1 use futures_core::task::{Context, Poll};
2 use futures_io::{AsyncWrite, IoSlice};
3 use std::fmt;
4 use std::io;
5 use std::pin::Pin;
6
7 /// Writer for the [`sink()`] function.
8 #[must_use = "writers do nothing unless polled"]
9 pub struct Sink {
10 _priv: (),
11 }
12
13 /// Creates an instance of a writer which will successfully consume all data.
14 ///
15 /// All calls to `poll_write` on the returned instance will return `Poll::Ready(Ok(buf.len()))`
16 /// and the contents of the buffer will not be inspected.
17 ///
18 /// # Examples
19 ///
20 /// ```rust
21 /// # futures::executor::block_on(async {
22 /// use futures::io::{self, AsyncWriteExt};
23 ///
24 /// let buffer = vec![1, 2, 3, 5, 8];
25 /// let mut writer = io::sink();
26 /// let num_bytes = writer.write(&buffer).await?;
27 /// assert_eq!(num_bytes, 5);
28 /// # Ok::<(), Box<dyn std::error::Error>>(()) }).unwrap();
29 /// ```
sink() -> Sink30 pub fn sink() -> Sink {
31 Sink { _priv: () }
32 }
33
34 impl AsyncWrite for Sink {
35 #[inline]
poll_write( self: Pin<&mut Self>, _: &mut Context<'_>, buf: &[u8], ) -> Poll<io::Result<usize>>36 fn poll_write(
37 self: Pin<&mut Self>,
38 _: &mut Context<'_>,
39 buf: &[u8],
40 ) -> Poll<io::Result<usize>> {
41 Poll::Ready(Ok(buf.len()))
42 }
43
44 #[inline]
poll_write_vectored( self: Pin<&mut Self>, _: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<io::Result<usize>>45 fn poll_write_vectored(
46 self: Pin<&mut Self>,
47 _: &mut Context<'_>,
48 bufs: &[IoSlice<'_>],
49 ) -> Poll<io::Result<usize>> {
50 Poll::Ready(Ok(bufs.iter().map(|b| b.len()).sum()))
51 }
52
53 #[inline]
poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>>54 fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
55 Poll::Ready(Ok(()))
56 }
57 #[inline]
poll_close(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>>58 fn poll_close(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
59 Poll::Ready(Ok(()))
60 }
61 }
62
63 impl fmt::Debug for Sink {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result64 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
65 f.pad("Sink { .. }")
66 }
67 }
68