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   comp.lang.asm.x86      Ahh, the lost art of x86 assembly      4,675 messages   

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   Message 2,789 of 4,675   
   Kerr Mudd-John to All   
   BASE64 again   
   05 Jul 17 10:08:05   
   
   From: admin@nospicedham.127.0.0.1   
      
   (may not thread)   
   WK wrote:   
      
   ...   
   146 sub ax,6d3b    ;92c5 xor 3636 = A4F3   
   149 xor [bx+24],ax ;create REP MOVS   
      
   I presume al=c5 here   
      
    14c sub al,21      ;c5-21=a4   
    14d inc ax  dup2   ;a6 xor 65 = c3   
   shorter:   
        xor al,63 ; c5->a6   
      
   14f xor [bx+7e],al ;create a RET in a field of 65 nops   
   ...   
      
      
   setting cx for my b64 decoder:   
   shorter to set dl earlier (where you set dh) (;it's not used elsewhere) to x6   
   where x is one of {3,4,5,6,7}   
   then push dx, pop cx before the entering; the "and cx,6" will scrap the other   
   values.   
      
      
      
   --   
   Bah, and indeed, Humbug   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)   

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