-struct file;
-bool dir_init (struct dir *, size_t entry_cnt);
-void dir_destroy (struct dir *);
-void dir_read (struct dir *, struct file *);
-void dir_write (struct dir *, struct file *);
-bool dir_lookup (const struct dir *, const char *name, disk_sector_no *);
-bool dir_add (struct dir *, const char *name, disk_sector_no);
+/* Reading and writing. */
+bool dir_lookup (const struct dir *, const char *name, struct inode **);
+bool dir_add (struct dir *, const char *name, disk_sector_t);