[PATCH v3 03/12] rust: xarray: add `contains_index` method

[Andreas Hindborg <a.hindborg@kernel.org>]

Add a convenience method `contains_index` to check whether an element
exists at a given index in the XArray. This method provides a more
ergonomic API compared to calling `get` and checking for `Some`.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/xarray.rs | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs
index d9762c6bef19c..ede48b5e1dba3 100644
--- a/rust/kernel/xarray.rs
+++ b/rust/kernel/xarray.rs
@@ -218,6 +218,27 @@ fn load<F, U>(&self, index: usize, f: F) -> Option<U>
         Some(f(ptr))
     }
 
+    /// Checks if the XArray contains an element at the specified index.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use kernel::{alloc::{flags::GFP_KERNEL, kbox::KBox}, xarray::{AllocKind, XArray}};
+    /// let xa = KBox::pin_init(XArray::new(AllocKind::Alloc), GFP_KERNEL)?;
+    ///
+    /// let mut guard = xa.lock();
+    /// assert_eq!(guard.contains_index(42), false);
+    ///
+    /// guard.store(42, KBox::new(0u32, GFP_KERNEL)?, GFP_KERNEL)?;
+    ///
+    /// assert_eq!(guard.contains_index(42), true);
+    ///
+    /// # Ok::<(), kernel::error::Error>(())
+    /// ```
+    pub fn contains_index(&self, index: usize) -> bool {
+        self.get(index).is_some()
+    }
+
     /// Provides a reference to the element at the given index.
     pub fn get(&self, index: usize) -> Option<T::Borrowed<'_>> {
         self.load(index, |ptr| {

-- 
2.51.2