format ELF64
section '.data'

strUsage: 
    db 'program filename -o filename', 0x00



section '.text' executable

extrn 'puts' as _puts
puts = PLT _puts

public main
main:
    ; rdi is count of arguments
    ; rsi **arg
    dec rdi
    jz .usageInfo
    mov rbx, 0x01
 
    
.getNextArg:
    ; save the registers 
    push rdi
    push rsi
    push rbx
    sub rsp, 24
    
    mov rdx, [rsi+rbx*8]    ;move current argument into rdx
    mov al, byte[rdx]       ;move first two to ax and switch option pointed at
;    cmp al, '-'  ; this is where the segmentation fault occurs.. which means it is not cleanly formed
;    je ProcessArg  ;it is the jump not the compare after further checking...
    cmp byte[rdx], 0x00
    je .toNextArg
    mov rdi, rdx
    call puts
    
    add rsp, 24
    pop rbx
    pop rsi
    pop rdi
    
;    add rsi, 0x08
.toNextArg:
    inc rbx
    dec rdi
    jnz .getNextArg
    jmp .exit
  
.usageInfo:
    push rdi
    push rsi
    sub rsp, 16
    
    mov rdi, strUsage
    call puts
    
    add rsp, 16
    pop rsi
    pop rdi
    
.exit:
    xor rax, rax
    ret

ProcessArg:
    push rcx
    push rbx
    push rdi
    push rsi
    sub rsp, 32
    
    mov ax, word[rdx]
    mov di, ax
    call puts
    
    add rsp, 32
    pop rsi
    pop rdi
    pop rbx
    pop rcx
    ret
    

    sub rsp, 0x0C  ;<--- not a multiple of 8 bytes