On Sat Mar 15, 2025 at 12:15 PM CET, Andrew Ballance wrote: > On Sat, Mar 15, 2025 at 10:09:26AM +0000, Benno Lossin wrote: >> On Sat Mar 15, 2025 at 3:42 AM CET, Andrew Ballance wrote: >> > implements the equivalent to the std's Vec::truncate >> > on the kernel's Vec type. >> > >> > Signed-off-by: Andrew Ballance <andrewjballance@xxxxxxxxx> >> > --- >> > rust/kernel/alloc/kvec.rs | 36 ++++++++++++++++++++++++++++++++++++ >> > 1 file changed, 36 insertions(+) >> > >> > diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs >> > index ae9d072741ce..75e9feebb81f 100644 >> > --- a/rust/kernel/alloc/kvec.rs >> > +++ b/rust/kernel/alloc/kvec.rs >> > @@ -452,6 +452,42 @@ pub fn reserve(&mut self, additional: usize, flags: Flags) -> Result<(), AllocEr >> > >> > Ok(()) >> > } >> > + >> > + /// Shortens the vector, setting the length to `len` and drops the removed values. >> > + /// If `len` is greater than or equal to the current length, this does nothing. >> > + /// >> > + /// This has no effect on the capacity and will not allocate. >> > + /// # Examples >> > + /// ``` >> > + /// let mut v = kernel::kvec![1, 2, 3]?; >> > + /// v.truncate(1); >> > + /// assert_eq!(v.len(), 1); >> > + /// assert_eq!(&v, &[1]); >> > + /// >> > + /// # Ok::<(), Error>(()) >> > + /// ``` >> > + pub fn truncate(&mut self, len: usize) { >> > + if len >= self.len() { >> > + return; >> > + } >> > + >> > + // [new_len, len) is guaranteed to be valid because [0, len) is guaranteed to be valid >> > + let drop_range = len..self.len(); >> > + >> > + // SAFETY: >> > + // we can safely ignore the bounds check because we already did our own check >> > + let ptr: *mut [T] = unsafe { self.get_unchecked_mut(drop_range) }; >> >> What's this `get_unchecked_mut` method, I don't see it in `rust-next` or >> `alloc-next`. > > Vec derefs into a slice which implements get_uncheked_mut > https://rust.docs.kernel.org/next/kernel/alloc/kvec/struct.Vec.html#method.get_unchecked_mut Ah, I forgot about that... Can you change the safety comment to: // SAFETY: `drop_range` is a subrange of `[0, len)` by the bounds check above. --- Cheers, Benno