Optimize this code?

[cblake]

Also, you can do what the C preprocessor calls "token pasting" within some back 
quotes in Nim. Basically concatenating parts of a name into a whole name. See 
[this part of the 
manual](https://nim-lang.org/docs/manual.html#templates-identifier-construction).
 If one of the ways you "multiply up" to 256 is varying that "key" part this 
could help, and you might even be able to "nest" template expansions to do such 
more cleanly.