RawWakerVTable in core::task - Rust
Description: A virtual function pointer table (vtable) that specifies the behavior of a `RawWaker`.

## RawWakerVTable

# Struct RawWakerVTable

1.36.0 · Source

    pub struct RawWakerVTable { /* private fields */ }

Expand description

A virtual function pointer table (vtable) that specifies the behavior of a `RawWaker`.

The pointer passed to all functions inside the vtable is the `data` pointer from the enclosing `RawWaker` object.

The functions inside this struct are only intended to be called on the `data` pointer of a properly constructed `RawWaker` object from inside the `RawWaker` implementation. Calling one of the contained functions using any other `data` pointer will cause undefined behavior.

Note that while this type implements `PartialEq`, comparing function pointers, and hence comparing structs like this that contain function pointers, is unreliable: pointers to the same function can compare inequal (because functions are duplicated in multiple codegen units), and pointers to different functions can compare equal (since identical functions can be deduplicated within a codegen unit).

## §Thread safety

If the `RawWaker` will be used to construct a `Waker` then these functions must all be thread-safe (even though `RawWaker` is `!Send + !Sync`). This is because `Waker` is `Send + Sync`, and it may be moved to arbitrary threads or invoked by `&` reference. For example, this means that if the `clone` and `drop` functions manage a reference count, they must do so atomically.

However, if the `RawWaker` will be used to construct a `LocalWaker` instead, then these functions don’t need to be thread safe. This means that `!Send + !Sync` data can be stored in the data pointer, and reference counting does not need any atomic synchronization. This is because `LocalWaker` is not thread safe itself, so it cannot be sent across threads.

## Implementations§

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### impl RawWakerVTable

1.36.0 (const: 1.36.0) · Source

#### pub const fn new( clone: unsafe fn(*const ()) -> RawWaker, wake: unsafe fn(*const ()), wake_by_ref: unsafe fn(*const ()), drop: unsafe fn(*const ()), ) -> Self

Creates a new `RawWakerVTable` from the provided `clone`, `wake`, `wake_by_ref`, and `drop` functions.

If the `RawWaker` will be used to construct a `Waker` then these functions must all be thread-safe (even though `RawWaker` is `!Send + !Sync`). This is because `Waker` is `Send + Sync`, and it may be moved to arbitrary threads or invoked by `&` reference. For example, this means that if the `clone` and `drop` functions manage a reference count, they must do so atomically.

However, if the `RawWaker` will be used to construct a `LocalWaker` instead, then these functions don’t need to be thread safe. This means that `!Send + !Sync` data can be stored in the data pointer, and reference counting does not need any atomic synchronization. This is because `LocalWaker` is not thread safe itself, so it cannot be sent across threads.

##### §`clone`

This function will be called when the `RawWaker` gets cloned, e.g. when the `Waker`/`LocalWaker` in which the `RawWaker` is stored gets cloned.

The implementation of this function must retain all resources that are required for this additional instance of a `RawWaker` and associated task. Calling `wake` on the resulting `RawWaker` should result in a wakeup of the same task that would have been awoken by the original `RawWaker`.

##### §`wake`

This function will be called when `wake` is called on the `Waker`. It must wake up the task associated with this `RawWaker`.

The implementation of this function must make sure to release any resources that are associated with this instance of a `RawWaker` and associated task.

##### §`wake_by_ref`

This function will be called when `wake_by_ref` is called on the `Waker`. It must wake up the task associated with this `RawWaker`.

This function is similar to `wake`, but must not consume the provided data pointer.

##### §`drop`

This function will be called when a `Waker`/`LocalWaker` gets dropped.

The implementation of this function must make sure to release any resources that are associated with this instance of a `RawWaker` and associated task.

## Trait Implementations§

1.36.0 · Source§

### impl Clone for RawWakerVTable

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#### fn clone(&self) -> RawWakerVTable

Returns a duplicate of the value. Read more
1.0.0 · Source§

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

Performs copy-assignment from `source`. Read more
1.36.0 · Source§

### impl Debug for RawWakerVTable

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

Formats the value using the given formatter. Read more
1.36.0 · Source§

### impl PartialEq for RawWakerVTable

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#### fn eq(&self, other: &RawWakerVTable) -> bool

Tests for `self` and `other` values to be equal, and is used by `==`.
1.0.0 · Source§

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

Tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
1.36.0 · Source§

### impl Copy for RawWakerVTable

1.36.0 · Source§

### impl StructuralPartialEq for RawWakerVTable

## Auto Trait Implementations§

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### impl Freeze for RawWakerVTable

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### impl RefUnwindSafe for RawWakerVTable

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### impl Send for RawWakerVTable

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### impl Sync for RawWakerVTable

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### impl Unpin for RawWakerVTable

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### impl UnwindSafe for RawWakerVTable

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit` #126799)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.