serialize/deserialize user defined class variable? - serialization

Question

Suppose I have two classes:
class1 {
int m_i;
std::string m_s;
};
class2 {
int m_i2;
class1 *m_ptr;
};
Now, I want to send a class2 variable over network, and want to use any of the libraries that does serialization.(Protocol-buffers, Thrift, MessagePack..)
Which one can I use?(note the class1* m_ptr)

Answer 1

You could use thrift for this.
the definition would look something like
struct class1 {
1: required i32 m_i;
2: required string m_s;
}
struct class2 {
1: required i32 m_i2;
2: optional class1 m_ptr;
}
You would like to read this excellent guide
http://diwakergupta.github.com/thrift-missing-guide/
and to get clarity on concern about the "pointer" issue that you mentioned in the question,read the section on "How are nested structs initialized?" in the above guide.

Answer 2

Using google protocol buffers, you would need a .proto file (say test.proto) like:
package serialisation; // puts this in namespace serialisation
message class1 {
required int32 m_i = 1;
required bytes m_s = 2;
}
message class2 {
required int32 m_i2 = 1;
optional class1 m_ptr = 2;
}
Using C++, once you run the protoc compiler against this, you end up with test.pb.cc and test.pb.h
You can then use these like:
#include <string>
#include "test.pb.h"
struct class1 {
int m_i;
std::string m_s;
};
struct class2 {
int m_i2;
class1 *m_ptr;
};
int main() {
class2 second_class;
second_class.m_i2 = 2;
second_class.m_ptr = new class1;
second_class.m_ptr->m_i = 1;
second_class.m_ptr->m_s = "one";
// Serialise class 2
serialisation::class2 serialisable_second_class;
serialisable_second_class.set_m_i2(second_class.m_i2);
if (second_class.m_ptr) {
serialisation::class1* serialisable_first_class = serialisable_second_class.mutable_m_ptr();
serialisable_first_class->set_m_i(second_class.m_ptr->m_i);
serialisable_first_class->set_m_s(second_class.m_ptr->m_s);
}
std::string serialised(serialisable_second_class.SerializeAsString());
// Parse class 2
serialisation::class2 parsed_second_class;
parsed_second_class.ParseFromString(serialised);
class2 retrieved_second_class;
retrieved_second_class.m_i2 = parsed_second_class.m_i2();
if (parsed_second_class.has_m_ptr()) {
retrieved_second_class.m_ptr = new class1;
retrieved_second_class.m_ptr->m_i = parsed_second_class.m_ptr().m_i();
retrieved_second_class.m_ptr->m_s = parsed_second_class.m_ptr().m_s();
} else {
retrieved_second_class.m_ptr = nullptr;
}
return 0;
}
Note, for the sake of brevity I'm not doing any error checking or exception handling here - this would be needed in production code. I'm also not managing the lifetime of the class1 pointer.