core::ptr

Struct Alignment

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pub struct Alignment(/* private fields */);
๐Ÿ”ฌThis is a nightly-only experimental API. (ptr_alignment_type #102070)
Expand description

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.

Implementationsยง

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impl Alignment

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pub const MIN: Self = _

๐Ÿ”ฌThis is a nightly-only experimental API. (ptr_alignment_type #102070)

The smallest possible alignment, 1.

All addresses are always aligned at least this much.

ยงExamples
#![feature(ptr_alignment_type)]
use std::ptr::Alignment;

assert_eq!(Alignment::MIN.as_usize(), 1);
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pub const fn of<T>() -> Self

๐Ÿ”ฌThis is a nightly-only experimental API. (ptr_alignment_type #102070)

Returns the alignment for a type.

This provides the same numerical value as mem::align_of, but in an Alignment instead of a usize.

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pub const fn new(align: usize) -> Option<Self>

๐Ÿ”ฌThis is a nightly-only experimental API. (ptr_alignment_type #102070)

Creates an Alignment from a usize, or returns None if itโ€™s not a power of two.

Note that 0 is not a power of two, nor a valid alignment.

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pub const unsafe fn new_unchecked(align: usize) -> Self

๐Ÿ”ฌThis is a nightly-only experimental API. (ptr_alignment_type #102070)

Creates an Alignment from a power-of-two usize.

ยงSafety

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.

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pub const fn as_usize(self) -> usize

๐Ÿ”ฌThis is a nightly-only experimental API. (ptr_alignment_type #102070)

Returns the alignment as a usize.

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pub const fn as_nonzero(self) -> NonZero<usize>

๐Ÿ”ฌThis is a nightly-only experimental API. (ptr_alignment_type #102070)

Returns the alignment as a NonZero<usize>.

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pub const fn log2(self) -> u32

๐Ÿ”ฌThis is a nightly-only experimental API. (ptr_alignment_type #102070)

Returns the base-2 logarithm of the alignment.

This is always exact, as self represents a power of two.

ยงExamples
#![feature(ptr_alignment_type)]
use std::ptr::Alignment;

assert_eq!(Alignment::of::<u8>().log2(), 0);
assert_eq!(Alignment::new(1024).unwrap().log2(), 10);
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pub const fn mask(self) -> usize

๐Ÿ”ฌThis is a nightly-only experimental API. (ptr_alignment_type #102070)

Returns a bit mask that can be used to match this alignment.

This is equivalent to !(self.as_usize() - 1).

ยงExamples
#![feature(ptr_alignment_type)]
#![feature(ptr_mask)]
use std::ptr::{Alignment, NonNull};

#[repr(align(1))] struct Align1(u8);
#[repr(align(2))] struct Align2(u16);
#[repr(align(4))] struct Align4(u32);
let one = <NonNull<Align1>>::dangling().as_ptr();
let two = <NonNull<Align2>>::dangling().as_ptr();
let four = <NonNull<Align4>>::dangling().as_ptr();

assert_eq!(four.mask(Alignment::of::<Align1>().mask()), four);
assert_eq!(four.mask(Alignment::of::<Align2>().mask()), four);
assert_eq!(four.mask(Alignment::of::<Align4>().mask()), four);
assert_ne!(one.mask(Alignment::of::<Align4>().mask()), one);

Trait Implementationsยง

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impl Clone for Alignment

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fn clone(&self) -> Alignment

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for Alignment

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl Default for Alignment

Returns Alignment::MIN, which is valid for any type.

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fn default() -> Alignment

Returns the โ€œdefault valueโ€ for a type. Read more
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impl From<Alignment> for NonZero<usize>

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fn from(align: Alignment) -> NonZero<usize>

Converts to this type from the input type.
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impl From<Alignment> for usize

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fn from(align: Alignment) -> usize

Converts to this type from the input type.
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impl Hash for Alignment

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fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher. Read more
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fn hash_slice<H: Hasher>(data: &[Self], state: &mut H)
where Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl Ord for Alignment

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fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other. Read more
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fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more
1.21.0 ยท sourceยง

fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
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fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more
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impl PartialEq for Alignment

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fn eq(&self, other: &Alignment) -> bool

Tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl PartialOrd for Alignment

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fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more
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fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator. Read more
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fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator. Read more
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fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator. Read more
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fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
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impl TryFrom<NonZero<usize>> for Alignment

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type Error = TryFromIntError

The type returned in the event of a conversion error.
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fn try_from(align: NonZero<usize>) -> Result<Alignment, Self::Error>

Performs the conversion.
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impl TryFrom<usize> for Alignment

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type Error = TryFromIntError

The type returned in the event of a conversion error.
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fn try_from(align: usize) -> Result<Alignment, Self::Error>

Performs the conversion.
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impl Copy for Alignment

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impl Eq for Alignment

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impl StructuralPartialEq for Alignment

Auto Trait Implementationsยง

Blanket Implementationsยง

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dst: *mut T)

๐Ÿ”ฌThis is a nightly-only experimental API. (clone_to_uninit #126799)
Performs copy-assignment from self to dst. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.