1 files changed, 105 insertions, 0 deletions
diff --git a/boot/common.asm b/boot/common.asm
new file mode 100644
index 0000000..02e1a0b
--- /dev/null
+++ b/boot/common.asm
@@ -0,0 +1,105 @@
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;;;;;; 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
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;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
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;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
+