get 3'th byte of eax?

[FastLife]

hello tuts4you, i tried to solve a keygenme and faced a problem.

 

the return value of a function is in example: eax == 00001234.

now i want the 3'th byte of it, which is 12.

 

so does anybody know a way to do this?

 

have a nice day!

[NOP]

The lowest 16 bits of EAX is AX

 

So...

AX = 1234

AL = 34

AH = 12

 

So just use AH

Edited August 24, 2014 by NOP

[simple]

C

void Main()

{

    int IntToParse = 4660; 0x00001234 = EAX = 32 bit integer
    // adjust this according to which bits you want. remember byte ordering

    int ParsePlace = 1;
    // bit shift, multiply, and

    int Parsed = ((IntToParse >> (8*ParsePlace)) & 0xFF);
    printf("Parsed = %i\n");

}

-----
Output - Parsed = 18 (12h)

x86 asm

IntToParse = 0x1234 ;
mov eax, IntToParse ;  int IntToParse = 0x1234
sar eax, 8 ; IntToParse >> 8
and eax, FF ; Result & FF. sometimes this step isnt necessary
eax == 12 

[h4sh3m]

x86 asm

IntToParse = 0x1234 ;mov eax, IntToParse ;  int IntToParse = 0x1234sar eax, 8 ; IntToParse >> 8and eax, FF ; Result & FF. sometimes this step isnt necessaryeax == 12 

Hi

 

easiest method for this problem (if we can call it problem !) is :

MOVZX EAX,AH

 

 

Best Regards,

h4sh3m

[simple]

i understand u (even though in this case a simple "sar eax, 8" works exactly same as "mov eax, ah") but way i showed is standard way to do this in high level language.

[FastLife]

So many replys, all are helpfull, thank you very much guys, problem solved!

[evlncrn8]

also, its 3rd.. not 3th

[mrexodia]

@evlncrn8: I smell some grammarnazism here

[evlncrn8]

sorta, but im just trying to help too

[FastLife]

well thanks for the tip