3 unstable releases
0.2.0 | Jul 30, 2024 |
---|---|
0.1.1 | Jul 11, 2024 |
0.1.0 | Jul 11, 2024 |
#725 in Asynchronous
59 downloads per month
36KB
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Napi Async Local Extension
This crate extends napi-rs with the ability to run local futures.
Run local futures with:
use napi::*;
use napi_derive::napi;
use napi_async_local::SpawnLocalExt;
#[napi]
fn my_js_func(env: Env) -> napi::Result<JsObject> {
env.spawn_local(|env| async {
println!("Running async!");
Ok(())
})
}
This allows for the usage of Channels, Timers and other async utilities in Rust without blocking the main JavaScript thread while retaining the capability of interacting with the underlying JavaScript values.
Installation
Install the crate with:
cargo add napi_async_local
Usage
Use env.spawn_local()
to spawn a non-blocking future on the local thread. Returns a Promise with the value
returned in the async closure.
To ensure the availability of NapiValue
types beyond the life of the parent function scope,
ensure that NapiValue
types that will be used in an async closure are wrapped in a JsRc
which
delegates GC to Rust.
Timers & Callbacks
use std::time::Duration;
use napi::*;
use napi_derive::napi;
use napi_async_local::JsRc;
use napi_async_local::JsRcExt;
use napi_async_local::SpawnLocalExt;
use async_std::task;
#[napi]
fn my_js_func(env: Env, callback: JsRc<JsFunction>) -> napi::Result<JsObject> {
env.spawn_local(move |env| async move {
task::sleep(Duration::from_millis(1000)).await;
callback.inner(&env)?.call_without_args(None)?;
Ok(())
})
}
import napi from './napi.node'
napi.myJsFunc(() => console.log('Waited for 1 second'))
Channels and Threads
You may combine OS threads with async channels to coordinate off-thread workloads.
I recommend using async_std for async utilities as the custom Futures reactor is not compatible with Tokio utilities.
use std::thread;
use std::time::Duration;
use napi::*;
use napi_derive::napi;
use napi_async_local::JsRc;
use napi_async_local::JsRcExt;
use napi_async_local::SpawnLocalExt;
use async_std::channel;
#[napi]
fn my_js_func(env: Env, callback: JsRc<JsFunction>) -> napi::Result<JsObject> {
let (tx, rx) = channel::unbounded();
thread::spawn(move || {
for i in 0..10 {
tx.send_blocking(i).unwrap();
thread::sleep(Duration::from_millis(1000));
}
});
env.spawn_local(move |env| async move {
while let Ok(value) = rx.recv().await {
println!("Got number: {}", value);
callback.inner(&env)?.call(None, &[env.create_int32(value)?])?;
}
Ok(())
})
}
Development
To setup the development environment ensure you have installed just
, then run:
npm install
just run example-a
Dependencies
~1.5–6.5MB
~51K SLoC