preprocess_file:
;hlt
        push    [memory_end]
        push    esi               ;keeps file name
        mov     al,2              ;seek mode = from eof
        xor     edx,edx           ;seek offs = 0
        call    lseek
        push    eax               ;keeps file size
        xor     al,al             ;seek mode = from head
        xor     edx,edx           ;seek offs = 0
        call    lseek
        pop     ecx               ;restores file size
        mov     edx,[memory_end]  ;HERE IT STARTS...
        dec     edx               
        mov     byte [edx],1Ah    ;stores some marker at pointer
        sub     edx,ecx           ;...POINTER - FILE SIZE
        jc      out_of_memory     ;...WILL IT EVER CARRY
                                  ;...SHOULD IT BE (EDX-EDI-1)-ECX ?