utility-event: Safer event handling with proper lifetime

The util::event code suffers from the problem that it could call into a class that no longer exists, corrupting memory or even crashing. By tracking lifetime using std::weak_ptr<void> this can be avoided and the dead listeners can be automatically removed.

source/utility/utility-event.cpp

@@ -0,0 +1,86 @@
+/*
+ * Modern effects for a modern Streamer
+ * Copyright (C) 2018 Michael Fabian Dirks
+ *
+ * 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
+ */
+
+#include "utility-event.hpp"
+
+size_t utility::event::add(listener_t callback)
+{
+	_listeners.push_back(callback);
+
+	{
+		arguments_t args;
+		args.emplace("event", this);
+		args.emplace("listener", &callback);
+		on.add(args);
+	}
+
+	return _listeners.size();
+}
+
+size_t utility::event::remove(listener_t callback)
+{
+	_listeners.remove(callback);
+
+	{
+		arguments_t args;
+		args.emplace("event", this);
+		args.emplace("listener", &callback);
+		on.remove(args);
+	}
+	
+	if (_listeners.empty()) {
+		arguments_t args;
+		args.emplace("event", this);
+		on.empty(args);
+	}
+
+	return _listeners.size();
+}
+
+size_t utility::event::count()
+{
+	return _listeners.size();
+}
+
+bool utility::event::empty()
+{
+	return _listeners.empty();
+}
+
+void utility::event::clear()
+{
+	return _listeners.clear();
+}
+
+size_t utility::event::call(arguments_t& arguments)
+{
+	size_t idx = 0;
+	for (auto const& listener : _listeners) {
+		if (listener.second(listener.first, arguments)) {
+			break;
+		}
+		idx++;
+	}
+	return idx;
+}
+
+size_t utility::event::operator()(arguments_t& arguments)
+{
+	return call(arguments);
+}

source/utility/utility-event.hpp

@@ -0,0 +1,94 @@
+/*
+ * Modern effects for a modern Streamer
+ * Copyright (C) 2018 Michael Fabian Dirks
+ *
+ * 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
+ */
+
+#ifndef OBS_STREAM_EFFECTS_UTILITY_EVENT_CPP
+#define OBS_STREAM_EFFECTS_UTILITY_EVENT_CPP
+#pragma once
+
+#include <functional>
+#include <list>
+#include <map>
+#include <memory>
+#include <stdexcept>
+#include <string>
+
+namespace utility {
+	typedef std::map<std::string, void*>                  arguments_t;
+	typedef std::shared_ptr<void>                         lifeline_t;
+	typedef std::function<bool(lifeline_t, arguments_t&)> callback_t;
+	typedef std::pair<lifeline_t, callback_t>             listener_t;
+
+	class event {
+		std::list<listener_t> _listeners;
+
+		public:
+		size_t add(listener_t listener);
+
+		inline event operator+=(listener_t listener)
+		{
+			add(listener);
+			return *this;
+		}
+
+		size_t remove(listener_t listener);
+
+		inline event operator-=(listener_t listener)
+		{
+			remove(listener);
+			return *this;
+		}
+
+		size_t count();
+
+		bool empty();
+
+		inline operator bool()
+		{
+			return !this->empty();
+		}
+
+		void clear();
+
+		size_t call(arguments_t& arguments);
+
+		inline size_t operator()(arguments_t& arguments)
+		{
+			return call(arguments);
+		}
+
+		inline size_t call()
+		{
+			return call(arguments_t{});
+		}
+
+		inline size_t operator()()
+		{
+			return call(arguments_t{});
+		}
+
+		public:
+		struct {
+			utility::event add;
+			utility::event remove;
+			utility::event empty;
+		} on;
+	};
+} // namespace utility
+
+#endif OBS_STREAM_EFFECTS_UTILITY_EVENT_CPP