Slow EULA display patch

[Dan Hipschman]

On Sun, Jul 02, 2006 at 04:35:11PM -0700, Dan Kegel wrote:
> FWIW, Dan H also explored a change to make a riched "run" struct be
> refcounted; that gave a 4x speedup.  Then he switched to using
> git bisect to find the cause of the regression, and shelved the
> refcounting patch.

That wasn't the real reason I scratched the refcount idea.  To make it
work correctly, I had to add copy-on-write and once I did this the performance
dropped again.  However, the problem I was trying to solve was that
ME_SplitRunSimple calls ME_VSplitString, which makes a copy of a large
suffix of its string argument.  The process then occurs again iteratively
on the suffix, so a lot of copys are being made.  Instead of this, if we
only copied the part of the suffix we need, and then use the same base
string in every iteration, we could eliminate another n-squared algorithm.

The 4x speedup might have been, in part, a side effect of something that
got broken by the incorrectly reference counted strings.  Sorry I didn't
mention this before.