如何序列化boost::dynamic_bitset？

Question

如何用 boost::dynamic_bitset 成员序列化 class？

#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/dynamic_bitset.hpp>
#include <boost/serialization/bitset.hpp>
#include <sstream>

class A
{
    friend class boost::serialization::access;
    boost::dynamic_bitset<> x;
    template<class Archive>
    void serialize(Archive & ar, const unsigned int){
        ar & x;
    }
};

int main()
{
    A a;
    std::stringstream ss;
    boost::archive::text_oarchive oa(ss);
    oa << a;
    return 0;
}

编译报错(boost 1.57)

In file included from /usr/include/boost/serialization/extended_type_info_typeid.hpp:37:0,
                 from /usr/include/boost/archive/detail/oserializer.hpp:38,
                 from /usr/include/boost/archive/detail/interface_oarchive.hpp:23,
                 from /usr/include/boost/archive/detail/common_oarchive.hpp:22,
                 from /usr/include/boost/archive/basic_text_oarchive.hpp:32,
                 from /usr/include/boost/archive/text_oarchive.hpp:31,
                 from dynamic_bitset_setial.cpp:1:
/usr/include/boost/serialization/access.hpp: In static member function ‘static void boost::serialization::access::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive, T = boost::dynamic_bitset<>]’:
/usr/include/boost/serialization/serialization.hpp:69:5:   instantiated from ‘void boost::serialization::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive, T = boost::dynamic_bitset<>]’
/usr/include/boost/serialization/serialization.hpp:128:9:   instantiated from ‘void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive, T = boost::dynamic_bitset<>]’
/usr/include/boost/archive/detail/oserializer.hpp:148:5:   instantiated from ‘void boost::archive::detail::oserializer<Archive, T>::save_object_data(boost::archive::detail::basic_oarchive&, const void*) const [with Archive = boost::archive::text_oarchive, T = boost::dynamic_bitset<>]’
dynamic_bitset_setial.cpp:25:1:   instantiated from here
/usr/include/boost/serialization/access.hpp:118:9: error: ‘class boost::dynamic_bitset<>’ has no member named ‘serialize’

Answer 1

正如您所发现的，

dynamic_bitset<> 不可序列化（std::bitset<N> 是不同的类型）。

不过不用担心，您可以毫不费力地添加它：

namespace boost { namespace serialization {

    template <typename Ar, typename Block, typename Alloc>
        void save(Ar& ar, dynamic_bitset<Block, Alloc> const& bs, unsigned) {
            size_t num_bits = bs.size();
            std::vector<Block> blocks(bs.num_blocks());
            to_block_range(bs, blocks.begin());

            ar & num_bits & blocks;
        }

    template <typename Ar, typename Block, typename Alloc>
        void load(Ar& ar, dynamic_bitset<Block, Alloc>& bs, unsigned) {
            size_t num_bits;
            std::vector<Block> blocks;
            ar & num_bits & blocks;

            bs.resize(num_bits);
            from_block_range(blocks.begin(), blocks.end(), bs);
            bs.resize(num_bits);
        }

    template <typename Ar, typename Block, typename Alloc>
        void serialize(Ar& ar, dynamic_bitset<Block, Alloc>& bs, unsigned version) {
            split_free(ar, bs, version);
        }

} }

这有效，例如Live On Coliru

int main() {
    A a;
    for (int i=0; i<128; ++i)
        a.x.resize(11*i, i%2);

    std::stringstream ss;
    {
        boost::archive::text_oarchive oa(ss);
        oa << a;
    }
    std::cout << ss.str();
    {
        boost::archive::text_iarchive ia(ss);
        A b;
        ia >> b;

        assert(a.x == b.x);
    }
}

请注意，如果您无力复制块向量，直接在 m_bits 级别添加序列化同样容易，但这需要进行侵入性更改（至少需要好友访问权限）。

这样的东西很容易被添加到拉取请求中。

更新

Answer 2

我继续 filed the pull request 为 Boost Dynamic Bitset 添加序列化支持

Serialization using the public interface isn't optimal as to_block_range()/from_block_range() require copying of m_bits (and subsequent resize()).

I added a generic implementation to Boost Dynamic Bitset. The changes merge cleanly against develop or master (1_58_0).

Changes

Implementation added with

minimal intrusiveness, only a nested friend (class serialization_impl;) has been forward declared to "key-hole" the required friend access through

This class, as well as the actual ADL hook for Boost Serialization are implemented in a separate header (dynamic_bitset/serialization.hpp, similar to other boost libraries with serialization support).

This means that zero dependencies on Boost Serialization stuff exists unless boost/dynamic_bitset/serialization.hpp is actually included

Zero copy is achieved (leveraging std::vector<Block>'s builtin support in Boost Serialization)

Tests

The second commit in the pull request adds tests for this feature. I'm not sure how to add the dyn_bitset_unit_tests5.cpp to the Jamfile. I suppose something else must be done to ensure linking to Boost System and Boost Serialization. I have run the tests myself using a simple wrapper:
#include <modular-boost/libs/dynamic_bitset/dyn_bitset_unit_tests5.cpp>

int main() {
    test_main(0, nullptr);
}
Which can then be compiled and run with e.g.
g++ main.cpp -lboost_system -lboost_serialization && ./a.out
No output means no errors.

如何序列化boost::dynamic_bitset？

How to serialize boost::dynamic_bitset?

c++

boost

boost-dynamic-bitset

更新

Changes

Tests