fillBytes function
Implementation
List<int> fillBytes(BigInt v, int len) {
List<int> result = List.filled(len, 0);
int bytes = (v.bitLength + 7) >> 3;
var b256 = BigInt.from(256);
var offset = len - 1;
for (int i = 0; i < bytes; i++) {
result[offset] = v.remainder(b256).toInt();
v = v >> 8;
offset--;
}
return result;
}