sqlx_core/ext/
async_stream.rs

1use std::future::Future;
2use std::pin::Pin;
3use std::task::{Context, Poll};
4
5use futures_channel::mpsc;
6use futures_core::future::BoxFuture;
7use futures_core::stream::Stream;
8use futures_util::{pin_mut, FutureExt, SinkExt};
9
10use crate::error::Error;
11
12pub struct TryAsyncStream<'a, T> {
13    receiver: mpsc::Receiver<Result<T, Error>>,
14    future: BoxFuture<'a, Result<(), Error>>,
15}
16
17impl<'a, T> TryAsyncStream<'a, T> {
18    pub fn new<F, Fut>(f: F) -> Self
19    where
20        F: FnOnce(mpsc::Sender<Result<T, Error>>) -> Fut + Send,
21        Fut: 'a + Future<Output = Result<(), Error>> + Send,
22        T: 'a + Send,
23    {
24        let (mut sender, receiver) = mpsc::channel(0);
25
26        let future = f(sender.clone());
27        let future = async move {
28            if let Err(error) = future.await {
29                let _ = sender.send(Err(error)).await;
30            }
31
32            Ok(())
33        }
34        .fuse()
35        .boxed();
36
37        Self { future, receiver }
38    }
39}
40
41impl<'a, T> Stream for TryAsyncStream<'a, T> {
42    type Item = Result<T, Error>;
43
44    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
45        let future = &mut self.future;
46        pin_mut!(future);
47
48        // the future is fused so its safe to call forever
49        // the future advances our "stream"
50        // the future should be polled in tandem with the stream receiver
51        let _ = future.poll(cx);
52
53        let receiver = &mut self.receiver;
54        pin_mut!(receiver);
55
56        // then we check to see if we have anything to return
57        receiver.poll_next(cx)
58    }
59}
60
61macro_rules! try_stream {
62    ($($block:tt)*) => {
63        crate::ext::async_stream::TryAsyncStream::new(move |mut sender| async move {
64            macro_rules! r#yield {
65                ($v:expr) => {{
66                    let _ = futures_util::sink::SinkExt::send(&mut sender, Ok($v)).await;
67                }}
68            }
69
70            $($block)*
71        })
72    }
73}
sqlx_core/ext/async_stream.rs

sqlx_core/ext/
async_stream.rs
