Rust by Example

Channels

Rust provides asynchronous channels for communication between threads. Channels allow a unidirectional flow of information between two end-points: the Sender and the Receiver.

use std::sync::mpsc::{Sender, Receiver};

use std::sync::mpsc;

use std::thread;

static NTHREADS: i32 = 3;

fn main() {

// Channels have two endpoints: the `Sender` and the `Receiver`,

// where `T` is the type of the message to be transferred

// (type annotation is superfluous)

let (tx, rx): (Sender, Receiver) = mpsc::channel();

let mut children = Vec::new();

for id in 0..NTHREADS {

// The sender endpoint can be copied

let thread_tx = tx.clone();

// Each thread will send its id via the channel

let child = thread::spawn(move || {

// The thread takes ownership over `thread_tx`

// Each thread queues a message in the channel

thread_tx.send(id).unwrap();

// Sending is a non-blocking operation, the thread will continue

// immediately after sending its message

println!("thread {} finished", id);

});

children.push(child);

}

// Here, all the messages are collected

let mut ids = Vec::with_capacity(NTHREADS as usize);

for _ in 0..NTHREADS {

// The `recv` method picks a message from the channel

// `recv` will block the current thread if there are no messages available

ids.push(rx.recv());

}

// Wait for the threads to complete any remaining work

for child in children {

child.join().expect("oops! the child thread panicked");

}

// Show the order in which the messages were sent

println!("{:?}", ids);

}

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