Struct rustc_data_structures::owning_ref::OwningHandle

pub struct OwningHandle<O, H> where
    O: StableAddress,
    H: Deref,  {
    handle: H,
    _owner: O,
}

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.

Since the callback needs to dereference a raw pointer, it requires unsafe code. To avoid forcing this unsafety on most callers, the ToHandle trait is implemented for common data structures. Types that implement ToHandle can be wrapped into an OwningHandle without passing a callback.

Fields

handle: H

_owner: O

Implementations

impl<O, H> OwningHandle<O, H> where
    O: StableAddress<Target: ToHandle<Handle = H>>,
    H: Deref, 

pub fn new(o: O) -> Self

Creates a new OwningHandle for a type that implements ToHandle. For types that don’t implement ToHandle, callers may invoke new_with_fn, which accepts a callback to perform the conversion.

impl<O, H> OwningHandle<O, H> where
    O: StableAddress<Target: ToHandleMut<HandleMut = H>>,
    H: DerefMut, 

pub fn new_mut(o: O) -> Self

Creates a new mutable OwningHandle for a type that implements ToHandleMut.

impl<O, H> OwningHandle<O, H> where
    O: StableAddress,
    H: Deref, 

pub fn new_with_fn<F>(o: O, f: F) -> Self where
    F: FnOnce(*const O::Target) -> H, 

Creates 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.

pub fn try_new<F, E>(o: O, f: F) -> Result<Self, E> where
    F: FnOnce(*const O::Target) -> Result<H, E>, 

Creates 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, 

type Target = H::Target

The resulting type after dereferencing.

fn deref(&self) -> &H::Target

Dereferences the value.

impl<O, H> DerefMut for OwningHandle<O, H> where
    O: StableAddress,
    H: DerefMut, 

fn deref_mut(&mut self) -> &mut H::Target

Mutably dereferences the value.

impl<O, H> StableDeref for OwningHandle<O, H> where
    O: StableAddress,
    H: StableAddress, 

Layout

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.