sub ScanDirectory {
    my ($workdir) = @_;

    my($startdir) = &cwd; # keep track of where we began

    chdir($workdir) or die "Unable to enter dir $workdir: $!\n";
    
    opendir(DIR, ".") or die "Unable to open $workdir: $!\n";
        my @names = readdir(DIR);
    closedir(DIR);

    foreach my $name (@names){

        next if ($name eq ".");
        next if ($name eq "..");
        next if ($name =~ /\.dat$|\.mdb^|\.snapshot/);

        if ( -d $name ) {
			if ($name =~ /^\d+\@\w/ ) {
				$all_mailbox_count++;
				$box_size=0;
			}

			&ScanDirectory($name);
			next;
		}

		if ( $name =~ /\.msg$/ ) {
			my $msg_size=(stat($name))[7];
			if ( $msg_size < 4096 ) {
			$box_size+=4096;
			} else {
				$box_size+=$msg_size;
			}
		}
	}

       if ( $workdir =~ /(\d+)\@/ ) {
			$msisdn=$1;
			$all_mailbox_size+=$box_size;
			if ( $box_size == 0 ) {
				$empty_mailbox++;
			} else {
				&top_size_mailbox($msisdn,$box_size);
			}
		}

        chdir($startdir) or die "Unable to change to dir $startdir: $!\n";
}


sub top_size_mailbox {

        my ($msisdn,$box_size)=@_;

        if ( keys( %top_size_mailbox ) < $num_top_size_box ) {
                $top_size_mailbox{$box_size}=$msisdn;
        } else {
                my $min=(sort {$a <=> $b} keys %top_size_mailbox)[0];
                if ( $box_size > $min ) {
                    delete $top_size_mailbox{$min};
                    $top_size_mailbox{$box_size}=$msisdn;
                }
        }

}