Struct std::ptr::DynMetadata

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

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

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 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

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

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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.

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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.

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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

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

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

Returns a copy of the value. Read more

1.0.0 · source

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

Performs copy-assignment from source. Read more

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

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

Formats the value using the given formatter. Read more

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

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

Feeds this value into the given Hasher. Read more

1.3.0 · source

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

Feeds a slice of this type into the given Hasher. Read more

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

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

This method returns an Ordering between self and other. Read more

1.21.0 · source

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

Compares and returns the maximum of two values. Read more

1.21.0 · source

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

Compares and returns the minimum of two values. Read more

1.50.0 · source

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

Restrict a value to a certain interval. Read more

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

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

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

1.0.0 · source

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

This method tests for !=.

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

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

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

1.0.0 · source

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

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

1.0.0 · source

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

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

1.0.0 · source

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

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

1.0.0 · source

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

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

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

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

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

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

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