Does this tool exist?

I recently found myself binary-editing a shared library to NOP out some code in order to test a theory about the cause of a crash. In this case I had the source available but this was a quicker approach than rebuilding; in other cases I might not have the source.

What I actually did was read a disassembly, figure out what addresses I needed to change, and then use tweak to edit it.

The ideal tool for the job, though, would have been one that displayed the disassembly and let me drag out a region and replace with it a new sequence of instructions, with an error if they were too long and NOP-filling if they were short, and with warnings if I was disrupting a branch target. You can probably imagine other nice features.

Anyway, does anyone know if such a tool exists?

I think I’ve spent more time reading and writing assembler in the last year than the entire preceding decade. Funny how things turn out.