process: expose AW::poll_write_vectored on unix

tokio/src/io/poll_evented.rs

@@ -208,7 +208,7 @@ feature! {
             }
         }
 
-        #[cfg(feature = "net")]
+        #[cfg(any(feature = "net", feature = "process"))]
         pub(crate) fn poll_write_vectored<'a>(
             &'a self,
             cx: &mut Context<'_>,

tokio/src/process/mod.rs

@@ -1329,6 +1329,18 @@ impl AsyncWrite for ChildStdin {
     fn poll_shutdown(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
         Pin::new(&mut self.inner).poll_shutdown(cx)
     }
+
+    fn poll_write_vectored(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        bufs: &[io::IoSlice<'_>],
+    ) -> Poll<Result<usize, io::Error>> {
+        Pin::new(&mut self.inner).poll_write_vectored(cx, bufs)
+    }
+
+    fn is_write_vectored(&self) -> bool {
+        self.inner.is_write_vectored()
+    }
 }
 
 impl AsyncRead for ChildStdout {

tokio/src/process/unix/mod.rs

@@ -182,6 +182,10 @@ impl<'a> io::Write for &'a Pipe {
     fn flush(&mut self) -> io::Result<()> {
         (&self.fd).flush()
     }
+
+    fn write_vectored(&mut self, bufs: &[io::IoSlice<'_>]) -> io::Result<usize> {
+        (&self.fd).write_vectored(bufs)
+    }
 }
 
 impl AsRawFd for Pipe {
@@ -258,6 +262,18 @@ impl AsyncWrite for ChildStdio {
     fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
         Poll::Ready(Ok(()))
     }
+
+    fn poll_write_vectored(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        bufs: &[io::IoSlice<'_>],
+    ) -> Poll<Result<usize, io::Error>> {
+        self.inner.poll_write_vectored(cx, bufs)
+    }
+
+    fn is_write_vectored(&self) -> bool {
+        true
+    }
 }
 
 impl AsyncRead for ChildStdio {