Question

I want to make copies of an executable file itself multiple times.

I tried the following code:

#include <fstream>
#include <string>

int main() {
    std::ifstream from("main.exe", std::ios::binary);
    auto buf { from.rdbuf() };

    for(int x { 0 }; x <= 10; ++x) {
        std::string name { "main" + std::to_string(x) + ".exe" };

        std::ofstream out(name, std::ios::binary);
        out << buf;
        out.close();
    }

    from.close();
    return 0;
}

但是,它没有像我所期望的那样做工作(它没有重复复制可执行的工作)。见以下屏幕上的规模一栏:

我如何解决这一问题?

Answer 1

从投入文件流中读取数据。你们需要在复制档案后重新确定上游:

...

for (int x{ 0 }; x <= 10; ++x) {
    std::string name{ "main" + std::to_string(x) + ".exe" };

    std::ofstream out(name, std::ios::binary);
    out << buf;
    out.close();
    from.seekg(0, std::ios::beg); // need to go back to the start here
}

...

您只能使用<代码>std:filesystem。图书馆在这方面的标准功能:


int main() {
    std::filesystem::path input("main.exe");

    for (int x{ 0 }; x <= 10; ++x) {
        std::filesystem::path outfile("main" + std::to_string(x) + ".exe");

        std::filesystem::copy_file(input, outfile, std::filesystem::copy_options::overwrite_existing);
    }

    return 0;
}

Answer 2

在您第一次访问时,你读过了缓冲投入的全部内容之后,你的投入缓冲是空的。因此,您随后的通报也将提供空文。我建议将<代码>从上移至像样的休息室内:

#include <fstream>
#include <string>

int main() {

    for (int x{ 0 }; x <= 10; ++x) {
        std::ifstream from("main.exe", std::ios::binary);
        auto buf{ from.rdbuf() };
        std::string name{ "main" + std::to_string(x) + ".exe" };

        std::ofstream out(name, std::ios::binary);
        out << buf;
        out.close();
        from.close();
    }

    
    return 0;
}

Here s what you should get:

Answer 3

In the other answers the data will be read from the file multiple times (once per save).
This will happen if you create a new std::ifstream object inside the loop, and also happen if you use seekg to go to the beginning of the stream.

由于磁盘访问相对缓慢(与记忆存取相比),将 提高效率改为,然后将射入<>/strong> ,即 视需要。

下面的代码将文档本体的内容改为<编码>std:vector。然后多次撰写病媒的内容,以创建新的档案:

#include <string> #include <vector> #include <fstream> int main() { // Read the entire main.exe file into memory: const std::string inFilename{ "main.exe" }; std::ifstream inFile{ inFilename, std::ios_base::binary }; std::vector<char> inFileData{ std::istreambuf_iterator<char>(inFile), std::istreambuf_iterator<char>() }; inFile.close(); // Save it as many times as needed: for (int x{ 0 }; x <= 10; ++x) { std::string name{ "main" + std::to_string(x) + ".exe" }; std::ofstream outFile{ name, std::ios::binary }; outFile.write(inFileData.data(), inFileData.size()); outFile.close(); } }

Answer 4

第一份副本是完美的。我最好的猜测是,投入的缓冲随后是空的,因此所有连续复制件都是空的。

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