• 如何在C++中使用boost库序列化自定义class ？| serialize and deserialize a class in cpp with boost

    本文首发于个人博客https://kezunlin.me/post/6887a6ee/，欢迎阅读!

    serialize and deserialize a class in cpp

    Guide

    how to serialize string

    size + data

    The easiest serialization method for strings or other blobs with variable size is to serialize first the size as you serialize integers, then just copy the content to the output stream.

    When reading you first read the size, then allocate the string and then fill it by reading the correct number of bytes from the stream.

    with ostream/istream

    native way with ostream/istream for example class MyClass with height,width,name fields.

    class MyClass {
public:
	int height;
   int width;
   std::string name;
}

std::ostream& MyClass::serialize(std::ostream &out) const {
    out << height;
    out << ',' //number seperator
    out << width;
    out << ',' //number seperator
    out << name.size(); //serialize size of string
    out << ',' //number seperator
    out << name; //serialize characters of string
    return out;
}
std::istream& MyClass::deserialize(std::istream &in) {
    if (in) {
        int len=0;
        char comma;
        in >> height;
        in >> comma; //read in the seperator
        in >> width;
        in >> comma; //read in the seperator
        in >> len;  //deserialize size of string
        in >> comma; //read in the seperator
        if (in && len) {
            std::vector<char> tmp(len);
            in.read(tmp.data() , len); //deserialize characters of string
            name.assign(tmp.data(), len);
        }
    }
    return in;
}

    overload for operator<< and operator>>

    std::ostream& operator<<(std::ostream& out, const MyClass &obj)
{
    obj.serialize(out); 
    return out;
}

std::istream& operator>>(std::istream& in, MyClass &obj)
{
    obj.deserialize(in); 
    return in;
}

    with boost serialization

    archive file format

    • text: text_iarchive,text_oarchive field
    • xml: xml_iarchive,xml_oarchive, with BOOST_SERIALIZATION_NVP(field)
    • binary: binary_iarchive,binary_oarchive with stringstream or fstream.

    text archive

    change BOOST_SERIALIZATION_NVP(field) to field

    xml archive

    #include <boost/archive/text_iarchive.hpp> 
#include <boost/archive/text_oarchive.hpp> 
#include <boost/archive/xml_iarchive.hpp> 
#include <boost/archive/xml_oarchive.hpp> 
#include <boost/archive/binary_iarchive.hpp> 
#include <boost/archive/binary_oarchive.hpp> 
#include <iostream> 
#include <fstream> 
#include <sstream>

class Camera {

public:
	int id;
	std::string name;
	double pos;
};

namespace boost {
	namespace serialization {

		template<class Archive>
		void serialize(Archive& archive, Camera& cam, const unsigned int version)
		{
			archive & BOOST_SERIALIZATION_NVP(cam.id);
			archive & BOOST_SERIALIZATION_NVP(cam.name);
			archive & BOOST_SERIALIZATION_NVP(cam.pos);
		}

	} // namespace serialization
} // namespace boost

std::ostream& operator<<(std::ostream& cout, const Camera& cam)
{
	cout << cam.id << std::endl
		<< cam.name << std::endl
		<< cam.pos << std::endl;
	return cout;
}

void save()
{
	std::ofstream file("archive.xml");
	boost::archive::xml_oarchive oa(file);
	
	Camera cam;
	cam.id = 100;
	cam.name = "new camera";
	cam.pos = 99.88;

	oa & BOOST_SERIALIZATION_NVP(cam);
}

void load()
{
	std::ifstream file("archive.xml");
	boost::archive::xml_iarchive ia(file);
	Camera cam;
	ia & BOOST_SERIALIZATION_NVP(cam);
	std::cout << cam << std::endl;
}

void test_camera()
{
	save();
	load();
}

int main(int argc, char** argv)
{
	test_camera();
}

    binary archive

    void save_load_with_binary_archive()
{
	// binary archive with stringstream
	std::ostringstream oss;
	boost::archive::binary_oarchive oa(oss);

	Camera cam;
	cam.id = 100;
	cam.name = "new camera";
	cam.pos = 99.88;

	oa & (cam);

   # get binary content
	std::string str_data = oss.str();
	std::cout << str_data << std::endl;

	std::istringstream iss(str_data);
	boost::archive::binary_iarchive ia(iss);
	Camera new_cam;
	ia & (new_cam);
	std::cout << new_cam << std::endl;
}

    binary archive with poco SocketStream

    client.cpp

    void test_client()
{
	SocketAddress address("127.0.0.1", 9911);
	StreamSocket socket(address);
	SocketStream stream(socket);
	//Poco::StreamCopier::copyStream(stream, std::cout);

	boost::archive::binary_oarchive oa(stream);
	Camera cam;
	cam.id = 100;
	cam.name = "new camera";
	cam.pos = 99.88;

	oa & (cam);
}

    server.cpp

    void run()
	{
		Application& app = Application::instance();
		app.logger().information("Request from " + this->socket().peerAddress().toString());
		try
		{
			SocketStream stream(this->socket());
			//Poco::StreamCopier::copyStream(stream, std::cout);

			boost::archive::binary_iarchive ia(stream);
			Camera new_cam;
			ia & (new_cam);
			std::cout << new_cam << std::endl;
		}
		catch (Poco::Exception& exc)
		{
			app.logger().log(exc);
		}
	}

    notes on std::string

    Even know you have seen that they do the same, or that .data() calls .c_str(), it is not correct to assume that this will be the case for other compilers. It is also possible that your compiler will change with a future release.

    2 reasons to use std::string:

    std::string can be used for both text and arbitrary binary data.

    //Example 1
//Plain text:
std::string s1;
s1 = "abc";
s1.c_str();

//Example 2
//Arbitrary binary data:
std::string s2;
s2.append("abb", 6);
s2.data();

    boost archive style

    intrusive

    • private template<class Archive> void serialize(Archive& archive, const unsigned int version)
    • friend class boost::serialization::access;
    class Camera {

public:
	int id;
	std::string name;
	double pos;

private:
	friend class boost::serialization::access;
	template<class Archive>
	void serialize(Archive& archive, const unsigned int version)
	{
		archive & BOOST_SERIALIZATION_NVP(id);
		archive & BOOST_SERIALIZATION_NVP(name);
		archive & BOOST_SERIALIZATION_NVP(pos);
	}
};

    non-intrusive

    class Camera {

public:
	int id;
	std::string name;
	double pos;
};


namespace boost {
	namespace serialization {

		template<class Archive>
		void serialize(Archive& archive, Camera& cam, const unsigned int version)
		{
			archive & BOOST_SERIALIZATION_NVP(cam.id);
			archive & BOOST_SERIALIZATION_NVP(cam.name);
			archive & BOOST_SERIALIZATION_NVP(cam.pos);
		}

	} // namespace serialization
} // namespace boost

    boost archive type

    shared_ptr

    boost::shared_ptr<T> instead of std::shared_prt<T>
    and

    #include <boost/serialization/shared_ptr.hpp>

    Reference

    History

    • 20180128: created.
    • 20180129: add intrusive,non-intrusive part.

    Copyright
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  • 原文地址：https://www.cnblogs.com/kezunlin/p/11840592.html
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