Macro dungeon_cell::layout_for

macro_rules! layout_for {
    ($($type:ty),* $(,)?) => { ... };
    ($($t:tt)*) => { ... };
}

Calculate the Layout needed to store a set of types.

This macro expects input of the form layout_for!(Type1, Type2, Type3). The created Layout type will have a size equal to the maximum size of the given types, and will have an alignment equal to the maximum alignment of the given types. If you want the layout for the combination of types Type1, Type2, Type3 as one value then use layout_for!((Type1, Type2, Type3)).

Examples

use dungeon_cell::layout_for;

// sizes

assert_eq!(<layout_for!()>::size(), 0);
assert_eq!(<layout_for!(())>::size(), 0);

assert_eq!(<layout_for!(u8)>::size(), 1);
assert_eq!(<layout_for!(u8, i8)>::size(), 1);

assert_eq!(<layout_for!(u32)>::size(), 4);
assert_eq!(<layout_for!(u32, i32, u8, i16, ())>::size(), 4);

assert_eq!(<layout_for!(u32, u8, String, &'static str, ())>::size(), 24);

assert_eq!(<layout_for!([u8; 100], [i32; 5], String)>::size(), 100);


// alignments

assert_eq!(<layout_for!()>::alignment(), 1);
assert_eq!(<layout_for!(u8)>::alignment(), 1);

assert_eq!(<layout_for!(i32)>::alignment(), 4);

assert_eq!(<layout_for!([u8; 100], [i32; 5], String)>::alignment(), 8);

Example Expansion

layout_for!(i32, u8)

expands to

::dungeon_cell::Layout<
    ::dungeon_cell::Size<
        {
            let mut max = 0;

            let size = ::core::mem::size_of::<i32>();
            if size > max {
                max = size;
            }

            let size = ::core::mem::size_of::<u8>();
            if size > max {
                max = size;
            }

            max
        },
    >,
    ::dungeon_cell::Alignment<
        {
            let mut max = 1;

            let align = ::core::mem::align_of::<i32>();
            if align > max {
                max = align;
            }

            let align = ::core::mem::align_of::<u8>();
            if align > max {
                max = align;
            }

            max
        },
    >,
>