1 use futures_sink::Sink; 2 3 use futures_core::stream::Stream; 4 use pin_project_lite::pin_project; 5 use std::io; 6 use std::pin::Pin; 7 use std::task::{ready, Context, Poll}; 8 use tokio::io::{AsyncRead, AsyncWrite}; 9 10 pin_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 70 impl<S> SinkWriter<S> { 71 /// Creates a new [`SinkWriter`]. new(sink: S) -> Self72 pub fn new(sink: S) -> Self { 73 Self { inner: sink } 74 } 75 76 /// Gets a reference to the underlying sink. get_ref(&self) -> &S77 pub fn get_ref(&self) -> &S { 78 &self.inner 79 } 80 81 /// Gets a mutable reference to the underlying sink. get_mut(&mut self) -> &mut S82 pub fn get_mut(&mut self) -> &mut S { 83 &mut self.inner 84 } 85 86 /// Consumes this [`SinkWriter`], returning the underlying sink. into_inner(self) -> S87 pub fn into_inner(self) -> S { 88 self.inner 89 } 90 } 91 impl<S, E> AsyncWrite for SinkWriter<S> 92 where 93 for<'a> S: Sink<&'a [u8], Error = E>, 94 E: Into<io::Error>, 95 { poll_write( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8], ) -> Poll<Result<usize, io::Error>>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 poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>>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 poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>>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 } 118 119 impl<S: Stream> Stream for SinkWriter<S> { 120 type Item = S::Item; poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::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 } 125 126 impl<S: AsyncRead> AsyncRead for SinkWriter<S> { poll_read( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut tokio::io::ReadBuf<'_>, ) -> Poll<io::Result<()>>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 } 135