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Index > Linux > Increasing offset whilst reading/writing

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andyz74



Joined: 26 Nov 2007
Posts: 36
Location: Germany
andyz74
Hello, it's me again, the noob. :-/

I tried to copy content bitwise from one "array" to another, by increasing the offset of the array, but i got no working version. Sad

As an example, I have...

Code:
  sub [zeugs],18h
     sub [zeugs+1],18h
   sub [zeugs+2],18h
   sub [zeugs+3],18h
   sub [zeugs+4],18h
   sub [zeugs+5],18h
   sub [zeugs+6],18h
   sub [zeugs+7],18h
   sub [zeugs+8],18h
   sub [zeugs+9],18h
   sub [zeugs+10],18h
    

...where U can see, that the increasing of the offset was done by hand ( +1 +2 +3) and so on...
If I do sth like

Code:
    sub [zeugs+cl],18h
    

with "cl" being increased automatically, i get some error by the compiler.

So how can I get a workaround for this problem? Anybody could help me please with this?
Post 17 Oct 2010, 16:27
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
Location: Argentina
LocoDelAssembly
Since you posted in Linux, you need 32-bit addresses, therefore you need to use ECX instead of just CL (lower 8 bits of ECX).

For your first code you could do this:
Code:
mov ecx, 0

.loop:
  mov byte [zeugs+ecx], 18h
  inc ecx
  cmp ecx, 10
  jbe .loop    

And to copy one array into another:
Code:
mov ecx, 0
mov edi, dstArray
mov esi, srcArray
.loop:
  mov al, [srcArray+ecx]
  mov [dstArray+ecx], al
  inc ecx
  cmp ecx, srcArraySize
  jb .loop    

Or just:
Code:
mov ecx, srcArraySize
mov edi, dstArray
mov esi, srcArray
rep movs byte[edi], byte[esi]    
In all cases I'm been working with byte arrays.
Post 17 Oct 2010, 17:05
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andyz74



Joined: 26 Nov 2007
Posts: 36
Location: Germany
andyz74
OK, this seems to work with the 32-bit-registers. No more compilation-errors.

Many thanks for the fast help! Smile
Post 17 Oct 2010, 18:04
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