Hi, i am trying to get access to specialized stream attributes in my own filters. I created a specialized stringstream class which holds some kind of log level, which i want to use in my input filters. Therefore i wrote a input device which handles my specialized class. With debug outputs i see that this device is used to read my stream. Now i want to create a filter which is able to access the log level attribute from the specialized stream. I tried to specialize the template function for reading from the source for my stream device and for the specialized stream but none of these functions are getting used. Is there a way to be able to access either the device or the source stream in the filters? The example code below gives a short example of the mentioned problem. #include <iostream> #include <sstream> #include <string> #include <boost/iostreams/concepts.hpp> #include <boost/iostreams/operations.hpp> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/char_traits.hpp> #include <boost/iostreams/stream.hpp> // specialized stream class class console_out_stream : public std::stringstream { public: console_out_stream() : std::stringstream() {} virtual ~console_out_stream() {} int get_log_level() const { return (_log_level); } void set_log_level(int l) { _log_level = l; } private: int _log_level; }; // ability to set log level using the << operator on the new stream class class log_level { public: log_level(int l) : _log_level(l) {} int _log_level; }; console_out_stream& operator << (console_out_stream& con_str, const log_level& log) { con_str.set_log_level(log._log_level); return (con_str); } // source device class my_console_source : public boost::iostreams::source { public: my_console_source(console_out_stream& con) : _console(con) {} std::streamsize read(char* s, std::streamsize n) { std::cout << "ran through the source" << std::endl; return (boost::iostreams::read(_console, s, n)); } const console_out_stream& get_console() const {return _console; } protected: console_out_stream& _console; }; // input filter // just filters out the character s class test_in_filter_m : public boost::iostreams::multichar_input_filter { public: explicit test_in_filter_m() {} template<typename Source> std::streamsize read(Source& src, char* s, std::streamsize n) { for (std::streamsize z = 0; z < n; ++z) { int c; while (true) { if ((c = boost::iostreams::get(src)) == EOF) return z != 0 ? z : -1; else if (c == boost::iostreams::WOULD_BLOCK) return z; if (c != 's') break; } s[z] = c; } return n; } template<> std::streamsize read<my_console_source>(my_console_source& src, char* s, std::streamsize n) { std::cout << "ran through the source filter: my_console_source" << std::endl; return (n); } template<> std::streamsize read<console_out_stream>(console_out_stream& src, char* s, std::streamsize n) { std::cout << "ran through the source filter: console_out_stream" << std::endl; return (n); } }; int main(int argc, char **argv) { console_out_stream console; console << log_level(20) << "sick, sad world!"; console << log_level(5) << "from mtv daria" << std::endl; boost::iostreams::stream<my_console_source> in_stream_buf(console); boost::iostreams::filtering_istream out_stream; out_stream.push(test_in_filter_m()); out_stream.push(in_stream_buf); std::string line; while (std::getline(out_stream, line)) { std::cout << line << std::endl; } return (0); } -chris -- Christopher Lux | | Bauhaus University Weimar | Faculty of Media - Virtual Reality Systems Group