1use core::sync::atomic::{fence, AtomicI32, Ordering};
2
3#[repr(transparent)]
4#[derive(Default)]
5pub struct RefCount(pub(crate) AtomicI32);
6
7impl RefCount {
8 /// Creates a new `RefCount` with an initial value of `1`.
9 pub const fn new(count: u32) -> Self {
10 Self(AtomicI32::new(count as i32))
11 }
12
13 /// Increments the reference count, returning the new value.
14 pub fn add_ref(&self) -> u32 {
15 (self.0.fetch_add(1, Ordering::Relaxed) + 1) as u32
16 }
17
18 /// Decrements the reference count, returning the new value.
19 ///
20 /// This operation inserts an `Acquire` fence when the reference count reaches zero.
21 /// This prevents reordering before the object is destroyed.
22 pub fn release(&self) -> u32 {
23 let remaining = self.0.fetch_sub(1, Ordering::Release) - 1;
24
25 match remaining.cmp(&0) {
26 core::cmp::Ordering::Equal => fence(Ordering::Acquire),
27 core::cmp::Ordering::Less => panic!("Object has been over-released."),
28 core::cmp::Ordering::Greater => {}
29 }
30
31 remaining as u32
32 }
33}
34