1 | use futures_core::future::Future; |
2 | use futures_core::task::{Context, Poll}; |
3 | use futures_io::AsyncBufRead; |
4 | use std::io; |
5 | use std::pin::Pin; |
6 | |
7 | /// Future for the [`fill_buf`](super::AsyncBufReadExt::fill_buf) method. |
8 | #[derive (Debug)] |
9 | #[must_use = "futures do nothing unless you `.await` or poll them" ] |
10 | pub struct FillBuf<'a, R: ?Sized> { |
11 | reader: Option<&'a mut R>, |
12 | } |
13 | |
14 | impl<R: ?Sized> Unpin for FillBuf<'_, R> {} |
15 | |
16 | impl<'a, R: AsyncBufRead + ?Sized + Unpin> FillBuf<'a, R> { |
17 | pub(super) fn new(reader: &'a mut R) -> Self { |
18 | Self { reader: Some(reader) } |
19 | } |
20 | } |
21 | |
22 | impl<'a, R> Future for FillBuf<'a, R> |
23 | where |
24 | R: AsyncBufRead + ?Sized + Unpin, |
25 | { |
26 | type Output = io::Result<&'a [u8]>; |
27 | |
28 | fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { |
29 | let this = &mut *self; |
30 | let reader = this.reader.take().expect("Polled FillBuf after completion" ); |
31 | |
32 | match Pin::new(&mut *reader).poll_fill_buf(cx) { |
33 | // With polonius it is possible to remove this inner match and just have the correct |
34 | // lifetime of the reference inferred based on which branch is taken |
35 | Poll::Ready(Ok(_)) => match Pin::new(reader).poll_fill_buf(cx) { |
36 | Poll::Ready(Ok(slice)) => Poll::Ready(Ok(slice)), |
37 | Poll::Ready(Err(err)) => { |
38 | unreachable!("reader indicated readiness but then returned an error: {:?}" , err) |
39 | } |
40 | Poll::Pending => { |
41 | unreachable!("reader indicated readiness but then returned pending" ) |
42 | } |
43 | }, |
44 | Poll::Ready(Err(err)) => Poll::Ready(Err(err)), |
45 | Poll::Pending => { |
46 | this.reader = Some(reader); |
47 | Poll::Pending |
48 | } |
49 | } |
50 | } |
51 | } |
52 | |