fnum

Fnum is an utility trait for enum, that provides size_of_variant method. size_of_variant returns the minimum size that specified variant requiring.

And fnum has some functions:

• variant_count: Returns the number of variants the enum has.
• variant_index: Returns the index of variant.
• uninit_variant: Create an enum value that has uninitialized fields.

Usage

use fnum::Fnum;

#[derive(Fnum)]
enum MyEnum {
    A(u64),
    B(String),
    C(u64, u32, u32, u32),
    D {
        foo: u32,
        bar: String,
    }
}

fn main() {
    dbg!(MyEnum::size_of_variant(0)); // => 16 (bytes required by `MyEnum::A(..)`)
    dbg!(MyEnum::size_of_variant(1)); // => 32 (bytes required by `MyEnum::B(..)`)
    dbg!(MyEnum::size_of_variant(2)); // => 24 (bytes required by `MyEnum::C(..)`)
    dbg!(MyEnum::size_of_variant(3)); // => 32 (bytes required by `MyEnum::D{..}`)
}

Related products

• fnumbuf

Author

• carrotflakes (carrotflakes@gmail.com)

Copyright

Copyright (c) 2020 carrotflakes (carrotflakes@gmail.com)

License

Licensed under the MIT License.