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//! A batteries included runtime for applications using Tokio.
//!
//! Applications using Tokio require some runtime support in order to work:
//!
//! * A [driver] to drive I/O resources.
//! * An [executor] to execute tasks that use these I/O resources.
//! * A [timer] for scheduling work to run after a set period of time.
//!
//! While it is possible to setup each component manually, this involves a bunch
//! of boilerplate.
//!
//! [`Runtime`] bundles all of these various runtime components into a single
//! handle that can be started and shutdown together, eliminating the necessary
//! boilerplate to run a Tokio application.
//!
//! Most applications wont need to use [`Runtime`] directly. Instead, they will
//! use the [`run`] function, which uses [`Runtime`] under the hood.
//!
//! Creating a [`Runtime`] does the following:
//!
//! * Spawn a background thread running a [`Reactor`] instance.
//! * Start a [`ThreadPool`] for executing futures.
//! * Run an instance of [`Timer`] **per** thread pool worker thread.
//!
//! The thread pool uses a work-stealing strategy and is configured to start a
//! worker thread for each CPU core available on the system. This tends to be
//! the ideal setup for Tokio applications.
//!
//! A timer per thread pool worker thread is used to minimize the amount of
//! synchronization that is required for working with the timer.
//!
//! # Usage
//!
//! Most applications will use the [`tokio::main`] attribute macro.
//!
//! ```no_run
//! use tokio::net::TcpListener;
//! use tokio::prelude::*;
//!
//! #[tokio::main]
//! async fn main() -> Result<(), Box<dyn std::error::Error>> {
//!     let mut listener = TcpListener::bind("127.0.0.1:8080").await?;
//!
//!     loop {
//!         let (mut socket, _) = listener.accept().await?;
//!
//!         tokio::spawn(async move {
//!             let mut buf = [0; 1024];
//!
//!             // In a loop, read data from the socket and write the data back.
//!             loop {
//!                 let n = match socket.read(&mut buf).await {
//!                     // socket closed
//!                     Ok(n) if n == 0 => return,
//!                     Ok(n) => n,
//!                     Err(e) => {
//!                         println!("failed to read from socket; err = {:?}", e);
//!                         return;
//!                     }
//!                 };
//!
//!                 // Write the data back
//!                 if let Err(e) = socket.write_all(&buf[0..n]).await {
//!                     println!("failed to write to socket; err = {:?}", e);
//!                     return;
//!                 }
//!             }
//!         });
//!     }
//! }
//! ```
//!
//! In this function, the `run` function blocks until the runtime becomes idle.
//! See [`shutdown_on_idle`][idle] for more shutdown details.
//!
//! From within the context of the runtime, additional tasks are spawned using
//! the [`tokio::spawn`] function. Futures spawned using this function will be
//! executed on the same thread pool used by the [`Runtime`].
//!
//! A [`Runtime`] instance can also be used directly.
//!
//! ```no_run
//! use tokio::net::TcpListener;
//! use tokio::prelude::*;
//! use tokio::runtime::Runtime;
//!
//! fn main() -> Result<(), Box<dyn std::error::Error>> {
//!     // Create the runtime
//!     let rt = Runtime::new()?;
//!
//!     // Spawn the root task
//!     rt.block_on(async {
//!         let mut listener = TcpListener::bind("127.0.0.1:8080").await?;
//!
//!         loop {
//!             let (mut socket, _) = listener.accept().await?;
//!
//!             tokio::spawn(async move {
//!                 let mut buf = [0; 1024];
//!
//!                 // In a loop, read data from the socket and write the data back.
//!                 loop {
//!                     let n = match socket.read(&mut buf).await {
//!                         // socket closed
//!                         Ok(n) if n == 0 => return,
//!                         Ok(n) => n,
//!                         Err(e) => {
//!                             println!("failed to read from socket; err = {:?}", e);
//!                             return;
//!                         }
//!                     };
//!
//!                     // Write the data back
//!                     if let Err(e) = socket.write_all(&buf[0..n]).await {
//!                         println!("failed to write to socket; err = {:?}", e);
//!                         return;
//!                     }
//!                 }
//!             });
//!         }
//!     })
//! }
//! ```
//!
//! [driver]: tokio_net::driver
//! [executor]: https://tokio.rs/docs/internals/runtime-model/#executors
//! [timer]: ../timer/index.html
//! [`Runtime`]: struct.Runtime.html
//! [`Reactor`]: ../reactor/struct.Reactor.html
//! [`ThreadPool`]: https://docs.rs/tokio-executor/0.2.0-alpha.2/tokio_executor/threadpool/struct.ThreadPool.html
//! [`run`]: fn.run.html
//! [idle]: struct.Runtime.html#method.shutdown_on_idle
//! [`tokio::spawn`]: ../executor/fn.spawn.html
//! [`Timer`]: https://docs.rs/tokio-timer/0.2/tokio_timer/timer/struct.Timer.html
//! [`tokio::main`]: ../../tokio_macros/attr.main.html

pub mod current_thread;
#[cfg(feature = "rt-full")]
mod threadpool;

#[cfg(feature = "rt-full")]
pub use self::threadpool::{
    Builder,
    Runtime,
    TaskExecutor,
};

// Internal export, don't use.
// This exists to support "auto" runtime selection when using the
// #[tokio::main] attribute.
#[doc(hidden)]
pub mod __main {
    #[cfg(feature = "rt-full")]
    pub use super::Runtime;

    #[cfg(not(feature = "rt-full"))]
    pub use super::current_thread::Runtime;
}