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Diffstat (limited to 'third_party/rust/crossbeam-channel/src/channel.rs')
| -rw-r--r-- | third_party/rust/crossbeam-channel/src/channel.rs | 1511 |
1 files changed, 1511 insertions, 0 deletions
diff --git a/third_party/rust/crossbeam-channel/src/channel.rs b/third_party/rust/crossbeam-channel/src/channel.rs new file mode 100644 index 0000000000..800fe63527 --- /dev/null +++ b/third_party/rust/crossbeam-channel/src/channel.rs @@ -0,0 +1,1511 @@ +//! 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}; +use crate::utils; + +/// 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!`]: +/// +/// [`select!`]: crate::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"), +/// } +/// ``` +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(65) > b && b + ms(65) > 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, utils::convert_timeout_to_deadline(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_senders()), + 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(utils::convert_timeout_to_deadline(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_receivers()), + 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(crate) 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(crate) 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), + } +} |