[英]Boost serialization with pointers and non-default constructor
你會如何使用boost :: serialization序列化/反序列化這個類?
#include <vector>
struct Foo {
struct Bar {
std::vector<int> * data; // Must point to Foo::data
Bar( std::vector<int> * d ) : data(d) { }
};
std::vector<int> data;
std::vector<Bar> elements;
Foo() {
// do very time consuming calculation to populate "data" and "elements"
}
};
當從序列化數據加載對象時,不得執行Foo中的構造函數,但如果對象是默認構造的,則必須對構造函數進行求值。
可以向Bar添加默認構造函數,但在序列化之后,Foo :: Bar :: data必須指向Foo :: data。
編輯:以下是我的嘗試的非工作實現
這是我基於@Matthieu提示的嘗試。 問題是,當我反序列化Foo時,我在Foo :: data和Foo :: elements中沒有得到任何元素。
struct Foo {
struct Bar {
std::vector<int> * data;
Bar( ) : data( 0 ) { }
Bar( std::vector<int> * d ) : data(d) { }
template<class Archive>
void serialize(Archive & ar, const unsigned int version) {
ar & data;
}
};
std::vector<int> data;
std::vector<Bar> elements;
Foo() {
std::cerr << "Running default constructor" << std::endl;
data.push_back(1);
data.push_back(2);
data.push_back(3);
data.push_back(4);
data.push_back(5);
elements.push_back( Bar( &data ) );
elements.push_back( Bar( &data ) );
elements.push_back( Bar( &data ) );
}
template<class Archive>
Foo( Archive & ar ) {
ar >> data; // is this corrent?
ar >> elements;
}
private:
BOOST_SERIALIZATION_SPLIT_MEMBER();
friend class boost::serialization::access;
template<class Archive>
void save(Archive & ar, const unsigned int version) const {
const std::vector<int> * data_ptr = &data;
// should data be seriliazed as pointer...
// it is used as a pointer in Bar
ar << data_ptr;
ar << elements;
}
};
int main(int argc, const char *argv[])
{
#if 0
// serialize
Foo foo;
boost::archive::text_oarchive oar(std::cout);
oar << foo;
#else
// deserialize
boost::archive::text_iarchive oar(std::cin);
Foo foo(oar);
#endif
std::cerr << foo.data.size() << std::endl;
std::cerr << foo.elements.size() << std::endl;
std::cerr << (&foo.data) << std::endl;
for( const auto& a : foo.data )
std::cerr << a << " ";
std::cerr << std::endl;
for( const auto& a : foo.elements)
std::cerr << a.data << " ";
std::cerr << std::endl;
return 0;
}
文檔中有一節描述如何(de)使用非默認構造函數序列化類。 看到這里 。
基本上,您必須在命名空間boost::serialization
實現名為save_construct_data
和load_construct_data
兩個函數,以寫出並讀入用於構造類實例的數據。 然后,您可以使用重建Foo
對象所需的參數從load_construct_data
函數調用Foo
的非默認構造函數。
這是一個基於您更新的代碼的工作示例:
請注意,我已經使用shared_ptr
來澄清由Foo和Bar序列化的data
成員引用相同的東西。
#include <vector>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/serialization/vector.hpp>
#include <boost/serialization/shared_ptr.hpp>
#include <boost/serialization/scoped_ptr.hpp>
#include <boost/shared_ptr.hpp>
#include <iostream>
#include <sstream>
struct Foo {
struct Bar {
boost::shared_ptr< std::vector<int> > data; // Must point to Foo::data
Bar( boost::shared_ptr< std::vector<int> > d ) : data(d) { }
template<class Archive>
void serialize(Archive & ar, const unsigned int version)
{
// ** note that this is empty **
}
};
boost::shared_ptr< std::vector<int> > data;
std::vector<Bar> elements;
Foo() : data( new std::vector<int>() ) {
std::cerr << "Running default constructor" << std::endl;
data->push_back(1);
data->push_back(2);
data->push_back(3);
data->push_back(4);
data->push_back(5);
elements.push_back( Bar( data ) );
elements.push_back( Bar( data ) );
elements.push_back( Bar( data ) );
}
template<class Archive>
void serialize(Archive & ar, const unsigned int version)
{
// ** note that this is empty **
}
Foo(
boost::shared_ptr< std::vector<int> > const & data_,
std::vector<Bar> const & elements_ ) : data( data_ ), elements( elements_ )
{
std::cout << "cheap construction" << std::endl;
}
};
namespace boost { namespace serialization {
template<class Archive>
inline void save_construct_data(
Archive & ar, const Foo * foo, const unsigned int file_version
){
ar << foo->data << foo->elements;
}
template<class Archive>
inline void load_construct_data(
Archive & ar, Foo * foo, const unsigned int file_version
){
boost::shared_ptr< std::vector<int> > data;
std::vector<Foo::Bar> elements;
ar >> data >> elements;
::new(foo)Foo(data, elements);
}
template<class Archive>
inline void save_construct_data(
Archive & ar, const Foo::Bar * bar, const unsigned int file_version
){
ar << bar->data;
}
template<class Archive>
inline void load_construct_data(
Archive & ar, Foo::Bar * bar, const unsigned int file_version
){
boost::shared_ptr< std::vector<int> > data;
ar >> data;
::new(bar)Foo::Bar(data);
}
}}
int main()
{
std::stringstream ss;
{
boost::scoped_ptr< Foo > foo( new Foo() );
std::cout << "size before serialization is: " << foo->data->size() << std::endl;
boost::archive::text_oarchive oa(ss);
oa << foo;
}
{
boost::scoped_ptr< Foo > foo;
boost::archive::text_iarchive is(ss);
is >> foo;
std::cout << "size after deserialization is: " << foo->data->size() << std::endl;
}
return 0;
}
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