Crate pasts

Expand description

Minimal and simpler alternative to the futures crate.

Optional Features

The std feature is enabled by default, disable it to use on no-std.

The web feature is disabled by default, enable it to use pasts within the javascript DOM.

Getting Started

Add the following to your ./Cargo.toml:

autobins = false

[[bin]]
name = "app"
path = "app/main.rs"

[dependencies]
pasts = "0.11"
# This example uses async-std for a sleep future, but async-std is *not*
# required to use pasts.
async-std = "1.11"

# Use web feature when compiling to wasm32-unknown-unknown
[target.'cfg(all(target_arch="wasm32",target_os="unknown"))'.dependencies]
pasts = { version = "0.11", features = ["web"] }
wasm-bindgen = "0.2"

Create ./app/main.rs:

// Shim for providing async main and handling platform-specific API differences
extern crate alloc;

#[allow(unused_imports)]
use self::main::*;

mod main {
    include!("../src/main.rs");

    #[allow(clippy::module_inception)]
    pub(super) mod main {
        pub(in super::super) async fn main(executor: pasts::Executor) {
            super::main(&executor).await
        }
    }
}

#[cfg_attr(
    all(target_arch = "wasm32", target_os = "none"),
    wasm_bindgen(start)
)]
pub fn main() {
    let executor = pasts::Executor::default();
    executor.spawn(Box::pin(self::main::main::main(executor.clone())));
}

Multi-Tasking On Multiple Iterators of Futures

This example runs two timers in parallel using the async-std crate counting from 0 to 6. The “one” task will always be run for count 6 and stop the program, although which task will run for count 5 may be either “one” or “two” because they trigger at the same time.

use core::time::Duration;

use async_std::task::sleep;
use pasts::{prelude::*, Join, Loop};

// Exit type for State.
struct Exit;

// Shared state between tasks on the thread.
struct State<'a> {
    counter: usize,
    one: &'a mut (dyn Notifier<Event = ()> + Unpin),
    two: &'a mut (dyn Notifier<Event = ()> + Unpin),
}

impl State<'_> {
    fn one(&mut self, _: ()) -> Poll<Exit> {
        println!("One {}", self.counter);
        self.counter += 1;

        if self.counter > 6 { Ready(Exit) } else { Pending }
    }

    fn two(&mut self, _: ()) -> Poll<Exit> {
        println!("Two {}", self.counter);
        self.counter += 1;

        Pending
    }
}

async fn main(_executor: &Executor) {
    let sleep = |seconds| sleep(Duration::from_secs_f64(seconds));
    let one = &mut Loop::pin(|| sleep(1.0));
    let two = &mut Loop::pin(|| sleep(2.0));
    let counter = 0;
    let mut state = State { counter, one, two };

    Join::new(&mut state)
        .on(|s| s.one, State::one)
        .on(|s| s.two, State::two)
        .await;
}