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timer_set.md

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zx_timer_set

NAME

timer_set - start a timer

SYNOPSIS

#include <zircon/syscalls.h>

zx_status_t zx_timer_set(zx_handle_t handle,
                         zx_time_t deadline,
                         zx_duration_t slack);

DESCRIPTION

zx_timer_set() starts a one-shot timer that will fire when deadline passes. If a previous call to zx_timer_set() was pending, the previous timer is canceled and ZX_TIMER_SIGNALED is de-asserted as needed.

The deadline parameter specifies a deadline with respect to ZX_CLOCK_MONOTONIC. To wait for a relative interval, use zx_deadline_after() returned value in deadline.

To fire the timer immediately pass a deadline less than or equal to 0.

When the timer fires it asserts ZX_TIMER_SIGNALED. To de-assert this signal call zx_timer_cancel() or zx_timer_set() again.

The slack parameter specifies a range from deadline - slack to deadline + slack during which the timer is allowed to fire. The system uses this parameter as a hint to coalesce nearby timers.

The precise coalescing behavior is controlled by the options parameter specified when the timer was created. ZX_TIMER_SLACK_EARLY allows only firing in the deadline - slack interval and ZX_TIMER_SLACK_LATE allows only firing in the deadline + slack interval. The default option value of 0 is ZX_TIMER_SLACK_CENTER and allows both early and late firing with an effective interval of deadline - slack to deadline + slack

RIGHTS

handle must be of type ZX_OBJ_TYPE_TIMER and have ZX_RIGHT_WRITE.

RETURN VALUE

zx_timer_set() returns ZX_OK on success. In the event of failure, a negative error value is returned.

ERRORS

ZX_ERR_BAD_HANDLE handle is not a valid handle.

ZX_ERR_ACCESS_DENIED handle lacks the right ZX_RIGHT_WRITE.

ZX_ERR_OUT_OF_RANGE slack is negative.

SEE ALSO