zombie-lib/atoi.asm

extern libz_strlen

global libz_atoi

section .text

libz_atoi:


;	mov r11, rdi	;saveing it for later

	push rdi
	call libz_strlen
	mov r9, rax
	pop rdi

	xor r10, r10

	mov rcx, 1
	add r9, rdi
	dec r9

_loop:

	xor rax, rax
	mov al, [r9]

	cmp rax, 48
	jb _nan
	cmp rax, 57 ;if its not a number then return 0 then exit
	ja _nan

;	push rax
	sub rax, 48
	mul rcx
	add r10, rax
;	pop rax

	cmp r9, rdi
	je _end
	dec r9
;	push rax
	mov rax, 10
	mul rcx
	mov rcx, rax
;	pop rax

	jmp _loop

_nan:
	xor r10, r10

_end:
	mov rax, r10
	ret