On Sun, Mar 16, 2025 at 06:16:42AM -0500, Andrew Ballance wrote: > implement 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..18bcc59f0b38 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; > + } > + > + let drop_range = len..self.len(); > + > + // SAFETY: `drop_range` is a subrange of `[0, len)` by the bounds check above. > + let ptr: *mut [T] = unsafe { self.get_unchecked_mut(drop_range) }; > + > + // SAFETY: > + // - this will always shrink the vector because of the above bounds check > + // - [`new_len`, `self.len`) will be dropped through the call to `drop_in_place` below We've just figured out that this part is not needed after all, sorry for the inconvenience. No need to resend for this though, I can remove this line when applying the patch. > + unsafe { self.set_len(len) }; > + > + // SAFETY: > + // - the dropped values are valid `T`s by the type invariant > + // - we are allowed to invalidate [`new_len`, `old_len`) because we just changed the > + // len, therefore we have exclusive access to [`new_len`, `old_len`) > + unsafe { ptr::drop_in_place(ptr) }; > + } > } > > impl<T: Clone, A: Allocator> Vec<T, A> { > -- > 2.48.1 >