Struct Context

pub struct Context(/* private fields */);

Represents an ongoing operation which could be cancelled in the future. Inspired by contexts in the Go programming language.

Concepts

Contexts have a few important concepts: “cancellation”, “parent” and “deadline”. A context can be cancelled by calling its Context::cancel() method; this notifies any tasks which are waiting on its Context::done() event. It is also cancelled automatically if and when its parent context is cancelled, and when the last copy of it goes out of scope. A “deadline” allows a context to be automatically cancelled at a certain timestamp; this is implemented without creating extra tasks/threads.

Forking

A context can be “forked”, which creates a new child context. This new context can optionally be created with a deadline.

Implementations

impl Context

pub fn new_global() -> Self

Creates a new global context (i.e., one which has no parent or deadline).

pub fn cancel(&self)

Cancels a context. This is a no-op if the context is already cancelled.

pub fn done(&self) -> impl Selectable + '_

A Selectable event which occurs when the context is cancelled. The sleep amount takes the context deadline into consideration.

pub fn wrap<'a, T: 'a>( &'a self, event: impl Selectable<T> + 'a, ) -> impl Selectable<Option<T>> + 'a

Creates a Selectable event which occurs when either the given event resolves, or when the context is cancelled, whichever occurs first.

Trait Implementations

impl Clone for Context

fn clone(&self) -> Context

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl ParentContext for Context

fn fork(&self) -> Context

Forks a context. The new context’s parent(s) are self.

fn fork_with_deadline(&self, deadline: Instant) -> Context

Forks a context. Equivalent to Self::fork(), except that the new context has a deadline which is the earliest of those in self and the one provided.

fn fork_with_timeout(&self, timeout: Duration) -> Context

Forks a context. Equivalent to Self::fork_with_deadline(), except that the deadline is calculated from the current time and the provided timeout duration.