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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:11:28 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:11:28 +0000 |
commit | 94a0819fe3a0d679c3042a77bfe6a2afc505daea (patch) | |
tree | 2b827afe6a05f3538db3f7803a88c4587fe85648 /library/core/src/ptr/alignment.rs | |
parent | Adding upstream version 1.64.0+dfsg1. (diff) | |
download | rustc-94a0819fe3a0d679c3042a77bfe6a2afc505daea.tar.xz rustc-94a0819fe3a0d679c3042a77bfe6a2afc505daea.zip |
Adding upstream version 1.66.0+dfsg1.upstream/1.66.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'library/core/src/ptr/alignment.rs')
-rw-r--r-- | library/core/src/ptr/alignment.rs | 326 |
1 files changed, 326 insertions, 0 deletions
diff --git a/library/core/src/ptr/alignment.rs b/library/core/src/ptr/alignment.rs new file mode 100644 index 000000000..1390e09dd --- /dev/null +++ b/library/core/src/ptr/alignment.rs @@ -0,0 +1,326 @@ +use crate::convert::{TryFrom, TryInto}; +use crate::intrinsics::assert_unsafe_precondition; +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. +#[unstable(feature = "ptr_alignment_type", issue = "102070")] +#[derive(Copy, Clone, Eq, PartialEq)] +#[repr(transparent)] +pub struct Alignment(AlignmentEnum); + +// Alignment is `repr(usize)`, but via extra steps. +const _: () = assert!(mem::size_of::<Alignment>() == mem::size_of::<usize>()); +const _: () = assert!(mem::align_of::<Alignment>() == mem::align_of::<usize>()); + +fn _alignment_can_be_structurally_matched(a: Alignment) -> bool { + matches!(a, Alignment::MIN) +} + +impl Alignment { + /// The smallest possible alignment, 1. + /// + /// All addresses are always aligned at least this much. + /// + /// # Examples + /// + /// ``` + /// #![feature(ptr_alignment_type)] + /// use std::ptr::Alignment; + /// + /// assert_eq!(Alignment::MIN.as_usize(), 1); + /// ``` + #[unstable(feature = "ptr_alignment_type", issue = "102070")] + pub const MIN: Self = Self(AlignmentEnum::_Align1Shl0); + + /// Returns the alignment for a type. + /// + /// This provides the same numerical value as [`mem::align_of`], + /// but in an `Alignment` instead of a `usize. + #[unstable(feature = "ptr_alignment_type", issue = "102070")] + #[inline] + pub const fn of<T>() -> Self { + // SAFETY: rustc ensures that type alignment is always a power of two. + unsafe { Alignment::new_unchecked(mem::align_of::<T>()) } + } + + /// Creates an `Alignment` from a `usize`, or returns `None` if it's + /// not a power of two. + /// + /// Note that `0` is not a power of two, nor a valid alignment. + #[unstable(feature = "ptr_alignment_type", issue = "102070")] + #[inline] + pub const fn new(align: usize) -> Option<Self> { + if align.is_power_of_two() { + // SAFETY: Just checked it only has one bit set + Some(unsafe { Self::new_unchecked(align) }) + } else { + None + } + } + + /// Creates an `Alignment` 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. + #[unstable(feature = "ptr_alignment_type", issue = "102070")] + #[rustc_const_unstable(feature = "ptr_alignment_type", issue = "102070")] + #[inline] + pub const unsafe fn new_unchecked(align: usize) -> Self { + // SAFETY: Precondition passed to the caller. + unsafe { + assert_unsafe_precondition!( + "Alignment::new_unchecked requires a power of two", + (align: usize) => 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, Alignment>(align) } + } + + /// Returns the alignment as a [`usize`] + #[unstable(feature = "ptr_alignment_type", issue = "102070")] + #[rustc_const_unstable(feature = "ptr_alignment_type", issue = "102070")] + #[inline] + pub const fn as_usize(self) -> usize { + self.0 as usize + } + + /// Returns the alignment as a [`NonZeroUsize`] + #[unstable(feature = "ptr_alignment_type", issue = "102070")] + #[inline] + pub const fn as_nonzero(self) -> NonZeroUsize { + // SAFETY: All the discriminants are non-zero. + unsafe { NonZeroUsize::new_unchecked(self.as_usize()) } + } + + /// Returns the base-2 logarithm of the alignment. + /// + /// This is always exact, as `self` represents a power of two. + /// + /// # Examples + /// + /// ``` + /// #![feature(ptr_alignment_type)] + /// use std::ptr::Alignment; + /// + /// assert_eq!(Alignment::of::<u8>().log2(), 0); + /// assert_eq!(Alignment::new(1024).unwrap().log2(), 10); + /// ``` + #[unstable(feature = "ptr_alignment_type", issue = "102070")] + #[inline] + pub fn log2(self) -> u32 { + self.as_nonzero().trailing_zeros() + } +} + +#[unstable(feature = "ptr_alignment_type", issue = "102070")] +impl fmt::Debug for Alignment { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "{:?} (1 << {:?})", self.as_nonzero(), self.log2()) + } +} + +#[unstable(feature = "ptr_alignment_type", issue = "102070")] +impl TryFrom<NonZeroUsize> for Alignment { + type Error = num::TryFromIntError; + + #[inline] + fn try_from(align: NonZeroUsize) -> Result<Alignment, Self::Error> { + align.get().try_into() + } +} + +#[unstable(feature = "ptr_alignment_type", issue = "102070")] +impl TryFrom<usize> for Alignment { + type Error = num::TryFromIntError; + + #[inline] + fn try_from(align: usize) -> Result<Alignment, Self::Error> { + Self::new(align).ok_or(num::TryFromIntError(())) + } +} + +#[unstable(feature = "ptr_alignment_type", issue = "102070")] +impl From<Alignment> for NonZeroUsize { + #[inline] + fn from(align: Alignment) -> NonZeroUsize { + align.as_nonzero() + } +} + +#[unstable(feature = "ptr_alignment_type", issue = "102070")] +impl From<Alignment> for usize { + #[inline] + fn from(align: Alignment) -> usize { + align.as_usize() + } +} + +#[unstable(feature = "ptr_alignment_type", issue = "102070")] +impl cmp::Ord for Alignment { + #[inline] + fn cmp(&self, other: &Self) -> cmp::Ordering { + self.as_nonzero().cmp(&other.as_nonzero()) + } +} + +#[unstable(feature = "ptr_alignment_type", issue = "102070")] +impl cmp::PartialOrd for Alignment { + #[inline] + fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> { + Some(self.cmp(other)) + } +} + +#[unstable(feature = "ptr_alignment_type", issue = "102070")] +impl hash::Hash for Alignment { + #[inline] + fn hash<H: hash::Hasher>(&self, state: &mut H) { + self.as_nonzero().hash(state) + } +} + +#[cfg(target_pointer_width = "16")] +type AlignmentEnum = AlignmentEnum16; +#[cfg(target_pointer_width = "32")] +type AlignmentEnum = AlignmentEnum32; +#[cfg(target_pointer_width = "64")] +type AlignmentEnum = AlignmentEnum64; + +#[derive(Copy, Clone, Eq, PartialEq)] +#[repr(u16)] +enum AlignmentEnum16 { + _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, Eq, PartialEq)] +#[repr(u32)] +enum AlignmentEnum32 { + _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, Eq, PartialEq)] +#[repr(u64)] +enum AlignmentEnum64 { + _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, +} |