pretty_hex.dart

  String prettyHex(List<int> bytes, int length) {
    final buffer = StringBuffer();
    for (var i = 0; i < bytes.length; i += length) {
      final list = bytes.sublist(i, min(i + length, bytes.length));
      final l1 = list.map((e) => e.toRadixString(16).padLeft(2, '0')).toList();
      final l2 = list.map((e) {
        if (e > 0 && e < 128) {
          return ascii.decode([e]);
        }
        return '.';
      }).toList();
      buffer.writeln('${l1.join(' ').padRight(length * 3)} | ${l2.join()}');
    }
    return buffer.toString();
  }