; global position for vram
vb_pos: dd 0

;;;;;;;;;;;;;;;;;;;;;
;print a 32-bit integer
; input: push u32
;;;;;;;;;;;;;;;;;;;;;;
print_u32:
push ebp
mov ebp, esp

push eax
push ebx
push ecx

; loop 4 times
mov ebx, 8
mov ecx, 32 - 4
.lp:
; eax = thing to print
mov eax, dword [ebp + 2 * 4]
shr eax, cl
and eax, 0xF

call al_to_char
call print_char

sub ecx, 4
dec ebx
test ebx, ebx
jne .lp

pop ecx
pop ebx
pop eax
pop ebp
ret

;;;;;;;;;;;;;;;;;;;;;
;print a char in
;;;;;;;;;;;;;;;;;;;;;;
print_char:
; input: al = char
push edi
push eax
push esi
push ecx

; esi points to current frame buffer
mov esi, 0xb8000
; edi points to offset
mov edi, dword [vb_pos]

; handle return character
cmp al, 0xA
jne .char
; round up to 80 * 2
mov eax, edi
add ax, 2 * 80 - 1
mov cl, 2 * 80
div cl
mul cl
mov edi, eax
jmp .end
.char:
mov byte [esi + edi], al
mov word [esi + edi + 1], 0xf
add edi, 2

.end:
mov dword [vb_pos], edi

pop ecx
pop esi
pop eax
pop edi
ret

;;;;;;;;;;;;;;;;;;;;;
;print a null-terminated string
;;;;;;;;;;;;;;;;;;;;;;
print_str:
;offset
push ebp
mov ebp, esp

push esi
push eax
push edi

mov esi, dword [ebp + 2 * 4]

mov edi, 0xb8000

.loop_each_char:
mov al, byte [esi]
test al, al
je .end
call print_char
inc esi
jmp .loop_each_char

.end:
pop edi
pop eax
pop esi
pop ebp
ret

;;;;;;;;;;;;;;;;;;;;;
; helper function converting 4 bit val in al to its character
;;;;;;;;;;;;;;;;;;;;;;
al_to_char:
; no parameters
cmp al,09h
jna .l2
add al,37h
jmp .end
.l2:
add al,30h
.end:
ret