Re^5: Using filepath method to identify an .html page

[blue_cowdawg]

in reply to Re^4: Using filepath method to identify an .html page
in thread Using filepath method to identify an .html page

The perl code will produce the same hash for "abc.html" as for "bca.html"

Which underscores the point I made earlier about adding collision detection and rehashing logic to whatever algorithm you use. One workround I've seen:

| handwaving  here...
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.