Re: hash function over IP address

From	Eric Sosman <esosman@ieee-dot-org.invalid>
Newsgroups	comp.programming, comp.unix.programmer
Subject	Re: hash function over IP address
Date	2012-04-05 22:24 -0400
Organization	A noiseless patient Spider
Message-ID	<jllk4e$mv2$1@dont-email.me> (permalink)
References	<jliber$ocn$1@speranza.aioe.org> <jlir5m$dd8$1@dont-email.me> <jlk3um$pog$1@speranza.aioe.org> <87bon65l7n.fsf@sapphire.mobileactivedefense.com> <jlkb2b$d5f$1@speranza.aioe.org>

Cross-posted to 2 groups.

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On 4/5/2012 10:43 AM, Mark wrote:
> "Rainer Weikusat"<rweikusat@mssgmbh.com>  wrote in message
> news:87bon65l7n.fsf@sapphire.mobileactivedefense.com...
>>> So the search was based on 'struct nhlfe_key'. Now, what I'm trying to
>>> add
>>> support for multiple next hops, that is I add a linked list in
>>> nhlfe_entry:
>>> struct nhlfe_entry{  u_int32_t nhlfe_ix;  u_char opcode;  ...  struct
>>> list
>>> *nhkey_list;}where 'struct list' is struct listnode that embeds 'void
>>> *data'
>>> pointer to caller'sprivate data, and this is 'struct nhlfe_key'.So I'm
>>> trying to find the way to generate key based on multiple elements in the
>>> list to store/search nodes in the tree.
>>
>> The simplest solution would be to concatenate all 'next hops' in
>> order to form a key.
>
> Number of next hops is variable, thus anyway it would require to delete the
> node and re-insert it back with a new key generated, right? (that's not an
> issue though). How would you suggest to concatenate 32-bit long unsigned
> integers, in what form -- convert to strings, concatenate and use such
> string as a key?

     What are you trying to *do* with this key?  Yes, we know, you're
using it to order the nodes in an AVL tree -- but that's like the guy
saying "I'm stacking bricks on top of other bricks" instead of saying
"I'm building a cathedral."  Tell us what you want to do with this AVL
tree once you have it: Especially, tell us what you'll have in your
hand when you knock on its door and ask "Have you got one of THESE?"

     Are you holding a single IP address, and looking for all the
multi-address routes that begin there?

     Are you holding a single IP address, and looking for all the
routes that include it anywhere?

     Are you holding an entire sequence of IP addresses, and looking
for that exact route?

     Are you holding a sequence of addresses, looking for all routes
that begin with that sequence?

     ... or what?  These are all "search problems," but they're of
rather different character and require rather different responses.

-- 
Eric Sosman
esosman@ieee-dot-org.invalid

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hash function over IP address "Mark" <mark_cruzNOTFORSPAM@hotmail.com> - 2012-04-04 16:37 -0400
  Re: hash function over IP address Barry Margolin <barmar@alum.mit.edu> - 2012-04-04 16:49 -0400
    Re: hash function over IP address China Blue Water Navy <chine.bleu@yahoo.com> - 2012-04-04 14:02 -0700
    Re: hash function over IP address "Mark" <mark_cruzNOTFORSPAM@hotmail.com> - 2012-04-04 17:21 -0400
      Re: hash function over IP address Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-04-04 14:47 -0700
  Re: hash function over IP address Ben Pfaff <blp@cs.stanford.edu> - 2012-04-04 14:40 -0700
    Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-04 22:52 +0100
      Re: hash function over IP address blp@cs.stanford.edu (Ben Pfaff) - 2012-04-04 15:35 -0700
        Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-05 12:08 +0100
          Re: hash function over IP address blp@cs.stanford.edu (Ben Pfaff) - 2012-04-05 07:42 -0700
            Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-05 16:29 +0100
          Re: hash function over IP address Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-04-05 10:05 -0700
            Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-05 18:12 +0100
              Re: hash function over IP address Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-04-05 10:23 -0700
                Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-05 18:34 +0100
                Re: hash function over IP address Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-04-05 11:11 -0700
                Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-05 19:34 +0100
                Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-05 19:38 +0100
                Re: hash function over IP address Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-04-05 12:18 -0700
            Re: hash function over IP address scott@slp53.sl.home (Scott Lurndal) - 2012-04-05 18:45 +0000
              Re: hash function over IP address "Mark" <mark_cruzNOTFORSPAM@hotmail.com> - 2012-04-05 15:02 -0400
  Re: hash function over IP address Rick Jones <rick.jones2@hp.com> - 2012-04-04 23:18 +0000
  Re: hash function over IP address William Ahern <william@wilbur.25thandClement.com> - 2012-04-04 16:57 -0700
  Re: hash function over IP address Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-04-04 21:05 -0400
    Re: hash function over IP address Barry Margolin <barmar@alum.mit.edu> - 2012-04-04 22:52 -0400
      Re: hash function over IP address Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-04-05 08:46 -0400
    Re: hash function over IP address "Mark" <mark_cruzNOTFORSPAM@hotmail.com> - 2012-04-05 08:42 -0400
      Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-05 15:04 +0100
        Re: hash function over IP address "Mark" <mark_cruzNOTFORSPAM@hotmail.com> - 2012-04-05 10:43 -0400
          Re: hash function over IP address Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-04-05 22:24 -0400
          Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-06 17:13 +0100
            Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-06 17:21 +0100
            Re: hash function over IP address "Mark" <mark_cruzNOTFORSPAM@hotmail.com> - 2012-04-09 10:04 -0400
              Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-09 15:54 +0100
  Re: hash function over IP address BGB <cr88192@hotmail.com> - 2012-04-04 20:21 -0700
  Re: hash function over IP address Udit Gangwani <uditg22@gmail.com> - 2012-04-05 00:26 -0700
  Re: hash function over IP address Rainer Weikusat <rweikusat@mssgmbh.com> - 2012-04-05 12:15 +0100
    Re: hash function over IP address Barry Margolin <barmar@alum.mit.edu> - 2012-04-05 07:52 -0400

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