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Accepted
Alrott SlimRG
Asked:2020-10-06 14:09:14 +0000 UTC2020-10-06 14:09:14 +0000 UTC

序列化 std::string

  • 772

实际上，有一个类：

class MyClass{
   const uint64_t UUID;
   const std::string Version;
   const uint32_t blocksize;
}

如何将其写入文件？

c++

1 个回答

  1. Best Answer

    好吧，我会做这样的事情......我重新制作它是struct为了不弄乱访问，并将它const从字段中删除 - 因为编写常量字段很容易，但读取不是：你不应该更改常量对象。除非在构造函数中完成读取，例如初始化......

    struct MyClass
{

    MyClass (uint64_t uuid, const char * s, uint32_t b):UUID(uuid),
             Version(s),blocksize(b){}

    uint64_t UUID;
    std::string Version;
    uint32_t blocksize;

    ostream& write(ostream& os) const;
    istream& read(istream& is);
};

ostream& MyClass::write(ostream& os) const
{
    os.write((char*)&UUID,sizeof(UUID));
    size_t s = Version.size();
    os.write((char*)&s,sizeof(s));
    os.write(Version.c_str(),s);
    os.write((char*)&blocksize,sizeof(blocksize));
    return os;
}

istream& MyClass::read(istream& is)
{
    is.read((char*)&UUID,sizeof(UUID));
    size_t s;
    is.read((char*)&s,sizeof(s));
    Version.resize(s);
    is.read(Version.data(),s);
    is.read((char*)&blocksize,sizeof(blocksize));
    return is;
}

    好吧，作为一个使用示例：

    int main(int argc, const char * argv[])
{
    MyClass a(1,"xyz",3);
    MyClass b(4,"s",8);

    ofstream out("data",ios::binary);
    a.write(out);
    out.close();

    ifstream in("data",ios::binary);
    b.read(in);
    in.close();

    cout << b.UUID << endl;
    cout << b.Version << endl;
    cout << b.blocksize << endl;
}

    自己检查一切是否正常。

    作为不想使用的编译器的一个选项.data()-

    Version.resize(s);
is.read(Version.data(),s);

    取而代之

    char * buf = new char[s];
is.read(buf,s);
Version.assign(buf,buf+s);
delete[] buf;
    • 2

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