Output in a bit more true assembly, Assembly

Output in a bit more true assembly

;nasm 2.11.08

section .data
    theString1:     db 'Small example of using calls instead of waterfalling code',0Ah,00             ; String with linefeed(hex) and zero terminator
    theString2:     db 'This is the second string that is drawn by a call and NOT a newline!',10d,00  ; String with linefeed(dec) and zero terminator

section .text
	global _start

_start:
    push theString1
    call _lenght         ; No absolute values, just calculate the lenght of string
    
    push theString2
    call _lenght
    
	mov eax,1            ; The system call for exit (sys_exit)
	mov ebx,0            ; Exit with return code of 0 (no error)
	int 80h
    
_lenght:
    mov ecx,[rsp+8h]     ; retrieve argument from the stack
    xor edx,edx          ; lenght of string
    
    _loop:
    cmp byte [ecx],0     ; check for the terminator
    je _writeline        ; if true, write line
      inc ecx            ; address
      inc edx            ; lenght of string + 1
      jmp _loop

_writeline:
    sub ecx,edx          ; restore our offset by substracting lenght
	mov eax,4            ; The system call for write (sys_write)
	mov ebx,1            ; File descriptor 1 - standard output
	int 80h              ; Call the kernel
    ret 8                ; return and pop 8 bytes extra (push in 64 bit = 8 bytes)


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