I would like to serialize a custom class containing an boost::multiprecision::mpfr_float as a member. It says here in the Boost.Serialization documentation that a type T
is serializable iff at least one of 5 properties is true, and here at the Multiprecision documentation that the number
class has pass-through support which requires the underlying backend to be serializable.
For Boost.Multiprecision's mpfr_float
type, I know:
- It is not a primitive type.
- It is a class type, but it doesn't have the
serialize
function(s) defined. - It is not a pointer to a Serializable type.
- It is not a reference to a Serializable type.
- It is not a native C++ array of Serializable type.
So, it looks like if I want to serialize the mpfr_float type, I must provide the serialize
function for that type.
My question is this: How can I extend the mpfr_float
type to be serializable by writing the serialize
function myself? I think I need to access the mpfr backend, and play with the underlying data, and I am unsure how to proceed. Tips from someone with experience Boost serializing previously-unserialized classes would be greatly appreciated.
Concluding Solution
Based on the reply from sehe, I arrived at a solution which round-trips just fine with precisions 100 and 1000:
namespace boost { namespace serialization { // insert this code to the appropriate namespaces
/**
Save a mpfr_float type to a boost archive.
*/
template <typename Archive>
void save(Archive& ar, ::boost::multiprecision::backends::mpfr_float_backend<0> const& r, unsigned /*version*/)
{
std::string tmp = r.str(0, std::ios::fixed);// 0 indicates use full precision
ar & tmp;
}
/**
Load a mpfr_float type from a boost archive.
*/
template <typename Archive>
void load(Archive& ar, ::boost::multiprecision::backends::mpfr_float_backend<0>& r, unsigned /*version*/)
{
std::string tmp;
ar & tmp;
r = tmp.c_str();
}
} } // re: namespaces
This solution addresses the need from item (2) above, which indicated the need to add the serialize
functions. Thanks for the help.