.intel_syntax noprefix

.section .data
INum:   .quad 12
DNum:   .quad 0
DBy:    .quad 1
Erg:    .quad 0
One:    .quad 1
Zero:   .quad 0

.section .bss
.lcomm output_buffer, 32

.section .text
.global _start

_start:
        mov rax, [rip + One]       # LDA One
        call print_number          # OUT

NEX:
        mov rax, [rip + INum]      # LDA INum
        mov [rip + DNum], rax      # STA DNum

        mov rax, [rip + DBy]       # LDA DBy
        add rax, [rip + One]       # ADD One
        mov [rip + DBy], rax       # STA DBy

        mov rax, [rip + INum]      # LDA INum
        sub rax, [rip + DBy]       # SUB DBy

        jns mod_loop               # BRP mod_loop
        jmp halt                   # HLT

mod_loop:
        mov rax, [rip + DNum]      # LDA DNum
        sub rax, [rip + DBy]       # SUB DBy
        mov [rip + DNum], rax      # STA DNum

        jz PRT                     # BRZ PRT
        jns mod_loop               # BRP mod_loop
        jmp NEX                    # BRA NEX

PRT:
        mov rax, [rip + DBy]       # LDA DBy
        call print_number          # OUT
        jmp NEX                    # BRA NEX

halt:
        mov rax, 60                # Linux exit syscall
        xor rdi, rdi               # Exit status 0
        syscall


# ------------------------------------------------------------
# print_number
#
# Input:
#   RAX = unsigned integer to print
#
# Output:
#   Number followed by a newline
# ------------------------------------------------------------
print_number:
        lea rsi, [rip + output_buffer + 31]
        mov byte ptr [rsi], 10     # Newline
        mov rcx, 1                 # Output length
        mov rbx, 10

.convert:
        xor rdx, rdx
        div rbx                    # RAX / 10; remainder in RDX
        add dl, '0'
        dec rsi
        mov [rsi], dl
        inc rcx

        test rax, rax
        jne .convert

        mov rax, 1                 # Linux write syscall
        mov rdi, 1                 # stdout
        mov rdx, rcx               # Number of bytes
        syscall
        ret