[boost] boost::iostreams: only with std::cout?

From: Dirk Griffioen (dirkgriffioen_at_[hidden])
Date: 2005-03-22 05:10:39

Hi,

 

I would love to use the boost::iostreams lib, so I created a filter
(which, in this case, does encryption)

but instead of passing it std::cout I would like to pass it some other
stream, a stringstream for instance (or any kind of ostream/istream,
depending on the direction).

 

However, I was very surprised to find the following code taking 100% cpu
and not returning. It probably means I did something wrong, but I can't
seem to find it.

 

void test_encryption_filter()

 {

    const char* speech =

        "They sorely misunderestimate the American people if they "

        "think we will let them obtain nucular weapons. This "

        "malfeance will not stand.";

 

    // std::ostream which writes to standard output, filtered by a

    // encryption_output_filter.

    boost::io::filtering_ostream out;

    out.push(encryption::code_book::output_filter());

 

    //out.push(std:cout); //this works

 

    std::ostringstream os;

    out.push(os); //this does not

 

    // Print unfiltered code.

    std::cout << "**** Speech unfiltered ****\n" << speech << "\n\n";

  

    // Print filtered code:

    std::cout << "**** Speech with encryption filter ****\n";

    out << speech << "\n\n";

}

 

(testing puspose) filter looks like (namespace omitted):

 

struct output_filter : public multichar_output_filter {
        template<typename Sink>
        void write(Sink& snk, const char* s, streamsize n) 
            { 
                while (n-- > 0)
                    boost::io::put(snk, toupper(*s++));
            }
    };

 

 

With std::cout this works fine, with std::ostringstream it does not.

 

So could anyone please tell me what I am missing?

 

Thanks in advance, Dirk

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