Jump Tables Effectiveness

[zemtex]

A much more delicate way to do it is to use (OFFSET JmpTable-4) so that the calculation is done at assembly time. When you use [-4] in brackets, the calculation is done at execution time and will waste cycles.

This will calculate at runtime: call switches[4*ebx-4]

This (The subtraction part) will calculate at assembly time: lea ecx, [4*ecx+(OFFSET JmpTable-4)]

It is a much more delicate way to do it.

EDIT: I tried it in olly, it seems like your solution calculated at assembly time after all. Then it would be the same.

FF149D FC3FEC00   CALL DWORD PTR DS:[EBX*4+0EC3FFC]

and here is mine:

8D0C8D FC3FEC00   LEA ECX,[ECX*4+0EC3FFC]

Can never be too careful  :P

[jj2007]

EDIT: I tried it in olly, it seems like your solution calculated at assembly time after all. Then it would be the same.

Yes indeed :bg