include/timers.h

   1 /* This library provides generic watchdog timer management functionality.
   2  * The functions operate on a timer queue provided by the caller. Note that
   3  * the timers must use absolute time to allow sorting. The library provides:
   4  *
   5  *    tmrs_settimer:     (re)set a new watchdog timer in the timers queue
   6  *    tmrs_clrtimer:     remove a timer from both the timers queue
   7  *    tmrs_exptimers:    check for expired timers and run watchdog functions
   8  *
   9  * Author:
  10  *    Jorrit N. Herder <jnherder@cs.vu.nl>
  11  *    Adapted from tmr_settimer and tmr_clrtimer in src/kernel/clock.c.
  12  *    Last modified: September 30, 2004.
  13  */
  14
  15 #ifndef _TIMERS_H
  16 #define _TIMERS_H
  17
  18 #include <limits.h>
  19 #include <sys/types.h>
  20
  21 struct timer;
  22 typedef void (*tmr_func_t)(struct timer *tp);
  23 typedef union { int ta_int; long ta_long; void *ta_ptr; } tmr_arg_t;
  24
  25 /* A timer_t variable must be declare for each distinct timer to be used.
  26  * The timers watchdog function and expiration time are automatically set
  27  * by the library function tmrs_settimer, but its argument is not.
  28  */
  29 typedef struct timer
  30 {
  31   struct timer  *tmr_next;      /* next in a timer chain */
  32   clock_t       tmr_exp_time;   /* expiration time */
  33   tmr_func_t    tmr_func;       /* function to call when expired */
  34   tmr_arg_t     tmr_arg;        /* random argument */
  35 } timer_t;
  36
  37 /* Used when the timer is not active. */
  38 #define TMR_NEVER    ((clock_t) -1 < 0) ? ((clock_t) LONG_MAX) : ((clock_t) -1)
  39 #undef TMR_NEVER
  40 #define TMR_NEVER       ((clock_t) LONG_MAX)
  41
  42 /* These definitions can be used to set or get data from a timer variable. */
  43 #define tmr_arg(tp) (&(tp)->tmr_arg)
  44 #define tmr_exp_time(tp) (&(tp)->tmr_exp_time)
  45
  46 /* Timers should be initialized once before they are being used. Be careful
  47  * not to reinitialize a timer that is in a list of timers, or the chain
  48  * will be broken.
  49  */
  50 #define tmr_inittimer(tp) (void)((tp)->tmr_exp_time = TMR_NEVER, \
  51         (tp)->tmr_next = NULL)
  52
  53 /* The following generic timer management functions are available. They
  54  * can be used to operate on the lists of timers. Adding a timer to a list
  55  * automatically takes care of removing it.
  56  */
  57 _PROTOTYPE( clock_t tmrs_clrtimer, (timer_t **tmrs, timer_t *tp, clock_t *new_head)             );
  58 _PROTOTYPE( void tmrs_exptimers, (timer_t **tmrs, clock_t now, clock_t *new_head)               );
  59 _PROTOTYPE( clock_t tmrs_settimer, (timer_t **tmrs, timer_t *tp,
  60         clock_t exp_time, tmr_func_t watchdog, clock_t *new_head)                               );
  61
  62 #endif /* _TIMERS_H */
  63