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lib/Digest/ssdeep.pm  view on Meta::CPAN

    # Returns: the actual rolling hash value
    sub _roll_hash {
        my $char    = shift;
        my $char7bf = shift @last7chars;

        push @last7chars, $char;

        $roll_h2 += 7 * $char - $roll_h1;
        $roll_h1 += $char - $char7bf;

        $roll_h3 <<= 5;    # 5*7 = 35 (so it vanish after 7 iterations)
        $roll_h3 &= 0xffffffff;
        $roll_h3 ^= $char;

        #printf("c=%d  cAnt=%d    H1=%u  H2=%u  H3=%u\n",
        #	$char, $char7bf,
        #	$roll_h1, $roll_h2, $roll_h3);

        return $roll_h1 + $roll_h2 + $roll_h3;
    }