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From: jss@jra.ardent.com
Newsgroups: comp.lang.c++
Subject: Re: Why isn't ostream::osfx/opfx virtual?
Message-ID: <9805@ardent.UUCP>
Date: 21 Dec 89 19:35:43 GMT
References: <1989Dec18.141217.19738@odi.com>
Sender: news@ardent.UUCP
Reply-To: jss@jra.ardent.com ()
Organization: Ardent Computer Corp., Sunnyvale, CA
Lines: 31

In article <1989Dec18.141217.19738@odi.com> benson@odi.com () writes:
>In 2.0, ostream has two functions osfx and opfx that are used to give
>the stream control (for buffering purposes) before and after output.
>They aren't virtual.
>
>As per my previous message, I need to implement some specializations
>of ostream that are sensitive to line boundaries. osfx would serve
>my purposes fine -- if it were virtual.
>

What these functions  do is check for special conditions inline and 
and then call out of line code to deal with these special conditions 
as necessary.  Since all this involves private data it was not 
appropriate to specify exactly what they would have to do and it was 
therefore not appropriate to make them virtual.  

They are part of the public interface so that they can be
called by user defined inserters.  

There is also the efficiency consideration, that making them
virtual would have had a significant performance impact on
the char inserter. 

As I suggested in another note, the best way to deal with
this sort of thing within the iostream interface is to put
the special handling into the streambuf rather than the ostream.
It is possible to cause flush to be called on every character
by making sure the streambuf always looks "full" even when there
is still room in the arrays.

Jerry Schwarz