event: Improve event code

include/event.hpp

@@ -1,19 +1,20 @@
 /*
-Low Latency IPC Library for high-speed traffic
-Copyright (C) 2019 Michael Fabian Dirks <info@xaymar.com>
-
-This program is free software: you can redistribute it and/or modify
-it under the terms of the GNU Affero General Public License as published
-by the Free Software Foundation, either version 3 of the License, or
-(at your option) any later version.
-
-This program 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 Affero General Public License for more details.
-
-You should have received a copy of the GNU Affero General Public License
-along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ * Low Latency IPC Library for high-speed traffic
+ * Copyright (C) 2017-2019 Michael Fabian Dirks <info@xaymar.com>
+ *
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
  */
 
 #pragma once
@@ -25,40 +26,94 @@ namespace datapath {
 	class event {
 		std::list<std::function<void(_args...)>> listeners;
 
-		public:
-		void add(std::function<void(_args...)> listener)
+		std::function<void()> listen_cb;
+		std::function<void()> silence_cb;
+
+		public /* functions */:
+
+		// Destructor
+		inline ~event()
 		{
+			this->clear();
+		}
+
+		// Add new listener.
+		inline void add(std::function<void(_args...)> listener)
+		{
+			if (listeners.size() == 0) {
+				if (listen_cb) {
+					listen_cb();
+				}
+			}
 			listeners.push_back(listener);
 		}
 
-		void remove(std::function<void(_args...)> listener)
+		// Remove existing listener.
+		inline void remove(std::function<void(_args...)> listener)
 		{
 			listeners.remove(listener);
+			if (listeners.size() == 0) {
+				if (silence_cb) {
+					silence_cb();
+				}
+			}
 		}
 
-		// Not valid without the extra template.
+		// Check if empty / no listeners.
+		inline bool empty()
+		{
+			return listeners.empty();
+		}
+
+		// Remove all listeners.
+		inline void clear()
+		{
+			listeners.clear();
+			if (silence_cb) {
+				silence_cb();
+			}
+		}
+
+		public /* operators */:
+		// Call Listeners with arguments.
+		/// Not valid without the extra template.
 		template<typename... _largs>
-		void operator()(_args... args)
+		inline void operator()(_args... args)
 		{
 			for (auto& l : listeners) {
 				l(args...);
 			}
 		}
 
-		operator bool()
+		// Convert to bool (true if not empty, false if empty).
+		inline operator bool()
 		{
-			return !listeners.empty();
+			return !this->empty();
 		}
 
-		public:
-		bool empty()
+		// Add new listener.
+		inline event<_args...>& operator+=(std::function<void(_args...)> listener)
 		{
-			return listeners.empty();
+			this->add(listener);
+			return *this;
 		}
 
-		void clear()
+		// Remove existing listener.
+		inline event<_args...>& operator-=(std::function<void(_args...)> listener)
 		{
-			listeners.clear();
+			this->remove(listener);
+			return *this;
+		}
+
+		public /* events */:
+		void set_listen_callback(std::function<void()> cb)
+		{
+			this->listen_cb = cb;
+		}
+
+		void set_silence_callback(std::function<void()> cb)
+		{
+			this->silence_cb = cb;
 		}
 	};
 }; // namespace datapath