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lib: posix: clock: Add read of CLOCK_REALTIME

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Add a private variable `rt_clock_base` that can be used to determine a
real-time clock by using the `k_uptime_get` clock.  Once `clock_settime`
is added, this can allow us to have a meaningful real time clock.

Signed-off-by: David Brown <david.brown@linaro.org>
This commit is contained in:
David Brown 2018-06-25 11:24:53 -06:00 • committed by Anas Nashif
commit 9921eb329d
1 changed files with 28 additions and 1 deletions
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29
lib/posix/clock.c
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@ -8,6 +8,15 @@
#include <posix/time.h>
#include <posix/sys/types.h>
/*
* `k_uptime_get` returns a timestamp based on an always increasing
* value from the system start. To support the `CLOCK_REALTIME`
* clock, this `rt_clock_base` records the time that the system was
* started. This can either be set via 'clock_settime', or could be
* set from a real time clock, if such hardware is present.
*/
static struct timespec rt_clock_base;
/**
* @brief Get clock time specified by clock_id.
*
@ -16,8 +25,19 @@
int clock_gettime(clockid_t clock_id, struct timespec *ts)
{
u64_t elapsed_msecs;
struct timespec base;
if (clock_id != CLOCK_MONOTONIC) {
switch (clock_id) {
case CLOCK_MONOTONIC:
base.tv_sec = 0;
base.tv_nsec = 0;
break;
case CLOCK_REALTIME:
base = rt_clock_base;
break;
default:
errno = EINVAL;
return -1;
}
@ -27,6 +47,13 @@ int clock_gettime(clockid_t clock_id, struct timespec *ts)
ts->tv_nsec = (s32_t) ((elapsed_msecs % MSEC_PER_SEC) *
USEC_PER_MSEC * NSEC_PER_USEC);
ts->tv_sec += base.tv_sec;
ts->tv_nsec += base.tv_nsec;
if (ts->tv_nsec > NSEC_PER_SEC) {
ts->tv_sec++;
ts->tv_nsec -= NSEC_PER_SEC;
}
return 0;
}