decodeBase64 function
Implementation
String decodeBase64(String input) {
final Base64Decoder base64Decoder = Base64Decoder();
final int difference = input.length % 4;
if (difference != 0) {
return String.fromCharCodes(
base64Decoder.convert(input + "=" * (4 - difference)));
}
return String.fromCharCodes(base64Decoder.convert(input));
}