title: Length of boost::iostream::basic_array_sink/source
body: <p>I'm using to do some serialization stuff <a href="https://stackoverflow.com/questions/3015582/direct-boost-serialization-to-char-array" title="as it can be seen here">"as it can be seen here"</a>. That worked fine, but I couldn't figure how to get the size of the written buffer.I've searched on boost documentation and apparently there is no way to do this aside of building a sink/source by myself?</p>
  
  <p>Thanks</p>