Timer library¶

The timer library provides functions for setting, resetting and restarting timers, and for checking if a timer has expired. An application must "manually" check if its timers have expired; this is not done automatically.

A timer is declared as a struct timer and all access to the timer is made by a pointer to the declared timer.

Note

The timer library is not able to post events when a timer expires. The Event timers should be used for this purpose.

Note

The timer library uses the Clock library to measure time. Intervals should be specified in the format used by the clock library.

Structs¶

timer¶

A timer.

This structure is used for declaring a timer. The timer must be set with timer_set() before it can be used.

Name	Type	Description
`start`	`clock_time_t`
`interval`	`clock_interval_t`

Functions¶

timer_set¶

void timer_set(struct timer *t, clock_interval_t interval);

Set a timer.

This function is used to set a timer for a time sometime in the future. The function timer_expired() will evaluate to true after the timer has expired.

Parameters¶

Name	Description
t	A pointer to the timer.
interval	The interval before the timer expires.

timer_reset¶

void timer_reset(struct timer *t);

Reset the timer with the same interval.

This function resets the timer with the same interval that was given to the timer_set() function. The start point of the interval is the exact time that the timer last expired. Therefore, this function will cause the timer to be stable over time, unlike the timer_restart() function.

Note

Must not be executed before timer expired.

Parameters¶

Name	Description
t	A pointer to the timer.

timer_restart¶

void timer_restart(struct timer *t);

Restart the timer from the current point in time

This function restarts a timer with the same interval that was given to the timer_set() function. The timer will start at the current time.

Note

A periodic timer will drift if this function is used to reset it. For preioric timers, use the timer_reset() function instead.

Parameters¶

Name	Description
t	A pointer to the timer.

timer_get_expire_time¶

clock_time_t timer_get_expire_time(struct timer *t);

Get the time for when the timer expires

Parameters¶

Name	Description
t	A pointer to the timer.

Return value¶

Expiration time

timer_expired¶

int timer_expired(struct timer *t);

Check if a timer has expired.

This function tests if a timer has expired and returns true or false depending on its status.

Parameters¶

Name	Description
t	A pointer to the timer.

Return value¶

Non-zero if the timer has expired, zero otherwise.