[Dreami]

How does this wrapper and each variant connect together? I supposed he would include a pointer to the actual struct in the wrapper, but I just see payload (that I'm gonna assume needs to be written to that array with padding in the actual struct).

For me, a wrapper includes the original thing and just wraps stuff around it. How does this work here? May also be a question to the author, I suppose now...

[JoachimSchipper]

In this wrapper, the payload[] field holds an instance of either struct A or of struct B - that is, the wrapper is "prepended" to the actual data.