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use crate::future::maybe_done::{maybe_done, MaybeDone};
use pin_project_lite::pin_project;
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};
pub(crate) fn try_join3<T1, F1, T2, F2, T3, F3, E>(
future1: F1,
future2: F2,
future3: F3,
) -> TryJoin3<F1, F2, F3>
where
F1: Future<Output = Result<T1, E>>,
F2: Future<Output = Result<T2, E>>,
F3: Future<Output = Result<T3, E>>,
{
TryJoin3 {
future1: maybe_done(future1),
future2: maybe_done(future2),
future3: maybe_done(future3),
}
}
pin_project! {
pub(crate) struct TryJoin3<F1, F2, F3>
where
F1: Future,
F2: Future,
F3: Future,
{
#[pin]
future1: MaybeDone<F1>,
#[pin]
future2: MaybeDone<F2>,
#[pin]
future3: MaybeDone<F3>,
}
}
impl<T1, F1, T2, F2, T3, F3, E> Future for TryJoin3<F1, F2, F3>
where
F1: Future<Output = Result<T1, E>>,
F2: Future<Output = Result<T2, E>>,
F3: Future<Output = Result<T3, E>>,
{
type Output = Result<(T1, T2, T3), E>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let mut all_done = true;
let mut me = self.project();
if me.future1.as_mut().poll(cx).is_pending() {
all_done = false;
} else if me.future1.as_mut().output_mut().unwrap().is_err() {
return Poll::Ready(Err(me.future1.take_output().unwrap().err().unwrap()));
}
if me.future2.as_mut().poll(cx).is_pending() {
all_done = false;
} else if me.future2.as_mut().output_mut().unwrap().is_err() {
return Poll::Ready(Err(me.future2.take_output().unwrap().err().unwrap()));
}
if me.future3.as_mut().poll(cx).is_pending() {
all_done = false;
} else if me.future3.as_mut().output_mut().unwrap().is_err() {
return Poll::Ready(Err(me.future3.take_output().unwrap().err().unwrap()));
}
if all_done {
Poll::Ready(Ok((
me.future1.take_output().unwrap().ok().unwrap(),
me.future2.take_output().unwrap().ok().unwrap(),
me.future3.take_output().unwrap().ok().unwrap(),
)))
} else {
Poll::Pending
}
}
}