extern uint64_t utime_since(struct timeval *, struct timeval *);
extern uint64_t utime_since_now(struct timeval *);
extern uint64_t mtime_since(struct timeval *, struct timeval *);
extern uint64_t utime_since(struct timeval *, struct timeval *);
extern uint64_t utime_since_now(struct timeval *);
extern uint64_t mtime_since(struct timeval *, struct timeval *);