#include <vector>
#include <fstream>
#include <iterator>
#include <algorithm>
#include <iostream>
#include <cassert>
#include <cstdlib>

#include <boost/progress.hpp>
#include <boost/shared_ptr.hpp>

double do_copy_via_streambuf()
{
  const size_t len = 1024*2048;
  const size_t factor = 5;
  ::std::vector<char> data(len, 1);

  std::vector<char> buffer(len*factor, 0);

  ::std::ofstream
    ofs("test.dat", ::std::ios_base::binary|::std::ios_base::out);
  noskipws(ofs);

  std::streambuf* rdbuf = ofs.rdbuf()->pubsetbuf(&buffer[0], buffer.size());

  ::std::ostreambuf_iterator<char> oi(rdbuf);

  boost::progress_timer pt;

  for(size_t i=1; i<=250; ++i)
  {
    ::std::copy(data.begin(), data.end(), oi);
    if(0==i%factor)
      rdbuf->pubsync();
  }

  ofs.flush();
  double rate = 500 / pt.elapsed();
  std::cout << rate << std::endl;
  return rate;
}

void count_avarage(const char* op_name, double (*fct)())
{
	double av_rate=0;
	const size_t repeat = 1;
	std::cout << "doing " << op_name << std::endl;
	for(size_t i=0; i<repeat; ++i)
		av_rate+=fct();

	std::cout << "average rate for " << op_name << ": " << av_rate/repeat 
            << "\n\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n\n"
            << std::endl;
}


int main()
{
    count_avarage("copy via streambuf iterator", do_copy_via_streambuf);
    return 0;
}

doing copy via streambuf iterator

Timeout