Struct Header 

pub(crate) struct Header<M> {
    pub(crate) state: AtomicUsize,
    pub(crate) awaiter: UnsafeCell<Option<Waker>>,
    pub(crate) vtable: &'static TaskVTable,
    pub(crate) metadata: M,
    pub(crate) propagate_panic: bool,
}

The header of a task.

This header is stored in memory at the beginning of the heap-allocated task.

Fields

state: AtomicUsize

Current state of the task.

Contains flags representing the current state and the reference count.

awaiter: UnsafeCell<Option<Waker>>

The task that is blocked on the Task handle.

This waker needs to be woken up once the task completes or is closed.

vtable: &'static TaskVTable

The virtual table.

In addition to the actual waker virtual table, it also contains pointers to several other methods necessary for bookkeeping the heap-allocated task.

metadata: M

Metadata associated with the task.

This metadata may be provided to the user.

propagate_panic: bool

Whether or not a panic that occurs in the task should be propagated.

Implementations

impl<M> Header<M>

pub(crate) fn notify(&self, current: Option<&Waker>)

Notifies the awaiter blocked on this task.

If the awaiter is the same as the current waker, it will not be notified.

pub(crate) fn take(&self, current: Option<&Waker>) -> Option<Waker>

Takes the awaiter blocked on this task.

If there is no awaiter or if it is the same as the current waker, returns None.

pub(crate) fn register(&self, waker: &Waker)

Registers a new awaiter blocked on this task.

This method is called when Task is polled and it has not yet completed.

Trait Implementations

impl<M: Debug> Debug for Header<M>

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

Formats the value using the given formatter.