iq-scm / stackfuture

A wrapper around Rust futures that stores the future in space provided by the caller.

StackFuture

This crate defines a StackFuture wrapper around futures that stores the wrapped future in space provided by the caller. This can be used to emulate dynamic async traits without requiring heap allocation. Below is an example of how use StackFuture:

use stackfuture::*;

trait PseudoAsyncTrait {
    fn do_something(&self) -> StackFuture<'static, (), { 512 }>;
}

impl PseudoAsyncTrait for i32 {
    fn do_something(&self) -> StackFuture<'static, (), { 512 }> {
        StackFuture::from(async {
            // function body goes here
        })
    }
}

async fn use_dyn_async_trait(x: &dyn PseudoAsyncTrait) {
    x.do_something().await;
}

async fn call_with_dyn_async_trait() {
    use_dyn_async_trait(&42).await;
}

This is most useful for cases where async functions in dyn Trait objects are needed but storing them in a Box is not feasible. Such cases include embedded programming where allocation is not available, or in tight inner loops where the performance overhead for allocation is unacceptable. Note that doing this involves tradeoffs. In the case of StackFuture, you must set a compile-time limit on the maximum size of future that will be supported. If you need to support async functions in dyn Trait objects but these constraints do not apply to you, you may be better served by the async-trait crate.

Contributing

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This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact [email protected] with any additional questions or comments.

Trademarks

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