1

rust: rbtree: add iterator

- Add Iterator implementation for `RBTree`, allowing
  iteration over (key, value) pairs in key order.
- Add individual `keys()` and `values()` functions to iterate over keys
  or values alone.
- Update doctests to use iteration instead of explicitly getting items.

Iteration is needed by the binder driver to enumerate all values in a
tree for oneway spam detection [1].

Link: https://lore.kernel.org/rust-for-linux/20231101-rust-binder-v1-17-08ba9197f637@google.com/ [1]
Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Matt Gilbride <mattgilbride@google.com>
Link: https://lore.kernel.org/r/20240822-b4-rbtree-v12-2-014561758a57@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Wedson Almeida Filho 2024-08-22 16:37:54 +00:00 committed by Miguel Ojeda
parent a0d13aac70
commit e601f1bb8e

View File

@ -42,14 +42,30 @@ use core::{
/// assert_eq!(tree.get(&30).unwrap(), &300);
/// }
///
/// // Iterate over the nodes we just inserted.
/// {
/// let mut iter = tree.iter();
/// assert_eq!(iter.next().unwrap(), (&10, &100));
/// assert_eq!(iter.next().unwrap(), (&20, &200));
/// assert_eq!(iter.next().unwrap(), (&30, &300));
/// assert!(iter.next().is_none());
/// }
///
/// // Print all elements.
/// for (key, value) in &tree {
/// pr_info!("{} = {}\n", key, value);
/// }
///
/// // Replace one of the elements.
/// tree.try_create_and_insert(10, 1000, flags::GFP_KERNEL)?;
///
/// // Check that the tree reflects the replacement.
/// {
/// assert_eq!(tree.get(&10).unwrap(), &1000);
/// assert_eq!(tree.get(&20).unwrap(), &200);
/// assert_eq!(tree.get(&30).unwrap(), &300);
/// let mut iter = tree.iter();
/// assert_eq!(iter.next().unwrap(), (&10, &1000));
/// assert_eq!(iter.next().unwrap(), (&20, &200));
/// assert_eq!(iter.next().unwrap(), (&30, &300));
/// assert!(iter.next().is_none());
/// }
///
/// // Change the value of one of the elements.
@ -57,9 +73,11 @@ use core::{
///
/// // Check that the tree reflects the update.
/// {
/// assert_eq!(tree.get(&10).unwrap(), &1000);
/// assert_eq!(tree.get(&20).unwrap(), &200);
/// assert_eq!(tree.get(&30).unwrap(), &3000);
/// let mut iter = tree.iter();
/// assert_eq!(iter.next().unwrap(), (&10, &1000));
/// assert_eq!(iter.next().unwrap(), (&20, &200));
/// assert_eq!(iter.next().unwrap(), (&30, &3000));
/// assert!(iter.next().is_none());
/// }
///
/// // Remove an element.
@ -67,9 +85,10 @@ use core::{
///
/// // Check that the tree reflects the removal.
/// {
/// assert_eq!(tree.get(&10), None);
/// assert_eq!(tree.get(&20).unwrap(), &200);
/// assert_eq!(tree.get(&30).unwrap(), &3000);
/// let mut iter = tree.iter();
/// assert_eq!(iter.next().unwrap(), (&20, &200));
/// assert_eq!(iter.next().unwrap(), (&30, &3000));
/// assert!(iter.next().is_none());
/// }
///
/// # Ok::<(), Error>(())
@ -109,9 +128,11 @@ use core::{
///
/// // Check the nodes we just inserted.
/// {
/// assert_eq!(tree.get(&10).unwrap(), &100);
/// assert_eq!(tree.get(&20).unwrap(), &200);
/// assert_eq!(tree.get(&30).unwrap(), &300);
/// let mut iter = tree.iter();
/// assert_eq!(iter.next().unwrap(), (&10, &100));
/// assert_eq!(iter.next().unwrap(), (&20, &200));
/// assert_eq!(iter.next().unwrap(), (&30, &300));
/// assert!(iter.next().is_none());
/// }
///
/// // Remove a node, getting back ownership of it.
@ -119,9 +140,10 @@ use core::{
///
/// // Check that the tree reflects the removal.
/// {
/// assert_eq!(tree.get(&10).unwrap(), &100);
/// assert_eq!(tree.get(&20).unwrap(), &200);
/// assert_eq!(tree.get(&30), None);
/// let mut iter = tree.iter();
/// assert_eq!(iter.next().unwrap(), (&10, &100));
/// assert_eq!(iter.next().unwrap(), (&20, &200));
/// assert!(iter.next().is_none());
/// }
///
/// // Create a preallocated reservation that we can re-use later.
@ -133,9 +155,11 @@ use core::{
///
/// // Check that the tree reflect the new insertion.
/// {
/// assert_eq!(tree.get(&10).unwrap(), &100);
/// assert_eq!(tree.get(&15).unwrap(), &150);
/// assert_eq!(tree.get(&20).unwrap(), &200);
/// let mut iter = tree.iter();
/// assert_eq!(iter.next().unwrap(), (&10, &100));
/// assert_eq!(iter.next().unwrap(), (&15, &150));
/// assert_eq!(iter.next().unwrap(), (&20, &200));
/// assert!(iter.next().is_none());
/// }
///
/// # Ok::<(), Error>(())
@ -167,6 +191,26 @@ impl<K, V> RBTree<K, V> {
_p: PhantomData,
}
}
/// Returns an iterator over the tree nodes, sorted by key.
pub fn iter(&self) -> Iter<'_, K, V> {
// INVARIANT: `bindings::rb_first` returns a valid pointer to a tree node given a valid pointer to a tree root.
Iter {
_tree: PhantomData,
// SAFETY: `self.root` is a valid pointer to the tree root.
next: unsafe { bindings::rb_first(&self.root) },
}
}
/// Returns an iterator over the keys of the nodes in the tree, in sorted order.
pub fn keys(&self) -> impl Iterator<Item = &'_ K> {
self.iter().map(|(k, _)| k)
}
/// Returns an iterator over the values of the nodes in the tree, sorted by key.
pub fn values(&self) -> impl Iterator<Item = &'_ V> {
self.iter().map(|(_, v)| v)
}
}
impl<K, V> RBTree<K, V>
@ -358,6 +402,56 @@ impl<K, V> Drop for RBTree<K, V> {
}
}
impl<'a, K, V> IntoIterator for &'a RBTree<K, V> {
type Item = (&'a K, &'a V);
type IntoIter = Iter<'a, K, V>;
fn into_iter(self) -> Self::IntoIter {
self.iter()
}
}
/// An iterator over the nodes of a [`RBTree`].
///
/// Instances are created by calling [`RBTree::iter`].
///
/// # Invariants
/// - `self.next` is a valid pointer.
/// - `self.next` points to a node stored inside of a valid `RBTree`.
pub struct Iter<'a, K, V> {
_tree: PhantomData<&'a RBTree<K, V>>,
next: *mut bindings::rb_node,
}
// SAFETY: The [`Iter`] gives out immutable references to K and V, so it has the same
// thread safety requirements as immutable references.
unsafe impl<'a, K: Sync, V: Sync> Send for Iter<'a, K, V> {}
// SAFETY: The [`Iter`] gives out immutable references to K and V, so it has the same
// thread safety requirements as immutable references.
unsafe impl<'a, K: Sync, V: Sync> Sync for Iter<'a, K, V> {}
impl<'a, K, V> Iterator for Iter<'a, K, V> {
type Item = (&'a K, &'a V);
fn next(&mut self) -> Option<Self::Item> {
if self.next.is_null() {
return None;
}
// SAFETY: By the type invariant of `Iter`, `self.next` is a valid node in an `RBTree`,
// and by the type invariant of `RBTree`, all nodes point to the links field of `Node<K, V>` objects.
let cur = unsafe { container_of!(self.next, Node<K, V>, links) };
// SAFETY: `self.next` is a valid tree node by the type invariants.
self.next = unsafe { bindings::rb_next(self.next) };
// SAFETY: By the same reasoning above, it is safe to dereference the node. Additionally,
// it is ok to return a reference to members because the iterator must outlive it.
Some(unsafe { (&(*cur).key, &(*cur).value) })
}
}
/// A memory reservation for a red-black tree node.
///
///