Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ukma!xanth!lazarus
From: lazarus@cs.odu.edu (Keith E. Lazarus)
Newsgroups: comp.editors
Subject: Re: multi-user editors???
Keywords: uses, feasible
Message-ID: <8571@xanth.cs.odu.edu>
Date: 20 Apr 89 17:24:30 GMT
References: <8531@xanth.cs.odu.edu> <1736@deimos.cis.ksu.edu>
Reply-To: lazarus@cs.odu.edu (Keith E. Lazarus)
Distribution: usa
Organization: Old Dominion University, Norfolk Va.
Lines: 56


>> Do any of y'all know of any full-screen editors that support multiple 
>> users editing a single file at one time???  

> Sorry, but I don't quite follow you. When would this be usefull, and
> how on earth would you implement such a thing?
> --
> Lars Bo Nielsen  ( lbn@ksuvax1.cis.ksu.edu  -*O*-  ...!rutgers!ksuvax1!lbn)

1) when would this be useful???

i'm not exactly sure...  thanks to separate compilation, there really
shouldn't be a need to do this if the modules were broken down into a small 
enough size.  even then, occasionally it might be convenient to allow two
people, working at separate terminals, to access the same file concurrently.


2) how would such a creature be implemented?

for a systems programming course that i'm taking here, i implemented a 
primitive full screen editor that supports this.  to work around the problem
of having two copies of the file being edited in memory at the same time, 
i used a server/client type arrangement.  one server would exist for each
file being edited and one client for each user.  the server maintains a
fairly current image of the file being edited. ( i say <fairly current>
because the client only sends an updated copy of the line being 
edited when the user moves his cursor off of the line )

all character based operations (ie. adding/deleting characters) are performed
by the client and all line based operations (ie. insertion/deletion) are
performed by the server.  also, the server is responsible for preventing
multiple users from modifying the same line at line time.

all of the interprocess communications are via sockets.  i do realize that 
if several instances of this program were running that this could cause a 
fairly substantial load on a network, but nothing comes free.......

...........

All this brings me back to my original question:

>> Do any of y'all know of any full-screen editors that support multiple 
>> users editing a single file at one time???  

and a new question:

  Can any of you come up with any other possible uses for such an editor?


                      k.e.l.

-- 
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  Keith E. Lazarus                     Department of Computer Science
  lazarus@xanth.cs.odu.edu             Old Dominion University  Norfolk, VA
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