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Diffstat (limited to 'library/core/src/mem/valid_align.rs')
| -rw-r--r-- | library/core/src/mem/valid_align.rs | 247 |
1 files changed, 247 insertions, 0 deletions
diff --git a/library/core/src/mem/valid_align.rs b/library/core/src/mem/valid_align.rs new file mode 100644 index 000000000..fcfa95120 --- /dev/null +++ b/library/core/src/mem/valid_align.rs @@ -0,0 +1,247 @@ +use crate::convert::TryFrom; +use crate::num::NonZeroUsize; +use crate::{cmp, fmt, hash, mem, num}; + +/// A type storing a `usize` which is a power of two, and thus +/// represents a possible alignment in the rust abstract machine. +/// +/// Note that particularly large alignments, while representable in this type, +/// are likely not to be supported by actual allocators and linkers. +#[derive(Copy, Clone)] +#[repr(transparent)] +pub(crate) struct ValidAlign(ValidAlignEnum); + +// ValidAlign is `repr(usize)`, but via extra steps. +const _: () = assert!(mem::size_of::<ValidAlign>() == mem::size_of::<usize>()); +const _: () = assert!(mem::align_of::<ValidAlign>() == mem::align_of::<usize>()); + +impl ValidAlign { + /// Creates a `ValidAlign` from a power-of-two `usize`. + /// + /// # Safety + /// + /// `align` must be a power of two. + /// + /// Equivalently, it must be `1 << exp` for some `exp` in `0..usize::BITS`. + /// It must *not* be zero. + #[inline] + pub(crate) const unsafe fn new_unchecked(align: usize) -> Self { + debug_assert!(align.is_power_of_two()); + + // SAFETY: By precondition, this must be a power of two, and + // our variants encompass all possible powers of two. + unsafe { mem::transmute::<usize, ValidAlign>(align) } + } + + #[inline] + pub(crate) const fn as_nonzero(self) -> NonZeroUsize { + // SAFETY: All the discriminants are non-zero. + unsafe { NonZeroUsize::new_unchecked(self.0 as usize) } + } + + /// Returns the base 2 logarithm of the alignment. + /// + /// This is always exact, as `self` represents a power of two. + #[inline] + pub(crate) fn log2(self) -> u32 { + self.as_nonzero().trailing_zeros() + } +} + +impl fmt::Debug for ValidAlign { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "{:?} (1 << {:?})", self.as_nonzero(), self.log2()) + } +} + +impl TryFrom<NonZeroUsize> for ValidAlign { + type Error = num::TryFromIntError; + + #[inline] + fn try_from(align: NonZeroUsize) -> Result<ValidAlign, Self::Error> { + if align.is_power_of_two() { + // SAFETY: Just checked for power-of-two + unsafe { Ok(ValidAlign::new_unchecked(align.get())) } + } else { + Err(num::TryFromIntError(())) + } + } +} + +impl TryFrom<usize> for ValidAlign { + type Error = num::TryFromIntError; + + #[inline] + fn try_from(align: usize) -> Result<ValidAlign, Self::Error> { + if align.is_power_of_two() { + // SAFETY: Just checked for power-of-two + unsafe { Ok(ValidAlign::new_unchecked(align)) } + } else { + Err(num::TryFromIntError(())) + } + } +} + +impl cmp::Eq for ValidAlign {} + +impl cmp::PartialEq for ValidAlign { + #[inline] + fn eq(&self, other: &Self) -> bool { + self.as_nonzero() == other.as_nonzero() + } +} + +impl cmp::Ord for ValidAlign { + #[inline] + fn cmp(&self, other: &Self) -> cmp::Ordering { + self.as_nonzero().cmp(&other.as_nonzero()) + } +} + +impl cmp::PartialOrd for ValidAlign { + #[inline] + fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> { + Some(self.cmp(other)) + } +} + +impl hash::Hash for ValidAlign { + #[inline] + fn hash<H: hash::Hasher>(&self, state: &mut H) { + self.as_nonzero().hash(state) + } +} + +#[cfg(target_pointer_width = "16")] +type ValidAlignEnum = ValidAlignEnum16; +#[cfg(target_pointer_width = "32")] +type ValidAlignEnum = ValidAlignEnum32; +#[cfg(target_pointer_width = "64")] +type ValidAlignEnum = ValidAlignEnum64; + +#[derive(Copy, Clone)] +#[repr(u16)] +enum ValidAlignEnum16 { + _Align1Shl0 = 1 << 0, + _Align1Shl1 = 1 << 1, + _Align1Shl2 = 1 << 2, + _Align1Shl3 = 1 << 3, + _Align1Shl4 = 1 << 4, + _Align1Shl5 = 1 << 5, + _Align1Shl6 = 1 << 6, + _Align1Shl7 = 1 << 7, + _Align1Shl8 = 1 << 8, + _Align1Shl9 = 1 << 9, + _Align1Shl10 = 1 << 10, + _Align1Shl11 = 1 << 11, + _Align1Shl12 = 1 << 12, + _Align1Shl13 = 1 << 13, + _Align1Shl14 = 1 << 14, + _Align1Shl15 = 1 << 15, +} + +#[derive(Copy, Clone)] +#[repr(u32)] +enum ValidAlignEnum32 { + _Align1Shl0 = 1 << 0, + _Align1Shl1 = 1 << 1, + _Align1Shl2 = 1 << 2, + _Align1Shl3 = 1 << 3, + _Align1Shl4 = 1 << 4, + _Align1Shl5 = 1 << 5, + _Align1Shl6 = 1 << 6, + _Align1Shl7 = 1 << 7, + _Align1Shl8 = 1 << 8, + _Align1Shl9 = 1 << 9, + _Align1Shl10 = 1 << 10, + _Align1Shl11 = 1 << 11, + _Align1Shl12 = 1 << 12, + _Align1Shl13 = 1 << 13, + _Align1Shl14 = 1 << 14, + _Align1Shl15 = 1 << 15, + _Align1Shl16 = 1 << 16, + _Align1Shl17 = 1 << 17, + _Align1Shl18 = 1 << 18, + _Align1Shl19 = 1 << 19, + _Align1Shl20 = 1 << 20, + _Align1Shl21 = 1 << 21, + _Align1Shl22 = 1 << 22, + _Align1Shl23 = 1 << 23, + _Align1Shl24 = 1 << 24, + _Align1Shl25 = 1 << 25, + _Align1Shl26 = 1 << 26, + _Align1Shl27 = 1 << 27, + _Align1Shl28 = 1 << 28, + _Align1Shl29 = 1 << 29, + _Align1Shl30 = 1 << 30, + _Align1Shl31 = 1 << 31, +} + +#[derive(Copy, Clone)] +#[repr(u64)] +enum ValidAlignEnum64 { + _Align1Shl0 = 1 << 0, + _Align1Shl1 = 1 << 1, + _Align1Shl2 = 1 << 2, + _Align1Shl3 = 1 << 3, + _Align1Shl4 = 1 << 4, + _Align1Shl5 = 1 << 5, + _Align1Shl6 = 1 << 6, + _Align1Shl7 = 1 << 7, + _Align1Shl8 = 1 << 8, + _Align1Shl9 = 1 << 9, + _Align1Shl10 = 1 << 10, + _Align1Shl11 = 1 << 11, + _Align1Shl12 = 1 << 12, + _Align1Shl13 = 1 << 13, + _Align1Shl14 = 1 << 14, + _Align1Shl15 = 1 << 15, + _Align1Shl16 = 1 << 16, + _Align1Shl17 = 1 << 17, + _Align1Shl18 = 1 << 18, + _Align1Shl19 = 1 << 19, + _Align1Shl20 = 1 << 20, + _Align1Shl21 = 1 << 21, + _Align1Shl22 = 1 << 22, + _Align1Shl23 = 1 << 23, + _Align1Shl24 = 1 << 24, + _Align1Shl25 = 1 << 25, + _Align1Shl26 = 1 << 26, + _Align1Shl27 = 1 << 27, + _Align1Shl28 = 1 << 28, + _Align1Shl29 = 1 << 29, + _Align1Shl30 = 1 << 30, + _Align1Shl31 = 1 << 31, + _Align1Shl32 = 1 << 32, + _Align1Shl33 = 1 << 33, + _Align1Shl34 = 1 << 34, + _Align1Shl35 = 1 << 35, + _Align1Shl36 = 1 << 36, + _Align1Shl37 = 1 << 37, + _Align1Shl38 = 1 << 38, + _Align1Shl39 = 1 << 39, + _Align1Shl40 = 1 << 40, + _Align1Shl41 = 1 << 41, + _Align1Shl42 = 1 << 42, + _Align1Shl43 = 1 << 43, + _Align1Shl44 = 1 << 44, + _Align1Shl45 = 1 << 45, + _Align1Shl46 = 1 << 46, + _Align1Shl47 = 1 << 47, + _Align1Shl48 = 1 << 48, + _Align1Shl49 = 1 << 49, + _Align1Shl50 = 1 << 50, + _Align1Shl51 = 1 << 51, + _Align1Shl52 = 1 << 52, + _Align1Shl53 = 1 << 53, + _Align1Shl54 = 1 << 54, + _Align1Shl55 = 1 << 55, + _Align1Shl56 = 1 << 56, + _Align1Shl57 = 1 << 57, + _Align1Shl58 = 1 << 58, + _Align1Shl59 = 1 << 59, + _Align1Shl60 = 1 << 60, + _Align1Shl61 = 1 << 61, + _Align1Shl62 = 1 << 62, + _Align1Shl63 = 1 << 63, +} |