c++ large file

#include <stdint.h>

#include <cassert>
#include <fstream>
#include <iostream>
#include <vector>

//! Main program that demonstrates large file handling
int
main
   ( int const argc
   , char const * const * const argv
   )
{
   std::ofstream ofs("bigfile.bin", std::ios::binary);

std::cerr << sizeof(std::streamoff) << std::endl;
std::cerr << sizeof(std::ios::pos_type) << std::endl;
std::cerr << sizeof(std::ios::off_type) << std::endl;

   // 4mb test buffer
   std::vector<uint32_t> buffer(1024 * 1024);

   size_t const bufbytes(sizeof(buffer[0]) * buffer.size());
   std::generate(buffer.begin(), buffer.end(), std::rand);

   uint64_t totalbytes(0);

   uint64_t const desiredbytes(3ULL * 1024ULL * 1024ULL * 1024ULL);
   while (totalbytes < desiredbytes)
   {
      ofs.write((char const *)&buffer[0], bufbytes);
      totalbytes += bufbytes;
   }

   ofs.close();

   std::ifstream ifs("bigfile.bin", std::ios::binary);
   ifs.seekg(0, std::ios::end);

   std::ios::streampos const fsize(ifs.tellg());
   std::cout << "seek from end: " << fsize << std::endl;

   ifs.seekg(0);
   ifs.seekg(fsize);
   std::cout << "seek to end: " << ifs.tellg() << std::endl;

   return 0;
}