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use core::pin::Pin;
use futures_core::stream::{FusedStream, Stream, TryStream};
use futures_core::task::{Context, Poll};
use futures_sink::Sink;
use pin_utils::{unsafe_pinned, unsafe_unpinned};
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct MapOk<St, F> {
stream: St,
f: F,
}
impl<St, F> MapOk<St, F> {
unsafe_pinned!(stream: St);
unsafe_unpinned!(f: F);
pub(super) fn new(stream: St, f: F) -> Self {
MapOk { stream, f }
}
}
impl<St: Unpin, F> Unpin for MapOk<St, F> {}
impl<St: FusedStream, F> FusedStream for MapOk<St, F> {
fn is_terminated(&self) -> bool {
self.stream.is_terminated()
}
}
impl<St, F, T> Stream for MapOk<St, F>
where
St: TryStream,
F: FnMut(St::Ok) -> T,
{
type Item = Result<T, St::Error>;
#[allow(clippy::redundant_closure)]
fn poll_next(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<Self::Item>> {
match self.as_mut().stream().try_poll_next(cx) {
Poll::Pending => Poll::Pending,
Poll::Ready(opt) =>
Poll::Ready(opt.map(|res| res.map(|x| self.as_mut().f()(x)))),
}
}
}
impl<S, F, T, Item> Sink<Item> for MapOk<S, F>
where
S: TryStream + Sink<Item>,
F: FnMut(S::Ok) -> T,
{
type SinkError = S::SinkError;
delegate_sink!(stream, Item);
}