在Assembly x86 tasm中实现任务删除功能

我目前正在编写一个用于任务管理的Assemblyx 86 tasm语言程序，它允许添加和查看任务。然而，我一直在努力实现一个删除特定任务的功能。

.model small
.stack 100h
.data
sir db 80 dup('$') 
m2 db 'Introduceti sirul:$'
m4 db '1. Add task', 13, 10, '$'
m5 db '2. View tasks', 13, 10, '$'
filename db 'tasks.txt',0
handle dw ?
strLength dw ?
t_handle dw ?
newline db 13, 10, '$' ; New line characters
menuChoice db ?
buffer db 2000 dup(0)
.code
    mov ax,@data
    mov ds,ax
    
    mov ah, 9h
    mov dx, offset m4
    int 21h
    
    mov ah, 9h
    mov dx, offset m5
    int 21h
    
    mov ah, 1h
    int 21h
    mov menuChoice, al
    
    cmp menuChoice, '1'
    je add_task
    cmp menuChoice, '2'
    je view_tasks
    cmp menuChoice, '3'
    je delete_aux
    
    jmp end_program

view_tasks:
    ; Opening file for reading
    mov ah, 3Dh 
    mov al, 0 
    mov dx, offset filename 
    int 21h 
    mov handle, ax 

    ; Reading file contents
    mov ah, 3Fh 
    mov bx, handle 
    mov dx, offset sir 
    mov cx, 80 
    int 21h 

    ; Displaying tasks line by line with incrementing numbers
    mov si, offset sir

    display_loop:
        ; Check if end of file or end of buffer
        cmp byte ptr [si], '$'
        je end_display
        ; Print character to screen
        mov ah, 02h 
        mov dl, [si] 
        int 21h 
        ; Move to the next character
        inc si
        jmp display_loop

    end_display:
    ; Close the file
    mov ah, 3Eh ; File close service
    mov bx, handle ; File handle
    int 21h ; File close interrupt

    jmp end_program

delete_aux:
    cmp menuChoice, '3' ; Check if the choice is for delete
    jne view_tasks ; If not, jump to view_tasks
    jmp delete_task ; If yes, jump to delete_task

add_task:
    ; Clearing the buffer
    mov ah, 0Ah
    mov dx, offset sir
    int 21h

    ; Adding a task to the file
    ; Prompting for task input
    mov ah, 9h
    mov dx, offset m2
    int 21h
    
    mov bx,0 
    mov cx,80 
    mov ah,3fh
    mov dx,offset sir
    int 21h

    mov ah, 9h
    mov dx, offset sir
    int 21h

    ; Calculating string length
    mov si, offset sir
    add si, 2
    mov cx, 0 ; Initialize count
    count_length:
        cmp byte ptr [si], '$' 
        je end_count
        inc cx 
        inc si
        jmp count_length 
    
    end_count:
    mov strLength, cx 

    ; Opening file for appending at the end
    mov ah, 3Dh 
    mov al, 2 ;
    mov dx, offset filename
    int 21h 
    mov handle, ax 

    ; Positioning at the end of the file
    mov ah, 42h 
    mov al, 2 
    mov bx, handle 
    mov cx, 0 
    mov dx, 0 
    int 21h 

    ; Writing string to file
    mov ah, 40h
    mov bx, handle 
    mov dx, offset sir 
    mov cx, strLength
    int 21h

; Writing newline to file
    mov ah, 40h 
    mov bx, handle
    mov dx, offset newline 
    mov cx, 2
    int 21h

    ; Closing the file
    mov ah, 3Eh 
    mov bx, handle
    int 21h
   
    jmp view_tasks

delete_task:
    
    jmp view_tasks ; Redirect to view tasks after deletion

end_program:
    mov ah,4Ch
    int 21h
end

字符串
我试过实现一个“删除任务”选项，并使用终止字符13，10，“$”管理文件操作，但我不能得到它的窍门。

delete_task:
    ; Prompt for task number to delete
    mov ah, 9h
    mov dx, offset m_delete_prompt
    int 21h

    ; Read user input for the task number to delete
    mov ah, 1h
    int 21h
    sub al, '0' 
    mov bl, al

    ; Opening the file for reading and writing
    mov ah, 3Dh 
    mov al, 2 
    mov dx, offset filename 
    int 21h
    mov handle, ax 

    ; Reading and deleting the desired task
    mov ah, 3Fh 
    mov bx, handle 
    mov dx, offset buffer 
    mov cx, 2000 
    int 21h

    mov si, offset buffer
    mov di, si

    delete_loop:
        cmp byte ptr [si], '$' 
        je end_delete
        mov al, [si]
        cmp al, 13 
        je check_next_char
        mov [di], al 
        inc di
        inc si
        jmp delete_loop

    check_next_char:
        inc si ; Move to next character (LF)
        mov al, [si]
        cmp al, 10
        je delete_task_found
        mov byte ptr [di], 13 
        inc di
        mov [di], al
        inc di 
        inc si
        jmp delete_loop

    delete_task_found:
        ; Check if it's the desired task to delete
        sub al, '0' 
        cmp al, bl  
        je skip_task   
        jmp copy_task

    skip_task:
        ; Skip the task to delete
        mov al, [si]
        cmp al, 13  
        jne skip_task 
        jmp delete_loop

    copy_task:
        ; Copy the task to keep it
        mov [di], al
        inc di 
        inc si 
        jmp delete_loop

    end_delete:
        ; Truncate the file at the updated position
        mov ah, 40h
        mov bx, handle
        mov dx, offset buffer
        sub di, offset buffer
        int 21h

        ; Close the file
        mov ah, 3Eh 
        mov bx, handle
        int 21h

    jmp view_tasks

; Data Section
m_delete_prompt db 'Enter the task number to delete: $'

型
对于以下任务：

task1
task2
task3
task4
task5

型
这就是我得到的：

task1
task2
task3
task4
task5
task1Útask2Útask3Útask4Útask5Ú                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             ÿÿùtâ

型

1.正如我在上面的评论中所说，应该保存删除任务的数量。所以push bx完成了这项工作。在delete_loop:之前使用pop bx恢复此值。
1.在delete_loop的开始处的指令cmp byte ptr [si], '$'搜索$，但是buffer被0填充。所以这个循环可以永远运行，除非内存中的某个地方有$。所以要么用$填充缓冲区，要么在buffer之后添加变量eotb db '$'来标记缓冲区的结束。

delete_loop里面发生的事情是这样的。
如果字节为0d，则转到check_next_char:
如果字节为0a，则转到delete_task_found:
al = 0a，因此此指令sub al '0'不会从'1' - '9'中继承'0'以获得正确的任务编号
其他字符t，a，s，k，1 - 9被跳过
我可以提出这个解决方案…
文件中的每个记录看起来都像这样task 1-9 0d 0a
任务的第一个编号位于位置buffer + 4
接下来是每7个字节：

buffer + 4 + 7
buffer + 4 + 7 + 7个
buffer + 4 + 7 + 7 + 7
buffer + 4 + 7 + 7 + 7 ...

如果程序在文件中找到任务的编号，则修改缓冲区并将新数据写入文件，否则$意味着文件中没有任务。
我写的代码只是为了删除任务

.model small
.stack 100h
.data
sir db 80 dup('$') 
m2 db 'Introduceti sirul:$'
m4 db '1. Add task', 13, 10, '$'
m5 db '2. View tasks', 13, 10, '$'
m6 db '3. Del tasks', 13, 10, '$'   

filename db 'code60t.txt',0
filesize dw ?
handle dw ?
strLength dw ?
t_handle dw ?
newline db 13, 10, '$' ; New line characters
menuChoice db ?
buffer db 70 dup('$')

m_delete_prompt db 13,10,'Enter the task number to delete: $'
task_doesnt_exists db 13,10,'This task is not in the file.',13,10,'$'
del_task db 13,10,'Deleting task number $'  

.code
start:
mov ax,@data
mov ds,ax

mov ah, 9h
mov dx, offset m4
int 21h

mov ah, 9h
mov dx, offset m5
int 21h

mov ah, 9h
mov dx, offset m6
int 21h

mov ah, 1h
int 21h
mov menuChoice, al

mov ah, 9h
mov dx, offset newline
int 21h

cmp menuChoice, '1'
je add_task
cmp menuChoice, '2'
je view_tasks
cmp menuChoice, '3'
je delete_aux

jmp end_program

view_tasks:
; Opening file for reading
mov ah, 3Dh 
mov al, 2 
mov dx, offset filename 
int 21h 
mov handle, ax 

; Reading file contents
mov ah, 3Fh 
mov bx, handle 
mov dx, offset sir 
mov cx, 80 
int 21h 

; Displaying tasks line by line with incrementing numbers
mov si, offset sir

display_loop:
    ; Check if end of file or end of buffer
    cmp byte ptr [si], '$'
    je end_display
    ; Print character to screen
    mov ah, 02h 
    mov dl, [si] 
    int 21h 
    ; Move to the next character
    inc si
    jmp display_loop

end_display:
; Close the file
mov ah, 3Eh ; File close service
mov bx, handle ; File handle
int 21h ; File close interrupt

jmp end_program

delete_aux:
cmp menuChoice, '3' ; Check if the choice is for delete
jne view_tasks ; If not, jump to view_tasks
jmp delete_task ; If yes, jump to delete_task

add_task:
; Clearing the buffer
mov ah, 0Ah
mov dx, offset sir
int 21h

; Adding a task to the file
; Prompting for task input
mov ah, 9h
mov dx, offset m2
int 21h

mov bx,0 
mov cx,80 
mov ah,3fh
mov dx,offset sir
int 21h

mov ah, 9h
mov dx, offset sir
int 21h

; Calculating string length
mov si, offset sir
add si, 2
mov cx, 0 ; Initialize count
count_length:
    cmp byte ptr [si], '$' 
    je end_count
    inc cx 
    inc si
    jmp count_length 

end_count:
mov strLength, cx 

; Opening file for appending at the end
mov ah, 3Dh 
mov al, 2 ;
mov dx, offset filename
int 21h 
mov handle, ax 

; Positioning at the end of the file
mov ah, 42h 
mov al, 2 
mov bx, handle 
mov cx, 0 
mov dx, 0 
int 21h 

; Writing string to file
mov ah, 40h
mov bx, handle 
mov dx, offset sir 
mov cx, strLength
int 21h

; Writing newline to file
mov ah, 40h 
mov bx, handle
mov dx, offset newline 
mov cx, 2
int 21h

; Closing the file
mov ah, 3Eh 
mov bx, handle
int 21h

jmp view_tasks

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

 delete_task: 
; Prompt for task number to delete
mov ah, 9h
mov dx, offset m_delete_prompt
int 21h

; Read user input for the task number to delete
mov ah, 1h
int 21h    
mov bl, al

push bx             ; save the number of the task

;---- file operations

; Opening the file for reading and writing
mov ah, 3Dh 
mov al, 2 
mov dx, offset filename 
int 21h
mov handle, ax 

; Reading from file to buffer
mov ah, 3Fh 
mov bx, handle 
mov dx, offset buffer 
mov cx, 70 
int 21h

; calculate file size, this value is used later
mov ah,42h
mov al,2
xor cx,cx
xor dx,dx
int 21h
mov filesize, ax

; close file, later program uses 3ch because we want to delete old data in file and write modified data
mov ah, 3eh     
int 21h

;---- buffer operations

mov si, offset buffer
add si, 4       ; first location of the task number

pop bx          ; restore the number of task 

delete_loop:
    cmp byte ptr [si],'$'       ; check if we reached end of buffer
    je no_tasks
    mov al, [si]                ; task number
    cmp al, bl                  ; is this our task?
    je task_found               ; yes
    add si, 7                   ; no, go to next record
    jmp delete_loop             ; try again

task_found:                 
    mov ah, 9h                  ; show some messages
    mov dx, offset del_task
    int 21h

    mov ah, 2h
    mov dl, bl      
    int 21h     

    mov ah, 9h
    mov dx, offset newline
    int 21h

    add si, 3                   ; start of the next record  
    mov di, si
    sub di, 7                   ; start of the record we want to delete
                                ; do this by moving rest of the tasks up 7 bytes

    mov al, 10                  ; we can have max 9 tasks (9 * 7 bytes = 63) + 7 bytes of '$' to clear end of the list
    mov ah, 0

    sub bl, 30h
    sub al, bl                   ; calculate how many bytes to copy
    mov bl, 7
    mul bl      
    mov cx, ax          

    tasks_move:
        mov al, [si]
        mov [di], al
        inc si
        inc di
        dec cx
        jnz tasks_move

    write_to_file:
        mov ah, 3ch         
        mov dx, offset filename
        mov cx, 2           
        int 21h             

        ; Writing modified buffer to file
        mov bx, ax
        mov ah, 40h         
        mov dx, offset buffer 
        mov cx, filesize
        sub cx,7
        int 21h     

        mov ah, 3eh     
        int 21h

jmp view_tasks

no_tasks:
    mov ah, 9h
    mov dx, offset task_doesnt_exists
    int 21h     

jmp view_tasks

end_program:
    mov ah,4Ch
    int 21h
end start

字符串

在Assembly x86 tasm中实现任务删除功能

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