Crate addr_of_enum

addr_of_enum

This crate provides #[derive(AddrOfEnum)] and addr_of_enum! macro to get a field pointer of specified variant without creating an intermediated reference. It works like std::ptr::addr_of!, but works only on enums.

This macro is zero-cost, which means that it calculates without minimum cost in release mode.

It also works on variables which has uninhabited types.

Example

#[derive(AddrOfEnum)]
#[repr(C)]
enum MyEnum {
    E1(usize, u8),
    E2 {
        item1: u32,
        item2: u8,
    }
}

let e = MyEnum::E1(1, 2);
let _: *const usize = addr_of_enum!(&e, E1, 0);
let _: *const u32 = addr_of_enum!(&e, E2, item1);

Limitations

For now, the macros cannot be used in const context.

Macros

• addr_of_enum
  See crate level documentation
• get_discriminant

Traits

• AddrOfEnum
  This trait is implemented with #[derive(AddrOfEnum)]

Derive Macros

• AddrOfEnum
  This macro impls AddrOfEnum trait. It works only on enums.