convert method
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* {
yield* add(BarcodeMaps.code39StartStop, BarcodeMaps.code39Len);
for (var code in data.codeUnits) {
final codeValue = BarcodeMaps.code39[code];
if (codeValue == null) {
throw BarcodeException(
'Unable to encode "${String.fromCharCode(code)}" to $name Barcode');
}
yield* add(codeValue, BarcodeMaps.code39Len);
}
yield* add(BarcodeMaps.code39StartStop, BarcodeMaps.code39Len);
}