以二进制模式将字符串写入文件

Question

所以我正在使用这段代码来编写文件(现在只是测试,我稍后会编写一个关卡编辑器):

 
int main()
{
    ofstream file("level.bin", ios::binary);
    int ents = 1; //number of entites
    file.write((char*)&ents, sizeof(int));
    float x = 300; //x and y coords
    float y = 500;
    file.write((char*)&x, sizeof(float));
    file.write((char*)&y, sizeof(float));
    int imglength = 12; //strings are prefixed by a length
    file.write((char*)&imglength, sizeof(int));
    string img = "platform.png"; //string
    file.write(img.c_str(), sizeof(img.c_str()));
    cout << "wrote\n";
    return 0;
}

我用来加载它的代码是这样的:

 


void SceneManager::LoadScene(std::string filename)
{
    std::ifstream file(filename.c_str(), std::ios::binary);
    int ents;
    file.read((char*)&ents, sizeof(int));
    std::cout << ents << std::endl;
    for(int i = 0; i < ents; i++)
    {
        //read x and y coords
        float x;
        float y;
        file.read((char*)&x, sizeof(float));
        file.read((char*)&y, sizeof(float));
        std::cout << x << " " << y << std::endl;
        int imglength;
        file.read((char*)&imglength, sizeof(int));
        std::cout << imglength << std::endl;
        std::stringstream ss;
        for(int k = 0; k <= imglength; k++)
        {
            //read string
            char c;
            file.read((char*)&c, sizeof(char));
            ss << c;
        }
        std::string image = ss.str();
        std::cout << image << std::endl;
        phys_static ent;
        Def edef;
        edef.SetVal("x", x);
        edef.SetVal("y", y);
        edef.SetString("image", image);
        ent.init(edef);
        AddEntity(ent);
    }
    file.close();
}

除了字符串加载,一切正常.我希望我写错了,因为它代替了platform.png,它显示了加载图像时的plattttttttt和错误.我也在字符串前面加上它的长度.将字符串写入二进制文件的正确方法是什么？相关的是什么

Answer 1

错误在这一行:

file.write(img.c_str(), sizeof(img.c_str()));

你想要的是:

file.write(img.c_str(), img.size());

在sizeof(img.c_str())返回4,因为sizeof(char *)(的返回类型c_str())是4你的平台上.这意味着前4个字符被写入,然后你只得到一些垃圾.