99_bottles_of_beer_on_the_wall.asm

global _start

section .text
  _start:
    xor   ecx, ecx
    mov   cl, 0x63

    song:
      mov   eax, ecx
      call  convert_to_ascii

      push  eax
      push  ecx
      call  verse_part_one

      pop   ecx
      pop   eax
      push  ecx
      call  verse_part_two

      pop   ecx
      loop  song

      call  outro

      xor   eax, eax
      mov   al, 0x01
      xor   ebx, ebx
      int   0x80

    convert_to_ascii:
      push  ebp
      mov   ebp, esp

      ; divide number by 10
      xor   ebx, ebx
      mov   bl, 0xb
      sub   bl, 0x01
      div   bl

      ; normalise values into ASCII
      add   ah, 0x30
      add   al, 0x30

      ; remove leading zeros
      cmp   al, 0x30
      jnz   exit_convert_to_ascii
      xor   al, al

    exit_convert_to_ascii:
      leave
      ret

    verse_part_one:
      push  ebp
      mov   ebp, esp

      xor   ebx, ebx
      xor   edx, edx

      cmp   al, dl
      jnz   build_v1_string
      cmp   ah, 0x31
      jnz   build_v1_string
      mov   bl, 0x01

      build_v1_string:
      xor   ecx, ecx
      mov   cl, 0xb
      sub   cl, 0x01
      push  cx
      push  0x2e726565
      push  0x6220666f
      push  0x20
      cmp   bl, 0x01
      jz    build_v1_string_2
      push  0x73
      build_v1_string_2:
      mov   cx, 0x656c
      push  cx
      push  0x74746f62

      xor   cx, cx
      mov   cl, 0x20
      push  cx
      push  ax
      push  0x202c6c6c
      push  0x61772065
      push  0x6874206e
      push  0x6f207265
      push  0x65622066
      mov   cx, 0x6f20
      push  cx
      cmp   bl, 0x01
      jz    build_v1_string_3
      xor   cx, cx
      mov   cl, 0x73
      push  cx
      build_v1_string_3:
      xor   cx, cx
      mov   cl, 0x65
      push  cx

      push  0x6c74746f
      mov   cx, 0x6220
      push  cx
      push  ax

      xor   eax, eax
      mov   al,  0x04

      xor   ebx, ebx
      mov   bl,  0x01

      mov   ecx, esp

      mov   edx, ebp
      sub   edx, esp

      int   0x80

      leave
      ret

    verse_part_two:
      push  ebp
      mov   ebp, esp

      mov   eax, ecx
      sub   eax, 0x01
      call  convert_to_ascii

      xor   ebx, ebx
      xor   edx, edx

      cmp   al, dl
      jnz   build_v2_string
      cmp   ah, 0x31
      jnz   build_v2_string
      mov   bl, 0x01

      build_v2_string:
      xor   ecx, ecx
      mov   cx, 0xb0b
      sub   cl, 0x01
      sub   ch, 0x01
      push  cx
      push  0x2e2e2e6c
      push  0x6c617720
      push  0x65687420
      push  0x6e6f2072
      push  0x65656220
      mov   cx, 0x666f
      push  cx
      xor   cx, cx
      mov   cl, 0x20
      push  cx
      cmp   bl, 0x01
      jz    build_v2_string_2
      push  0x73
      build_v2_string_2:
      push  0x656c7474
      mov   cx, 0x6f62
      push  cx
      xor   cx, cx
      mov   cl, 0x20
      push  cx
      push  ax
      push  0x202c646e
      push  0x756f7261
      push  0x20746920
      push  0x73736170
      push  0x202c6e77
      push  0x6f642065
      push  0x6e6f2065
      mov   cx, 0x6b61
      push  cx
      xor   cx, cx
      mov   cl, 0x54
      push  cx

      xor   eax, eax
      mov   al,  0x04
      xor   ebx, ebx
      mov   bl,  0x01
      mov   ecx, esp
      mov   edx, ebp
      sub   edx, esp
      int   0x80

      leave
      ret

    outro:
      push  ebp
      mov   ebp, esp

      xor   eax, eax
      mov   al, 0xb
      sub   al, 0x01
      push  ax
      push  0x20217475
      push  0x6f206465
      push  0x73736170
      push  0x20646e61
      push  0x206b6e75
      push  0x72642065
      push  0x72276577
      push  0x20776f6e
      push  0x203b646e
      push  0x756f7261
      push  0x206d6568
      push  0x74206465
      push  0x73736170
      push  0x20646e61
      push  0x206e776f
      push  0x64206d65
      push  0x6874206e
      push  0x656b6174
      push  0x20657627

      xor   ax, ax
      mov   ax, 0x6557
      push  ax

      xor   ax, ax
      mov   ah, 0x0b
      mov   al, 0x2e
      sub   ah, 0x01
      push  ax

      push  0x72656562
      push  0x20666f20
      push  0x73656c74
      push  0x746f6220
      push  0x65726f6d
      push  0x206f6e20
      push  0x2c6c6c61
      push  0x77206568
      push  0x74206e6f
      push  0x20726565
      push  0x6220666f
      push  0x2073656c
      push  0x74746f62
      push  0x2065726f
      push  0x6d206f4e

      xor   eax, eax
      mov   al,  0x04
      xor   ebx, ebx
      mov   bl,  0x01
      mov   ecx, esp
      mov   edx, ebp
      sub   edx, esp
      int   0x80

      leave
      ret