`slice_cell::SliceCell<T>` is much like `Cell<[T]>`, but with some additional features.
In particular, `&SliceCell<u8>` implements `std::io::Read` and `std::io::Write` (under the `"std"` cargo feature), and `slice_cell::io::Cursor<&SliceCell<u8>>` implements those as well as `std::io::Seek`.