[Sheepdog] [PATCH 2/5] sheep: add some candy helpers in util.c

[Liu Yuan]

On 11/16/2011 01:50 PM, MORITA Kazutaka wrote:

>>>
>>> We already have a hash function, fnv_64a_buf().  How about using it
>>> instead of introducing new one?
>>>
>>
>>
>> When I need a hash function that inputs an integer and outputs an
>> integer for specified bits, I looked at the fnv_64a_buf(), it seems to
>> me it tries to hash an string to integer. So I think these hash
>> functions do a different thing, no?
> 
> We already use it to calculate a hash value from a 64 bit object id:
> 
>   fnv_64a_buf(&oid, sizeof(uint64_t), FNV1A_64_INIT);
> 
> I guess this generates a less random value than hash_64(), though.


Umm, I didn't go over usage close enough, and this interface is more
named to handle string hash, at least to me.

So even we use it to hash integer, we need to further bit operation to
remove extra bits. hash_long(hval, bits) has a nicer and more intuitive
interface to handle integer.

How about coexisting these two? fnv_64a_buf() is supposed to handle
string hash and hash_long() is supposed to handle integer otherwise.

Thanks,
Yuan