advent_of_code_2024_asm/main.asm

  default rel
  extern printf

  global exitcode

  section .data
buf: dq 0
dbuf: dw 0
path:  db "./input.txt", 0
nb_lines: dw 1000

fmt:  db "Value %s: %d", 10, 0

fd_str:  db "file descriptor", 0
close_str:  db "close", 0
content_str:  db "Content: '%s'", 10, 0
nbr_str:  db "number", 0

exitcode: dw 0



  section .text

  global _start


printvalue:
  push rbp
  mov rbp, rsp
  sub rsp, 8H

  ;; args
  mov dword [rbp-8H], edi
  mov dword [rbp-4H], esi

  ;; printf
  xor rax, rax
  lea rdi, [fmt]                ; format
  mov esi, dword [rbp-8H]       ; arg1
  mov edx, dword [rbp-4H]       ; arg2
  call printf

  ;; leave
  mov rsp, rbp
  pop rbp
  ret
;; End of printvalue

readval:
  ;; rdi: FILE DESCRIPTOR
  ;; rsi: offset

  push rbp
  mov rbp, rsp
  sub rsp, 16H

  mov qword [rbp-8H], rsi
  mov qword [rbp-16H], rdi

  ;; sys_read
  mov rax, 0                    ; sys_read
  ;; rdi has already file descriptor
  mov rdi, qword [rbp-16H]
  mov rsi, buf
  mov rdx, 5H
  syscall

  ;; Go to the next number
  mov rax, 8                    ; sys_lseek
  mov rdi, qword [rbp-16H]      ; fd
  mov rsi, qword [rbp-8H]       ; advance by n chars
  mov rdx, 1                    ; origin
  syscall

  ;; convert buf to an int
  xor ebx, ebx
  mov esi, buf
  mov ecx, 5

  .next_digit:
  movzx eax, byte [esi]
  inc rsi
  sub al, '0'                   ; convert ascii to number (remove offset of the 0 digit)
  imul ebx, 10
  add ebx, eax                  ; rbx = rbx*10 + rax
  loop .next_digit              ; loop until ecx = 0

  xor rax, rax
  mov eax, ebx

  mov rsp, rbp
  pop rbp
  ret
;; end of readval1


_start:
  push rbp
  mov rbp, rsp
  sub rsp, 2000H

  ;; 8H -> 0 : file_descriptor
  ;; 12H -> 8H : buffer for readvalue
  ;; 14H -> 12H : current line
  ;; 19H -> 17H: read loop counter
  ;; 2000H -> 1060H : list 1 (1000 digits of 4 bytes)
  ;; 1000H -> 60H : list 2


  mov rax, 2                    ; sys_open
  lea rdi, [path]
  xor rsi, rsi
  xor rdx, rdx
  syscall

  ;; store file descriptor
  mov qword [rbp-8H], rax

  ;; print file descriptor
  lea rdi, [fd_str]
  mov rsi, rax
  call printvalue

  ;; exit if open failed
  cmp dword [rbp-8H], 0
  jl exit

  mov word [rbp-14H], 0H         ; line number

  mov cx, [nb_lines]            ; number of lines
loop:
  mov [rbp-19H], cx             ; store loop counter

  ;; read the 1st value
  mov rdi, qword [rbp-8H]
  mov rsi, 3H                   ; mov to the second number
  call readval

  ; store the read value
  mov [dbuf], eax

  ;; calculate list position
  xor rax, rax
  mov ax, word [rbp-14H]
  mov bx, 2H
  mul bx
  ;; 14H -> 12H : line counter
  mov rbx, 2000H
  sub rbx, rax
  mov r9, rbp
  sub r9, rbx

  ; move the value to its position
  mov eax, [dbuf]
  mov dword [r9], eax

  ;; read the 2nd value
  mov rdi, qword [rbp-8H]
  mov rsi, 1H                   ; mov to the next line
  call readval

  ; store the read value
  mov [dbuf], eax

  ;; calculate list position
  xor rax, rax
  mov ax, word [rbp-14H]
  mov bx, 4H
  mul bx
  mov rbx, 1000H
  sub rbx, rax
  mov r9, rbp
  sub r9, rbx

  ; move the value to its position
  mov eax, [dbuf]
  mov dword [r9], eax

  xor rax, rax
  mov ax, word [rbp-14H]
  inc ax
  mov word [rbp-14H], ax

  mov cx, [rbp-19H]             ; restore loop counter
  dec cx
  jnz loop

  ;; print values

  mov word [rbp-14H], 0         ; line number
  xor ecx, ecx
  mov ecx, 2024                 ; There are 24 dword between address 1060H and 1000H

  .loop:
  mov [rbp-19H], cx             ; store loop counter

  ;; calculate list 1 position
  xor rax, rax
  mov ax, word [rbp-14H]
  mov bx, 4H
  mul bx
  mov rbx, 2000H
  sub rbx, rax
  mov r9, rbp
  sub r9, rbx

  ; move the value to its position
  lea rdi, [nbr_str]
  mov esi, dword [r9]
  call printvalue

  inc word [rbp-14H]

  mov cx, [rbp-19H]
  loop .loop


close_file:
  ;; sys_close
  mov rax, 3                    ; sys_close
  mov edi, dword [rbp-8H]
  syscall

  ;; print sys_close result
  lea rdi, [close_str]
  mov rsi, rax
  call printvalue


exit:
  ;; EXIT
  mov rax, 60                   ; sys_exit
  mov rdi, [exitcode]
  syscall