ATO: A Simple Task Async Runtime for `no_std` and `no_alloc` Environments

ATO is a minimal asynchronous task runtime designed for no_std and no_alloc environments, making it suitable for embedded systems, operating system kernels, or other resource-constrained applications where the standard library is unavailable.

It provides a basic task spawner and a round-robin scheduler to run Futures to completion.

Features

no_std Compatible: Works in environments without the standard library.
No Allocator Needed: Designed to operate without dynamic memory allocation.
Task Spawner: Queue multiple asynchronous tasks.
Round-Robin Scheduling: Tasks are polled sequentially until completion.
Simple Sleep Functionality: Includes an async sleep function that requires a user-provided time source.
Fixed-Size Task Queue: Uses heapless::Q* for a statically-sized task queue, configurable at compile time.
Simple Yield Functionality: Allows yielding control back to the scheduler, enabling cooperative multitasking.

Motivation

In many no_std contexts, a full-fledged async runtime like Tokio or async-std is too heavy or relies on operating system features that aren't available. ATO aims to provide the bare essentials for cooperative multitasking with futures in such environments.

Migration from V1 to V2

The v2 release of ATO introduces breaking changes due to usage of no allocator required. This means that the Spawner is now not 'static but rather scoped to the stack frame it is created in. This allows ATO to work in no_alloc environments. Please take a look at the example for how to create and use a Spawner in v2.

Installation

Add ATO to your Cargo.toml:

[dependencies]
ato = "2.0.1" # Replace with the desired version

Usage

Here's a basic example of how to use ATO:

use ato::Spawner;

const SPAWNER_SIZE: usize = 4; // Must be a power of two, e.g., 2, 4, 8, 16, etc.

fn main() {
    // create a spawner with the specified size
    let spawner: Spawner<SPAWNER_SIZE> = Spawner::default();

    // create a simple task that prints a message
    ato::task!(task, {
        println!("Hello, World!");
    });
    spawner.spawn(task).unwrap();

    // run until all tasks are done running
    spawner.run_until_all_done().unwrap();
}