bufprf.asm

一个朋友写的操作系统源码

;/++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
; printnm is the modify verion of printf, it won't do I/O operating
; just used as a format convertion tools to normalize the line number
; in decimal makes it looks all right.

; The entry points into this file are
;   printnm  :  insert the char to the specified file offset
;   printnum :  convert the binary to the normalize decimal
;++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++/

include comstruc.inc
include arg.inc

sseg segment stack

     db 128 dup (0)

sseg ends

dseg segment para public 'global'

     extrn inrtpos:word

dseg ends

cseg segment para public 'code'

     assume cs:cseg,ds:dseg,es:dseg,ss:sseg

     public printnm


;/============================================================================
;
;                             printnm
;
;============================================================================/


     printnm proc near

     push ds
     push es
     push bp
     mov bp,sp
     sub sp,8

     ; stack arranges like this
     ;
     ; [bp-2] : bit count of decimal
     ; [bp-4] : a
     ; [bp-6] : n
     ; [bp-8] : b

     ; initialize the max label bit,
     ; 5 bit in decimal can expresses
     ; less than 65535 lines, because
     ; the integer is only 16 bit

     mov word ptr [bp-2],0

     mov ax,8[bp]
     mov [bp-6],ax      ; get n
     mov ax,10[bp]
     mov [bp-8],ax      ; get b

     ; first we get space printed, 'spnr'
     ; indicates how many spaces needed

     mov cx,spnr
sploop:
     cmp cx,0
     jz pn1loop
     mov ax,20h
     push ax
     call printnum      ; print one space each time
     pop ax
     dec cx
     jmp sploop

pn1loop:
     mov ax,[bp-2]
     xor dx,dx
     mov ax,[bp-6]
     mov bx,[bp-8]
     div bx
     mov [bp-4],ax

     xor dx,dx
     mov ax,[bp-6]
     mov bx,[bp-8]
     div bx
     add dx,30h          ; convert to ascii
     push dx
     call printnum
     pop cx
     mov ax,[bp-4]
     mov [bp-6],ax
     inc word ptr [bp-2]
     cmp ax,0
     jnz pnmnext1        

     ; if [bp-4] == 0, feed rest room with '0'

     mov cx,insertnr
     sub cx,[bp-2]


     sub cx,spnr



     jz goback       ; if 5 bit is feed, no '0' can feed
feedloop:
     push cx
     cmp cx,0
     jz goback
     mov ax,30h      ; '0'
     push ax
     call printnum
     pop ax
     pop cx
     dec cx
     jmp feedloop
goback:
     mov sp,bp
     pop bp
     pop es
     pop ds
     ret

pnmnext1:
     jmp pn1loop

     printnm endp


;/============================================================================
;
;                             printnum
;
;============================================================================/

     printnum proc near

     push ds
     push es
     push bp
     mov bp,sp
     sub sp,2

     ; stack arranges like this
     ;
     ; [bp-2] : ascii to be inserted

     mov ax,8[bp]
     mov [bp-2],ax
     mov al,[bp-2]
     mov di,inrtpos
     std
     stosb
     mov inrtpos,di     ; save next position

     mov sp,bp
     pop bp
     pop es
     pop ds
     ret

     printnum endp

cseg ends

end