//! Version of [`std::thread`] that also works in WebAssembly.
use std::thread;
use std::time::Duration;
/// See [`Thread`].
struct UniversalThread();
/// Encapsulates the public thread API that has been tested on native and WASM,
/// as well as environment specific implementation. All methods from here
/// will get exposed at the module level as well lower in this file.
trait Thread {
/// Run function in a non-blocking thread.
///
/// Check out the `test_multithread` for sample usage.
///
/// TODO(Paras): Implement join handles. When we do, we can use the same
/// function signature here as [`std::thread::spawn`].
fn spawn(f: impl FnOnce() + Send + 'static);
/// See [`std::thread::sleep`].
fn sleep(duration: Duration);
}
#[cfg(not(target_arch = "wasm32"))]
impl Thread for UniversalThread {
/// See [`Thread::spawn`].
fn spawn(f: impl FnOnce() + Send + 'static) {
thread::spawn(f);
}
/// See [`Thread::sleep`].
fn sleep(dur: Duration) {
thread::sleep(dur);
}
}
#[cfg(target_arch = "wasm32")]
struct WorkerContext {
func: Box<dyn FnOnce() + Send>,
}
#[cfg(target_arch = "wasm32")]
impl Thread for UniversalThread {
/// See [`Thread::spawn`].
fn spawn(f: impl FnOnce() + Send + 'static) {
let context = Box::into_raw(Box::new(WorkerContext { func: Box::new(f) })) as usize;
unsafe {
threadSpawn(context as u64);
}
}
/// See [`Thread::sleep`].
fn sleep(dur: Duration) {
thread::sleep(dur);
}
}
#[cfg(target_arch = "wasm32")]
extern "C" {
fn threadSpawn(context: u64);
}
#[cfg(target_arch = "wasm32")]
#[export_name = "runFunctionPointer"]
unsafe extern "C" fn fn_to_run_in_worker(ctx_ptr: u64) {
let ctx = Box::from_raw(ctx_ptr as *mut WorkerContext);
(ctx.func)();
}
/// Version of [`std::thread::spawn`] that also works in WebAssembly.
///
/// See also [`Thread::spawn`].
pub fn spawn(f: impl FnOnce() + Send + 'static) {
UniversalThread::spawn(f);
}
/// Universal version of [`std::thread::sleep`].
///
/// Note that this doesn't work properly in Safari: <https://bugs.webkit.org/show_bug.cgi?id=234833>
/// TODO(JP): If they don't fix this, we should make our own version using `Atomics.wait` in JS instead.
pub fn sleep(dur: Duration) {
UniversalThread::sleep(dur);
}