1 use super::read_to_end::read_to_end_internal;
2 use futures_core::ready;
3 use futures_core::future::Future;
4 use futures_core::task::{Context, Poll};
5 use futures_io::AsyncRead;
6 use std::pin::Pin;
7 use std::vec::Vec;
8 use 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"]
13 pub 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
20 impl<R: ?Sized + Unpin> Unpin for ReadToString<'_, R> {}
21
22 impl<'a, R: AsyncRead + ?Sized + Unpin> ReadToString<'a, R> {
new(reader: &'a mut R, buf: &'a mut String) -> Self23 pub(super) fn new(reader: &'a mut R, buf: &'a mut String) -> Self {
24 let start_len = buf.len();
25 Self {
26 reader,
27 bytes: mem::replace(buf, String::new()).into_bytes(),
28 buf,
29 start_len,
30 }
31 }
32 }
33
read_to_string_internal<R: AsyncRead + ?Sized>( reader: Pin<&mut R>, cx: &mut Context<'_>, buf: &mut String, bytes: &mut Vec<u8>, start_len: usize, ) -> Poll<io::Result<usize>>34 fn read_to_string_internal<R: AsyncRead + ?Sized>(
35 reader: Pin<&mut R>,
36 cx: &mut Context<'_>,
37 buf: &mut String,
38 bytes: &mut Vec<u8>,
39 start_len: usize,
40 ) -> Poll<io::Result<usize>> {
41 let ret = ready!(read_to_end_internal(reader, cx, bytes, start_len));
42 if str::from_utf8(bytes).is_err() {
43 Poll::Ready(ret.and_then(|_| {
44 Err(io::Error::new(
45 io::ErrorKind::InvalidData,
46 "stream did not contain valid UTF-8",
47 ))
48 }))
49 } else {
50 debug_assert!(buf.is_empty());
51 // Safety: `bytes` is a valid UTF-8 because `str::from_utf8` returned `Ok`.
52 mem::swap(unsafe { buf.as_mut_vec() }, bytes);
53 Poll::Ready(ret)
54 }
55 }
56
57 impl<A> Future for ReadToString<'_, A>
58 where
59 A: AsyncRead + ?Sized + Unpin,
60 {
61 type Output = io::Result<usize>;
62
poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>63 fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
64 let Self { reader, buf, bytes, start_len } = &mut *self;
65 read_to_string_internal(Pin::new(reader), cx, buf, bytes, *start_len)
66 }
67 }
68