Re: [PATCH v4 2/4] rust: str: implement `strip_prefix` for `BStr`

[Gary Guo]

On Thu, 09 Jan 2025 11:54:57 +0100
Andreas Hindborg <a.hindborg@xxxxxxxxxx> wrote:

> Implement `strip_prefix` for `BStr` by deferring to `slice::strip_prefix`
> on the underlying `&[u8]`.
> 
> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>

Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>

> 
> ---
> 
> 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 c441acf76ebd1f14919b6d233edffbbbbf944619..9c446ff1ad7adba7ca09a5ae9df00fd369a32899 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")));
> +    /// ```
> +    pub fn strip_prefix(&self, pattern: &Self) -> Option<&BStr> {
> +        self.deref()
> +            .strip_prefix(pattern.deref())
> +            .map(Self::from_bytes)
> +    }
>  }
>  
>  impl fmt::Display for BStr {
>