Refactor TreeArena #827
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Refactor TreeArena #827
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Document tests more. Fix a lifetime error in unsafe API. Remove the `mem::swap` tests. While the action they were testing was possible, sharing data between two separate arenas isn't meant to be part of the API and is unlikely to happen in the wild.
Rename a lot of methods. Rework documentation. Unify safe and unsafe APIs.
DJMcNab
reviewed
Jan 16, 2025
Comment on lines
-99
to
-136
| fn mem_swap() { | ||
| let mut tree_a: TreeArena<char> = TreeArena::new(); | ||
| let mut roots_a = tree_a.root_token_mut(); | ||
| roots_a.insert_child(1_u64, 'a'); | ||
| let mut node_1_a = roots_a.get_child_mut(1_u64).expect("No child 1 found"); | ||
| node_1_a.children.insert_child(2_u64, 'b'); | ||
| node_1_a.children.insert_child(3_u64, 'c'); | ||
| let mut node_3_a = node_1_a | ||
| .children | ||
| .get_child_mut(3_u64) | ||
| .expect("No child 3 found"); | ||
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| node_3_a.children.insert_child(4_u64, 'd'); | ||
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| let mut tree_b: TreeArena<char> = TreeArena::new(); | ||
| let mut roots_b = tree_b.root_token_mut(); | ||
| roots_b.insert_child(4_u64, 'e'); | ||
| let mut node_4_b = roots_b.get_child_mut(4_u64).expect("No child 4 found"); | ||
| node_4_b.children.insert_child(3_u64, 'f'); | ||
| node_4_b.children.insert_child(2_u64, 'g'); | ||
| let mut node_2_b = node_4_b | ||
| .children | ||
| .get_child_mut(2_u64) | ||
| .expect("No child 2 found"); | ||
| node_2_b.children.insert_child(1_u64, 'h'); | ||
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| mem::swap(&mut node_1_a.children, &mut node_4_b.children); | ||
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| // node 1 from tree a now believes it is node 4 from tree b | ||
| assert_eq!(node_1_a.id(), 4_u64, "Node 1 id should be 4"); | ||
| // however it still contains the item from tree a | ||
| assert_eq!(*node_1_a.item, 'a', "Node 1 item should be 'a'"); | ||
| // and we can access the nodes in tree b, that node 4 was able to | ||
| assert_eq!( | ||
| *node_1_a.children.get_child(2_u64).unwrap().item, | ||
| 'g', | ||
| "Node 2 item in tree b should be g" | ||
| ); |
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It's not clear to me that this test is sufficiently useless to justify removing. This is both:
- an operation which can be performed safely
- A weird thing to do.
and so I think we should test that it doesn't cause UB.
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Yes this was my motivation for having the test, or something similar, as mem::swap should be safe, but wanted to make sure that doing something with it wouldn't allow any of the preconditions to be broken (specifically that you couldn't access a parent from a child)
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I guess I'll re-add it with a comment, then. I'll try to make a shorter version.
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Make tests more spread out and more readable.
Add comments detailing the state of the arena being tested.
Fix a lifetime error in unsafe API.
Remove the
mem::swaptest. While the operation it was testing was possible, sharing data between two separate arenas isn't meant to be part of the API and is unlikely to happen in the wild.Rename Arena[Ref/Mut]Children to Arena[Ref/Mut]List
Rename a lot of methods.
Rework documentation.
Unify safe and unsafe APIs.