Whoops, looks like I've indeed mixed up my assembler. While the rep/repe/repnz can be used in conjunction with movs(b/w) it will not terminate on the z flag in

Whoops, looks like I've indeed mixed up my assembler. While the rep/repe/repnz can be used in conjunction with movs(b/w) it will not terminate on the z flag in the eflags register (so it won't stop if *esi == 0) but rather when ecx = 0. So ecx needs to contain the size of the string you want to move, and rep movsb does not use the zero flag.