feat: Initial clean release of CHM

packages/whisper-voice-typing/cpp/utils/SingleThread.cpp

@@ -0,0 +1,59 @@
+#include "SingleThread.hpp"
+#include "androidUtil.h"
+
+#include <condition_variable>
+#include <thread>
+#include <mutex>
+
+struct SingleThread::State_ {
+	std::vector<std::function<void()>> tasks;
+
+	// mutex_ and cv_ are used as a signaling mechanism.
+	// See, for example https://cplusplus.com/reference/condition_variable/condition_variable/
+	//                  https://en.cppreference.com/w/cpp/thread/condition_variable.html
+	std::condition_variable cv;
+    std::mutex mutex;
+
+	bool cancelled = false;
+};
+
+void threadLoop(std::shared_ptr<SingleThread::State_> state) {
+	while (!state->cancelled) {
+		// Create a lock that can be used by state->cv (see https://stackoverflow.com/a/13102893
+        // for why).
+		std::unique_lock lock {state->mutex};
+
+        // Run all tasks **first**, to handle the case where the threadLoop starts after the first
+        // task has been posted.
+		for (auto& task : state->tasks) {
+			task();
+		}
+		state->tasks.clear();
+
+		state->cv.wait(lock);
+	}
+}
+
+SingleThread::SingleThread()
+	: state_ { std::make_shared<State_>() },
+	  thread_ { threadLoop, state_ } {
+}
+
+SingleThread::~SingleThread() {
+	{
+		std::lock_guard lock { state_->mutex };
+		state_->cancelled = true;
+	}
+
+	state_->cv.notify_all();
+	thread_.join();
+}
+
+void SingleThread::post(std::function<void()> task) {
+	{
+		std::lock_guard lock { state_->mutex };
+		state_->tasks.push_back(std::move(task));
+	}
+	state_->cv.notify_all();
+}
+