Τη Τρίτη, 22 Ιανουαρίου 2013 9:16:34 μ.μ. UTC+2, ο χρήστης Peter Otten έγραψε:
> Ferrous Cranus wrote:
>
>
>
> > Τη Τρίτη, 22 Ιανουαρίου 2013 6:11:20 μ.μ. UTC+2, ο χρήστης Chris Angelico
>
> > έγραψε:
>
>
>
> >> all of it. You are asking something that is fundamentally
>
> >> impossible[1]. There simply are not enough numbers to go around.
>
>
>
> > Fundamentally impossible?
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> >
>
> > Well....
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> >
>
> > OK: How about this in Perl:
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> >
>
> > $ cat testMD5.pl
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> > use strict;
>
> >
>
> > foreach my $url(qw@ /index.html /about/time.html @){
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> > hashit($url);
>
> > }
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> >
>
> > sub hashit {
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> > my $url=shift;
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> > my @ltrs=split(//,$url);
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> > my $hash = 0;
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> >
>
> > foreach my $ltr(@ltrs){
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> > $hash = ( $hash + ord($ltr)) %10000;
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> > }
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> > printf "%s: %0.4d\n",$url,$hash
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> >
>
> > }
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> >
>
> >
>
> > which yields:
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> > $ perl testMD5.pl
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> > /index.html: 1066
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> > /about/time.html: 1547
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>
>
> $ cat clashes.pl
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> use strict;
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>
>
> foreach my $url(qw@
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> /public/fails.html
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> /large/cannot.html
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> /number/being.html
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> /hope/already.html
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> /being/really.html
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> /index/breath.html
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> /can/although.html
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> @){
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> hashit($url);
>
> }
>
>
>
> sub hashit {
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> my $url=shift;
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> my @ltrs=split(//,$url);
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> my $hash = 0;
>
>
>
> foreach my $ltr(@ltrs){
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> $hash = ( $hash + ord($ltr)) %10000;
>
> }
>
> printf "%s: %0.4d\n",$url,$hash
>
>
>
> }
>
> $ perl clashes.pl
>
> /public/fails.html: 1743
>
> /large/cannot.html: 1743
>
> /number/being.html: 1743
>
> /hope/already.html: 1743
>
> /being/really.html: 1743
>
> /index/breath.html: 1743
>
> /can/although.html: 1743
>
>
>
> Hm, I must be holding it wrong...
my @i = split(//,$url); # put each letter in it's own bin
my $j=0; # Initailize our
my $k=1; # hashing increment values
my @m=(); # workspace
foreach my $n(@i){
my $q=ord($n); # ASCII for character
$k += $j; # Increment our hash offset
$q += $k; # add our "old" value
$j = $k; # store that.
push @m,$q; # save the offsetted value
}
my $hashval=0; #initialize our hash value
# Generate that
map { $hashval = ($hashval + $_) % 10000} @m;
Using that method ABC.html and CBA.html now have different values because each
letter position's value gets bumped up increasingly from left to right.
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