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use alloc::sync::Arc;↩
↩
/// Guarantees uniqueness only if `Weak` pointers are never created↩
/// from this `Arc` or clones.↩
pub(crate) fn is_arc_unique<M>(arc: &mut Arc<M>) -> bool {↩
let strong_count = Arc::strong_count(&*arc);↩
debug_assert_ne!(strong_count, 0, "This Arc should exist");↩
↩
debug_assert!(↩
strong_count > 1 || Arc::get_mut(arc).is_some(),↩
"`Weak` pointer exists"↩
);↩
↩
strong_count == 1↩
}↩
↩
/// Can be used instead of `Arc::try_unwrap(arc).unwrap()`↩
/// when it is guaranteed to succeed.↩
pub(crate) unsafe fn arc_unwrap<M>(mut arc: Arc<M>) -> M {↩
use core::{mem::ManuallyDrop, ptr::read};↩
debug_assert!(is_arc_unique(&mut arc));↩
↩
// Get raw pointer to inner value.↩
let raw = Arc::into_raw(arc);↩
↩
// As `Arc` is unique and no Weak pointers exist↩
// it won't be dereferenced elsewhere.↩
let inner = read(raw);↩
↩
// Cast to `ManuallyDrop` which guarantees to have same layout↩
// and will skip dropping.↩
drop(Arc::from_raw(raw as *const ManuallyDrop<M>));↩
inner↩
}↩
↩
/// Can be used instead of `Arc::try_unwrap`↩
/// only if `Weak` pointers are never created from this `Arc` or clones.↩
pub(crate) unsafe fn try_arc_unwrap<M>(mut arc: Arc<M>) -> Option<M> {↩
if is_arc_unique(&mut arc) {↩
Some(arc_unwrap(arc))↩
} else {↩
None↩
}↩
}↩