High resolution timer for algorithm development

timer.cpp

#include "timer.hpp"

using namespace std;
using namespace std::chrono;

timer::timer()
{
	this->hasRun = false;
	this->start = high_resolution_clock::now();
}

void timer::stop()
{	
	this->assert_timer_is_running();
	this->end = high_resolution_clock::now();
	this->hasRun = true;
}

unsigned int timer::nanoseconds()
{
	this->assert_timer_is_stopped();
	return duration_cast<chrono::nanoseconds>(this->end - this->start).count();
}

unsigned int timer::microseconds()
{
	this->assert_timer_is_stopped();
	return duration_cast<chrono::microseconds>(this->end - this->start).count();
}

unsigned int timer::milliseconds()
{
	this->assert_timer_is_stopped();
	return duration_cast<chrono::milliseconds>(this->end - this->start).count();
}

unsigned int timer::seconds()
{
	this->assert_timer_is_stopped();
	return duration_cast<chrono::seconds>(this->end - this->start).count();
}

void timer::assert_timer_is_running()
{
	if (this->hasRun)
		throw "Cannot stop timer that has already been stopped.";
}

void timer::assert_timer_is_stopped()
{
	if (!this->hasRun)
		throw "Cannot get elapsed time of still-running timer.";
}

timer.hpp

#ifndef TIMER_HPP
#define TIMER_HPP

#include <chrono>

class timer
{
private:
	std::chrono::high_resolution_clock::time_point start;
	std::chrono::high_resolution_clock::time_point end;
	bool hasRun;

public:
	timer();
	void stop();
	unsigned int nanoseconds();
	unsigned int microseconds();
	unsigned int milliseconds();
	unsigned int seconds();

private:
	void assert_timer_is_running();
	void assert_timer_is_stopped();
};

#endif // !TIMER_HPP