;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;; Miguel's FoolOS Helper Functions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
[bits 16]


;global data
STR_HEX_OUT:
    db "0x0000",0

;print_string routine ([bx])
;this routine will print a null terminated string at [bx] to the screen.
print_string:

    pusha			;push all registers
    mov ah,0x0e

    print_string_loop:

	;check if value at [bx] is "\0" (end of string)
	mov cl,[bx]
	cmp cl,0
	je print_string_finish

	;otherwise instruct BIOS to print the current char
	mov al,cl
	int 0x10

	;proceed with next char
        inc bx
	jmp print_string_loop

    print_string_finish:

    popa			;pop all registers
    ret				;return to caller

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;print_hex routine (dx)
;will print the value of the bx register as hex to the screen
print_hex:

    pusha

    ;begin with last hex val (hex_out[5])
    mov bx,STR_HEX_OUT+5

    ;lets loop throuth all 4 'digits'
    print_hex_loop:

    ;get least significan hex digit to cx
    mov cx,dx
    and cx,0x000F

    ;check range (0-9 vs a-f)
    cmp cx,10
    jl print_hex_setnum

    ;set hex a-f
    mov al,'A'-10		
    add al,cl
    jmp print_hex_al

    ;set hex 0-9
    print_hex_setnum:
    mov al,'0'		
    add al,cl

    ; set hex_out[bx] to al
    print_hex_al:
    mov [bx],al

    ;proceed with the next significant hex 'digit'
    dec bx
    shr dx,4

    ;check if finished (otherwise loop)
    cmp bx,STR_HEX_OUT+1
    jne print_hex_loop

    ;output complete hex string and return to caller
    mov bx,STR_HEX_OUT
    call print_string
    popa
    ret

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;disk_load routune (load dh sectors from drive dl to es:bx)
disk_load:

    pusha

    mov ah,0x02		;BIOS read sector func
    mov al,dh		;read dh sectors (amount)
    mov ch,0x00		;cyl 0
    mov dh,0x00		;head 0
    mov cl,0x02		;start at sector 2

    int 0x13		;bios interrupt

    popa
    ret