1 files changed, 67 insertions, 0 deletions
diff --git a/third_party/rust/futures-util/src/io/sink.rs b/third_party/rust/futures-util/src/io/sink.rs
new file mode 100644
index 0000000000..4a32ca7041
--- /dev/null
+++ b/third_party/rust/futures-util/src/io/sink.rs
@@ -0,0 +1,67 @@
+use futures_core::task::{Context, Poll};
+use futures_io::{AsyncWrite, IoSlice};
+use std::fmt;
+use std::io;
+use std::pin::Pin;
+
+/// Writer for the [`sink()`] function.
+#[must_use = "writers do nothing unless polled"]
+pub struct Sink {
+    _priv: (),
+}
+
+/// Creates an instance of a 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.
+///
+/// # Examples
+///
+/// ```rust
+/// # futures::executor::block_on(async {
+/// use futures::io::{self, AsyncWriteExt};
+///
+/// let buffer = vec![1, 2, 3, 5, 8];
+/// let mut writer = io::sink();
+/// let num_bytes = writer.write(&buffer).await?;
+/// assert_eq!(num_bytes, 5);
+/// # Ok::<(), Box<dyn std::error::Error>>(()) }).unwrap();
+/// ```
+pub fn sink() -> Sink {
+    Sink { _priv: () }
+}
+
+impl AsyncWrite for Sink {
+    #[inline]
+    fn poll_write(
+        self: Pin<&mut Self>,
+        _: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        Poll::Ready(Ok(buf.len()))
+    }
+
+    #[inline]
+    fn poll_write_vectored(
+        self: Pin<&mut Self>,
+        _: &mut Context<'_>,
+        bufs: &[IoSlice<'_>],
+    ) -> Poll<io::Result<usize>> {
+        Poll::Ready(Ok(bufs.iter().map(|b| b.len()).sum()))
+    }
+
+    #[inline]
+    fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+    #[inline]
+    fn poll_close(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+}
+
+impl fmt::Debug for Sink {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("Sink { .. }")
+    }
+}