Crate struct_layout

Learn by example, for a detailed description see the readme.

Examples

Most simple example, specify the required size and alignment and annotate the fields with an offset. Use zeroed to create an instance and use the generated accessors to access the field.

#[struct_layout::explicit(size = 16, align = 4)]
struct Foo {
    #[field(offset = 4)]
    field: i32,
}

let mut foo: Foo = unsafe { std::mem::zeroed() };

foo.set_field(13);
assert_eq!(foo.field(), 13);

*foo.field_mut() = 42;
assert_eq!(foo.field_ref(), &42);

Auto derive traits

Minimal set of whitelisted auto derived traits are supported.

Don't forget you can implement additional methods and traits on the generated type!

#[struct_layout::explicit(size = 16, align = 4)]
#[derive(Copy, Clone, Debug, Default)]
struct Foo {
    #[field(offset = 4)]
    field: char,
}

let mut foo = Foo::default().clone();
let _ = foo;
foo.set_field('a');
assert_eq!(format!("{:?}", foo), "Foo { field: 'a' }");

Check argument to ensure safety

The check attribute requires that all fields meet this trait bound. It is meant to support custom pod-like traits to ensure safe usage of the explicit attribute.

unsafe trait Pod {}
unsafe impl Pod for i32 {}

#[struct_layout::explicit(size = 16, align = 4, check(Pod))]
struct Foo {
    #[field(offset = 4)]
    field: i32,
}

Unaligned fields

Annotate a field with get or set accessors allows unaligned fields.

#[struct_layout::explicit(size = 16, align = 4)]
struct Foo {
    #[field(offset = 3, get, set)]
    field: i64,
}

Attribute Macros

explicit

Explicit field layout attribute.