rdos/kernel/fd.asm

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%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