// Returns the amount of milliseconds elapsed since the UNIX epoch. Works on both
// windows and linux.

uint64 GetTimeMs64()
{
#ifdef _WIN32
// Windows
FILETIME ft;
LARGE_INTEGER li;

// Get the amount of 100 nano seconds intervals elapsed since January 1, 1601 (UTC) and copy it
// to a LARGE_INTEGER structure.
GetSystemTimeAsFileTime(&ft);
li.LowPart = ft.dwLowDateTime;
li.HighPart = ft.dwHighDateTime;

uint64 ret = li.QuadPart;
ret -= 116444736000000000LL; // Convert from file time to UNIX epoch time.
ret /= 10000; // From 100 nano seconds (10^-7) to 1 millisecond (10^-3) intervals

return ret;
#else
// Linux
struct timeval tv;

gettimeofday(&tv, NULL);

uint64 ret = tv.tv_usec;
// Convert from micro seconds (10^-6) to milliseconds (10^-3)
ret /= 1000;

// Adds the seconds (10^0) after converting them to milliseconds (10^-3)
ret += (tv.tv_sec * 1000);

return ret;
#endif
}