%include "MY_IO.h"

global PRINT_HELLO
global DOUBLE_NUMBER
global DOUBLE_IN_PLACE
global FILL_ARRAY

section .data
   HELLO_STRING db `Hello from Assembly!\n`,0
   helloLen equ $ - HELLO_STRING

section .text

PRINT_HELLO:
    push rbp
    mov rbp, rsp

    mov rdi, HELLO_STRING
    mov rsi, helloLen
    call PRINT_STRING

    pop rbp
    ret

; rdi holds the number
; return value in rax
DOUBLE_NUMBER:

    mov rax, rdi
    add rax, rax
    ret

; rdi holds the address of the number;
; at first I was u sing r8, but crashed on return
; I was over writing memory that was not part of the variable.
DOUBLE_IN_PLACE:
    mov r8d, DWORD [rdi]
    add r8d, r8d
    mov DWORD [rdi], r8d
    ret

; rdi holds the address of the array
; rsi holds the size of the array
; rdx holds the fill value
FILL_ARRAY:
    push rbp
    mov rbp, rsp
    push r15 ; lcv
    push r14 ; offset

    mov r15, 0
    mov r14, 0
.top:
    cmp r15, rsi
    je  .done

    mov [rdi+r14], rdx

    add r14, 4
    inc r15
    jmp .top
.done:

    pop r14
    pop r15
    pop rbp
    ret