1use crate::io::AsyncWrite;
2
3use bytes::Buf;
4use pin_project_lite::pin_project;
5use std::future::Future;
6use std::io;
7use std::marker::PhantomPinned;
8use std::pin::Pin;
9use std::task::{ready, Context, Poll};
10
11pin_project! {
12 /// A future to write some of the buffer to an `AsyncWrite`.
13 #[derive(Debug)]
14 #[must_use = "futures do nothing unless you `.await` or poll them"]
15 pub struct WriteBuf<'a, W, B> {
16 writer: &'a mut W,
17 buf: &'a mut B,
18 #[pin]
19 _pin: PhantomPinned,
20 }
21}
22
23/// Tries to write some bytes from the given `buf` to the writer in an
24/// asynchronous manner, returning a future.
25pub(crate) fn write_buf<'a, W, B>(writer: &'a mut W, buf: &'a mut B) -> WriteBuf<'a, W, B>
26where
27 W: AsyncWrite + Unpin,
28 B: Buf,
29{
30 WriteBuf {
31 writer,
32 buf,
33 _pin: PhantomPinned,
34 }
35}
36
37impl<W, B> Future for WriteBuf<'_, W, B>
38where
39 W: AsyncWrite + Unpin,
40 B: Buf,
41{
42 type Output = io::Result<usize>;
43
44 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
45 let me: Projection<'_, '_, W, B> = self.project();
46
47 if !me.buf.has_remaining() {
48 return Poll::Ready(Ok(0));
49 }
50
51 let n: usize = ready!(Pin::new(me.writer).poll_write(cx, me.buf.chunk()))?;
52 me.buf.advance(cnt:n);
53 Poll::Ready(Ok(n))
54 }
55}
56