Commit dbb0b840 authored by Tamir Duberstein's avatar Tamir Duberstein Committed by Danilo Krummrich
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rust: alloc: add `Vec::dec_len` 



Add `Vec::dec_len` that reduces the length of the receiver. This method
is intended to be used from methods that remove elements from `Vec` such
as `truncate`, `pop`, `remove`, and others. This method is intentionally
not `pub`.

Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Signed-off-by: default avatarTamir Duberstein <tamird@gmail.com>
Link: https://lore.kernel.org/r/20250416-vec-set-len-v4-2-112b222604cd@gmail.com


[ Add #[expect(unused)] to dec_len(). - Danilo ]
Signed-off-by: default avatarDanilo Krummrich <dakr@kernel.org>
parent 47a17a63

rust/kernel/alloc/kvec.rs

+20 −0
Original line number Diff line number Diff line
@@ -201,6 +201,26 @@ pub unsafe fn set_len(&mut self, new_len: usize) { 
        self.len = new_len;

    }



    /// Decreases `self.len` by `count`.

    ///

    /// Returns a mutable slice to the elements forgotten by the vector. It is the caller's

    /// responsibility to drop these elements if necessary.

    ///

    /// # Safety

    ///

    /// - `count` must be less than or equal to `self.len`.

    #[expect(unused)]

    unsafe fn dec_len(&mut self, count: usize) -> &mut [T] {

        debug_assert!(count <= self.len());

        // INVARIANT: We relinquish ownership of the elements within the range `[self.len - count,

        // self.len)`, hence the updated value of `set.len` represents the exact number of elements

        // stored within `self`.

        self.len -= count;

        // SAFETY: The memory after `self.len()` is guaranteed to contain `count` initialized

        // elements of type `T`.

        unsafe { slice::from_raw_parts_mut(self.as_mut_ptr().add(self.len), count) }

    }



    /// Returns a slice of the entire vector.

    #[inline]

    pub fn as_slice(&self) -> &[T] {