On Thu, Aug 02, 2012 at 12:00:33PM +0200, Sasha Levin wrote:
> On 08/02/2012 12:45 AM, Tejun Heo wrote:
> > On Thu, Aug 02, 2012 at 12:41:56AM +0200, Sasha Levin wrote:
> >> How would your DEFINE_HASHTABLE look like if we got for the simple
> >> 'struct hash_table' approach?
> >
> > I think defining a different enclosing anonymous struct which the
> > requested number of array entries and then aliasing the actual
> > hash_table to that symbol should work. It's rather horrible and I'm
> > not sure it's worth the trouble.
>
> I agree that this is probably not worth the trouble.
>
> At the moment I see two alternatives:
>
> 1. Dynamically allocate the hash buckets.
>
> 2. Use the first bucket to store size. Something like the follows:
>
> #define HASH_TABLE(name, bits) \
> struct hlist_head name[1 << bits + 1];
>
> #define HASH_TABLE_INIT (bits) ({name[0].next = bits});
>
> And then have hash_{add,get} just skip the first bucket.
>
>
> While it's not a pretty hack, I don't see a nice way to avoid having to dynamically allocate buckets for all cases.
What about using a C99 flexible array member? Kernel style prohibits
variable-length arrays, but I don't think the same rationale applies to
flexible array members.
struct hash_table {
size_t count;
struct hlist_head buckets[];
};
#define DEFINE_HASH_TABLE(name, length) struct hash_table name = { .count = length, .buckets = { [0 ... (length - 1)] = HLIST_HEAD_INIT } }
- Josh Triplett
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>