futures_util/sink/
drain.rs

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1use super::assert_sink;
2use crate::never::Never;
3use core::marker::PhantomData;
4use core::pin::Pin;
5use futures_core::task::{Context, Poll};
6use futures_sink::Sink;
7
8/// Sink for the [`drain`] function.
9#[derive(Debug)]
10#[must_use = "sinks do nothing unless polled"]
11pub struct Drain<T> {
12    marker: PhantomData<T>,
13}
14
15/// Create a sink that will just discard all items given to it.
16///
17/// Similar to [`io::Sink`](::std::io::Sink).
18///
19/// # Examples
20///
21/// ```
22/// # futures::executor::block_on(async {
23/// use futures::sink::{self, SinkExt};
24///
25/// let mut drain = sink::drain();
26/// drain.send(5).await?;
27/// # Ok::<(), futures::never::Never>(()) }).unwrap();
28/// ```
29pub fn drain<T>() -> Drain<T> {
30    assert_sink::<T, Never, _>(Drain { marker: PhantomData })
31}
32
33impl<T> Unpin for Drain<T> {}
34
35impl<T> Clone for Drain<T> {
36    fn clone(&self) -> Self {
37        drain()
38    }
39}
40
41impl<T> Sink<T> for Drain<T> {
42    type Error = Never;
43
44    fn poll_ready(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
45        Poll::Ready(Ok(()))
46    }
47
48    fn start_send(self: Pin<&mut Self>, _item: T) -> Result<(), Self::Error> {
49        Ok(())
50    }
51
52    fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
53        Poll::Ready(Ok(()))
54    }
55
56    fn poll_close(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
57        Poll::Ready(Ok(()))
58    }
59}
futures_util/sink/drain.rs

futures_util/sink/
drain.rs
