1use std::mem;
2use std::pin::Pin;
3use std::future::Future;
4
5use crate::io::{self, Read};
6use crate::task::{Context, Poll};
7
8#[doc(hidden)]
9#[allow(missing_debug_implementations)]
10pub struct ReadExactFuture<'a, T: Unpin + ?Sized> {
11 pub(crate) reader: &'a mut T,
12 pub(crate) buf: &'a mut [u8],
13}
14
15impl<T: Read + Unpin + ?Sized> Future for ReadExactFuture<'_, T> {
16 type Output = io::Result<()>;
17
18 fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
19 let Self { reader: &mut &mut T, buf: &mut &mut [u8] } = &mut *self;
20
21 while !buf.is_empty() {
22 let n: usize = futures_core::ready!(Pin::new(&mut *reader).poll_read(cx, buf))?;
23 let (_, rest: &mut [u8]) = mem::replace(buf, &mut []).split_at_mut(mid:n);
24 *buf = rest;
25
26 if n == 0 {
27 return Poll::Ready(Err(io::ErrorKind::UnexpectedEof.into()));
28 }
29 }
30
31 Poll::Ready(Ok(()))
32 }
33}
34