ext2fs_bufatoff
int ext2fs_bufatoff(struct inode *, off_t, char **, struct buf **);
(error = ext2fs_bufatoff(dp, (off_t)dp->i_offset,
error = ext2fs_bufatoff(dp, (off_t)dp->i_offset, NULL, &bp);
if ((error = ext2fs_bufatoff(dp, (off_t)dp->i_offset, &dirbuf, &bp))
error = ext2fs_bufatoff(dp, (off_t)dp->i_offset, (char **)&ep,
error = ext2fs_bufatoff(dp, (off_t)(dp->i_offset - dp->i_count),
error = ext2fs_bufatoff(dp, (off_t)dp->i_offset, (char **)&ep, &bp);