blob: c3409ee86d37ab85ca64378fae6fff5e29e6c485 [file] [log] [blame]
use core::marker::Unpin;
use core::mem::PinMut;
use futures_core::future::{Future, TryFuture};
use futures_core::stream::TryStream;
use futures_core::task::{self, Poll};
use pin_utils::{unsafe_pinned, unsafe_unpinned};
/// A stream combinator which attempts to execute an async closure over each
/// future in a stream.
///
/// This future is returned by the `TryStream::try_for_each` method.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct TryForEach<St, Fut, F> {
stream: St,
f: F,
future: Option<Fut>,
}
impl<St: Unpin, Fut: Unpin, F> Unpin for TryForEach<St, Fut, F> {}
impl<St, Fut, F> TryForEach<St, Fut, F>
where St: TryStream,
F: FnMut(St::Ok) -> Fut,
Fut: TryFuture<Ok = (), Error = St::Error>,
{
unsafe_pinned!(stream: St);
unsafe_unpinned!(f: F);
unsafe_pinned!(future: Option<Fut>);
pub(super) fn new(stream: St, f: F) -> TryForEach<St, Fut, F> {
TryForEach {
stream,
f,
future: None,
}
}
}
impl<St, Fut, F> Future for TryForEach<St, Fut, F>
where St: TryStream,
F: FnMut(St::Ok) -> Fut,
Fut: TryFuture<Ok = (), Error = St::Error>,
{
type Output = Result<(), St::Error>;
fn poll(mut self: PinMut<Self>, cx: &mut task::Context) -> Poll<Self::Output> {
loop {
if let Some(future) = self.future().as_pin_mut() {
try_ready!(future.try_poll(cx));
}
PinMut::set(self.future(), None);
match ready!(self.stream().try_poll_next(cx)) {
Some(Ok(e)) => {
let future = (self.f())(e);
PinMut::set(self.future(), Some(future));
}
Some(Err(e)) => return Poll::Ready(Err(e)),
None => return Poll::Ready(Ok(())),
}
}
}
}