ej12.asm

format PE
entry main
section '.text' code readable executable

main:
  mov eax, [esp]
  xor edi, edi

  ; 32 bit -> 8 nibble
  ; valor inicial de la mascara
  xor edx, edx
  mov edx, $0000000F
bucle:
  mov ebx, eax

  ; desplaza la mascara
  and ebx, edx
  shl edx, 4

  ; corre el nible a la parte baja (bl)
  xor ecx, ecx
  lea ecx, [4 * edi]
  shr ebx, cl

  ; controla si es A-F o 0-9
  cmp ebx, 9
  jg  aefe

  ; del 0 al 9
  add ebx, 48
  jmp continua

aefe:
  sub ebx, 10
  add ebx, 97

continua:
  ; guarda en buffer el char
  mov byte[buffer+edi], bl

  ; increenta contador
  add edi, 1

  ; condicion salida
  cmp edi, 8
  jne bucle

termina:
  push buffer
  push _format_output
  call [printf]
  add  esp, 8

  push buffer
  push _format_input
  call [scanf]
  add  esp, 8

  ret

section '.data' data readable writeable

_format_input   db "%s",0
_format_output  db "%s",10,0

buffer          dd ?

section '.idata' data import readable

include "macro\import32.inc"
library msvcrt, "MSVCRT.DLL"
import msvcrt,\
       printf ,'printf',\
       scanf  ,'scanf',\
       exit   ,'exit'