Module mpmc

Multi-producer, multi-consumer FIFO queue communication primitives.

This module provides message-based communication over channels, concretely defined by two types:

Senders are used to send data to a set of Receivers where each item sent is delivered to (at most) one receiver. Both sender and receiver are cloneable (multi-producer) such that many threads can send simultaneously to receivers (multi-consumer).

These channels come in two flavors:

  1. An asynchronous, infinitely buffered channel. The channel function will return a (Sender, Receiver) tuple where all sends will be asynchronous (they never block). The channel conceptually has an infinite buffer.

  2. A synchronous, bounded channel. The sync_channel function will return a (Sender, Receiver) tuple where the storage for pending messages is a pre-allocated buffer of a fixed size. All sends will be synchronous by blocking until there is buffer space available. Note that a bound of 0 is allowed, causing the channel to become a "rendezvous" channel where each sender atomically hands off a message to a receiver.

Disconnection

The send and receive operations on channels will all return a Result indicating whether the operation succeeded or not. An unsuccessful operation is normally indicative of the other half of a channel having "hung up" by being dropped in its corresponding thread.

Once half of a channel has been deallocated, most operations can no longer continue to make progress, so Err will be returned. Many applications will continue to unwrap the results returned from this module, instigating a propagation of failure among threads if one unexpectedly dies.

Examples

Simple usage:

#![feature(mpmc_channel)]

use std::thread;
use std::sync::mpmc::channel;

// Create a simple streaming channel
let (tx, rx) = channel();
thread::spawn(move || {
    tx.send(10).unwrap();
});
assert_eq!(rx.recv().unwrap(), 10);

Shared usage:

#![feature(mpmc_channel)]

use std::thread;
use std::sync::mpmc::channel;

thread::scope(|s| {
    // Create a shared channel that can be sent along from many threads
    // where tx is the sending half (tx for transmission), and rx is the receiving
    // half (rx for receiving).
    let (tx, rx) = channel();
    for i in 0..10 {
        let tx = tx.clone();
        s.spawn(move || {
            tx.send(i).unwrap();
        });
    }

    for _ in 0..5 {
        let rx1 = rx.clone();
        let rx2 = rx.clone();
        s.spawn(move || {
            let j = rx1.recv().unwrap();
            assert!(0 <= j && j < 10);
        });
        s.spawn(move || {
            let j = rx2.recv().unwrap();
            assert!(0 <= j && j < 10);
        });
    }
})

Propagating panics:

#![feature(mpmc_channel)]

use std::sync::mpmc::channel;

// The call to recv() will return an error because the channel has already
// hung up (or been deallocated)
let (tx, rx) = channel::<i32>();
drop(tx);
assert!(rx.recv().is_err());

Structs

Functions