blob: 475f4469017ae39d5cd7b01fb78f1fb105cce842 [file] [log] [blame]
use core::marker::Unpin;
use core::pin::Pin;
use futures_core::future::{FusedFuture, Future};
use futures_core::task::{LocalWaker, Poll};
use pin_utils::{unsafe_pinned, unsafe_unpinned};
/// Do something with the item of a future, passing it on.
///
/// This is created by the [`super::FutureExt::inspect`] method.
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct Inspect<Fut, F> where Fut: Future {
future: Fut,
f: Option<F>,
}
impl<Fut: Future, F: FnOnce(&Fut::Output)> Inspect<Fut, F> {
unsafe_pinned!(future: Fut);
unsafe_unpinned!(f: Option<F>);
pub(super) fn new(future: Fut, f: F) -> Inspect<Fut, F> {
Inspect {
future,
f: Some(f),
}
}
}
impl<Fut: Future + Unpin, F> Unpin for Inspect<Fut, F> {}
impl<Fut: Future + FusedFuture, F> FusedFuture for Inspect<Fut, F> {
fn is_terminated(&self) -> bool { self.future.is_terminated() }
}
impl<Fut, F> Future for Inspect<Fut, F>
where Fut: Future,
F: FnOnce(&Fut::Output),
{
type Output = Fut::Output;
fn poll(mut self: Pin<&mut Self>, lw: &LocalWaker) -> Poll<Fut::Output> {
let e = match self.as_mut().future().poll(lw) {
Poll::Pending => return Poll::Pending,
Poll::Ready(e) => e,
};
let f = self.as_mut().f().take().expect("cannot poll Inspect twice");
f(&e);
Poll::Ready(e)
}
}