How to shrink boost::offset_ptr

Question

I'm using boost::interprocess::offset_ptr<> template class specialization, as a type of several fields in my structure. Unfortunately offset_ptr has a size of an underlying pointer(8 bytes in my case). However I'm convinced, that it will never exceed the max size of 4 bytes integer.

So here comes my question. Can I somehow create 4-bytes range offset_ptr easily, or I will have to cast to and from 4-byte width integer?

Answer 1

offset_ptr with default template parameters is

static const std::size_t offset_type_alignment = 0;

template <class T, class DifferenceType = std::ptrdiff_t,
class OffsetType = std::size_t, std::size_t Alignment = offset_type_alignment>
class offset_ptr;

You can change third parameter of offset_ptr.

#include <iostream>
#include <boost/interprocess/offset_ptr.hpp>
#include <cstdint>

int main()
{
   using namespace boost::interprocess;

   offset_ptr<int, std::ptrdiff_t, std::uint32_t> offs;
   std::cout << sizeof(offs) << std::endl;
}