osthread: init

osthread/osthread.go

@@ -0,0 +1,70 @@
+// Package osthread allows functions to be called on the main operating system thread.
+//
+// Usage:
+//
+//	func main() {
+//		osthread.Start(Entrypoint) // Initialize osthread and calls Entrypoint. Blocks until Entrypoint returns.
+//	}
+//
+//	func Entrypoint() {
+//		osthread.Call(FuncA) // Call FuncA on the main operating system thread, block until it returns
+//		// ...
+//		osthread.Go(FuncB) // Schedule FuncB to be called on the main operating system thread
+//		// ...
+//	}
+package osthread
+
+import "runtime"
+
+// Start allows arbitrary functions to be run on the main operating system thread.
+//
+// Start must be called from the program's main function. Once called, it blocks until entrypoint returns.
+func Start(entrypoint func()) {
+	done := make(chan any)
+
+	// Run entrypoint in a separate goroutine.
+	go func() {
+		defer func() {
+			done <- nil
+		}()
+
+		entrypoint()
+	}()
+
+	// Call functions in our queue until entrypoint returns.
+	// These functions are called on the main operating system thread.
+	for {
+		select {
+		case fn := <-queue:
+			fn()
+		case <-done:
+			return
+		}
+	}
+}
+
+// Go schedules a function to be run on the main operating system thread, returning immediately.
+func Go(fn func()) {
+	queue <- fn
+}
+
+// Call schedules a function to be run on the main operating system thread, blocking until it returns.
+func Call(fn func()) {
+	done := make(chan any)
+	queue <- func() {
+		defer func() {
+			done <- nil
+		}()
+
+		fn()
+	}
+
+	<-done
+}
+
+var queue chan func()
+
+func init() {
+	runtime.LockOSThread()
+	queue = make(chan func(), runtime.GOMAXPROCS(0))
+}