Contiki-NG
stimer.c
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1/*
2 * Copyright (c) 2004, 2008, 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>, Nicolas Tsiftes <nvt@sics.se>
32 *
33 */
34
35/**
36 * \file
37 * Timer of seconds library implementation.
38 * \author
39 * Adam Dunkels <adam@sics.se>, Nicolas Tsiftes <nvt@sics.se>
40 */
41
42/**
43 * \addtogroup stimer
44 * @{
45 */
46
47#include "contiki.h"
48#include "sys/clock.h"
49#include "sys/stimer.h"
50
51#define SCLOCK_GEQ(a, b) ((unsigned long)((a) - (b)) < \
52 ((unsigned long)(~((unsigned long)0)) >> 1))
53
54/*---------------------------------------------------------------------------*/
55/**
56 * Set a timer.
57 *
58 * This function is used to set a timer for a time sometime in the
59 * future. The function stimer_expired() will evaluate to true after
60 * the timer has expired.
61 *
62 * \param t A pointer to the timer
63 * \param interval The interval before the timer expires.
64 *
65 */
66void
67stimer_set(struct stimer *t, unsigned long interval)
68{
69 t->interval = interval;
70 t->start = clock_seconds();
71}
72/*---------------------------------------------------------------------------*/
73/**
74 * Reset the timer with the same interval.
75 *
76 * This function resets the timer with the same interval that was
77 * given to the stimer_set() function. The start point of the interval
78 * is the exact time that the timer last expired. Therefore, this
79 * function will cause the timer to be stable over time, unlike the
80 * stimer_restart() function. If this is executed before the
81 * timer expired, this function has no effect.
82 *
83 * \param t A pointer to the timer.
84 *
85 * \sa stimer_restart()
86 */
87void
89{
90 if(stimer_expired(t)) {
91 t->start += t->interval;
92 }
93}
94/*---------------------------------------------------------------------------*/
95/**
96 * Restart the timer from the current point in time
97 *
98 * This function restarts a timer with the same interval that was
99 * given to the stimer_set() function. The timer will start at the
100 * current time.
101 *
102 * \note A periodic timer will drift if this function is used to reset
103 * it. For preioric timers, use the stimer_reset() function instead.
104 *
105 * \param t A pointer to the timer.
106 *
107 * \sa stimer_reset()
108 */
109void
111{
112 t->start = clock_seconds();
113}
114/*---------------------------------------------------------------------------*/
115/**
116 * Check if a timer has expired.
117 *
118 * This function tests if a timer has expired and returns true or
119 * false depending on its status.
120 *
121 * \param t A pointer to the timer
122 *
123 * \return Non-zero if the timer has expired, zero otherwise.
124 *
125 */
126int
128{
129 return SCLOCK_GEQ(clock_seconds(), t->start + t->interval);
130}
131/*---------------------------------------------------------------------------*/
132/**
133 * The time until the timer expires
134 *
135 * This function returns the time until the timer expires.
136 *
137 * \param t A pointer to the timer
138 *
139 * \return The time until the timer expires
140 *
141 */
142unsigned long
144{
145 return t->start + t->interval - clock_seconds();
146}
147/*---------------------------------------------------------------------------*/
148/**
149 * The time elapsed since the timer started
150 *
151 * This function returns the time elapsed.
152 *
153 * \param t A pointer to the timer
154 *
155 * \return The time elapsed since the last start of the timer
156 *
157 */
158unsigned long
160{
161 return clock_seconds() - t->start;
162}
163
164/*---------------------------------------------------------------------------*/
165
166/** @} */
unsigned long clock_seconds(void)
Get the current value of the platform seconds.
Definition: clock.c:130
void stimer_reset(struct stimer *t)
Reset the timer with the same interval.
Definition: stimer.c:88
void stimer_restart(struct stimer *t)
Restart the timer from the current point in time.
Definition: stimer.c:110
unsigned long stimer_remaining(struct stimer *t)
The time until the timer expires.
Definition: stimer.c:143
unsigned long stimer_elapsed(struct stimer *t)
The time elapsed since the timer started.
Definition: stimer.c:159
int stimer_expired(struct stimer *t)
Check if a timer has expired.
Definition: stimer.c:127
void stimer_set(struct stimer *t, unsigned long interval)
Set a timer.
Definition: stimer.c:67
Second timer library header file.
A timer.
Definition: stimer.h:81