hakers.info

This problem statement is part of binary-auditing package. This needs

to be converted to HLL

Problem:(Assembly code)

sub_408138 proc near
000 push ebx
004 push esi
008 mov esi, edx
008 dec esi
008 test esi, esi
008 jl short loc_40816F
008 inc esi
loc_408142:
008 xor edx, edx
008 mov dl, [eax]
008 xor ebx, ebx
008 mov bl, cl
008 add edx, ebx
008 test edx, edx
008 jge short loc_40815B
008 mov ebx, 100h
008 sub ebx, edx
008 mov edx, ebx
008 jmp short loc_408169
loc_40815B:
008 cmp edx, 100h
008 jle short loc_408169
008 sub edx, 100h
loc_408169:
008 mov [eax], dl
008 inc eax
008 dec esi
008 jnz short loc_408142
loc_40816F:
008 pop esi
004 pop ebx
000 retn
sub_408138 endp

 

Pseudo/High Level code:
var_esi = var_edx;
var_esi -- ;

if(var_esi >=0)
var_esi++;

do
{
var_edx=0;
LOWER byte of EDX=*var_eax;  //EAX supplied from outside

var_ebx=0;
LOWER byte of EBX=LOWER byte of ECX;  //ECX supplied from outside

var_edx=var_edx+var_ebx;

if(var_edx<0)
{
var_ebx=100h;   //256
var_ebx=var_ebx-var_edx;
var_edx=var_ebx;
}
else
{
if(var_edx>100h)
var_edx=var_edx-100h;
}

*var_eax=LOWER byte of EDX
var_eax++;
}while(--var_edx!=0)