async_sink/ext/
with.rs

1use core::fmt;
2use core::future::Future;
3use core::marker::PhantomData;
4use core::pin::Pin;
5use core::task::{Context, Poll};
6use tokio_stream::Stream;
7use tokio_stream_util::FusedStream;
8
9use super::Sink;
10
11/// Sink for the [`with`](super::SinkExt::with) method.
12#[must_use = "sinks do nothing unless polled"]
13pub struct With<Si, Item, U, Fut, F> {
14    sink: Si,
15    f: F,
16    state: Option<Fut>,
17    _phantom: PhantomData<fn(U) -> Item>,
18}
19
20impl<Si: Unpin, Item, U, Fut: Unpin, F> Unpin for With<Si, Item, U, Fut, F> {}
21
22impl<Si, Item, U, Fut, F> fmt::Debug for With<Si, Item, U, Fut, F>
23where
24    Si: fmt::Debug,
25    Fut: fmt::Debug,
26{
27    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
28        f.debug_struct("With")
29            .field("sink", &self.sink)
30            .field("state", &self.state)
31            .finish()
32    }
33}
34
35impl<Si, Item, U, Fut, F> With<Si, Item, U, Fut, F>
36where
37    Si: Sink<Item>,
38    F: FnMut(U) -> Fut,
39    Fut: Future,
40{
41    pub(super) fn new<E>(sink: Si, f: F) -> Self
42    where
43        Fut: Future<Output = Result<Item, E>>,
44        E: From<Si::Error>,
45    {
46        Self {
47            state: None,
48            sink,
49            f,
50            _phantom: PhantomData,
51        }
52    }
53}
54
55impl<Si, Item, U, Fut, F> Clone for With<Si, Item, U, Fut, F>
56where
57    Si: Clone,
58    F: Clone,
59    Fut: Clone,
60{
61    fn clone(&self) -> Self {
62        Self {
63            state: self.state.clone(),
64            sink: self.sink.clone(),
65            f: self.f.clone(),
66            _phantom: PhantomData,
67        }
68    }
69}
70
71// Forwarding impl of Stream from the underlying sink
72impl<S, Item, U, Fut, F> Stream for With<S, Item, U, Fut, F>
73where
74    S: Stream + Sink<Item>,
75    F: FnMut(U) -> Fut,
76    Fut: Future,
77{
78    type Item = S::Item;
79
80    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
81        let this = unsafe { self.get_unchecked_mut() };
82        let sink = unsafe { Pin::new_unchecked(&mut this.sink) };
83        sink.poll_next(cx)
84    }
85
86    fn size_hint(&self) -> (usize, Option<usize>) {
87        self.sink.size_hint()
88    }
89}
90
91impl<S, Item, U, Fut, F> FusedStream for With<S, Item, U, Fut, F>
92where
93    S: FusedStream + Sink<Item>,
94    F: FnMut(U) -> Fut,
95    Fut: Future,
96{
97    fn is_terminated(&self) -> bool {
98        self.sink.is_terminated()
99    }
100}
101
102impl<Si, Item, U, Fut, F, E> With<Si, Item, U, Fut, F>
103where
104    Si: Sink<Item>,
105    F: FnMut(U) -> Fut,
106    Fut: Future<Output = Result<Item, E>>,
107    E: From<Si::Error>,
108{
109    /// Acquires a reference to the underlying sink.
110    pub fn get_ref(&self) -> &Si {
111        &self.sink
112    }
113
114    /// Acquires a mutable reference to the underlying sink.
115    ///
116    /// Note that care must be taken to avoid tampering with the state of the
117    /// sink which may otherwise confuse this combinator.
118    pub fn get_mut(&mut self) -> &mut Si {
119        &mut self.sink
120    }
121
122    /// Acquires a pinned mutable reference to the underlying sink.
123    ///
124    /// Note that care must be taken to avoid tampering with the state of the
125    /// sink which may otherwise confuse this combinator.
126    pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut Si> {
127        unsafe { Pin::new_unchecked(&mut self.get_unchecked_mut().sink) }
128    }
129
130    /// Consumes this combinator, returning the underlying sink.
131    ///
132    /// Note that this may discard intermediate state of this combinator, so
133    /// care should be taken to avoid losing resources when this is called.
134    pub fn into_inner(self) -> Si {
135        self.sink
136    }
137
138    /// Completes the processing of previous item if any.
139    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), E>> {
140        let this = unsafe { self.get_unchecked_mut() };
141
142        if let Some(fut) = this.state.as_mut() {
143            let item_res = match unsafe { Pin::new_unchecked(fut) }.poll(cx) {
144                Poll::Ready(res) => res,
145                Poll::Pending => return Poll::Pending,
146            };
147            this.state = None;
148            let item = match item_res {
149                Ok(item) => item,
150                Err(e) => return Poll::Ready(Err(e)),
151            };
152            let sink = unsafe { Pin::new_unchecked(&mut this.sink) };
153            if let Err(e) = sink.start_send(item) {
154                return Poll::Ready(Err(e.into()));
155            }
156        }
157
158        Poll::Ready(Ok(()))
159    }
160}
161
162impl<Si, Item, U, Fut, F, E> Sink<U> for With<Si, Item, U, Fut, F>
163where
164    Si: Sink<Item>,
165    F: FnMut(U) -> Fut,
166    Fut: Future<Output = Result<Item, E>>,
167    E: From<Si::Error>,
168{
169    type Error = E;
170
171    fn poll_ready(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
172        match self.as_mut().poll(cx) {
173            Poll::Ready(Ok(())) => {}
174            Poll::Ready(Err(e)) => return Poll::Ready(Err(e)),
175            Poll::Pending => return Poll::Pending,
176        }
177        let sink = unsafe { Pin::new_unchecked(&mut self.get_unchecked_mut().sink) };
178        match sink.poll_ready(cx) {
179            Poll::Ready(Ok(())) => Poll::Ready(Ok(())),
180            Poll::Ready(Err(e)) => Poll::Ready(Err(e.into())),
181            Poll::Pending => Poll::Pending,
182        }
183    }
184
185    fn start_send(self: Pin<&mut Self>, item: U) -> Result<(), Self::Error> {
186        let this = unsafe { self.get_unchecked_mut() };
187
188        assert!(this.state.is_none());
189        this.state = Some((this.f)(item));
190        Ok(())
191    }
192
193    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
194        match self.as_mut().poll(cx) {
195            Poll::Ready(Ok(())) => {}
196            Poll::Ready(Err(e)) => return Poll::Ready(Err(e)),
197            Poll::Pending => return Poll::Pending,
198        };
199        let sink = unsafe { Pin::new_unchecked(&mut self.get_unchecked_mut().sink) };
200        match sink.poll_flush(cx) {
201            Poll::Ready(Ok(())) => Poll::Ready(Ok(())),
202            Poll::Ready(Err(e)) => Poll::Ready(Err(e.into())),
203            Poll::Pending => Poll::Pending,
204        }
205    }
206
207    fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
208        match self.as_mut().poll(cx) {
209            Poll::Ready(Ok(())) => {}
210            Poll::Ready(Err(e)) => return Poll::Ready(Err(e)),
211            Poll::Pending => return Poll::Pending,
212        };
213        let sink = unsafe { Pin::new_unchecked(&mut self.get_unchecked_mut().sink) };
214        match sink.poll_close(cx) {
215            Poll::Ready(Ok(())) => Poll::Ready(Ok(())),
216            Poll::Ready(Err(e)) => Poll::Ready(Err(e.into())),
217            Poll::Pending => Poll::Pending,
218        }
219    }
220}
async_sink/ext/with.rs

async_sink/ext/
with.rs
