#include <sys/types.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <err.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

#define timespecsub(vvp, uvp)						\
	do {								\
		(vvp)->tv_sec -= (uvp)->tv_sec;				\
		(vvp)->tv_nsec -= (uvp)->tv_nsec;			\
		if ((vvp)->tv_nsec < 0) {				\
			(vvp)->tv_sec--;				\
			(vvp)->tv_nsec += 1000000000;			\
		}							\
	} while (0)

void
inittest(int nprocs)
{
	int i;
	int val;

	if (setpgid(getpid(), getpid()) != 0)
		err(1, "setpgid");

	val = 99999;
	if (sysctlbyname("kern.randompid", NULL, NULL, &val, sizeof(int)) != 0)
		err(1, "sysctlbyname(\"kern.randompid\")");

	for (i = 0; i < nprocs; i++) {
		switch (fork()) {
		case 0:
			pause();
			exit(0);
		default:
			break;
		case -1:
			err(1, "fork");
		}
	}

	val = 0;
	if (sysctlbyname("kern.randompid", NULL, NULL, &val, sizeof(int)) != 0)
		err(1, "sysctlbyname(\"kern.randompid\")");
}

void
runtest(void)
{
	pid_t pid;
	int dummy;

	switch (pid = fork()) {
	case 0:
		exit(0);
	default:
		wait4(pid, &dummy, 0, NULL);
		break;
	case -1:
		err(1, "fork");
	}
}

void
cleantest(void)
{
	int dummy;

	killpg(0, SIGINT);	/* XXX doesn't work */
}

int
main(int argc, char *argv[])
{
	struct timespec start, end;
	int i, iters, nprocs;

	if (argc != 3)
		errx(1, "usage: %s processes iterations", argv[0]);
	nprocs = atoi(argv[1]);
	if (nprocs < 0)
		errx(1, "number of processes must be nonnegative");
	iters = atoi(argv[2]);
	if (iters <= 0)
		errx(1, "iterations must be positive");

	inittest(nprocs);

	if (clock_gettime(CLOCK_REALTIME, &start) != 0)
		err(1, "clock_gettime");
	for (i = 0; i < iters; i++)
		runtest();
	if (clock_gettime(CLOCK_REALTIME, &end) != 0)
		err(1, "clock_gettime");

	timespecsub(&end, &start);
	printf("%ju.%09ju\n", (uintmax_t)end.tv_sec, (uintmax_t)end.tv_nsec);
	fflush(stdout);

	cleantest();
	exit(0);
}