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// SPDX-License-Identifier: GPL-2.0
//! Bit manipulation macros.
//!
//! C header: [`include/linux/bits.h`](srctree/include/linux/bits.h)
use crate::prelude::*;
use core::ops::RangeInclusive;
use macros::paste;
macro_rules! impl_bit_fn {
(
$ty:ty
) => {
paste! {
/// Computes `1 << n` if `n` is in bounds, i.e.: if `n` is smaller than
/// the maximum number of bits supported by the type.
///
/// Returns [`None`] otherwise.
#[inline]
pub fn [<checked_bit_ $ty>](n: u32) -> Option<$ty> {
(1 as $ty).checked_shl(n)
}
/// Computes `1 << n` by performing a compile-time assertion that `n` is
/// in bounds.
///
/// This version is the default and should be used if `n` is known at
/// compile time.
#[inline]
pub const fn [<bit_ $ty>](n: u32) -> $ty {
build_assert!(n < <$ty>::BITS);
(1 as $ty) << n
}
}
};
}
impl_bit_fn!(u64);
impl_bit_fn!(u32);
impl_bit_fn!(u16);
impl_bit_fn!(u8);
macro_rules! impl_genmask_fn {
(
$ty:ty,
$(#[$genmask_checked_ex:meta])*,
$(#[$genmask_ex:meta])*
) => {
paste! {
/// Creates a contiguous bitmask for the given range by validating
/// the range at runtime.
///
/// Returns [`None`] if the range is invalid, i.e.: if the start is
/// greater than the end or if the range is outside of the
/// representable range for the type.
$(#[$genmask_checked_ex])*
#[inline]
pub fn [<genmask_checked_ $ty>](range: RangeInclusive<u32>) -> Option<$ty> {
let start = *range.start();
let end = *range.end();
if start > end {
return None;
}
let high = [<checked_bit_ $ty>](end)?;
let low = [<checked_bit_ $ty>](start)?;
Some((high | (high - 1)) & !(low - 1))
}
/// Creates a compile-time contiguous bitmask for the given range by
/// performing a compile-time assertion that the range is valid.
///
/// This version is the default and should be used if the range is known
/// at compile time.
$(#[$genmask_ex])*
#[inline]
pub const fn [<genmask_ $ty>](range: RangeInclusive<u32>) -> $ty {
let start = *range.start();
let end = *range.end();
build_assert!(start <= end);
let high = [<bit_ $ty>](end);
let low = [<bit_ $ty>](start);
(high | (high - 1)) & !(low - 1)
}
}
};
}
impl_genmask_fn!(
u64,
/// # Examples
///
/// ```
/// # #![expect(clippy::reversed_empty_ranges)]
/// # use kernel::bits::genmask_checked_u64;
/// assert_eq!(genmask_checked_u64(0..=0), Some(0b1));
/// assert_eq!(genmask_checked_u64(0..=63), Some(u64::MAX));
/// assert_eq!(genmask_checked_u64(21..=39), Some(0x0000_00ff_ffe0_0000));
///
/// // `80` is out of the supported bit range.
/// assert_eq!(genmask_checked_u64(21..=80), None);
///
/// // Invalid range where the start is bigger than the end.
/// assert_eq!(genmask_checked_u64(15..=8), None);
/// ```
,
/// # Examples
///
/// ```
/// # use kernel::bits::genmask_u64;
/// assert_eq!(genmask_u64(21..=39), 0x0000_00ff_ffe0_0000);
/// assert_eq!(genmask_u64(0..=0), 0b1);
/// assert_eq!(genmask_u64(0..=63), u64::MAX);
/// ```
);
impl_genmask_fn!(
u32,
/// # Examples
///
/// ```
/// # #![expect(clippy::reversed_empty_ranges)]
/// # use kernel::bits::genmask_checked_u32;
/// assert_eq!(genmask_checked_u32(0..=0), Some(0b1));
/// assert_eq!(genmask_checked_u32(0..=31), Some(u32::MAX));
/// assert_eq!(genmask_checked_u32(21..=31), Some(0xffe0_0000));
///
/// // `40` is out of the supported bit range.
/// assert_eq!(genmask_checked_u32(21..=40), None);
///
/// // Invalid range where the start is bigger than the end.
/// assert_eq!(genmask_checked_u32(15..=8), None);
/// ```
,
/// # Examples
///
/// ```
/// # use kernel::bits::genmask_u32;
/// assert_eq!(genmask_u32(21..=31), 0xffe0_0000);
/// assert_eq!(genmask_u32(0..=0), 0b1);
/// assert_eq!(genmask_u32(0..=31), u32::MAX);
/// ```
);
impl_genmask_fn!(
u16,
/// # Examples
///
/// ```
/// # #![expect(clippy::reversed_empty_ranges)]
/// # use kernel::bits::genmask_checked_u16;
/// assert_eq!(genmask_checked_u16(0..=0), Some(0b1));
/// assert_eq!(genmask_checked_u16(0..=15), Some(u16::MAX));
/// assert_eq!(genmask_checked_u16(6..=15), Some(0xffc0));
///
/// // `20` is out of the supported bit range.
/// assert_eq!(genmask_checked_u16(6..=20), None);
///
/// // Invalid range where the start is bigger than the end.
/// assert_eq!(genmask_checked_u16(10..=5), None);
/// ```
,
/// # Examples
///
/// ```
/// # use kernel::bits::genmask_u16;
/// assert_eq!(genmask_u16(6..=15), 0xffc0);
/// assert_eq!(genmask_u16(0..=0), 0b1);
/// assert_eq!(genmask_u16(0..=15), u16::MAX);
/// ```
);
impl_genmask_fn!(
u8,
/// # Examples
///
/// ```
/// # #![expect(clippy::reversed_empty_ranges)]
/// # use kernel::bits::genmask_checked_u8;
/// assert_eq!(genmask_checked_u8(0..=0), Some(0b1));
/// assert_eq!(genmask_checked_u8(0..=7), Some(u8::MAX));
/// assert_eq!(genmask_checked_u8(6..=7), Some(0xc0));
///
/// // `10` is out of the supported bit range.
/// assert_eq!(genmask_checked_u8(6..=10), None);
///
/// // Invalid range where the start is bigger than the end.
/// assert_eq!(genmask_checked_u8(5..=2), None);
/// ```
,
/// # Examples
///
/// ```
/// # use kernel::bits::genmask_u8;
/// assert_eq!(genmask_u8(6..=7), 0xc0);
/// assert_eq!(genmask_u8(0..=0), 0b1);
/// assert_eq!(genmask_u8(0..=7), u8::MAX);
/// ```
);
|
