75 lines
2.3 KiB
Rust
75 lines
2.3 KiB
Rust
use core::marker::PhantomData;
|
|
|
|
use js_sys::Promise;
|
|
use wasm_bindgen::prelude::*;
|
|
|
|
use super::raw::util::UninitCell;
|
|
use super::raw::{self};
|
|
use super::Spawner;
|
|
|
|
/// WASM executor, wasm_bindgen to schedule tasks on the JS event loop.
|
|
pub struct Executor {
|
|
inner: raw::Executor,
|
|
ctx: &'static WasmContext,
|
|
not_send: PhantomData<*mut ()>,
|
|
}
|
|
|
|
pub(crate) struct WasmContext {
|
|
promise: Promise,
|
|
closure: UninitCell<Closure<dyn FnMut(JsValue)>>,
|
|
}
|
|
|
|
impl WasmContext {
|
|
pub fn new() -> Self {
|
|
Self {
|
|
promise: Promise::resolve(&JsValue::undefined()),
|
|
closure: UninitCell::uninit(),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl Executor {
|
|
/// Create a new Executor.
|
|
pub fn new() -> Self {
|
|
let ctx = &*Box::leak(Box::new(WasmContext::new()));
|
|
let inner = raw::Executor::new(
|
|
|p| unsafe {
|
|
let ctx = &*(p as *const () as *const WasmContext);
|
|
let _ = ctx.promise.then(ctx.closure.as_mut());
|
|
},
|
|
ctx as *const _ as _,
|
|
);
|
|
Self {
|
|
inner,
|
|
not_send: PhantomData,
|
|
ctx,
|
|
}
|
|
}
|
|
|
|
/// Run the executor.
|
|
///
|
|
/// The `init` closure is called with a [`Spawner`] that spawns tasks on
|
|
/// this executor. Use it to spawn the initial task(s). After `init` returns,
|
|
/// the executor starts running the tasks.
|
|
///
|
|
/// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
|
|
/// for example by passing it as an argument to the initial tasks.
|
|
///
|
|
/// This function requires `&'static mut self`. This means you have to store the
|
|
/// Executor instance in a place where it'll live forever and grants you mutable
|
|
/// access. There's a few ways to do this:
|
|
///
|
|
/// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
|
|
/// - a `static mut` (unsafe)
|
|
/// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
|
|
pub fn start(&'static mut self, init: impl FnOnce(Spawner)) {
|
|
unsafe {
|
|
let executor = &self.inner;
|
|
self.ctx.closure.write(Closure::new(move |_| {
|
|
executor.poll();
|
|
}));
|
|
init(self.inner.spawner());
|
|
}
|
|
}
|
|
}
|