/* $Id: bench_read.c,v 1.1 2012/02/03 15:53:01 kostik Exp kostik $ */
#include <sys/fcntl.h>
#include <sys/time.h>
#include <err.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

static void
do_reads(int fd, char *buf, size_t bufsize, int count)
{
	int i, error;

	for (i = 0; i < count; i++) {
		error = lseek(fd, 0, SEEK_SET);
		if (error != 0)
			err(1, "lseek");
		error = read(fd, buf, bufsize);
		if (error == -1)
			err(1, "read");
		else if (error != (int)bufsize)
			errx(1, "truncated read %d %d", bufsize, error);
	}
}

int
main(int argc, char *argv[])
{
	struct timeval start, end;
	char *buf;
	size_t bufsize;
	const char *filename;
	int fd;
	int count;
	double sp;

	if (argc != 4)
		errx(1, "Usage: %s file bufsize count", argv[0]);
	filename = argv[1];
	bufsize = atoi(argv[2]);
	count = atoi(argv[3]);

	buf = malloc(bufsize);
	fd = open(filename, O_RDONLY);
	if (fd == -1)
		err(1, "open %s", filename);

	gettimeofday(&start, NULL);
	do_reads(fd, buf, bufsize, count);
	gettimeofday(&end, NULL);

	sp = (end.tv_sec - start.tv_sec) +
		(end.tv_usec - start.tv_usec) * 1.0e-6;
	sp /= count;
	printf("%e\n", sp);

	return (0);
}