What I would like to do is to skip over part of a gzip'ed input, in a manner similiar to calling gzseek() in C, but I don't seem to be able to do that. Since it is possible to do it in C (somewhat slowly and there is no bzseek), I was thinking of something similiar to: namespace boost_io = boost::iostreams; boost_io::filtering_istream *instr = new boost_io::filtering_istream(); /* one of these two */ //instr->push(boost_io::gzip_decompressor()); instr->push(boost_io::bzip2_decompressor()); instr->push(boost_io::file_source(m_FileName.c_str(), std::ios::in | std::ios::binary)); // skip the header //instr->seekg(boost_io::offset_to_position(m_iHeaderBytes), std::ios_base::beg); instr->seekg(boost_io::offset_to_position(m_iHeaderBytes)); int32_t datasize = BUFFER_ZIZE; m_lpData = new char[datasize]; std::cout << "position before:\t " << instr->tellg() << std::endl; instr->read(m_lpData, datasize); std::cout << "position after:\t " << instr->tellg() << std::endl; But I tellg() returns 0 and datasize without the push::decompressor, and -1/-1 when the decompressor is pushed. Am I doing something wrong? I know streams aren't really seekable, but I was hoping that there is a poorman's seek (like gzseek - which is essentially read and throw-away) that's implementable. The incentive - is to have transparent decompression of input in some legacy code - I don't really want to modify every read to gzread, or bzread, for example... Thanks a lot. Hin-Tak Leung Send instant messages to your online friends http://uk.messenger.yahoo.com