#!/usr/bin/perl -w
use strict;

die "need file as parameter" unless my $file = $ARGV[0];

open(my $fh, $file) or die "Can't open file $file: $!";
die "File $file is too small!" if -s $file < 65536;

my $hashstring = -s $file;

#calculate first 64kb
for(1 .. 65536/8) {
	read($fh, my $byte, 4);
	my $ll = unpack("LL", $byte);
	#here is missing code
}

#calculate last 64kb
seek $fh, -65536, 2;
for(1 .. 65536/8) {
	read($fh, my $byte, 4);
	my $ll = unpack("LL", $byte);
	#here is missing code
}
close($fh);

printf("Hash of $file is: %016x", $hashstring);