I want to convert an NSDecimalNumber to a byte array. Also, I do not want to use any library for that like BigInt, BInt, etc. 

I tried this one: 

```
static func toByteArray<T>(_ value: T) -> [UInt8] {
    var value = value
    return withUnsafeBytes(of: &value) { Array($0) }
}
let value =  NSDecimalNumber(string: "...")
let bytes = toByteArray(value.uint64Value)

```

If the number is not bigger than Uint64, it works great. But, what if it is, how can we convert it?