1 files changed, 55 insertions, 0 deletions
diff --git a/third_party/rust/tokio/src/io/util/read.rs b/third_party/rust/tokio/src/io/util/read.rs
new file mode 100644
index 0000000000..edc9d5a9e6
--- /dev/null
+++ b/third_party/rust/tokio/src/io/util/read.rs
@@ -0,0 +1,55 @@
+use crate::io::{AsyncRead, ReadBuf};
+
+use pin_project_lite::pin_project;
+use std::future::Future;
+use std::io;
+use std::marker::PhantomPinned;
+use std::marker::Unpin;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+/// Tries to read some bytes directly into the given `buf` in asynchronous
+/// manner, returning a future type.
+///
+/// The returned future will resolve to both the I/O stream and the buffer
+/// as well as the number of bytes read once the read operation is completed.
+pub(crate) fn read<'a, R>(reader: &'a mut R, buf: &'a mut [u8]) -> Read<'a, R>
+where
+    R: AsyncRead + Unpin + ?Sized,
+{
+    Read {
+        reader,
+        buf,
+        _pin: PhantomPinned,
+    }
+}
+
+pin_project! {
+    /// A future which can be used to easily read available number of bytes to fill
+    /// a buffer.
+    ///
+    /// Created by the [`read`] function.
+    #[derive(Debug)]
+    #[must_use = "futures do nothing unless you `.await` or poll them"]
+    pub struct Read<'a, R: ?Sized> {
+        reader: &'a mut R,
+        buf: &'a mut [u8],
+        // Make this future `!Unpin` for compatibility with async trait methods.
+        #[pin]
+        _pin: PhantomPinned,
+    }
+}
+
+impl<R> Future for Read<'_, R>
+where
+    R: AsyncRead + Unpin + ?Sized,
+{
+    type Output = io::Result<usize>;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
+        let me = self.project();
+        let mut buf = ReadBuf::new(*me.buf);
+        ready!(Pin::new(me.reader).poll_read(cx, &mut buf))?;
+        Poll::Ready(Ok(buf.filled().len()))
+    }
+}