b8ae372e48
This removes two minor OnceLock tests which test private methods. The rest of the tests should be more than enough to catch mistakes in those private methods. Also makes ReentrantLock::try_lock public. And finally it makes the mpmc tests actually run.
1242 lines
39 KiB
Rust
1242 lines
39 KiB
Rust
//! Multi-producer, single-consumer FIFO queue communication primitives.
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//!
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//! This module provides message-based communication over channels, concretely
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//! defined among three types:
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//!
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//! * [`Sender`]
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//! * [`SyncSender`]
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//! * [`Receiver`]
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//!
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//! A [`Sender`] or [`SyncSender`] is used to send data to a [`Receiver`]. Both
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//! senders are clone-able (multi-producer) such that many threads can send
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//! simultaneously to one receiver (single-consumer).
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//!
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//! These channels come in two flavors:
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//!
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//! 1. An asynchronous, infinitely buffered channel. The [`channel`] function
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//! will return a `(Sender, Receiver)` tuple where all sends will be
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//! **asynchronous** (they never block). The channel conceptually has an
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//! infinite buffer.
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//!
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//! 2. A synchronous, bounded channel. The [`sync_channel`] function will
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//! return a `(SyncSender, Receiver)` tuple where the storage for pending
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//! messages is a pre-allocated buffer of a fixed size. All sends will be
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//! **synchronous** by blocking until there is buffer space available. Note
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//! that a bound of 0 is allowed, causing the channel to become a "rendezvous"
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//! channel where each sender atomically hands off a message to a receiver.
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//!
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//! [`send`]: Sender::send
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//!
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//! ## Disconnection
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//!
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//! The send and receive operations on channels will all return a [`Result`]
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//! indicating whether the operation succeeded or not. An unsuccessful operation
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//! is normally indicative of the other half of a channel having "hung up" by
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//! being dropped in its corresponding thread.
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//!
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//! Once half of a channel has been deallocated, most operations can no longer
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//! continue to make progress, so [`Err`] will be returned. Many applications
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//! will continue to [`unwrap`] the results returned from this module,
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//! instigating a propagation of failure among threads if one unexpectedly dies.
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//!
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//! [`unwrap`]: Result::unwrap
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//!
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//! # Examples
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//!
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//! Simple usage:
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//!
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//! ```
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//! use std::thread;
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//! use std::sync::mpsc::channel;
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//!
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//! // Create a simple streaming channel
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//! let (tx, rx) = channel();
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//! thread::spawn(move || {
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//! tx.send(10).unwrap();
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//! });
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//! assert_eq!(rx.recv().unwrap(), 10);
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//! ```
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//!
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//! Shared usage:
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//!
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//! ```
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//! use std::thread;
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//! use std::sync::mpsc::channel;
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//!
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//! // Create a shared channel that can be sent along from many threads
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//! // where tx is the sending half (tx for transmission), and rx is the receiving
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//! // half (rx for receiving).
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//! let (tx, rx) = channel();
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//! for i in 0..10 {
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//! let tx = tx.clone();
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//! thread::spawn(move || {
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//! tx.send(i).unwrap();
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//! });
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//! }
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//!
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//! for _ in 0..10 {
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//! let j = rx.recv().unwrap();
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//! assert!(0 <= j && j < 10);
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//! }
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//! ```
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//!
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//! Propagating panics:
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//!
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//! ```
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//! use std::sync::mpsc::channel;
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//!
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//! // The call to recv() will return an error because the channel has already
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//! // hung up (or been deallocated)
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//! let (tx, rx) = channel::<i32>();
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//! drop(tx);
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//! assert!(rx.recv().is_err());
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//! ```
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//!
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//! Synchronous channels:
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//!
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//! ```
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//! use std::thread;
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//! use std::sync::mpsc::sync_channel;
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//!
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//! let (tx, rx) = sync_channel::<i32>(0);
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//! thread::spawn(move || {
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//! // This will wait for the parent thread to start receiving
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//! tx.send(53).unwrap();
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//! });
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//! rx.recv().unwrap();
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//! ```
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//!
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//! Unbounded receive loop:
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//!
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//! ```
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//! use std::sync::mpsc::sync_channel;
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//! use std::thread;
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//!
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//! let (tx, rx) = sync_channel(3);
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//!
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//! for _ in 0..3 {
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//! // It would be the same without thread and clone here
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//! // since there will still be one `tx` left.
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//! let tx = tx.clone();
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//! // cloned tx dropped within thread
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//! thread::spawn(move || tx.send("ok").unwrap());
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//! }
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//!
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//! // Drop the last sender to stop `rx` waiting for message.
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//! // The program will not complete if we comment this out.
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//! // **All** `tx` needs to be dropped for `rx` to have `Err`.
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//! drop(tx);
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//!
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//! // Unbounded receiver waiting for all senders to complete.
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//! while let Ok(msg) = rx.recv() {
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//! println!("{msg}");
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//! }
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//!
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//! println!("completed");
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//! ```
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#![stable(feature = "rust1", since = "1.0.0")]
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// MPSC channels are built as a wrapper around MPMC channels, which
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// were ported from the `crossbeam-channel` crate. MPMC channels are
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// not exposed publicly, but if you are curious about the implementation,
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// that's where everything is.
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use crate::sync::mpmc;
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use crate::time::{Duration, Instant};
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use crate::{error, fmt};
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/// The receiving half of Rust's [`channel`] (or [`sync_channel`]) type.
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/// This half can only be owned by one thread.
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///
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/// Messages sent to the channel can be retrieved using [`recv`].
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///
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/// [`recv`]: Receiver::recv
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///
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/// # Examples
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///
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/// ```rust
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/// use std::sync::mpsc::channel;
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/// use std::thread;
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/// use std::time::Duration;
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///
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/// let (send, recv) = channel();
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///
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/// thread::spawn(move || {
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/// send.send("Hello world!").unwrap();
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/// thread::sleep(Duration::from_secs(2)); // block for two seconds
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/// send.send("Delayed for 2 seconds").unwrap();
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/// });
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///
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/// println!("{}", recv.recv().unwrap()); // Received immediately
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/// println!("Waiting...");
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/// println!("{}", recv.recv().unwrap()); // Received after 2 seconds
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[cfg_attr(not(test), rustc_diagnostic_item = "Receiver")]
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pub struct Receiver<T> {
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inner: mpmc::Receiver<T>,
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}
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// The receiver port can be sent from place to place, so long as it
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// is not used to receive non-sendable things.
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#[stable(feature = "rust1", since = "1.0.0")]
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unsafe impl<T: Send> Send for Receiver<T> {}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T> !Sync for Receiver<T> {}
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/// An iterator over messages on a [`Receiver`], created by [`iter`].
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///
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/// This iterator will block whenever [`next`] is called,
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/// waiting for a new message, and [`None`] will be returned
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/// when the corresponding channel has hung up.
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///
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/// [`iter`]: Receiver::iter
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/// [`next`]: Iterator::next
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///
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/// # Examples
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///
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/// ```rust
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/// use std::sync::mpsc::channel;
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/// use std::thread;
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///
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/// let (send, recv) = channel();
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///
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/// thread::spawn(move || {
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/// send.send(1u8).unwrap();
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/// send.send(2u8).unwrap();
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/// send.send(3u8).unwrap();
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/// });
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///
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/// for x in recv.iter() {
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/// println!("Got: {x}");
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/// }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[derive(Debug)]
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pub struct Iter<'a, T: 'a> {
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rx: &'a Receiver<T>,
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}
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/// An iterator that attempts to yield all pending values for a [`Receiver`],
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/// created by [`try_iter`].
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///
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/// [`None`] will be returned when there are no pending values remaining or
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/// if the corresponding channel has hung up.
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///
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/// This iterator will never block the caller in order to wait for data to
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/// become available. Instead, it will return [`None`].
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///
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/// [`try_iter`]: Receiver::try_iter
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///
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/// # Examples
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///
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/// ```rust
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/// use std::sync::mpsc::channel;
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/// use std::thread;
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/// use std::time::Duration;
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///
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/// let (sender, receiver) = channel();
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///
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/// // Nothing is in the buffer yet
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/// assert!(receiver.try_iter().next().is_none());
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/// println!("Nothing in the buffer...");
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///
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/// thread::spawn(move || {
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/// sender.send(1).unwrap();
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/// sender.send(2).unwrap();
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/// sender.send(3).unwrap();
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/// });
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///
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/// println!("Going to sleep...");
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/// thread::sleep(Duration::from_secs(2)); // block for two seconds
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///
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/// for x in receiver.try_iter() {
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/// println!("Got: {x}");
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/// }
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/// ```
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#[stable(feature = "receiver_try_iter", since = "1.15.0")]
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#[derive(Debug)]
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pub struct TryIter<'a, T: 'a> {
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rx: &'a Receiver<T>,
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}
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/// An owning iterator over messages on a [`Receiver`],
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/// created by [`into_iter`].
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///
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/// This iterator will block whenever [`next`]
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/// is called, waiting for a new message, and [`None`] will be
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/// returned if the corresponding channel has hung up.
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///
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/// [`into_iter`]: Receiver::into_iter
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/// [`next`]: Iterator::next
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///
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/// # Examples
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///
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/// ```rust
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/// use std::sync::mpsc::channel;
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/// use std::thread;
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///
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/// let (send, recv) = channel();
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///
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/// thread::spawn(move || {
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/// send.send(1u8).unwrap();
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/// send.send(2u8).unwrap();
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/// send.send(3u8).unwrap();
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/// });
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///
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/// for x in recv.into_iter() {
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/// println!("Got: {x}");
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/// }
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/// ```
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#[stable(feature = "receiver_into_iter", since = "1.1.0")]
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#[derive(Debug)]
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pub struct IntoIter<T> {
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rx: Receiver<T>,
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}
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/// The sending-half of Rust's asynchronous [`channel`] type.
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///
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/// Messages can be sent through this channel with [`send`].
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///
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/// Note: all senders (the original and its clones) need to be dropped for the receiver
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/// to stop blocking to receive messages with [`Receiver::recv`].
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///
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/// [`send`]: Sender::send
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///
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/// # Examples
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///
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/// ```rust
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/// use std::sync::mpsc::channel;
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/// use std::thread;
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///
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/// let (sender, receiver) = channel();
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/// let sender2 = sender.clone();
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///
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/// // First thread owns sender
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/// thread::spawn(move || {
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/// sender.send(1).unwrap();
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/// });
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///
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/// // Second thread owns sender2
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/// thread::spawn(move || {
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/// sender2.send(2).unwrap();
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/// });
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///
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/// let msg = receiver.recv().unwrap();
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/// let msg2 = receiver.recv().unwrap();
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///
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/// assert_eq!(3, msg + msg2);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct Sender<T> {
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inner: mpmc::Sender<T>,
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}
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// The send port can be sent from place to place, so long as it
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// is not used to send non-sendable things.
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#[stable(feature = "rust1", since = "1.0.0")]
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unsafe impl<T: Send> Send for Sender<T> {}
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#[stable(feature = "mpsc_sender_sync", since = "1.72.0")]
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unsafe impl<T: Send> Sync for Sender<T> {}
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/// The sending-half of Rust's synchronous [`sync_channel`] type.
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///
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/// Messages can be sent through this channel with [`send`] or [`try_send`].
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///
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/// [`send`] will block if there is no space in the internal buffer.
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///
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/// [`send`]: SyncSender::send
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/// [`try_send`]: SyncSender::try_send
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///
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/// # Examples
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///
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/// ```rust
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/// use std::sync::mpsc::sync_channel;
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/// use std::thread;
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///
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/// // Create a sync_channel with buffer size 2
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/// let (sync_sender, receiver) = sync_channel(2);
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/// let sync_sender2 = sync_sender.clone();
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///
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/// // First thread owns sync_sender
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/// thread::spawn(move || {
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/// sync_sender.send(1).unwrap();
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/// sync_sender.send(2).unwrap();
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/// });
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///
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/// // Second thread owns sync_sender2
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/// thread::spawn(move || {
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/// sync_sender2.send(3).unwrap();
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/// // thread will now block since the buffer is full
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/// println!("Thread unblocked!");
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/// });
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///
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/// let mut msg;
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///
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/// msg = receiver.recv().unwrap();
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/// println!("message {msg} received");
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///
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/// // "Thread unblocked!" will be printed now
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///
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/// msg = receiver.recv().unwrap();
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/// println!("message {msg} received");
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///
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/// msg = receiver.recv().unwrap();
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///
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/// println!("message {msg} received");
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct SyncSender<T> {
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inner: mpmc::Sender<T>,
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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unsafe impl<T: Send> Send for SyncSender<T> {}
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/// An error returned from the [`Sender::send`] or [`SyncSender::send`]
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/// function on **channel**s.
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///
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/// A **send** operation can only fail if the receiving end of a channel is
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/// disconnected, implying that the data could never be received. The error
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/// contains the data being sent as a payload so it can be recovered.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[derive(PartialEq, Eq, Clone, Copy)]
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pub struct SendError<T>(#[stable(feature = "rust1", since = "1.0.0")] pub T);
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/// An error returned from the [`recv`] function on a [`Receiver`].
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///
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/// The [`recv`] operation can only fail if the sending half of a
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/// [`channel`] (or [`sync_channel`]) is disconnected, implying that no further
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/// messages will ever be received.
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///
|
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/// [`recv`]: Receiver::recv
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#[derive(PartialEq, Eq, Clone, Copy, Debug)]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct RecvError;
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|
|
/// This enumeration is the list of the possible reasons that [`try_recv`] could
|
|
/// not return data when called. This can occur with both a [`channel`] and
|
|
/// a [`sync_channel`].
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///
|
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/// [`try_recv`]: Receiver::try_recv
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#[derive(PartialEq, Eq, Clone, Copy, Debug)]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
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pub enum TryRecvError {
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/// This **channel** is currently empty, but the **Sender**(s) have not yet
|
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/// disconnected, so data may yet become available.
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#[stable(feature = "rust1", since = "1.0.0")]
|
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Empty,
|
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|
|
/// The **channel**'s sending half has become disconnected, and there will
|
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/// never be any more data received on it.
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
Disconnected,
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|
}
|
|
|
|
/// This enumeration is the list of possible errors that made [`recv_timeout`]
|
|
/// unable to return data when called. This can occur with both a [`channel`] and
|
|
/// a [`sync_channel`].
|
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///
|
|
/// [`recv_timeout`]: Receiver::recv_timeout
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|
#[derive(PartialEq, Eq, Clone, Copy, Debug)]
|
|
#[stable(feature = "mpsc_recv_timeout", since = "1.12.0")]
|
|
pub enum RecvTimeoutError {
|
|
/// This **channel** is currently empty, but the **Sender**(s) have not yet
|
|
/// disconnected, so data may yet become available.
|
|
#[stable(feature = "mpsc_recv_timeout", since = "1.12.0")]
|
|
Timeout,
|
|
/// The **channel**'s sending half has become disconnected, and there will
|
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/// never be any more data received on it.
|
|
#[stable(feature = "mpsc_recv_timeout", since = "1.12.0")]
|
|
Disconnected,
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|
}
|
|
|
|
/// This enumeration is the list of the possible error outcomes for the
|
|
/// [`try_send`] method.
|
|
///
|
|
/// [`try_send`]: SyncSender::try_send
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|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[derive(PartialEq, Eq, Clone, Copy)]
|
|
pub enum TrySendError<T> {
|
|
/// The data could not be sent on the [`sync_channel`] because it would require that
|
|
/// the callee block to send the data.
|
|
///
|
|
/// If this is a buffered channel, then the buffer is full at this time. If
|
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/// this is not a buffered channel, then there is no [`Receiver`] available to
|
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/// acquire the data.
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
Full(#[stable(feature = "rust1", since = "1.0.0")] T),
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|
|
/// This [`sync_channel`]'s receiving half has disconnected, so the data could not be
|
|
/// sent. The data is returned back to the callee in this case.
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
Disconnected(#[stable(feature = "rust1", since = "1.0.0")] T),
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}
|
|
|
|
/// Creates a new asynchronous channel, returning the sender/receiver halves.
|
|
///
|
|
/// All data sent on the [`Sender`] will become available on the [`Receiver`] in
|
|
/// the same order as it was sent, and no [`send`] will block the calling thread
|
|
/// (this channel has an "infinite buffer", unlike [`sync_channel`], which will
|
|
/// block after its buffer limit is reached). [`recv`] will block until a message
|
|
/// is available while there is at least one [`Sender`] alive (including clones).
|
|
///
|
|
/// The [`Sender`] can be cloned to [`send`] to the same channel multiple times, but
|
|
/// only one [`Receiver`] is supported.
|
|
///
|
|
/// If the [`Receiver`] is disconnected while trying to [`send`] with the
|
|
/// [`Sender`], the [`send`] method will return a [`SendError`]. Similarly, if the
|
|
/// [`Sender`] is disconnected while trying to [`recv`], the [`recv`] method will
|
|
/// return a [`RecvError`].
|
|
///
|
|
/// [`send`]: Sender::send
|
|
/// [`recv`]: Receiver::recv
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::sync::mpsc::channel;
|
|
/// use std::thread;
|
|
///
|
|
/// let (sender, receiver) = channel();
|
|
///
|
|
/// // Spawn off an expensive computation
|
|
/// thread::spawn(move || {
|
|
/// # fn expensive_computation() {}
|
|
/// sender.send(expensive_computation()).unwrap();
|
|
/// });
|
|
///
|
|
/// // Do some useful work for awhile
|
|
///
|
|
/// // Let's see what that answer was
|
|
/// println!("{:?}", receiver.recv().unwrap());
|
|
/// ```
|
|
#[must_use]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn channel<T>() -> (Sender<T>, Receiver<T>) {
|
|
let (tx, rx) = mpmc::channel();
|
|
(Sender { inner: tx }, Receiver { inner: rx })
|
|
}
|
|
|
|
/// Creates a new synchronous, bounded channel.
|
|
///
|
|
/// All data sent on the [`SyncSender`] will become available on the [`Receiver`]
|
|
/// in the same order as it was sent. Like asynchronous [`channel`]s, the
|
|
/// [`Receiver`] will block until a message becomes available. `sync_channel`
|
|
/// differs greatly in the semantics of the sender, however.
|
|
///
|
|
/// This channel has an internal buffer on which messages will be queued.
|
|
/// `bound` specifies the buffer size. When the internal buffer becomes full,
|
|
/// future sends will *block* waiting for the buffer to open up. Note that a
|
|
/// buffer size of 0 is valid, in which case this becomes "rendezvous channel"
|
|
/// where each [`send`] will not return until a [`recv`] is paired with it.
|
|
///
|
|
/// The [`SyncSender`] can be cloned to [`send`] to the same channel multiple
|
|
/// times, but only one [`Receiver`] is supported.
|
|
///
|
|
/// Like asynchronous channels, if the [`Receiver`] is disconnected while trying
|
|
/// to [`send`] with the [`SyncSender`], the [`send`] method will return a
|
|
/// [`SendError`]. Similarly, If the [`SyncSender`] is disconnected while trying
|
|
/// to [`recv`], the [`recv`] method will return a [`RecvError`].
|
|
///
|
|
/// [`send`]: SyncSender::send
|
|
/// [`recv`]: Receiver::recv
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::sync::mpsc::sync_channel;
|
|
/// use std::thread;
|
|
///
|
|
/// let (sender, receiver) = sync_channel(1);
|
|
///
|
|
/// // this returns immediately
|
|
/// sender.send(1).unwrap();
|
|
///
|
|
/// thread::spawn(move || {
|
|
/// // this will block until the previous message has been received
|
|
/// sender.send(2).unwrap();
|
|
/// });
|
|
///
|
|
/// assert_eq!(receiver.recv().unwrap(), 1);
|
|
/// assert_eq!(receiver.recv().unwrap(), 2);
|
|
/// ```
|
|
#[must_use]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn sync_channel<T>(bound: usize) -> (SyncSender<T>, Receiver<T>) {
|
|
let (tx, rx) = mpmc::sync_channel(bound);
|
|
(SyncSender { inner: tx }, Receiver { inner: rx })
|
|
}
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
// Sender
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
|
|
impl<T> Sender<T> {
|
|
/// Attempts to send a value on this channel, returning it back if it could
|
|
/// not be sent.
|
|
///
|
|
/// A successful send occurs when it is determined that the other end of
|
|
/// the channel has not hung up already. An unsuccessful send would be one
|
|
/// where the corresponding receiver has already been deallocated. Note
|
|
/// that a return value of [`Err`] means that the data will never be
|
|
/// received, but a return value of [`Ok`] does *not* mean that the data
|
|
/// will be received. It is possible for the corresponding receiver to
|
|
/// hang up immediately after this function returns [`Ok`].
|
|
///
|
|
/// This method will never block the current thread.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::sync::mpsc::channel;
|
|
///
|
|
/// let (tx, rx) = channel();
|
|
///
|
|
/// // This send is always successful
|
|
/// tx.send(1).unwrap();
|
|
///
|
|
/// // This send will fail because the receiver is gone
|
|
/// drop(rx);
|
|
/// assert_eq!(tx.send(1).unwrap_err().0, 1);
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn send(&self, t: T) -> Result<(), SendError<T>> {
|
|
self.inner.send(t)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T> Clone for Sender<T> {
|
|
/// Clone a sender to send to other threads.
|
|
///
|
|
/// Note, be aware of the lifetime of the sender because all senders
|
|
/// (including the original) need to be dropped in order for
|
|
/// [`Receiver::recv`] to stop blocking.
|
|
fn clone(&self) -> Sender<T> {
|
|
Sender { inner: self.inner.clone() }
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "mpsc_debug", since = "1.8.0")]
|
|
impl<T> fmt::Debug for Sender<T> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
f.debug_struct("Sender").finish_non_exhaustive()
|
|
}
|
|
}
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
// SyncSender
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
|
|
impl<T> SyncSender<T> {
|
|
/// Sends a value on this synchronous channel.
|
|
///
|
|
/// This function will *block* until space in the internal buffer becomes
|
|
/// available or a receiver is available to hand off the message to.
|
|
///
|
|
/// Note that a successful send does *not* guarantee that the receiver will
|
|
/// ever see the data if there is a buffer on this channel. Items may be
|
|
/// enqueued in the internal buffer for the receiver to receive at a later
|
|
/// time. If the buffer size is 0, however, the channel becomes a rendezvous
|
|
/// channel and it guarantees that the receiver has indeed received
|
|
/// the data if this function returns success.
|
|
///
|
|
/// This function will never panic, but it may return [`Err`] if the
|
|
/// [`Receiver`] has disconnected and is no longer able to receive
|
|
/// information.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// use std::sync::mpsc::sync_channel;
|
|
/// use std::thread;
|
|
///
|
|
/// // Create a rendezvous sync_channel with buffer size 0
|
|
/// let (sync_sender, receiver) = sync_channel(0);
|
|
///
|
|
/// thread::spawn(move || {
|
|
/// println!("sending message...");
|
|
/// sync_sender.send(1).unwrap();
|
|
/// // Thread is now blocked until the message is received
|
|
///
|
|
/// println!("...message received!");
|
|
/// });
|
|
///
|
|
/// let msg = receiver.recv().unwrap();
|
|
/// assert_eq!(1, msg);
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn send(&self, t: T) -> Result<(), SendError<T>> {
|
|
self.inner.send(t)
|
|
}
|
|
|
|
/// Attempts to send a value on this channel without blocking.
|
|
///
|
|
/// This method differs from [`send`] by returning immediately if the
|
|
/// channel's buffer is full or no receiver is waiting to acquire some
|
|
/// data. Compared with [`send`], this function has two failure cases
|
|
/// instead of one (one for disconnection, one for a full buffer).
|
|
///
|
|
/// See [`send`] for notes about guarantees of whether the
|
|
/// receiver has received the data or not if this function is successful.
|
|
///
|
|
/// [`send`]: Self::send
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// use std::sync::mpsc::sync_channel;
|
|
/// use std::thread;
|
|
///
|
|
/// // Create a sync_channel with buffer size 1
|
|
/// let (sync_sender, receiver) = sync_channel(1);
|
|
/// let sync_sender2 = sync_sender.clone();
|
|
///
|
|
/// // First thread owns sync_sender
|
|
/// thread::spawn(move || {
|
|
/// sync_sender.send(1).unwrap();
|
|
/// sync_sender.send(2).unwrap();
|
|
/// // Thread blocked
|
|
/// });
|
|
///
|
|
/// // Second thread owns sync_sender2
|
|
/// thread::spawn(move || {
|
|
/// // This will return an error and send
|
|
/// // no message if the buffer is full
|
|
/// let _ = sync_sender2.try_send(3);
|
|
/// });
|
|
///
|
|
/// let mut msg;
|
|
/// msg = receiver.recv().unwrap();
|
|
/// println!("message {msg} received");
|
|
///
|
|
/// msg = receiver.recv().unwrap();
|
|
/// println!("message {msg} received");
|
|
///
|
|
/// // Third message may have never been sent
|
|
/// match receiver.try_recv() {
|
|
/// Ok(msg) => println!("message {msg} received"),
|
|
/// Err(_) => println!("the third message was never sent"),
|
|
/// }
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn try_send(&self, t: T) -> Result<(), TrySendError<T>> {
|
|
self.inner.try_send(t)
|
|
}
|
|
|
|
// Attempts to send for a value on this receiver, returning an error if the
|
|
// corresponding channel has hung up, or if it waits more than `timeout`.
|
|
//
|
|
// This method is currently only used for tests.
|
|
#[unstable(issue = "none", feature = "std_internals")]
|
|
#[doc(hidden)]
|
|
pub fn send_timeout(&self, t: T, timeout: Duration) -> Result<(), mpmc::SendTimeoutError<T>> {
|
|
self.inner.send_timeout(t, timeout)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T> Clone for SyncSender<T> {
|
|
fn clone(&self) -> SyncSender<T> {
|
|
SyncSender { inner: self.inner.clone() }
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "mpsc_debug", since = "1.8.0")]
|
|
impl<T> fmt::Debug for SyncSender<T> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
f.debug_struct("SyncSender").finish_non_exhaustive()
|
|
}
|
|
}
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
// Receiver
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
|
|
impl<T> Receiver<T> {
|
|
/// Attempts to return a pending value on this receiver without blocking.
|
|
///
|
|
/// This method will never block the caller in order to wait for data to
|
|
/// become available. Instead, this will always return immediately with a
|
|
/// possible option of pending data on the channel.
|
|
///
|
|
/// This is useful for a flavor of "optimistic check" before deciding to
|
|
/// block on a receiver.
|
|
///
|
|
/// Compared with [`recv`], this function has two failure cases instead of one
|
|
/// (one for disconnection, one for an empty buffer).
|
|
///
|
|
/// [`recv`]: Self::recv
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// use std::sync::mpsc::{Receiver, channel};
|
|
///
|
|
/// let (_, receiver): (_, Receiver<i32>) = channel();
|
|
///
|
|
/// assert!(receiver.try_recv().is_err());
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn try_recv(&self) -> Result<T, TryRecvError> {
|
|
self.inner.try_recv()
|
|
}
|
|
|
|
/// Attempts to wait for a value on this receiver, returning an error if the
|
|
/// corresponding channel has hung up.
|
|
///
|
|
/// This function will always block the current thread if there is no data
|
|
/// available and it's possible for more data to be sent (at least one sender
|
|
/// still exists). Once a message is sent to the corresponding [`Sender`]
|
|
/// (or [`SyncSender`]), this receiver will wake up and return that
|
|
/// message.
|
|
///
|
|
/// If the corresponding [`Sender`] has disconnected, or it disconnects while
|
|
/// this call is blocking, this call will wake up and return [`Err`] to
|
|
/// indicate that no more messages can ever be received on this channel.
|
|
/// However, since channels are buffered, messages sent before the disconnect
|
|
/// will still be properly received.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::sync::mpsc;
|
|
/// use std::thread;
|
|
///
|
|
/// let (send, recv) = mpsc::channel();
|
|
/// let handle = thread::spawn(move || {
|
|
/// send.send(1u8).unwrap();
|
|
/// });
|
|
///
|
|
/// handle.join().unwrap();
|
|
///
|
|
/// assert_eq!(Ok(1), recv.recv());
|
|
/// ```
|
|
///
|
|
/// Buffering behavior:
|
|
///
|
|
/// ```
|
|
/// use std::sync::mpsc;
|
|
/// use std::thread;
|
|
/// use std::sync::mpsc::RecvError;
|
|
///
|
|
/// let (send, recv) = mpsc::channel();
|
|
/// let handle = thread::spawn(move || {
|
|
/// send.send(1u8).unwrap();
|
|
/// send.send(2).unwrap();
|
|
/// send.send(3).unwrap();
|
|
/// drop(send);
|
|
/// });
|
|
///
|
|
/// // wait for the thread to join so we ensure the sender is dropped
|
|
/// handle.join().unwrap();
|
|
///
|
|
/// assert_eq!(Ok(1), recv.recv());
|
|
/// assert_eq!(Ok(2), recv.recv());
|
|
/// assert_eq!(Ok(3), recv.recv());
|
|
/// assert_eq!(Err(RecvError), recv.recv());
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn recv(&self) -> Result<T, RecvError> {
|
|
self.inner.recv()
|
|
}
|
|
|
|
/// Attempts to wait for a value on this receiver, returning an error if the
|
|
/// corresponding channel has hung up, or if it waits more than `timeout`.
|
|
///
|
|
/// This function will always block the current thread if there is no data
|
|
/// available and it's possible for more data to be sent (at least one sender
|
|
/// still exists). Once a message is sent to the corresponding [`Sender`]
|
|
/// (or [`SyncSender`]), this receiver will wake up and return that
|
|
/// message.
|
|
///
|
|
/// If the corresponding [`Sender`] has disconnected, or it disconnects while
|
|
/// this call is blocking, this call will wake up and return [`Err`] to
|
|
/// indicate that no more messages can ever be received on this channel.
|
|
/// However, since channels are buffered, messages sent before the disconnect
|
|
/// will still be properly received.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Successfully receiving value before encountering timeout:
|
|
///
|
|
/// ```no_run
|
|
/// use std::thread;
|
|
/// use std::time::Duration;
|
|
/// use std::sync::mpsc;
|
|
///
|
|
/// let (send, recv) = mpsc::channel();
|
|
///
|
|
/// thread::spawn(move || {
|
|
/// send.send('a').unwrap();
|
|
/// });
|
|
///
|
|
/// assert_eq!(
|
|
/// recv.recv_timeout(Duration::from_millis(400)),
|
|
/// Ok('a')
|
|
/// );
|
|
/// ```
|
|
///
|
|
/// Receiving an error upon reaching timeout:
|
|
///
|
|
/// ```no_run
|
|
/// use std::thread;
|
|
/// use std::time::Duration;
|
|
/// use std::sync::mpsc;
|
|
///
|
|
/// let (send, recv) = mpsc::channel();
|
|
///
|
|
/// thread::spawn(move || {
|
|
/// thread::sleep(Duration::from_millis(800));
|
|
/// send.send('a').unwrap();
|
|
/// });
|
|
///
|
|
/// assert_eq!(
|
|
/// recv.recv_timeout(Duration::from_millis(400)),
|
|
/// Err(mpsc::RecvTimeoutError::Timeout)
|
|
/// );
|
|
/// ```
|
|
#[stable(feature = "mpsc_recv_timeout", since = "1.12.0")]
|
|
pub fn recv_timeout(&self, timeout: Duration) -> Result<T, RecvTimeoutError> {
|
|
self.inner.recv_timeout(timeout)
|
|
}
|
|
|
|
/// Attempts to wait for a value on this receiver, returning an error if the
|
|
/// corresponding channel has hung up, or if `deadline` is reached.
|
|
///
|
|
/// This function will always block the current thread if there is no data
|
|
/// available and it's possible for more data to be sent. Once a message is
|
|
/// sent to the corresponding [`Sender`] (or [`SyncSender`]), then this
|
|
/// receiver will wake up and return that message.
|
|
///
|
|
/// If the corresponding [`Sender`] has disconnected, or it disconnects while
|
|
/// this call is blocking, this call will wake up and return [`Err`] to
|
|
/// indicate that no more messages can ever be received on this channel.
|
|
/// However, since channels are buffered, messages sent before the disconnect
|
|
/// will still be properly received.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Successfully receiving value before reaching deadline:
|
|
///
|
|
/// ```no_run
|
|
/// #![feature(deadline_api)]
|
|
/// use std::thread;
|
|
/// use std::time::{Duration, Instant};
|
|
/// use std::sync::mpsc;
|
|
///
|
|
/// let (send, recv) = mpsc::channel();
|
|
///
|
|
/// thread::spawn(move || {
|
|
/// send.send('a').unwrap();
|
|
/// });
|
|
///
|
|
/// assert_eq!(
|
|
/// recv.recv_deadline(Instant::now() + Duration::from_millis(400)),
|
|
/// Ok('a')
|
|
/// );
|
|
/// ```
|
|
///
|
|
/// Receiving an error upon reaching deadline:
|
|
///
|
|
/// ```no_run
|
|
/// #![feature(deadline_api)]
|
|
/// use std::thread;
|
|
/// use std::time::{Duration, Instant};
|
|
/// use std::sync::mpsc;
|
|
///
|
|
/// let (send, recv) = mpsc::channel();
|
|
///
|
|
/// thread::spawn(move || {
|
|
/// thread::sleep(Duration::from_millis(800));
|
|
/// send.send('a').unwrap();
|
|
/// });
|
|
///
|
|
/// assert_eq!(
|
|
/// recv.recv_deadline(Instant::now() + Duration::from_millis(400)),
|
|
/// Err(mpsc::RecvTimeoutError::Timeout)
|
|
/// );
|
|
/// ```
|
|
#[unstable(feature = "deadline_api", issue = "46316")]
|
|
pub fn recv_deadline(&self, deadline: Instant) -> Result<T, RecvTimeoutError> {
|
|
self.inner.recv_deadline(deadline)
|
|
}
|
|
|
|
/// Returns an iterator that will block waiting for messages, but never
|
|
/// [`panic!`]. It will return [`None`] when the channel has hung up.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// use std::sync::mpsc::channel;
|
|
/// use std::thread;
|
|
///
|
|
/// let (send, recv) = channel();
|
|
///
|
|
/// thread::spawn(move || {
|
|
/// send.send(1).unwrap();
|
|
/// send.send(2).unwrap();
|
|
/// send.send(3).unwrap();
|
|
/// });
|
|
///
|
|
/// let mut iter = recv.iter();
|
|
/// assert_eq!(iter.next(), Some(1));
|
|
/// assert_eq!(iter.next(), Some(2));
|
|
/// assert_eq!(iter.next(), Some(3));
|
|
/// assert_eq!(iter.next(), None);
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
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pub fn iter(&self) -> Iter<'_, T> {
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Iter { rx: self }
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}
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/// Returns an iterator that will attempt to yield all pending values.
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/// It will return `None` if there are no more pending values or if the
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/// channel has hung up. The iterator will never [`panic!`] or block the
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/// user by waiting for values.
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///
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/// # Examples
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///
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/// ```no_run
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/// use std::sync::mpsc::channel;
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/// use std::thread;
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/// use std::time::Duration;
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///
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/// let (sender, receiver) = channel();
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///
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/// // nothing is in the buffer yet
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/// assert!(receiver.try_iter().next().is_none());
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///
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/// thread::spawn(move || {
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/// thread::sleep(Duration::from_secs(1));
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/// sender.send(1).unwrap();
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/// sender.send(2).unwrap();
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/// sender.send(3).unwrap();
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/// });
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///
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/// // nothing is in the buffer yet
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/// assert!(receiver.try_iter().next().is_none());
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///
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/// // block for two seconds
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/// thread::sleep(Duration::from_secs(2));
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///
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/// let mut iter = receiver.try_iter();
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/// assert_eq!(iter.next(), Some(1));
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/// assert_eq!(iter.next(), Some(2));
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/// assert_eq!(iter.next(), Some(3));
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/// assert_eq!(iter.next(), None);
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/// ```
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#[stable(feature = "receiver_try_iter", since = "1.15.0")]
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pub fn try_iter(&self) -> TryIter<'_, T> {
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TryIter { rx: self }
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<'a, T> Iterator for Iter<'a, T> {
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type Item = T;
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fn next(&mut self) -> Option<T> {
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self.rx.recv().ok()
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}
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}
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#[stable(feature = "receiver_try_iter", since = "1.15.0")]
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impl<'a, T> Iterator for TryIter<'a, T> {
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type Item = T;
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fn next(&mut self) -> Option<T> {
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self.rx.try_recv().ok()
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}
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}
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#[stable(feature = "receiver_into_iter", since = "1.1.0")]
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impl<'a, T> IntoIterator for &'a Receiver<T> {
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type Item = T;
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type IntoIter = Iter<'a, T>;
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fn into_iter(self) -> Iter<'a, T> {
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self.iter()
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}
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}
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#[stable(feature = "receiver_into_iter", since = "1.1.0")]
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impl<T> Iterator for IntoIter<T> {
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type Item = T;
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fn next(&mut self) -> Option<T> {
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self.rx.recv().ok()
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}
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}
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#[stable(feature = "receiver_into_iter", since = "1.1.0")]
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impl<T> IntoIterator for Receiver<T> {
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type Item = T;
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type IntoIter = IntoIter<T>;
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|
|
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fn into_iter(self) -> IntoIter<T> {
|
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IntoIter { rx: self }
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}
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}
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|
|
#[stable(feature = "mpsc_debug", since = "1.8.0")]
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impl<T> fmt::Debug for Receiver<T> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("Receiver").finish_non_exhaustive()
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|
}
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}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
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|
impl<T> fmt::Debug for SendError<T> {
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|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
f.debug_struct("SendError").finish_non_exhaustive()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
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|
impl<T> fmt::Display for SendError<T> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
"sending on a closed channel".fmt(f)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T> error::Error for SendError<T> {
|
|
#[allow(deprecated)]
|
|
fn description(&self) -> &str {
|
|
"sending on a closed channel"
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
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|
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),
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
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 closed channel".fmt(f),
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T> error::Error for TrySendError<T> {
|
|
#[allow(deprecated)]
|
|
fn description(&self) -> &str {
|
|
match *self {
|
|
TrySendError::Full(..) => "sending on a full channel",
|
|
TrySendError::Disconnected(..) => "sending on a closed channel",
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "mpsc_error_conversions", since = "1.24.0")]
|
|
impl<T> From<SendError<T>> for TrySendError<T> {
|
|
/// Converts a `SendError<T>` into a `TrySendError<T>`.
|
|
///
|
|
/// This conversion always returns a `TrySendError::Disconnected` containing the data in the `SendError<T>`.
|
|
///
|
|
/// No data is allocated on the heap.
|
|
fn from(err: SendError<T>) -> TrySendError<T> {
|
|
match err {
|
|
SendError(t) => TrySendError::Disconnected(t),
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl fmt::Display for RecvError {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
"receiving on a closed channel".fmt(f)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl error::Error for RecvError {
|
|
#[allow(deprecated)]
|
|
fn description(&self) -> &str {
|
|
"receiving on a closed channel"
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
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 a closed channel".fmt(f),
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl error::Error for TryRecvError {
|
|
#[allow(deprecated)]
|
|
fn description(&self) -> &str {
|
|
match *self {
|
|
TryRecvError::Empty => "receiving on an empty channel",
|
|
TryRecvError::Disconnected => "receiving on a closed channel",
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "mpsc_error_conversions", since = "1.24.0")]
|
|
impl From<RecvError> for TryRecvError {
|
|
/// Converts a `RecvError` into a `TryRecvError`.
|
|
///
|
|
/// This conversion always returns `TryRecvError::Disconnected`.
|
|
///
|
|
/// No data is allocated on the heap.
|
|
fn from(err: RecvError) -> TryRecvError {
|
|
match err {
|
|
RecvError => TryRecvError::Disconnected,
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "mpsc_recv_timeout_error", since = "1.15.0")]
|
|
impl fmt::Display for RecvTimeoutError {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
match *self {
|
|
RecvTimeoutError::Timeout => "timed out waiting on channel".fmt(f),
|
|
RecvTimeoutError::Disconnected => "channel is empty and sending half is closed".fmt(f),
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "mpsc_recv_timeout_error", since = "1.15.0")]
|
|
impl error::Error for RecvTimeoutError {
|
|
#[allow(deprecated)]
|
|
fn description(&self) -> &str {
|
|
match *self {
|
|
RecvTimeoutError::Timeout => "timed out waiting on channel",
|
|
RecvTimeoutError::Disconnected => "channel is empty and sending half is closed",
|
|
}
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "mpsc_error_conversions", since = "1.24.0")]
|
|
impl From<RecvError> for RecvTimeoutError {
|
|
/// Converts a `RecvError` into a `RecvTimeoutError`.
|
|
///
|
|
/// This conversion always returns `RecvTimeoutError::Disconnected`.
|
|
///
|
|
/// No data is allocated on the heap.
|
|
fn from(err: RecvError) -> RecvTimeoutError {
|
|
match err {
|
|
RecvError => RecvTimeoutError::Disconnected,
|
|
}
|
|
}
|
|
}
|