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use crate::io::util::read_to_end::read_to_end_internal;
use crate::io::AsyncRead;
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};
use std::{io, mem, str};
/// Future for the [`read_to_string`](super::AsyncReadExt::read_to_string) method.
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct ReadToString<'a, R: ?Sized> {
reader: &'a mut R,
buf: &'a mut String,
bytes: Vec<u8>,
start_len: usize,
}
pub(crate) fn read_to_string<'a, R>(reader: &'a mut R, buf: &'a mut String) -> ReadToString<'a, R>
where
R: AsyncRead + ?Sized + Unpin,
{
let start_len = buf.len();
ReadToString {
reader,
bytes: unsafe { mem::replace(buf.as_mut_vec(), Vec::new()) },
buf,
start_len,
}
}
fn 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>> {
let ret = ready!(read_to_end_internal(reader, cx, bytes, start_len));
if str::from_utf8(&bytes).is_err() {
Poll::Ready(ret.and_then(|_| {
Err(io::Error::new(
io::ErrorKind::InvalidData,
"stream did not contain valid UTF-8",
))
}))
} else {
debug_assert!(buf.is_empty());
// Safety: `bytes` is a valid UTF-8 because `str::from_utf8` returned `Ok`.
mem::swap(unsafe { buf.as_mut_vec() }, bytes);
Poll::Ready(ret)
}
}
impl<A> Future for ReadToString<'_, A>
where
A: AsyncRead + ?Sized + Unpin,
{
type Output = io::Result<usize>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let Self {
reader,
buf,
bytes,
start_len,
} = &mut *self;
read_to_string_internal(Pin::new(reader), cx, buf, bytes, *start_len)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn assert_unpin() {
use std::marker::PhantomPinned;
crate::is_unpin::<ReadToString<'_, PhantomPinned>>();
}
}
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