futures_util/io/
sink.rs

1use futures_core::task::{Context, Poll};
2use futures_io::{AsyncWrite, IoSlice};
3use std::fmt;
4use std::io;
5use std::pin::Pin;
6
7/// Writer for the [`sink()`] function.
8#[must_use = "writers do nothing unless polled"]
9pub 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/// ```
30pub fn sink() -> Sink {
31    Sink { _priv: () }
32}
33
34impl AsyncWrite for Sink {
35    #[inline]
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]
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]
54    fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
55        Poll::Ready(Ok(()))
56    }
57    #[inline]
58    fn poll_close(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
59        Poll::Ready(Ok(()))
60    }
61}
62
63impl fmt::Debug for Sink {
64    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
65        f.pad("Sink { .. }")
66    }
67}
futures_util/io/sink.rs

futures_util/io/
sink.rs
