1 files changed, 72 insertions, 0 deletions
diff --git a/third_party/rust/tokio/src/io/util/repeat.rs b/third_party/rust/tokio/src/io/util/repeat.rs
new file mode 100644
index 0000000000..1142765df5
--- /dev/null
+++ b/third_party/rust/tokio/src/io/util/repeat.rs
@@ -0,0 +1,72 @@
+use crate::io::{AsyncRead, ReadBuf};
+
+use std::io;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+cfg_io_util! {
+    /// An async reader which yields one byte over and over and over and over and
+    /// over and...
+    ///
+    /// This struct is generally created by calling [`repeat`][repeat]. Please
+    /// see the documentation of `repeat()` for more details.
+    ///
+    /// This is an asynchronous version of [`std::io::Repeat`][std].
+    ///
+    /// [repeat]: fn@repeat
+    /// [std]: std::io::Repeat
+    #[derive(Debug)]
+    pub struct Repeat {
+        byte: u8,
+    }
+
+    /// Creates an instance of an async reader that infinitely repeats one byte.
+    ///
+    /// All reads from this reader will succeed by filling the specified buffer with
+    /// the given byte.
+    ///
+    /// This is an asynchronous version of [`std::io::repeat`][std].
+    ///
+    /// [std]: std::io::repeat
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use tokio::io::{self, AsyncReadExt};
+    ///
+    /// #[tokio::main]
+    /// async fn main() {
+    ///     let mut buffer = [0; 3];
+    ///     io::repeat(0b101).read_exact(&mut buffer).await.unwrap();
+    ///     assert_eq!(buffer, [0b101, 0b101, 0b101]);
+    /// }
+    /// ```
+    pub fn repeat(byte: u8) -> Repeat {
+        Repeat { byte }
+    }
+}
+
+impl AsyncRead for Repeat {
+    #[inline]
+    fn poll_read(
+        self: Pin<&mut Self>,
+        _: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
+        // TODO: could be faster, but should we unsafe it?
+        while buf.remaining() != 0 {
+            buf.put_slice(&[self.byte]);
+        }
+        Poll::Ready(Ok(()))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn assert_unpin() {
+        crate::is_unpin::<Repeat>();
+    }
+}