rex-nop

https://github.com/rapid7/rex-nop

This library contains the opty2 library for dynamic generation of x86 multi-byte NOPs. This is useful in writing exploits and encoders. It allows you to dynamic generate variable length instruction sets that are equivalent to a No Operation(NOP) without using the actual 0x90 bytecode. The original code was written by Optyx and spoonm.