chore: checkpoint before Python removal

vendor/tokio/tests/duplex_stream.rs

@@ -0,0 +1,47 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+
+use std::io::IoSlice;
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+
+const HELLO: &[u8] = b"hello world...";
+
+#[tokio::test]
+async fn write_vectored() {
+    let (mut client, mut server) = tokio::io::duplex(64);
+
+    let ret = client
+        .write_vectored(&[IoSlice::new(HELLO), IoSlice::new(HELLO)])
+        .await
+        .unwrap();
+    assert_eq!(ret, HELLO.len() * 2);
+
+    client.flush().await.unwrap();
+    drop(client);
+
+    let mut buf = Vec::with_capacity(HELLO.len() * 2);
+    let bytes_read = server.read_to_end(&mut buf).await.unwrap();
+
+    assert_eq!(bytes_read, HELLO.len() * 2);
+    assert_eq!(buf, [HELLO, HELLO].concat());
+}
+
+#[tokio::test]
+async fn write_vectored_and_shutdown() {
+    let (mut client, mut server) = tokio::io::duplex(64);
+
+    let ret = client
+        .write_vectored(&[IoSlice::new(HELLO), IoSlice::new(HELLO)])
+        .await
+        .unwrap();
+    assert_eq!(ret, HELLO.len() * 2);
+
+    client.shutdown().await.unwrap();
+    drop(client);
+
+    let mut buf = Vec::with_capacity(HELLO.len() * 2);
+    let bytes_read = server.read_to_end(&mut buf).await.unwrap();
+
+    assert_eq!(bytes_read, HELLO.len() * 2);
+    assert_eq!(buf, [HELLO, HELLO].concat());
+}