sub safe_encode
  { my $str= shift;
       $str =~ s{([\xC0-\xDF].|[\xE0-\xEF]..|[\xF0-\xFF]...)}
	        {XmlUtf8Decode ($1)}egs;
      return $str;
  }

sub XmlUtf8Decode
  { my ($str, $hex) = @_;
    my $len = length ($str);
    my $n;

    if ($len == 2)
      { my @n = unpack "C2", $str;
	$n = (($n[0] & 0x3f) << 6) + ($n[1] & 0x3f);
      }
    elsif ($len == 3)
    { my @n = unpack "C3", $str;
      $n = (($n[0] & 0x1f) << 12) + (($n[1] & 0x3f) << 6) + ($n[2] & 0x3f);
    }
    elsif ($len == 4)
    { my @n = unpack "C4", $str;
      $n = (($n[0] & 0x0f) << 18) + (($n[1] & 0x3f) << 12)
         + (($n[2] & 0x3f) << 6) + ($n[3] & 0x3f);
    }
    elsif ($len == 1)	# just to be complete...
    { $n = ord ($str); }
    else
    { die "bad value [$str] for XmlUtf8Decode"; }

    $hex ? sprintf ("&#x%x;", $n) : "&#$n;";
}