Desync

[dependencies]
desync = "0.2"

Desync provides a single type, Desync<T> that can be used to replace both threads and mutexes. This type schedules operations for a contained data structure so that they are always performed in order and optionally in the background.

Such a Desync object can be created like so:

use desync::Desync;
let number = Desync::new(0);

It supports two main operations. async will schedule a new job for the object that will run in a background thread. It's useful for deferring long-running operations and moving updates so they can run in parallel.

let number = Desync::new(0);
number.async(|val| {
    // Long update here
    thread::sleep(Duration::from_millis(100));
    *val = 42;
});

// We can carry on what we're doing with the update now running in the background

The other operation is sync, which schedules a job to run synchronously on the data structure. This is useful for retrieving values from a Desync.

let new_number = number.sync(|val| *val);           // = 42

Desync objects always run operations in the order that is provided, so all operations are serialized from the point of view of the data that they contain. When combined with the ability to perform operations asynchronously, this provides a useful way to immediately parallelize long-running operations.

Working with futures

Desync has support for the futures library. The simplest operation is future(), which creates a future that runs asynchronously on a Desync object but - unlike async() can return a result. It works like this:

let future_number = number.future(|val| *val);
assert!(executor::spawn(future_number).wait_future().unwrap() == 42);

There is also support for streams, via the pipe_in() and pipe() functions. These work on Arc<Desync<T>> references and provide a way to process a stream asynchronously. These two functions provide a powerful way to process input and also to connect Desync objects together using message-passing for communication.

let some_object = Arc::new(Desync::new(some_object));

pipe_in(Arc::clone(&number), some_stream, 
    |some_object, input| input.map(|input| some_object.process(input)));

let output_stream = pipe(Arc::clone(&number), some_stream, 
    |some_object, input| input.map(|input| some_object.process_with_output(input)));