Getting a time difference in milliseconds - c++

Question

I´m trying to do something that I thought would be very simple but I have looked everywhere and I can´t figure it out. I´m also new to C++ and have no good understanding of templates and such.
I just need a function that measures the time from the program´s launch to a certain point in milliseconds, something like:
class timeCounter {
private:
long startTime;
long currentTime;
long timeDifference;
public:
long getTime();
}
timeCounter::timeCounter () {
startTime = time.now();
}
long timeCounter::getTimePassed () {
currentTime = time.now();
timeDifference = timeNow - timeStart;
return timeDifference;
}
I´ve tried with clock() / CLOCKS_PER_SECONDS but the result is slower than a second.
Can anyone help me out?
Thank you very much!

Answer 1

I was recently writing a similar system to get the delta time for a game engine.
Using the std::chrono library, here's an example:
#include <iostream>
#include <chrono>
#include <thread>
class timer
{
// alias our types for simplicity
using clock = std::chrono::system_clock;
using time_point_type = std::chrono::time_point < clock, std::chrono::milliseconds > ;
public:
// default constructor that stores the start time
timer()
{
start = std::chrono::time_point_cast<std::chrono::milliseconds>(clock::now());
}
// gets the time elapsed from construction.
long /*milliseconds*/ getTimePassed()
{
// get the new time
auto end = clock::now();
// return the difference of the times
return (end - start).count();
}
private:
time_point_type start;
};
int main()
{
timer t;
std::this_thread::sleep_for(std::chrono::seconds(5));
std::cout << t.getTimePassed();
std::cin.get();
}