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Take a single root node in range_search #71523

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merged 1 commit into from
Apr 25, 2020
+7 −10
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Take a single root node in range_search #71523

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17 changes: 7 additions & 10 deletions src/liballoc/collections/btree/map.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1034,9 +1034,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
R: RangeBounds<T>,
{
if let Some(root) = &self.root {
let root1 = root.as_ref();
let root2 = root.as_ref();
let (f, b) = range_search(root1, root2, range);
let (f, b) = range_search(root.as_ref(), range);

Range { front: Some(f), back: Some(b) }
} else {
Expand Down Expand Up @@ -1082,9 +1080,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
R: RangeBounds<T>,
{
if let Some(root) = &mut self.root {
let root1 = root.as_mut();
let root2 = unsafe { ptr::read(&root1) };
let (f, b) = range_search(root1, root2, range);
let (f, b) = range_search(root.as_mut(), range);

RangeMut { front: Some(f), back: Some(b), _marker: PhantomData }
} else {
Expand Down Expand Up @@ -2043,8 +2039,7 @@ where
}

fn range_search<BorrowType, K, V, Q: ?Sized, R: RangeBounds<Q>>(
root1: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
root2: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
root: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
range: R,
) -> (
Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>,
Expand All @@ -2064,8 +2059,10 @@ where
_ => {}
};

let mut min_node = root1;
let mut max_node = root2;
// We duplicate the root NodeRef here -- we will never access it in a way
// that overlaps references obtained from the root.
Comment on lines +2062 to +2063
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I don't understand that sentence (but I don't have to). In an emptied tree, range_search will return two references to the same and only edge. Is that no overlap?

let mut min_node = unsafe { ptr::read(&root) };
let mut max_node = root;
let mut min_found = false;
let mut max_found = false;

Expand Down