Macro project_uninit::project_ptr_mut

macro_rules! project_ptr_mut {
    ($expr:expr => {$( $($props:tt)=>+ ),* $(,)?}) => { ... };
    ($expr:expr => $($props:tt)=>+) => { ... };
}

Unsafe: Given a *mut pointer to a struct, obtain *mut pointers to one or more of its fields.

This does not statically check whether multiple pointers to the same data are returned. This must be used in an unsafe block or function.

Usage

let mut bob = Person {
    name: Name { first: "Bob", last: "Jones" },
    age: 35,
    id: (111, 222),
};
let bob_ptr: *mut Person = &mut bob;

unsafe {
    // Pointer to a single field:
    let age: *mut u32 = project_ptr_mut!(bob_ptr => age);
    *age = 36;

    // Pointers to multiple fields:
    let (first, last, id0): (*mut &str, *mut &str, *mut usize) = project_ptr_mut!(
        bob_ptr => { name => first, name => last, id => 0 }
    );
    *first = "Robert";
    *last = "Johns";
    *id0 = 444;
    assert_eq!(bob, Person {
        name: Name { first: "Robert", last: "Johns" },
        age: 36,
        id: (444, 222),
    });
}