%define	fd_num	32

		section .bss

fd_table:	resb (0x10 * fd_num)

		section .text

fd_to_ptr:	push cx
		mov cl, 4
		sal bx, cl
		add bx, fd_table
		pop cx
		ret

fd_read:	cmp bx, fd_num
		jnc fd_inv_hnd
		call fd_to_ptr
		; read ptr to ftab
		mov bx, [bx]
		; jmp to addr in ftab[0]
		jmp [bx]

fd_write:	cmp bx, fd_num
		jnc fd_inv_hnd
		call fd_to_ptr
		mov bx, [bx]
		jmp [bx+2]

fd_inv_hnd:	mov ax, 6
		stc
		ret