async-fuse

Helpers for "fusing" asynchronous computations.

A fused operation has a well-defined behavior once the operation has completed. In this library, it means that a fused operation that has completed will block forever by returning [Poll::Pending].

This is similar to the Fuse type provided in futures-rs, but provides more utility allowing it to interact with types which does not implement [FusedFuture] or [FusedStream] as is now the case with all core Tokio types since 1.0.

This is especially useful in combination with optional branches using [tokio::select], where the future being polled is optionally set. So instead of requiring a [branch precondition], the future will simply be marked as pending indefinitely and behave accordingly when polled.

Features

• stream - Makes the [Fuse] implement the [Stream] trait if it contains a stream.

Examples

This is available as the stack_ticker example: sh cargo run --example stack_ticker

```rust use async_fuse::Fuse; use std::time::Duration; use tokio::time;

let mut duration = Duration::from_millis(500);

let sleep = Fuse::new(time::sleep(duration)); tokio::pin!(sleep);

let updateduration = Fuse::new(time::sleep(Duration::fromsecs(2))); tokio::pin!(update_duration);

for _ in 0..10usize { tokio::select! { _ = &mut sleep => { println!("Tick"); sleep.set(Fuse::new(time::sleep(duration))); } _ = &mut updateduration => { println!("Tick faster!"); duration = Duration::frommillis(250); } } } ```

For some types it might be easier to fuse the value on the heap. To make this easier, we provide the [Fuse::pin] constructor which provides a fused value which is pinned on the heap.

As a result, it looks pretty similar to the above example.

This is available as the heap_ticker example: sh cargo run --example heap_ticker

```rust use async_fuse::Fuse; use std::time::Duration; use tokio::time;

let mut duration = Duration::from_millis(500);

let mut sleep = Fuse::pin(time::sleep(duration)); let mut updateduration = Fuse::pin(time::sleep(Duration::fromsecs(2)));

for _ in 0..10usize { tokio::select! { _ = &mut sleep => { println!("Tick"); sleep.set(Box::pin(time::sleep(duration))); } _ = &mut updateduration => { println!("Tick faster!"); duration = Duration::frommillis(250); } } } ```

License: MIT/Apache-2.0