The Tor Browser: nsprpub/pr/src/misc/pralarm.c@6474c204b198 (annotated)

nsprpub/pr/src/misc/pralarm.c@6474c204b198 (annotated)

nsprpub/pr/src/misc/pralarm.c

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "primpl.h"
 /**********************************************************************/
 /******************************* PRALARM ******************************/
 /**********************************************************************/
 #include "obsolete/pralarm.h"
 struct PRAlarmID {                       /* typedef'd in pralarm.h       */
     PRCList list;                        /* circular list linkage        */
     PRAlarm *alarm;                      /* back pointer to owning alarm */
     PRPeriodicAlarmFn function;          /* function to call for notify  */
     void *clientData;                    /* opaque client context        */
     PRIntervalTime period;               /* the client defined period    */
     PRUint32 rate;                       /* rate of notification         */
     PRUint32 accumulator;                /* keeps track of # notifies    */
     PRIntervalTime epoch;                /* when timer was started       */
     PRIntervalTime nextNotify;           /* when we'll next do our thing */
     PRIntervalTime lastNotify;           /* when we last did our thing   */
 };
 typedef enum {alarm_active, alarm_inactive} _AlarmState;
 struct PRAlarm {                         /* typedef'd in pralarm.h       */
     PRCList timers;                      /* base of alarm ids list       */
     PRLock *lock;                        /* lock used to protect data    */
     PRCondVar *cond;                     /* condition that used to wait  */
     PRThread *notifier;                  /* thread to deliver notifies   */
     PRAlarmID *current;                  /* current alarm being served   */
     _AlarmState state;                   /* used to delete the alarm     */
 };
 static PRAlarmID *pr_getNextAlarm(PRAlarm *alarm, PRAlarmID *id)
 {
 /*
  * Puts 'id' back into the sorted list iff it's not NULL.
  * Removes the first element from the list and returns it (or NULL).
  * List is "assumed" to be short.
  *
  * NB: Caller is providing locking
  */
     PRCList *timer;
     PRAlarmID *result = id;
     PRIntervalTime now = PR_IntervalNow();
     if (!PR_CLIST_IS_EMPTY(&alarm->timers))
     {
         if (id != NULL)  /* have to put this id back in */
         {
             PRIntervalTime idDelta = now - id->nextNotify;
             timer = alarm->timers.next;
             do
             {
                 result = (PRAlarmID*)timer;
                 if ((PRIntervalTime)(now - result->nextNotify) > idDelta)
                 {
                     PR_INSERT_BEFORE(&id->list, &alarm->timers);
                     break;
                 }
                 timer = timer->next;
             } while (timer != &alarm->timers);
         }
         result = (PRAlarmID*)(timer = PR_LIST_HEAD(&alarm->timers));
         PR_REMOVE_LINK(timer);  /* remove it from the list */
     }
     return result;
 }  /* pr_getNextAlarm */
 static PRIntervalTime pr_PredictNextNotifyTime(PRAlarmID *id)
 {
     PRIntervalTime delta;
     PRFloat64 baseRate = (PRFloat64)id->period / (PRFloat64)id->rate;
     PRFloat64 offsetFromEpoch = (PRFloat64)id->accumulator * baseRate;
     id->accumulator += 1;  /* every call advances to next period */
     id->lastNotify = id->nextNotify;  /* just keeping track of things */
     id->nextNotify = (PRIntervalTime)(offsetFromEpoch + 0.5);
     delta = id->nextNotify - id->lastNotify;
     return delta;
 }  /* pr_PredictNextNotifyTime */
 static void PR_CALLBACK pr_alarmNotifier(void *arg)
 {
     /*
      * This is the root of the notifier thread. There is one such thread
      * for each PRAlarm. It may service an arbitrary (though assumed to be
      * small) number of alarms using the same thread and structure. It
      * continues to run until the alarm is destroyed.
      */
     PRAlarmID *id = NULL;
     PRAlarm *alarm = (PRAlarm*)arg;
     enum {notify, abort, scan} why = scan;
     while (why != abort)
     {
         PRIntervalTime pause;
         PR_Lock(alarm->lock);
         while (why == scan)
         {
             alarm->current = NULL;  /* reset current id */
             if (alarm->state == alarm_inactive) why = abort;  /* we're toast */
             else if (why == scan)  /* the dominant case */
             {
                 id = pr_getNextAlarm(alarm, id);  /* even if it's the same */
                 if (id == NULL)  /* there are no alarms set */
                     (void)PR_WaitCondVar(alarm->cond, PR_INTERVAL_NO_TIMEOUT);
                 else
                 {
                     pause = id->nextNotify - (PR_IntervalNow() - id->epoch);
                     if ((PRInt32)pause <= 0)  /* is this one's time up? */
                     {
                         why = notify;  /* set up to do our thing */
                         alarm->current = id;  /* id we're about to schedule */
                     }
                     else
                         (void)PR_WaitCondVar(alarm->cond, pause);  /* dally */
                 }
             }
         }
         PR_Unlock(alarm->lock);
         if (why == notify)
         {
             (void)pr_PredictNextNotifyTime(id);
             if (!id->function(id, id->clientData, ~pause))
             {
                 /*
                  * Notified function decided not to continue. Free
                  * the alarm id to make sure it doesn't get back on
                  * the list.
                  */
                 PR_DELETE(id);  /* free notifier object */
                 id = NULL;  /* so it doesn't get back into the list */
             }
             why = scan;  /* so we can cycle through the loop again */
         }
     }
 }  /* pr_alarm_notifier */
 PR_IMPLEMENT(PRAlarm*) PR_CreateAlarm(void)
 {
     PRAlarm *alarm = PR_NEWZAP(PRAlarm);
     if (alarm != NULL)
     {
         if ((alarm->lock = PR_NewLock()) == NULL) goto done;
         if ((alarm->cond = PR_NewCondVar(alarm->lock)) == NULL) goto done;
         alarm->state = alarm_active;
         PR_INIT_CLIST(&alarm->timers);
         alarm->notifier = PR_CreateThread(
             PR_USER_THREAD, pr_alarmNotifier, alarm,
             PR_GetThreadPriority(PR_GetCurrentThread()),
             PR_LOCAL_THREAD, PR_JOINABLE_THREAD, 0);
         if (alarm->notifier == NULL) goto done;
     }
     return alarm;
 done:
     if (alarm->cond != NULL) PR_DestroyCondVar(alarm->cond);
     if (alarm->lock != NULL) PR_DestroyLock(alarm->lock);
     PR_DELETE(alarm);
     return NULL;
 }  /* CreateAlarm */
 PR_IMPLEMENT(PRStatus) PR_DestroyAlarm(PRAlarm *alarm)
 {
     PRStatus rv;
     PR_Lock(alarm->lock);
     alarm->state = alarm_inactive;
     rv = PR_NotifyCondVar(alarm->cond);
     PR_Unlock(alarm->lock);
     if (rv == PR_SUCCESS)
         rv = PR_JoinThread(alarm->notifier);
     if (rv == PR_SUCCESS)
     {
         PR_DestroyCondVar(alarm->cond);
         PR_DestroyLock(alarm->lock);
         PR_DELETE(alarm);
     }
     return rv;
 }  /* PR_DestroyAlarm */
 PR_IMPLEMENT(PRAlarmID*) PR_SetAlarm(
     PRAlarm *alarm, PRIntervalTime period, PRUint32 rate,
     PRPeriodicAlarmFn function, void *clientData)
 {
     /*
      * Create a new periodic alarm an existing current structure.
      * Set up the context and compute the first notify time (immediate).
      * Link the new ID into the head of the list (since it's notifying
      * immediately).
      */
     PRAlarmID *id = PR_NEWZAP(PRAlarmID);
     if (!id)
         return NULL;
     id->alarm = alarm;
     PR_INIT_CLIST(&id->list);
     id->function = function;
     id->clientData = clientData;
     id->period = period;
     id->rate = rate;
     id->epoch = id->nextNotify = PR_IntervalNow();
     (void)pr_PredictNextNotifyTime(id);
     PR_Lock(alarm->lock);
     PR_INSERT_BEFORE(&id->list, &alarm->timers);
     PR_NotifyCondVar(alarm->cond);
     PR_Unlock(alarm->lock);
     return id;
 }  /* PR_SetAlarm */
 PR_IMPLEMENT(PRStatus) PR_ResetAlarm(
     PRAlarmID *id, PRIntervalTime period, PRUint32 rate)
 {
     /*
      * Can only be called from within the notify routine. Doesn't
      * need locking because it can only be called from within the
      * notify routine.
      */
     if (id != id->alarm->current)
         return PR_FAILURE;
     id->period = period;
     id->rate = rate;
     id->accumulator = 1;
     id->epoch = PR_IntervalNow();
     (void)pr_PredictNextNotifyTime(id);
     return PR_SUCCESS;
 }  /* PR_ResetAlarm */

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nsprpub/pr/src/misc/pralarm.c@6474c204b198 (annotated)

nsprpub/pr/src/misc/pralarm.c