Possible upgrades to gzfilebuf:- The ability to do putback (e.g. putbackfail)- The ability to seek (zlib supports this, but could be slow/tricky)- Simultaneous read/write access (does it make sense?)- Support for ios_base::ate open mode- Locale support?- Check public interface to see which calls give problems  (due to dependence on library internals)- Override operator<<(ostream&, gzfilebuf*) to allow direct copying  of stream buffer to stream ( i.e. os << is.rdbuf(); )