miquels/async-stream-rs

Produce items for a stream from an async closure

async-stream

Use an async closure to produce items for a stream.

A way to produce items for a stream from an async closure, while we are waiting for official async yield support.

The obvious solution would be to just use a channel, spawn the async closure as a seperate task, letting it send items onto the sink end of the channel - the other end is the stream, producing those items.

However this results in overhead - memory allocations, context switching between the tasks, unnecessary buffering, and it makes canceling the stream (dropping it) harder than it needs to be.

The AsyncStream from this crate runs as a stream in the current task, using only async/await and no other unstable features.

Example:

#![feature(async_await)]
use futures::StreamExt;
use futures::executor::block_on;
use async_stream::async_stream;

let mut strm = async_stream!(u8, {
    for i in 0u8..10 {
        stream_send!(i);
    }
});

let fut = async {
    let mut count = 0;
    while let Some(item) = strm.next().await {
        println!("{:?}", item);
        count += 1;
    }
    assert!(count == 10);
};
block_on(fut);

Copyright and License.

• © 2019 Miquel van Smoorenburg
• Apache License, Version 2.0