flo_stream = "0.1"

flo_stream

flo_stream is a crate providing some extra utilities for streams in Rust's futures library. The primary new feature it provides is a "pubsub" mechanism - a way to subscribe to updates sent to a futures Sink. This differs from the Sender/Receiver mechanism provided in the main futures library in two key ways: it's possible to have multiple receivers, and messages sent when there is no subscriber connected will be ignored.

PubSub

The sink type provided is Publisher. You can create one with let publisher = Publisher::new(10). This implements the Sink trait so can be used in a very similar way to send messages. The number passed in is the maximum number of waiting messages allowed for any given subscriber.

A subscription can be created using let subscription = publisher.subscribe(). Any messages sent to the sink after this is called is relayed to all subscriptions. A subscription is a Stream so can interact with other parts of the futures library in the usual way.

Here's a full worked example with a single subscriber. Note the use of get_mut() with the spawned executor to create a new subscriber:

let publisher       = Publisher::new(10);
let mut publisher   = executor::spawn(publisher);

let subscriber      = publisher.get_mut().subscribe();
let mut subscriber  = executor::spawn(subscriber);

publisher.wait_send(1).unwrap();
publisher.wait_send(2).unwrap();
publisher.wait_send(3).unwrap();

assert!(subscriber.wait_stream() == Some(Ok(1)));
assert!(subscriber.wait_stream() == Some(Ok(2)));
assert!(subscriber.wait_stream() == Some(Ok(3)));