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5099ac24 FG |
1 | use core::fmt; |
2 | use core::pin::Pin; | |
3 | use futures_core::future::TryFuture; | |
4 | use futures_core::ready; | |
5 | use futures_core::stream::{FusedStream, Stream, TryStream}; | |
6 | use futures_core::task::{Context, Poll}; | |
7 | #[cfg(feature = "sink")] | |
8 | use futures_sink::Sink; | |
9 | use pin_project_lite::pin_project; | |
10 | ||
11 | pin_project! { | |
12 | /// Stream for the [`try_filter_map`](super::TryStreamExt::try_filter_map) | |
13 | /// method. | |
14 | #[must_use = "streams do nothing unless polled"] | |
15 | pub struct TryFilterMap<St, Fut, F> { | |
16 | #[pin] | |
17 | stream: St, | |
18 | f: F, | |
19 | #[pin] | |
20 | pending: Option<Fut>, | |
21 | } | |
22 | } | |
23 | ||
24 | impl<St, Fut, F> fmt::Debug for TryFilterMap<St, Fut, F> | |
25 | where | |
26 | St: fmt::Debug, | |
27 | Fut: fmt::Debug, | |
28 | { | |
29 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | |
30 | f.debug_struct("TryFilterMap") | |
31 | .field("stream", &self.stream) | |
32 | .field("pending", &self.pending) | |
33 | .finish() | |
34 | } | |
35 | } | |
36 | ||
37 | impl<St, Fut, F> TryFilterMap<St, Fut, F> { | |
38 | pub(super) fn new(stream: St, f: F) -> Self { | |
39 | Self { stream, f, pending: None } | |
40 | } | |
41 | ||
42 | delegate_access_inner!(stream, St, ()); | |
43 | } | |
44 | ||
45 | impl<St, Fut, F, T> FusedStream for TryFilterMap<St, Fut, F> | |
46 | where | |
47 | St: TryStream + FusedStream, | |
48 | Fut: TryFuture<Ok = Option<T>, Error = St::Error>, | |
49 | F: FnMut(St::Ok) -> Fut, | |
50 | { | |
51 | fn is_terminated(&self) -> bool { | |
52 | self.pending.is_none() && self.stream.is_terminated() | |
53 | } | |
54 | } | |
55 | ||
56 | impl<St, Fut, F, T> Stream for TryFilterMap<St, Fut, F> | |
57 | where | |
58 | St: TryStream, | |
59 | Fut: TryFuture<Ok = Option<T>, Error = St::Error>, | |
60 | F: FnMut(St::Ok) -> Fut, | |
61 | { | |
62 | type Item = Result<T, St::Error>; | |
63 | ||
64 | fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> { | |
65 | let mut this = self.project(); | |
66 | ||
67 | Poll::Ready(loop { | |
68 | if let Some(p) = this.pending.as_mut().as_pin_mut() { | |
69 | // We have an item in progress, poll that until it's done | |
70 | let res = ready!(p.try_poll(cx)); | |
71 | this.pending.set(None); | |
72 | let item = res?; | |
73 | if item.is_some() { | |
74 | break item.map(Ok); | |
75 | } | |
76 | } else if let Some(item) = ready!(this.stream.as_mut().try_poll_next(cx)?) { | |
77 | // No item in progress, but the stream is still going | |
78 | this.pending.set(Some((this.f)(item))); | |
79 | } else { | |
80 | // The stream is done | |
81 | break None; | |
82 | } | |
83 | }) | |
84 | } | |
85 | ||
86 | fn size_hint(&self) -> (usize, Option<usize>) { | |
353b0b11 | 87 | let pending_len = usize::from(self.pending.is_some()); |
5099ac24 FG |
88 | let (_, upper) = self.stream.size_hint(); |
89 | let upper = match upper { | |
90 | Some(x) => x.checked_add(pending_len), | |
91 | None => None, | |
92 | }; | |
93 | (0, upper) // can't know a lower bound, due to the predicate | |
94 | } | |
95 | } | |
96 | ||
97 | // Forwarding impl of Sink from the underlying stream | |
98 | #[cfg(feature = "sink")] | |
99 | impl<S, Fut, F, Item> Sink<Item> for TryFilterMap<S, Fut, F> | |
100 | where | |
101 | S: Sink<Item>, | |
102 | { | |
103 | type Error = S::Error; | |
104 | ||
105 | delegate_sink!(stream, Item); | |
106 | } |