1 | use crate::io::AsyncRead; |
2 | use futures_core::future::Future; |
3 | use futures_core::ready; |
4 | use futures_core::task::{Context, Poll}; |
5 | use std::io; |
6 | use std::mem; |
7 | use std::pin::Pin; |
8 | |
9 | /// Future for the [`read_exact`](super::AsyncReadExt::read_exact) method. |
10 | #[derive (Debug)] |
11 | #[must_use = "futures do nothing unless you `.await` or poll them" ] |
12 | pub struct ReadExact<'a, R: ?Sized> { |
13 | reader: &'a mut R, |
14 | buf: &'a mut [u8], |
15 | } |
16 | |
17 | impl<R: ?Sized + Unpin> Unpin for ReadExact<'_, R> {} |
18 | |
19 | impl<'a, R: AsyncRead + ?Sized + Unpin> ReadExact<'a, R> { |
20 | pub(super) fn new(reader: &'a mut R, buf: &'a mut [u8]) -> Self { |
21 | Self { reader, buf } |
22 | } |
23 | } |
24 | |
25 | impl<R: AsyncRead + ?Sized + Unpin> Future for ReadExact<'_, R> { |
26 | type Output = io::Result<()>; |
27 | |
28 | fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { |
29 | let this: &mut ReadExact<'_, R> = &mut *self; |
30 | while !this.buf.is_empty() { |
31 | let n: usize = ready!(Pin::new(&mut this.reader).poll_read(cx, this.buf))?; |
32 | { |
33 | let (_, rest: &mut [u8]) = mem::take(&mut this.buf).split_at_mut(mid:n); |
34 | this.buf = rest; |
35 | } |
36 | if n == 0 { |
37 | return Poll::Ready(Err(io::ErrorKind::UnexpectedEof.into())); |
38 | } |
39 | } |
40 | Poll::Ready(Ok(())) |
41 | } |
42 | } |
43 | |