1 use futures_core::stream::{Stream, FusedStream};
2 use futures_core::task::{Context, Poll};
3 use pin_utils::{unsafe_pinned, unsafe_unpinned};
4 use std::any::Any;
5 use std::pin::Pin;
6 use std::panic::{catch_unwind, UnwindSafe, AssertUnwindSafe};
7 
8 /// Stream for the [`catch_unwind`](super::StreamExt::catch_unwind) method.
9 #[derive(Debug)]
10 #[must_use = "streams do nothing unless polled"]
11 pub struct CatchUnwind<St: Stream> {
12     stream: St,
13     caught_unwind: bool,
14 }
15 
16 impl<St: Stream + UnwindSafe> CatchUnwind<St> {
17     unsafe_pinned!(stream: St);
18     unsafe_unpinned!(caught_unwind: bool);
19 
new(stream: St) -> CatchUnwind<St>20     pub(super) fn new(stream: St) -> CatchUnwind<St> {
21         CatchUnwind { stream, caught_unwind: false }
22     }
23 }
24 
25 impl<St: Stream + UnwindSafe> Stream for CatchUnwind<St> {
26     type Item = Result<St::Item, Box<dyn Any + Send>>;
27 
poll_next( mut self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Option<Self::Item>>28     fn poll_next(
29         mut self: Pin<&mut Self>,
30         cx: &mut Context<'_>,
31     ) -> Poll<Option<Self::Item>> {
32         if self.caught_unwind {
33             Poll::Ready(None)
34         } else {
35             let res = catch_unwind(AssertUnwindSafe(|| {
36                 self.as_mut().stream().poll_next(cx)
37             }));
38 
39             match res {
40                 Ok(poll) => poll.map(|opt| opt.map(Ok)),
41                 Err(e) => {
42                     *self.as_mut().caught_unwind() = true;
43                     Poll::Ready(Some(Err(e)))
44                 },
45             }
46         }
47     }
48 
size_hint(&self) -> (usize, Option<usize>)49     fn size_hint(&self) -> (usize, Option<usize>) {
50         if self.caught_unwind {
51             (0, Some(0))
52         } else {
53             self.stream.size_hint()
54         }
55     }
56 }
57 
58 impl<St: FusedStream + UnwindSafe> FusedStream for CatchUnwind<St> {
is_terminated(&self) -> bool59     fn is_terminated(&self) -> bool {
60         self.caught_unwind || self.stream.is_terminated()
61     }
62 }
63