tokio_util/io/
sink_writer.rs

1use futures_sink::Sink;
2
3use futures_core::stream::Stream;
4use pin_project_lite::pin_project;
5use std::io;
6use std::pin::Pin;
7use std::task::{ready, Context, Poll};
8use tokio::io::{AsyncRead, AsyncWrite};
9
10pin_project! {
11    /// Convert a [`Sink`] of byte chunks into an [`AsyncWrite`].
12    ///
13    /// Whenever you write to this [`SinkWriter`], the supplied bytes are
14    /// forwarded to the inner [`Sink`]. When `shutdown` is called on this
15    /// [`SinkWriter`], the inner sink is closed.
16    ///
17    /// This adapter takes a `Sink<&[u8]>` and provides an [`AsyncWrite`] impl
18    /// for it. Because of the lifetime, this trait is relatively rarely
19    /// implemented. The main ways to get a `Sink<&[u8]>` that you can use with
20    /// this type are:
21    ///
22    ///  * With the codec module by implementing the [`Encoder`]`<&[u8]>` trait.
23    ///  * By wrapping a `Sink<Bytes>` in a [`CopyToBytes`].
24    ///  * Manually implementing `Sink<&[u8]>` directly.
25    ///
26    /// The opposite conversion of implementing `Sink<_>` for an [`AsyncWrite`]
27    /// is done using the [`codec`] module.
28    ///
29    /// # Example
30    ///
31    /// ```
32    /// use bytes::Bytes;
33    /// use futures_util::SinkExt;
34    /// use std::io::{Error, ErrorKind};
35    /// use tokio::io::AsyncWriteExt;
36    /// use tokio_util::io::{SinkWriter, CopyToBytes};
37    /// use tokio_util::sync::PollSender;
38    ///
39    /// # #[tokio::main(flavor = "current_thread")]
40    /// # async fn main() -> Result<(), Error> {
41    /// // We use an mpsc channel as an example of a `Sink<Bytes>`.
42    /// let (tx, mut rx) = tokio::sync::mpsc::channel::<Bytes>(1);
43    /// let sink = PollSender::new(tx).sink_map_err(|_| Error::from(ErrorKind::BrokenPipe));
44    ///
45    /// // Wrap it in `CopyToBytes` to get a `Sink<&[u8]>`.
46    /// let mut writer = SinkWriter::new(CopyToBytes::new(sink));
47    ///
48    /// // Write data to our interface...
49    /// let data: [u8; 4] = [1, 2, 3, 4];
50    /// let _ = writer.write(&data).await?;
51    ///
52    /// // ... and receive it.
53    /// assert_eq!(data.as_slice(), &*rx.recv().await.unwrap());
54    /// # Ok(())
55    /// # }
56    /// ```
57    ///
58    /// [`AsyncWrite`]: tokio::io::AsyncWrite
59    /// [`CopyToBytes`]: crate::io::CopyToBytes
60    /// [`Encoder`]: crate::codec::Encoder
61    /// [`Sink`]: futures_sink::Sink
62    /// [`codec`]: crate::codec
63    #[derive(Debug)]
64    pub struct SinkWriter<S> {
65        #[pin]
66        inner: S,
67    }
68}
69
70impl<S> SinkWriter<S> {
71    /// Creates a new [`SinkWriter`].
72    pub fn new(sink: S) -> Self {
73        Self { inner: sink }
74    }
75
76    /// Gets a reference to the underlying sink.
77    pub fn get_ref(&self) -> &S {
78        &self.inner
79    }
80
81    /// Gets a mutable reference to the underlying sink.
82    pub fn get_mut(&mut self) -> &mut S {
83        &mut self.inner
84    }
85
86    /// Consumes this [`SinkWriter`], returning the underlying sink.
87    pub fn into_inner(self) -> S {
88        self.inner
89    }
90}
91impl<S, E> AsyncWrite for SinkWriter<S>
92where
93    for<'a> S: Sink<&'a [u8], Error = E>,
94    E: Into<io::Error>,
95{
96    fn poll_write(
97        self: Pin<&mut Self>,
98        cx: &mut Context<'_>,
99        buf: &[u8],
100    ) -> Poll<Result<usize, io::Error>> {
101        let mut this = self.project();
102
103        ready!(this.inner.as_mut().poll_ready(cx).map_err(Into::into))?;
104        match this.inner.as_mut().start_send(buf) {
105            Ok(()) => Poll::Ready(Ok(buf.len())),
106            Err(e) => Poll::Ready(Err(e.into())),
107        }
108    }
109
110    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
111        self.project().inner.poll_flush(cx).map_err(Into::into)
112    }
113
114    fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
115        self.project().inner.poll_close(cx).map_err(Into::into)
116    }
117}
118
119impl<S: Stream> Stream for SinkWriter<S> {
120    type Item = S::Item;
121    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
122        self.project().inner.poll_next(cx)
123    }
124}
125
126impl<S: AsyncRead> AsyncRead for SinkWriter<S> {
127    fn poll_read(
128        self: Pin<&mut Self>,
129        cx: &mut Context<'_>,
130        buf: &mut tokio::io::ReadBuf<'_>,
131    ) -> Poll<io::Result<()>> {
132        self.project().inner.poll_read(cx, buf)
133    }
134}
tokio_util/io/sink_writer.rs

tokio_util/io/
sink_writer.rs
