Subj : Re: Retrieving property  name in getter and setter functions
To   : Eric Brueggemann <eric_brueggemann@yahoo.com>
From : Brendan Eich <brendan@meer.net>
Date : Fri May 09 2003 04:28 pm


>>> Now, how in my AW_JS_Get function can I retrieve the name of the 
>>> property
>>> that has been executed in the users JavaScript?
>>>
>>> static JSBool AW_JS_Get(JSContext *cx, JSObject *obj, jsval id, 
>>> jsval *rval)
>>> {
>>>    // need to get the name of the property here
>>> }
>>>  
>>>
>>
>> if (JSVAL_IS_INT(id)) then the property identifier is 
>> JSVAL_TO_INT(id) -- an integer index.  Otherwise, you can assert that 
>> JSVAL_IS_STRING(id), and JSVAL_TO_STRING(id) can be passed to 
>> JS_GetStringChars and JS_GetStringLength to look at the string's 
>> characters.
>>
>
> Actually, that's not always safe. Since a call to js_Atomize uses 
> temporary space to inflate bytes into wide chars, 
> JSVAL_TO_STRING(id)->chars may no longer exist when the id makes it 
> into your getter/setter. 


False -- search for ATOM_NOCOPY, notice that that flag is *not* used in 
the js_InflateStringToBuffer case in js_Atomize.  I wonder why you 
thought there was a problem, though.  Were you seeing crashes or other 
symptoms of some bug, or were you just reading code?


> The above assertion would be extremely helpful if it were reliable, 
> but it isn't always the case. Any way of fixing this? 


The assertion that the jsval id passed to class or per-property getters 
and setters satisfies either JSVAL_IS_INT(id) or JSVAL_IS_STRING(id) is 
reliable.  If you have a bug to report, please show a testcase or give 
some skidmarks.

/be

>
>
> Cheers,
>
> Eric
>

.