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§
Source§impl RawWakerVTable
impl RawWakerVTable
1.36.0 (const: 1.36.0) · Sourcepub const fn new(
clone: unsafe fn(_: *const ()) -> RawWaker,
wake: unsafe fn(_: *const ()),
wake_by_ref: unsafe fn(_: *const ()),
drop: unsafe fn(_: *const ()),
) -> RawWakerVTable
pub const fn new( clone: unsafe fn(_: *const ()) -> RawWaker, wake: unsafe fn(_: *const ()), wake_by_ref: unsafe fn(_: *const ()), drop: unsafe fn(_: *const ()), ) -> RawWakerVTable
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
impl Clone for RawWakerVTable
Source§fn clone(&self) -> RawWakerVTable
fn clone(&self) -> RawWakerVTable
1.0.0 · Source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source. Read more