; number of sectors to be read
; 3 * 512 for bootloader stage2 and the kernel code 
; (note: the first sector gets loaded by the BIOS, so
; subtract 1 here!)
NOF_LOAD_SECTORS equ 13

; IN bx: begin of memory area to dump
; IN ax: number of words to dump
dump_range:
	mov dx, bx
	call print_hex
	mov dx, [bx]
	call print_hex
	call print_newline
	add bx, 2
	dec ax
	cmp ax, 0
	jnz dump_range
	ret

; IN dx: hex value to print	
print_hex:
	push bx
	push si
	mov si, HEX_TEMPLATE
	mov bx, dx
	shr bx, 12
	mov bx, [HEXABET+bx]
	mov [HEX_TEMPLATE+2], bl
	mov bx, dx
	and bx, 0x0FFF
	shr bx, 8
	mov bx, [HEXABET+bx]
	mov [HEX_TEMPLATE+3], bl
	mov bx, dx
	and bx, 0x00FF
	shr bx, 4
	mov bx, [HEXABET+bx]
	mov [HEX_TEMPLATE+4], bl
	mov bx, dx
	and bx, 0x000F
	mov bx, [HEXABET+bx]
	mov [HEX_TEMPLATE+5], bl
	call print_string
	pop si
	pop bx
	ret

HEX_TEMPLATE:
	db '0x???? ', 0

HEXABET:
	db '0123456789ABCDEF'

print_newline:
	push ax
	mov al, 10
	call print_char
	mov al, 13
	call print_char
	pop ax
	ret

; IN si
print_string:
	push ax
_loop_print_string:
	lodsb
	cmp al, 0
	je print_string_fini
	call print_char
	jmp _loop_print_string
print_string_fini:
	pop ax
	ret

; IN al: character to print
; MOD ah
print_char:
	mov ah, 0x0e
	int 0x10
	ret

fat_cursor:
	push ax
	push cx
	mov ah, 0x01
	mov cx, 0x0007
	int 0x10
	pop cx
	pop ax
	ret

; OUT: current row
current_row:
	push ax
	push bx
	push cx
	mov ah, 0x03
	mov bh, 0
	int 0x10
	pop cx
	pop bx
	pop ax
	ret

; IN dl: drive to read from
read_from_disk:

	mov ah, 0x02			; read sectors from drive
	
	mov al, NOF_LOAD_SECTORS	; read 1 sector
	mov ch, 0			; select first cylinder
	mov dh, 0			; first head
	mov cl, 2			; second sector after boot sector
	
	mov bx, 0			; where to store the data
	mov es, bx
	mov bx, 0x7e00			; 512 bytes after first sector
		
	int 0x13
	
	jc read_error
	
	cmp al, NOF_LOAD_SECTORS	; 1 sector read?
	jne short_read			; if not, short read
	
	ret
	
read_error:
	mov si, DISK_ERROR
	call print_string
	mov dh, 0
	mov dl, ah
	call print_hex
	jmp $

short_read:
	mov si, SHORT_READ
	call print_string
	jmp $