tokio/io/util/
read.rs

1use crate::io::{AsyncRead, ReadBuf};
2
3use pin_project_lite::pin_project;
4use std::future::Future;
5use std::io;
6use std::marker::PhantomPinned;
7use std::marker::Unpin;
8use std::pin::Pin;
9use std::task::{ready, Context, Poll};
10
11/// Tries to read some bytes directly into the given `buf` in asynchronous
12/// manner, returning a future type.
13///
14/// The returned future will resolve to both the I/O stream and the buffer
15/// as well as the number of bytes read once the read operation is completed.
16pub(crate) fn read<'a, R>(reader: &'a mut R, buf: &'a mut [u8]) -> Read<'a, R>
17where
18    R: AsyncRead + Unpin + ?Sized,
19{
20    Read {
21        reader,
22        buf,
23        _pin: PhantomPinned,
24    }
25}
26
27pin_project! {
28    /// A future which can be used to easily read available number of bytes to fill
29    /// a buffer.
30    ///
31    /// Created by the [`read`] function.
32    #[derive(Debug)]
33    #[must_use = "futures do nothing unless you `.await` or poll them"]
34    pub struct Read<'a, R: ?Sized> {
35        reader: &'a mut R,
36        buf: &'a mut [u8],
37        // Make this future `!Unpin` for compatibility with async trait methods.
38        #[pin]
39        _pin: PhantomPinned,
40    }
41}
42
43impl<R> Future for Read<'_, R>
44where
45    R: AsyncRead + Unpin + ?Sized,
46{
47    type Output = io::Result<usize>;
48
49    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
50        let me = self.project();
51        let mut buf = ReadBuf::new(me.buf);
52        ready!(Pin::new(me.reader).poll_read(cx, &mut buf))?;
53        Poll::Ready(Ok(buf.filled().len()))
54    }
55}
tokio/io/util/read.rs

tokio/io/util/
read.rs
