Callback timers¶

The ctimer API provides a timer mechanism that calls a specified C function when a ctimer expires.

Structs¶

ctimer¶

Name	Type	Description
`next`	`struct ctimer *`
`etimer`	`struct etimer`
`p`	`struct process *`
`f`	`void()(void )`
`ptr`	`void *`

Functions¶

ctimer_reset¶

void ctimer_reset(struct ctimer *c);

Reset a callback timer with the same interval as was previously set.

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

Parameters¶

Name	Description
c	A pointer to the callback timer.

ctimer_restart¶

void ctimer_restart(struct ctimer *c);

Restart a callback timer from the current point in time

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

Note

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

Parameters¶

Name	Description
c	A pointer to the callback timer.

ctimer_set¶

void ctimer_set(struct ctimer *c, clock_time_t t, void(*f)(void *), void *ptr);

Set a callback timer.

This function is used to set a callback timer for a time sometime in the future. When the callback timer expires, the callback function f will be called with ptr as argument.

Parameters¶

Name	Description
c	A pointer to the callback timer.
t	The interval before the timer expires.
f	A function to be called when the timer expires.
ptr	An opaque pointer that will be supplied as an argument to the callback function.

ctimer_stop¶

void ctimer_stop(struct ctimer *c);

Stop a pending callback timer.

This function stops a callback timer that has previously been set with ctimer_set(), ctimer_reset(), or ctimer_restart(). After this function has been called, the callback timer will be expired and will not call the callback function.

Parameters¶

Name	Description
c	A pointer to the pending callback timer.

ctimer_expired¶

int ctimer_expired(struct ctimer *c);

Check if a callback timer has expired.

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

Parameters¶

Name	Description
c	A pointer to the callback timer

Return value¶

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