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try_filter_map.rs
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try_filter_map.rs
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use core::fmt;
use core::pin::Pin;
use futures_core::future::{TryFuture};
use futures_core::stream::{Stream, TryStream, FusedStream};
use futures_core::task::{Context, Poll};
#[cfg(feature = "sink")]
use futures_sink::Sink;
use pin_utils::{unsafe_pinned, unsafe_unpinned};
/// Stream for the [`try_filter_map`](super::TryStreamExt::try_filter_map)
/// method.
#[must_use = "streams do nothing unless polled"]
pub struct TryFilterMap<St, Fut, F> {
stream: St,
f: F,
pending: Option<Fut>,
}
impl<St, Fut, F> Unpin for TryFilterMap<St, Fut, F>
where St: Unpin, Fut: Unpin,
{}
impl<St, Fut, F> fmt::Debug for TryFilterMap<St, Fut, F>
where
St: fmt::Debug,
Fut: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("TryFilterMap")
.field("stream", &self.stream)
.field("pending", &self.pending)
.finish()
}
}
impl<St, Fut, F> TryFilterMap<St, Fut, F> {
unsafe_pinned!(stream: St);
unsafe_unpinned!(f: F);
unsafe_pinned!(pending: Option<Fut>);
pub(super) fn new(stream: St, f: F) -> Self {
TryFilterMap { stream, f, pending: None }
}
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &St {
&self.stream
}
/// Acquires a mutable reference to the underlying stream that this
/// combinator is pulling from.
///
/// Note that care must be taken to avoid tampering with the state of the
/// stream which may otherwise confuse this combinator.
pub fn get_mut(&mut self) -> &mut St {
&mut self.stream
}
/// Acquires a pinned mutable reference to the underlying stream that this
/// combinator is pulling from.
///
/// Note that care must be taken to avoid tampering with the state of the
/// stream which may otherwise confuse this combinator.
pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut St> {
self.stream()
}
/// Consumes this combinator, returning the underlying stream.
///
/// Note that this may discard intermediate state of this combinator, so
/// care should be taken to avoid losing resources when this is called.
pub fn into_inner(self) -> St {
self.stream
}
}
impl<St, Fut, F, T> FusedStream for TryFilterMap<St, Fut, F>
where St: TryStream + FusedStream,
Fut: TryFuture<Ok = Option<T>, Error = St::Error>,
F: FnMut(St::Ok) -> Fut,
{
fn is_terminated(&self) -> bool {
self.pending.is_none() && self.stream.is_terminated()
}
}
impl<St, Fut, F, T> Stream for TryFilterMap<St, Fut, F>
where St: TryStream,
Fut: TryFuture<Ok = Option<T>, Error = St::Error>,
F: FnMut(St::Ok) -> Fut,
{
type Item = Result<T, St::Error>;
fn poll_next(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<Result<T, St::Error>>> {
loop {
if self.pending.is_none() {
let item = match ready!(self.as_mut().stream().poll_next(cx)?) {
Some(x) => x,
None => return Poll::Ready(None),
};
let fut = (self.as_mut().f())(item);
self.as_mut().pending().set(Some(fut));
}
let result = ready!(self.as_mut().pending().as_pin_mut().unwrap().poll(cx));
self.as_mut().pending().set(None);
if let Some(x) = result? {
return Poll::Ready(Some(Ok(x)));
}
}
}
}
// Forwarding impl of Sink from the underlying stream
#[cfg(feature = "sink")]
impl<S, Fut, F, Item> Sink<Item> for TryFilterMap<S, Fut, F>
where S: Sink<Item>,
{
type Error = S::Error;
delegate_sink!(stream, Item);
}