Manual String Length function in NASM

strlen.asm

%if 0 
 * Title: Manual String Length function
 * Author: Osanda Malith (@OsandaMalith)
 * Website: https://osandamalith.com
%endif 

global _start

section .text

_start:

  mov edi, message
  call _strlen
  mov edx, eax

  mov eax, 0x4
  mov ebx, 0x1
  mov ecx, message
  int 0x80

  mov eax, 0x1
  mov ebx, 0x5
  int 0x80

_strlen:

  push ebx
  push ecx

  mov   ebx, edi            
  xor   al, al                               
  mov   ecx, 0xffffffff     
                                                     
  repne scasb               ; REPeat while Not Equal [edi] != al

  sub   edi, ebx            ; length = offset of (edi - ebx)
  mov   eax, edi            

  pop ebx
  pop ecx
  ret                       

section .data

  message: db "https://osandamalith.com", 0xa