rust: rbtree: add RBTree::is_empty

Darksonn · ojeda · commit fbcd4b7bf5c9 · 2025-06-29T18:52:41.000+02:00
In Rust Binder I need to be able to determine whether a red/black tree is empty. Thus, add a method for that operation to replace rbtree.iter().next().is_none() This is terrible, so add a method for this purpose. We do not add a RBTree::len method because computing the number of elements requires iterating the entire tree, but checking whether it is empty can be done cheaply. Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Benno Lossin <lossin@kernel.org> Link: https://lore.kernel.org/r/20250616-rbtree-is-empty-v1-1-61f7cfb012e3@google.com [ Adjusted title. - Miguel ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
diff --git a/rust/kernel/rbtree.rs b/rust/kernel/rbtree.rs
@@ -191,6 +191,12 @@ impl<K, V> RBTree<K, V> {
         }
     }
 
+    /// Returns true if this tree is empty.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.root.rb_node.is_null()
+    }
+
     /// Returns an iterator over the tree nodes, sorted by key.
     pub fn iter(&self) -> Iter<'_, K, V> {
         Iter {

Original file line number	Diff line number	Diff line change
`@@ -191,6 +191,12 @@ impl<K, V> RBTree<K, V> {`
`191`	`191`	`}`
`192`	`192`	`}`
`193`	`193`
	`194`	`+ /// Returns true if this tree is empty.`
	`195`	`+ #[inline]`
	`196`	`+ pub fn is_empty(&self) -> bool {`
	`197`	`+ self.root.rb_node.is_null()`
	`198`	`+ }`
	`199`	`+`
`194`	`200`	`/// Returns an iterator over the tree nodes, sorted by key.`
`195`	`201`	`pub fn iter(&self) -> Iter<'_, K, V> {`
`196`	`202`	`Iter {`