use strict;
use warnings;
use Fcntl ':seek';

use constant CHUNK => 65536;

sub calc {
    my $file  = shift or die "no filename given\n";
    my $hash  = -s $file;
    my $chunk = CHUNK;

    $hash < $chunk and die "$file is too small ($hash bytes < $chunk)\n";

    open my $in, '<', $file or die "Cannot open $file for input: $!\n";
    local $/ = \$chunk;

    $hash += ord($_) for split //, readline($in);
    seek($in, SEEK_END, -$chunk);
    $hash += ord($_) for split //, readline($in);

    close $in;
    return sprintf '%016x', $hash;
}

print calc($_), "\t$_\n" for @ARGV;