io: use Buf::put_bytes in Repeat read impl

tokio/src/io/util/repeat.rs

@@ -1,3 +1,5 @@
+use bytes::BufMut;
+
 use crate::io::util::poll_proceed_and_make_progress;
 use crate::io::{AsyncRead, ReadBuf};
 
@@ -56,10 +58,7 @@ impl AsyncRead for Repeat {
     ) -> Poll<io::Result<()>> {
         ready!(crate::trace::trace_leaf(cx));
         ready!(poll_proceed_and_make_progress(cx));
-        // TODO: could be faster, but should we unsafe it?
-        while buf.remaining() != 0 {
-            buf.put_slice(&[self.byte]);
-        }
+        buf.put_bytes(self.byte, buf.remaining());
         Poll::Ready(Ok(()))
     }
 }