subst/
non_aliasing.rs

1use core::mem::MaybeUninit;
2
3/// Simple wrapper around [`MaybeUninit`] that guarantees the type is initialized.
4///
5/// This may sound odd, but the compiler can not assume that `MaybeUninit` is initialized,
6/// but as far is the compiler is concerned, `MaybeUninit<T>` is not keeping any references around, even if `T` would.
7/// So `NonAliasing<T>` is not aliassing anything untill you call `inner()` to get your `&T` back.
8///
9/// We use this to create a (hopefully) sound self referential struct in `TemplateBuf` and `ByteTemplateBuf`.
10pub struct NonAliasing<T> {
11	inner: MaybeUninit<T>,
12}
13
14impl<T> NonAliasing<T> {
15	pub fn new(inner: T) -> Self {
16		let inner = MaybeUninit::new(inner);
17		Self { inner }
18	}
19
20	pub fn inner(&self) -> &T {
21		// SAFETY: We always initialize `inner` in the constructor.
22		unsafe {
23			self.inner.assume_init_ref()
24		}
25	}
26}
27
28impl<T> Drop for NonAliasing<T> {
29	fn drop(&mut self) {
30		// SAFETY: We always initialize `inner` in the constructor,
31		// the API only exposes `assume_init_ref()`,
32		// and we're in the destructor, so nobody is going to call assume_init_read() again.
33		unsafe {
34			drop(self.inner.assume_init_read())
35		}
36	}
37}
subst/non_aliasing.rs

subst/
non_aliasing.rs
