在C ++中将数据写入内存 [英] Writing data to memory in C++

问题描述

我想在void * data中写一个int，char，real的混合。
我使用一个文件指针来运行数据块。
现在我的问题是，因为数据类型是void，我必须将其类型转换为int而写入整数和字符串的char。
虽然typecasting我使用下面的示例代码：

I want to write a a mix of int, char, real in void *data. I am using a file pointer to run through the data block. Now my question is that since the data type is void, I have to typecast it to int while writing integer and char for writing string. While typecasting I used the following sample code:

*((int *)data+0) = 14;      //writing int
*((int *)data+4) = 5;       //writing int, left a space of 4 bytes for int
*((char *)data+8) = 'a';    //writing char
*((char *)data+9) = 'f';    //writing char

但是在读取值的时候没有给出正确的值。

But then while reading the values back it didnt give the correct value.

cout<<*((int *)data+0);
cout<<*((int *)data+3);
cout<<*((char *)data+8);

我的代码是否正确写入？

Is the way my code is written correct? I am doubtful about it as data is void.

推荐答案

*((int *)data+4) = 5; // writing 4th int
cout<<*((int *)data+3); // but reading third one

到第4个整数（即，给定int size = 4的第16个字节），而不是第4个字节。也就是说，你的代码覆盖字节0-3，然后16-19，然后8th，然后9th。你可能的意思是： *（int *）（（char *）data + X）

And just in case, ((int *)data+4) points to 4th integer (that is, 16th byte given int size = 4), not to 4th byte. That is, you code overwrites bytes 0-3, then 16-19, then 8th, then 9th. What you probably meant is: *(int *)( (char*)data + X )

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