gistfile1.hpp

class TimeAccum
{
    public:
    TimeAccum(int frequency) : time_previous(0), accum_delta_error(0), accum_time(0), time(0)
    {
        /* frequency is updates / sec, for example 30 or 60 fps */
        /* almost everything is 15.16Q fixedpoint */
        timestep = 65536 / frequency;
    }
    void advanceTime()
    {
        int time_current = SDL_GetTicks();
        int deltatmp = (time_current - time_previous) * 65536; /* 65536000/s */
        time_previous = time_current;
        
        /*SDL_GetTicks returns milliseconds (1/1000). We want 1/65536 */
        int delta = deltatmp / 1000;
        int delta_error = deltatmp % 1000;
        /* save the error (remainder)*/
        accum_delta_error += delta_error;
        if(accum_delta_error >= 1000){
            ++delta; /* Increase delta by 1, if the accumulated remainders becomes "one whole" */
            accum_delta_error -= 1000;
        }
        accum_time += delta;
        while(accum_time >= timestep)
        {
            accum_time -= timestep;
            time += timestep;
            think(time); /* remember to divide by 65536 */
        }
    }
private:
    int time_previous;
    int timestep;
    int accum_delta_error;
    int accum_time;
    int time;
};