tokio/tokio-io/tests/copy.rs

#![deny(warnings, rust_2018_idioms)]
#![feature(async_await)]

use tokio_io::{AsyncRead, AsyncReadExt, AsyncWrite};
use tokio_test::assert_ok;

use bytes::BytesMut;
use std::io;
use std::pin::Pin;
use std::task::{Context, Poll};

#[tokio::test]
async fn copy() {
    struct Rd(bool);

    impl AsyncRead for Rd {
        fn poll_read(
            mut self: Pin<&mut Self>,
            _cx: &mut Context<'_>,
            buf: &mut [u8],
        ) -> Poll<io::Result<usize>> {
            if self.0 {
                buf[0..11].copy_from_slice(b"hello world");
                self.0 = false;
                Poll::Ready(Ok(11))
            } else {
                Poll::Ready(Ok(0))
            }
        }
    }

    struct Wr(BytesMut);

    impl Unpin for Wr {}
    impl AsyncWrite for Wr {
        fn poll_write(
            mut self: Pin<&mut Self>,
            _cx: &mut Context<'_>,
            buf: &[u8],
        ) -> Poll<io::Result<usize>> {
            self.0.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 buf = BytesMut::with_capacity(64);
    let mut rd = Rd(true);
    let mut wr = Wr(buf);

    let n = assert_ok!(rd.copy(&mut wr).await);
    assert_eq!(n, 11);
    assert_eq!(wr.0[..], b"hello world"[..]);
}