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// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![unstable(feature = "futures_api",
reason = "futures in libcore are unstable",
issue = "50547")]
use fmt;
use super::{Executor, Waker, LocalWaker};
/// Information about the currently-running task.
///
/// Contexts are always tied to the stack, since they are set up specifically
/// when performing a single `poll` step on a task.
pub struct Context<'a> {
local_waker: &'a LocalWaker,
executor: &'a mut dyn Executor,
}
impl<'a> fmt::Debug for Context<'a> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("Context")
.finish()
}
}
impl<'a> Context<'a> {
/// Create a new task `Context` with the provided `local_waker`, `waker`, and `executor`.
#[inline]
pub fn new(local_waker: &'a LocalWaker, executor: &'a mut dyn Executor) -> Context<'a> {
Context {
local_waker,
executor,
}
}
/// Get the `LocalWaker` associated with the current task.
#[inline]
pub fn local_waker(&self) -> &'a LocalWaker {
self.local_waker
}
/// Get the `Waker` associated with the current task.
#[inline]
pub fn waker(&self) -> &'a Waker {
unsafe { &*(self.local_waker as *const LocalWaker as *const Waker) }
}
/// Get the default executor associated with this task.
///
/// This method is useful primarily if you want to explicitly handle
/// spawn failures.
#[inline]
pub fn executor(&mut self) -> &mut dyn Executor {
self.executor
}
/// Produce a context like the current one, but using the given waker instead.
///
/// This advanced method is primarily used when building "internal
/// schedulers" within a task, where you want to provide some customized
/// wakeup logic.
#[inline]
pub fn with_waker<'b>(&'b mut self, local_waker: &'b LocalWaker) -> Context<'b> {
Context {
local_waker,
executor: self.executor,
}
}
/// Produce a context like the current one, but using the given executor
/// instead.
///
/// This advanced method is primarily used when building "internal
/// schedulers" within a task.
#[inline]
pub fn with_executor<'b, E>(&'b mut self, executor: &'b mut E) -> Context<'b>
where E: Executor
{
Context {
local_waker: self.local_waker,
executor: executor,
}
}
}
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