I could foresee a Rust one outperforming a C++ one to be honest, but I doubt the current pure-rust libraries would at this time (though still plenty fast).
Sure, I’ll clean it up and PR it into a cpp/rapidjson directory or something. 
Do you want a readme.md or INSTALL file in that directory, or do you want me to edit the root readme to add instructions on how to compile/run it?
I was thinking of adding a statistical benchmarker to the C++ version instead of just using time, do you want me to do that pre-PR?
