Question

I need to convert time from one format to another in C++ and it must be cross-platform compatible. I have created a structure as my time container. The structure fields must also be unsigned int as specified by legacy code.

struct time{   
unsigned int timeInteger;   
unsigned int timeFraction;
} time1, time2;

Mathematically the conversion is as follows:

time2.timeInteger = time1.timeInteger + 2208988800

time2.timeFraction = (time1.timeFraction * 20e-6) * 2e32

Here is my original code in C++ however when I attempt to write to a binary file, the converted time does not match with the truth data. I think this problem is due to a type casting mistake? This code will compile in VS2008 and will execute.

void convertTime(){
   time2.timeInteger  = unsigned int(time1.timeInteger + 2209032000);
   time2.timeFraction = unsigned int(double(time1.timeFraction) * double(20e-6)*double(pow(double(2),32)));
}

Answer 1

Just a guess, but are you assuming that 2e32 == 2^32? This assumption would make sense if you’re trying to scale the result into a 32 bit integer. In fact 2e32 == 2 * 10^32