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