為什麼這個彙編代碼不刪除擴展名為“.lnk”的文件？ (Why doesn't this assembly code delete the file with ".lnk" extension?)

問題描述

為什麼這個彙編代碼不刪除擴展名為“.lnk”的文件？ (Why doesn't this assembly code delete the file with ".lnk" extension?)

我正在嘗試使用程序集 8086 架構刪除擴展名為“.lnk”的文件。當我在“mov si, dx”之後寫“jmp DELETE”並跳過內部、back1、back2、back3 部分時，我的代碼會刪除所有文件，但是當它逐個字符檢查它是否具有 .lnk 擴展名時，它不會t 刪除其中任何一個，甚至不刪除擴展名為 .lnk 的文件。為什麼會這樣？

.MODEL SMALL
.STACK 100H
.DATA
FILE DB "*", 0
DTA DB 128H DUP(?)   
FILENAME DB 50 DUP(?)
.CODE

MAIN PROC  

    MOV AX,@DATA
    MOV DS,AX

    ;SET DTA
    MOV DX,OFFSET DTA
    MOV AH,1AH
    INT 21H

    ;FIRST SEARCH
    MOV DX,OFFSET FILE 
    MOV CX,0
    MOV AH,4EH
    INT 21H
    JC QUIT

OUTER_LOOP:


    ;DELETE
    LEA DX,DTA+30 
    mov si, dx 

    inner:
    cmp [si], 0
    je back1
    inc si
    jmp inner

    back1:
    dec si
    cmp [si],'K'
    je back2
    jmp NEXT

    back2:
    dec si
    cmp [si],'N'
    je back3
    jmp NEXT

    back3:

    dec si
    cmp [si], 'L'


    delete:
    LEA DX,DTA+30 
    MOV AH,41H
    INT 21H


    ;INITIATE NEXT SEARCH
    NEXT:
    MOV DX,OFFSET FILE 
    MOV CX,0
    MOV AH,4FH
    INT 21H
    JC QUIT

    JMP OUTER_LOOP



QUIT:
    MOV AX,4C00H
    INT 21H

MAIN ENDP
    END MAIN

參考解法

方法 1:

These points might interest you:

• Change your filemask to

  *.*
  

• Why do you set up such a large DTA?.

  DTA 44 dup(?)
  

• Always write cmp byte ptr [si], ...

• Don't stop comparing after the 3 characters. Add a fourth compare to see if the point is present. Then you'll know that LNK is indeed a file extension.

• Your 4Fh DOS call doesn't need the CX and DX parameters.

• You don't interpret the result from

  cmp [si], 'L'
  

(by harmione 、Sep Roland)

參考文件

1. Why doesn't this assembly code delete the file with ".lnk" extension? (CC BY‑SA 2.5/3.0/4.0)