linux-kernel - Re: [PATCH v4 2/4] rust: str: implement `strip

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Message-ID: <20250115193524.5c07a472.gary@garyguo.net>
Date: Wed, 15 Jan 2025 19:35:24 +0000
From: Gary Guo <gary@...yguo.net>
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>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, Alice
 Ryhl <aliceryhl@...gle.com>, Masahiro Yamada <masahiroy@...nel.org>, Nathan
 Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, Luis
 Chamberlain <mcgrof@...nel.org>, Trevor Gross <tmgross@...ch.edu>, Adam
 Bratschi-Kaye <ark.email@...il.com>, rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org, Petr Pavlu
 <petr.pavlu@...e.com>, Sami Tolvanen <samitolvanen@...gle.com>, Daniel
 Gomez <da.gomez@...sung.com>, Simona Vetter <simona.vetter@...ll.ch>, Greg
 KH <gregkh@...uxfoundation.org>, linux-modules@...r.kernel.org
Subject: Re: [PATCH v4 2/4] rust: str: implement `strip_prefix` for `BStr`

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

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

Reviewed-by: Gary Guo <gary@...yguo.net>

> 
> ---
> 
> 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 {
>