inp.asm

C标准库源代码,能提高对C的理解,不错的哦

        page    ,132
        title   inp - input from ports
;***
;inp.asm - _inp, _inpw and _inpd routines
;
;       Copyright (c) 1993-1997, Microsoft Corporation. All rights reserved.
;
;Purpose:
;       Defines the read-from-a-port functions: _inp(), _inpw() and inpd().
;
;*******************************************************************************

        .xlist
        include cruntime.inc
        .list


page
;***
;int            _inp(port)  - read byte from port
;unsigned short _inpw(port) - read word from port
;unsigned long  _inpd(port) - read dword from port
;
;Purpose:
;       Read single byte/word/dword from the specified port.
;
;Entry:
;       unsigned short port - port to read from
;
;Exit:
;       returns value read.
;
;Uses:
;       EAX, EDX
;
;Exceptions:
;
;*******************************************************************************

        CODESEG

        public _inp, _inpw, _inpd

_inp    proc

        xor     eax,eax
        mov     dx,word ptr [esp + 4]
        in      al,dx
        ret

_inp    endp


_inpw   proc

        mov     dx,word ptr [esp + 4]
        in      ax,dx
        ret

_inpw   endp

_inpd   proc

        mov     dx,word ptr [esp + 4]
        in      eax,dx
        ret

_inpd   endp

        end