8086汇编语言王爽 17.3 字符串的输入 (含输入溢出问题分析)

assume cs:code
; dsstack segment
;     db 16 dup(0) 
; dsstack ends
code segment 
start:
    ; mov ax,dsstack
    ; mov ds,ax
    ; mov si,13
    ; mov sp,160
    call getstr
    mov ax,4c00h
    int 21h

getstr:
    push ax
getstrs:
    mov ah,0
    int 16h
    cmp al,20h
    jb nochar
    mov ah,0
    call charstack
    mov ah,2
    call charstack
    jmp getstrs

nochar:
    cmp ah,0eh
    je backspace
    cmp ah,1ch
    je enter
    jmp getstrs

backspace:
    mov ah,1
    call charstack
    mov ah,2
    call charstack
    jmp getstrs
    
enter:
    mov al,0
    mov ah,0
    call charstack
    mov ah,2
    call charstack
    pop ax
    ret

; ==================================
charstack:
    jmp short charstart
    table dw charpush,charpop,charshow
    top dw 0 ; top of stack
charstart:
    push bx
    push dx
    push di
    push es

    cmp ah,2
    ja charret
    mov bl,ah
    mov bh,0
    add bx,bx
    jmp word ptr table[bx]

charpush:
    mov bx,top
    mov ds:[si][bx],al
    add top,1
    jmp charret

charpop:
    cmp top,0
    je charret
    dec top
    mov bx,top
    mov al,[si][bx]
    jmp charret

charshow:
    mov bx,0b800h
    mov es,bx
    mov al,160
    mov ah,0
    mul dh
    mov di,ax
    add dl,dl
    mov dh,0
    add di,dx

    mov bx,0
charshows:
    cmp bx,top
    jne noempty
    mov byte ptr es:[di],'+'  ; 结束符
    jmp charret

noempty:
    mov al,[si][bx]
    mov es:[di],al
    mov byte ptr es:[di+2],'+' ; 结束符
    inc bx
    add di,2
    jmp charshows

charret:
    pop es
    pop di
    pop dx
    pop bx
    ret

code ends 
end start