pad method
Implementation
@override
String pad(String data, int maxLength) {
if (data.length > maxLength) throw ArgumentError("Data is too long. Max = $maxLength");
if (data.length == maxLength) return data;
final StringBuffer buffer = StringBuffer(data);
for (int i = data.length; i < maxLength; i++) {
buffer.write(padCharacter);
}
return buffer.toString();
}