20070918/src/timer.c

/*
 *  Copyright (C) 2006-2007  Anders Gavare.  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright  
 *     notice, this list of conditions and the following disclaimer in the 
 *     documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 *  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE   
 *  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 *  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 *  OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 *  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 *  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 *  OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 *  SUCH DAMAGE.
 *
 *
 *  $Id: timer.c,v 1.11 2007/06/18 04:23:19 debug Exp $
 *
 *  Timer framework. This is used by emulated clocks.
 */

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <sys/time.h>

#include "misc.h"
#include "timer.h"


/*  #define TEST  */


struct timer {
        struct timer    *next;

        double          freq;
        void            (*timer_tick)(struct timer *timer, void *extra);
        void            *extra;

        double          interval;
        double          next_tick_at;
};

static struct timer *first_timer = NULL;
struct timeval timer_start_tv;
static double timer_freq;
static int timer_countdown_to_next_gettimeofday;
static double timer_current_time;
static double timer_current_time_step;

static int timer_is_running;

#define SECONDS_BETWEEN_GETTIMEOFDAY_SYNCH      1.65


/*
 *  timer_add():
 *
 *  Adds a virtual timer to the list of timers.
 *
 *  Return value is a pointer to a timer struct.
 */
struct timer *timer_add(double freq, void (*timer_tick)(struct timer *timer,
        void *extra), void *extra)
{
        struct timer *newtimer;

        CHECK_ALLOCATION(newtimer = malloc(sizeof(struct timer)));

        if (freq <= 0.00000001)
                freq = 0.00000001;

        newtimer->freq = freq;
        newtimer->timer_tick = timer_tick;
        newtimer->extra = extra;

        newtimer->interval = 1.0 / freq;
        newtimer->next_tick_at = timer_current_time + newtimer->interval;

        newtimer->next = first_timer;
        first_timer = newtimer;

        return newtimer;
}


/*
 *  timer_remove():
 *
 *  Removes a virtual timer from the list of timers.
 */
void timer_remove(struct timer *t)
{
        struct timer *prev = NULL, *cur = first_timer;

        while (cur != NULL && cur != t) {
                prev = cur;
                cur = cur->next;
        }

        if (cur == t) {
                if (prev == NULL)
                        first_timer = cur->next;
                else
                        prev->next = cur->next;
                free(cur);
        } else {
                fprintf(stderr, "attempt to remove timer %p which "
                    "doesn't exist. aborting\n", t);
                exit(1);
        }
}


/*
 *  timer_update_frequency():
 *
 *  Changes the frequency of an existing timer.
 */
void timer_update_frequency(struct timer *t, double new_freq)
{
        if (t->freq == new_freq)
                return;

        t->freq = new_freq;

        if (new_freq <= 0.00000001)
                new_freq = 0.00000001;

        t->interval = 1.0 / new_freq;
        t->next_tick_at = timer_current_time + t->interval;
}


/*
 *  timer_tick():
 *
 *  Timer tick handler. This is where the interesting stuff happens.
 */
static void timer_tick(int signal_nr)
{
        struct timer *timer = first_timer;
        struct timeval tv;

        timer_current_time += timer_current_time_step;

        if ((--timer_countdown_to_next_gettimeofday) < 0) {
                gettimeofday(&tv, NULL);
                tv.tv_sec -= timer_start_tv.tv_sec;
                tv.tv_usec -= timer_start_tv.tv_usec;
                if (tv.tv_usec < 0) {
                        tv.tv_usec += 1000000;
                        tv.tv_sec --;
                }

#ifdef TIMER_DEBUG
                /*  For debugging/testing:  */
                {
                        double diff = tv.tv_usec * 0.000001 + tv.tv_sec
                            - timer_current_time;
                        printf("timer: lagging behind %f seconds\n", diff);
                }
#endif

                /*  Get exponentially closer to the real time, instead of
                    just changing to it directly:  */
                timer_current_time = ( (tv.tv_usec * 0.000001 + tv.tv_sec) +
                    timer_current_time ) / 2;

                timer_countdown_to_next_gettimeofday = timer_freq *
                    SECONDS_BETWEEN_GETTIMEOFDAY_SYNCH;
        }

        while (timer != NULL) {
                while (timer_current_time >= timer->next_tick_at) {
                        timer->timer_tick(timer, timer->extra);
                        timer->next_tick_at += timer->interval;
                }

                timer = timer->next;
        }

#ifdef TEST
        printf("T"); fflush(stdout);
#endif
}


/*
 *  timer_start():
 *
 *  Set the interval timer to timer_freq Hz, and install the signal handler.
 */
void timer_start(void)
{
        struct timer *timer = first_timer;
        struct itimerval val;
        struct sigaction saction;

        if (timer_is_running)
                return;

        timer_is_running = 1;

        gettimeofday(&timer_start_tv, NULL);
        timer_current_time = 0.0;

        /*  Reset all timers:  */
        while (timer != NULL) {
                timer->next_tick_at = timer->interval;
                timer = timer->next;
        }
        val.it_interval.tv_sec = 0;
        val.it_interval.tv_usec = 1000000.0 / timer_freq;
        val.it_value.tv_sec = 0;
        val.it_value.tv_usec = 1000000.0 / timer_freq;

        memset(&saction, 0, sizeof(saction));
        saction.sa_handler = timer_tick;

        sigaction(SIGALRM, &saction, NULL);

        setitimer(ITIMER_REAL, &val, NULL);
}


/*
 *  timer_stop():
 *
 *  Deinstall the signal handler, and disable the interval timer.
 */
void timer_stop(void)
{
        struct itimerval val;
        struct sigaction saction;

        if (!timer_is_running)
                return;

        timer_is_running = 0;

        val.it_interval.tv_sec = 0;
        val.it_interval.tv_usec = 0;
        val.it_value.tv_sec = 0;
        val.it_value.tv_usec = 0;

        setitimer(ITIMER_REAL, &val, NULL);

        memset(&saction, 0, sizeof(saction));
        saction.sa_handler = NULL;

        sigaction(SIGALRM, &saction, NULL);
}


#ifdef TEST
static void timer_tick_test(struct timer *t, void *extra)
{
        printf((char *) extra); fflush(stdout);
}
#endif


/*
 *  timer_init():
 *
 *  Initialize the timer framework.
 */
void timer_init(void)
{
        first_timer = NULL;
        timer_current_time = 0.0;
        timer_is_running = 0;
        timer_countdown_to_next_gettimeofday = 0;

        timer_freq = TIMER_BASE_FREQUENCY;
        timer_current_time_step = 1.0 / timer_freq;

#ifdef TEST
        timer_add(0.5, timer_tick_test, "X");
        timer_add(10.0, timer_tick_test, ".");
        timer_add(200.0, timer_tick_test, " ");
        timer_start();
        while (1)
                sleep(999999);
#endif
}

1	dpavlin	32	/*
2	dpavlin	34	* Copyright (C) 2006-2007 Anders Gavare. All rights reserved.
3	dpavlin	32	*
4			* Redistribution and use in source and binary forms, with or without
5			* modification, are permitted provided that the following conditions are met:
6			*
7			* 1. Redistributions of source code must retain the above copyright
8			* notice, this list of conditions and the following disclaimer.
9			* 2. Redistributions in binary form must reproduce the above copyright
10			* notice, this list of conditions and the following disclaimer in the
11			* documentation and/or other materials provided with the distribution.
12			* 3. The name of the author may not be used to endorse or promote products
13			* derived from this software without specific prior written permission.
14			*
15			* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16			* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17			* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18			* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19			* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20			* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21			* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22			* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23			* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24			* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25			* SUCH DAMAGE.
26			*
27			*
28	dpavlin	44	* $Id: timer.c,v 1.11 2007/06/18 04:23:19 debug Exp $
29	dpavlin	32	*
30			* Timer framework. This is used by emulated clocks.
31			*/
32
33			#include <stdio.h>
34			#include <stdlib.h>
35			#include <signal.h>
36			#include <string.h>
37			#include <unistd.h>
38			#include <sys/time.h>
39
40	dpavlin	42	#include "misc.h"
41	dpavlin	32	#include "timer.h"
42
43
44			/* #define TEST */
45
46
47			struct timer {
48			struct timer *next;
49
50			double freq;
51			void (timer_tick)(struct timer timer, void *extra);
52			void *extra;
53
54			double interval;
55			double next_tick_at;
56			};
57
58			static struct timer *first_timer = NULL;
59			struct timeval timer_start_tv;
60			static double timer_freq;
61			static int timer_countdown_to_next_gettimeofday;
62			static double timer_current_time;
63			static double timer_current_time_step;
64
65			static int timer_is_running;
66
67	dpavlin	42	#define SECONDS_BETWEEN_GETTIMEOFDAY_SYNCH 1.65
68	dpavlin	32
69
70			/*
71			* timer_add():
72			*
73			* Adds a virtual timer to the list of timers.
74			*
75			* Return value is a pointer to a timer struct.
76			*/
77			struct timer timer_add(double freq, void (timer_tick)(struct timer *timer,
78			void extra), void extra)
79			{
80	dpavlin	42	struct timer *newtimer;
81	dpavlin	32
82	dpavlin	42	CHECK_ALLOCATION(newtimer = malloc(sizeof(struct timer)));
83
84	dpavlin	32	if (freq <= 0.00000001)
85			freq = 0.00000001;
86
87			newtimer->freq = freq;
88			newtimer->timer_tick = timer_tick;
89			newtimer->extra = extra;
90
91			newtimer->interval = 1.0 / freq;
92			newtimer->next_tick_at = timer_current_time + newtimer->interval;
93
94			newtimer->next = first_timer;
95			first_timer = newtimer;
96
97			return newtimer;
98			}
99
100
101			/*
102			* timer_remove():
103			*
104			* Removes a virtual timer from the list of timers.
105			*/
106			void timer_remove(struct timer *t)
107			{
108			struct timer prev = NULL, cur = first_timer;
109
110			while (cur != NULL && cur != t) {
111			prev = cur;
112			cur = cur->next;
113			}
114
115			if (cur == t) {
116			if (prev == NULL)
117			first_timer = cur->next;
118			else
119			prev->next = cur->next;
120			free(cur);
121			} else {
122			fprintf(stderr, "attempt to remove timer %p which "
123			"doesn't exist. aborting\n", t);
124			exit(1);
125			}
126			}
127
128
129			/*
130			* timer_update_frequency():
131			*
132			* Changes the frequency of an existing timer.
133			*/
134			void timer_update_frequency(struct timer *t, double new_freq)
135			{
136			if (t->freq == new_freq)
137			return;
138
139			t->freq = new_freq;
140
141			if (new_freq <= 0.00000001)
142			new_freq = 0.00000001;
143
144			t->interval = 1.0 / new_freq;
145			t->next_tick_at = timer_current_time + t->interval;
146			}
147
148
149			/*
150			* timer_tick():
151			*
152			* Timer tick handler. This is where the interesting stuff happens.
153			*/
154			static void timer_tick(int signal_nr)
155			{
156			struct timer *timer = first_timer;
157			struct timeval tv;
158
159			timer_current_time += timer_current_time_step;
160
161			if ((--timer_countdown_to_next_gettimeofday) < 0) {
162			gettimeofday(&tv, NULL);
163			tv.tv_sec -= timer_start_tv.tv_sec;
164			tv.tv_usec -= timer_start_tv.tv_usec;
165			if (tv.tv_usec < 0) {
166			tv.tv_usec += 1000000;
167			tv.tv_sec --;
168			}
169
170	dpavlin	42	#ifdef TIMER_DEBUG
171	dpavlin	32	/* For debugging/testing: */
172			{
173			double diff = tv.tv_usec * 0.000001 + tv.tv_sec
174			- timer_current_time;
175			printf("timer: lagging behind %f seconds\n", diff);
176			}
177			#endif
178
179	dpavlin	44	/* Get exponentially closer to the real time, instead of
180			just changing to it directly: */
181			timer_current_time = ( (tv.tv_usec * 0.000001 + tv.tv_sec) +
182			timer_current_time ) / 2;
183	dpavlin	32
184			timer_countdown_to_next_gettimeofday = timer_freq *
185			SECONDS_BETWEEN_GETTIMEOFDAY_SYNCH;
186			}
187
188			while (timer != NULL) {
189			while (timer_current_time >= timer->next_tick_at) {
190			timer->timer_tick(timer, timer->extra);
191			timer->next_tick_at += timer->interval;
192			}
193
194			timer = timer->next;
195			}
196
197			#ifdef TEST
198			printf("T"); fflush(stdout);
199			#endif
200			}
201
202
203			/*
204			* timer_start():
205			*
206			* Set the interval timer to timer_freq Hz, and install the signal handler.
207			*/
208			void timer_start(void)
209			{
210			struct timer *timer = first_timer;
211			struct itimerval val;
212			struct sigaction saction;
213
214			if (timer_is_running)
215			return;
216
217			timer_is_running = 1;
218
219			gettimeofday(&timer_start_tv, NULL);
220			timer_current_time = 0.0;
221
222			/* Reset all timers: */
223			while (timer != NULL) {
224			timer->next_tick_at = timer->interval;
225			timer = timer->next;
226			}
227			val.it_interval.tv_sec = 0;
228			val.it_interval.tv_usec = 1000000.0 / timer_freq;
229			val.it_value.tv_sec = 0;
230			val.it_value.tv_usec = 1000000.0 / timer_freq;
231
232			memset(&saction, 0, sizeof(saction));
233			saction.sa_handler = timer_tick;
234
235			sigaction(SIGALRM, &saction, NULL);
236
237			setitimer(ITIMER_REAL, &val, NULL);
238			}
239
240
241			/*
242			* timer_stop():
243			*
244			* Deinstall the signal handler, and disable the interval timer.
245			*/
246			void timer_stop(void)
247			{
248			struct itimerval val;
249			struct sigaction saction;
250
251			if (!timer_is_running)
252			return;
253
254			timer_is_running = 0;
255
256			val.it_interval.tv_sec = 0;
257			val.it_interval.tv_usec = 0;
258			val.it_value.tv_sec = 0;
259			val.it_value.tv_usec = 0;
260
261			setitimer(ITIMER_REAL, &val, NULL);
262
263			memset(&saction, 0, sizeof(saction));
264			saction.sa_handler = NULL;
265
266			sigaction(SIGALRM, &saction, NULL);
267			}
268
269
270			#ifdef TEST
271			static void timer_tick_test(struct timer t, void extra)
272			{
273			printf((char *) extra); fflush(stdout);
274			}
275			#endif
276
277
278			/*
279			* timer_init():
280			*
281			* Initialize the timer framework.
282			*/
283			void timer_init(void)
284			{
285			first_timer = NULL;
286			timer_current_time = 0.0;
287			timer_is_running = 0;
288			timer_countdown_to_next_gettimeofday = 0;
289
290	dpavlin	42	timer_freq = TIMER_BASE_FREQUENCY;
291	dpavlin	32	timer_current_time_step = 1.0 / timer_freq;
292
293			#ifdef TEST
294			timer_add(0.5, timer_tick_test, "X");
295			timer_add(10.0, timer_tick_test, ".");
296			timer_add(200.0, timer_tick_test, " ");
297			timer_start();
298			while (1)
299			sleep(999999);
300			#endif
301			}
302