1 files changed, 57 insertions, 0 deletions
diff --git a/third_party/rust/futures-util/src/io/read_line.rs b/third_party/rust/futures-util/src/io/read_line.rs
new file mode 100644
index 0000000000..e1b8fc9455
--- /dev/null
+++ b/third_party/rust/futures-util/src/io/read_line.rs
@@ -0,0 +1,57 @@
+use super::read_until::read_until_internal;
+use futures_core::future::Future;
+use futures_core::ready;
+use futures_core::task::{Context, Poll};
+use futures_io::AsyncBufRead;
+use std::io;
+use std::mem;
+use std::pin::Pin;
+use std::str;
+
+/// Future for the [`read_line`](super::AsyncBufReadExt::read_line) method.
+#[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
+pub struct ReadLine<'a, R: ?Sized> {
+    reader: &'a mut R,
+    buf: &'a mut String,
+    bytes: Vec<u8>,
+    read: usize,
+}
+
+impl<R: ?Sized + Unpin> Unpin for ReadLine<'_, R> {}
+
+impl<'a, R: AsyncBufRead + ?Sized + Unpin> ReadLine<'a, R> {
+    pub(super) fn new(reader: &'a mut R, buf: &'a mut String) -> Self {
+        Self { reader, bytes: mem::take(buf).into_bytes(), buf, read: 0 }
+    }
+}
+
+pub(super) fn read_line_internal<R: AsyncBufRead + ?Sized>(
+    reader: Pin<&mut R>,
+    cx: &mut Context<'_>,
+    buf: &mut String,
+    bytes: &mut Vec<u8>,
+    read: &mut usize,
+) -> Poll<io::Result<usize>> {
+    let ret = ready!(read_until_internal(reader, cx, b'\n', bytes, read));
+    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());
+        debug_assert_eq!(*read, 0);
+        // 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<R: AsyncBufRead + ?Sized + Unpin> Future for ReadLine<'_, R> {
+    type Output = io::Result<usize>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let Self { reader, buf, bytes, read } = &mut *self;
+        read_line_internal(Pin::new(reader), cx, buf, bytes, read)
+    }
+}