tokio: move I/O helpers to ext traits (#1204)

Refs: #1203

1 files changed, 46 insertions, 0 deletions

diff --git a/tokio/tests/io_read_exact.rs b/tokio/tests/io_read_exact.rs
new file mode 100644
index 00000000..94e35514
--- /dev/null
+++ b/tokio/tests/io_read_exact.rs
@@ -0,0 +1,46 @@
+#![deny(warnings, rust_2018_idioms)]
+
+use tokio::io::{AsyncRead, AsyncReadExt};
+use tokio_test::assert_ready_ok;
+use tokio_test::task::MockTask;
+
+use pin_utils::pin_mut;
+use std::future::Future;
+use std::io;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+#[test]
+fn read_exact() {
+    struct Rd {
+        val: &'static [u8; 11],
+    }
+
+    impl AsyncRead for Rd {
+        fn poll_read(
+            mut self: Pin<&mut Self>,
+            _cx: &mut Context<'_>,
+            buf: &mut [u8]
+        ) -> Poll<io::Result<usize>> {
+            let me = &mut *self;
+            let len = buf.len();
+
+            buf[..].copy_from_slice(&me.val[..len]);
+            Poll::Ready(Ok(buf.len()))
+        }
+    }
+
+    let mut buf = Box::new([0; 8]);
+    let mut task = MockTask::new();
+
+    task.enter(|cx| {
+        let mut rd = Rd { val: b"hello world" };
+
+        let read = rd.read_exact(&mut buf[..]);
+        pin_mut!(read);
+
+        let n = assert_ready_ok!(read.poll(cx));
+        assert_eq!(n, 8);
+        assert_eq!(buf[..], b"hello wo"[..]);
+    });
+}