Date: Tue, 8 Oct 1996 17:56:32 +1000 From: Bruce Evans <bde@zeta.org.au> To: louie@TransSys.COM, terry@lambert.org Cc: ache@nagual.ru, bde@zeta.org.au, current@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG, joerg_wunsch@uriah.heep.sax.de, wollman@lcs.mit.edu Subject: Re: I plan to change random() for -current (was Re: rand() and random()) Message-ID: <199610080756.RAA27388@godzilla.zeta.org.au>
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>I have to agree with Terry here about "fixing" rand()/srand(). For
>better or worse, there are expections on the implementation of these
>functions in a standard C libarary. For instance, in a recent
>Internet Draft of a protocol specification for multicast routing
>protocol (draft-ietf-idmr-pim-sm-spec-05.txt):
>> 3.7 Hash Function
>>....
>> 1 For each candidate RP address Ci in the Candidate-RP-
>> Set, whose Group-prefix covers G, compute a value:
>> Value(G,M,Ci) =
>> 1103515245 ((1103515245 (G&M)+12345) XOR Ci)+ 12345 mod 2^31
If you want exactly that, use your own routine. Apparently a quality
hash function isn't required.
>> In standard C, this corresponds to:
^^^^^^^^^^ the usual (low quality) BSD implementation
of the Standard C library functions srand()
and rand()
>>
>> srand(G & M);
>> srand(rand() ^ Ci);
>> value = rand();
Bruce
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