convert method

@override Iterable<bool> convert(String data)

Actual barcode computation method, returns a stream of bool which represents the presence or absence of a bar

Implementation

@override
Iterable<bool> convert(String data) sync* {
  if (fixedLength != null) {
    data = checkLength(data, fixedLength!);
  } else {
    if (zeroPrepend && ((data.length % 2 != 0) != addChecksum)) {
      data = '0$data';
    }

    if (addChecksum) {
      data += checkSumModulo10(data);
    }

    if (data.length % 2 != 0) {
      throw BarcodeException(
          '$name barcode can only encode an even number of digits.');
    }
  }

  // Start
  yield* add(BarcodeMaps.itfStart, 4);

  final cu = data.codeUnits;
  for (var i = 0; i < cu.length / 2; i++) {
    final tuple = <int?>[
      BarcodeMaps.itf[cu[i * 2]],
      BarcodeMaps.itf[cu[i * 2 + 1]]
    ];

    if (tuple[0] == null || tuple[1] == null) {
      throw BarcodeException(
          'Unable to encode "${String.fromCharCode(cu[i * 2])}${String.fromCharCode(cu[i * 2 + 1])}" to $name Barcode');
    }

    for (var n = 0; n < 10; n++) {
      final v = (tuple[n % 2]! >> (n ~/ 2)) & 1;
      final c = n % 2 == 0;
      yield c;
      if (v != 0) {
        yield c;
        yield c;
      }
    }
  }

  // End
  yield* add(BarcodeMaps.itfEnd, 5);
}