Struct std::ptr::DynMetadata

pub struct DynMetadata<Dyn> where
    Dyn: ?Sized,  { /* private fields */ }

🔬 This is a nightly-only experimental API. (ptr_metadata #81513)

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 it 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.

Implementations

impl<Dyn> DynMetadata<Dyn> where
    Dyn: ?Sized, 

pub fn size_of(self) -> usize

🔬 This is a nightly-only experimental API. (ptr_metadata #81513)

Returns the size of the type associated with this vtable.

pub fn align_of(self) -> usize

🔬 This is a nightly-only experimental API. (ptr_metadata #81513)

Returns the alignment of the type associated with this vtable.

pub fn layout(self) -> Layout

🔬 This is a nightly-only experimental API. (ptr_metadata #81513)

Returns the size and alignment together as a Layout

Trait Implementations

impl<Dyn> Clone for DynMetadata<Dyn> where
    Dyn: ?Sized, 

fn clone(&self) -> DynMetadata<Dyn>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<Dyn> Debug for DynMetadata<Dyn> where
    Dyn: ?Sized, 

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<Dyn> Hash for DynMetadata<Dyn> where
    Dyn: ?Sized, 

fn hash<H>(&self, hasher: &mut H) where
    H: Hasher, 

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl<Dyn> Ord for DynMetadata<Dyn> where
    Dyn: ?Sized, 

fn cmp(&self, other: &DynMetadata<Dyn>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl<Dyn> PartialEq<DynMetadata<Dyn>> for DynMetadata<Dyn> where
    Dyn: ?Sized, 

fn eq(&self, other: &DynMetadata<Dyn>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<Dyn> PartialOrd<DynMetadata<Dyn>> for DynMetadata<Dyn> where
    Dyn: ?Sized, 

fn partial_cmp(&self, other: &DynMetadata<Dyn>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

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,