blob: 2de497e2a3167564e4794880ad2c130903f9633b [file] [log] [blame]
use super::Chain;
use core::pin::Pin;
use futures_core::future::{FusedFuture, Future};
use futures_core::task::{LocalWaker, Poll};
use pin_utils::unsafe_pinned;
/// Future for the `then` combinator, chaining computations on the end of
/// another future regardless of its outcome.
///
/// This is created by the `Future::then` method.
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct Then<Fut1, Fut2, F> {
chain: Chain<Fut1, Fut2, F>,
}
impl<Fut1, Fut2, F> Then<Fut1, Fut2, F>
where Fut1: Future,
Fut2: Future,
{
unsafe_pinned!(chain: Chain<Fut1, Fut2, F>);
/// Creates a new `Then`.
pub(super) fn new(future: Fut1, f: F) -> Then<Fut1, Fut2, F> {
Then {
chain: Chain::new(future, f),
}
}
}
impl<Fut1, Fut2, F> FusedFuture for Then<Fut1, Fut2, F> {
fn is_terminated(&self) -> bool { self.chain.is_terminated() }
}
impl<Fut1, Fut2, F> Future for Then<Fut1, Fut2, F>
where Fut1: Future,
Fut2: Future,
F: FnOnce(Fut1::Output) -> Fut2,
{
type Output = Fut2::Output;
fn poll(mut self: Pin<&mut Self>, lw: &LocalWaker) -> Poll<Fut2::Output> {
self.as_mut().chain().poll(lw, |output, f| f(output))
}
}