Further decoupled recommendation engine: it now has its own thread

src/libs/utils/impl/Logger.cpp

@@ -34,7 +34,7 @@ const char* getModuleName(Module mod)
 		case Module::METADATA:		return "METADATA";
 		case Module::REMOTE:		return "REMOTE";
 		case Module::SERVICE:		return "SERVICE";
-		case Module::SIMILARITY:	return "SIMILARITY";
+		case Module::RECOMMENDATION:	return "RECOMMENDATION";
 		case Module::TRANSCODE:		return "TRANSCODE";
 		case Module::UI:		return "UI";
 	}

src/libs/utils/include/utils/Logger.hpp

@@ -46,7 +46,7 @@ enum class Module
 	METADATA,
 	REMOTE,
 	SERVICE,
-	SIMILARITY,
+	RECOMMENDATION,
 	TRANSCODE,
 	UI,
 };

src/libs/utils/include/utils/Semaphore.hpp

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2020 Emeric Poupon
+ *
+ * This file is part of LMS.
+ *
+ * LMS is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * LMS is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with LMS.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <mutex>
+#include <condition_variable>
+
+class Semaphore
+{
+	public:
+		Semaphore() = default;
+		Semaphore(const Semaphore&) = delete;
+		Semaphore(Semaphore&&) = delete;
+		Semaphore& operator=(const Semaphore&) = delete;
+		Semaphore& operator=(Semaphore&&) = delete;
+
+		void notify()
+		{
+			std::unique_lock<std::mutex> lock {_mutex};
+
+			_count++;
+			_cv.notify_one();
+		}
+
+		void wait()
+		{
+			std::unique_lock<std::mutex> lock(_mutex);
+
+			while (_count == 0)
+				_cv.wait(lock);
+
+			_count--;
+		}
+
+	private:
+		std::mutex			_mutex;
+		std::condition_variable		_cv;
+		unsigned			_count {};
+};
+
+