futures_util/io/
read_exact.rs

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1use crate::io::AsyncRead;
2use futures_core::future::Future;
3use futures_core::ready;
4use futures_core::task::{Context, Poll};
5use std::io;
6use std::mem;
7use 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"]
12pub struct ReadExact<'a, R: ?Sized> {
13    reader: &'a mut R,
14    buf: &'a mut [u8],
15}
16
17impl<R: ?Sized + Unpin> Unpin for ReadExact<'_, R> {}
18
19impl<'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
25impl<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 *self;
30        while !this.buf.is_empty() {
31            let n = ready!(Pin::new(&mut this.reader).poll_read(cx, this.buf))?;
32            {
33                let (_, rest) = mem::take(&mut this.buf).split_at_mut(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}
futures_util/io/read_exact.rs

futures_util/io/
read_exact.rs
