Re: [PATCH 2/3] hfsplus: implement attributes file's header node initialization code

[Al Viro <viro@ZenIV.linux.org.uk>]

On Wed, Sep 25, 2013 at 03:54:39PM -0700, Andrew Morton wrote:

> > +#define SETOFFSET(buf, ndsiz, offset, rec) \
> > +	(*(u16 *)((u8 *)(buf) + (ndsiz) + (-2 * (rec))) = (cpu_to_be16(offset)))
> 
> This is pretty ghastly.  Can you take a look at reimplementing it in a C
> function?  Add any necessary comments to explain what's happening and I
> expect you will find that it produces a much nicer result.

Take a look at the callers - buf and ndsiz remain unchanged, rec runs from
1 to 4.  IOW, what should be done is

	/* last 8 bytes contain offsets */
	__be16 *offsets = (__be16 *)(buf + node_size);
	...
	offset = sizeof(struct hfs_bnode_desc);
	*--offsets = cpu_to_be16(offset);
	...
	offset += sizeof(struct hfs_btree_header_rec);
	*--offsets = cpu_to_be16(offset);
	offset += HFSPLUS_BTREE_HDR_USER_BYTES;
	*--offsets = cpu_to_be16(offset);
	...
	offset += hdr_node_map_rec_bits / 8;
	*--offsets = cpu_to_be16(offset);
and to hell with that macro.

Speaking of another thing in the patch, there's that useful function called
"memset"...