[boost] Someone wanted filtered/decorated streambufs?

From: Daryle Walker (dwalker07_at_[hidden])
Date: 2003-06-27 00:40:25

For the past few weeks, some posters were talking about streambufs that 
can decorate another stream buffer.  I wrote up a general class at 
<http://groups.yahoo.com/group/boost/files/filter_stream.hpp>.

The non-virtual filter functions act as a pass-through (i.e. no change) 
filter/monitor at the moment.  We would need to figure out the points 
of customizing before adding the virtual filter functions.  For 
instance, "doing_imbue" could have a virtual "do_postonly_imbue" that 
only lets the filter do its own adjusting for locale changes after the 
main stream buffer has already done its adjustments.  The "doing_sync" 
method could have a virtual "do_preonly_sync" that is called before the 
main stream buffer's syncing, and the virtual method could return a 
Boolean determining if the main buffer should continue.  The other 
"doings" could have pre- and post-actions (no "only," of course).

One difficulty would be if the reading and/or writing overrides need  
to store extra characters.  Maybe I could add reserve space in the 
filtering stream buffer....

Daryle