Re: [PATCH v7 4/6] rust: str: implement `strip_prefix` for `BStr`

[Daniel Almeida]

Hi Andreas,

> On 18 Feb 2025, at 10:00, Andreas Hindborg <a.hindborg@xxxxxxxxxx> wrote:
> 
> Implement `strip_prefix` for `BStr` by deferring to `slice::strip_prefix`
> on the underlying `&[u8]`.
> 
> Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>
> Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
> ---
> 
> It is also possible to get this method by implementing
> `core::slice::SlicePattern` for `BStr`. `SlicePattern` is unstable, so this
> seems more reasonable.
> ---
> rust/kernel/str.rs | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
> 
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index c6bd2c69543dc..db272d2198fcc 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -31,6 +31,22 @@ pub const fn from_bytes(bytes: &[u8]) -> &Self {
>         // SAFETY: `BStr` is transparent to `[u8]`.
>         unsafe { &*(bytes as *const [u8] as *const BStr) }
>     }
> +
> +    /// Strip a prefix from `self`. Delegates to [`slice::strip_prefix`].
> +    ///
> +    /// # Example
> +    /// ```
> +    /// use kernel::b_str;
> +    /// assert_eq!(Some(b_str!("bar")), b_str!("foobar").strip_prefix(b_str!("foo")));
> +    /// assert_eq!(None, b_str!("foobar").strip_prefix(b_str!("bar")));
> +    /// assert_eq!(Some(b_str!("foobar")), b_str!("foobar").strip_prefix(b_str!("")));
> +    /// assert_eq!(Some(b_str!("")), b_str!("foobar").strip_prefix(b_str!("foobar")));
> +    /// ```

This is passing.

> +    pub fn strip_prefix(&self, pattern: impl AsRef<Self>) -> Option<&BStr> {
> +        self.deref()
> +            .strip_prefix(pattern.as_ref().deref())
> +            .map(Self::from_bytes)
> +    }
> }
> 
> impl fmt::Display for BStr {
> 
> -- 
> 2.47.0
> 
> 

Reviewed-by: Daniel Almeida <daniel.almeida@xxxxxxxxxxxxx>