Subj : Re: Performance Interfacing to C++
To   : netscape.public.mozilla.jseng
From : Brendan Eich
Date : Wed Aug 25 2004 08:14 am

Thorsten R wrote:
> I found an old message from  2001-07-04 via Google, which says:
> 
> 
>>>... interfaced JS with C ...
> 
> It seems to me, however, that these C functions (get, set, etc.) are called
> by the engine subsequent to the engine's own internal JavaScript object
> manipulation routines (i.e. the engine sets a property on the object using
> it's own internal set method, then almost as an afterthought, it calls my
> set method).
> <<


Why didn't you provide a link to this old message?  That's what URLs are 
for, and it's hard to tell what you are talking about without it.


> Brendan Eich had confirmed that this is true.


Yes, and it's not a bug.  For most native and host objects, the shared 
code to manage slots and properties (in a per-runtime lexicographic 
tree) is a win.


> I would like to ask if this is still true in 8 / 2004? And if so, why?  I
> can't see the reason, since the object has pointers declared for its getters
> and setters to external C functions, which should solely be responsible for
> getting and setting properties.


Think a little harder, then.  If every object had to implement its own 
hash tables and obj->slots value storage, there would be much duplicated 
code.  Even if you factored all that code into common subroutines, the 
high-level interface (JSObjectOps) would call into different Date, 
String, RegExp, etc. implementations, which would have to duplicate 
calls to the common subroutines.

It's better to have a common "middleware" implementation of JSObjectOps 
for most such classes.  This actually evolved after the lower-level 
JSClass interface, but that's history.


> Are there any plans to change this?


No concrete plans that you should count on.


> Brendan had also pointed to use JSObjectOps() to work-around that problem.


It's not a work-around, it's an alternative, and the problem is a 
solution for most native and host classes.


> I
> looked at JSObjectOps(), but the docs are not very clear about it and rather
> confusing. Can someone help on how to use this method?


JSObjectOps is not documented.  You'll have to read the source and 
understand the interface yourself.  If you can't do that, then I can't 
recommend you using it.

Perhaps you could say more about your embedding and why you don't need 
the usual property lookup and value storage mechanism?

/be

.