Contiki-NG
timer.c
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1 /*
2  * Copyright (c) 2004, Swedish Institute of Computer Science.
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  * notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  * notice, this list of conditions and the following disclaimer in the
12  * documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the Institute nor the names of its contributors
14  * may be used to endorse or promote products derived from this software
15  * without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  * This file is part of the Contiki operating system.
30  *
31  * Author: Adam Dunkels <adam@sics.se>
32  *
33  */
34 
35 /**
36  * \file
37  * Timer library implementation.
38  * \author
39  * Adam Dunkels <adam@sics.se>
40  */
41 
42 /**
43  * \addtogroup timer
44  * @{
45  */
46 
47 #include "contiki.h"
48 #include "sys/clock.h"
49 #include "sys/timer.h"
50 
51 /*---------------------------------------------------------------------------*/
52 /**
53  * Set a timer.
54  *
55  * This function is used to set a timer for a time sometime in the
56  * future. The function timer_expired() will evaluate to true after
57  * the timer has expired.
58  *
59  * \param t A pointer to the timer
60  * \param interval The interval before the timer expires.
61  *
62  */
63 void
64 timer_set(struct timer *t, clock_time_t interval)
65 {
66  t->interval = interval;
67  t->start = clock_time();
68 }
69 /*---------------------------------------------------------------------------*/
70 /**
71  * Reset the timer with the same interval.
72  *
73  * This function resets the timer with the same interval that was
74  * given to the timer_set() function. The start point of the interval
75  * is the exact time that the timer last expired. Therefore, this
76  * function will cause the timer to be stable over time, unlike the
77  * timer_restart() function.
78  *
79  * \note Must not be executed before timer expired
80  *
81  * \param t A pointer to the timer.
82  * \sa timer_restart()
83  */
84 void
85 timer_reset(struct timer *t)
86 {
87  t->start += t->interval;
88 }
89 /*---------------------------------------------------------------------------*/
90 /**
91  * Restart the timer from the current point in time
92  *
93  * This function restarts a timer with the same interval that was
94  * given to the timer_set() function. The timer will start at the
95  * current time.
96  *
97  * \note A periodic timer will drift if this function is used to reset
98  * it. For preioric timers, use the timer_reset() function instead.
99  *
100  * \param t A pointer to the timer.
101  *
102  * \sa timer_reset()
103  */
104 void
106 {
107  t->start = clock_time();
108 }
109 /*---------------------------------------------------------------------------*/
110 /**
111  * Check if a timer has expired.
112  *
113  * This function tests if a timer has expired and returns true or
114  * false depending on its status.
115  *
116  * \param t A pointer to the timer
117  *
118  * \return Non-zero if the timer has expired, zero otherwise.
119  *
120  */
121 int
123 {
124  /* Note: Can not return diff >= t->interval so we add 1 to diff and return
125  t->interval < diff - required to avoid an internal error in mspgcc. */
126  clock_time_t diff = (clock_time() - t->start) + 1;
127  return t->interval < diff;
128 
129 }
130 /*---------------------------------------------------------------------------*/
131 /**
132  * The time until the timer expires
133  *
134  * This function returns the time until the timer expires.
135  *
136  * \param t A pointer to the timer
137  *
138  * \return The time until the timer expires
139  *
140  */
141 clock_time_t
143 {
144  return t->start + t->interval - clock_time();
145 }
146 /*---------------------------------------------------------------------------*/
147 
148 /** @} */
void timer_set(struct timer *t, clock_time_t interval)
Set a timer.
Definition: timer.c:64
clock_time_t timer_remaining(struct timer *t)
The time until the timer expires.
Definition: timer.c:142
void timer_reset(struct timer *t)
Reset the timer with the same interval.
Definition: timer.c:85
A timer.
Definition: timer.h:82
Timer library header file.
void timer_restart(struct timer *t)
Restart the timer from the current point in time.
Definition: timer.c:105
int timer_expired(struct timer *t)
Check if a timer has expired.
Definition: timer.c:122
clock_time_t clock_time(void)
Get the current clock time.
Definition: clock.c:118