Question

For a client/server application I need to send and recive c++ objects. I don’t need the corresponding classes to do anything fancy but want to have maximal performance (regarding network traffic and computation). So I though of simply transferring them as binary strings. Basicly I want to be able to do the following

//Create original object
MyClass oldObj();

//save to char array
char* save = new char[sizeof(MyClass)];
memcpy(save, &oldObj, sizeof(MyClass));

//Somewhere of course there would be the transfer to the client/server

//Read back from char array
MyClass newObj();
memcpy(&newObj, save, sizeof(MyClass));

My question: What does my class need to fullfill in order for this to work?
Naturaly Pointers as members won’t work when transferring to another application. But is it sufficient that my Class is considered POD (in c++03 and/or c++11) and does not have any pointers or equivalents (like STL containers) as members?

Answer 1

Both machines need to:

1. Have the same Endianess (for int)
2. The same floating point representation (double)
3. The same size for all types.
4. The Same compiler
5. The Same flags used to build the application.
6. Pointers dont transfer well.

BUT the network is going to be the slowest part here.
The cost of serializing most objects is going to be irrelevant compared to the cost of transfer. Of course the bigger your object the higher the cost but it takes a while before it is significant to make a dent.

The higher cost of maintenance is also you should factor in.