The Scale program uses the Boost::ASIO libraries in order to execute the functions in async fashion. It also uses mutiple threads to have io.services run in each of them. I have Interfacing the C++ code with C wrapper .

scale.cpp

#include <boost/asio.hpp> 
#include <boost/thread.hpp> 
#include <iostream> 





class Foo {
	
	public:

	static boost::asio::io_service io_service1; 
	static boost::asio::io_service io_service2;

	static void handler1(const boost::system::error_code &ec) 
	{ 
	  std::cout << "5 s." << std::endl; 
	} 

	static void handler2(const boost::system::error_code &ec) 
	{ 
	  std::cout << "5 s." << std::endl; 
	} 

	static void run1() 
	{ 
	  io_service1.run(); 
	} 

	static void run2() 
	{ 
	  io_service2.run(); 
	} 

	void run()
	{

	boost::asio::deadline_timer timer1(Foo::io_service1, boost::posix_time::seconds(5)); 
	timer1.async_wait(Foo::handler1); 
	boost::asio::deadline_timer timer2(Foo::io_service2, boost::posix_time::seconds(5)); 
	timer2.async_wait(Foo::handler2); 
	boost::thread thread1(Foo::run1); 
	boost::thread thread2(Foo::run2); 
	thread1.join(); 
	thread2.join(); 
	}



};

boost::asio::io_service Foo::io_service1; 
boost::asio::io_service Foo::io_service2; 


extern "C" {
   Foo* Foo_new(){ return new Foo(); }
   void Foo_run(Foo* foo){ foo->run(); }
}	


int main()
{
	
	Foo *f = new Foo();
	f->run();

}