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use std::prelude::v1::*;
use std::any::Any;
use std::panic::{catch_unwind, UnwindSafe, AssertUnwindSafe};
use std::mem;
use futures_core::{Poll, Async, Stream};
use futures_core::task;
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct CatchUnwind<S> where S: Stream {
state: CatchUnwindState<S>,
}
pub fn new<S>(stream: S) -> CatchUnwind<S>
where S: Stream + UnwindSafe,
{
CatchUnwind {
state: CatchUnwindState::Stream(stream),
}
}
#[derive(Debug)]
enum CatchUnwindState<S> {
Stream(S),
Eof,
Done,
}
impl<S> Stream for CatchUnwind<S>
where S: Stream + UnwindSafe,
{
type Item = Result<S::Item, S::Error>;
type Error = Box<Any + Send>;
fn poll_next(&mut self, cx: &mut task::Context) -> Poll<Option<Self::Item>, Self::Error> {
let mut stream = match mem::replace(&mut self.state, CatchUnwindState::Eof) {
CatchUnwindState::Done => panic!("cannot poll after eof"),
CatchUnwindState::Eof => {
self.state = CatchUnwindState::Done;
return Ok(Async::Ready(None));
}
CatchUnwindState::Stream(stream) => stream,
};
let res = catch_unwind(AssertUnwindSafe(|| (stream.poll_next(cx), stream)));
match res {
Err(e) => Err(e),
Ok((poll, stream)) => {
self.state = CatchUnwindState::Stream(stream);
match poll {
Err(e) => Ok(Async::Ready(Some(Err(e)))),
Ok(Async::Pending) => Ok(Async::Pending),
Ok(Async::Ready(Some(r))) => Ok(Async::Ready(Some(Ok(r)))),
Ok(Async::Ready(None)) => Ok(Async::Ready(None)),
}
}
}
}
}