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|
; **************************************************************************** ;
; ;
; ::: :::::::: ;
; ft_strcmp.s :+: :+: :+: ;
; +:+ +:+ +:+ ;
; By: cacharle <marvin@42.fr> +;+ +:+ +;+ ;
; +;+;+;+;+;+ +;+ ;
; Created: 2019/11/23 00:17:19 by cacharle ;+; ;+; ;
; Updated: 2019/11/23 00:17:19 by cacharle ;;; ;;;;;;;;.fr ;
; ;
; **************************************************************************** ;
%ifdef __LINUX__
%define M_FT_STRCMP ft_strcmp
%else
%define M_FT_STRCMP _ft_strcmp
%endif
global M_FT_STRCMP
section .text
; int ft_strcmp(const char *s1, const char *s2);
M_FT_STRCMP:
push r12
push r13
push rcx
mov r12, rdi ; s1
mov r13, rsi ; s2
mov rcx, -1 ; index
FT_STRCMP_LOOP:
inc rcx
cmp byte [r12 + rcx], 0 ; check and of s1
je FT_STRCMP_LOOP_END
mov dl, byte [r12 + rcx]
cmp dl, byte [r13 + rcx] ; s1[rcx] == s2[rcx]
je FT_STRCMP_LOOP
FT_STRCMP_LOOP_END:
xor rax, rax
mov al, byte [r12 + rcx]
sub al, byte [r13 + rcx]
jnc FT_STRCMP_END ; jump end if no substraction overflow
neg al ; negate al to cancel overflow
neg eax ; negate the whole int since the function returns that type
FT_STRCMP_END:
pop rcx
pop r13
pop r12
ret
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