On Tue, Oct 30, 2012 at 5:08 AM, Hossein Siadati <[email protected]>wrote:
> Thanks for response. > Look at this in general. Is that something related to caching of objects. > No. I mean I change the object value directly in the memory but I can not see > the result in assignment. > You write something to *some* memory address. What makes you so sure that that's the address where the property in question is actually stored? > My speculation is that these two things may happen: > - V8 keeps multiple copies of one object (why v8 should do that? After > assignment it may recreate the object instead of changing the value!) > No. > - For the sake of the performance, v8 keeps the recently used objects in a > cache helping it to speed up the access to values > No. > > I am really puzzled! May be I should change the AST in order to intercept > the assignments. > No. You've never explained on a high level what you're trying to achieve, but I'm pretty sure that changing V8's internals is not the right way to do it. Accessing and modifying DOM elements is best done in JavaScript running in the browser, no modification of the browser or its JS engine should be necessary. Custom behavior on read/write accesses to certain properties of JS objects can be implemented using getters/setters, maybe that's something you should look into. > Thanks, > HDev > > On Mon, Oct 29, 2012 at 7:58 PM, Jakob Kummerow <[email protected]>wrote: > >> Since _nodeValue is not defined by V8, this is a question for whoever >> defined that property on the object. It could be intercepted or whatever. >> >> Also, be aware that playing with raw pointers is dangerous. Your address >> calculation looks fishy to me. In objects.cc, there should be no need to do >> anything that low-level. Look for existing functions that do what you need. >> >> >> On Mon, Oct 29, 2012 at 11:54 AM, Hossein Siadati >> <[email protected]>wrote: >> >>> After the HTML is parsed and the DOM tree is built, for each DOM >>> element, a JSObject is created. The JSObject class is defined in objects.h >>> file and the methods reside in objects.cc file. >>> >>> JSObject is inherited from class Object, and Object class >>> is inherited from class MaybeObject. Each JSObject probably has a map which >>> keeps pairs of key-value things for each DOM element, including parent, >>> child nodes, name, and value. The key in which keeps the value is >>> _nodeValue (which should be named by jsdom or htmlparser which I use for >>> parsing and creating the DOM tree). I change the _nodeValue directly (for >>> example want to encrypt it). I can change the _nodevalue. But when I assign >>> the value of that node to a variable, the old value is assigned to that >>> variable. >>> >>> By "directly", I mean that I want to intercept the access to DOM >>> elements in v8, and when a value wants to be assigned to the node, I want >>> to encrypt the value. In the reverse side, i should decrypt when I am >>> reading from the node. Currently, I think that the JSObject::SetProperty >>> and Object::GetProperty methods in objects.cc file is the correct place. >>> I intercept there and change the _nodeValue property of the JSObject then I >>> change the value like this: >>> >>> // i is the index of _nodeValue in the map of properties of the node >>> DescriptorArray* descs = map()->instance_descriptors(); >>> int index = 0; >>> index = descs->GetFieldIndex(i); >>> int offset = map()->inobject_properties() + (index * kPointerSize); >>> *reinterpret_cast<uint16_t*>(reinterpret_cast<byte*>(this) + >>> offset - kHeapObjectTag -1 ) = ENCRYPTEDVALUE; >>> >>> That is how I do that. But I do not know why the change does not applies? >>> Am I doing right? What is the problem? >>> >>> Thanks, >>> Hossein >>> >>> On Mon, Oct 29, 2012 at 6:38 PM, Jakob Kummerow >>> <[email protected]>wrote: >>> >>>> I don't know what you're talking about. What's the "value" of a >>>> JSObject? What does changing it "directly" mean? What's a "_nodeValue" >>>> attribute? The V8 source code does not contain this string. >>>> >>>> >>>> On Mon, Oct 29, 2012 at 9:08 AM, HDev <[email protected]> wrote: >>>> >>>>> Hi All, >>>>> >>>>> I wan to change the value of JSObject s directly. Should I change the >>>>> value of _nodeValue attribute? >>>>> Please help!!!!! >>>>> >>>>> Thanks, >>>>> HDev >>>>> >>>>> -- >>>>> v8-dev mailing list >>>>> [email protected] >>>>> http://groups.google.com/group/v8-dev >>>> >>>> >>>> -- >>>> v8-dev mailing list >>>> [email protected] >>>> http://groups.google.com/group/v8-dev >>> >>> >>> -- >>> v8-dev mailing list >>> [email protected] >>> http://groups.google.com/group/v8-dev >>> >> >> -- >> v8-dev mailing list >> [email protected] >> http://groups.google.com/group/v8-dev > > > -- > v8-dev mailing list > [email protected] > http://groups.google.com/group/v8-dev > -- v8-dev mailing list [email protected] http://groups.google.com/group/v8-dev
