fairness.
+    utils::shuffle(handles);
+
+    loop {
+        let backoff = Backoff::new();
+        loop {
+            // Check operations for readiness.
+            for &(handle, i, _) in handles.iter() {
+                if handle.is_ready() {
+                    return Some(i);
+                }
+            }
+
+            if backoff.is_completed() {
+                break;
+            } else {
+                backoff.snooze();
+            }
+        }
+
+        // Check for timeout.
+        match timeout {
+            Timeout::Now => return None,
+            Timeout::Never => {}
+            Timeout::At(when) => {
+                if Instant::now() >= when {
+                    return None;
+                }
+            }
+        }
+
+        // Prepare for blocking.
+        let res = Context::with(|cx| {
+            let mut sel = Selected::Waiting;
+            let mut registered_count = 0;
+
+            // Begin watching all operations.
+            for (handle, _, _) in handles.iter_mut() {
+                registered_count += 1;
+                let oper = Operation::hook::<&dyn SelectHandle>(handle);
+
+                // If registration returns `false`, that means the operation has just become ready.
+                if handle.watch(oper, cx) {
+                    sel = match cx.try_select(Selected::Operation(oper)) {
+                        Ok(()) => Selected::Operation(oper),
+                        Err(s) => s,
+                    };
+                    break;
+                }
+
+                // If another thread has already chosen one of the operations, stop registration.
+                sel = cx.selected();
+                if sel != Selected::Waiting {
+                    break;
+                }
+            }
+
+            if sel == Selected::Waiting {
+                // Check with each operation for how long we're allowed to block, and compute the
+                // earliest deadline.
+                let mut deadline: Option<Instant> = match timeout {
+                    Timeout::Now => unreachable!(),
+                    Timeout::Never => None,
+                    Timeout::At(when) => Some(when),
+                };
+                for &(handle, _, _) in handles.iter() {
+                    if let Some(x) = handle.deadline() {
+                        deadline = deadline.map(|y| x.min(y)).or(Some(x));
+                    }
+                }
+
+                // Block the current thread.
+                sel = cx.wait_until(deadline);
+            }
+
+            // Unwatch all operations.
+            for (handle, _, _) in handles.iter_mut().take(registered_count) {
+                handle.unwatch(Operation::hook::<&dyn SelectHandle>(handle));
+            }
+
+            match sel {
+                Selected::Waiting => unreachable!(),
+                Selected::Aborted => {}
+                Selected::Disconnected => {}
+                Selected::Operation(_) => {
+                    for (handle, i, _) in handles.iter_mut() {
+                        let oper = Operation::hook::<&dyn SelectHandle>(handle);
+                        if sel == Selected::Operation(oper) {
+                            return Some(*i);
+                        }
+                    }
+                }
+            }
+
+            None
+        });
+
+        // Return if an operation became ready.
+        if res.is_some() {
+            return res;
+        }
+    }
+}
+
+/// Attempts to select one of the operations without blocking.
+#[inline]
+pub fn try_select<'a>(
+    handles: &mut [(&'a dyn SelectHandle, usize, *const u8)],
+) -> Result<SelectedOperation<'a>, TrySelectError> {
+    match run_select(handles, Timeout::Now) {
+        None => Err(TrySelectError),
+        Some((token, index, ptr)) => Ok(SelectedOperation {
+            token,
+            index,
+            ptr,
+            _marker: PhantomData,
+        }),
+    }
+}
+
+/// Blocks until one of the operations becomes ready and selects it.
+#[inline]
+pub fn select<'a>(
+    handles: &mut [(&'a dyn SelectHandle, usize, *const u8)],
+) -> SelectedOperation<'a> {
+    if handles.is_empty() {
+        panic!("no operations have been added to `Select`");
+    }
+
+    let (token, index, ptr) = run_select(handles, Timeout::Never).unwrap();
+    SelectedOperation {
+        token,
+        index,
+        ptr,
+        _marker: PhantomData,
+    }
+}
+
+/// Blocks for a limited time until one of the operations becomes ready and selects it.
+#[inline]
+pub fn select_timeout<'a>(
+    handles: &mut [(&'a dyn SelectHandle, usize, *const u8)],
+    timeout: Duration,
+) -> Result<SelectedOperation<'a>, SelectTimeoutError> {
+    select_deadline(handles, Instant::now() + timeout)
+}
+
+/// Blocks until a given deadline, or until one of the operations becomes ready and selects it.
+#[inline]
+pub fn select_deadline<'a>(
+    handles: &mut [(&'a dyn SelectHandle, usize, *const u8)],
+    deadline: Instant,
+) -> Result<SelectedOperation<'a>, SelectTimeoutError> {
+    match run_select(handles, Timeout::At(deadline)) {
+        None => Err(SelectTimeoutError),
+        Some((token, index, ptr)) => Ok(SelectedOperation {
+            token,
+            index,
+            ptr,
+            _marker: PhantomData,
+        }),
+    }
+}
+
+/// Selects from a set of channel operations.
+///
+/// `Select` allows you to define a set of channel operations, wait until any one of them becomes
+/// ready, and finally execute it. If multiple operations are ready at the same time, a random one
+/// among them is selected.
+///
+/// An operation is considered to be ready if it doesn't have to block. Note that it is ready even
+/// when it will simply return an error because the channel is disconnected.
+///
+/// The [`select!`] macro is a convenience wrapper around `Select`. However, it cannot select over a
+/// dynamically created list of channel operations.
+///
+/// Once a list of operations has been built with `Select`, there are two different ways of
+/// proceeding:
+///
+/// * Select an operation with [`try_select`], [`select`], or [`select_timeout`]. If successful,
+///   the returned selected operation has already begun and **must** be completed. If we don't
+///   complete it, a panic will occur.
+///
+/// * Wait for an operation to become ready with [`try_ready`], [`ready`], or [`ready_timeout`]. If
+///   successful, we may attempt to execute the operation, but are not obliged to. In fact, it's
+///   possible for another thread to make the operation not ready just before we try executing it,
+///   so it's wise to use a retry loop. However, note that these methods might return with success
+///   spuriously, so it's a good idea to always double check if the operation is really ready.
+///
+/// # Examples
+///
+/// Use [`select`] to receive a message from a list of receivers:
+///
+/// ```
+/// use crossbeam_channel::{Receiver, RecvError, Select};
+///
+/// fn recv_multiple<T>(rs: &[Receiver<T>]) -> Result<T, RecvError> {
+///     // Build a list of operations.
+///     let mut sel = Select::new();
+///     for r in rs {
+///         sel.recv(r);
+///     }
+///
+///     // Complete the selected operation.
+///     let oper = sel.select();
+///     let index = oper.index();
+///     oper.recv(&rs[index])
+/// }
+/// ```
+///
+/// Use [`ready`] to receive a message from a list of receivers:
+///
+/// ```
+/// use crossbeam_channel::{Receiver, RecvError, Select};
+///
+/// fn recv_multiple<T>(rs: &[Receiver<T>]) -> Result<T, RecvError> {
+///     // Build a list of operations.
+///     let mut sel = Select::new();
+///     for r in rs {
+///         sel.recv(r);
+///     }
+///
+///     loop {
+///         // Wait until a receive operation becomes ready and try executing it.
+///         let index = sel.ready();
+///         let res = rs[index].try_recv();
+///
+///         // If the operation turns out not to be ready, retry.
+///         if let Err(e) = res {
+///             if e.is_empty() {
+///                 continue;
+///             }
+///         }
+///
+///         // Success!
+///         return res.map_err(|_| RecvError);
+///     }
+/// }
+/// ```
+///
+/// [`try_select`]: Select::try_select
+/// [`select`]: Select::select
+/// [`select_timeout`]: Select::select_timeout
+/// [`try_ready`]: Select::try_ready
+/// [`ready`]: Select::ready
+/// [`ready_timeout`]: Select::ready_timeout
+pub struct Select<'a> {
+    /// A list of senders and receivers participating in selection.
+    handles: Vec<(&'a dyn SelectHandle, usize, *const u8)>,
+
+    /// The next index to assign to an operation.
+    next_index: usize,
+}
+
+unsafe impl Send for Select<'_> {}
+unsafe impl Sync for Select<'_> {}
+
+impl<'a> Select<'a> {
+    /// Creates an empty list of channel operations for selection.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::Select;
+    ///
+    /// let mut sel = Select::new();
+    ///
+    /// // The list of operations is empty, which means no operation can be selected.
+    /// assert!(sel.try_select().is_err());
+    /// ```
+    pub fn new() -> Select<'a> {
+        Select {
+            handles: Vec::with_capacity(4),
+            next_index: 0,
+        }
+    }
+
+    /// Adds a send operation.
+    ///
+    /// Returns the index of the added operation.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let (s, r) = unbounded::<i32>();
+    ///
+    /// let mut sel = Select::new();
+    /// let index = sel.send(&s);
+    /// ```
+    pub fn send<T>(&mut self, s: &'a Sender<T>) -> usize {
+        let i = self.next_index;
+        let ptr = s as *const Sender<_> as *const u8;
+        self.handles.push((s, i, ptr));
+        self.next_index += 1;
+        i
+    }
+
+    /// Adds a receive operation.
+    ///
+    /// Returns the index of the added operation.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let (s, r) = unbounded::<i32>();
+    ///
+    /// let mut sel = Select::new();
+    /// let index = sel.recv(&r);
+    /// ```
+    pub fn recv<T>(&mut self, r: &'a Receiver<T>) -> usize {
+        let i = self.next_index;
+        let ptr = r as *const Receiver<_> as *const u8;
+        self.handles.push((r, i, ptr));
+        self.next_index += 1;
+        i
+    }
+
+    /// Removes a previously added operation.
+    ///
+    /// This is useful when an operation is selected because the channel got disconnected and we
+    /// want to try again to select a different operation instead.
+    ///
+    /// If new operations are added after removing some, the indices of removed operations will not
+    /// be reused.
+    ///
+    /// # Panics
+    ///
+    /// An attempt to remove a non-existing or already removed operation will panic.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let (s1, r1) = unbounded::<i32>();
+    /// let (_, r2) = unbounded::<i32>();
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.recv(&r1);
+    /// let oper2 = sel.recv(&r2);
+    ///
+    /// // Both operations are initially ready, so a random one will be executed.
+    /// let oper = sel.select();
+    /// assert_eq!(oper.index(), oper2);
+    /// assert!(oper.recv(&r2).is_err());
+    /// sel.remove(oper2);
+    ///
+    /// s1.send(10).unwrap();
+    ///
+    /// let oper = sel.select();
+    /// assert_eq!(oper.index(), oper1);
+    /// assert_eq!(oper.recv(&r1), Ok(10));
+    /// ```
+    pub fn remove(&mut self, index: usize) {
+        assert!(
+            index < self.next_index,
+            "index out of bounds; {} >= {}",
+            index,
+            self.next_index,
+        );
+
+        let i = self
+            .handles
+            .iter()
+            .enumerate()
+            .find(|(_, (_, i, _))| *i == index)
+            .expect("no operation with this index")
+            .0;
+
+        self.handles.swap_remove(i);
+    }
+
+    /// Attempts to select one of the operations without blocking.
+    ///
+    /// If an operation is ready, it is selected and returned. If multiple operations are ready at
+    /// the same time, a random one among them is selected. If none of the operations are ready, an
+    /// error is returned.
+    ///
+    /// An operation is considered to be ready if it doesn't have to block. Note that it is ready
+    /// even when it will simply return an error because the channel is disconnected.
+    ///
+    /// The selected operation must be completed with [`SelectedOperation::send`]
+    /// or [`SelectedOperation::recv`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let (s1, r1) = unbounded();
+    /// let (s2, r2) = unbounded();
+    ///
+    /// s1.send(10).unwrap();
+    /// s2.send(20).unwrap();
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.recv(&r1);
+    /// let oper2 = sel.recv(&r2);
+    ///
+    /// // Both operations are initially ready, so a random one will be executed.
+    /// let oper = sel.try_select();
+    /// match oper {
+    ///     Err(_) => panic!("both operations should be ready"),
+    ///     Ok(oper) => match oper.index() {
+    ///         i if i == oper1 => assert_eq!(oper.recv(&r1), Ok(10)),
+    ///         i if i == oper2 => assert_eq!(oper.recv(&r2), Ok(20)),
+    ///         _ => unreachable!(),
+    ///     }
+    /// }
+    /// ```
+    pub fn try_select(&mut self) -> Result<SelectedOperation<'a>, TrySelectError> {
+        try_select(&mut self.handles)
+    }
+
+    /// Blocks until one of the operations becomes ready and selects it.
+    ///
+    /// Once an operation becomes ready, it is selected and returned. If multiple operations are
+    /// ready at the same time, a random one among them is selected.
+    ///
+    /// An operation is considered to be ready if it doesn't have to block. Note that it is ready
+    /// even when it will simply return an error because the channel is disconnected.
+    ///
+    /// The selected operation must be completed with [`SelectedOperation::send`]
+    /// or [`SelectedOperation::recv`].
+    ///
+    /// # Panics
+    ///
+    /// Panics if no operations have been added to `Select`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::Duration;
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let (s1, r1) = unbounded();
+    /// let (s2, r2) = unbounded();
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     s1.send(10).unwrap();
+    /// });
+    /// thread::spawn(move || s2.send(20).unwrap());
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.recv(&r1);
+    /// let oper2 = sel.recv(&r2);
+    ///
+    /// // The second operation will be selected because it becomes ready first.
+    /// let oper = sel.select();
+    /// match oper.index() {
+    ///     i if i == oper1 => assert_eq!(oper.recv(&r1), Ok(10)),
+    ///     i if i == oper2 => assert_eq!(oper.recv(&r2), Ok(20)),
+    ///     _ => unreachable!(),
+    /// }
+    /// ```
+    pub fn select(&mut self) -> SelectedOperation<'a> {
+        select(&mut self.handles)
+    }
+
+    /// Blocks for a limited time until one of the operations becomes ready and selects it.
+    ///
+    /// If an operation becomes ready, it is selected and returned. If multiple operations are
+    /// ready at the same time, a random one among them is selected. If none of the operations
+    /// become ready for the specified duration, an error is returned.
+    ///
+    /// An operation is considered to be ready if it doesn't have to block. Note that it is ready
+    /// even when it will simply return an error because the channel is disconnected.
+    ///
+    /// The selected operation must be completed with [`SelectedOperation::send`]
+    /// or [`SelectedOperation::recv`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::Duration;
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let (s1, r1) = unbounded();
+    /// let (s2, r2) = unbounded();
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     s1.send(10).unwrap();
+    /// });
+    /// thread::spawn(move || s2.send(20).unwrap());
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.recv(&r1);
+    /// let oper2 = sel.recv(&r2);
+    ///
+    /// // The second operation will be selected because it becomes ready first.
+    /// let oper = sel.select_timeout(Duration::from_millis(500));
+    /// match oper {
+    ///     Err(_) => panic!("should not have timed out"),
+    ///     Ok(oper) => match oper.index() {
+    ///         i if i == oper1 => assert_eq!(oper.recv(&r1), Ok(10)),
+    ///         i if i == oper2 => assert_eq!(oper.recv(&r2), Ok(20)),
+    ///         _ => unreachable!(),
+    ///     }
+    /// }
+    /// ```
+    pub fn select_timeout(
+        &mut self,
+        timeout: Duration,
+    ) -> Result<SelectedOperation<'a>, SelectTimeoutError> {
+        select_timeout(&mut self.handles, timeout)
+    }
+
+    /// Blocks until a given deadline, or until one of the operations becomes ready and selects it.
+    ///
+    /// If an operation becomes ready, it is selected and returned. If multiple operations are
+    /// ready at the same time, a random one among them is selected. If none of the operations
+    /// become ready before the given deadline, an error is returned.
+    ///
+    /// An operation is considered to be ready if it doesn't have to block. Note that it is ready
+    /// even when it will simply return an error because the channel is disconnected.
+    ///
+    /// The selected operation must be completed with [`SelectedOperation::send`]
+    /// or [`SelectedOperation::recv`].
+    ///
+    /// [`SelectedOperation::send`]: struct.SelectedOperation.html#method.send
+    /// [`SelectedOperation::recv`]: struct.SelectedOperation.html#method.recv
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::{Instant, Duration};
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let (s1, r1) = unbounded();
+    /// let (s2, r2) = unbounded();
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     s1.send(10).unwrap();
+    /// });
+    /// thread::spawn(move || s2.send(20).unwrap());
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.recv(&r1);
+    /// let oper2 = sel.recv(&r2);
+    ///
+    /// let deadline = Instant::now() + Duration::from_millis(500);
+    ///
+    /// // The second operation will be selected because it becomes ready first.
+    /// let oper = sel.select_deadline(deadline);
+    /// match oper {
+    ///     Err(_) => panic!("should not have timed out"),
+    ///     Ok(oper) => match oper.index() {
+    ///         i if i == oper1 => assert_eq!(oper.recv(&r1), Ok(10)),
+    ///         i if i == oper2 => assert_eq!(oper.recv(&r2), Ok(20)),
+    ///         _ => unreachable!(),
+    ///     }
+    /// }
+    /// ```
+    pub fn select_deadline(
+        &mut self,
+        deadline: Instant,
+    ) -> Result<SelectedOperation<'a>, SelectTimeoutError> {
+        select_deadline(&mut self.handles, deadline)
+    }
+
+    /// Attempts to find a ready operation without blocking.
+    ///
+    /// If an operation is ready, its index is returned. If multiple operations are ready at the
+    /// same time, a random one among them is chosen. If none of the operations are ready, an error
+    /// is returned.
+    ///
+    /// An operation is considered to be ready if it doesn't have to block. Note that it is ready
+    /// even when it will simply return an error because the channel is disconnected.
+    ///
+    /// Note that this method might return with success spuriously, so it's a good idea to always
+    /// double check if the operation is really ready.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let (s1, r1) = unbounded();
+    /// let (s2, r2) = unbounded();
+    ///
+    /// s1.send(10).unwrap();
+    /// s2.send(20).unwrap();
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.recv(&r1);
+    /// let oper2 = sel.recv(&r2);
+    ///
+    /// // Both operations are initially ready, so a random one will be chosen.
+    /// match sel.try_ready() {
+    ///     Err(_) => panic!("both operations should be ready"),
+    ///     Ok(i) if i == oper1 => assert_eq!(r1.try_recv(), Ok(10)),
+    ///     Ok(i) if i == oper2 => assert_eq!(r2.try_recv(), Ok(20)),
+    ///     Ok(_) => unreachable!(),
+    /// }
+    /// ```
+    pub fn try_ready(&mut self) -> Result<usize, TryReadyError> {
+        match run_ready(&mut self.handles, Timeout::Now) {
+            None => Err(TryReadyError),
+            Some(index) => Ok(index),
+        }
+    }
+
+    /// Blocks until one of the operations becomes ready.
+    ///
+    /// Once an operation becomes ready, its index is returned. If multiple operations are ready at
+    /// the same time, a random one among them is chosen.
+    ///
+    /// An operation is considered to be ready if it doesn't have to block. Note that it is ready
+    /// even when it will simply return an error because the channel is disconnected.
+    ///
+    /// Note that this method might return with success spuriously, so it's a good idea to always
+    /// double check if the operation is really ready.
+    ///
+    /// # Panics
+    ///
+    /// Panics if no operations have been added to `Select`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::Duration;
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let (s1, r1) = unbounded();
+    /// let (s2, r2) = unbounded();
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     s1.send(10).unwrap();
+    /// });
+    /// thread::spawn(move || s2.send(20).unwrap());
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.recv(&r1);
+    /// let oper2 = sel.recv(&r2);
+    ///
+    /// // The second operation will be selected because it becomes ready first.
+    /// match sel.ready() {
+    ///     i if i == oper1 => assert_eq!(r1.try_recv(), Ok(10)),
+    ///     i if i == oper2 => assert_eq!(r2.try_recv(), Ok(20)),
+    ///     _ => unreachable!(),
+    /// }
+    /// ```
+    pub fn ready(&mut self) -> usize {
+        if self.handles.is_empty() {
+            panic!("no operations have been added to `Select`");
+        }
+
+        run_ready(&mut self.handles, Timeout::Never).unwrap()
+    }
+
+    /// Blocks for a limited time until one of the operations becomes ready.
+    ///
+    /// If an operation becomes ready, its index is returned. If multiple operations are ready at
+    /// the same time, a random one among them is chosen. If none of the operations become ready
+    /// for the specified duration, an error is returned.
+    ///
+    /// An operation is considered to be ready if it doesn't have to block. Note that it is ready
+    /// even when it will simply return an error because the channel is disconnected.
+    ///
+    /// Note that this method might return with success spuriously, so it's a good idea to double
+    /// check if the operation is really ready.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::Duration;
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let (s1, r1) = unbounded();
+    /// let (s2, r2) = unbounded();
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     s1.send(10).unwrap();
+    /// });
+    /// thread::spawn(move || s2.send(20).unwrap());
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.recv(&r1);
+    /// let oper2 = sel.recv(&r2);
+    ///
+    /// // The second operation will be selected because it becomes ready first.
+    /// match sel.ready_timeout(Duration::from_millis(500)) {
+    ///     Err(_) => panic!("should not have timed out"),
+    ///     Ok(i) if i == oper1 => assert_eq!(r1.try_recv(), Ok(10)),
+    ///     Ok(i) if i == oper2 => assert_eq!(r2.try_recv(), Ok(20)),
+    ///     Ok(_) => unreachable!(),
+    /// }
+    /// ```
+    pub fn ready_timeout(&mut self, timeout: Duration) -> Result<usize, ReadyTimeoutError> {
+        self.ready_deadline(Instant::now() + timeout)
+    }
+
+    /// Blocks until a given deadline, or until one of the operations becomes ready.
+    ///
+    /// If an operation becomes ready, its index is returned. If multiple operations are ready at
+    /// the same time, a random one among them is chosen. If none of the operations become ready
+    /// before the deadline, an error is returned.
+    ///
+    /// An operation is considered to be ready if it doesn't have to block. Note that it is ready
+    /// even when it will simply return an error because the channel is disconnected.
+    ///
+    /// Note that this method might return with success spuriously, so it's a good idea to double
+    /// check if the operation is really ready.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::thread;
+    /// use std::time::{Duration, Instant};
+    /// use crossbeam_channel::{unbounded, Select};
+    ///
+    /// let deadline = Instant::now() + Duration::from_millis(500);
+    ///
+    /// let (s1, r1) = unbounded();
+    /// let (s2, r2) = unbounded();
+    ///
+    /// thread::spawn(move || {
+    ///     thread::sleep(Duration::from_secs(1));
+    ///     s1.send(10).unwrap();
+    /// });
+    /// thread::spawn(move || s2.send(20).unwrap());
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.recv(&r1);
+    /// let oper2 = sel.recv(&r2);
+    ///
+    /// // The second operation will be selected because it becomes ready first.
+    /// match sel.ready_deadline(deadline) {
+    ///     Err(_) => panic!("should not have timed out"),
+    ///     Ok(i) if i == oper1 => assert_eq!(r1.try_recv(), Ok(10)),
+    ///     Ok(i) if i == oper2 => assert_eq!(r2.try_recv(), Ok(20)),
+    ///     Ok(_) => unreachable!(),
+    /// }
+    /// ```
+    pub fn ready_deadline(&mut self, deadline: Instant) -> Result<usize, ReadyTimeoutError> {
+        match run_ready(&mut self.handles, Timeout::At(deadline)) {
+            None => Err(ReadyTimeoutError),
+            Some(index) => Ok(index),
+        }
+    }
+}
+
+impl<'a> Clone for Select<'a> {
+    fn clone(&self) -> Select<'a> {
+        Select {
+            handles: self.handles.clone(),
+            next_index: self.next_index,
+        }
+    }
+}
+
+impl<'a> Default for Select<'a> {
+    fn default() -> Select<'a> {
+        Select::new()
+    }
+}
+
+impl fmt::Debug for Select<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("Select { .. }")
+    }
+}
+
+/// A selected operation that needs to be completed.
+///
+/// To complete the operation, call [`send`] or [`recv`].
+///
+/// # Panics
+///
+/// Forgetting to complete the operation is an error and might lead to deadlocks. If a
+/// `SelectedOperation` is dropped without completion, a panic occurs.
+///
+/// [`send`]: SelectedOperation::send
+/// [`recv`]: SelectedOperation::recv
+#[must_use]
+pub struct SelectedOperation<'a> {
+    /// Token needed to complete the operation.
+    token: Token,
+
+    /// The index of the selected operation.
+    index: usize,
+
+    /// The address of the selected `Sender` or `Receiver`.
+    ptr: *const u8,
+
+    /// Indicates that `Sender`s and `Receiver`s are borrowed.
+    _marker: PhantomData<&'a ()>,
+}
+
+impl SelectedOperation<'_> {
+    /// Returns the index of the selected operation.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{bounded, Select};
+    ///
+    /// let (s1, r1) = bounded::<()>(0);
+    /// let (s2, r2) = bounded::<()>(0);
+    /// let (s3, r3) = bounded::<()>(1);
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.send(&s1);
+    /// let oper2 = sel.recv(&r2);
+    /// let oper3 = sel.send(&s3);
+    ///
+    /// // Only the last operation is ready.
+    /// let oper = sel.select();
+    /// assert_eq!(oper.index(), 2);
+    /// assert_eq!(oper.index(), oper3);
+    ///
+    /// // Complete the operation.
+    /// oper.send(&s3, ()).unwrap();
+    /// ```
+    pub fn index(&self) -> usize {
+        self.index
+    }
+
+    /// Completes the send operation.
+    ///
+    /// The passed [`Sender`] reference must be the same one that was used in [`Select::send`]
+    /// when the operation was added.
+    ///
+    /// # Panics
+    ///
+    /// Panics if an incorrect [`Sender`] reference is passed.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{bounded, Select, SendError};
+    ///
+    /// let (s, r) = bounded::<i32>(0);
+    /// drop(r);
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.send(&s);
+    ///
+    /// let oper = sel.select();
+    /// assert_eq!(oper.index(), oper1);
+    /// assert_eq!(oper.send(&s, 10), Err(SendError(10)));
+    /// ```
+    pub fn send<T>(mut self, s: &Sender<T>, msg: T) -> Result<(), SendError<T>> {
+        assert!(
+            s as *const Sender<T> as *const u8 == self.ptr,
+            "passed a sender that wasn't selected",
+        );
+        let res = unsafe { channel::write(s, &mut self.token, msg) };
+        mem::forget(self);
+        res.map_err(SendError)
+    }
+
+    /// Completes the receive operation.
+    ///
+    /// The passed [`Receiver`] reference must be the same one that was used in [`Select::recv`]
+    /// when the operation was added.
+    ///
+    /// # Panics
+    ///
+    /// Panics if an incorrect [`Receiver`] reference is passed.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::{bounded, Select, RecvError};
+    ///
+    /// let (s, r) = bounded::<i32>(0);
+    /// drop(s);
+    ///
+    /// let mut sel = Select::new();
+    /// let oper1 = sel.recv(&r);
+    ///
+    /// let oper = sel.select();
+    /// assert_eq!(oper.index(), oper1);
+    /// assert_eq!(oper.recv(&r), Err(RecvError));
+    /// ```
+    pub fn recv<T>(mut self, r: &Receiver<T>) -> Result<T, RecvError> {
+        assert!(
+            r as *const Receiver<T> as *const u8 == self.ptr,
+            "passed a receiver that wasn't selected",
+        );
+        let res = unsafe { channel::read(r, &mut self.token) };
+        mem::forget(self);
+        res.map_err(|_| RecvError)
+    }
+}
+
+impl fmt::Debug for SelectedOperation<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("SelectedOperation { .. }")
+    }
+}
+
+impl Drop for SelectedOperation<'_> {
+    fn drop(&mut self) {
+        panic!("dropped `SelectedOperation` without completing the operation");
+    }
+}
diff --git a/src/select_macro.rs b/src/select_macro.rs
new file mode 100644
index 0000000..f8b247e
--- /dev/null
+++ b/src/select_macro.rs
@@ -0,0 +1,1166 @@
+//! The `select!` macro.
+
+/// A helper macro for `select!` to hide the long list of macro patterns from the documentation.
+///
+/// The macro consists of two stages:
+/// 1. Parsing
+/// 2. Code generation
+///
+/// The parsing stage consists of these subparts:
+/// 1. `@list`: Turns a list of tokens into a list of cases.
+/// 2. `@list_errorN`: Diagnoses the syntax error.
+/// 3. `@case`: Parses a single case and verifies its argument list.
+///
+/// The codegen stage consists of these subparts:
+/// 1. `@init`: Attempts to optimize `select!` away and initializes the list of handles.
+/// 1. `@count`: Counts the listed cases.
+/// 3. `@add`: Adds send/receive operations to the list of handles and starts selection.
+/// 4. `@complete`: Completes the selected send/receive operation.
+///
+/// If the parsing stage encounters a syntax error or the codegen stage ends up with too many
+/// cases to process, the macro fails with a compile-time error.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! crossbeam_channel_internal {
+    // The list is empty. Now check the arguments of each processed case.
+    (@list
+        ()
+        ($($head:tt)*)
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @case
+            ($($head)*)
+            ()
+            ()
+        )
+    };
+    // If necessary, insert an empty argument list after `default`.
+    (@list
+        (default => $($tail:tt)*)
+        ($($head:tt)*)
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @list
+            (default() => $($tail)*)
+            ($($head)*)
+        )
+    };
+    // But print an error if `default` is followed by a `->`.
+    (@list
+        (default -> $($tail:tt)*)
+        ($($head:tt)*)
+    ) => {
+        compile_error!(
+            "expected `=>` after `default` case, found `->`"
+        )
+    };
+    // Print an error if there's an `->` after the argument list in the default case.
+    (@list
+        (default $args:tt -> $($tail:tt)*)
+        ($($head:tt)*)
+    ) => {
+        compile_error!(
+            "expected `=>` after `default` case, found `->`"
+        )
+    };
+    // Print an error if there is a missing result in a recv case.
+    (@list
+        (recv($($args:tt)*) => $($tail:tt)*)
+        ($($head:tt)*)
+    ) => {
+        compile_error!(
+            "expected `->` after `recv` case, found `=>`"
+        )
+    };
+    // Print an error if there is a missing result in a send case.
+    (@list
+        (send($($args:tt)*) => $($tail:tt)*)
+        ($($head:tt)*)
+    ) => {
+        compile_error!(
+            "expected `->` after `send` operation, found `=>`"
+        )
+    };
+    // Make sure the arrow and the result are not repeated.
+    (@list
+        ($case:ident $args:tt -> $res:tt -> $($tail:tt)*)
+        ($($head:tt)*)
+    ) => {
+        compile_error!("expected `=>`, found `->`")
+    };
+    // Print an error if there is a semicolon after the block.
+    (@list
+        ($case:ident $args:tt $(-> $res:pat)* => $body:block; $($tail:tt)*)
+        ($($head:tt)*)
+    ) => {
+        compile_error!(
+            "did you mean to put a comma instead of the semicolon after `}`?"
+        )
+    };
+    // The first case is separated by a comma.
+    (@list
+        ($case:ident ($($args:tt)*) $(-> $res:pat)* => $body:expr, $($tail:tt)*)
+        ($($head:tt)*)
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @list
+            ($($tail)*)
+            ($($head)* $case ($($args)*) $(-> $res)* => { $body },)
+        )
+    };
+    // Don't require a comma after the case if it has a proper block.
+    (@list
+        ($case:ident ($($args:tt)*) $(-> $res:pat)* => $body:block $($tail:tt)*)
+        ($($head:tt)*)
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @list
+            ($($tail)*)
+            ($($head)* $case ($($args)*) $(-> $res)* => { $body },)
+        )
+    };
+    // Only one case remains.
+    (@list
+        ($case:ident ($($args:tt)*) $(-> $res:pat)* => $body:expr)
+        ($($head:tt)*)
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @list
+            ()
+            ($($head)* $case ($($args)*) $(-> $res)* => { $body },)
+        )
+    };
+    // Accept a trailing comma at the end of the list.
+    (@list
+        ($case:ident ($($args:tt)*) $(-> $res:pat)* => $body:expr,)
+        ($($head:tt)*)
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @list
+            ()
+            ($($head)* $case ($($args)*) $(-> $res)* => { $body },)
+        )
+    };
+    // Diagnose and print an error.
+    (@list
+        ($($tail:tt)*)
+        ($($head:tt)*)
+    ) => {
+        $crate::crossbeam_channel_internal!(@list_error1 $($tail)*)
+    };
+    // Stage 1: check the case type.
+    (@list_error1 recv $($tail:tt)*) => {
+        $crate::crossbeam_channel_internal!(@list_error2 recv $($tail)*)
+    };
+    (@list_error1 send $($tail:tt)*) => {
+        $crate::crossbeam_channel_internal!(@list_error2 send $($tail)*)
+    };
+    (@list_error1 default $($tail:tt)*) => {
+        $crate::crossbeam_channel_internal!(@list_error2 default $($tail)*)
+    };
+    (@list_error1 $t:tt $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "expected one of `recv`, `send`, or `default`, found `",
+                stringify!($t),
+                "`",
+            )
+        )
+    };
+    (@list_error1 $($tail:tt)*) => {
+        $crate::crossbeam_channel_internal!(@list_error2 $($tail)*);
+    };
+    // Stage 2: check the argument list.
+    (@list_error2 $case:ident) => {
+        compile_error!(
+            concat!(
+                "missing argument list after `",
+                stringify!($case),
+                "`",
+            )
+        )
+    };
+    (@list_error2 $case:ident => $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "missing argument list after `",
+                stringify!($case),
+                "`",
+            )
+        )
+    };
+    (@list_error2 $($tail:tt)*) => {
+        $crate::crossbeam_channel_internal!(@list_error3 $($tail)*)
+    };
+    // Stage 3: check the `=>` and what comes after it.
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)*) => {
+        compile_error!(
+            concat!(
+                "missing `=>` after `",
+                stringify!($case),
+                "` case",
+            )
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)* =>) => {
+        compile_error!(
+            "expected expression after `=>`"
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)* => $body:expr; $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "did you mean to put a comma instead of the semicolon after `",
+                stringify!($body),
+                "`?",
+            )
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)* => recv($($a:tt)*) $($tail:tt)*) => {
+        compile_error!(
+            "expected an expression after `=>`"
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)* => send($($a:tt)*) $($tail:tt)*) => {
+        compile_error!(
+            "expected an expression after `=>`"
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)* => default($($a:tt)*) $($tail:tt)*) => {
+        compile_error!(
+            "expected an expression after `=>`"
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)* => $f:ident($($a:tt)*) $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "did you mean to put a comma after `",
+                stringify!($f),
+                "(",
+                stringify!($($a)*),
+                ")`?",
+            )
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)* => $f:ident!($($a:tt)*) $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "did you mean to put a comma after `",
+                stringify!($f),
+                "!(",
+                stringify!($($a)*),
+                ")`?",
+            )
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)* => $f:ident![$($a:tt)*] $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "did you mean to put a comma after `",
+                stringify!($f),
+                "![",
+                stringify!($($a)*),
+                "]`?",
+            )
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)* => $f:ident!{$($a:tt)*} $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "did you mean to put a comma after `",
+                stringify!($f),
+                "!{",
+                stringify!($($a)*),
+                "}`?",
+            )
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) $(-> $r:pat)* => $body:tt $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "did you mean to put a comma after `",
+                stringify!($body),
+                "`?",
+            )
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) -> => $($tail:tt)*) => {
+        compile_error!("missing pattern after `->`")
+    };
+    (@list_error3 $case:ident($($args:tt)*) $t:tt $(-> $r:pat)* => $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "expected `->`, found `",
+                stringify!($t),
+                "`",
+            )
+        )
+    };
+    (@list_error3 $case:ident($($args:tt)*) -> $t:tt $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "expected a pattern, found `",
+                stringify!($t),
+                "`",
+            )
+        )
+    };
+    (@list_error3 recv($($args:tt)*) $t:tt $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "expected `->`, found `",
+                stringify!($t),
+                "`",
+            )
+        )
+    };
+    (@list_error3 send($($args:tt)*) $t:tt $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "expected `->`, found `",
+                stringify!($t),
+                "`",
+            )
+        )
+    };
+    (@list_error3 recv $args:tt $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "expected an argument list after `recv`, found `",
+                stringify!($args),
+                "`",
+            )
+        )
+    };
+    (@list_error3 send $args:tt $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "expected an argument list after `send`, found `",
+                stringify!($args),
+                "`",
+            )
+        )
+    };
+    (@list_error3 default $args:tt $($tail:tt)*) => {
+        compile_error!(
+            concat!(
+                "expected an argument list or `=>` after `default`, found `",
+                stringify!($args),
+                "`",
+            )
+        )
+    };
+    (@list_error3 $($tail:tt)*) => {
+        $crate::crossbeam_channel_internal!(@list_error4 $($tail)*)
+    };
+    // Stage 4: fail with a generic error message.
+    (@list_error4 $($tail:tt)*) => {
+        compile_error!("invalid syntax")
+    };
+
+    // Success! All cases were parsed.
+    (@case
+        ()
+        $cases:tt
+        $default:tt
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @init
+            $cases
+            $default
+        )
+    };
+
+    // Check the format of a recv case.
+    (@case
+        (recv($r:expr) -> $res:pat => $body:tt, $($tail:tt)*)
+        ($($cases:tt)*)
+        $default:tt
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @case
+            ($($tail)*)
+            ($($cases)* recv($r) -> $res => $body,)
+            $default
+        )
+    };
+    // Allow trailing comma...
+    (@case
+        (recv($r:expr,) -> $res:pat => $body:tt, $($tail:tt)*)
+        ($($cases:tt)*)
+        $default:tt
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @case
+            ($($tail)*)
+            ($($cases)* recv($r) -> $res => $body,)
+            $default
+        )
+    };
+    // Print an error if the argument list is invalid.
+    (@case
+        (recv($($args:tt)*) -> $res:pat => $body:tt, $($tail:tt)*)
+        ($($cases:tt)*)
+        $default:tt
+    ) => {
+        compile_error!(
+            concat!(
+                "invalid argument list in `recv(",
+                stringify!($($args)*),
+                ")`",
+            )
+        )
+    };
+    // Print an error if there is no argument list.
+    (@case
+        (recv $t:tt $($tail:tt)*)
+        ($($cases:tt)*)
+        $default:tt
+    ) => {
+        compile_error!(
+            concat!(
+                "expected an argument list after `recv`, found `",
+                stringify!($t),
+                "`",
+            )
+        )
+    };
+
+    // Check the format of a send case.
+    (@case
+        (send($s:expr, $m:expr) -> $res:pat => $body:tt, $($tail:tt)*)
+        ($($cases:tt)*)
+        $default:tt
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @case
+            ($($tail)*)
+            ($($cases)* send($s, $m) -> $res => $body,)
+            $default
+        )
+    };
+    // Allow trailing comma...
+    (@case
+        (send($s:expr, $m:expr,) -> $res:pat => $body:tt, $($tail:tt)*)
+        ($($cases:tt)*)
+        $default:tt
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @case
+            ($($tail)*)
+            ($($cases)* send($s, $m) -> $res => $body,)
+            $default
+        )
+    };
+    // Print an error if the argument list is invalid.
+    (@case
+        (send($($args:tt)*) -> $res:pat => $body:tt, $($tail:tt)*)
+        ($($cases:tt)*)
+        $default:tt
+    ) => {
+        compile_error!(
+            concat!(
+                "invalid argument list in `send(",
+                stringify!($($args)*),
+                ")`",
+            )
+        )
+    };
+    // Print an error if there is no argument list.
+    (@case
+        (send $t:tt $($tail:tt)*)
+        ($($cases:tt)*)
+        $default:tt
+    ) => {
+        compile_error!(
+            concat!(
+                "expected an argument list after `send`, found `",
+                stringify!($t),
+                "`",
+            )
+        )
+    };
+
+    // Check the format of a default case.
+    (@case
+        (default() => $body:tt, $($tail:tt)*)
+        $cases:tt
+        ()
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @case
+            ($($tail)*)
+            $cases
+            (default() => $body,)
+        )
+    };
+    // Check the format of a default case with timeout.
+    (@case
+        (default($timeout:expr) => $body:tt, $($tail:tt)*)
+        $cases:tt
+        ()
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @case
+            ($($tail)*)
+            $cases
+            (default($timeout) => $body,)
+        )
+    };
+    // Allow trailing comma...
+    (@case
+        (default($timeout:expr,) => $body:tt, $($tail:tt)*)
+        $cases:tt
+        ()
+    ) => {
+        $crate::crossbeam_channel_internal!(
+            @case
+            ($($tail)*)
+            $cases
+            (default($timeout) => $body,)
+        )
+    };
+    // Check for duplicate default cases...
+    (@case
+        (default $($tail:tt)*)
+        $cases:tt
+        ($($def:tt)+)
+    ) => {
+        compile_error!(
+            "there can be only one `default` case in a `select!` block"
+        )
+    };
+    // Print an error if the argument list is invalid.
+    (@case
+        (default($($args:tt)*) => $body:tt, $($tail:tt)*)
+        $cases:tt
+        $default:tt
+    ) => {
+        compile_error!(
+            concat!(
+                "invalid argument list in `default(",
+                stringify!($($args)*),
+                ")`",
+            )
+        )
+    };
+    // Print an error if there is an unexpected token after `default`.
+    (@case
+        (default $t:tt $($tail:tt)*)
+        $cases:tt
+        $default:tt
+    ) => {
+        compile_error!(
+            concat!(
+                "expected an argument list or `=>` after `default`, found `",
+                stringify!($t),
+                "`",
+            )
+        )
+    };
+
+    // The case was not consumed, therefore it must be invalid.
+    (@case
+        ($case:ident $($tail:tt)*)
+        $cases:tt
+        $default:tt
+    ) => {
+        compile_error!(
+            concat!(
+                "expected one of `recv`, `send`, or `default`, found `",
+                stringify!($case),
+                "`",
+            )
+        )
+    };
+
+    // Optimize `select!` into `try_recv()`.
+    (@init
+        (recv($r:expr) -> $res:pat => $recv_body:tt,)
+        (default() => $default_body:tt,)
+    ) => {{
+        match $r {
+            ref _r => {
+                let _r: &$crate::Receiver<_> = _r;
+                match _r.try_recv() {
+                    ::std::result::Result::Err($crate::TryRecvError::Empty) => {
+                        $default_body
+                    }
+                    _res => {
+                        let _res = _res.map_err(|_| $crate::RecvError);
+                        let $res = _res;
+                        $recv_body
+                    }
+                }
+            }
+        }
+    }};
+    // Optimize `select!` into `recv()`.
+    (@init
+        (recv($r:expr) -> $res:pat => $body:tt,)
+        ()
+    ) => {{
+        match $r {
+            ref _r => {
+                let _r: &$crate::Receiver<_> = _r;
+                let _res = _r.recv();
+                let $res = _res;
+                $body
+            }
+        }
+    }};
+    // Optimize `select!` into `recv_timeout()`.
+    (@init
+        (recv($r:expr) -> $res:pat => $recv_body:tt,)
+        (default($timeout:expr) => $default_body:tt,)
+    ) => {{
+        match $r {
+            ref _r => {
+                let _r: &$crate::Receiver<_> = _r;
+                match _r.recv_timeout($timeout) {
+                    ::std::result::Result::Err($crate::RecvTimeoutError::Timeout) => {
+                        $default_body
+                    }
+                    _res => {
+                        let _res = _res.map_err(|_| $crate::RecvError);
+                        let $res = _res;
+                        $recv_body
+                    }
+                }
+            }
+        }
+    }};
+
+    // // Optimize the non-blocking case with two receive operations.
+    // (@init
+    //     (recv($r1:expr) -> $res1:pat => $recv_body1:tt,)
+    //     (recv($r2:expr) -> $res2:pat => $recv_body2:tt,)
+    //     (default() => $default_body:tt,)
+    // ) => {{
+    //     match $r1 {
+    //         ref _r1 => {
+    //             let _r1: &$crate::Receiver<_> = _r1;
+    //
+    //             match $r2 {
+    //                 ref _r2 => {
+    //                     let _r2: &$crate::Receiver<_> = _r2;
+    //
+    //                     // TODO(stjepang): Implement this optimization.
+    //                 }
+    //             }
+    //         }
+    //     }
+    // }};
+    // // Optimize the blocking case with two receive operations.
+    // (@init
+    //     (recv($r1:expr) -> $res1:pat => $body1:tt,)
+    //     (recv($r2:expr) -> $res2:pat => $body2:tt,)
+    //     ()
+    // ) => {{
+    //     match $r1 {
+    //         ref _r1 => {
+    //             let _r1: &$crate::Receiver<_> = _r1;
+    //
+    //             match $r2 {
+    //                 ref _r2 => {
+    //                     let _r2: &$crate::Receiver<_> = _r2;
+    //
+    //                     // TODO(stjepang): Implement this optimization.
+    //                 }
+    //             }
+    //         }
+    //     }
+    // }};
+    // // Optimize the case with two receive operations and a timeout.
+    // (@init
+    //     (recv($r1:expr) -> $res1:pat => $recv_body1:tt,)
+    //     (recv($r2:expr) -> $res2:pat => $recv_body2:tt,)
+    //     (default($timeout:expr) => $default_body:tt,)
+    // ) => {{
+    //     match $r1 {
+    //         ref _r1 => {
+    //             let _r1: &$crate::Receiver<_> = _r1;
+    //
+    //             match $r2 {
+    //                 ref _r2 => {
+    //                     let _r2: &$crate::Receiver<_> = _r2;
+    //
+    //                     // TODO(stjepang): Implement this optimization.
+    //                 }
+    //             }
+    //         }
+    //     }
+    // }};
+
+    // // Optimize `select!` into `try_send()`.
+    // (@init
+    //     (send($s:expr, $m:expr) -> $res:pat => $send_body:tt,)
+    //     (default() => $default_body:tt,)
+    // ) => {{
+    //     match $s {
+    //         ref _s => {
+    //             let _s: &$crate::Sender<_> = _s;
+    //             // TODO(stjepang): Implement this optimization.
+    //         }
+    //     }
+    // }};
+    // // Optimize `select!` into `send()`.
+    // (@init
+    //     (send($s:expr, $m:expr) -> $res:pat => $body:tt,)
+    //     ()
+    // ) => {{
+    //     match $s {
+    //         ref _s => {
+    //             let _s: &$crate::Sender<_> = _s;
+    //             // TODO(stjepang): Implement this optimization.
+    //         }
+    //     }
+    // }};
+    // // Optimize `select!` into `send_timeout()`.
+    // (@init
+    //     (send($s:expr, $m:expr) -> $res:pat => $body:tt,)
+    //     (default($timeout:expr) => $body:tt,)
+    // ) => {{
+    //     match $s {
+    //         ref _s => {
+    //             let _s: &$crate::Sender<_> = _s;
+    //             // TODO(stjepang): Implement this optimization.
+    //         }
+    //     }
+    // }};
+
+    // Create the list of handles and add operations to it.
+    (@init
+        ($($cases:tt)*)
+        $default:tt
+    ) => {{
+        const _LEN: usize = $crate::crossbeam_channel_internal!(@count ($($cases)*));
+        let _handle: &$crate::internal::SelectHandle = &$crate::never::<()>();
+
+        #[allow(unused_mut)]
+        let mut _sel = [(_handle, 0, ::std::ptr::null()); _LEN];
+
+        $crate::crossbeam_channel_internal!(
+            @add
+            _sel
+            ($($cases)*)
+            $default
+            (
+                (0usize _oper0)
+                (1usize _oper1)
+                (2usize _oper2)
+                (3usize _oper3)
+                (4usize _oper4)
+                (5usize _oper5)
+                (6usize _oper6)
+                (7usize _oper7)
+                (8usize _oper8)
+                (9usize _oper9)
+                (10usize _oper10)
+                (11usize _oper11)
+                (12usize _oper12)
+                (13usize _oper13)
+                (14usize _oper14)
+                (15usize _oper15)
+                (16usize _oper16)
+                (17usize _oper17)
+                (18usize _oper18)
+                (19usize _oper19)
+                (20usize _oper20)
+                (21usize _oper21)
+                (22usize _oper22)
+                (23usize _oper23)
+                (24usize _oper24)
+                (25usize _oper25)
+                (26usize _oper26)
+                (27usize _oper27)
+                (28usize _oper28)
+                (29usize _oper29)
+                (30usize _oper30)
+                (31usize _oper31)
+            )
+            ()
+        )
+    }};
+
+    // Count the listed cases.
+    (@count ()) => {
+        0
+    };
+    (@count ($oper:ident $args:tt -> $res:pat => $body:tt, $($cases:tt)*)) => {
+        1 + $crate::crossbeam_channel_internal!(@count ($($cases)*))
+    };
+
+    // Run blocking selection.
+    (@add
+        $sel:ident
+        ()
+        ()
+        $labels:tt
+        $cases:tt
+    ) => {{
+        let _oper: $crate::SelectedOperation<'_> = {
+            let _oper = $crate::internal::select(&mut $sel);
+
+            // Erase the lifetime so that `sel` can be dropped early even without NLL.
+            unsafe { ::std::mem::transmute(_oper) }
+        };
+
+        $crate::crossbeam_channel_internal! {
+            @complete
+            $sel
+            _oper
+            $cases
+        }
+    }};
+    // Run non-blocking selection.
+    (@add
+        $sel:ident
+        ()
+        (default() => $body:tt,)
+        $labels:tt
+        $cases:tt
+    ) => {{
+        let _oper: ::std::option::Option<$crate::SelectedOperation<'_>> = {
+            let _oper = $crate::internal::try_select(&mut $sel);
+
+            // Erase the lifetime so that `sel` can be dropped early even without NLL.
+            unsafe { ::std::mem::transmute(_oper) }
+        };
+
+        match _oper {
+            None => {
+                { $sel };
+                $body
+            }
+            Some(_oper) => {
+                $crate::crossbeam_channel_internal! {
+                    @complete
+                    $sel
+                    _oper
+                    $cases
+                }
+            }
+        }
+    }};
+    // Run selection with a timeout.
+    (@add
+        $sel:ident
+        ()
+        (default($timeout:expr) => $body:tt,)
+        $labels:tt
+        $cases:tt
+    ) => {{
+        let _oper: ::std::option::Option<$crate::SelectedOperation<'_>> = {
+            let _oper = $crate::internal::select_timeout(&mut $sel, $timeout);
+
+            // Erase the lifetime so that `sel` can be dropped early even without NLL.
+            unsafe { ::std::mem::transmute(_oper) }
+        };
+
+        match _oper {
+            ::std::option::Option::None => {
+                { $sel };
+                $body
+            }
+            ::std::option::Option::Some(_oper) => {
+                $crate::crossbeam_channel_internal! {
+                    @complete
+                    $sel
+                    _oper
+                    $cases
+                }
+            }
+        }
+    }};
+    // Have we used up all labels?
+    (@add
+        $sel:ident
+        $input:tt
+        $default:tt
+        ()
+        $cases:tt
+    ) => {
+        compile_error!("too many operations in a `select!` block")
+    };
+    // Add a receive operation to `sel`.
+    (@add
+        $sel:ident
+        (recv($r:expr) -> $res:pat => $body:tt, $($tail:tt)*)
+        $default:tt
+        (($i:tt $var:ident) $($labels:tt)*)
+        ($($cases:tt)*)
+    ) => {{
+        match $r {
+            ref _r => {
+                let $var: &$crate::Receiver<_> = unsafe {
+                    let _r: &$crate::Receiver<_> = _r;
+
+                    // Erase the lifetime so that `sel` can be dropped early even without NLL.
+                    unsafe fn unbind<'a, T>(x: &T) -> &'a T {
+                        ::std::mem::transmute(x)
+                    }
+                    unbind(_r)
+                };
+                $sel[$i] = ($var, $i, $var as *const $crate::Receiver<_> as *const u8);
+
+                $crate::crossbeam_channel_internal!(
+                    @add
+                    $sel
+                    ($($tail)*)
+                    $default
+                    ($($labels)*)
+                    ($($cases)* [$i] recv($var) -> $res => $body,)
+                )
+            }
+        }
+    }};
+    // Add a send operation to `sel`.
+    (@add
+        $sel:ident
+        (send($s:expr, $m:expr) -> $res:pat => $body:tt, $($tail:tt)*)
+        $default:tt
+        (($i:tt $var:ident) $($labels:tt)*)
+        ($($cases:tt)*)
+    ) => {{
+        match $s {
+            ref _s => {
+                let $var: &$crate::Sender<_> = unsafe {
+                    let _s: &$crate::Sender<_> = _s;
+
+                    // Erase the lifetime so that `sel` can be dropped early even without NLL.
+                    unsafe fn unbind<'a, T>(x: &T) -> &'a T {
+                        ::std::mem::transmute(x)
+                    }
+                    unbind(_s)
+                };
+                $sel[$i] = ($var, $i, $var as *const $crate::Sender<_> as *const u8);
+
+                $crate::crossbeam_channel_internal!(
+                    @add
+                    $sel
+                    ($($tail)*)
+                    $default
+                    ($($labels)*)
+                    ($($cases)* [$i] send($var, $m) -> $res => $body,)
+                )
+            }
+        }
+    }};
+
+    // Complete a receive operation.
+    (@complete
+        $sel:ident
+        $oper:ident
+        ([$i:tt] recv($r:ident) -> $res:pat => $body:tt, $($tail:tt)*)
+    ) => {{
+        if $oper.index() == $i {
+            let _res = $oper.recv($r);
+            { $sel };
+
+            let $res = _res;
+            $body
+        } else {
+            $crate::crossbeam_channel_internal! {
+                @complete
+                $sel
+                $oper
+                ($($tail)*)
+            }
+        }
+    }};
+    // Complete a send operation.
+    (@complete
+        $sel:ident
+        $oper:ident
+        ([$i:tt] send($s:ident, $m:expr) -> $res:pat => $body:tt, $($tail:tt)*)
+    ) => {{
+        if $oper.index() == $i {
+            let _res = $oper.send($s, $m);
+            { $sel };
+
+            let $res = _res;
+            $body
+        } else {
+            $crate::crossbeam_channel_internal! {
+                @complete
+                $sel
+                $oper
+                ($($tail)*)
+            }
+        }
+    }};
+    // Panic if we don't identify the selected case, but this should never happen.
+    (@complete
+        $sel:ident
+        $oper:ident
+        ()
+    ) => {{
+        unreachable!(
+            "internal error in crossbeam-channel: invalid case"
+        )
+    }};
+
+    // Catches a bug within this macro (should not happen).
+    (@$($tokens:tt)*) => {
+        compile_error!(
+            concat!(
+                "internal error in crossbeam-channel: ",
+                stringify!(@$($tokens)*),
+            )
+        )
+    };
+
+    // The entry points.
+    () => {
+        compile_error!("empty `select!` block")
+    };
+    ($($case:ident $(($($args:tt)*))* => $body:expr $(,)*)*) => {
+        $crate::crossbeam_channel_internal!(
+            @list
+            ($($case $(($($args)*))* => { $body },)*)
+            ()
+        )
+    };
+    ($($tokens:tt)*) => {
+        $crate::crossbeam_channel_internal!(
+            @list
+            ($($tokens)*)
+            ()
+        )
+    };
+}
+
+/// Selects from a set of channel operations.
+///
+/// This macro allows you to define a set of channel operations, wait until any one of them becomes
+/// ready, and finally execute it. If multiple operations are ready at the same time, a random one
+/// among them is selected.
+///
+/// It is also possible to define a `default` case that gets executed if none of the operations are
+/// ready, either right away or for a certain duration of time.
+///
+/// An operation is considered to be ready if it doesn't have to block. Note that it is ready even
+/// when it will simply return an error because the channel is disconnected.
+///
+/// The `select` macro is a convenience wrapper around [`Select`]. However, it cannot select over a
+/// dynamically created list of channel operations.
+///
+/// [`Select`]: super::Select
+///
+/// # Examples
+///
+/// Block until a send or a receive operation is selected:
+///
+/// ```
+/// use crossbeam_channel::{select, unbounded};
+///
+/// let (s1, r1) = unbounded();
+/// let (s2, r2) = unbounded();
+/// s1.send(10).unwrap();
+///
+/// // Since both operations are initially ready, a random one will be executed.
+/// select! {
+///     recv(r1) -> msg => assert_eq!(msg, Ok(10)),
+///     send(s2, 20) -> res => {
+///         assert_eq!(res, Ok(()));
+///         assert_eq!(r2.recv(), Ok(20));
+///     }
+/// }
+/// ```
+///
+/// Select from a set of operations without blocking:
+///
+/// ```
+/// use std::thread;
+/// use std::time::Duration;
+/// use crossbeam_channel::{select, unbounded};
+///
+/// let (s1, r1) = unbounded();
+/// let (s2, r2) = unbounded();
+///
+/// thread::spawn(move || {
+///     thread::sleep(Duration::from_secs(1));
+///     s1.send(10).unwrap();
+/// });
+/// thread::spawn(move || {
+///     thread::sleep(Duration::from_millis(500));
+///     s2.send(20).unwrap();
+/// });
+///
+/// // None of the operations are initially ready.
+/// select! {
+///     recv(r1) -> msg => panic!(),
+///     recv(r2) -> msg => panic!(),
+///     default => println!("not ready"),
+/// }
+/// ```
+///
+/// Select over a set of operations with a timeout:
+///
+/// ```
+/// use std::thread;
+/// use std::time::Duration;
+/// use crossbeam_channel::{select, unbounded};
+///
+/// let (s1, r1) = unbounded();
+/// let (s2, r2) = unbounded();
+///
+/// thread::spawn(move || {
+///     thread::sleep(Duration::from_secs(1));
+///     s1.send(10).unwrap();
+/// });
+/// thread::spawn(move || {
+///     thread::sleep(Duration::from_millis(500));
+///     s2.send(20).unwrap();
+/// });
+///
+/// // None of the two operations will become ready within 100 milliseconds.
+/// select! {
+///     recv(r1) -> msg => panic!(),
+///     recv(r2) -> msg => panic!(),
+///     default(Duration::from_millis(100)) => println!("timed out"),
+/// }
+/// ```
+///
+/// Optionally add a receive operation to `select!` using [`never`]:
+///
+/// ```
+/// use std::thread;
+/// use std::time::Duration;
+/// use crossbeam_channel::{select, never, unbounded};
+///
+/// let (s1, r1) = unbounded();
+/// let (s2, r2) = unbounded();
+///
+/// thread::spawn(move || {
+///     thread::sleep(Duration::from_secs(1));
+///     s1.send(10).unwrap();
+/// });
+/// thread::spawn(move || {
+///     thread::sleep(Duration::from_millis(500));
+///     s2.send(20).unwrap();
+/// });
+///
+/// // This receiver can be a `Some` or a `None`.
+/// let r2 = Some(&r2);
+///
+/// // None of the two operations will become ready within 100 milliseconds.
+/// select! {
+///     recv(r1) -> msg => panic!(),
+///     recv(r2.unwrap_or(&never())) -> msg => assert_eq!(msg, Ok(20)),
+/// }
+/// ```
+///
+/// To optionally add a timeout to `select!`, see the [example] for [`never`].
+///
+/// [`never`]: super::never
+/// [example]: super::never#examples
+#[macro_export]
+macro_rules! select {
+    ($($tokens:tt)*) => {
+        $crate::crossbeam_channel_internal!(
+            $($tokens)*
+        )
+    };
+}
diff --git a/src/utils.rs b/src/utils.rs
new file mode 100644
index 0000000..3fe171b
--- /dev/null
+++ b/src/utils.rs
@@ -0,0 +1,112 @@
+//! Miscellaneous utilities.
+
+use std::cell::{Cell, UnsafeCell};
+use std::num::Wrapping;
+use std::ops::{Deref, DerefMut};
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::thread;
+use std::time::{Duration, Instant};
+
+use crossbeam_utils::Backoff;
+
+/// Randomly shuffles a slice.
+pub fn shuffle<T>(v: &mut [T]) {
+    let len = v.len();
+    if len <= 1 {
+        return;
+    }
+
+    thread_local! {
+        static RNG: Cell<Wrapping<u32>> = Cell::new(Wrapping(1_406_868_647));
+    }
+
+    let _ = RNG.try_with(|rng| {
+        for i in 1..len {
+            // This is the 32-bit variant of Xorshift.
+            //
+            // Source: https://en.wikipedia.org/wiki/Xorshift
+            let mut x = rng.get();
+            x ^= x << 13;
+            x ^= x >> 17;
+            x ^= x << 5;
+            rng.set(x);
+
+            let x = x.0;
+            let n = i + 1;
+
+            // This is a fast alternative to `let j = x % n`.
+            //
+            // Author: Daniel Lemire
+            // Source: https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/
+            let j = ((x as u64).wrapping_mul(n as u64) >> 32) as u32 as usize;
+
+            v.swap(i, j);
+        }
+    });
+}
+
+/// Sleeps until the deadline, or forever if the deadline isn't specified.
+pub fn sleep_until(deadline: Option<Instant>) {
+    loop {
+        match deadline {
+            None => thread::sleep(Duration::from_secs(1000)),
+            Some(d) => {
+                let now = Instant::now();
+                if now >= d {
+                    break;
+                }
+                thread::sleep(d - now);
+            }
+        }
+    }
+}
+
+/// A simple spinlock.
+pub struct Spinlock<T> {
+    flag: AtomicBool,
+    value: UnsafeCell<T>,
+}
+
+impl<T> Spinlock<T> {
+    /// Returns a new spinlock initialized with `value`.
+    pub fn new(value: T) -> Spinlock<T> {
+        Spinlock {
+            flag: AtomicBool::new(false),
+            value: UnsafeCell::new(value),
+        }
+    }
+
+    /// Locks the spinlock.
+    pub fn lock(&self) -> SpinlockGuard<'_, T> {
+        let backoff = Backoff::new();
+        while self.flag.swap(true, Ordering::Acquire) {
+            backoff.snooze();
+        }
+        SpinlockGuard { parent: self }
+    }
+}
+
+/// A guard holding a spinlock locked.
+pub struct SpinlockGuard<'a, T> {
+    parent: &'a Spinlock<T>,
+}
+
+impl<T> Drop for SpinlockGuard<'_, T> {
+    fn drop(&mut self) {
+        self.parent.flag.store(false, Ordering::Release);
+    }
+}
+
+impl<T> Deref for SpinlockGuard<'_, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        unsafe { &*self.parent.value.get() }
+    }
+}
+
+impl<T> DerefMut for SpinlockGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.parent.value.get() }
+    }
+}
diff --git a/src/waker.rs b/src/waker.rs
new file mode 100644
index 0000000..3d0af26
--- /dev/null
+++ b/src/waker.rs
@@ -0,0 +1,287 @@
+//! Waking mechanism for threads blocked on channel operations.
+
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::thread::{self, ThreadId};
+
+use crate::context::Context;
+use crate::select::{Operation, Selected};
+use crate::utils::Spinlock;
+
+/// Represents a thread blocked on a specific channel operation.
+pub struct Entry {
+    /// The operation.
+    pub oper: Operation,
+
+    /// Optional packet.
+    pub packet: usize,
+
+    /// Context associated with the thread owning this operation.
+    pub cx: Context,
+}
+
+/// A queue of threads blocked on channel operations.
+///
+/// This data structure is used by threads to register blocking operations and get woken up once
+/// an operation becomes ready.
+pub struct Waker {
+    /// A list of select operations.
+    selectors: Vec<Entry>,
+
+    /// A list of operations waiting to be ready.
+    observers: Vec<Entry>,
+}
+
+impl Waker {
+    /// Creates a new `Waker`.
+    #[inline]
+    pub fn new() -> Self {
+        Waker {
+            selectors: Vec::new(),
+            observers: Vec::new(),
+        }
+    }
+
+    /// Registers a select operation.
+    #[inline]
+    pub fn register(&mut self, oper: Operation, cx: &Context) {
+        self.register_with_packet(oper, 0, cx);
+    }
+
+    /// Registers a select operation and a packet.
+    #[inline]
+    pub fn register_with_packet(&mut self, oper: Operation, packet: usize, cx: &Context) {
+        self.selectors.push(Entry {
+            oper,
+            packet,
+            cx: cx.clone(),
+        });
+    }
+
+    /// Unregisters a select operation.
+    #[inline]
+    pub fn unregister(&mut self, oper: Operation) -> Option<Entry> {
+        if let Some((i, _)) = self
+            .selectors
+            .iter()
+            .enumerate()
+            .find(|&(_, entry)| entry.oper == oper)
+        {
+            let entry = self.selectors.remove(i);
+            Some(entry)
+        } else {
+            None
+        }
+    }
+
+    /// Attempts to find another thread's entry, select the operation, and wake it up.
+    #[inline]
+    pub fn try_select(&mut self) -> Option<Entry> {
+        let mut entry = None;
+
+        if !self.selectors.is_empty() {
+            let thread_id = current_thread_id();
+
+            for i in 0..self.selectors.len() {
+                // Does the entry belong to a different thread?
+                if self.selectors[i].cx.thread_id() != thread_id {
+                    // Try selecting this operation.
+                    let sel = Selected::Operation(self.selectors[i].oper);
+                    let res = self.selectors[i].cx.try_select(sel);
+
+                    if res.is_ok() {
+                        // Provide the packet.
+                        self.selectors[i].cx.store_packet(self.selectors[i].packet);
+                        // Wake the thread up.
+                        self.selectors[i].cx.unpark();
+
+                        // Remove the entry from the queue to keep it clean and improve
+                        // performance.
+                        entry = Some(self.selectors.remove(i));
+                        break;
+                    }
+                }
+            }
+        }
+
+        entry
+    }
+
+    /// Returns `true` if there is an entry which can be selected by the current thread.
+    #[inline]
+    pub fn can_select(&self) -> bool {
+        if self.selectors.is_empty() {
+            false
+        } else {
+            let thread_id = current_thread_id();
+
+            self.selectors.iter().any(|entry| {
+                entry.cx.thread_id() != thread_id && entry.cx.selected() == Selected::Waiting
+            })
+        }
+    }
+
+    /// Registers an operation waiting to be ready.
+    #[inline]
+    pub fn watch(&mut self, oper: Operation, cx: &Context) {
+        self.observers.push(Entry {
+            oper,
+            packet: 0,
+            cx: cx.clone(),
+        });
+    }
+
+    /// Unregisters an operation waiting to be ready.
+    #[inline]
+    pub fn unwatch(&mut self, oper: Operation) {
+        self.observers.retain(|e| e.oper != oper);
+    }
+
+    /// Notifies all operations waiting to be ready.
+    #[inline]
+    pub fn notify(&mut self) {
+        for entry in self.observers.drain(..) {
+            if entry.cx.try_select(Selected::Operation(entry.oper)).is_ok() {
+                entry.cx.unpark();
+            }
+        }
+    }
+
+    /// Notifies all registered operations that the channel is disconnected.
+    #[inline]
+    pub fn disconnect(&mut self) {
+        for entry in self.selectors.iter() {
+            if entry.cx.try_select(Selected::Disconnected).is_ok() {
+                // Wake the thread up.
+                //
+                // Here we don't remove the entry from the queue. Registered threads must
+                // unregister from the waker by themselves. They might also want to recover the
+                // packet value and destroy it, if necessary.
+                entry.cx.unpark();
+            }
+        }
+
+        self.notify();
+    }
+}
+
+impl Drop for Waker {
+    #[inline]
+    fn drop(&mut self) {
+        debug_assert_eq!(self.selectors.len(), 0);
+        debug_assert_eq!(self.observers.len(), 0);
+    }
+}
+
+/// A waker that can be shared among threads without locking.
+///
+/// This is a simple wrapper around `Waker` that internally uses a mutex for synchronization.
+pub struct SyncWaker {
+    /// The inner `Waker`.
+    inner: Spinlock<Waker>,
+
+    /// `true` if the waker is empty.
+    is_empty: AtomicBool,
+}
+
+impl SyncWaker {
+    /// Creates a new `SyncWaker`.
+    #[inline]
+    pub fn new() -> Self {
+        SyncWaker {
+            inner: Spinlock::new(Waker::new()),
+            is_empty: AtomicBool::new(true),
+        }
+    }
+
+    /// Registers the current thread with an operation.
+    #[inline]
+    pub fn register(&self, oper: Operation, cx: &Context) {
+        let mut inner = self.inner.lock();
+        inner.register(oper, cx);
+        self.is_empty.store(
+            inner.selectors.is_empty() && inner.observers.is_empty(),
+            Ordering::SeqCst,
+        );
+    }
+
+    /// Unregisters an operation previously registered by the current thread.
+    #[inline]
+    pub fn unregister(&self, oper: Operation) -> Option<Entry> {
+        let mut inner = self.inner.lock();
+        let entry = inner.unregister(oper);
+        self.is_empty.store(
+            inner.selectors.is_empty() && inner.observers.is_empty(),
+            Ordering::SeqCst,
+        );
+        entry
+    }
+
+    /// Attempts to find one thread (not the current one), select its operation, and wake it up.
+    #[inline]
+    pub fn notify(&self) {
+        if !self.is_empty.load(Ordering::SeqCst) {
+            let mut inner = self.inner.lock();
+            if !self.is_empty.load(Ordering::SeqCst) {
+                inner.try_select();
+                inner.notify();
+                self.is_empty.store(
+                    inner.selectors.is_empty() && inner.observers.is_empty(),
+                    Ordering::SeqCst,
+                );
+            }
+        }
+    }
+
+    /// Registers an operation waiting to be ready.
+    #[inline]
+    pub fn watch(&self, oper: Operation, cx: &Context) {
+        let mut inner = self.inner.lock();
+        inner.watch(oper, cx);
+        self.is_empty.store(
+            inner.selectors.is_empty() && inner.observers.is_empty(),
+            Ordering::SeqCst,
+        );
+    }
+
+    /// Unregisters an operation waiting to be ready.
+    #[inline]
+    pub fn unwatch(&self, oper: Operation) {
+        let mut inner = self.inner.lock();
+        inner.unwatch(oper);
+        self.is_empty.store(
+            inner.selectors.is_empty() && inner.observers.is_empty(),
+            Ordering::SeqCst,
+        );
+    }
+
+    /// Notifies all threads that the channel is disconnected.
+    #[inline]
+    pub fn disconnect(&self) {
+        let mut inner = self.inner.lock();
+        inner.disconnect();
+        self.is_empty.store(
+            inner.selectors.is_empty() && inner.observers.is_empty(),
+            Ordering::SeqCst,
+        );
+    }
+}
+
+impl Drop for SyncWaker {
+    #[inline]
+    fn drop(&mut self) {
+        debug_assert_eq!(self.is_empty.load(Ordering::SeqCst), true);
+    }
+}
+
+/// Returns the id of the current thread.
+#[inline]
+fn current_thread_id() -> ThreadId {
+    thread_local! {
+        /// Cached thread-local id.
+        static THREAD_ID: ThreadId = thread::current().id();
+    }
+
+    THREAD_ID
+        .try_with(|id| *id)
+        .unwrap_or_else(|_| thread::current().id())
+}