Contributor: PAUL SOBOLIK
{
In answer to a fellow subscriber's request, I recently posted to this list a
Delphi Assembler procedure to reverse ShortStrings. After someone pointed out
to me in a private message that my routine was slower than his all-Pascal
alternative, I tried again, and managed to come up with an asm procedure that
actually has a (modest) speed advantage. It is presented below, in case
anyone else can use it.
--Paul Sobolik
}
procedure RevString3(var s: ShortString); assembler;
asm
push esi
push edi
mov esi,eax
mov edi,eax
xor eax,eax
lodsb
add edi,eax
dec edi
add eax,2
shr eax,2
mov ecx,eax
jecxz @@done
@@loop:
mov ax,[esi]
mov dx,[edi]
xchg al,ah
mov [edi],ax
sub edi,2
xchg dl,dh
mov [esi],dx
add esi,2
dec ecx
jnz @@loop
@@done:
pop edi
pop esi
end;