On Wed, Jun 07, 2000 at 02:55:11PM +0100, Nick O'Brien wrote:
> We are looking to split our mail spool using nhash, in Exim 3.14. We are
> also using the UoW imapd (v4.7c) and qpopper, and I am trying to
> incorporate nhash into those as well.
>
> Admittedly my C is a bit rusty, but I have been having problems
> disentangling the code for nhash from the rest of source, so I can then
> slot it into the imapd and qpopper sources. I've extracted the main
> potions of the code from expand.c and am trying to hack into a form I can
> use.
What don't you understand in it?
It works on the following basis: Take a string, convert each letter to a
number and weight that number by a prime number, making sure the largest
prime used is the first. This computes a large number. Do a div/mod
operation on it and get two ints between the two values you gave it.
The only possible bug is if you have users named like:
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz@???
Then you might get a NaN error as no boundary are checked. However, this
is very unlikly. With 2.5 millions users, I never had a problem with
this.
Yes, I know I was slacking off when I wrote it ;>
> What is the best way to try and attempt this or has anyone produced any
> patches for the UoW imapd and qpopper?
Donno if it helps, but here is a perl function for it:
my @prime = (
"2", "3", "5", "7", "11", "13", "17", "19", "23", "29",
"31", "37", "41", "43", "47", "53", "59", "61", "67", "71",
"73", "79", "83", "89", "97", "101", "103", "107", "109", "113"
);
my $nbr_primes = 30;
# nhash sub
sub nhash {
my $sum = 0;
my $i = 29;
my ($div, $mod, $retval);
my ($first, $second, $string) = @_;
chomp($string);
unless ($first) {printf(STDERR "NO first value!\n"); return "ERROR";}
unless ($second) {printf(STDERR "No second value!\n"); return "ERROR";}
unless ($string) {printf(STDERR "No user name given!\n"); return "ERROR";}
foreach my $val ( split(//,$string) ) {
if ( $i == 0 ) { $i = 29 };
$sum += $prime[$i--] * ord($val);
}
$sum = $sum % ($first * $second);
$div = int($sum / $second);
$mod = int($sum % $second);
return ( $div."/".$mod );
}
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Dr Yann Golanski Internet Systems Developer
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