Subj : Re: (Spidermonkey) Converting a property name to a tinyId
To   : James Turner <zakalawe@mac.com>
From : Brendan Eich <brendan@meer.net>
Date : Wed Mar 12 2003 10:59 am

James Turner wrote:

>I have a pressing need to map a string which *might* be the name of
>property I've defined on an object to it's numerical ID. Essentially I
>need a function which returns either a failure  or the value I passed
>in via the JSPropertySpec to JS_InitClass.
>
>Essential I want:
>
>int8 tinyid;
>JSBool hasTinyId = JS_GetPropertyTinyId(ctx, obj, "foo", &tinyid);
>
>to return true, and set tinyid to be (say) 42, assuming the
>JSPropertySpec looked like
>
>{ "foo", 42, ... flags .... },
>
>I've looked through the jsobj.c code but am getting lost rather
>easily, so could someone tell me if this is even possible? I could
>maintain a seperate lookup table by hand by copying the JSPropertySpec
>array I pass to JS_InitClass, but I figure that table has *got* to
>exist somewhere internally.
>  
>

It does, but maybe you can get it from where you need it.  Where in your 
code do you have this pressing need?  If within a property getter or 
setter, then of course JSVAL_IS_INT(id) is true, and JSVAL_TO_INT(id) 
gives the tinyid.  Otherwise, if you have only a short list of 
properties, linear search should be ok.  We could add a 
JS_GetPropertyTinyId as you suggest, but maybe it's not worth the code 
bloat (minor, but still) in the common engine, if only a few embeddings 
need it and can compute what it returns otherwise.

So sell me!

/be

>Many thanks,
>James
>  
>

.