nsprpub/pr/src/misc/pralarm.c

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  15  * The Original Code is the Netscape Portable Runtime (NSPR).
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  37
  38 #include "primpl.h"
  39
  40 /**********************************************************************/
  41 /******************************* PRALARM ******************************/
  42 /**********************************************************************/
  43
  44 #ifdef XP_MAC
  45 #include "pralarm.h"
  46 #else
  47 #include "obsolete/pralarm.h"
  48 #endif
  49
  50 struct PRAlarmID {                       /* typedef'd in pralarm.h       */
  51     PRCList list;                        /* circular list linkage        */
  52     PRAlarm *alarm;                      /* back pointer to owning alarm */
  53     PRPeriodicAlarmFn function;          /* function to call for notify  */
  54     void *clientData;                    /* opaque client context        */
  55     PRIntervalTime period;               /* the client defined period    */
  56     PRUint32 rate;                       /* rate of notification         */
  57
  58     PRUint32 accumulator;                /* keeps track of # notifies    */
  59     PRIntervalTime epoch;                /* when timer was started       */
  60     PRIntervalTime nextNotify;           /* when we'll next do our thing */
  61     PRIntervalTime lastNotify;           /* when we last did our thing   */
  62 };
  63
  64 typedef enum {alarm_active, alarm_inactive} _AlarmState;
  65
  66 struct PRAlarm {                         /* typedef'd in pralarm.h       */
  67     PRCList timers;                      /* base of alarm ids list       */
  68     PRLock *lock;                        /* lock used to protect data    */
  69     PRCondVar *cond;                     /* condition that used to wait  */
  70     PRThread *notifier;                  /* thread to deliver notifies   */
  71     PRAlarmID *current;                  /* current alarm being served   */
  72     _AlarmState state;                   /* used to delete the alarm     */
  73 };
  74
  75 static PRAlarmID *pr_getNextAlarm(PRAlarm *alarm, PRAlarmID *id)
  76 {
  77 /*
  78  * Puts 'id' back into the sorted list iff it's not NULL.
  79  * Removes the first element from the list and returns it (or NULL).
  80  * List is "assumed" to be short.
  81  *
  82  * NB: Caller is providing locking
  83  */
  84     PRCList *timer;
  85     PRAlarmID *result = id;
  86     PRIntervalTime now = PR_IntervalNow();
  87
  88     if (!PR_CLIST_IS_EMPTY(&alarm->timers))
  89     {
  90         if (id != NULL)  /* have to put this id back in */
  91         {
  92             PRIntervalTime idDelta = now - id->nextNotify;
  93             timer = alarm->timers.next;
  94             do
  95             {
  96                 result = (PRAlarmID*)timer;
  97                 if ((PRIntervalTime)(now - result->nextNotify) > idDelta)
  98                 {
  99                     PR_INSERT_BEFORE(&id->list, &alarm->timers);
 100                     break;
 101                 }
 102                 timer = timer->next;
 103             } while (timer != &alarm->timers);
 104         }
 105         result = (PRAlarmID*)(timer = PR_LIST_HEAD(&alarm->timers));
 106         PR_REMOVE_LINK(timer);  /* remove it from the list */
 107     }
 108
 109     return result;
 110 }  /* pr_getNextAlarm */
 111
 112 static PRIntervalTime pr_PredictNextNotifyTime(PRAlarmID *id)
 113 {
 114     PRIntervalTime delta;
 115     PRFloat64 baseRate = (PRFloat64)id->period / (PRFloat64)id->rate;
 116     PRFloat64 offsetFromEpoch = (PRFloat64)id->accumulator * baseRate;
 117
 118     id->accumulator += 1;  /* every call advances to next period */
 119     id->lastNotify = id->nextNotify;  /* just keeping track of things */
 120     id->nextNotify = (PRIntervalTime)(offsetFromEpoch + 0.5);
 121
 122     delta = id->nextNotify - id->lastNotify;
 123     return delta;
 124 }  /* pr_PredictNextNotifyTime */
 125
 126 static void PR_CALLBACK pr_alarmNotifier(void *arg)
 127 {
 128     /*
 129      * This is the root of the notifier thread. There is one such thread
 130      * for each PRAlarm. It may service an arbitrary (though assumed to be
 131      * small) number of alarms using the same thread and structure. It
 132      * continues to run until the alarm is destroyed.
 133      */
 134     PRAlarmID *id = NULL;
 135     PRAlarm *alarm = (PRAlarm*)arg;
 136     enum {notify, abort, scan} why = scan;
 137
 138     while (why != abort)
 139     {
 140         PRIntervalTime pause;
 141
 142         PR_Lock(alarm->lock);
 143         while (why == scan)
 144         {
 145             alarm->current = NULL;  /* reset current id */
 146             if (alarm->state == alarm_inactive) why = abort;  /* we're toast */
 147             else if (why == scan)  /* the dominant case */
 148             {
 149                 id = pr_getNextAlarm(alarm, id);  /* even if it's the same */
 150                 if (id == NULL)  /* there are no alarms set */
 151                     (void)PR_WaitCondVar(alarm->cond, PR_INTERVAL_NO_TIMEOUT);
 152                 else
 153                 {
 154                     pause = id->nextNotify - (PR_IntervalNow() - id->epoch);
 155                     if ((PRInt32)pause <= 0)  /* is this one's time up? */
 156                     {
 157                         why = notify;  /* set up to do our thing */
 158                         alarm->current = id;  /* id we're about to schedule */
 159                     }
 160                     else
 161                         (void)PR_WaitCondVar(alarm->cond, pause);  /* dally */
 162                 }
 163             }
 164         }
 165         PR_Unlock(alarm->lock);
 166
 167         if (why == notify)
 168         {
 169             (void)pr_PredictNextNotifyTime(id);
 170             if (!id->function(id, id->clientData, ~pause))
 171             {
 172                 /*
 173                  * Notified function decided not to continue. Free
 174                  * the alarm id to make sure it doesn't get back on
 175                  * the list.
 176                  */
 177                 PR_DELETE(id);  /* free notifier object */
 178                 id = NULL;  /* so it doesn't get back into the list */
 179             }
 180             why = scan;  /* so we can cycle through the loop again */
 181         }
 182     }
 183
 184 }  /* pr_alarm_notifier */
 185
 186 PR_IMPLEMENT(PRAlarm*) PR_CreateAlarm(void)
 187 {
 188     PRAlarm *alarm = PR_NEWZAP(PRAlarm);
 189     if (alarm != NULL)
 190     {
 191         if ((alarm->lock = PR_NewLock()) == NULL) goto done;
 192         if ((alarm->cond = PR_NewCondVar(alarm->lock)) == NULL) goto done;
 193         alarm->state = alarm_active;
 194         PR_INIT_CLIST(&alarm->timers);
 195         alarm->notifier = PR_CreateThread(
 196             PR_USER_THREAD, pr_alarmNotifier, alarm,
 197             PR_GetThreadPriority(PR_GetCurrentThread()),
 198             PR_LOCAL_THREAD, PR_JOINABLE_THREAD, 0);
 199         if (alarm->notifier == NULL) goto done;
 200     }
 201     return alarm;
 202
 203 done:
 204     if (alarm->cond != NULL) PR_DestroyCondVar(alarm->cond);
 205     if (alarm->lock != NULL) PR_DestroyLock(alarm->lock);
 206     PR_DELETE(alarm);
 207     return NULL;
 208 }  /* CreateAlarm */
 209
 210 PR_IMPLEMENT(PRStatus) PR_DestroyAlarm(PRAlarm *alarm)
 211 {
 212     PRStatus rv;
 213
 214     PR_Lock(alarm->lock);
 215     alarm->state = alarm_inactive;
 216     rv = PR_NotifyCondVar(alarm->cond);
 217     PR_Unlock(alarm->lock);
 218
 219     if (rv == PR_SUCCESS)
 220         rv = PR_JoinThread(alarm->notifier);
 221     if (rv == PR_SUCCESS)
 222     {
 223         PR_DestroyCondVar(alarm->cond);
 224         PR_DestroyLock(alarm->lock);
 225         PR_DELETE(alarm);
 226     }
 227     return rv;
 228 }  /* PR_DestroyAlarm */
 229
 230 PR_IMPLEMENT(PRAlarmID*) PR_SetAlarm(
 231     PRAlarm *alarm, PRIntervalTime period, PRUint32 rate,
 232     PRPeriodicAlarmFn function, void *clientData)
 233 {
 234     /*
 235      * Create a new periodic alarm an existing current structure.
 236      * Set up the context and compute the first notify time (immediate).
 237      * Link the new ID into the head of the list (since it's notifying
 238      * immediately).
 239      */
 240
 241     PRAlarmID *id = PR_NEWZAP(PRAlarmID);
 242
 243     if (!id)
 244         return NULL;
 245
 246     id->alarm = alarm;
 247     PR_INIT_CLIST(&id->list);
 248     id->function = function;
 249     id->clientData = clientData;
 250     id->period = period;
 251     id->rate = rate;
 252     id->epoch = id->nextNotify = PR_IntervalNow();
 253     (void)pr_PredictNextNotifyTime(id);
 254
 255     PR_Lock(alarm->lock);
 256     PR_INSERT_BEFORE(&id->list, &alarm->timers);
 257     PR_NotifyCondVar(alarm->cond);
 258     PR_Unlock(alarm->lock);
 259
 260     return id;
 261 }  /* PR_SetAlarm */
 262
 263 PR_IMPLEMENT(PRStatus) PR_ResetAlarm(
 264     PRAlarmID *id, PRIntervalTime period, PRUint32 rate)
 265 {
 266     /*
 267      * Can only be called from within the notify routine. Doesn't
 268      * need locking because it can only be called from within the
 269      * notify routine.
 270      */
 271     if (id != id->alarm->current)
 272         return PR_FAILURE;
 273     id->period = period;
 274     id->rate = rate;
 275     id->accumulator = 1;
 276     id->epoch = PR_IntervalNow();
 277     (void)pr_PredictNextNotifyTime(id);
 278     return PR_SUCCESS;
 279 }  /* PR_ResetAlarm */
 280
 281
 282