1 use core::fmt;
2 use core::pin::Pin;
3 use futures_core::future::{FusedFuture, Future};
4 use futures_core::ready;
5 use futures_core::stream::TryStream;
6 use futures_core::task::{Context, Poll};
7 use pin_project_lite::pin_project;
8 
9 pin_project! {
10     /// Future for the [`try_all`](super::TryStreamExt::try_all) method.
11     #[must_use = "futures do nothing unless you `.await` or poll them"]
12     pub struct TryAll<St, Fut, F> {
13         #[pin]
14         stream: St,
15         f: F,
16         done: bool,
17         #[pin]
18         future: Option<Fut>,
19     }
20 }
21 
22 impl<St, Fut, F> fmt::Debug for TryAll<St, Fut, F>
23 where
24     St: fmt::Debug,
25     Fut: fmt::Debug,
26 {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result27     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
28         f.debug_struct("TryAll")
29             .field("stream", &self.stream)
30             .field("done", &self.done)
31             .field("future", &self.future)
32             .finish()
33     }
34 }
35 
36 impl<St, Fut, F> TryAll<St, Fut, F>
37 where
38     St: TryStream,
39     F: FnMut(St::Ok) -> Fut,
40     Fut: Future<Output = bool>,
41 {
new(stream: St, f: F) -> Self42     pub(super) fn new(stream: St, f: F) -> Self {
43         Self { stream, f, done: false, future: None }
44     }
45 }
46 
47 impl<St, Fut, F> FusedFuture for TryAll<St, Fut, F>
48 where
49     St: TryStream,
50     F: FnMut(St::Ok) -> Fut,
51     Fut: Future<Output = bool>,
52 {
is_terminated(&self) -> bool53     fn is_terminated(&self) -> bool {
54         self.done && self.future.is_none()
55     }
56 }
57 
58 impl<St, Fut, F> Future for TryAll<St, Fut, F>
59 where
60     St: TryStream,
61     F: FnMut(St::Ok) -> Fut,
62     Fut: Future<Output = bool>,
63 {
64     type Output = Result<bool, St::Error>;
65 
poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<bool, St::Error>>66     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<bool, St::Error>> {
67         let mut this = self.project();
68 
69         Poll::Ready(loop {
70             if let Some(fut) = this.future.as_mut().as_pin_mut() {
71                 // we're currently processing a future to produce a new value
72                 let acc = ready!(fut.poll(cx));
73                 this.future.set(None);
74                 if !acc {
75                     *this.done = true;
76                     break Ok(false);
77                 } // early exit
78             } else if !*this.done {
79                 // we're waiting on a new item from the stream
80                 match ready!(this.stream.as_mut().try_poll_next(cx)) {
81                     Some(Ok(item)) => {
82                         this.future.set(Some((this.f)(item)));
83                     }
84                     Some(Err(err)) => {
85                         *this.done = true;
86                         break Err(err);
87                     }
88                     None => {
89                         *this.done = true;
90                         break Ok(true);
91                     }
92                 }
93             } else {
94                 panic!("TryAll polled after completion")
95             }
96         })
97     }
98 }
99