mirror of https://github.com/stjepang/smol
121 lines
3.5 KiB
Rust
121 lines
3.5 KiB
Rust
//! A small and fast async runtime.
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//!
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//! # Examples
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//!
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//! Connect to an HTTP website, make a GET request, and pipe the response to the standard output:
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//!
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//! ```
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//! use smol::{io, net, prelude::*, Unblock};
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//!
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//! fn main() -> io::Result<()> {
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//! smol::block_on(async {
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//! let mut stream = net::TcpStream::connect("example.com:80").await?;
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//! let req = b"GET / HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n";
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//! stream.write_all(req).await?;
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//!
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//! let mut stdout = Unblock::new(std::io::stdout());
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//! io::copy(&stream, &mut stdout).await?;
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//! Ok(())
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//! })
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//! }
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//! ```
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//!
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//! This example uses the [`net`] module for networking, but you can also use the primitive
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//! [`Async`] type. See the [full code][get-request].
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//!
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//! Look inside the [examples] directory for more.
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//!
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//! [`async-net`]: https://docs.rs/async-net
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//! [examples]: https://github.com/stjepang/smol/tree/master/examples
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//! [get-request]: https://github.com/stjepang/smol/blob/master/examples/get-request.rs
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#![forbid(unsafe_code)]
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#![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
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#[cfg(doctest)]
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doc_comment::doctest!("../README.md");
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use std::future::Future;
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use std::panic::catch_unwind;
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use std::thread;
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use once_cell::sync::Lazy;
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#[doc(inline)]
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pub use {
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async_executor::{Executor, LocalExecutor, Task},
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async_io::{block_on, Async, Timer},
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blocking::{unblock, Unblock},
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futures_lite::{future, io, stream},
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futures_lite::{pin, ready},
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};
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#[doc(inline)]
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pub use {
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async_channel as channel, async_fs as fs, async_lock as lock, async_net as net,
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async_process as process,
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};
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pub mod prelude {
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//! Traits [`Future`], [`AsyncBufRead`], [`AsyncRead`], [`AsyncSeek`], [`AsyncWrite`], and
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//! their extensions.
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//!
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//! # Examples
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//!
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//! ```
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//! use smol::prelude::*;
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//! ```
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#[doc(no_inline)]
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pub use futures_lite::{
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future::{Future, FutureExt},
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io::{AsyncBufRead, AsyncBufReadExt},
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io::{AsyncRead, AsyncReadExt},
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io::{AsyncSeek, AsyncSeekExt},
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io::{AsyncWrite, AsyncWriteExt},
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stream::{Stream, StreamExt},
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};
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}
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/// Spawns a task onto the single-threaded global executor.
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///
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/// There is a (single-threaded by default) global executor that gets lazily initialized on first use.
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/// It is advisable to use it in tests or small programs, but it is otherwise a better idea to define
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/// your own [`Executor`]s.
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/// You can configure the number of threads of the global executor using the `SMOL_THREADS` environment
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/// variable.
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///
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/// # Examples
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///
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/// ```
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/// let task = smol::spawn(async {
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/// 1 + 2
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/// });
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///
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/// smol::block_on(async {
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/// assert_eq!(task.await, 3);
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/// });
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/// ```
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pub fn spawn<T: Send + 'static>(future: impl Future<Output = T> + Send + 'static) -> Task<T> {
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static GLOBAL: Lazy<Executor> = Lazy::new(|| {
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let num_threads = {
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// Parse SMOL_THREADS or run a monothreaded executor.
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std::env::var("SMOL_THREADS")
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.ok()
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.and_then(|s| s.parse().ok())
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.unwrap_or(1)
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};
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for n in 1..=num_threads {
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thread::Builder::new()
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.name(format!("smol-{}", n))
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.spawn(|| loop {
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let _ =
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catch_unwind(|| async_io::block_on(GLOBAL.run(future::pending::<()>())));
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})
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.expect("cannot spawn executor thread");
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}
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Executor::new()
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});
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GLOBAL.spawn(future)
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}
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