added stop watch

nufi/stopwatch.h

@@ -0,0 +1,37 @@
+#ifndef STOPWATCH_H
+#define STOPWATCH_H
+
+#include <chrono>
+
+template <typename real>
+class stopwatch
+{
+public:
+	void reset();
+	real elapsed();
+
+private:
+	using clock = std::chrono::high_resolution_clock;
+	clock::time_point t0 { clock::now() };
+};
+
+
+template <typename real> inline
+void stopwatch<real>::reset()
+{
+	t0 = clock::now();
+}
+
+template <typename real> inline
+real stopwatch<real>::elapsed()
+{
+	using seconds = std::chrono::duration<real,std::ratio<1,1>>;
+
+	auto tnow = clock::now();
+	auto duration = std::chrono::duration_cast<seconds>( tnow - t0 );
+
+	return duration.count();
+}
+
+#endif // STOPWATCH_H
+