context.rs

//! This module introduces `TokioContext`, which enables a simple way of using
//! the tokio runtime with any other executor.

use pin_project_lite::pin_project;
use std::{
    future::Future,
    pin::Pin,
    task::{Context, Poll},
};
use tokio::runtime::Handle;

pin_project! {
    /// TODO: add docs. Get some inspiration?
    pub struct TokioContext<F> {
        #[pin]
        inner: F,
        handle: Handle,
    }
}

impl<F: Future> Future for TokioContext<F> {
    type Output = F::Output;
    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let me = self.project();
        let handle = me.handle;
        let fut = me.inner;

        handle.enter(|| fut.poll(cx))
    }
}

impl<F: Future> TokioContext<F> {
    /// Creates a new `TokioContext`. Expects a future as its first argument, and a
    /// `tokio::runtime::Handle` as a second.
    pub fn new(f: F, handle: Handle) -> Self {
        Self { inner: f, handle }
    }
}