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fstream 到 const char *

发布于 2024-09-28 19:49:23 字数 69 浏览 4 评论 0原文

我想要做的是读取一个名为“test.txt”的文件，然后让该文件的内容为 const char * 类型。一个人会怎样做呢？

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执笔绘流年 2024-10-05 19:49:23

#include <string>
#include <fstream>

int main()
{
   std::string line,text;
   std::ifstream in("test.txt");
   while(std::getline(in, line))
   {
       text += line + "\n";
   }
   const char* data = text.c_str();
}

注意不要显式调用数据删除

#include <string>
#include <fstream>

int main()
{
   std::string line,text;
   std::ifstream in("test.txt");
   while(std::getline(in, line))
   {
       text += line + "\n";
   }
   const char* data = text.c_str();
}

Be careful not to explicitly call delete on data

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幻想少年梦 2024-10-05 19:49:23

您不太可能真的想这样做。文件的内容（可能是文本或二进制数据）不太可能表示指向体系结构上的字符的（有效）指针，因此将其[内容]表示为 并没有真正的意义常量字符*。

您可能想要的是将文件的内容加载到内存中，然后将指针（类型为 const char*）存储到给定块的开头。实现这一目标的一种方法是：

#include <sstream>
#include <fstream>
// ...
{
    std::ostringstream sstream;
    std::ifstream fs("test.txt");
    sstream << fs.rdbuf();
    const std::string str(sstream.str());
    const char* ptr = str.c_str();
    // ptr is the pointer we wanted - do note that it's only valid
    // while str is valid (i.e. not after str goes out of scope)
}

It's highly unlikely you really want to do that. The contents of the file (which may be either text, or binary data) are unlikely to represent a (valid) pointer to a char on your architecture, so it is not really meaningful to represent it [the content] as a const char *.

What you may instead want is to load the contents of the file in memory, and then store a pointer (of type const char*) to the beginning of the given block. </pedantry> One way of achieving that:

#include <sstream>
#include <fstream>
// ...
{
    std::ostringstream sstream;
    std::ifstream fs("test.txt");
    sstream << fs.rdbuf();
    const std::string str(sstream.str());
    const char* ptr = str.c_str();
    // ptr is the pointer we wanted - do note that it's only valid
    // while str is valid (i.e. not after str goes out of scope)
}

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