|
|
#include <time.h>int timer_settime(timer_t timerid, int flags, const struct itimerspec *value, struct itimerspec *ovalue);
int timer_gettime(timer_t timerid, struct itimerspec *value);
int timer_getoverrun(timer_t timerid);
timer_gettime- get process timer
timer_getoverrun- return timer overrun count
The timer_settime function sets the time until the next
expiration of the timer specified by timerid. The time is
set from the it_value member of the value
argument. The timer is armed if the it_value member of
value is non-zero. If the specified timer was already
armed when timer_settime is called, this call resets the
time until next expiration to the value specified. If the
it_value member of value is zero, the timer is
disarmed.
If the flag TIMER_ABSTIME is not set in the argument
flags, timer_settime behaves as if the time
until next expiration is set equal to the interval specified by the
it_value member of value: that is, the timer
expires in it_value nanoseconds (see Section 14.1.1 of
IEEE Std 1003.1b-1993) from when the call is made. If the
flag TIMER_ABSTIME is set in the argument flags,
timer_settime behaves as if the time until next expiration
is set equal to the difference between the absolute time specified
by the it_value member of value and the current
value of the clock associated with timerid: that is, the
timer expires when the clock reaches the value specified by the
it_value member of value. If the specified time
has already passed, the function succeeds and the expiration
notification is made.
The reload value of the timer is set to the value specified by the
it_interval member of value. When a timer is
armed with a non-zero it_interval, a periodic (or
repetitive) timer is specified.
Time values that are between two consecutive non-negative integer multiples of the resolution of the specified timer are rounded up to the larger multiple of the resolution. Quantization error does not cause the timer to expire earlier than the rounded-up time value.
If the argument ovalue is not NULL, the function timer_settime stores, in the location referenced by ovalue, a value representing the previous amount of time before the timer would have expired or zero if the timer was disarmed, together with the previous timer reload value. The members of ovalue are subject to the resolution of the timer, and are the same values that would be returned by a timer_gettime call at that point in time.
The timer_gettime function stores the amount of time until
the specified timer, timerid, expires and the timer's
reload value into the space pointed to by the value
argument. The it_value member of this structure contains
the amount of time before the timer expires, or zero if the timer is
disarmed. This value is returned as the interval until timer
expiration, even if the timer was armed with absolute time. The
it_interval member of value contains the reload
value last set by timer_settime.
Only a single signal is queued to the process for a given timer at any point in time. When a timer for which a signal is still pending expires, no signal is queued, and a timer overrun occurs. The timer_getoverrun function returns the timer expiration overrun count for the timer specified by the timerid argument. The overrun count returned contains the number of extra timer expirations which occurred between the time the signal was generated (queued) and when it was delivered, up to but not including {DELAYTIMER_MAX}. If the number of such extra expirations is greater than or equal to {DELAYTIMER_MAX}, then the overrun count is set to {DELAYTIMER_MAX}. The value returned by timer_getoverrun applies to the most recent expiration signal delivery for the timer.