use std::thread::{self, JoinHandle};
/// Spawns a new thread with the given code, or executes it directly if the
/// environment variable `PERSEUS_CLI_SEQUENTIAL` is set to any valid (Unicode)
/// value. Multithreading is the default.
pub fn spawn_thread<F, T>(f: F, sequential: bool) -> ThreadHandle<F, T>
where
F: FnOnce() -> T,
F: Send + 'static,
T: Send + 'static,
{
if sequential {
ThreadHandle {
join_handle: None,
f: Some(f),
}
} else {
let join_handle = thread::spawn(f);
ThreadHandle {
join_handle: Some(join_handle),
f: None,
}
}
}
/// An abstraction over a `JoinHandle` in a multithreaded case, or just a
/// similar interface that will immediately return if otherwise. This allows the
/// interfaces for multithreading and single-threading to be basically
/// identical.
pub struct ThreadHandle<F, T>
where
F: FnOnce() -> T,
F: Send + 'static,
T: Send + 'static,
{
/// If multithreaded, this is the join handle.
join_handle: Option<JoinHandle<T>>,
// If single-threaded, this is the output (it's already been executed).
f: Option<F>,
}
impl<F, T> ThreadHandle<F, T>
where
F: FnOnce() -> T,
F: Send + 'static,
T: Send + 'static,
{
/// Waits for the 'thread' to complete, properly if it's multithreaded, or
/// by direct execution if it's single-threaded.
pub fn join(
self,
) -> Result<T, std::boxed::Box<(dyn std::any::Any + std::marker::Send + 'static)>> {
if let Some(join_handle) = self.join_handle {
join_handle.join()
} else if let Some(f) = self.f {
let output = f();
Ok(output)
} else {
unreachable!();
}
}
}