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use crate::io::AsyncWrite;
use std::fmt;
use std::io;
use std::pin::Pin;
use std::task::{Context, Poll};
cfg_io_util! {
/// An async writer which will move data into the void.
///
/// This struct is generally created by calling [`sink`][sink]. Please
/// see the documentation of `sink()` for more details.
///
/// This is an asynchronous version of [`std::io::Sink`][std].
///
/// [sink]: sink()
/// [std]: std::io::Sink
pub struct Sink {
_p: (),
}
/// Creates an instance of an async writer which will successfully consume all
/// data.
///
/// All calls to [`poll_write`] on the returned instance will return
/// `Poll::Ready(Ok(buf.len()))` and the contents of the buffer will not be
/// inspected.
///
/// This is an asynchronous version of [`std::io::sink`][std].
///
/// [`poll_write`]: crate::io::AsyncWrite::poll_write()
/// [std]: std::io::sink
///
/// # Examples
///
/// ```
/// use tokio::io::{self, AsyncWriteExt};
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let buffer = vec![1, 2, 3, 5, 8];
/// let num_bytes = io::sink().write(&buffer).await?;
/// assert_eq!(num_bytes, 5);
/// Ok(())
/// }
/// ```
pub fn sink() -> Sink {
Sink { _p: () }
}
}
impl AsyncWrite for Sink {
#[inline]
fn poll_write(
self: Pin<&mut Self>,
_: &mut Context<'_>,
buf: &[u8],
) -> Poll<Result<usize, io::Error>> {
Poll::Ready(Ok(buf.len()))
}
#[inline]
fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
Poll::Ready(Ok(()))
}
#[inline]
fn poll_shutdown(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
Poll::Ready(Ok(()))
}
}
impl fmt::Debug for Sink {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.pad("Sink { .. }")
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn assert_unpin() {
crate::is_unpin::<Sink>();
}
}