Add thread pool scheduler (#159)

* Add thread pool scheduler

* Use event loop now

* Make negative time exception message consistent

* try sys wrap

* fix thread dodge

---------

Co-authored-by: Simon Krajewski <[email protected]>

std/haxe/coro/schedulers/ThreadPoolScheduler.hx

@@ -0,0 +1,57 @@
+package haxe.coro.schedulers;
+
+#if target.threaded
+import sys.thread.Thread;
+import sys.thread.IThreadPool;
+import haxe.Int64;
+import haxe.exceptions.ArgumentException;
+
+private class NoOpHandle implements ISchedulerHandle {
+	public function new() {}
+	public function close() {}
+}
+
+final class ThreadPoolScheduler extends Scheduler {
+	final pool : IThreadPool;
+
+	final thread : Thread;
+
+	final eventLoop : EventLoopScheduler;
+
+	public function new(pool) {
+		super();
+
+		this.pool      = pool;
+		this.eventLoop = new EventLoopScheduler();
+		this.thread    = Thread.create(keepAlive);
+	}
+
+	public function schedule(ms:Int64, func:()->Void):ISchedulerHandle {
+		if (ms < 0) {
+			throw new ArgumentException("Time must be greater or equal to zero");
+		}
+
+		if (0 == ms) {
+			pool.run(func);
+
+			return new NoOpHandle();
+		}
+
+		return eventLoop.schedule(ms, pool.run.bind(func));
+	}
+
+	public function scheduleObject(obj:IScheduleObject):Void {
+		pool.run(obj.onSchedule);
+	}
+
+	public function now() {
+		return eventLoop.now();
+	}
+
+	function keepAlive() {
+		while (true) {
+			eventLoop.run();
+		}
+	}
+}
+#end