Audio: Clean up threading and add AudioStream fadein (RGSS3)

src/sdl-util.h

@@ -0,0 +1,48 @@
+#ifndef SDLUTIL_H
+#define SDLUTIL_H
+
+#include <SDL_atomic.h>
+#include <SDL_thread.h>
+
+#include <string>
+
+struct AtomicFlag
+{
+	AtomicFlag()
+	{
+		clear();
+	}
+
+	void set()
+	{
+		SDL_AtomicSet(&atom, 1);
+	}
+
+	void clear()
+	{
+		SDL_AtomicSet(&atom, 0);
+	}
+
+	operator bool() const
+	{
+		return SDL_AtomicGet(&atom);
+	}
+
+private:
+	mutable SDL_atomic_t atom;
+};
+
+template<class C, void (C::*func)()>
+int __sdlThreadFun(void *obj)
+{
+	(static_cast<C*>(obj)->*func)();
+	return 0;
+}
+
+template<class C, void (C::*func)()>
+SDL_Thread *createSDLThread(C *obj, const std::string &name = std::string())
+{
+	return SDL_CreateThread(__sdlThreadFun<C, func>, name.c_str(), obj);
+}
+
+#endif // SDLUTIL_H