tor_async_utils/
sinkext.rs

1//! Extension trait for `Sink`.
2
3use std::{
4    marker::PhantomData,
5    pin::Pin,
6    task::{Context, Poll},
7};
8
9use futures::{ready, sink::Sink};
10use pin_project::pin_project;
11
12/// Extension trait for `Sink`
13pub trait SinkExt<Item>: Sink<Item> {
14    /// As `Sink::with`, but takes a function that returns an `Item` rather
15    /// than `Future<Output=Item>`.
16    fn with_fn<F, T, E>(self, func: F) -> WithFn<Self, F, T, E>
17    // or error?
18    where
19        Self: Sized,
20        F: FnMut(T) -> Result<Item, E>,
21        E: From<Self::Error>,
22    {
23        WithFn {
24            sink: self,
25            func,
26            _phantom: PhantomData,
27        }
28    }
29}
30
31impl<Item, S> SinkExt<Item> for S where S: Sink<Item> {}
32
33/// Sink returned by [`SinkExt::with_fn`].
34#[pin_project]
35pub struct WithFn<S, F, T, E> {
36    /// The underlying sink
37    #[pin]
38    sink: S,
39    /// The user-provided function.
40    func: F,
41    /// Phantom data to ensure type consistency.
42    _phantom: PhantomData<fn() -> Result<T, E>>,
43}
44
45impl<S, Item, F, T, E> Sink<T> for WithFn<S, F, T, E>
46where
47    S: Sink<Item>,
48    F: FnMut(T) -> Result<Item, E>,
49    E: From<S::Error>,
50{
51    type Error = E;
52
53    fn poll_ready(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
54        ready!(self.project().sink.poll_ready(cx))?;
55        Poll::Ready(Ok(()))
56    }
57
58    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
59        ready!(self.project().sink.poll_flush(cx))?;
60        Poll::Ready(Ok(()))
61    }
62
63    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
64        ready!(self.project().sink.poll_close(cx))?;
65        Poll::Ready(Ok(()))
66    }
67
68    fn start_send(self: Pin<&mut Self>, item: T) -> Result<(), Self::Error> {
69        let this = self.project();
70        let item = (this.func)(item)?;
71        this.sink.start_send(item).map_err(E::from)
72    }
73}
tor_async_utils/sinkext.rs

tor_async_utils/
sinkext.rs
