Ïðîãðàììèðîâàíèå íà Àññåìáëåðå
6.2.2 Êîìàíäû óñëîâíîãî ïåðåõîäà - ÷àñòü 2
Mov eax, [X]
Cmp eax, [Y]
Jae mx
My:
Mov eax, [Y]
Mov [Z], eax
Mov eax, [Y+4]
Mov [Z+4], eax
Jmp short m1
Mx:
Mov eax, [X]
Mov [X], eax
Mov eax, [X+4]
Mov [X+4], eax
M1:
Ïðèìåð 3.
Ñêîïèðîâàòü äàííûå èç îäíîé îáëàñòè ïàìÿòè â äðóãóþ, åñëè çàäàíû àäðåñà îáåèõ îáëàñòåé è ðàçìåð
Addr1 dd …
Addr2 dd …
Len dd …
Ñïîñîá 1
Mov eax, [addr1]
Mov edx, eax
Add edx, [len]
Mov ebx, [addr2]
For1:
Mov cl, [eax]
Mov [ebx], cl
Inc eax
Inc ebx
Cmp eax, edx
Jle for1
…
Îøèáêà!: êîìàíäó Jle íåîáõîäèìî çàìåíèòü êîìàíäîé äëÿ ñðàâíåíèÿ ÷èñåë áåç çíàêà! (Jbe).
Íåäîñòàòîê ðåøåíèÿ! Íå ó÷òåíî âîçìîæíîå ïåðåêðûòèå îáëàñòåé!
Ñïîñîá 2
Ab = addr1; h = 1; Be = addr2;
If (addr2 != addr1){
If (addr2 > addr1 && addr2 < addr1+len){
Ab += len – 1; Bb +=len – 1;
H=-1;
}
for (i=0; i<len; i++){
*Bb = *Ab
bb+=h;
aa+=h;
}
;Ab = addr1; h = 1; Be = addr2;
mov eax, [addr1]
mov ebx, [addr2]
mov edx, 1
;If (addr2 != addr1){
cmp eax, ebx
je short break
; If (addr2 > addr1 && addr2 < addr1+len){
cmp eax, ebx
jbe m1
mov ecx, eax
add ecx, [len]
cmp ebx, ecx
jae m1
;Ab += len – 1; Bb += len – 1; H=-1;
mov eax, ecx
dec eax
add ebx, [len]
dec ebx
mov edx, -1
;}
;for (i=0; i<len; i++){ *Bb = *Ab; bb+=h; aa+=h;
mov esi, [len]
for2:
mov cl, [eax]
mov [ebx], cl
add eax, edx
add ebx, edx
sub esi, 1
jnz for2
