io: add vectored writes to `AsyncWrite` (#3149)

This adds `AsyncWrite::poll_write_vectored`, and implements it for
`TcpStream` and `UnixStream`.

Refs: #3135.

1 files changed, 12 insertions, 0 deletions

diff --git a/tokio/src/net/tcp/split.rs b/tokio/src/net/tcp/split.rs
index 9a257f8b..28c94eb4 100644
--- a/tokio/src/net/tcp/split.rs
+++ b/tokio/src/net/tcp/split.rs
@@ -147,6 +147,18 @@ impl AsyncWrite for WriteHalf<'_> {
         self.0.poll_write_priv(cx, buf)
     }
 
+    fn poll_write_vectored(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        bufs: &[io::IoSlice<'_>],
+    ) -> Poll<io::Result<usize>> {
+        self.0.poll_write_vectored_priv(cx, bufs)
+    }
+
+    fn is_write_vectored(&self) -> bool {
+        self.0.is_write_vectored()
+    }
+
     #[inline]
     fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
         // tcp flush is a no-op