RE: Channel concept instead of simple Files

[Sander van der Wal <svdwal@xs4all.nl>]

On Fri, 12 Jan 96 9:00:55 EST acken@informatik.uni-kl.de (you) wrote:

> >  From: Sander van der Wal <svdwal@xs4all.nl>
> >  Date: Fri, 12 Jan 1996 11:54:44 +0100
> >  
> >  ...
> >  There is another factor to take into account, there is a difference 
> >  between for instance a disk file and the keyboard.
[knip]
> 
> Unix, and AFAIK AmigaOS, simply spend the file descriptor (stream,
> channel, or whatever) additional attributes and/or prevent a function
> that needs a specific feature from being used.  For example the Unix
> pipes and FIFOs don't allow lseek() and make it return with an error
> code.  A simple solution to this problem is to add an "is
> positionable" flag to the channel, similar to the "is readable" and
> "is writable" flags.

RISC OS does something similar with the file descriptor. Unix really
has a large influence ;-).
I find the use of a 'is positionable' flag a bit of a hack.
If there are two kinds of channels, a positionable one and a sequential 
one, I can immediately deduct some properties of the algorithm that 
uses a paricular kind of channel. Take for instance a backend for ooc:
if the channel is sequential, I immediately know that either the code
generator is sequential too, or that it buffers the code.  
 
-- 
Sander        

We get to pick tools and equipment that suit the job.  We spend nearly all our 
time programming ART's computer's. (~P.J.Plauger: Programming on Purpose III)