How to serialize a class with a boost::dynamic_bitset member?
#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;
}
Compiling gives an error (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’
dynamic_bitset<> is not serializable, as you've found out (std::bitset<N> is different type).
Not to worry, though, you can add it without too much effort:
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);
}
} }
This works e.g. 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);
}
}
Note that if you can't afford to copy the blocks vector, it's equally easy to add serialization directly on the m_bits level, but that requires intrusive changes (friend access required at a minimum).
Such a thing would easily be added to boost in a pull request.