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Add methods that perform the shift and return a `Bounded` with the appropriately adjusted bit width. These methods are particularly useful for bitfield extraction. Suggested-by: Alice Ryhl Reviewed-by: Alice Ryhl Reviewed-by: Gary Guo Reviewed-by: Daniel Almeida Tested-by: Dirk Behme Acked-by: Miguel Ojeda Signed-off-by: Alexandre Courbot --- rust/kernel/num/bounded.rs | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/rust/kernel/num/bounded.rs b/rust/kernel/num/bounded.rs index fa81acbdc8c2..2f5f13ecd3d6 100644 --- a/rust/kernel/num/bounded.rs +++ b/rust/kernel/num/bounded.rs @@ -473,6 +473,48 @@ pub fn cast(self) -> Bounded // `N` bits, and with the same signedness. unsafe { Bounded::__new(value) } } + + /// Right-shifts `self` by `SHIFT` and returns the result as a `Bounded<_, RES>`, where `RES >= + /// N - SHIFT`. + /// + /// # Examples + /// + /// ``` + /// use kernel::num::Bounded; + /// + /// let v = Bounded::::new::<0xff00>(); + /// let v_shifted: Bounded:: = v.shr::<8, _>(); + /// + /// assert_eq!(v_shifted.get(), 0xff); + /// ``` + pub fn shr(self) -> Bounded { + const { assert!(RES + SHIFT >= N) } + + // SAFETY: We shift the value right by `SHIFT`, reducing the number of bits needed to + // represent the shifted value by as much, and just asserted that `RES >= N - SHIFT`. + unsafe { Bounded::__new(self.0 >> SHIFT) } + } + + /// Left-shifts `self` by `SHIFT` and returns the result as a `Bounded<_, RES>`, where `RES >= + /// N + SHIFT`. + /// + /// # Examples + /// + /// ``` + /// use kernel::num::Bounded; + /// + /// let v = Bounded::::new::<0xff>(); + /// let v_shifted: Bounded:: = v.shl::<8, _>(); + /// + /// assert_eq!(v_shifted.get(), 0xff00); + /// ``` + pub fn shl(self) -> Bounded { + const { assert!(RES >= N + SHIFT) } + + // SAFETY: We shift the value left by `SHIFT`, augmenting the number of bits needed to + // represent the shifted value by as much, and just asserted that `RES >= N + SHIFT`. + unsafe { Bounded::__new(self.0 << SHIFT) } + } } impl Deref for Bounded -- 2.53.0