I ran into a problem when using restrict on a file_source. The problem was that it decided that the stream wasn't seekable and called the version of skip that reads a character at a time until it gets to the requested offset, instead of just calling seek. The code was similar to this: namespace io = boost::iostreams; std::string filename; io::filtering_istream rstr(io::restrict(io::file_source(filename), 10, 100)); I've attached a patch that solved my problem. It was checking to see if the device was seekable (which means input_seekable and output_seekable), but since it was an input device, it was just input_seekable. Phillip Seaver --- skip.hpp.orig 2007-03-20 16:20:55.253000000 -0400 +++ skip.hpp 2007-03-20 16:11:51.096750000 -0400 @@ -67,7 +67,17 @@ void skip(Device& dev, stream_offset off) { typedef typename mode_of<Device>::type mode; - detail::skip(dev, off, is_convertible<mode, seekable>()); + typedef mpl::or_< + mpl::and_< + is_convertible<mode, input>, + is_convertible<mode, input_seekable> + >, + mpl::and_< + is_convertible<mode, output>, + is_convertible<mode, output_seekable> + > + > can_seek; + detail::skip(dev, off, can_seek()); } template<typename Filter, typename Device>