output/pulse: use a RTTI lock guard

Make all the locks exception-safe.

src/lib/pulse/LockGuard.hxx

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2003-2016 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_PULSE_LOCK_GUARD_HXX
+#define MPD_PULSE_LOCK_GUARD_HXX
+
+#include <pulse/thread-mainloop.h>
+
+namespace Pulse {
+
+class LockGuard {
+	struct pa_threaded_mainloop *const mainloop;
+
+public:
+	explicit LockGuard(struct pa_threaded_mainloop *_mainloop)
+		:mainloop(_mainloop) {
+		pa_threaded_mainloop_lock(mainloop);
+	}
+
+	~LockGuard() {
+		pa_threaded_mainloop_unlock(mainloop);
+	}
+
+	LockGuard(const LockGuard &) = delete;
+	LockGuard &operator=(const LockGuard &) = delete;
+};
+
+};
+
+#endif