file mapping

#include <iostream>
#include <boost/filesystem/v3/operations.hpp>
#include <boost/interprocess/file_mapping.hpp>
#include <boost/interprocess/mapped_region.hpp>
#include <boost/chrono.hpp>
#include <boost/array.hpp>
#include <fstream>

int main()
{
    using namespace std;
    using namespace boost;
    chrono::system_clock::time_point now = chrono::system_clock::now();
    size_t size;
    {
        interprocess::file_mapping mfile("mapped_file.txt", interprocess::read_write);
        interprocess::mapped_region region(mfile, interprocess::read_write);
        array<char, 23> *const addr = (array<char, 23> *)region.get_address();
        size = region.get_size() / 23;
        sort(addr, addr + size, [] (array<char, 23> const &buf1, array<char, 23> const &buf2) {
            return memcmp(&buf1, &buf2, 21) < 0;
        });
        size = unique(addr, addr + size, [] (array<char, 23> const &buf1, array<char, 23> const &buf2) {
            return memcmp(&buf1, &buf2, 21) == 0;
        }) - addr;
    }
    filesystem::resize_file("mapped_file.txt", size * 23);
    cout << chrono::system_clock::now() - now;
}