Struct owning_ref::OwningHandle
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pub struct OwningHandle<O, H> where O: StableAddress, H: Deref { /* fields omitted */ }
OwningHandle
is a complement to OwningRef
. Where OwningRef
allows
consumers to pass around an owned object and a dependent reference,
OwningHandle
contains an owned object and a dependent object.
OwningHandle
can encapsulate a RefMut
along with its associated
RefCell
, or an RwLockReadGuard
along with its associated RwLock
.
However, the API is completely generic and there are no restrictions on
what types of owning and dependent objects may be used.
OwningHandle
is created by passing an owner object (which dereferences
to a stable address) along with a callback which receives a pointer to
that stable location. The callback may then dereference the pointer and
mint a dependent object, with the guarantee that the returned object will
not outlive the referent of the pointer.
This does foist some unsafety onto the callback, which needs an unsafe
block to dereference the pointer. It would be almost good enough for
OwningHandle to pass a transmuted &'statc reference to the callback
since the lifetime is infinite as far as the minted handle is concerned.
However, even an Fn
callback can still allow the reference to escape
via a StaticMutex
or similar, which technically violates the safety
contract. Some sort of language support in the lifetime system could
make this API a bit nicer.
Methods
impl<O, H> OwningHandle<O, H> where O: StableAddress, H: Deref
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fn new<F>(o: O, f: F) -> Self where F: Fn(*const O::Target) -> H
Create a new OwningHandle. The provided callback will be invoked with
a pointer to the object owned by o
, and the returned value is stored
as the object to which this OwningHandle
will forward Deref
and
DerefMut
.
Trait Implementations
impl<O, H> Deref for OwningHandle<O, H> where O: StableAddress, H: Deref
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type Target = H::Target
The resulting type after dereferencing
fn deref(&self) -> &H::Target
The method called to dereference a value
impl<O, H> StableAddress for OwningHandle<O, H> where O: StableAddress,
H: StableAddress
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H: StableAddress