converting c++ class to a byte array

问题

It is possible to convert the following Student class to a binary file by writing it with ios::binary

#include <fstream>
#include <iostream>
using namespace std;

class Student{
    public:
        char name[40], address[120], gender;
        double age;
        bool is_blabla;
};

int main() {

    Student one;
    strcpy(one.name, "Cancan Can");
    strcpy(one.address, "example example exampla");
    one.gender = 'M';
    one.age = 25;
    one.is_blabla = true;

    ofstream ofs("fifthgrade.ros", ios::binary);
    ofs.write((char *)&one, sizeof(one));

    Student two;
    ifstream ifs("fifthgrade.ros", ios::binary);
    ifs.read((char *)&two, sizeof(two));

    // check if the data is OK
    cout << "Student Name: " << two.name << endl;


    return 0;
}

The file looks like as follows:

http://i.imgur.com/GfkheWs.png

So how can I do the same thing to convert the class to a byte (or say char*) array in this case?

Edit: But in this case, Let's say I have a class having methods. The answers you gave is telling me to write my own bitwise operators to serialize a complex class. Can you refer to a good source teaching how it can be done or a small sample/example for it?

Edit2: I have to avoid using extra libraries because I may deserialize the serialized code on a machine/compiler that I cannot import most of the libraries (for example I will try to deserialize the code on an nvcc compiled code).

Example dummy class would be like this:

class Student{
    public:
        char name[40], address[120], gender;
        double age;
        bool is_blabla;

        void set_values (int,int);
        int doubleage() {return age*2;}
};

回答1:

Just use a std::stringstream rather than std::ofstream.

Then, access the char* using std::stringstream::str() (This return's a std::string, on which you can retrieve a char* using std::string::c_str()).

回答2:

All objects can be accessed as their constituent chars, just get a pointer and cast it.

Still, even if you want to write it to a binary file (in contrast to writing a textual representation), do not just write its raw bytes:

The object might contain a number of non-value-bits (Like padding, unused buffers, whatever). Those might contain previously recorded information, which you should not leak.
The object might contain pointers, handles or other references to additional data. Those cannot be recovered from a bitwise-copy, as the information they indicate is the important part and won't be there.

BTW: ios::binary just disables translation of text-files. (Identity on Unixoids, newline-conversion on windows...)

回答3:

If you need a more enhanced way, consider the following ways:

Boost.Serialization (http://www.boost.org/doc/libs/1_56_0/libs/serialization/doc/index.html)
Google Protocol Buffers (https://developers.google.com/protocol-buffers/)

来源：https://stackoverflow.com/questions/26527317/converting-c-class-to-a-byte-array

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c++

arrays

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serialization

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