The functionality that I am personally interested in from a binary parsing framework like Kaitai is generating an encoder implementation in addition to a decoder one. In other words, given a description of a binary format, I would like to be able to construct an instance of a class whose memory layout matches the format. For instance, if the format has an int n, then an array `a` of size `n`, and then a double `d`, it would be awesome to be able to construct a corresponding object with fields `n`, `a` and `d` and when I change `n`, then the size of `a` changes accordingly. And then, if I pass a pointer to this object to the decoder, it would be able to parse it correctly, as if the memory representation of the object came from some external buffer.