1 use futures_core::ready; 2 use futures_sink::Sink; 3 4 use futures_core::stream::Stream; 5 use pin_project_lite::pin_project; 6 use std::io; 7 use std::pin::Pin; 8 use std::task::{Context, Poll}; 9 use tokio::io::{AsyncRead, AsyncWrite}; 10 11 pin_project! { 12 /// Convert a [`Sink`] of byte chunks into an [`AsyncWrite`]. 13 /// 14 /// Whenever you write to this [`SinkWriter`], the supplied bytes are 15 /// forwarded to the inner [`Sink`]. When `shutdown` is called on this 16 /// [`SinkWriter`], the inner sink is closed. 17 /// 18 /// This adapter takes a `Sink<&[u8]>` and provides an [`AsyncWrite`] impl 19 /// for it. Because of the lifetime, this trait is relatively rarely 20 /// implemented. The main ways to get a `Sink<&[u8]>` that you can use with 21 /// this type are: 22 /// 23 /// * With the codec module by implementing the [`Encoder`]`<&[u8]>` trait. 24 /// * By wrapping a `Sink<Bytes>` in a [`CopyToBytes`]. 25 /// * Manually implementing `Sink<&[u8]>` directly. 26 /// 27 /// The opposite conversion of implementing `Sink<_>` for an [`AsyncWrite`] 28 /// is done using the [`codec`] module. 29 /// 30 /// # Example 31 /// 32 /// ``` 33 /// use bytes::Bytes; 34 /// use futures_util::SinkExt; 35 /// use std::io::{Error, ErrorKind}; 36 /// use tokio::io::AsyncWriteExt; 37 /// use tokio_util::io::{SinkWriter, CopyToBytes}; 38 /// use tokio_util::sync::PollSender; 39 /// 40 /// # #[tokio::main(flavor = "current_thread")] 41 /// # async fn main() -> Result<(), Error> { 42 /// // We use an mpsc channel as an example of a `Sink<Bytes>`. 43 /// let (tx, mut rx) = tokio::sync::mpsc::channel::<Bytes>(1); 44 /// let sink = PollSender::new(tx).sink_map_err(|_| Error::from(ErrorKind::BrokenPipe)); 45 /// 46 /// // Wrap it in `CopyToBytes` to get a `Sink<&[u8]>`. 47 /// let mut writer = SinkWriter::new(CopyToBytes::new(sink)); 48 /// 49 /// // Write data to our interface... 50 /// let data: [u8; 4] = [1, 2, 3, 4]; 51 /// let _ = writer.write(&data).await?; 52 /// 53 /// // ... and receive it. 54 /// assert_eq!(data.as_slice(), &*rx.recv().await.unwrap()); 55 /// # Ok(()) 56 /// # } 57 /// ``` 58 /// 59 /// [`AsyncWrite`]: tokio::io::AsyncWrite 60 /// [`CopyToBytes`]: crate::io::CopyToBytes 61 /// [`Encoder`]: crate::codec::Encoder 62 /// [`Sink`]: futures_sink::Sink 63 /// [`codec`]: crate::codec 64 #[derive(Debug)] 65 pub struct SinkWriter<S> { 66 #[pin] 67 inner: S, 68 } 69 } 70 71 impl<S> SinkWriter<S> { 72 /// Creates a new [`SinkWriter`]. new(sink: S) -> Self73 pub fn new(sink: S) -> Self { 74 Self { inner: sink } 75 } 76 77 /// Gets a reference to the underlying sink. get_ref(&self) -> &S78 pub fn get_ref(&self) -> &S { 79 &self.inner 80 } 81 82 /// Gets a mutable reference to the underlying sink. get_mut(&mut self) -> &mut S83 pub fn get_mut(&mut self) -> &mut S { 84 &mut self.inner 85 } 86 87 /// Consumes this [`SinkWriter`], returning the underlying sink. into_inner(self) -> S88 pub fn into_inner(self) -> S { 89 self.inner 90 } 91 } 92 impl<S, E> AsyncWrite for SinkWriter<S> 93 where 94 for<'a> S: Sink<&'a [u8], Error = E>, 95 E: Into<io::Error>, 96 { poll_write( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8], ) -> Poll<Result<usize, io::Error>>97 fn poll_write( 98 self: Pin<&mut Self>, 99 cx: &mut Context<'_>, 100 buf: &[u8], 101 ) -> Poll<Result<usize, io::Error>> { 102 let mut this = self.project(); 103 104 ready!(this.inner.as_mut().poll_ready(cx).map_err(Into::into))?; 105 match this.inner.as_mut().start_send(buf) { 106 Ok(()) => Poll::Ready(Ok(buf.len())), 107 Err(e) => Poll::Ready(Err(e.into())), 108 } 109 } 110 poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>>111 fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> { 112 self.project().inner.poll_flush(cx).map_err(Into::into) 113 } 114 poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>>115 fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> { 116 self.project().inner.poll_close(cx).map_err(Into::into) 117 } 118 } 119 120 impl<S: Stream> Stream for SinkWriter<S> { 121 type Item = S::Item; poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>>122 fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> { 123 self.project().inner.poll_next(cx) 124 } 125 } 126 127 impl<S: AsyncRead> AsyncRead for SinkWriter<S> { poll_read( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut tokio::io::ReadBuf<'_>, ) -> Poll<io::Result<()>>128 fn poll_read( 129 self: Pin<&mut Self>, 130 cx: &mut Context<'_>, 131 buf: &mut tokio::io::ReadBuf<'_>, 132 ) -> Poll<io::Result<()>> { 133 self.project().inner.poll_read(cx, buf) 134 } 135 } 136