Path: utzoo!attcan!uunet!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Serious programming question
Message-ID: <8785@hoptoad.uucp>
Date: 23 Oct 89 05:13:19 GMT
References: <89295.142753CXT105@PSUVM.BITNET> <4002@helios.ee.lbl.gov>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 30

The linked list suggestions made so far may be fast enough for a word
processor, but the Memory Manager will really bog down when you have a
lot of these chunks allocated.  If you want better performance, it
would probably be better to pre-allocate a large buffer and treat nulls
as non-characters, the "holy buffer" approach.  This will completely
avoid Memory Manager overhead, but may require you to move more data
explicitly.  You can optimize it in various ways, as any
second-semester data structures textbook will tell you.  You can leave
extra space to make insertions faster, or use only as much space as the
user types if you feel deletions are more important.

The subject is not trivial and I recommend some research before you
begin.  I just plunged ahead with a relocatable linked list approach
for one of my terminal emulators and I wound up with something that
couldn't keep up with 2400 baud on an 8MHz 68000.  On the other hand,
it was a lot faster for data input than the MPW Shell.  So I guess my
main advice is -- be prepared to throw away your first stab at it.
Make sure knowledge of your data structures is confined to only those
files that need it, so that you can change them when you find that your
first algorithm bogs down in certain situations.  Be sure to test speed
with respect to operations like large pastes and very fast typing.  And
familiarize yourself beforehand with the various buffering strategies
that can be found in the textbooks.  Most importantly, be sure to leave
yourself a way to buffer large files on disk.
-- 
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com

FROM THE FOOL FILE:
"As the expert on stupid, I'll take your word for it."
  -- Richard Sexton, richard@gryphon.COM