TIMEVAL(3) | Library Functions Manual | TIMEVAL(3) |
void
TIMEVAL_TO_TIMESPEC(struct timeval *tv, struct timespec *ts);
void
TIMESPEC_TO_TIMEVAL(struct timeval *tv, struct timespec *ts);
struct timeval { time_t tv_sec; suseconds_t tv_usec; };
The tv_sec member represents the elapsed time, in whole seconds. The tv_usec member captures rest of the elapsed time, represented as the number of microseconds.
struct timespec { time_t tv_sec; long tv_nsec; };
The tv_sec member is again the elapsed time in whole seconds. The tv_nsec member represents the rest of the elapsed time in nanoseconds.
A microsecond is equal to one millionth of a second, 1000 nanoseconds, or 1/1000 milliseconds. To ease the conversions, the macros TIMEVAL_TO_TIMESPEC() and TIMESPEC_TO_TIMEVAL() can be used to convert between struct timeval and struct timespec.
struct itimerval { struct timeval it_interval; struct timeval it_value; };
struct itimerspec { struct timespec it_interval; struct timespec it_value; };
Both struct itimerval and struct itimerspec are used to specify when a timer expires. Generally, it_interval specifies the period between successive timer expirations. A value zero implies that the alarm will fire only once. If it_value is non-zero, it indicates the time left to the next timer expiration. A value zero implies that the timer is disabled.
struct bintime { time_t sec; uint64_t frac; };
The sec member specifies the time in seconds and frac represents a 64-bit fraction of seconds. The struct bintime is meant to be used in the kernel only. It is further described in timecounter(9).
static void example(struct timespec *spec, time_t minutes) { struct timeval elapsed; (void)gettimeofday(&elapsed, NULL); _DIAGASSERT(spec != NULL); TIMEVAL_TO_TIMESPEC(&elapsed, spec); /* Add the offset for timeout in minutes. */ spec->tv_sec = spec->tv_sec + minutes * 60; }
A better alternative would use the more precise clock_gettime(2).
April 12, 2011 | NetBSD 6.1 |