io: add `AsyncReadExt::read_buf` (#3003)

Brings back `read_buf` from 0.2. This will be stabilized as part of 1.0.

3 files changed, 113 insertions, 0 deletions

diff --git a/tokio/tests/io_read.rs b/tokio/tests/io_read.rs
index 29d7d6d7..cb1aa705 100644
--- a/tokio/tests/io_read.rs
+++ b/tokio/tests/io_read.rs
@@ -36,3 +36,24 @@ 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 ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
+        *buf = ReadBuf::new(Box::leak(vec![0; buf.capacity()].into_boxed_slice()));
+        buf.advance(buf.capacity());
+        Poll::Ready(Ok(()))
+    }
+}
+
+#[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();
+}
diff --git a/tokio/tests/io_read_buf.rs b/tokio/tests/io_read_buf.rs
new file mode 100644
index 00000000..0328168d
--- /dev/null
+++ b/tokio/tests/io_read_buf.rs
@@ -0,0 +1,36 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+
+use tokio::io::{AsyncRead, AsyncReadExt, ReadBuf};
+use tokio_test::assert_ok;
+
+use std::io;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+#[tokio::test]
+async fn read_buf() {
+    struct Rd {
+        cnt: usize,
+    }
+
+    impl AsyncRead for Rd {
+        fn poll_read(
+            mut self: Pin<&mut Self>,
+            _cx: &mut Context<'_>,
+            buf: &mut ReadBuf<'_>,
+        ) -> Poll<io::Result<()>> {
+            self.cnt += 1;
+            buf.put_slice(b"hello world");
+            Poll::Ready(Ok(()))
+        }
+    }
+
+    let mut buf = vec![];
+    let mut rd = Rd { cnt: 0 };
+
+    let n = assert_ok!(rd.read_buf(&mut buf).await);
+    assert_eq!(1, rd.cnt);
+    assert_eq!(n, 11);
+    assert_eq!(buf[..], b"hello world"[..]);
+}
diff --git a/tokio/tests/io_write_buf.rs b/tokio/tests/io_write_buf.rs
new file mode 100644
index 00000000..9ae655b6
--- /dev/null
+++ b/tokio/tests/io_write_buf.rs
@@ -0,0 +1,56 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+
+use tokio::io::{AsyncWrite, AsyncWriteExt};
+use tokio_test::assert_ok;
+
+use bytes::BytesMut;
+use std::cmp;
+use std::io::{self, Cursor};
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+#[tokio::test]
+async fn write_all() {
+    struct Wr {
+        buf: BytesMut,
+        cnt: usize,
+    }
+
+    impl AsyncWrite for Wr {
+        fn poll_write(
+            mut self: Pin<&mut Self>,
+            _cx: &mut Context<'_>,
+            buf: &[u8],
+        ) -> Poll<io::Result<usize>> {
+            assert_eq!(self.cnt, 0);
+
+            let n = cmp::min(4, buf.len());
+            let buf = &buf[0..n];
+
+            self.cnt += 1;
+            self.buf.extend(buf);
+            Ok(buf.len()).into()
+        }
+
+        fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+            Ok(()).into()
+        }
+
+        fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+            Ok(()).into()
+        }
+    }
+
+    let mut wr = Wr {
+        buf: BytesMut::with_capacity(64),
+        cnt: 0,
+    };
+
+    let mut buf = Cursor::new(&b"hello world"[..]);
+
+    assert_ok!(wr.write_buf(&mut buf).await);
+    assert_eq!(wr.buf, b"hell"[..]);
+    assert_eq!(wr.cnt, 1);
+    assert_eq!(buf.position(), 4);
+}