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

Subject: Re: [Boost-users] [iostreams] How can I use the Stream Insertion operator (<<) with a filtering_streambuf?
From: Stephen Greenfield (StephenG_at_[hidden])
Date: 2013-07-29 00:28:04

On 7/28/13 8:45 PM, "Larry Evans" <cppljevans_at_[hidden]<mailto:cppljevans_at_[hidden]>> wrote:

I thought the filtering_stream would be derived from std::ostream, at
least according to:

  Derived class of std::basic_istream, std::basic_ostream or
  std::basic_iostream, used to perform filtering.

quoted from:

http://www.boost.org/doc/libs/1_54_0/libs/iostreams/doc/classes/filtering_stream.html


Did you not find this so, or do you needs require something more
specific than std::ostream& to be passed to the other functions you
mention?

Larry --

Thanks!  You would've thought that — and you know what?  You would be CORRECT.

I thought I had tested every possible case — but I think I did that BEFORE discovering my error with closing the file before destructing the filtering_streambuf/filtering_ostream.

You (and everyone else) were ABSOLUTELY CORRECT.  When I changed my code from a filtering_streambuf:

ofstream myXMLFile (destPath, std::ios_base::out | std::ios_base::app | std::ios_base::binary);
boost::iostreams::filtering_streambuf<boost::iostreams::output> filteringOStream;
filteringOStream.push(boost::iostreams::zlib_compressor());
filteringOStream.push(myXMLFile);
std::ostream myExportedXMLFilteringOStream(&filteringOStream);
Foo(myExportedXMLFilteringOStream);

TO A filtering_ostream:

ofstream myXMLFile (destPath, std::ios_base::out | std::ios_base::app | std::ios_base::binary);
boost::iostreams::filtering_ostream myExportedXMLFilteringOStream;
myExportedXMLFilteringOStream.push(boost::iostreams::zlib_compressor());
myExportedXMLFilteringOStream.push(myXMLFile);
Foo(myExportedXMLFilteringOStream);

Thank you so much for tying up that loose end!  I'm assuming the filtering_ostream is of course more efficient than the filtering_streambuf scenario?

Best Regards,

Stephen