c get time in milliseconds
#include <sys/time.h>
long long current_timestamp() {
struct timeval te;
gettimeofday(&te, NULL); // get current time
long long milliseconds = te.tv_sec*1000LL + te.tv_usec/1000; // calculate milliseconds
// printf("milliseconds: %lld\n", milliseconds);
return milliseconds;
}