Common: Move the Event class to a separate file, and add tests for it. Fix includes everywhere to match this.

Source/Core/Common/Event.h

@@ -0,0 +1,59 @@
+// Copyright 2014 Dolphin Emulator Project
+// Licensed under GPLv2
+// Refer to the license.txt file included.
+
+// Multithreaded event class. This allows waiting in a thread for an event to
+// be triggered in another thread. While waiting, the CPU will be available for
+// other tasks.
+// * Set(): triggers the event and wakes up the waiting thread.
+// * Wait(): waits for the event to be triggered.
+// * Reset(): tries to reset the event before the waiting thread sees it was
+//            triggered. Usually a bad idea.
+
+#pragma once
+
+#include "Common/StdConditionVariable.h"
+#include "Common/StdMutex.h"
+
+namespace Common {
+
+class Event
+{
+public:
+	Event()
+		: is_set(false)
+	{}
+
+	void Set()
+	{
+		std::lock_guard<std::mutex> lk(m_mutex);
+		if (!is_set)
+		{
+			is_set = true;
+			m_condvar.notify_one();
+		}
+	}
+
+	void Wait()
+	{
+		std::unique_lock<std::mutex> lk(m_mutex);
+		m_condvar.wait(lk, [&]{ return is_set; });
+		is_set = false;
+	}
+
+	void Reset()
+	{
+		std::unique_lock<std::mutex> lk(m_mutex);
+		// no other action required, since wait loops on
+		// the predicate and any lingering signal will get
+		// cleared on the first iteration
+		is_set = false;
+	}
+
+private:
+	volatile bool is_set;
+	std::condition_variable m_condvar;
+	std::mutex m_mutex;
+};
+
+}  // namespace Common