提升序列化多个对象

Question

我正在使用二进制序列化一个类.我正在使用ios :: append以便将多个对象附加到此文件中.如何检索存储的所有对象？

这是我的测试类,它尝试多个序列化并检索它们.我评论了我没有得到正确数据的失败点.

using namespace std;
 class Data {
 public:
double get_latitude() const {
    return _latitude;
}

double get_longitude() const {
    return _longitude;
}

void set_latitude(double _latitude) {
    this->_latitude = _latitude;
}

void set_longitude(double _longitude) {
    this->_longitude = _longitude;
}
private:
double _latitude;
double _longitude;
friend class boost::serialization::access;
// When the class Archive corresponds to an output archive, the
// & operator is defined similar to <<.  Likewise, when the class Archive
// is a type of input archive the & operator is defined similar to >>.
template<class Archive>
void serialize(Archive & ar, const unsigned int version)
{
    ar & _latitude;
    ar & _longitude;
}
};

class DataTest: public CppUnit::TestFixture {
CPPUNIT_TEST_SUITE( DataTest);
CPPUNIT_TEST(testMultipleSaveData);
CPPUNIT_TEST_SUITE_END();

public:

void testMultipleSaveData() {
    Data data;
    data.set_latitude(1.0);
    data.set_longitude(2.0);
    saveData(data);
    Data secondData;
    secondData.set_latitude(5.0);
    secondData.set_longitude(6.0);
    saveData(secondData);
    Data returnData;
    Data return2Data;
    {
        // create and open an archive for input
        std::ifstream ifs("data.dat", ios::binary);
        boost::archive::binary_iarchive ia(ifs);
        // read class state from archive
        ia >> returnData;
        ia >> return2Data;
        // archive and stream closed when destructors are called
    }
    CPPUNIT_ASSERT_EQUAL(data.get_latitude(), returnData.get_latitude());
    CPPUNIT_ASSERT_EQUAL(data.get_longitude(), returnData.get_longitude());
    //Failure on next line
    CPPUNIT_ASSERT_EQUAL(secondData.get_latitude(), return2Data.get_latitude());
    CPPUNIT_ASSERT_EQUAL(secondData.get_longitude(), return2Data.get_longitude());
}

void saveData(Data data) {
    std::ofstream ofs("data.dat", ios::binary | ios::app);
    boost::archive::binary_oarchive oa(ofs);
    oa << data;
}

 };
 CPPUNIT_TEST_SUITE_REGISTRATION( DataTest);

Answer 1

决定添加另一个答案,以避免完全混乱.

您的问题是您序列化为单独的实例boost::archive::binary_oarchive.Boost Archive在文件的开头存储一些内部信息(我不会将其称为标题,因为Boost Serialization具有单独的标题来存储版本号),并且您在文件的开头和之间收到此信息的两个副本您的数据序列化.

Boost Archive不是为此类用途而设计的.甚至指定boost::archive::no_header如下:

boost::archive::text_oarchive oa(ofs, boost::archive::no_header);

没有帮助,因为此选项配置另一个包含版本号的标头.您需要序列化到Boost Archive的同一个实例.