See https://docs.google.com/document/d/1C5b81g0W6th5Ti5P6nlWrjc2qsR8I6sTFuy0bYumOfI/edit?usp=sharing

I have now coded up and tested both wrap and unwrap. The exercise resulted in some refinement of the interface of the new functions. It turns out that x_iovcount and x_fillbufs with minor tweaks are useful in the unwrap side also.

Code to follow soon…

Frank