Subj : Re: int8 for property enum?
To   : netscape.public.mozilla.jseng
From : Brendan Eich <brendan@meer.net>
Date : Mon Feb 02 2004 01:27 pm

Brendan Eich wrote:

> Why tinyids, anyway?  They exist so you can have a class getter or 
> setter, or even a getter/setter shared among a set of properties, and 
> you want the common getter/setter to switch on an int id of some 
> sort.  That's what tinyids are for; they make for dense switches, and 
> generally you don't need anywhere near more than a hundred or so 
> well-known properties per built-in object class. 


To finish this story, the shared getter or setter has common prolog and 
epilog code around the switch on N tinyid cases, that would otherwise 
have to be subroutined, or duplicated, among N distinct getters or 
setters.  This common prolog and epilog code can be big enough that the 
code size reduction from sharing is worth the small cycle hit of the 
switch statement.  Code size vs. cycle is an apples to oranges 
trade-off, of course; YMMV.

/be

.