impl more traits for ptr::Alignment, add mask method · rust-lang/rust@114873d (original) (raw)
`@@ -42,6 +42,7 @@ impl Alignment {
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`` /// This provides the same numerical value as [mem::align_of],
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`` /// but in an Alignment instead of a usize.
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`#[unstable(feature = "ptr_alignment_type", issue = "102070")]
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#[rustc_const_unstable(feature = "ptr_alignment_type", issue = "102070")]
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`#[inline]
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`pub const fn of() -> Self {
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`// SAFETY: rustc ensures that type alignment is always a power of two.
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`@@ -53,6 +54,7 @@ impl Alignment {
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`///
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`` /// Note that 0 is not a power of two, nor a valid alignment.
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`#[unstable(feature = "ptr_alignment_type", issue = "102070")]
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#[rustc_const_unstable(feature = "ptr_alignment_type", issue = "102070")]
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`#[inline]
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`pub const fn new(align: usize) -> Option {
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`if align.is_power_of_two() {
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`@@ -98,6 +100,7 @@ impl Alignment {
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`` /// Returns the alignment as a [NonZeroUsize]
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`#[unstable(feature = "ptr_alignment_type", issue = "102070")]
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#[rustc_const_unstable(feature = "ptr_alignment_type", issue = "102070")]
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`#[inline]
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`pub const fn as_nonzero(self) -> NonZeroUsize {
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`// SAFETY: All the discriminants are non-zero.
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`@@ -118,10 +121,42 @@ impl Alignment {
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`/// assert_eq!(Alignment::new(1024).unwrap().log2(), 10);
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```` /// ```
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`#[unstable(feature = "ptr_alignment_type", issue = "102070")]
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#[rustc_const_unstable(feature = "ptr_alignment_type", issue = "102070")]
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`#[inline]
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``
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pub fn log2(self) -> u32 {
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pub const fn log2(self) -> u32 {
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`self.as_nonzero().trailing_zeros()
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`}
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/// Returns a bit mask that can be used to match this alignment.
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///
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/// This is equivalent to `!(self.as_usize() - 1)`.
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///
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/// # Examples
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///
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```` +
/// ```
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/// #![feature(ptr_alignment_type)]
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/// #![feature(ptr_mask)]
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/// use std::ptr::{Alignment, NonNull};
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///
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/// #[repr(align(1))] struct Align1(u8);
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/// #[repr(align(2))] struct Align2(u16);
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/// #[repr(align(4))] struct Align4(u32);
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/// let one = <NonNull>::dangling().as_ptr();
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/// let two = <NonNull>::dangling().as_ptr();
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/// let four = <NonNull>::dangling().as_ptr();
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///
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/// assert_eq!(four.mask(Alignment::of::().mask()), four);
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/// assert_eq!(four.mask(Alignment::of::().mask()), four);
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/// assert_eq!(four.mask(Alignment::of::().mask()), four);
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/// assert_ne!(one.mask(Alignment::of::().mask()), one);
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/// ```
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#[unstable(feature = "ptr_alignment_type", issue = "102070")]
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#[rustc_const_unstable(feature = "ptr_alignment_type", issue = "102070")]
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#[inline]
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pub const fn mask(self) -> usize {
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// SAFETY: The alignment is always nonzero, and therefore decrementing won't overflow.
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!(unsafe { self.as_usize().unchecked_sub(1) })
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}
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`}
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``
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`#[unstable(feature = "ptr_alignment_type", issue = "102070")]
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`@@ -193,6 +228,14 @@ impl hash::Hash for Alignment {
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`}
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`}
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/// Returns [Alignment::MIN], which is valid for any type.
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#[unstable(feature = "ptr_alignment_type", issue = "102070")]
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impl Default for Alignment {
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fn default() -> Alignment {
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Alignment::MIN
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}
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}
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`#[cfg(target_pointer_width = "16")]
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`type AlignmentEnum = AlignmentEnum16;
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`#[cfg(target_pointer_width = "32")]
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