Crate async_ffi[][src]

FFI-compatible futures

FfiFuture<T> provides the same function as Box<dyn Future<Output = T>> but FFI-compatible. Any future implementing Send can be converted to FfiFuture<T> by calling into_ffi on it.

FfiFuture<T> also implements Future<Output = T>. You can simply await a FfiFuture<T> like a normal Future to get the output.

In case of an async program with some async plugins, Futures need to cross the FFI boundary. But Rust currently doesn’t provide stable ABI nor stable layout of related structs like dyn Future and Waker. With this crate, we can easily wrap async blocks or async functions to make this happen.

Provide some async functions in library: (plugin side)

// Compile with `crate-type = ["cdylib"]`.
use async_ffi::{FfiFuture, FutureExt};

pub extern "C" fn work(arg: u32) -> FfiFuture<u32> {
    async move {
        let ret = do_some_io(arg).await;

Execute async functions from external library: (host or executor side)

use async_ffi::{FfiFuture, FutureExt};

// #[link(name = "myplugin...")]
extern "C" {
    fn work(arg: u32) -> FfiFuture<u32>;

async fn run_work(arg: u32) -> u32 {
    unsafe { work(arg).await }



The FFI compatible future type.



Helper trait to provide conversion method to FfiFuture on all Futures implementing Send.