From 88a8caca6781365eeb427d5c6e660b2d7576485d Mon Sep 17 00:00:00 2001
From: iximeow <me@iximeow.net>
Date: Fri, 26 Sep 2014 22:15:07 -0700
Subject: Hefty bootloader changes, some screen manip functions

---
 bootloader.asm | 143 +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 139 insertions(+), 4 deletions(-)

diff --git a/bootloader.asm b/bootloader.asm
index 181c1dc..2993726 100644
--- a/bootloader.asm
+++ b/bootloader.asm
@@ -1,12 +1,147 @@
+[BITS 16]
+[ORG 7c00h]
 
-  mov cx, 0x10
-  mov ah, 0x0A
-  mov al, 0x74
-  int 0x10
+init:
+  mov cx, 0xB800
+  mov gs, cx
 
+start:
+  call clr_vga
+  mov si, HELLO
+  call write_str
+  call disk_read
+  mov si, VERIFY
+  call write_str
+  mov ax, 0x61
+  call cursor_next_line
+  call write_char_default_attr
+  mov ax, 0x62
+  call cursor_next_line
+  call write_char_default_attr
+  mov ax, 0x63
+  call cursor_next_line
+  call write_char_default_attr
+  call write_char_default_attr
+  call write_char_default_attr
+  call cursor_back_one
+  call cursor_backspace
+  jmp hang
+
+read_err:
+  mov si, READ_ERR
+  call write_str
 hang:
   jmp hang
 
+write_str:
+  push ax
+  push si
+  xor ax, ax
+write_str_each_char:
+  mov al, byte [si]
+  cmp al, 0
+  je write_str_done
+  inc si
+  call write_char_default_attr
+  jmp write_str_each_char
+write_str_done:
+  pop si
+  pop ax
+  ret
+
+write_char_default_attr:
+  push bx
+  mov bl, 0x07
+  jmp write_char_inner
+write_char:
+  push bx
+write_char_inner:
+  push di
+  mov di, [CURSOR_LOC]
+  mov byte [gs:di], al
+  inc di
+  mov byte [gs:di], bl
+  inc di
+  mov [CURSOR_LOC], di
+  pop di
+  pop bx
+  ret
+
+clr_vga:
+  mov di, 4000
+clr_vga_loop:
+  dec di
+  mov byte [gs:di], 0x00
+  cmp di, 0
+  jne clr_vga_loop
+  mov word [CURSOR_LOC], 0
+  ret
+
+disk_read:
+  ; ax = disk number to read from
+  ; reference: http://www.delorie.com/djgpp/doc/rbinter/id/14/7.html
+  mov dx, 0x80
+  or ax, dx
+  mov si, LBA_DISK_READ_PACKET
+  mov ah, 0x42
+  int 0x13
+  jc read_err
+  mov si, READ_SUCC
+  call write_str
+  ret
+
+READ_ERR:
+  db 'Read failed: ', 0
+READ_SUCC:
+  db 'Read didnt fail: ', 0
+HELLO:
+  db 'Bootloader init: ', 0
+CURSOR_LOC:
+  dw 0
+
+ ; reference: http://www.delorie.com/djgpp/doc/rbinter/it/72/2.html
+LBA_DISK_READ_PACKET:
+  db 0x10
+  db 0
+  dw 1      ; number of blocks to read, reset to # actually read when done
+  dw 0x7e00 ; read destination address
+  dw 0
+  dd 1      ; lba to read from
+  dd 0      ; for extended lba adresses (not really used here)
+
   times 510-($-$$) db 0
   db 0x55
   db 0xAA
+
+cursor_next_line:
+  mov di, [CURSOR_LOC]
+  add di, 160
+  mov [CURSOR_LOC], di
+  ret
+
+cursor_prev_line:
+  mov di, [CURSOR_LOC]
+  sub di, 160
+  mov [CURSOR_LOC], di
+  ret
+
+cursor_backspace:
+  push ax
+  call cursor_back_one
+  mov ax, 0x00
+  call write_char_default_attr
+  call cursor_back_one
+  pop ax
+  ret
+
+cursor_back_one:
+  mov di, [CURSOR_LOC]
+  dec di
+  dec di
+  mov [CURSOR_LOC], di
+  ret
+
+VERIFY:
+  db '[x] read next block: ', 0
+
+  times 1024-($-$$) db 0
-- 
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