[SOLVED] how to divide timeval value by a number

kikilinux · 04-30-2016, 04:34 AM

I need to divide a timeval value by a number and save the results into tv_sec and tv_usec.
I don’t how to do this in c++.

any suggestions would be greatly appreciated.

tshikose · 05-01-2016, 02:09 PM

Hi,

It will be great if you share with us what you have tried so far (and how it failed).

NevemTeve · 05-01-2016, 02:17 PM

If it were me, I would divide by 1000000, because 'usec' means 10^(-6) sec

sundialsvcs · 05-01-2016, 09:35 PM

Consider pages such as this: http://www.tutorialspoint.com/cplusp..._date_time.htm.

"Time manipulation," of any sort, is often handled through standard libraries and/or objects. The math is easy to get wrong, and you know that somebody else(!) already got it right . . .

kikilinux · 05-03-2016, 11:22 PM

I used this solution to multiply time which I get from pcap file packets timestamp:

Code:

if(byte_rate < 1)       // multiply with a value smaller than one
    {
        new_tv.tv_sec = new_tv.tv_sec * (1/byte_rate) + (new_tv.tv_usec * (1/byte_rate)) / ONE_MILION;
        new_tv.tv_usec = (new_tv.tv_usec * (rate / new_rate)) % ONE_MILION;
    }
    else                    // multiply with a value bigger than one
    {

        double m, fracpart, intpart;
        m = (long double)new_tv.tv_sec / byte_rate;
        // separate fractional part from integer part
        fracpart = modf (m , &intpart);
        // Add results of fractional part of SECOND to MICRO SECOND with MICRO SECOND division
        new_tv.tv_usec = (fracpart * ONE_MILION) + (new_tv.tv_usec / (byte_rate));
        // Set integer part of division of SECOND part by byterate to packet tv_sec
        new_tv.tv_sec = intpart;
    }

here byterate is a value bigger or smaller than one. the if portion multiplies timestamp to a value bigger than one and the else portion multiply timestamp to a value smaller than one.

rtmistler · 05-04-2016, 02:49 PM

Quote:

Originally Posted by kikilinux

I need to divide a timeval value by a number and save the results into tv_sec and tv_usec.
I don’t how to do this in c++.

any suggestions would be greatly appreciated.

What language do you know how to do this in? C? Same way in C++ as in C.