写二进制文件（C ++）整数 [英] writing integer to binary file (C++)

问题描述

我有一个很简单的问题，这恰好是我很难，因为这是我第一次尝试用二进制文件的工作，我不太了解他们。所有我想要做的是写一个二进制文件的一个整数。

下面是我做的：

 的#include＆LT;＆的fstream GT;
使用命名空间std;
诠释主（）{
    INT NUM = 162;
    的ofstream文件（file.bin，IOS ::二进制）;
    file.write（（字符*）试验＃，的sizeof（NUM））;
    file.close（）;
    返回0;
}
 

你能告诉我，如果我做错了什么，和什么？

这是给我麻烦的部分是与file.write行了，我不明白。

感谢您提前。

解决方案

  

这是给我麻烦的部分是与file.write行，我不知道
  理解这一点。

如果你读 ofstream.write（）方法的文档，你会看到，它要求两个参数：

1. 在指针数据块的内容写入;




2. 一个整数值，再presenting在字节大小，这一块的

这个声明只是给这两条信息，以 ofstream.write（）：

  file.write（reinter pret_cast＆LT;为const char *＆GT;（试验＃）的sizeof（NUM））;
 

试验＃是数据块的地址（在这种情况下，仅仅是一个整数变量），的sizeof（NUM）是该块（如Windows平台上的4个字节）的大小。

I have a very simple question, which happens to be hard for me since this is the first time I tried working with binary files, and I don't quite understand them. All I want to do is write an integer to a binary file.

Here is how I did it:

#include <fstream>
using namespace std;
int main () {
    int num=162;
    ofstream file ("file.bin", ios::binary);
    file.write ((char *)&num, sizeof(num));
    file.close (); 
    return 0;
}

Could you please tell me if I did something wrong, and what?

The part that is giving me trouble is line with file.write, I don't understand it.

Thank you in advance.

解决方案

The part that is giving me trouble is line with file.write, I don't understand it.

If you read the documentation of ofstream.write() method, you'll see that it requests two arguments:

1. a pointer to a block of data with the content to be written;

2. an integer value representing the size, in bytes, of this block.

This statement just gives these two pieces of information to ofstream.write():

file.write(reinterpret_cast<const char *>(&num), sizeof(num));

&num is the address of the block of data (in this case just an integer variable), sizeof(num) is the size of this block (e.g. 4 bytes on Windows platforms).

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