Subj : Re: object serialization
To   : netscape.public.mozilla.jseng
From : Jens Thiele <karme@unforgettable.com>
Date : Wed Apr 07 2004 10:27 am

>> the hash function is shit - is there any way to get a hashvalue for
>> an object (perhaps based on its pointer/reference)?
> However, about the hash function, I can help:
> There is a MD5 hashing class within Mozlib library, part of my JS
> Console extension (<http://jsconsole.mozdev.org>). Find it in the
> "chrome://mozlib/content/lib/js/digest/" directory (after installing JS
> Console, of course). You need only 2 files: generator.js and md5.js.
> 
> You could use the DIGEST_MD5Generator class to hash your objects, based
> on a unique field value, for instance using the Date function. For
> instance:
> 
> var object = {id:new Date}; //add your properties as you wish
> var hashvalue = (new DIGEST_MD5Generator()).getHex(object.id);
> 
> Will it fit?
i hoped to get a hash for any existing object without adding properties

i looked into
JS_GetObjectID, JS_IdToValue, JS_ValueToId
which at first seemed to be the right thing
but perhaps it is not?

any obvious bug there?
ECMA_BEGIN_FUNC(hashObject)
{
      ECMA_CHECK_NUM_ARGS(1);
      jsid id;
      if (!JSVAL_IS_OBJECT(argv[0])) ECMA_ERROR("object required as
argument");
      JSObject *o=JSVAL_TO_OBJECT(argv[0]);
      if (!JS_GetObjectId(cx,o,&id)) return JS_FALSE;
      if (!JS_IdToValue(cx,id,rval)) return JS_FALSE;
      return JS_TRUE;
}

hmm following will crash:
if (!JS_GetObjectId(cx,o,&id)) return JS_FALSE;
if (!JS_IdToValue(cx,id,rval)) return JS_FALSE;
JS_TypeOfValue(cx,*rval);

JS_PUBLIC_API(JSType)
JS_TypeOfValue(JSContext *cx, jsval v)
{
    JSType type;
    JSObject *obj;
    JSObjectOps *ops;
    JSClass *clasp;

    CHECK_REQUEST(cx);
    if (JSVAL_IS_OBJECT(v)) {
        /* XXX JSVAL_IS_OBJECT(v) is true for null too! Can we change
ECMA? */
        obj = JSVAL_TO_OBJECT(v);
        if (obj &&
            (ops = obj->map->ops,

CRASH since JSVAL_IS_OBJECT is true but the value is not an object

puh
Brendan? ;-)

.