cpu_sin_signal.c

#include <math.h>
#include <signal.h>
#include <unistd.h>
#include <sys/time.h>

#define INTERVAL 50000
#define SAMPLES 200

int sleep_interval[SAMPLES];

void sleep_a_while(int sig)
{
	static int idx = 0;
	usleep(sleep_interval[idx++]);
	idx %= SAMPLES;
}

void init_sleep_interval(void)
{
	int i;
	for (i = 0; i < SAMPLES; ++i)
		sleep_interval[i] = (sin(M_PI*2*i/SAMPLES) + 1) * INTERVAL / 2;
}

int main(int argc, char *argv[])
{
	init_sleep_interval();
	signal(SIGALRM, sleep_a_while);

	struct itimerval timer = {
		.it_interval = { .tv_sec = 0, .tv_usec = INTERVAL },
		.it_value = {.tv_sec = 0, .tv_usec = INTERVAL },
	};

	setitimer(ITIMER_REAL, &timer, NULL);

	for (;;)
		;

	return 0;
}

cpu_sin_time.c

#include <math.h>
#include <signal.h>
#include <unistd.h>
#include <sys/time.h>

#define INTERVAL 50000
#define SAMPLES 200

int sleep_interval[SAMPLES];

void init_sleep_interval(void)
{
	int i;
	for (i = 0; i < SAMPLES; ++i)
		sleep_interval[i] = (sin(M_PI*2*i/SAMPLES) + 1) * INTERVAL / 2;
}

int main(int argc, char *argv[])
{
	struct timeval hd, tl;
	int idx = 0;

	init_sleep_interval();

	for (;;) {
		gettimeofday(&hd, NULL);
		tl = hd;
		while (tl.tv_sec * 1000000 + tl.tv_usec - hd.tv_sec * 1000000 - hd.tv_usec < INTERVAL - sleep_interval[idx])
			gettimeofday(&tl, NULL);
		usleep(sleep_interval[idx++]);
		idx %= SAMPLES;
	}
	return 0;
}