如何在内联汇编C

如何在内联汇编C

本文介绍了如何在内联汇编C ++中设置eax寄存器的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

eax和ebx是32位寄存器。 a []和b []数组有4个字符和32位数据。我可以在每个寄存器中单独设置数组的每个索引,例如mov eax,a [1]。

但是我想将所有4个数组'a'的字符设置为eax寄存器。重要的是序列。我想设置这两个寄存器而不对数组内容序列进行任何更改。例如,第一个数组是[0] ='a',a [1] ='b',a [2] ='c',a [3] ='d',eax寄存器必须为abcd 。我怎么能这样做?



我尝试过:



eax and ebx are 32 bits registers. a[] and b[] arrays have 4 chars and 32 bits data. i can separately set each index of array in each register for example mov eax,a[1].
but I wanna set all 4 chars of array 'a' to eax register. the important thing is the sequence. I want to set those two registers without any changes in the arrays content sequence. for example first array is a[0]='a',a[1]='b',a[2]='c',a[3]='d' and the eax register must be as "abcd". how can I do that?

What I have tried:

<pre lang="c++">
int _tmain()
{
char b[4],a[4];
b[0]='A',b[1]='T',b[2]='C',b[3]='G';
a[0]='A',a[1]='T',a[2]='C',a[3]='G';
__asm
{
    movzx eax,a[1]  //here i want to load all 4 char of a
    movzx ebx,b[1]  //here i want to load all 4 char of b
}
getchar();
return 0;
}

推荐答案

MOV EAX,BYTE PTR [addr]



如果要从字节数组加载32位值,请告诉编译器他必须加载32位字(未经测试但应该这样做):


If you want to load a 32 bit value from a byte array, tell the compiler that he has to load 32 bit words (untested but should do it):

__asm
{
    mov eax,DWORD PTR [a]
    mov ebx,DWORD PTR [b]
}



请注意在这两种情况下使用 MOVZX 在源和目的地大小相同时没有任何意义。





同时进行了测试。使用 DWORD PTR 按预期工作,而使用转换指针不起作用(加载寄存器的地址为a32或b32)。

[/ EDIT ]

Note that in both cases using MOVZX makes no sense when source and destination have the same size.


Have tested it meanwhile. Using DWORD PTR works as expected while using a casted pointer does not work (loads register with address of a32 resp. b32).
[/EDIT]


Quote:

eax和ebx是32位寄存器。 a []和b []数组有4个字符和32位数据。我可以在每个寄存器中单独设置数组的每个索引,例如mov eax,a [1]。

eax and ebx are 32 bits registers. a[] and b[] arrays have 4 chars and 32 bits data. i can separately set each index of array in each register for example mov eax,a[1].



首先,你应该尝试更换


first of all, you should try to replace

movzx eax,a[1]  //here i want to load all 4 char of a
movzx ebx,b[1]  //here i want to load all 4 char of b



by


by

movzx eax,a[0]  //here i want to load all 4 char of a
movzx ebx,b[0]  //here i want to load all 4 char of b



因为数组是0的基础C ++。


because arrays are 0 based in C++.

Quote:

如何设置eax寄存器,内联汇编C ++

How to set eax register in, inline assembly C++



否则,你的问题是什么使用此代码?


otherwise, what is your problem with this code ?


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08-19 16:21