x86 中字符串和变量的连接

Question

我正在尝试连接字符串和变量并将其存储到 x86 中的新变量中。 我正在使用 nasm 编写汇编代码。 我想做的是这样的：

a = 1;
b = 2;
c = "values are: " + a + " and " + b ;
print c;

但我不知道如何连接并为新变量赋值

Answer 1

a = 1;
b = 2;
c = "values are: " + a + " and " + b ;

这个数据大致翻译为：

a db 1
b db 2
c db "values are: ? and ?$"

您的变量 a 和 b 是数字。在将它们插入字符串之前，您需要将它们转换为文本，在这个简化的示例中，字符串使用问号字符 (?) 作为单个字符占位符。

mov al, [a]       ;AL becomes 1
add al, '0'       ;AL becomes "1"
mov [c + 12], al  ;12 is offset of the first '?'
mov al, [b]       ;AL becomes 2
add al, '0'       ;AL becomes "2"
mov [c + 18], al  ;18 is offset of the second '?'
mov dx, c         ;Address of the string
mov ah, 09h
int 21h           ;Print with DOS

---

这是上述代码的替代方案。它的一些指令更短，但缺点是不能太重用！ （因为 add 取决于占位符保持为零）

a db 1
b db 2
c db "values are: 0 and 0$"


mov al, [a]       ;AL becomes 1
add [c + 12], al  ;12 is offset of the first '0'
mov al, [b]       ;AL becomes 2
add [c + 18], al  ;18 is offset of the second '0'
mov dx, c         ;Address of the string
mov ah, 09h
int 21h           ;Print with DOS