Rust+Hyper Shift_JIS でレスポンスを返却する

fn full<T: Into<Bytes>>(chunk: T) -> BoxBody {
    Full::new(chunk.into())
        .map_err(|never| match never {})
        .boxed()
}

fn index() -> Result<Response<BoxBody>> {
    let cow_of_shift_jis_u8 = SHIFT_JIS.encode("あいうえお"); // encoding_rs::SHIFT_JIS encoding-rs crate

    Ok(Response::builder()
        .header("Content-Type", "text/plain; charset=shift_jis")
        .status(StatusCode::OK)
        .body(full(cow_of_shift_jis_u8.0.into_owned().into_boxed_slice()))?)
}

into_owned で Vec＜u8＞ にして、into_boxed_slice で Box<[u8]> に変換