pub struct Alignment(/* private fields */);
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
sourceยงimpl Alignment
impl Alignment
sourcepub const MIN: Self = _
๐ฌThis is a nightly-only experimental API. (ptr_alignment_type
#102070)
pub const MIN: Self = _
ptr_alignment_type
#102070)sourcepub const fn of<T>() -> Self
๐ฌThis is a nightly-only experimental API. (ptr_alignment_type
#102070)
pub const fn of<T>() -> Self
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
.
sourcepub const fn new(align: usize) -> Option<Self>
๐ฌThis is a nightly-only experimental API. (ptr_alignment_type
#102070)
pub const fn new(align: usize) -> Option<Self>
ptr_alignment_type
#102070)Creates an Alignment
from a usize
, or returns None
if itโs
not a power of two.
Note that 0
is not a power of two, nor a valid alignment.
sourcepub const unsafe fn new_unchecked(align: usize) -> Self
๐ฌThis is a nightly-only experimental API. (ptr_alignment_type
#102070)
pub const unsafe fn new_unchecked(align: usize) -> Self
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.
sourcepub const fn as_usize(self) -> usize
๐ฌThis is a nightly-only experimental API. (ptr_alignment_type
#102070)
pub const fn as_usize(self) -> usize
ptr_alignment_type
#102070)Returns the alignment as a usize
.
sourcepub const fn as_nonzero(self) -> NonZero<usize>
๐ฌThis is a nightly-only experimental API. (ptr_alignment_type
#102070)
pub const fn as_nonzero(self) -> NonZero<usize>
ptr_alignment_type
#102070)sourcepub const fn log2(self) -> u32
๐ฌThis is a nightly-only experimental API. (ptr_alignment_type
#102070)
pub const fn log2(self) -> u32
ptr_alignment_type
#102070)Returns the base-2 logarithm of the alignment.
This is always exact, as self
represents a power of two.
ยงExamples
sourcepub const fn mask(self) -> usize
๐ฌThis is a nightly-only experimental API. (ptr_alignment_type
#102070)
pub const fn mask(self) -> usize
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
sourceยงimpl Default for Alignment
impl Default for Alignment
Returns Alignment::MIN
, which is valid for any type.