Wrapper Functions for Optimization

This section introduces wrapper functions to optimize the serialization process. These functions mark objects to allow Boost.Serialization to apply certain optimization techniques.

#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/array.hpp>
#include <iostream>
#include <sstream>

using namespace boost::archive;

std::stringstream ss;

void save()
{
  text_oarchive oa{ss};
  boost::array<int, 3> a{{0, 1, 2}};
  oa << a;
}

void load()
{
  text_iarchive ia{ss};
  boost::array<int, 3> a;
  ia >> a;
  std::cout << a[0] << ", " << a[1] << ", " << a[2] << '\n';
}

int main()
{
  save();
  load();
}

Example 64.14 uses Boost.Serialization without any wrapper function. The example creates and writes the value 22 serialization::archive 11 0 0 3 0 1 2 to the string. Using the wrapper function boost::serialization::make_array(), the value written can be shortened to the following string: 22 serialization::archive 11 0 1 2.

#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/serialization/array.hpp>
#include <array>
#include <iostream>
#include <sstream>

using namespace boost::archive;

std::stringstream ss;

void save()
{
  text_oarchive oa{ss};
  std::array<int, 3> a{{0, 1, 2}};
  oa << boost::serialization::make_array(a.data(), a.size());
}

void load()
{
  text_iarchive ia{ss};
  std::array<int, 3> a;
  ia >> boost::serialization::make_array(a.data(), a.size());
  std::cout << a[0] << ", " << a[1] << ", " << a[2] << '\n';
}

int main()
{
  save();
  load();
}

boost::serialization::make_array() expects the address and the length of an array. However, because it is known in advance, the length does not need to be serialized as part of the array.

boost::serialization::make_array() can be used whenever classes such as std::array or std::vector contain an array that can be serialized directly. Additional member variables, which would normally also be serialized, are skipped (see Example 64.15).

Boost.Serialization also provides the wrapper boost::serialization::make_binary_object(). Similar to boost::serialization::make_array(), this function expects an address and a length. boost::serialization::make_binary_object() is used solely for binary data that has no underlying structure, while boost::serialization::make_array() is used for arrays.