event/DeferredMonitor: new class wrapping g_idle_add()

Makefile.am

@@ -297,6 +297,7 @@ libevent_a_SOURCES = \
 	src/event/WakeFD.hxx \
 	src/event/SignalMonitor.hxx src/event/SignalMonitor.cxx \
 	src/event/TimeoutMonitor.hxx src/event/TimeoutMonitor.cxx \
+	src/event/DeferredMonitor.hxx src/event/DeferredMonitor.cxx \
 	src/event/SocketMonitor.cxx src/event/SocketMonitor.hxx \
 	src/event/BufferedSocket.cxx src/event/BufferedSocket.hxx \
 	src/event/FullyBufferedSocket.cxx src/event/FullyBufferedSocket.hxx \

src/GlobalEvents.cxx

@@ -19,6 +19,8 @@
 
 #include "config.h"
 #include "GlobalEvents.hxx"
+#include "util/Manual.hxx"
+#include "event/DeferredMonitor.hxx"
 #include "gcc.h"
 
 #include <atomic>
@@ -30,7 +32,13 @@
 #define G_LOG_DOMAIN "global_events"
 
 namespace GlobalEvents {
-	static guint source_id;
+	class Monitor final : public DeferredMonitor {
+	protected:
+		virtual void Run() override;
+	};
+
+	static Manual<Monitor> monitor;
+
 	static std::atomic_uint flags;
 	static Handler handlers[MAX];
 }
@@ -47,29 +55,27 @@ InvokeGlobalEvent(GlobalEvents::Event event)
 	GlobalEvents::handlers[event]();
 }
 
-static gboolean
-GlobalEventCallback(gcc_unused gpointer data)
+void
+GlobalEvents::Monitor::Run()
 {
-	const unsigned flags = GlobalEvents::flags.exchange(0);
+	const unsigned f = flags.exchange(0);
 
-	for (unsigned i = 0; i < GlobalEvents::MAX; ++i)
-		if (flags & (1u << i))
+	for (unsigned i = 0; i < MAX; ++i)
+		if (f & (1u << i))
 			/* invoke the event handler */
-			InvokeGlobalEvent(GlobalEvents::Event(i));
-
-	return false;
+			InvokeGlobalEvent(Event(i));
 }
 
 void
 GlobalEvents::Initialize()
 {
+	monitor.Construct();
 }
 
 void
 GlobalEvents::Deinitialize()
 {
-	if (source_id != 0)
-		g_source_remove(source_id);
+	monitor.Destruct();
 }
 
 void
@@ -88,5 +94,5 @@ GlobalEvents::Emit(Event event)
 
 	const unsigned mask = 1u << unsigned(event);
 	if (GlobalEvents::flags.fetch_or(mask) == 0)
-		source_id = g_idle_add(GlobalEventCallback, nullptr);
+		monitor->Schedule();
 }

src/event/DeferredMonitor.cxx

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * 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 "config.h"
+#include "DeferredMonitor.hxx"
+#include "Loop.hxx"
+
+void
+DeferredMonitor::Cancel()
+{
+	const auto id = source_id.exchange(0);
+	if (id != 0)
+		g_source_remove(id);
+}
+
+void
+DeferredMonitor::Schedule()
+{
+	const unsigned id = g_idle_add(Callback, this);
+	const auto old_id = source_id.exchange(id);
+	if (old_id != 0)
+		g_source_remove(old_id);
+}
+
+void
+DeferredMonitor::DoRun()
+{
+	const auto id = source_id.exchange(0);
+	if (id != 0)
+		Run();
+}
+
+gboolean
+DeferredMonitor::Callback(gpointer data)
+{
+	DeferredMonitor &monitor = *(DeferredMonitor *)data;
+	monitor.Run();
+	return false;
+}

src/event/DeferredMonitor.hxx

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * 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 MPD_SOCKET_DEFERRED_MONITOR_HXX
+#define MPD_SOCKET_DEFERRED_MONITOR_HXX
+
+#include "check.h"
+
+#include <glib.h>
+
+#include <atomic>
+
+/**
+ * Defer execution of an event into an #EventLoop.
+ */
+class DeferredMonitor {
+	std::atomic<guint> source_id;
+
+public:
+	DeferredMonitor()
+		:source_id(0) {}
+
+	~DeferredMonitor() {
+		Cancel();
+	}
+
+	void Schedule();
+	void Cancel();
+
+protected:
+	virtual void Run() = 0;
+
+private:
+	void DoRun();
+	static gboolean Callback(gpointer data);
+};
+
+#endif /* MAIN_NOTIFY_H */