Linux timer code

timer.h

#include <stdio.h>
#include <time.h>

// calculate time in seconds between two timespecs

inline double time_diff(timespec start, timespec end)
{
    timespec temp;
    if ((end.tv_nsec-start.tv_nsec)<0) {
        temp.tv_sec = end.tv_sec-start.tv_sec-1;
        temp.tv_nsec = 1000000000+end.tv_nsec-start.tv_nsec;
    } else {
        temp.tv_sec = end.tv_sec-start.tv_sec;
        temp.tv_nsec = end.tv_nsec-start.tv_nsec;
    }
    
    double t = temp.tv_sec;
    double ns = temp.tv_nsec;
    t += ns*1e-9;
    return t;
}

class Timer {
private:
    timespec starttime; //!< timespec of initialisation time
    timespec marktime; //!< timespec of the mark
public:
    Timer(){
        clock_gettime(CLOCK_MONOTONIC,&starttime);
    }
    
    /// return the time since object construction in seconds
    double timeSinceStart(){
        struct timespec now;
        clock_gettime(CLOCK_MONOTONIC,&now);
        return time_diff(starttime,now);
    }
    
    /// set the mark time
    void mark(){
        clock_gettime(CLOCK_MONOTONIC,&marktime);
    }
    
    /// return the time since mark() in seconds
    double timeSinceMark(){
        struct timespec now;
        clock_gettime(CLOCK_MONOTONIC,&now);
        return time_diff(marktime,now);
    }
        
};