sub quickMD5 {
    my $fh = shift;
    my $md5 = new Digest::MD5->new;

    $md5->add( -s $fh );

    my $pos = 0;
    until( eof $fh ) {
        seek $fh, $pos, 0;
        read( $fh, my $block, 4096 ) or last;
        $md5->add( $block );
        $pos += 1024**2;
    }
    return $md5;
}