#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>

#include <fcntl.h>

#include <err.h>
#include <errno.h>

#define NR 256
#define SIZE 4096

int main(int argc, char **argv)
{
	int fd, rc, n, iter = 0;
	const char *path;
	static unsigned char  __attribute__ ((aligned (4096))) buf[NR][SIZE];

	if (argc != 2) {
		fprintf(stderr, "usage: blktest2 [PATH]\n");
		exit(1);
	}
	path = argv[1];

	printf("opening %s for O_DIRECT access\n", path);
	fd = open(path, O_CREAT/*|O_DIRECT*/|O_RDWR, 0666);
	if (fd < 0)
		err(1,"unable to open file");

	while(1) {
		if ((iter%10)==0)
			printf("iteration %d ...", iter);
		if (lseek(fd, (iter%NR)*SIZE, SEEK_SET) < 0)
			err(1, "seek for write %d %d\n", iter, n);
		memset(buf[iter%NR], 0xaa, SIZE);
		rc = write(fd, buf[iter%NR], SIZE);
		memset(buf[iter%NR], 0x55, SIZE);
		if (rc == -1)
			//warn("write failed");
			err(1, "write failed");
		else if (rc != SIZE)
			err(1, "only wrote %d/%d bytes\n", rc, SIZE);
		if ((iter%10)==0)
			printf("\n", iter);

		iter++;
	}
}