extern uint64_t mtime_since(const struct timespec *, const struct timespec *);
extern uint64_t mtime_since_now(const struct timespec *);
extern uint64_t mtime_since_tv(const struct timeval *, const struct timeval *);
extern uint64_t mtime_since(const struct timespec *, const struct timespec *);
extern uint64_t mtime_since_now(const struct timespec *);
extern uint64_t mtime_since_tv(const struct timeval *, const struct timeval *);