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* {
  data = adaptData(data);

  final checksum = <int>[];

  for (var codeIndex in shortestCode(data.codeUnits)) {
    final codeValue = BarcodeMaps.code128[codeIndex]!;
    yield* add(codeValue, BarcodeMaps.code128Len);
    checksum.add(codeIndex);
  }

  // Checksum
  var sum = 0;
  for (var index = 0; index < checksum.length; index++) {
    final code = checksum[index];
    final mul = index == 0 ? 1 : index;
    sum += code * mul;
  }
  sum = sum % 103;
  yield* add(BarcodeMaps.code128[sum]!, BarcodeMaps.code128Len);

  // Stop
  yield* add(
      BarcodeMaps.code128[BarcodeMaps.code128Stop]!, BarcodeMaps.code128Len);

  // Termination Bars
  yield true;
  yield true;
}