#[unsafe(no_mangle)]pub extern "C" fn book_order_new(
order_side: OrderSideOptional,
price: Price,
size: Quantity,
order_id: u64,
) -> BookOrderFfi#[unsafe(no_mangle)]pub extern "C" fn book_order_new(
order_side: OrderSideOptional,
price: Price,
size: Quantity,
order_id: u64,
) -> BookOrderFfi