Working with 2-byte

[bbufa]

It's a PCSX2 game.

[ecx+4] (2 byte)
[ecx+6] (2 byte, too)
How can I do something like this: [ecx+6] = [ecx+4] * 10, using CE script?

Thank you.

[Rhark]

Might help to explain yourself better, I can't seem to see what you are asking to do.

[bbufa]

Might help to explain yourself better, I can't seem to see what you are asking to do.

For example, the ecx register is something like this:

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02   1C   42   32   21   00   39   00 ...

I want to get [ecx+4] (only 2 byte): 21 00

multiply 21 00 with 10, result: XX XX

Place result to [ecx+6]

So in the end the ecx should be:

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02   1C   42   32   21   00   XX   XX ...

[TheByteSize]

Assuming 10 is integer value.

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push eax  //save eax
xor eax,eax
mov eax,word ptr [ecx+4]
imul eax,a  // or imul eax,#10 or imul eax,(int)10
mov word ptr [ecx+6], eax
pop eax   //recall eax

[Paul44]

^^ #TheByteSize is correct; the "key" thing here is that you use 'word ptr' to collect/manipulate 2 byte info (see also: byte ptr, dword ptr, etc ~ google). for completeness sake, you also might want to work with - in this case - ax...
(seems cleaner, but i always debug it just to make sure )

[bbufa]

Assuming 10 is integer value.

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push eax  //save eax
xor eax,eax
mov eax,word ptr [ecx+4]
imul eax,a  // or imul eax,#10 or imul eax,(int)10
mov word ptr [ecx+6], eax
pop eax   //recall eax

CE warns me:

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Not all code is injectable.
(Error in line 21 (mov eax,word ptr [ecx+4]): This instruction can't be compiled)
Are you sure you want to edit it to this?

[Rhark]

CE warns me:

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Not all code is injectable.
(Error in line 21 (mov eax,word ptr [ecx+4]): This instruction can't be compiled)
Are you sure you want to edit it to this?

Try this:

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push eax  //save eax
xor eax,eax
movzx ax,word ptr [ecx+4]
imul ax,#10
mov word ptr [ecx+6], ax
pop eax   //recall eax

[bbufa]

CE warns me:

Code: Select all

Not all code is injectable.
(Error in line 21 (mov eax,word ptr [ecx+4]): This instruction can't be compiled)
Are you sure you want to edit it to this?

Try this:

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push eax  //save eax
xor eax,eax
movzx ax,word ptr [ecx+4]
imul ax,#10
mov word ptr [ecx+6], ax
pop eax   //recall eax

Line

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movzx ax,word ptr [ecx+4]

get the same warning as above

[Rhark]

Line

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movzx ax,word ptr [ecx+4]

get the same warning as above

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push eax  //save eax
xor eax,eax
movzx eax,word ptr [ecx+4]
imul ax,#10
mov [ecx+6], ax
pop eax   //recall eax

Sorry, had a brain fart.

[bbufa]

Line

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movzx ax,word ptr [ecx+4]

get the same warning as above

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push eax  //save eax
xor eax,eax
movzx eax,word ptr [ecx+4]
imul ax,#10
mov [ecx+6], ax
pop eax   //recall eax

Sorry, had a brain fart.

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push eax  //save eax            (1)
xor eax,eax      //             (2)
movzx eax,word ptr [ecx+4]  //  (3)
imul ax,#10           //        (4)
mov [ecx+6], ax        //       (5)
pop eax   //recall eax          (6)

Now line (3) works, thank you.
But line (4) & (5), I think it is eax instead of ax?
Line (5) seems to be problem because: after (2), eax will be cleaned... After (3), except 2 first bytes of eax, the rest are 00 bytes, so eax looks like XX XX 00 00 00 00... In that case, line (5) mov the whole eax to [ecx+6] may replace a lot of bytes in ecx with 00?
Can we use "word ptr" in line (5)?

[Rhark]

[Link]

[bbufa]

[Link]

Thank you, after reading many times, I finally understand movzx command

However, the code

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imul ax,#10

still causes warning "this instruction can't be compiled".
I tried creating a new script (which has nothing to do with above codes and has only 1 imul code), just to test imul command:

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newmem:
  imul ax,#10

this new script can't be compiled either.
Could you please have a look.

[TheByteSize]

This should works.
Also remember that you're converting from 4 bytes into 2 bytes so you might get negative number in game.
if that the case, you will need to add number limit to 32767 before storing it back into pointer.

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push eax  
xor eax,eax
movzx eax,word ptr [ecx+4]
imul eax,#10  
mov word ptr [ecx+6], ax
pop eax  

[bbufa]

This should works.
Also remember that you're converting from 4 bytes into 2 bytes so you might get negative number in game.
if that the case, you will need to add number limit to 32767 before storing it back into pointer.

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push eax  
xor eax,eax
movzx eax,word ptr [ecx+4]
imul eax,#10  
mov word ptr [ecx+6], ax
pop eax  

I tested these codes dozen times, so far there is no problem.
Just in case bad things happen (negative number), could you please teach me how to fix it?

Thank you so much sirs

[TheByteSize]

Here you going to see couple push and pop. When you have multiple of these, remember the concept of First In/Last Out or Last In/First Out.
If you mess up the order, your game data could get wrong saved value in long run as worst case scenario. Immediately crash is better in this situation.
Also, we're going to use comparison in this so it's good idea to save the Flag(comparison result) stack and recall it.

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pushf   //saving flag stack
push eax 
push ebx 
xor eax,eax
xor ebx,ebx
mov ebx,#9999
movzx eax,word ptr [ecx+4]
imul eax,#10  
cmp eax,ebx
cmovg eax,ebx   //copy data of ebx to eax if eax is greater than ebx by the comparison line above.
mov word ptr [ecx+6], ax
pop ebx
pop eax 
popf    //recall flag stack