提升序列化 std::unique_ptr 支持

Question

boost 序列化库是否支持 std::unique_ptr 的序列化？ 我试图编译下面的代码，但如果我包括 boost::archive::text_oarchive oa(ofs); oa 行，

编译器（btw gcc4.7 with -std=c++11 flag）抛出错误

/usr/include/boost/serialization/access.hpp:118:9: 错误：‘class std::unique_ptr’没有名为‘serialize’的成员

#include <iostream>
#include <memory>
#include <fstream>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
class MyDegrees
{
public:
  void setDeg(int d){deg = d;}
  int getDeg()const {return deg;}
private:
  friend class boost::serialization::access;
    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    { ar & deg; }
  int deg;
};
class gps_position
{
private:
    friend class boost::serialization::access;
    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    { ar & degrees; }
    std::unique_ptr<MyDegrees> degrees;
public:
    gps_position(): degrees(std::unique_ptr<MyDegrees>(new MyDegrees)){};
    void setDeg(int d){degrees->setDeg(d);}
    int getDeg() const {return degrees->getDeg();}
};
int main()
{
    std::ofstream ofs("filename");
    gps_position g;
    g.setDeg(45);
    std::cout<<g.getDeg()<<std::endl;
    {// compiler error, fine if commented out
        boost::archive::text_oarchive oa(ofs); oa << g;
    }
  return 0;
}

Answer 1

我不确定如何解释 this list，但似乎在 1.48 之后的某个时间添加了对此的支持。我使用的是 1.58，它已包含在内。只是

#include <boost/serialization/unique_ptr.hpp>

然后它将按如下方式工作：

#include <memory>

#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/serialization/unique_ptr.hpp>

#include <fstream>

class Point
{
public:
    Point() { }

    float x = 1.;
    float y = 2.;
    float z = 3.;

private:
    friend class boost::serialization::access;

    template<class TArchive>
    void serialize(TArchive & archive, const unsigned int version)
    {
        archive & x;
        archive & y;
        archive & z;
    }
};

void ValidUniquePointer()
{
    std::unique_ptr<Point> p(new Point());

    std::ofstream outputStream("test.txt");
    boost::archive::text_oarchive outputArchive(outputStream);
    outputArchive << p;
    outputStream.close();

    // read from a text archive
    std::unique_ptr<Point> pointRead;
    std::ifstream inputStream("test.txt");
    boost::archive::text_iarchive inputArchive(inputStream);
    inputArchive >> pointRead;

    std::cout << pointRead->x << " " << pointRead->y << " " << pointRead->z << std::endl;

}

void NullUniquePointer()
{
    std::unique_ptr<Point> p;

    std::ofstream outputStream("test.txt");
    boost::archive::text_oarchive outputArchive(outputStream);
    outputArchive << p;
    outputStream.close();

    // read from a text archive
    std::unique_ptr<Point> pointRead;
    std::ifstream inputStream("test.txt");
    boost::archive::text_iarchive inputArchive(inputStream);
    inputArchive >> pointRead;

    if(pointRead != nullptr) {
        std::cout << pointRead->x << " " << pointRead->y << " " << pointRead->z << std::endl;
    }
    else {
        std::cout << "Pointer is null!" << std::endl;
    }

}

int main()
{
    ValidUniquePointer();
    NullUniquePointer();
    return 0;
}

Answer 2

正如pmr 所提到的，我设法提出了以下解决方案，乍一看，一切正常。希望有人能发现它有用：

#include <iostream>
#include <memory>
#include <fstream>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
namespace boost { 
namespace serialization {

template<class Archive, class T>
inline void save(
    Archive & ar,
    const std::unique_ptr< T > &t,
    const unsigned int /*file_version*/
){
    // only the raw pointer has to be saved
    const T * const base_pointer = t.get();
    ar & BOOST_SERIALIZATION_NVP(base_pointer);
}
template<class Archive, class T>
inline void load(
    Archive & ar,
    std::unique_ptr< T > &t,
    const unsigned int /*file_version*/
){
    T *base_pointer;
    ar & BOOST_SERIALIZATION_NVP(base_pointer);
    t.reset(base_pointer);
}
template<class Archive, class T>
inline void serialize(
    Archive & ar,
    std::unique_ptr< T > &t,
    const unsigned int file_version
){
    boost::serialization::split_free(ar, t, file_version);
}
} // namespace serialization
} // namespace boost

class MyDegrees
{
public:
  void setDeg(int d){deg = d;}
  int getDeg()const {return deg;}
private:
  friend class boost::serialization::access;
    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    { ar & deg; }
  int deg;
};
class gps_position
{
private:
    friend class boost::serialization::access;
    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    { ar & degrees;  }
    std::unique_ptr<MyDegrees> degrees;
public:
    gps_position(): degrees(std::unique_ptr<MyDegrees>(new MyDegrees)){};
    void setDeg(int d){degrees->setDeg(d);}
    int getDeg() const {return degrees->getDeg();}
};
int main()
{
    std::ofstream ofs("filename");
    gps_position g;
    g.setDeg(45);
    std::cout<<g.getDeg()<<std::endl;
    { boost::archive::text_oarchive oa(ofs); oa << g; }
    gps_position newg;
    {
        std::ifstream ifs("filename");
        boost::archive::text_iarchive ia(ifs);
        ia >> newg;
        std::cout<<newg.getDeg()<<std::endl;
    }
  return 0;
}

Answer 3

最新版本的 boost 序列化支持所有 std 智能指针类型。

Answer 4

Boost 现在支持智能指针，您可以为 Unique_Ptr #include 头文件。

 #include <boost/serialization/unique_ptr.hpp>

Answer 5

不，没有开箱即用的适配。您需要自己提供一个非侵入式适配器。请参阅tutorial here 了解如何执行此操作。