futures_util/io/
read_to_string.rs

Help
1use super::read_to_end::read_to_end_internal;
2use futures_core::future::Future;
3use futures_core::ready;
4use futures_core::task::{Context, Poll};
5use futures_io::AsyncRead;
6use std::pin::Pin;
7use std::vec::Vec;
8use std::{io, mem, str};
9
10/// Future for the [`read_to_string`](super::AsyncReadExt::read_to_string) method.
11#[derive(Debug)]
12#[must_use = "futures do nothing unless you `.await` or poll them"]
13pub struct ReadToString<'a, R: ?Sized> {
14    reader: &'a mut R,
15    buf: &'a mut String,
16    bytes: Vec<u8>,
17    start_len: usize,
18}
19
20impl<R: ?Sized + Unpin> Unpin for ReadToString<'_, R> {}
21
22impl<'a, R: AsyncRead + ?Sized + Unpin> ReadToString<'a, R> {
23    pub(super) fn new(reader: &'a mut R, buf: &'a mut String) -> Self {
24        let start_len = buf.len();
25        Self { reader, bytes: mem::take(buf).into_bytes(), buf, start_len }
26    }
27}
28
29fn read_to_string_internal<R: AsyncRead + ?Sized>(
30    reader: Pin<&mut R>,
31    cx: &mut Context<'_>,
32    buf: &mut String,
33    bytes: &mut Vec<u8>,
34    start_len: usize,
35) -> Poll<io::Result<usize>> {
36    let ret = ready!(read_to_end_internal(reader, cx, bytes, start_len));
37    if str::from_utf8(bytes).is_err() {
38        Poll::Ready(ret.and_then(|_| {
39            Err(io::Error::new(io::ErrorKind::InvalidData, "stream did not contain valid UTF-8"))
40        }))
41    } else {
42        debug_assert!(buf.is_empty());
43        // Safety: `bytes` is a valid UTF-8 because `str::from_utf8` returned `Ok`.
44        mem::swap(unsafe { buf.as_mut_vec() }, bytes);
45        Poll::Ready(ret)
46    }
47}
48
49impl<A> Future for ReadToString<'_, A>
50where
51    A: AsyncRead + ?Sized + Unpin,
52{
53    type Output = io::Result<usize>;
54
55    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
56        let Self { reader, buf, bytes, start_len } = &mut *self;
57        read_to_string_internal(Pin::new(reader), cx, buf, bytes, *start_len)
58    }
59}
futures_util/io/read_to_string.rs

futures_util/io/
read_to_string.rs
