linux-kernel - Re: [PATCH 03/10] rust: xarray: add `contains

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Message-ID: <CAJ-ks9mqwaWMc0MTGOk+rKSM8W8spRmwiLGCkEjcSvF+d7QW7g@mail.gmail.com>
Date: Mon, 29 Dec 2025 10:59:59 -0500
From: Tamir Duberstein <tamird@...il.com>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <lossin@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
	Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, Daniel Gomez <da.gomez@...nel.org>, 
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/10] rust: xarray: add `contains_index` method

On Wed, Dec 3, 2025 at 5:27 PM Andreas Hindborg <a.hindborg@...nel.org> wrote:
>
> 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`.

It isn't clear when you'd want this API, and neither this nor the
example are particularly motivating.

>
> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.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
>
>