michael@0: /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: /*
michael@0: ** File:		pralarm.h
michael@0: ** Description:	API to periodic alarms.
michael@0: **
michael@0: **
michael@0: ** Alarms are defined to invoke some client specified function at 
michael@0: ** a time in the future. The notification may be a one time event
michael@0: ** or repeated at a fixed interval. The interval at which the next
michael@0: ** notification takes place may be modified by the client code only
michael@0: ** during the respective notification.
michael@0: **
michael@0: ** The notification is delivered on a thread that is part of the
michael@0: ** alarm context (PRAlarm). The thread will inherit the priority
michael@0: ** of the Alarm creator.
michael@0: **
michael@0: ** Any number of periodic alarms (PRAlarmID) may be created within
michael@0: ** the context of a single alarm (PRAlarm). The notifications will be
michael@0: ** scheduled as close to the desired time as possible.
michael@0: **
michael@0: ** Repeating periodic notifies are expected to run at a fixed rate.
michael@0: ** That rate is expressed as some number of notifies per period where
michael@0: ** the period is much larger than a PRIntervalTime (see prinrval.h).
michael@0: */
michael@0: 
michael@0: #if !defined(pralarm_h)
michael@0: #define pralarm_h
michael@0: 
michael@0: #include "prtypes.h"
michael@0: #include "prinrval.h"
michael@0: 
michael@0: 
michael@0: PR_BEGIN_EXTERN_C
michael@0: 
michael@0: /**********************************************************************/
michael@0: /************************* TYPES AND CONSTANTS ************************/
michael@0: /**********************************************************************/
michael@0: 
michael@0: typedef struct PRAlarm PRAlarm;
michael@0: typedef struct PRAlarmID PRAlarmID;
michael@0: 
michael@0: typedef PRBool (PR_CALLBACK *PRPeriodicAlarmFn)(
michael@0:     PRAlarmID *id, void *clientData, PRUint32 late);
michael@0: 
michael@0: /**********************************************************************/
michael@0: /****************************** FUNCTIONS *****************************/
michael@0: /**********************************************************************/
michael@0: 
michael@0: /***********************************************************************
michael@0: ** FUNCTION:    PR_CreateAlarm
michael@0: ** DESCRIPTION:
michael@0: **  Create an alarm context.
michael@0: ** INPUTS:      void
michael@0: ** OUTPUTS:     None
michael@0: ** RETURN:      PRAlarm*
michael@0: **  
michael@0: ** SIDE EFFECTS:
michael@0: **  This creates an alarm context, which is an object used for subsequent
michael@0: **  notification creations. It also creates a thread that will be used to
michael@0: ** deliver the notifications that are expected to be defined. The client
michael@0: ** is resposible for destroying the context when appropriate.
michael@0: ** RESTRICTIONS:
michael@0: **  None. 
michael@0: ** MEMORY:      The object (PRAlarm) and a thread to support notifications.
michael@0: ** ALGORITHM:   N/A
michael@0: ***********************************************************************/
michael@0: NSPR_API(PRAlarm*) PR_CreateAlarm(void);
michael@0: 
michael@0: /***********************************************************************
michael@0: ** FUNCTION:    PR_DestroyAlarm
michael@0: ** DESCRIPTION:
michael@0: **  Destroys the context created by PR_CreateAlarm().
michael@0: ** INPUTS:      PRAlarm*
michael@0: ** OUTPUTS:     None
michael@0: ** RETURN:      PRStatus
michael@0: **  
michael@0: ** SIDE EFFECTS:
michael@0: **  This destroys the context that was created by PR_CreateAlarm().
michael@0: **  If there are any active alarms (PRAlarmID), they will be cancelled.
michael@0: **  Once that is done, the thread that was used to deliver the alarms
michael@0: **  will be joined. 
michael@0: ** RESTRICTIONS:
michael@0: **  None. 
michael@0: ** MEMORY:      N/A
michael@0: ** ALGORITHM:   N/A
michael@0: ***********************************************************************/
michael@0: NSPR_API(PRStatus) PR_DestroyAlarm(PRAlarm *alarm);
michael@0: 
michael@0: /***********************************************************************
michael@0: ** FUNCTION:    PR_SetAlarm
michael@0: ** DESCRIPTION:
michael@0: **  Creates a periodic notifier that is to be delivered to a specified
michael@0: **  function at some fixed interval.
michael@0: ** INPUTS:      PRAlarm *alarm              Parent alarm context
michael@0: **              PRIntervalTime period       Interval over which the notifies
michael@0: **                                          are delivered.
michael@0: **              PRUint32 rate               The rate within the interval that
michael@0: **                                          the notifies will be delivered.
michael@0: **              PRPeriodicAlarmFn function  Entry point where the notifies
michael@0: **                                          will be delivered.
michael@0: ** OUTPUTS:     None
michael@0: ** RETURN:      PRAlarmID*                  Handle to the notifier just created
michael@0: **                                          or NULL if the request failed.
michael@0: **  
michael@0: ** SIDE EFFECTS:
michael@0: **  A periodic notifier is created. The notifications will be delivered
michael@0: **  by the alarm's internal thread at a fixed interval whose rate is the
michael@0: **  number of interrupts per interval specified. The first notification
michael@0: **  will be delivered as soon as possible, and they will continue until
michael@0: **  the notifier routine indicates that they should cease of the alarm
michael@0: **  context is destroyed (PR_DestroyAlarm).
michael@0: ** RESTRICTIONS:
michael@0: **  None. 
michael@0: ** MEMORY:      Memory for the notifier object.
michael@0: ** ALGORITHM:   The rate at which notifications are delivered are stated
michael@0: **              to be "'rate' notifies per 'interval'". The exact time of
michael@0: **              the notification is computed based on a epoch established
michael@0: **              when the notifier was set. Each notification is delivered
michael@0: **              not ealier than the epoch plus the fixed rate times the
michael@0: **              notification sequence number. Such notifications have the
michael@0: **              potential to be late by not more than 'interval'/'rate'.
michael@0: **              The amount of lateness of one notification is taken into
michael@0: **              account on the next in an attempt to avoid long term slew.  
michael@0: ***********************************************************************/
michael@0: NSPR_API(PRAlarmID*) PR_SetAlarm(
michael@0:     PRAlarm *alarm, PRIntervalTime period, PRUint32 rate,
michael@0:     PRPeriodicAlarmFn function, void *clientData);
michael@0: 
michael@0: /***********************************************************************
michael@0: ** FUNCTION:    PR_ResetAlarm
michael@0: ** DESCRIPTION:
michael@0: **  Resets an existing alarm.
michael@0: ** INPUTS:      PRAlarmID *id               Identify of the notifier.
michael@0: **              PRIntervalTime period       Interval over which the notifies
michael@0: **                                          are delivered.
michael@0: **              PRUint32 rate               The rate within the interval that
michael@0: **                                          the notifies will be delivered.
michael@0: ** OUTPUTS:     None
michael@0: ** RETURN:      PRStatus                    Indication of completion.
michael@0: **  
michael@0: ** SIDE EFFECTS:
michael@0: **  An existing alarm may have its period and rate redefined. The
michael@0: **  additional side effect is that the notifier's epoch is recomputed.
michael@0: **  The first notification delivered by the newly refreshed alarm is
michael@0: **  defined to be 'interval'/'rate' from the time of the reset.
michael@0: ** RESTRICTIONS:
michael@0: **  This function may only be called in the notifier for that alarm.
michael@0: ** MEMORY:      N/A.
michael@0: ** ALGORITHM:   See PR_SetAlarm().  
michael@0: ***********************************************************************/
michael@0: NSPR_API(PRStatus) PR_ResetAlarm(
michael@0: 	PRAlarmID *id, PRIntervalTime period, PRUint32 rate);
michael@0: 
michael@0: PR_END_EXTERN_C
michael@0: 
michael@0: #endif /* !defined(pralarm_h) */
michael@0: 
michael@0: /* prinrval.h */