isBase64 function
check if a string input
is base64 encoded
Implementation
bool isBase64(String input) {
if (input != null && input.length % 4 != 0 || _regExp.hasMatch(input)) {
return false;
}
var firstPaddingChar = input.indexOf("=");
return firstPaddingChar == -1 ||
firstPaddingChar == input.length - 1 ||
(firstPaddingChar == input.length - 2 && input[input.length - 1] == '=');
}