2025aoc1.asm

default rel

section .data
    filename: db "input.txt", 0

section .bss
    char:      resq 1
    number_string: resq 32
    number:    resq 1
    isL:       resq 1
    password1: resq 1
    password2: resq 1
    dial:      resq 1

section .text
    global _main

; read_number() => [rel char]
read_char:
    mov     rax, 0x2000003    ; read
    mov     rdi, r15          ; fd
    lea     rsi, [rel char]
    mov     rdx, 1
    syscall
    ret

; read_number() => r14
read_number:
    xor r14, r14
.loop:
    call read_char
    cmp  al, 0
    je   .done
    
    ; if (char < '0' || char > '9') return
    movzx rbx, byte [rel char]
    cmp   bl, '0'
    jb    .done
    cmp   bl, '9'
    ja    .done

    ; number = (char - '0') + number * 10
    imul r14, r14, 10
    sub  bl, '0'
    add  r14, rbx

    jmp .loop
.done:
    ret

; print_number(c: [rel char])
print_char:
    push rax
    push rdi
    push rsi
    push rdx
    mov     rax, 0x2000004    ; write
    mov     rdi, 1            ; stdout
    lea     rsi, [rel char]
    mov     rdx, 1
    syscall
    pop rax
    pop rdi
    pop rsi
    pop rdx
    ret

; print_number(num: r14)
print_number:
    push r14

    cmp r14, 0
    jge .skip_negative
    mov byte [char], '-'
    call print_char
    neg r14
.skip_negative:

    cmp r14, 0
    jne .skip_zero
    mov byte [char], '0'
    call print_char

    pop r14
    ret
.skip_zero:

    mov rax, r14

    lea rcx, [rel number_string]
    lea r8,  [rcx + 32]
    mov rsi, r8
    mov rbx, 10
    
.buff_loop:
    cmp rax, 0
    je  .buff_end

    cqo
    idiv rbx
    add  dl, '0'
    dec  rsi
    mov  [rsi], dl

    jmp .buff_loop
.buff_end:
    mov rdx, r8
    sub rdx, rsi
    
    mov rax, 0x2000004    ; write
    mov rdi, 1            ; stdout
    syscall

    pop r14
    ret

print_newline:
    mov   byte [char], 10
    call  print_char
    ret

handle_r:
    xor rcx, rcx
.loop:
    cmp rax, 0
    je .done

    inc rbx
    dec rax

    cmp rbx, 100
    jne .loop

    mov rbx, 0
    inc rcx

    jmp .loop
.done:
    ret

handle_l:
    xor rcx, rcx
.loop:
    cmp rax, 0
    je .done

    dec rbx
    dec rax

    cmp rbx, 0
    jne .continue
    inc rcx
.continue:
    cmp rbx, 0
    jge .loop
    mov rbx, 99

    jmp .loop
.done:
    ret



_main:
    mov     rax, 0x2000005
    lea     rdi, [rel filename]
    xor     rsi, rsi
    xor     rdx, rdx
    syscall
    mov     r15, rax        ; r15 = fd

    mov [rel dial], 50
    mov [rel password1], 0
    mov [rel password2], 0

.read_loop:
    ; while (char = read(fd, 1)) {
    call    read_char
    cmp     rax, 0
    je      .done
    
    cmp     byte [rel char], 'L'
    sete    byte [rel isL]

    ; call    print_char
    call    read_number
    ; call    print_number

    mov rax, r14
    mov rbx, [rel dial]
    
    cmp [rel isL], 1
    jne .R
    call handle_l
    jmp .continue
.R:
    call handle_r
.continue:

    mov [rel dial], rbx
        
    mov rax, [rel password2]
    add rax, rcx
    mov [rel password2], rax

   ; mov [rel char], ' '
   ; call print_char

    mov    r14, [rel dial]
   ; call   print_number
   ; call   print_newline

    cmp    [rel dial], 0
    jne    .read_loop
    mov    eax, [rel password1]
    inc    eax
    mov    [rel password1], eax

    jmp    .read_loop

.done:
    mov     r14, [rel password1]
    call    print_number
    call    print_newline

    mov     r14, [rel password2]
    call    print_number
    call    print_newline

    mov     rax, 0x2000006     ; close(fd)
    mov     rdi, r15
    syscall

    mov     rax, 0x2000001     ; exit(0)
    xor     rdi, rdi
    syscall

run.sh

nasm -fmacho64 hello.asm -o hello.o
clang -arch x86_64 -mmacosx-version-min=10.13 hello.o -o hello
arch -x86_64 ./hello
# time arch -x86_64 ./hello