pub struct ArcBorrow<'a, T: ?Sized + 'a> { /* private fields */ }
Expand description
A borrowed reference to an Arc
instance.
For cases when one doesn’t ever need to increment the refcount on the allocation, it is simpler
to use just &T
, which we can trivially get from an Arc<T>
instance.
However, when one may need to increment the refcount, it is preferable to use an ArcBorrow<T>
over &Arc<T>
because the latter results in a double-indirection: a pointer (shared reference)
to a pointer (Arc<T>
) to the object (T
). An ArcBorrow
eliminates this double
indirection while still allowing one to increment the refcount and getting an Arc<T>
when/if
needed.
Invariants
There are no mutable references to the underlying Arc
, and it remains valid for the
lifetime of the ArcBorrow
instance.
Example
use kernel::sync::{Arc, ArcBorrow};
struct Example;
fn do_something(e: ArcBorrow<'_, Example>) -> Arc<Example> {
e.into()
}
let obj = Arc::try_new(Example)?;
let cloned = do_something(obj.as_arc_borrow());
// Assert that both `obj` and `cloned` point to the same underlying object.
assert!(core::ptr::eq(&*obj, &*cloned));
Using ArcBorrow<T>
as the type of self
:
use kernel::sync::{Arc, ArcBorrow};
struct Example {
a: u32,
b: u32,
}
impl Example {
fn use_reference(self: ArcBorrow<'_, Self>) {
// ...
}
}
let obj = Arc::try_new(Example { a: 10, b: 20 })?;
obj.as_arc_borrow().use_reference();
Trait Implementations
impl<T: ?Sized> Copy for ArcBorrow<'_, T>
impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<ArcBorrow<'_, U>> for ArcBorrow<'_, T>
Auto Trait Implementations
impl<'a, T> !RefUnwindSafe for ArcBorrow<'a, T>
impl<'a, T> !Send for ArcBorrow<'a, T>
impl<'a, T> !Sync for ArcBorrow<'a, T>
impl<'a, T: ?Sized> Unpin for ArcBorrow<'a, T>
impl<'a, T> !UnwindSafe for ArcBorrow<'a, T>
Blanket Implementations
sourceimpl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more