Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!ucsd!sdcsvax!ucsdhub!hp-sdd!hplabs!hpda!hpsemc!bd
From: bd@hpsemc.HP.COM (bob desinger)
Newsgroups: comp.emacs
Subject: Re: undo
Message-ID: <690011@hpsemc.HP.COM>
Date: 22 Apr 88 16:03:28 GMT
References: <282@litp.UUCP>
Organization: HP SEMC, Cupertino, CA
Lines: 11

Francois-Xavier Testard-Vaillant (fxtv@litp.UUCP) writes:
> I would appreciate help about the undo mechanism of editors such as
> emacs. What are the basic tools used to implement this? Are they
> efficient?

For GNU Emacs, see dist-*/src/undo.c and dist-*/src/undo.h.  The code
there uses structs, so it's somewhat hairy.  It copies data using the
extremely fast bcopy() routine, so it's quite efficient.  (Remember
that premature optimization is the root of all evil---don't make it
fast before you make it right.)

-- bd