[Boost-users] array sink of unknown size

Hello, I need a filtering_ostream that efficiently yields a char* and it's size (i.e., it allocates the memory it needs). I have no way of knowing or predicting the number of chars resulting from uncompressing the input (?). For efficiency it would be nice to specify an estimate and a "chunking" size, but the filtering_ostream would actually allocate all that is needed. I looked at this: boost::iostreams::stream< boost::iostreams::array_sink > but it seems to need a terminating char* or a size in its ctor. What is recommended? Thanks!