Alignment in std::ptr - Rust
Description: A type storing a `usize` which is a power of two, and thus represents a possible alignment in the Rust abstract machine.

## Alignment

# Struct Alignment

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    pub struct Alignment(/* private fields */);

🔬This 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.

## Implementations§

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### impl Alignment

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#### pub const MIN: Alignment

🔬This is a nightly-only experimental API. (`ptr_alignment_type` #102070)

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);

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#### pub const fn of<T>() -> Alignment

🔬This is a nightly-only experimental API. (`ptr_alignment_type` #102070)

Returns the alignment for a type.

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

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

🔬This is a nightly-only experimental API. (`ptr_alignment_type` #102070)

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.

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

🔬This is a nightly-only experimental API. (`ptr_alignment_type` #102070)

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.

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#### pub const fn as_usize(self) -> usize

🔬This 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>

🔬This 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

🔬This 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.

##### §Examples

    #![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

🔬This 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)`.

##### §Examples

    #![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 Implementations§

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### impl Clone for Alignment

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#### fn clone(&self) -> Alignment

Returns a duplicate of the value. Read more
1.0.0 · Source§

#### 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<(), Error>

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 “default value” 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>(&self, state: &mut H)
where H: Hasher,

Feeds this value into the given `Hasher`. Read more
1.3.0 · Source§

#### fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, 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: &Alignment) -> Ordering

This method returns an `Ordering` between `self` and `other`. Read more
1.21.0 · Source§

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

Compares and returns the maximum of two values. Read more
1.21.0 · Source§

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

Compares and returns the minimum of two values. Read more
1.50.0 · Source§

#### fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized,

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 `==`.
1.0.0 · Source§

#### 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: &Alignment) -> Option<Ordering>

This method returns an ordering between `self` and `other` values if one exists. Read more
1.0.0 · Source§

#### fn lt(&self, other: &Rhs) -> bool

Tests less than (for `self` and `other`) and is used by the `<` operator. Read more
1.0.0 · Source§

#### fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more
1.0.0 · Source§

#### fn gt(&self, other: &Rhs) -> bool

Tests greater than (for `self` and `other`) and is used by the `>` operator. Read more
1.0.0 · Source§

#### 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, <Alignment as TryFrom<NonZero<usize>>>::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, <Alignment as TryFrom<usize>>::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 Implementations§

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### impl Freeze for Alignment

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### impl RefUnwindSafe for Alignment

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### impl Send for Alignment

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### impl Sync for Alignment

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### impl Unpin for Alignment

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### impl UnwindSafe for Alignment

## Blanket Implementations§

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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, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit` #126799)
Performs copy-assignment from `self` to `dest`. 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> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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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.