io: implement AsyncWrite for Vec<u8> (#1409)

tokio-io/src/async_write.rs

@@ -190,3 +190,22 @@ where
         self.get_mut().as_mut().poll_shutdown(cx)
     }
 }
+
+impl AsyncWrite for Vec<u8> {
+    fn poll_write(
+        self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        self.get_mut().extend_from_slice(buf);
+        Poll::Ready(Ok(buf.len()))
+    }
+
+    fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+
+    fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+}