1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88

#![doc(html_root_url = "https://docs.rs/tokio-executor/0.2.0-alpha.6")]
#![warn(
    missing_debug_implementations,
    missing_docs,
    rust_2018_idioms,
    unreachable_pub
)]
#![deny(intra_doc_link_resolution_failure)]
#![doc(test(
    no_crate_inject,
    attr(deny(warnings, rust_2018_idioms), allow(dead_code, unused_variables))
))]

//! Task execution related traits and utilities.
//!
//! In the Tokio execution model, futures are lazy. When a future is created, no
//! work is performed. In order for the work defined by the future to happen,
//! the future must be submitted to an executor. A future that is submitted to
//! an executor is called a "task".
//!
//! The executor is responsible for ensuring that [`Future::poll`] is called
//! whenever the task is notified. Notification happens when the internal
//! state of a task transitions from *not ready* to *ready*. For example, a
//! socket might have received data and a call to `read` will now be able to
//! succeed.
//!
//! This crate provides traits and utilities that are necessary for building an
//! executor, including:
//!
//! * The [`Executor`] trait spawns future object onto an executor.
//!
//! * The [`TypedExecutor`] trait spawns futures of a specific type onto an
//!   executor. This is used to be generic over executors that spawn futures
//!   that are either `Send` or `!Send` or implement executors that apply to
//!   specific futures.
//!
//! * [`enter`] marks that the current thread is entering an execution
//!   context. This prevents a second executor from accidentally starting from
//!   within the context of one that is already running.
//!
//! * [`DefaultExecutor`] spawns tasks onto the default executor for the current
//!   context.
//!
//! * [`Park`] abstracts over blocking and unblocking the current thread.
//!
//! # Implementing an executor
//!
//! Executors should always implement `TypedExecutor`. This usually is the bound
//! that applications and libraries will use when generic over an executor. See
//! the [trait documentation][`TypedExecutor`] for more details.
//!
//! If the executor is able to spawn all futures that are `Send`, then the
//! executor should also implement the `Executor` trait. This trait is rarely
//! used directly by applications and libraries. Instead, `tokio::spawn` is
//! configured to dispatch to type that implements `Executor`.
//!
//! [`Executor`]: trait.Executor.html
//! [`TypedExecutor`]: trait.TypedExecutor.html
//! [`enter`]: fn.enter.html
//! [`DefaultExecutor`]: struct.DefaultExecutor.html
//! [`Park`]: park/index.html
//! [`Future::poll`]: https://doc.rust-lang.org/std/future/trait.Future.html#tymethod.poll
#[cfg(any(feature = "current-thread", feature = "threadpool"))]
#[macro_use]
mod tracing;

mod enter;
mod error;
mod executor;
mod global;
pub mod park;
mod typed;

#[cfg(feature = "blocking")]
pub mod blocking;

#[cfg(feature = "current-thread")]
pub mod current_thread;

#[cfg(feature = "threadpool")]
pub mod threadpool;

pub use crate::enter::{enter, exit, Enter, EnterError};
pub use crate::error::SpawnError;
pub use crate::executor::Executor;
pub use crate::global::{spawn, with_default, DefaultExecutor};
pub use crate::typed::TypedExecutor;
pub use futures_util::future::RemoteHandle;