Question

这是我在NASM写的代码

此代码在字符串s1中找到字符串s2，如果找到则返回索引，如果未找到则返回-1。

我的麻烦是我的EBX（索引），它增加1,2,3，... 9 ok但是当inc到10时，他们会显示＆＃39;：＆＃39;或者它显示＆＃39;;＆＃39;

我不知道为什么？请帮忙

非常感谢

抱歉我的英文不好

; DINH VAN KIET
; TUAN 3
; Find String 32bit

; Build
; nasm -f elf find_string_32bit.asm -o find_string_32bit.o ; file object will be created
; ld -m elf_i386 -o find_string_32bit find_string_32bit.o ; link the object file and create executable file

; MO TA
; Tim chuoi s2 trong chuoi s1

SYS_EXIT EQU 1
SYS_READ EQU 3
SYS_WRITE EQU 4
STDIN EQU 0
STDOUT EQU 1

%define LEN 64 ; do dai toi da
%define LEN_STT 2

segment .data
    msgS1 db 'Nhap chuoi s1: '
    msgS1Len equ $ - msgS1
    msgS2 db 'Nhap chuoi s2 (can tim): '
    msgS2Len equ $ - msgS2
    pos dw 00

segment .bss
    s1 resw LEN
    s2 resw LEN

    temp resb 1

segment .learn
    global _start
_start:
    mov edx,msgS1Len
    mov ecx,msgS1
    call display

    mov edx,LEN
    mov ecx,s1
    call read

    mov edx,msgS2Len
    mov ecx,msgS2
    call display

    mov edx,LEN
    mov ecx,s2
    call read

    ; dung eax de xu ly chuoi s2
    mov eax,[s2]
    mov edx,0 ; dung edx lam index

    ; dung ecx de xu ly chuoi s1
    mov ecx,s1
    mov ebx,-1 ; dung ebx de dem

lap1:
    ; kiem tra het chuoi
    cmp byte[ecx],0
    je done

    ; duyet tung ki tu cua s2
    mov eax,[s2+edx]
    mov [temp],eax

    ; de test
    ;push ebx
    ;push edx
    ;push ecx
    ;mov edx,1
    ;mov ecx,temp
    ;call display
    ;pop ecx
    ;pop edx
    ;pop ebx

    ; dua cac ki tu vao thanh ghi al va ah de so sanh
    mov al,byte[ecx]
    mov ah,[temp]

    cmp ah,0xA ; kiem tra xem da het chuoi s2 hay chua?
    je done

    inc ebx ; tang bien vi tri
    inc ecx ; tang index cua ecx

    cmp al,ah ; kiem tra xem ki tu co khop nhau hay ko?
    je meet
    jne miss

    jmp lap1

; Neu khop
meet:
    cmp edx,0
    jne met 

    push ebx

    inc edx ; tang bien edx de kiem tra tiep s2
    jmp lap1

; Neu tiep tuc khop
met:
    inc edx
    jmp lap1

; Neu khong khop
miss:
    mov edx,0 ; dua edx ve dau s2 de kiem tra lai
    jmp lap1

; Neu tim thay
found:
    ; in ra vi tri tim thay
    pop ebx
    add ebx,'0' 
    jmp exit

; Neu khong tim thay
notfound:
    ; in ra -1
    mov ebx,'-1'
    jmp exit

done:
    cmp edx,0
    je notfound
    jne found

exit:
    mov [pos],ebx

    mov edx,2
    mov ecx,pos
    call display 

    mov eax,SYS_EXIT
    int 80h

display:
    mov eax,SYS_WRITE
    mov ebx,STDOUT
    int 80h
    ret

read:
    mov eax,SYS_READ
    mov ebx,STDIN
    int 80h
    ret

Answer 1

问题是你是将一个数字显示为一个字符。

add ebx, '0'

是将数字转换为字符以进行显示的好方法。将数字转换为字符进行显示是一种糟糕的方法。

您需要以下内容：

; variable in ebx
itoa:
   mov eax, ebx
   mov ecx, 10
   mov esi, buf + 10
   xor edx, edx
.nxt
   div ecx
   add dl, '0'
   dec esi
   mov [esi], dl
   or  eax, eax
   jnz .nxt
   mov edx, buf + 10
   sub edx, esi
   ret

   ; pointer in esi, length in edx

;... (bss area)
buf resb 10

超过9的Nasm增量寄存器无法显示

1 个答案: