####### PROGRAM GLOWNY C #########

#include <stdio.h>

extern void szyfrCezara(char * text, int key);

char text[]="ZZZZaSHF";
int key = 54;
int textlen = 6;

int main() {

szyfrCezara(&text,key);

printf("Zaszyfrowany tekst: %s\n",text);

return 0;
}


####### FUNKCJA W ASM ##########

.data

.text
.global szyfrCezara
.type szyfrCezara, @function

szyfrCezara:

push %rbp
mov %rsp, %rbp

mov $0, %r8 /* licznik */
mov $26, %r9
mov %rsi, %rax

loop:

/* rdi - text, rax - klucz */

    mov (%rdi, %r8, 1), %bl
    cmp $65, %bl
    jl next
    cmp $90, %bl
    ja next
    cmp $26, %rsi
    ja modkey

    adding:
    add %al, %bl
    cmp $90, %bl
    ja bigkey
    mov %bl, (%rdi, %r8, 1)
    jmp next

    next:
    inc %r8
    cmp $3, %r8
    je end
    cmp $3, %r8
    jl loop

    modkey:
    mov $0, %rdx
    div %r9
    mov %rdx, %rax
    jmp adding

    bigkey:
    sub $26, %bl
    mov %bl, (%rdi, %r8, 1)
    jmp next

jl loop

end:
mov %rbp, %rsp
pop %rbp
ret