/*******************************************************************************
 *  The BYTE UNIX Benchmarks - Release 3
 *          Module: context1.c   SID: 3.3 5/15/91 19:30:18
 *
 *******************************************************************************
 * Bug reports, patches, comments, suggestions should be sent to:
 *
 *	Ben Smith, Rick Grehan or Tom Yager
 *	ben@bytepb.byte.com   rick_g@bytepb.byte.com   tyager@bytepb.byte.com
 *
 *******************************************************************************
 *  Modification Log:
 *  $Header: context1.c,v 3.4 87/06/22 14:22:59 kjmcdonell Beta $
 *  August 28, 1990 - changed timing routines--now returns total number of
 *                    iterations in specified time period
 *  October 22, 1997 - code cleanup to remove ANSI C compiler warnings
 *                     Andy Kahn <kahn@zk3.dec.com>
 *
 ******************************************************************************/
char SCCSid[] = "@(#) @(#)context1.c:3.3 -- 5/15/91 19:30:18";
/*
 *  Context switching via synchronized unbuffered pipe i/o
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include "timeit.c"

unsigned long iter;
int stop_timing=0;

void report()
{
	fprintf(stderr, "%lu context switches per second.\n", iter);	
	stop_timing=1;
}

void context_switch_test(int duration)
{
	unsigned long	check;
	int	p1[2], p2[2];


	/* set up alarm call */
	iter = 0;
	wake_me(duration, report);

	if (pipe(p1) || pipe(p2)) {
		perror("pipe create failed");
		exit(1);
	}

	if (fork()) {	/* parent process */
		/* master, write p1 & read p2 */
		close(p1[0]); close(p2[1]);
		while (!stop_timing) {
			if (write(p1[1], (char *)&iter, sizeof(iter)) != sizeof(iter)) {
				if ((errno != 0) && (errno != EINTR))
					perror("master write failed");
				exit(1);
			}
			if (read(p2[0], (char *)&check, sizeof(check)) != sizeof(check)) {
				if ((errno != 0) && (errno != EINTR))
					perror("master read failed");
				exit(1);
			}
			if (check != iter) {
				fprintf(stderr, "Master sync error: expect %lu, got %lu\n",
					iter, check);
				exit(2);
			}
			iter++;
		}
	}
	else { /* child process */
		unsigned long iter1;

		iter1 = 0;
		/* slave, read p1 & write p2 */
		close(p1[1]); close(p2[0]);
		while (!stop_timing) {
			if (read(p1[0], (char *)&check, sizeof(check)) != sizeof(check)) {
				if ((errno != 0) && (errno != EINTR))
					perror("slave read failed");
				exit(1);
			}
			if (check != iter1) {
				fprintf(stderr, "Slave sync error: expect %lu, got %lu\n",
					iter, check);
				exit(2);
			}
			if (write(p2[1], (char *)&iter1, sizeof(iter1)) != sizeof(check)) {
				if ((errno != 0) && (errno != EINTR))
					perror("slave write failed");
				exit(1);
			}
			iter1++;
		}
	}
}