//Purpose:
//  Explore differences in ways iostreams filtering is done
//  with different device types.
//Acknowledgements:
//  Original code from post:
/*
From: Ken Appleby <ken.appleby@btopenworld.com>
Newsgroups: gmane.comp.lib.boost.user
Subject: Re: [iostreams] How can I use the Stream Insertion
 operator (<<) with a filtering_streambuf?
Date: Fri, 26 Jul 2013 18:06:47 +0100
Lines: 94
*/
//ChangeLog:
//  2013-07-29.0847
//    Converted to use:
//      filtering_estream 
//    instead of:
//      filtering_streambuf
//    after reading post:
/*
From: Stephen Greenfield <StephenG@screenplay.com>
Newsgroups: gmane.comp.lib.boost.user
Subject: Re: [iostreams] How can I use the Stream Insertion
 operator (<<) with a filtering_streambuf?
Date: Mon, 29 Jul 2013 04:28:04 +0000
Lines: 167
 */
//==========================
#include <iostream>
#define USE_STRINGSTRM //use stringstream instead of fstream.
#ifdef USE_STRINGSTRM
#include <sstream>
#else
#include <fstream>
#endif

#include <boost/iostreams/filtering_stream.hpp>
#include <boost/iostreams/copy.hpp>
#include <boost/iostreams/filter/gzip.hpp>

namespace bio = boost::iostreams;

int main()
{
    std::cout<<"USE_STRINGSTRM="
    #ifdef USE_STRINGSTRM
      <<"yes defined"
    #else
      <<"not defined"
    #endif
      <<"\n";
      std::string 
    expected_text
      //storage for output to be compressed.
      ;
    {//make expected_text just list of numbers
     //delimited by { , and }.
          std::ostringstream 
        expected_strm
          //used to compose output to be compressed.
          ;
        expected_strm<<"{ ";
        for(unsigned i=0; i<10; ++i)
        {
            if(i) expected_strm<<", ";
            expected_strm<<i<<"\n";
        }
        expected_strm<<"}\n";
        expected_strm.flush();
        expected_text=expected_strm.str();
    }
    std::cout << "expected_text=\"\n" << expected_text << "\"" << std::endl;
    std::ios::openmode const ios_binary=std::ios::binary;
    try
    {
        std::ios::openmode const mode_out=ios_binary | std::ios::out;
      #ifdef USE_STRINGSTRM
        typedef std::ostringstream strm_type;
          std::string 
        actual_out
          //actual compressed output.
          //Used to transfer value to std::istringstream CTOR
          //for reading back in.
          ;
      #else
        typedef std::ofstream strm_type;
        char const*filePath="hello.gz";
      #endif
        {
          #ifdef USE_STRINGSTRM
            strm_type myOstrm(            mode_out );
          #else
            strm_type myOstrm( filePath , mode_out );
          #endif
            bio::filtering_ostream out;
            typedef bio::gzip_compressor filter_type;
            filter_type filter_push;
            out.push( filter_push );
            out.push( myOstrm     );
            out << expected_text;
            out.reset();
          #ifdef USE_STRINGSTRM
            actual_out=myOstrm.str();
          #endif
        }
        {
          std::ios::openmode const ios_mode=ios_binary | std::ios::in;
          #ifdef USE_STRINGSTRM
            std::istringstream myIstrm( actual_out, ios_mode);
          #else
            std::ifstream      myIstrm( filePath  , ios_mode);
          #endif
            bio::filtering_istream inp;
            bio::gzip_decompressor filter_push;
            inp.push( filter_push );
            inp.push( myIstrm );
            std::string actual_text;
            while ( inp.good() )
            {
                char ch = inp.get();
                if ( inp.good() )
                {
                    actual_text.push_back( ch );
                }
            }
            std::cout << "actual_text=\"\n" << actual_text << "\"" 
              << std::endl << std::flush;
            std::cout<<"(actual_text==expected_text)="
              <<(actual_text == expected_text)<<"\n";
        }
    } 
    catch ( std::exception& e )
    {
        std::cerr << e.what() << std::endl;
    }
}