-// 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 future::{FutureObj, LocalFutureObj};
-
-/// A task executor.
-///
-/// Futures are polled until completion by tasks, a kind of lightweight
-/// "thread". A *task executor* is responsible for the creation of these tasks
-/// and the coordination of their execution on real operating system threads. In
-/// particular, whenever a task signals that it can make further progress via a
-/// wake-up notification, it is the responsibility of the task executor to put
-/// the task into a queue to continue executing it, i.e. polling the future in
-/// it, later.
-pub trait Executor {
- /// Spawns a new task with the given future. The future will be polled until
- /// completion.
- ///
- /// # Errors
- ///
- /// The executor may be unable to spawn tasks, either because it has
- /// been shut down or is resource-constrained.
- fn spawn_obj(
- &mut self,
- future: FutureObj<'static, ()>,
- ) -> Result<(), SpawnObjError>;
-
- /// Determines whether the executor is able to spawn new tasks.
- ///
- /// # Returns
- ///
- /// An `Ok` return means the executor is *likely* (but not guaranteed)
- /// to accept a subsequent spawn attempt. Likewise, an `Err` return
- /// means that `spawn` is likely, but not guaranteed, to yield an error.
- #[inline]
- fn status(&self) -> Result<(), SpawnErrorKind> {
- Ok(())
- }
-}
-
-/// Provides the reason that an executor was unable to spawn.
-pub struct SpawnErrorKind {
- _hidden: (),
-}
-
-impl fmt::Debug for SpawnErrorKind {
- fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- f.debug_tuple("SpawnErrorKind")
- .field(&"shutdown")
- .finish()
- }
-}
-
-impl SpawnErrorKind {
- /// Spawning is failing because the executor has been shut down.
- pub fn shutdown() -> SpawnErrorKind {
- SpawnErrorKind { _hidden: () }
- }
-
- /// Check whether this error is the `shutdown` error.
- pub fn is_shutdown(&self) -> bool {
- true
- }
-}
-
-/// The result of a failed spawn
-#[derive(Debug)]
-pub struct SpawnObjError {
- /// The kind of error
- pub kind: SpawnErrorKind,
-
- /// The future for which spawning inside a task was attempted
- pub future: FutureObj<'static, ()>,
-}
-
-/// The result of a failed spawn
-#[derive(Debug)]
-pub struct SpawnLocalObjError {
- /// The kind of error
- pub kind: SpawnErrorKind,
-
- /// The future for which spawning inside a task was attempted
- pub future: LocalFutureObj<'static, ()>,
-}