pub struct DynMetadata<Dyn>where
Dyn: ?Sized,{ /* private fields */ }
ptr_metadata
)Expand description
The metadata for a Dyn = dyn SomeTrait
trait object type.
It is a pointer to a vtable (virtual call table) that represents all the necessary information to manipulate the concrete type stored inside a trait object. The vtable notably contains:
- type size
- type alignment
- a pointer to the type’s
drop_in_place
impl (may be a no-op for plain-old-data) - pointers to all the methods for the type’s implementation of the trait
Note that the first three are special because they’re necessary to allocate, drop, and deallocate any trait object.
It is possible to name this struct with a type parameter that is not a dyn
trait object
(for example DynMetadata<u64>
) but not to obtain a meaningful value of that struct.
Note that while this type implements PartialEq
, comparing vtable pointers is unreliable:
pointers to vtables of the same type for the same trait can compare inequal (because vtables are
duplicated in multiple codegen units), and pointers to vtables of different types/traits can
compare equal (since identical vtables can be deduplicated within a codegen unit).
Implementations§
source§impl<Dyn> DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> DynMetadata<Dyn>where
Dyn: ?Sized,
sourcepub fn size_of(self) -> usize
🔬This is a nightly-only experimental API. (ptr_metadata
)
pub fn size_of(self) -> usize
ptr_metadata
)Returns the size of the type associated with this vtable.
Trait Implementations§
source§impl<Dyn> Clone for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> Clone for DynMetadata<Dyn>where
Dyn: ?Sized,
source§fn clone(&self) -> DynMetadata<Dyn>
fn clone(&self) -> DynMetadata<Dyn>
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl<Dyn> Debug for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> Debug for DynMetadata<Dyn>where
Dyn: ?Sized,
source§impl<Dyn> Hash for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> Hash for DynMetadata<Dyn>where
Dyn: ?Sized,
source§impl<Dyn> Ord for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> Ord for DynMetadata<Dyn>where
Dyn: ?Sized,
source§fn cmp(&self, other: &DynMetadata<Dyn>) -> Ordering
fn cmp(&self, other: &DynMetadata<Dyn>) -> Ordering
1.21.0 · source§fn max(self, other: Self) -> Selfwhere
Self: Sized,
fn max(self, other: Self) -> Selfwhere
Self: Sized,
source§impl<Dyn> PartialEq for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> PartialEq for DynMetadata<Dyn>where
Dyn: ?Sized,
source§impl<Dyn> PartialOrd for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> PartialOrd for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> Copy for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> Eq for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> Send for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> Sync for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> Unpin for DynMetadata<Dyn>where
Dyn: ?Sized,
Auto Trait Implementations§
impl<Dyn> Freeze for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Dyn> !RefUnwindSafe for DynMetadata<Dyn>
impl<Dyn> !UnwindSafe for DynMetadata<Dyn>
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T> CloneToUninit for Twhere
T: Clone,
impl<T> CloneToUninit for Twhere
T: Clone,
source§unsafe fn clone_to_uninit(&self, dst: *mut T)
unsafe fn clone_to_uninit(&self, dst: *mut T)
clone_to_uninit
)§impl<Q, K> Comparable<K> for Q
impl<Q, K> Comparable<K> for Q
§impl<Q, K> Equivalent<K> for Q
impl<Q, K> Equivalent<K> for Q
§fn equivalent(&self, key: &K) -> bool
fn equivalent(&self, key: &K) -> bool
§impl<Q, K> Equivalent<K> for Q
impl<Q, K> Equivalent<K> for Q
§fn equivalent(&self, key: &K) -> bool
fn equivalent(&self, key: &K) -> bool
key
and return true
if they are equal.