Function repurpose_allocation

src/ore/src/vec.rs:25–37

Create a new vector that re-uses the same allocation as an old one. The element types must have the same size and alignment.

(mut v: Vec<T1>)

/// Create a new vector that re-uses the same allocation as an old one.
/// The element types must have the same size and alignment.
pub fn repurpose_allocation<T1, T2>(mut v: Vec<T1>) -> Vec<T2> {
    assert_eq!(size_of::<T1>(), size_of::<T2>(), "same size");
    assert_eq!(align_of::<T1>(), align_of::<T2>(), "same alignment");

    v.clear();
    let cap = v.capacity();
    let p = v.as_mut_ptr().cast();
    std::mem::forget(v);
    // This is safe because `T1` and `T2` have the same size and alignment,
    // `p`'s allocation is no longer owned by `v` (since that has been forgotten),
    // and `p` was previously allocated with capacity `cap`.
    unsafe { Vec::from_raw_parts(p, 0, cap) }
}

/// A trait for objects that behave like vectors.
pub trait Vector<T> {