Re: Hashing on System.Address

["Matthew Heaney" <mheaney@on2.com>]

Duncan Sands wrote:
> > Use System.Storage_Elements.To_Integer to convert the address to an
> > Integer_Address, and then convert that to type Hash_Type.
>
> that's what I'm doing.  But there's no guarantee that they have the
> same size, so it's not portable.

Even if the Integer_Address type is 64 bits, that doesn't necessarily
mean To_Address will return values > 2**32.  The easiest thing is to do
is just throw away the upper 32 bits of of the integer value, and then
convert that to type Hash_Type.

Yes, then means you won't have a perfect hash function, but that's
typical for hash functions anyway.  (The Birthday Paradox applies to
hash functions too, I think.)

You might want to post your question on comp.compilers or one of the OS
newgroups.  This is most probably a solved problem.

-Matt