// One downside of the way we have implemented enum support so far is that it // makes it impossible to see from the definition of a bitfield struct how the // bits are being laid out. In something like the following bitfield, all we // know from this code is that the total size is a multiple of 8 bits. Maybe // trigger_mode is 11 bits and delivery_mode is 1 bit. This may tend to make // maintenance problematic when the types involved are defined across different // modules or even different crates. // // #[bitfield] // pub struct RedirectionTableEntry { // trigger_mode: TriggerMode, // delivery_mode: DeliveryMode, // reserved: B4, // } // // Introduce an optional #[bits = N] attribute to serve as compile-time checked // documentation of field size. Ensure that this attribute is entirely optional, // meaning that the code behaves the same whether or not you write it, but if // the user does provide the attribute then the program must not compile if // their value is wrong. use modular_bitfield::prelude::*; #[bitfield] pub struct RedirectionTableEntry { #[bits = 1] trigger_mode: TriggerMode, #[bits = 3] delivery_mode: DeliveryMode, reserved: B4, } #[derive(BitfieldSpecifier, Debug)] pub enum TriggerMode { Edge = 0, Level = 1, } #[derive(BitfieldSpecifier, Debug)] pub enum DeliveryMode { Fixed = 0b000, Lowest = 0b001, SMI = 0b010, RemoteRead = 0b011, NMI = 0b100, Init = 0b101, Startup = 0b110, External = 0b111, } fn main() {}