gecko-dev/third_party/rust/ringbuf

ringbuf

Lock-free single-producer single-consumer (SPSC) FIFO ring buffer with direct access to inner data.

Overview

RingBuffer is the initial structure representing ring buffer itself. Ring buffer can be splitted into pair of Producer and Consumer.

Producer and Consumer are used to append/remove elements to/from the ring buffer accordingly. They can be safely transfered between threads. Operations with Producer and Consumer are lock-free - they're succeded or failed immediately without blocking or waiting.

Elements can be effectively appended/removed one by one or many at once. Also data could be loaded/stored directly into/from Read/Write instances. And finally, there are unsafe methods allowing thread-safe direct access in place to the inner memory being appended/removed.

When building with nightly toolchain it is possible to run benchmarks via cargo bench --features benchmark.

Examples

Simple example

use ringbuf::RingBuffer;

let rb = RingBuffer::<i32>::new(2);
let (mut prod, mut cons) = rb.split();

prod.push(0).unwrap();
prod.push(1).unwrap();
assert_eq!(prod.push(2), Err(2));

assert_eq!(cons.pop().unwrap(), 0);

prod.push(2).unwrap();

assert_eq!(cons.pop().unwrap(), 1);
assert_eq!(cons.pop().unwrap(), 2);
assert_eq!(cons.pop(), None);

Message transfer

This is more complicated example of transfering text message between threads.

use std::io::Read;
use std::thread;
use std::time::Duration;

use ringbuf::RingBuffer;

let buf = RingBuffer::<u8>::new(10);
let (mut prod, mut cons) = buf.split();

let smsg = "The quick brown fox jumps over the lazy dog";

let pjh = thread::spawn(move || {
    println!("-> sending message: '{}'", smsg);

    let zero = [0 as u8];
    let mut bytes = smsg.as_bytes().chain(&zero[..]);
    loop {
        if prod.is_full() {
            println!("-> buffer is full, waiting");
            thread::sleep(Duration::from_millis(1));
        } else {
            let n = prod.read_from(&mut bytes, None).unwrap();
            if n == 0 {
                break;
            }
            println!("-> {} bytes sent", n);
        }
    }

    println!("-> message sent");
});

let cjh = thread::spawn(move || {
    println!("<- receiving message");

    let mut bytes = Vec::<u8>::new();
    loop {
        if cons.is_empty() {
            if bytes.ends_with(&[0]) {
                break;
            } else {
                println!("<- buffer is empty, waiting");
                thread::sleep(Duration::from_millis(1));
            }
        } else {
            let n = cons.write_into(&mut bytes, None).unwrap();
            println!("<- {} bytes received", n);
        }
    }

    assert_eq!(bytes.pop().unwrap(), 0);
    let msg = String::from_utf8(bytes).unwrap();
    println!("<- message received: '{}'", msg);

    msg
});

pjh.join().unwrap();
let rmsg = cjh.join().unwrap();

assert_eq!(smsg, rmsg);

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.