asm double of nr

; Program to read a number and print its double
section .data
    prompt db "Enter a number: ", 0
    prompt_len equ $ - prompt
    result db "Double of the number is: ", 0
    result_len equ $ - result
    newline db 10, 0

section .bss
    num resb 32    ; Buffer to store input string
    output resb 32 ; Buffer to store output string

section .text
    global _start

_start:
    ; Print prompt
    mov rax, 1          ; sys_write
    mov rdi, 1          ; stdout
    mov rsi, prompt     ; message to write
    mov rdx, prompt_len ; message length
    syscall

    ; Read input
    mov rax, 0          ; sys_read
    mov rdi, 0          ; stdin
    mov rsi, num        ; buffer
    mov rdx, 32         ; buffer size
    syscall

    ; Convert string to integer using atoi
    mov rdi, num        ; number string to convert
    call atoi           ; call our atoi function

    ; Double the number
    add rax, rax        ; multiply by 2

    ; Convert integer back to string
    mov rdi, output     ; output buffer
    mov rsi, rax        ; number to convert
    call itoa           ; call our itoa function

    ; Print result message
    mov rax, 1          ; sys_write
    mov rdi, 1          ; stdout
    mov rsi, result     ; message
    mov rdx, result_len ; length
    syscall

    ; Print the doubled number
    mov rax, 1          ; sys_write
    mov rdi, 1          ; stdout
    mov rsi, output     ; converted number string
    mov rdx, 32         ; max length
    syscall

    ; Print newline
    mov rax, 1
    mov rdi, 1
    mov rsi, newline
    mov rdx, 1
    syscall

    ; Exit
    mov rax, 60         ; sys_exit
    mov rdi, 0          ; exit code 0
    syscall

; Function to convert ASCII string to integer (atoi)
atoi:
    xor rax, rax        ; zero out rax
    xor rcx, rcx        ; zero out rcx
.loop:
    movzx rdx, byte [rdi + rcx] ; get current char
    cmp dl, 0xa         ; check for newline
    je .done
    cmp dl, 0           ; check for null terminator
    je .done

    sub dl, '0'         ; convert ASCII to number
    imul rax, 10        ; multiply current result by 10
    add rax, rdx        ; add new digit

    inc rcx             ; move to next char
    jmp .loop
.done:
    ret

; Function to convert integer to ASCII string (itoa)
itoa:
    push rbp
    mov rbp, rsp
    sub rsp, 32         ; allocate stack space

    mov rax, rsi        ; number to convert
    mov rcx, 0          ; digit counter
    mov r8, 10          ; divisor

.divide_loop:
    xor rdx, rdx        ; clear remainder
    div r8              ; divide by 10
    add dl, '0'         ; convert to ASCII
    push rdx            ; save digit
    inc rcx             ; increment counter
    test rax, rax       ; check if done
    jnz .divide_loop

.build_string:
    mov rdx, rcx        ; save length
.digit_loop:
    pop rax             ; get digit
    mov [rdi], al       ; store in buffer
    inc rdi             ; next position
    loop .digit_loop

    mov byte [rdi], 0   ; null terminate

    mov rsp, rbp
    pop rbp
    ret