1 files changed, 74 insertions, 0 deletions
diff --git a/third_party/rust/tokio/src/net/unix/split.rs b/third_party/rust/tokio/src/net/unix/split.rs
new file mode 100644
index 0000000000..9b9fa5ee1d
--- /dev/null
+++ b/third_party/rust/tokio/src/net/unix/split.rs
@@ -0,0 +1,74 @@
+//! `UnixStream` split support.
+//!
+//! A `UnixStream` can be split into a read half and a write half with
+//! `UnixStream::split`. The read half implements `AsyncRead` while the write
+//! half implements `AsyncWrite`.
+//!
+//! Compared to the generic split of `AsyncRead + AsyncWrite`, this specialized
+//! split has no associated overhead and enforces all invariants at the type
+//! level.
+
+use crate::io::{AsyncRead, AsyncWrite};
+use crate::net::UnixStream;
+
+use std::io;
+use std::mem::MaybeUninit;
+use std::net::Shutdown;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+/// Read half of a `UnixStream`.
+#[derive(Debug)]
+pub struct ReadHalf<'a>(&'a UnixStream);
+
+/// Write half of a `UnixStream`.
+#[derive(Debug)]
+pub struct WriteHalf<'a>(&'a UnixStream);
+
+pub(crate) fn split(stream: &mut UnixStream) -> (ReadHalf<'_>, WriteHalf<'_>) {
+    (ReadHalf(stream), WriteHalf(stream))
+}
+
+impl AsyncRead for ReadHalf<'_> {
+    unsafe fn prepare_uninitialized_buffer(&self, _: &mut [MaybeUninit<u8>]) -> bool {
+        false
+    }
+
+    fn poll_read(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut [u8],
+    ) -> Poll<io::Result<usize>> {
+        self.0.poll_read_priv(cx, buf)
+    }
+}
+
+impl AsyncWrite for WriteHalf<'_> {
+    fn poll_write(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        self.0.poll_write_priv(cx, buf)
+    }
+
+    fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+
+    fn poll_shutdown(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
+        self.0.shutdown(Shutdown::Write).into()
+    }
+}
+
+impl AsRef<UnixStream> for ReadHalf<'_> {
+    fn as_ref(&self) -> &UnixStream {
+        self.0
+    }
+}
+
+impl AsRef<UnixStream> for WriteHalf<'_> {
+    fn as_ref(&self) -> &UnixStream {
+        self.0
+    }
+}