#define _FILE_OFFSET_BITS	64
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/uio.h>

int main(int argc, char *argv[])
{
	off_t offset = 0;
	int h, r;
	char *m;
	int ps = getpagesize();
	struct iovec iov[2];
	if (argc < 2) fprintf(stderr, "argc\n"), exit(1);
	if (argc >= 3) offset = strtoull(argv[2], NULL, 16);
	h = open(argv[1], O_RDONLY | O_DIRECT);
	if (h == -1) perror("open"), exit(1);
	m = valloc(ps);
	if (!m) perror("valloc"), exit(1);
	iov[0].iov_base = m;
	iov[0].iov_len = ps;
	iov[1].iov_base = m;
	iov[1].iov_len = ps;
	r = preadv(h, iov, 2, offset);
	if (r < 0) perror("readv"), exit(1);
	if (close(h)) perror("close"), exit(1);
	return 0;
}