use strict;
use Digest::MD5;

sub get_md5 {
  my $file = shift;

  open (my $fh, '<', $file) or die "cannot open $file - $1";
  binmode($fh);

  my $md5 = Digest::MD5->new;
  $md5->addfile($fh);

  close($fh) or die "cannot close $file - $!";

  return $md5->hexdigest; # TODO: think about caching results...
}


sub files_equal_by_md5 {
  my ($file1, $file2) = @_;

  # files differ in size? 
  return 0 if (-s $file1 != -s $file2);

  my $digest1 = get_md5($file1);
  my $digest2 = get_md5($file2);

  return $digest1 eq $digest2 ? 1 : 0;
}

die "usage: $0 file1 file2\n compares file1 and file 2\n" unless @ARGV==2;
print files_equal_by_md5($ARGV[0],$ARGV[1])
  ? "files are equal"
  : "different files",
  "\n";