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dyn_future.rs
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dyn_future.rs
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// Pasts
//
// Copyright (c) 2019-2020 Jeron Aldaron Lau
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// https://apache.org/licenses/LICENSE-2.0>, or the Zlib License, <LICENSE-ZLIB
// or http://opensource.org/licenses/Zlib>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.
use core::{future::Future, mem, pin::Pin, ptr, task::Context, task::Poll};
/// A wrapper around a `Future` trait object.
#[allow(missing_debug_implementations)]
pub struct DynFuture<'a, T>(&'a mut dyn Future<Output = T>);
impl<T> Future for DynFuture<'_, T> {
type Output = T;
#[allow(unsafe_code)]
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> {
// unsafe: This is safe because `DynFut` doesn't let you move it.
let mut fut = unsafe { Pin::new_unchecked(ptr::read(&self.0)) };
let ret = fut.as_mut().poll(cx);
mem::forget(fut);
ret
}
}
/// Trait for converting `Future`s into an abstraction of pinned trait objects.
pub trait DynFut<T> {
/// Turn a future into a generic type. This is useful for creating an array
/// of `Future`s.
fn fut(&mut self) -> DynFuture<'_, T>;
}
impl<T, F> DynFut<T> for F
where
F: Future<Output = T>,
{
fn fut(&mut self) -> DynFuture<'_, T> {
DynFuture(self)
}
}