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

async_sink/ext/
with.rs
