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..a8ca370ea8
--- /dev/null
+++ b/third_party/rust/tokio/src/io/util/read.rs
@@ -0,0 +1,55 @@
+use crate::io::AsyncRead;
+
+use std::future::Future;
+use std::io;
+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 }
+}
+
+cfg_io_util! {
+    /// 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],
+    }
+}
+
+impl<R> Future for Read<'_, R>
+where
+    R: AsyncRead + Unpin + ?Sized,
+{
+    type Output = io::Result<usize>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
+        let me = &mut *self;
+        Pin::new(&mut *me.reader).poll_read(cx, me.buf)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn assert_unpin() {
+        use std::marker::PhantomPinned;
+        crate::is_unpin::<Read<'_, PhantomPinned>>();
+    }
+}