int fstat(int fd, struct stat *);

/* opendir:  open a directory for readdir calls */
DIR *opendir(char *dirname)
{
	int fd;
	struct stat stbuf;
	DIR *dp;

	if ((fd = open(dirname, O_RDONLY, 0)) == -1
	 || fstat(fd, &stbuf) == -1
	 || (stbuf.st_mode & S_IFMT) != S_IFDIR
	 || (dp = (DIR *) malloc(sizeof(DIR))) == NULL)
		return NULL;
	dp->fd = fd;
	return dp;	
}