Question is how to do these in Rust. An example might be a browser DOM: each node has a parent pointer, a list of child pointers, left and right sibling pointers, maybe a CSS node pointer, etc. Inserting or deleting nodes has to repair the pointers to and from the neighboring nodes as needed.

I know this is doable since obviously Servo (Rust's initial driving application) has to do it. I hope the answer doesn't involve the word "unsafe". But I am quite unclear about how to create such a structure under Rust's rules of pointer ownership, and also how to reliably reclaim storage when nodes and trees/subtrees are deleted. Plus there will be thread safety rules that should be statically enforced if possible.

I've heard that doubly linked lists in Rust are handled by an unsafe library, yet this seems even worse. Thanks.

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[–] [email protected] 7 points 2 weeks ago (1 children)

One way to do this is to use reference-counting pointers such as std::rc::Rc or std::sync:Arc. The parent node can hold a strong reference to each child node and each child node has a Weak reference to its parent.

[–] [email protected] 4 points 2 weeks ago

I guess that's possible. The sibling pointers can also be weakrefs, I think. I don't know if there are ever arbitrary links between DOM nodes rather than just the tree-like ones. But, you are onto something if creation of weakrefs safely avoids the pointer ownership rules. I'll have to look into this further.