Re: [patch 1/4] Linux Kernel Markers - Architecture Independent Code

[Mathieu Desnoyers]

* Rusty Russell (rusty@xxxxxxxxxxxxxxx) wrote:
> On Fri, 2007-08-24 at 12:26 -0400, Mathieu Desnoyers wrote:
> > * Rusty Russell (rusty@xxxxxxxxxxxxxxx) wrote:
> > > On Mon, 2007-08-20 at 16:27 -0400, Mathieu Desnoyers wrote:
> > > > +{
> > > > +	struct hlist_head *head;
> > > > +	struct hlist_node *node;
> > > > +	struct marker_entry *e;
> > > > +	size_t len = strlen(name) + 1;
> > > > +	u32 hash = jhash(name, len-1, 0);
> > > > +
> > > > +	head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
> > > > +	hlist_for_each_entry(e, node, head, hlist) {
> > > > +		if (!strcmp(name, e->name))
> > > > +			return e;
> > > > +	}
> > > > +	return NULL;
> > > > +}
> > > 
> > > OK, don't understand the strlen, len, len-1 dance here?
> > > 
> > 
> > Let's say we have abc\0 for marker name as name input.
> > 
> > len = 3 + 1 = 4 (including \0)
> > hash is done only on the 3 first chars, excluding the \0 (therefore the
> >                                                           len-1 there)
> > 
> > Actually, it's like this only for a matter of consistency between
> > add_marker and remove_marker, which are quite similar, but add_marker
> > needs name_len to include the \0 value. It would be odd to change the
> > logic between the two functions to one including the \0 and the other
> > excluding it.
> 
> Sure, but that doesn't really explain why the code does:
> 
> 	size_t len = strlen(name) + 1;
> 	u32 hash = jhash(name, len-1, 0);
> 
> Rather than:
> 
> 	u32 hash = jhash(name, strlen(name), 0);
> 

Yup, good point. Fixed.

Thanks,

Mathieu

> > Thanks for the review,
> 
> That's fine, just some light reading...
> 
> Cheers,
> Rusty.
> > 
> 

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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