Support interrupted streams in response

[connorslade]

The following code does not work because in the ResponseData write method, if the Reader returns any error, including interrupted kind errors it just passes it up. What it should do, is copy the impl of read_to_end in Read where it just continues. Perhaps spin-locking like this isn't the best solution long term, but it's easy enough, and it's not like anybody is going to stop me.

pub fn attach(server: &mut Server<App>) {
    server.route(afire::Method::GET, "/test", |_| {
        Response::new().stream(TestStream::new())
    });
}

struct TestStream {
    count: usize,
    last: Instant,
}

impl TestStream {
    fn new() -> Self {
        Self {
            count: 0,
            last: Instant::now(),
        }
    }
}

impl Read for TestStream {
    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
        if self.count > 10 {
            return Ok(0);
        }

        let elapsed = self.last.elapsed().as_secs_f64();
        if elapsed < 0.5 {
            return Err(std::io::Error::new(
                std::io::ErrorKind::Interrupted,
                "Not enough time has elapsed.",
            ));
        }

        self.count += 1;
        let data = format!("{{\"count\": {}}}", self.count);
        let bytes = data.as_bytes();
        let len = bytes.len().min(buf.len());
        buf[..len].copy_from_slice(&bytes[..len]);
        Ok(len)
    }
}