Manipulating Strings in Assembly (MASM)

问题

.data
    source  BYTE  "Defense mechanism",0
    target  BYTE  SIZEOF source DUP(0)

.code
    main PROC

        mov  esi, OFFSET target
        mov  edi, OFFSET target
        mov  ecx, SIZEOF source
    L1:
        mov  al,[esi]           ; get a character from source
        mov  [edi],al           ; store it in the target
        inc  esi                ; move to next character
        inc  edi
        loop L1

In the .data section, I see that source is defined as the string. In the .code section, I see that the memory location of target is stored in the source index. Shouldn't I want the source index (ESI) to point to source instead of target? This program is supposed to copy a string into the target box that has been initialized to the size of the source string and to have each of the fields filled with zeroes. I have no experience with Assembly language. What am I getting wrong? (Note: this is how my professor has the program listed out, but he isn't offering any real material on this because this is a web based "security in computing" course.

回答1:

Yes, you're right - esi should point at source, not target - it looks like your professor has at least one bug in that code. Change:

          mov  esi, OFFSET target

to:

          mov  esi, OFFSET source

来源：https://stackoverflow.com/questions/6522386/manipulating-strings-in-assembly-masm