pralarm.h (6937B)
1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* This Source Code Form is subject to the terms of the Mozilla Public 3 * License, v. 2.0. If a copy of the MPL was not distributed with this 4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 5 6 /* 7 ** File: pralarm.h 8 ** Description: API to periodic alarms. 9 ** 10 ** 11 ** Alarms are defined to invoke some client specified function at 12 ** a time in the future. The notification may be a one time event 13 ** or repeated at a fixed interval. The interval at which the next 14 ** notification takes place may be modified by the client code only 15 ** during the respective notification. 16 ** 17 ** The notification is delivered on a thread that is part of the 18 ** alarm context (PRAlarm). The thread will inherit the priority 19 ** of the Alarm creator. 20 ** 21 ** Any number of periodic alarms (PRAlarmID) may be created within 22 ** the context of a single alarm (PRAlarm). The notifications will be 23 ** scheduled as close to the desired time as possible. 24 ** 25 ** Repeating periodic notifies are expected to run at a fixed rate. 26 ** That rate is expressed as some number of notifies per period where 27 ** the period is much larger than a PRIntervalTime (see prinrval.h). 28 */ 29 30 #if !defined(pralarm_h) 31 #define pralarm_h 32 33 #include "prtypes.h" 34 #include "prinrval.h" 35 36 37 PR_BEGIN_EXTERN_C 38 39 /**********************************************************************/ 40 /************************* TYPES AND CONSTANTS ************************/ 41 /**********************************************************************/ 42 43 typedef struct PRAlarm PRAlarm; 44 typedef struct PRAlarmID PRAlarmID; 45 46 typedef PRBool (PR_CALLBACK *PRPeriodicAlarmFn)( 47 PRAlarmID *id, void *clientData, PRUint32 late); 48 49 /**********************************************************************/ 50 /****************************** FUNCTIONS *****************************/ 51 /**********************************************************************/ 52 53 /*********************************************************************** 54 ** FUNCTION: PR_CreateAlarm 55 ** DESCRIPTION: 56 ** Create an alarm context. 57 ** INPUTS: void 58 ** OUTPUTS: None 59 ** RETURN: PRAlarm* 60 ** 61 ** SIDE EFFECTS: 62 ** This creates an alarm context, which is an object used for subsequent 63 ** notification creations. It also creates a thread that will be used to 64 ** deliver the notifications that are expected to be defined. The client 65 ** is resposible for destroying the context when appropriate. 66 ** RESTRICTIONS: 67 ** None. 68 ** MEMORY: The object (PRAlarm) and a thread to support notifications. 69 ** ALGORITHM: N/A 70 ***********************************************************************/ 71 NSPR_API(PRAlarm*) PR_CreateAlarm(void); 72 73 /*********************************************************************** 74 ** FUNCTION: PR_DestroyAlarm 75 ** DESCRIPTION: 76 ** Destroys the context created by PR_CreateAlarm(). 77 ** INPUTS: PRAlarm* 78 ** OUTPUTS: None 79 ** RETURN: PRStatus 80 ** 81 ** SIDE EFFECTS: 82 ** This destroys the context that was created by PR_CreateAlarm(). 83 ** If there are any active alarms (PRAlarmID), they will be cancelled. 84 ** Once that is done, the thread that was used to deliver the alarms 85 ** will be joined. 86 ** RESTRICTIONS: 87 ** None. 88 ** MEMORY: N/A 89 ** ALGORITHM: N/A 90 ***********************************************************************/ 91 NSPR_API(PRStatus) PR_DestroyAlarm(PRAlarm *alarm); 92 93 /*********************************************************************** 94 ** FUNCTION: PR_SetAlarm 95 ** DESCRIPTION: 96 ** Creates a periodic notifier that is to be delivered to a specified 97 ** function at some fixed interval. 98 ** INPUTS: PRAlarm *alarm Parent alarm context 99 ** PRIntervalTime period Interval over which the notifies 100 ** are delivered. 101 ** PRUint32 rate The rate within the interval that 102 ** the notifies will be delivered. 103 ** PRPeriodicAlarmFn function Entry point where the notifies 104 ** will be delivered. 105 ** OUTPUTS: None 106 ** RETURN: PRAlarmID* Handle to the notifier just created 107 ** or NULL if the request failed. 108 ** 109 ** SIDE EFFECTS: 110 ** A periodic notifier is created. The notifications will be delivered 111 ** by the alarm's internal thread at a fixed interval whose rate is the 112 ** number of interrupts per interval specified. The first notification 113 ** will be delivered as soon as possible, and they will continue until 114 ** the notifier routine indicates that they should cease of the alarm 115 ** context is destroyed (PR_DestroyAlarm). 116 ** RESTRICTIONS: 117 ** None. 118 ** MEMORY: Memory for the notifier object. 119 ** ALGORITHM: The rate at which notifications are delivered are stated 120 ** to be "'rate' notifies per 'interval'". The exact time of 121 ** the notification is computed based on a epoch established 122 ** when the notifier was set. Each notification is delivered 123 ** not ealier than the epoch plus the fixed rate times the 124 ** notification sequence number. Such notifications have the 125 ** potential to be late by not more than 'interval'/'rate'. 126 ** The amount of lateness of one notification is taken into 127 ** account on the next in an attempt to avoid long term slew. 128 ***********************************************************************/ 129 NSPR_API(PRAlarmID*) PR_SetAlarm( 130 PRAlarm *alarm, PRIntervalTime period, PRUint32 rate, 131 PRPeriodicAlarmFn function, void *clientData); 132 133 /*********************************************************************** 134 ** FUNCTION: PR_ResetAlarm 135 ** DESCRIPTION: 136 ** Resets an existing alarm. 137 ** INPUTS: PRAlarmID *id Identify of the notifier. 138 ** PRIntervalTime period Interval over which the notifies 139 ** are delivered. 140 ** PRUint32 rate The rate within the interval that 141 ** the notifies will be delivered. 142 ** OUTPUTS: None 143 ** RETURN: PRStatus Indication of completion. 144 ** 145 ** SIDE EFFECTS: 146 ** An existing alarm may have its period and rate redefined. The 147 ** additional side effect is that the notifier's epoch is recomputed. 148 ** The first notification delivered by the newly refreshed alarm is 149 ** defined to be 'interval'/'rate' from the time of the reset. 150 ** RESTRICTIONS: 151 ** This function may only be called in the notifier for that alarm. 152 ** MEMORY: N/A. 153 ** ALGORITHM: See PR_SetAlarm(). 154 ***********************************************************************/ 155 NSPR_API(PRStatus) PR_ResetAlarm( 156 PRAlarmID *id, PRIntervalTime period, PRUint32 rate); 157 158 PR_END_EXTERN_C 159 160 #endif /* !defined(pralarm_h) */ 161 162 /* prinrval.h */