Struct futures::task::Task
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pub struct Task { /* fields omitted */ }A handle to a "task", which represents a single lightweight "thread" of execution driving a future to completion.
In general, futures are composed into large units of work, which are then spawned as tasks onto an executor. The executor is responsible for polling the future as notifications arrive, until the future terminates.
This is obtained by the task::current function.
Methods
impl Task[src]
fn notify(&self)
Indicate that the task should attempt to poll its future in a timely fashion.
It's typically guaranteed that, for each call to notify, poll will
be called at least once subsequently (unless the future has terminated).
If the task is currently polling its future when notify is called, it
must poll the future again afterwards, ensuring that all relevant
events are eventually observed by the future.
fn is_current(&self) -> bool
: intended to be removed, see docs for details
Returns true when called from within the context of the task.
In other words, the task is currently running on the thread calling the
function. Note that this is currently, and has historically, been
implemented by tracking an id on every instance of Spawn created.
When a Spawn is being polled it stores in thread-local-storage the id
of the instance, and then task::current will return a Task that also
stores this id.
The intention of this function was to answer questions like "if I
notify this task, is it equivalent to task::current().notify()?"
The answer "yes" may be able to avoid some extra work to block the
current task, such as sending a task along a channel or updating a
stored Task somewhere. An answer of "no" typically results in doing
the work anyway.
Unfortunately this function has been somewhat buggy in the past and is
not intended to be supported in the future. By simply matching id the
intended question above isn't accurately taking into account, for
example, unpark events (now deprecated, but still a feature). Thus many
old users of this API weren't fully accounting for the question it was
intended they were asking.
This API continues to be implemented but will in the future, e.g. in the
0.1.x series of this crate, eventually return false unconditionally.
It is intended that this function will be removed in the next breaking
change of this crate. If you'd like to continue to be able to answer the
example question above, it's recommended you use the
will_notify_current method.
If you've got questions about this though please let us know! We'd like to learn about other use cases here that we did not consider.
Panics
This function will panic if no current future is being polled.
fn will_notify_current(&self) -> bool
This function is intended as a performance optimization for structures
which store a Task internally.
The purpose of this function is to answer the question "if I notify
this task is it equivalent to task::current().notify()". An answer
"yes" may mean that you don't actually need to call task::current()
and store it, but rather you can simply leave a stored task in place. An
answer of "no" typically means that you need to call task::current()
and store it somewhere.
As this is purely a peformance optimization a valid implementation for
this function is to always return false. A best effort is done to
return true where possible, but false negatives may happen. Note that
this function will not return a false positive, however.
Panics
This function will panic if no current future is being polled.
Trait Implementations
impl Clone for Task[src]
fn clone(&self) -> Task
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)1.0.0
Performs copy-assignment from source. Read more