crates/futures-rs-0.3.29/futures-executor/src/lib.rs

//! Built-in executors and related tools.
//!
//! All asynchronous computation occurs within an executor, which is
//! capable of spawning futures as tasks. This module provides several
//! built-in executors, as well as tools for building your own.
//!
//! All items are only available when the `std` feature of this
//! library is activated, and it is activated by default.
//!
//! # Using a thread pool (M:N task scheduling)
//!
//! Most of the time tasks should be executed on a [thread pool](ThreadPool).
//! A small set of worker threads can handle a very large set of spawned tasks
//! (which are much lighter weight than threads). Tasks spawned onto the pool
//! with the [`spawn_ok`](ThreadPool::spawn_ok) function will run ambiently on
//! the created threads.
//!
//! # Spawning additional tasks
//!
//! Tasks can be spawned onto a spawner by calling its [`spawn_obj`] method
//! directly. In the case of `!Send` futures, [`spawn_local_obj`] can be used
//! instead.
//!
//! # Single-threaded execution
//!
//! In addition to thread pools, it's possible to run a task (and the tasks
//! it spawns) entirely within a single thread via the [`LocalPool`] executor.
//! Aside from cutting down on synchronization costs, this executor also makes
//! it possible to spawn non-`Send` tasks, via [`spawn_local_obj`]. The
//! [`LocalPool`] is best suited for running I/O-bound tasks that do relatively
//! little work between I/O operations.
//!
//! There is also a convenience function [`block_on`] for simply running a
//! future to completion on the current thread.
//!
//! [`spawn_obj`]: https://docs.rs/futures/0.3/futures/task/trait.Spawn.html#tymethod.spawn_obj
//! [`spawn_local_obj`]: https://docs.rs/futures/0.3/futures/task/trait.LocalSpawn.html#tymethod.spawn_local_obj

#![cfg_attr(not(feature = "std"), no_std)]
#![warn(
    missing_debug_implementations,
    missing_docs,
    rust_2018_idioms,
    single_use_lifetimes,
    unreachable_pub
)]
#![doc(test(
    no_crate_inject,
    attr(
        deny(warnings, rust_2018_idioms, single_use_lifetimes),
        allow(dead_code, unused_assignments, unused_variables)
    )
))]
#![cfg_attr(docsrs, feature(doc_cfg))]

#[cfg(feature = "std")]
mod local_pool;
#[cfg(feature = "std")]
pub use crate::local_pool::{block_on, block_on_stream, BlockingStream, LocalPool, LocalSpawner};

#[cfg(feature = "thread-pool")]
#[cfg_attr(docsrs, doc(cfg(feature = "thread-pool")))]
#[cfg(feature = "std")]
mod thread_pool;
#[cfg(feature = "thread-pool")]
#[cfg(feature = "std")]
mod unpark_mutex;
#[cfg(feature = "thread-pool")]
#[cfg_attr(docsrs, doc(cfg(feature = "thread-pool")))]
#[cfg(feature = "std")]
pub use crate::thread_pool::{ThreadPool, ThreadPoolBuilder};

#[cfg(feature = "std")]
mod enter;
#[cfg(feature = "std")]
pub use crate::enter::{enter, Enter, EnterError};