unary * on a local<T> gives a T*: https://v8.paulfryzel.com/docs/master/classv8_1_1_local.html#a3c96c0bc5db1288bad5769e8e54e26da
On Wednesday, June 20, 2018 at 10:58:37 PM UTC-7, Gonzalo Diethelm wrote: > > I run the following JS code in the Chrome console: > > // Version 67.0.3396.87 (Official Build) (64-bit) > > var x = [1, 2, {"foo": 11}]; > x[2].bar = x; > > Now from C++ code, I get ahold of x as a Local<Object>, and wish to > traverse the whole structure; for the sake of the example, let's say I am > converting it into serialized data (I know I can use JSON.stringify() to do > this, serializing is just an example to clarify ideas). My question is, > how can I keep track of the nodes in the structure that I have already > seen, and their associated serialized value, so that I can avoid an > infinite traversal? > > It seems to me doing this would require a way to get a unique identity for > each node, so that the C++ code can do something similar to this: > > typedef map<NodeId, NodeData> NodeMap; > NodeMap seen; > ... > Local<Object> node = current.GetNextChild(); > NodeId id = node.GetUniqueId(); > NodeMap::iterator k = seen.find(id); > NodeData data; > if (k != seen.end()) { > // node already seen, reuse its serialization > data = k->first; > } else { > // first time we see node, serialize and remember > data = node.Serialize(); // recurses > seen[id] = data; > } > > The specific question is: what type could be NodeId, and how do I get the > equivalent of GetUniqueId()? > > I am very tempted to ask for a way to get a raw void* to each node, but I > guess any way of doing this is fine, as long as I can get a unique id that > is stable while I'm traversing the data. For these reasons, > GetIdentityHash() does not seem to fit the bill: "*The return value will > never be 0. Also, it is not guaranteed to be unique.*" > > Incidentally, If I try to use JSON.stringify for my data, I get this: > > JSON.stringify(x) > VM170:1 Uncaught TypeError: Converting circular structure to JSON > at JSON.stringify (<anonymous>) > at <anonymous>:1:6 > > This is taken care of here in the V8 code: > > JsonStringifier::Result JsonStringifier::StackPush(Handle<Object> object) > { > ... > // member stack_ is: Handle<JSArray> stack_; > int length = Smi::ToInt(stack_->length()); > FixedArray* elements = FixedArray::cast(stack_->elements()); > for (int i = 0; i < length; i++) { > FixedArray* elements = FixedArray::cast(stack_->elements()); > if (elements->get(i) == *object) { > // boom > } > } > } > > So, operator*() in a Handle<Object> gives me a unique id? Which is the > type for this? Can I store that in a C++ map? Is it stable (enough)? > > Thanks! > -- -- v8-users mailing list v8-users@googlegroups.com http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.