io: change AsyncRead to use a ReadBuf (#2758)

Works towards #2716. Changes the argument to `AsyncRead::poll_read` to
take a `ReadBuf` struct that safely manages writes to uninitialized memory.

1 files changed, 5 insertions, 27 deletions

diff --git a/tokio/tests/io_read.rs b/tokio/tests/io_read.rs
index 4791c9a6..0a717cf5 100644
--- a/tokio/tests/io_read.rs
+++ b/tokio/tests/io_read.rs
@@ -1,7 +1,7 @@
 #![warn(rust_2018_idioms)]
 #![cfg(feature = "full")]
 
-use tokio::io::{AsyncRead, AsyncReadExt};
+use tokio::io::{AsyncRead, AsyncReadExt, ReadBuf};
 use tokio_test::assert_ok;
 
 use std::io;
@@ -19,13 +19,13 @@ async fn read() {
         fn poll_read(
             mut self: Pin<&mut Self>,
             _cx: &mut Context<'_>,
-            buf: &mut [u8],
-        ) -> Poll<io::Result<usize>> {
+            buf: &mut ReadBuf<'_>,
+        ) -> Poll<io::Result<()>> {
             assert_eq!(0, self.poll_cnt);
             self.poll_cnt += 1;
 
-            buf[0..11].copy_from_slice(b"hello world");
-            Poll::Ready(Ok(11))
+            buf.append(b"hello world");
+            Poll::Ready(Ok(()))
         }
     }
 
@@ -36,25 +36,3 @@ async fn read() {
     assert_eq!(n, 11);
     assert_eq!(buf[..], b"hello world"[..]);
 }
-
-struct BadAsyncRead;
-
-impl AsyncRead for BadAsyncRead {
-    fn poll_read(
-        self: Pin<&mut Self>,
-        _cx: &mut Context<'_>,
-        buf: &mut [u8],
-    ) -> Poll<io::Result<usize>> {
-        for b in &mut *buf {
-            *b = b'a';
-        }
-        Poll::Ready(Ok(buf.len() * 2))
-    }
-}
-
-#[tokio::test]
-#[should_panic]
-async fn read_buf_bad_async_read() {
-    let mut buf = Vec::with_capacity(10);
-    BadAsyncRead.read_buf(&mut buf).await.unwrap();
-}