Implementation
@override
Iterable<int> get charSet => BarcodeMaps.code128B.keys
.where((int x) => useCode128B && x >= 0)
.followedBy(BarcodeMaps.code128A.keys.where((int x) => useCode128A && x >= 0))
.followedBy(useCode128C ? List<int>.generate(10, (int index) => index + 0x30) : <int>[])
.followedBy(<int>[
BarcodeMaps.code128FNC1,
if (useCode128A || useCode128B) BarcodeMaps.code128FNC2,
if (useCode128A || useCode128B) BarcodeMaps.code128FNC3,
if (useCode128A || useCode128B) BarcodeMaps.code128FNC4,
if (isGS1) ...<int>[40, 41],
])
.toSet();