Re: [Boost-users] [iostreams] How can I use the Stream Insertion operator (<<) with a filtering_streambuf?

26 Jul 2013

      On 26/07/2013 01:37, Stephen Greenfield wrote:
...
Partially asked in another question, but so far unanswered:  Once I create
a
filtering_streambuf that is connected to the zlib_compressor() and the
output file,
how do I then construct an object that can accept data from the Stream
Insertion Operator?
void CompressUsingFilteringStreambuf()
{
     std::ofstream myFile("hello.z", std::ios_base::out |
std::ios_base::binary);
boost::iostreams::filtering_streambufboost::iostreams::output out;
     out.push(boost::iostreams::zlib_compressor());
     out.push(myFile);
// MY QUESTION:  How can I use the "stream insertion" operator
(<<)
         // to go through the filtering_streambuf
         // and place compressed text into myFile?
// HOW DO I CREATE someStream?
         someStream << "text I want to be compressed and end up in the
file...";
myFile.close();
}
I have scoured the documentation and the web looking for the answer -- and
come up empty.
Stephen
Try:

  std::ofstream myFile("hello.z", std::ios_base::out | 
std::ios_base::binary);
  boost::iostreams::filtering_streambufboost::iostreams::output out;
  out.push(boost::iostreams::zlib_compressor());
  out.push(myFile);

  std::ostream os(&out);
  os << "text I want to be compressed and end up in the file..."

On input it would be something like:

  std::ifstream myFile( "hello.z", std::ios::in | std::ios::binary ); 

  boost::iostreams::filtering_streambuf< boost::iostreams::input > in;
  in.push( boost::iostreams::gzip_decompressor() );
  in.push( ifs );
  std::istream is( &in );
  is >> text;

Ken Appleby

Soft Optics Ltd