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* {
  // Start
  yield* add(BarcodeMaps.code93StartStop, BarcodeMaps.code93Len);

  final keys = BarcodeMaps.code93.keys.toList();

  for (var code in data.codeUnits) {
    final codeValue = BarcodeMaps.code93[code];
    if (codeValue == null) {
      throw BarcodeException(
          'Unable to encode "${String.fromCharCode(code)}" to $name Barcode');
    }
    yield* add(codeValue, BarcodeMaps.code93Len);
  }

  // Checksum
  var sumC = 0;
  var sumK = 0;
  var indexC = 1;
  var indexK = 2;

  for (var index = data.codeUnits.length - 1; index >= 0; index--) {
    final code = data.codeUnits[index];
    sumC += keys.indexOf(code) * indexC;
    sumK += keys.indexOf(code) * indexK;

    indexC++;
    if (indexC > 20) {
      indexC = 1;
    }
    indexK++;
    if (indexK > 15) {
      indexK = 1;
    }
  }

  sumC = sumC % 47;
  yield* add(BarcodeMaps.code93[keys[sumC]]!, BarcodeMaps.code93Len);

  sumK = (sumK + sumC) % 47;
  yield* add(BarcodeMaps.code93[keys[sumK]]!, BarcodeMaps.code93Len);

  // Stop
  yield* add(BarcodeMaps.code93StartStop, BarcodeMaps.code93Len);

  // Termination Bar
  yield true;
}