convert method

@override Iterable<bool> convert(String data)

Implementation

@override
Iterable<bool> convert(String data) sync* {
  verify(data);
  int idata;
  try {
    idata = int.parse(data);
  } catch (e) {
    throw BarcodeException('Unable to encode "$data" to $name Barcode');
  }
  final int pattern = idata % 4;

  yield* add(BarcodeMaps.eanStartEan2, 5);

  int index = 0;
  for (final int code in data.codeUnits) {
    final List<int>? codes = BarcodeMaps.ean[code];

    if (codes == null) {
      throw BarcodeException('Unable to encode "${String.fromCharCode(code)}" to $name Barcode');
    }

    if (index == 1) {
      yield* add(BarcodeMaps.eanCenterEan2, 2);
    }

    if (index == 0) {
      yield* add(codes[pattern < 2 ? 0 : 1], 7);
    } else {
      yield* add(codes[pattern % 2 == 0 ? 0 : 1], 7);
    }
    index++;
  }
}