[Mesa-dev] [PATCH] util/hash_table: Rework the API to know about hashing

Kenneth Graunke kenneth at whitecape.org
Tue Nov 25 00:58:38 PST 2014

On Monday, November 24, 2014 10:19:50 PM Jason Ekstrand wrote:
> Previously, the hash_table API required the user to do all of the hashing
> of keys as it passed them in.  Since the hashing function is intrinsicly
> tied to the comparison function, it makes sense for the hash table to know
> about it.  Also, it makes for a somewhat clumsy API as the user is
> constantly calling hashing functions many of which have long names.  This
> is especially bad when the standard call looks something like
> _mesa_hash_table_insert(ht, _mesa_pointer_hash(key), key, data);
> In the above case, there is no reason why the hash table shouldn't do the
> hashing for you.  We leave the option for you to do your own hashing if
> it's more efficient, but it's no longer needed.  Also, if you do do your
> own hashing, the hash table will assert that your hash matches what it
> expects out of the hashing function.  This should make it harder to mess up
> your hashing.
> Signed-off-by: Jason Ekstrand <jason.ekstrand at intel.com>

(CC'ing Eric to make sure he sees your patch - it's his code after all)

Yes, please - the new API looks much nicer to work with.  This should be
especially nice in the compiler, where we have a lot of hash tables, and
aren't concerned with saving every last CPU cycle.

I like that there are still _with_hash variants, so you can still compute
the hash once and use it multiple times where that makes sense.

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