Expand description
VWeak
is a version of Parc
that holds a non-owning thread-safe
reference to the managed allocation in the volatile heap. The allocation is
accessed by calling upgrade
on the VWeak
pointer, which returns an
Option
<
Parc
<T>>
.
Since a VWeak
reference does not count towards ownership, it will not
prevent the value stored in the allocation from being dropped, and VWeak
itself makes no guarantees about the value still being present. Thus it may
return None
when upgrade
d. Note however that a VWeak
reference,
unlike Weak
, does NOT prevent the allocation itself (the backing
store) from being deallocated.
A VWeak
pointer is useful for keeping a temporary thread-safe reference to
the persistent allocation managed by Parc
without preventing its inner
value from being dropped.
The typical way to obtain a VWeak
pointer is to call Parc::demote
.
Implementations
sourceimpl<T: PSafe + ?Sized, A: MemPool> VWeak<T, A>
impl<T: PSafe + ?Sized, A: MemPool> VWeak<T, A>
sourcepub fn promote(&self, j: &Journal<A>) -> Option<Parc<T, A>>
pub fn promote(&self, j: &Journal<A>) -> Option<Parc<T, A>>
Attempts to promote the VWeak
pointer to an Parc
, delaying
dropping of the inner value if successful.
Returns None
if the inner value has since been dropped.
Examples
use corundum::default::*;
use std::mem::drop;
type P = Allocator;
let obj = P::open::<Root>("foo.pool", O_CF).unwrap();
struct Root(PRefCell<Option<Parc<i32>>>);
impl RootObj<P> for Root {
fn init(j: &Journal) -> Self {
Root(PRefCell::new(Some(Parc::new(10, j))))
}
}
let vweak_obj = obj.0.borrow().as_ref().unwrap().demote();
P::transaction(|j| {
let strong_obj = vweak_obj.promote(j);
assert!(strong_obj.is_some());
// Destroy all strong pointers.
drop(strong_obj);
*obj.0.borrow_mut(j) = None; // RootCell does not drop, so make it None
assert!(vweak_obj.promote(j).is_none());
}).unwrap();
Trait Implementations
impl<T: ?Sized, A: MemPool> PSafe for VWeak<T, A>
impl<T: ?Sized, A: MemPool> RefUnwindSafe for VWeak<T, A>
impl<T: PSend + ?Sized, A: MemPool> Send for VWeak<T, A>
impl<T: PSend + ?Sized, A: MemPool> Sync for VWeak<T, A>
impl<T: ?Sized, A: MemPool> TxInSafe for VWeak<T, A>
impl<T: ?Sized, A: MemPool> TxOutSafe for VWeak<T, A>
impl<T: ?Sized, A: MemPool> UnwindSafe for VWeak<T, A>
Auto Trait Implementations
impl<T, A> LooseTxInUnsafe for VWeak<T, A>
impl<T: ?Sized, A> PSend for VWeak<T, A> where
A: PSend,
T: PSend,
impl<T: ?Sized, A> Unpin for VWeak<T, A>
impl<T: ?Sized, A> VSafe for VWeak<T, A>
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
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
sourceimpl<T> ToOwned for T where
T: Clone,
impl<T> ToOwned for T where
T: Clone,
type Owned = T
type Owned = T
The resulting type after obtaining ownership.
sourcefn clone_into(&self, target: &mut T)
fn clone_into(&self, target: &mut T)
toowned_clone_into
)Uses borrowed data to replace owned data, usually by cloning. Read more