mirror of
https://github.com/rust-lang/rust.git
synced 2025-11-19 17:06:42 +00:00
1745 lines
69 KiB
Rust
1745 lines
69 KiB
Rust
use crate::cmp::Ordering;
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use crate::marker::{PointeeSized, Unsize};
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use crate::mem::{MaybeUninit, SizedTypeProperties};
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use crate::num::NonZero;
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use crate::ops::{CoerceUnsized, DispatchFromDyn};
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use crate::pin::PinCoerceUnsized;
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use crate::ptr::Unique;
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use crate::slice::{self, SliceIndex};
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use crate::ub_checks::assert_unsafe_precondition;
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use crate::{fmt, hash, intrinsics, mem, ptr};
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/// `*mut T` but non-zero and [covariant].
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///
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/// This is often the correct thing to use when building data structures using
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/// raw pointers, but is ultimately more dangerous to use because of its additional
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/// properties. If you're not sure if you should use `NonNull<T>`, just use `*mut T`!
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///
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/// Unlike `*mut T`, the pointer must always be non-null, even if the pointer
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/// is never dereferenced. This is so that enums may use this forbidden value
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/// as a discriminant -- `Option<NonNull<T>>` has the same size as `*mut T`.
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/// However the pointer may still dangle if it isn't dereferenced.
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///
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/// Unlike `*mut T`, `NonNull<T>` is covariant over `T`. This is usually the correct
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/// choice for most data structures and safe abstractions, such as `Box`, `Rc`, `Arc`, `Vec`,
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/// and `LinkedList`.
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///
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/// In rare cases, if your type exposes a way to mutate the value of `T` through a `NonNull<T>`,
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/// and you need to prevent unsoundness from variance (for example, if `T` could be a reference
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/// with a shorter lifetime), you should add a field to make your type invariant, such as
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/// `PhantomData<Cell<T>>` or `PhantomData<&'a mut T>`.
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///
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/// Example of a type that must be invariant:
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/// ```rust
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/// use std::cell::Cell;
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/// use std::marker::PhantomData;
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/// struct Invariant<T> {
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/// ptr: std::ptr::NonNull<T>,
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/// _invariant: PhantomData<Cell<T>>,
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/// }
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/// ```
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///
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/// Notice that `NonNull<T>` has a `From` instance for `&T`. However, this does
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/// not change the fact that mutating through a (pointer derived from a) shared
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/// reference is undefined behavior unless the mutation happens inside an
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/// [`UnsafeCell<T>`]. The same goes for creating a mutable reference from a shared
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/// reference. When using this `From` instance without an `UnsafeCell<T>`,
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/// it is your responsibility to ensure that `as_mut` is never called, and `as_ptr`
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/// is never used for mutation.
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///
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/// # Representation
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///
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/// Thanks to the [null pointer optimization],
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/// `NonNull<T>` and `Option<NonNull<T>>`
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/// are guaranteed to have the same size and alignment:
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///
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/// ```
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/// use std::ptr::NonNull;
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///
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/// assert_eq!(size_of::<NonNull<i16>>(), size_of::<Option<NonNull<i16>>>());
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/// assert_eq!(align_of::<NonNull<i16>>(), align_of::<Option<NonNull<i16>>>());
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///
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/// assert_eq!(size_of::<NonNull<str>>(), size_of::<Option<NonNull<str>>>());
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/// assert_eq!(align_of::<NonNull<str>>(), align_of::<Option<NonNull<str>>>());
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/// ```
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///
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/// [covariant]: https://doc.rust-lang.org/reference/subtyping.html
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/// [`PhantomData`]: crate::marker::PhantomData
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/// [`UnsafeCell<T>`]: crate::cell::UnsafeCell
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/// [null pointer optimization]: crate::option#representation
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#[stable(feature = "nonnull", since = "1.25.0")]
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#[repr(transparent)]
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#[rustc_layout_scalar_valid_range_start(1)]
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#[rustc_nonnull_optimization_guaranteed]
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#[rustc_diagnostic_item = "NonNull"]
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pub struct NonNull<T: PointeeSized> {
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// Remember to use `.as_ptr()` instead of `.pointer`, as field projecting to
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// this is banned by <https://github.com/rust-lang/compiler-team/issues/807>.
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pointer: *const T,
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}
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/// `NonNull` pointers are not `Send` because the data they reference may be aliased.
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// N.B., this impl is unnecessary, but should provide better error messages.
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#[stable(feature = "nonnull", since = "1.25.0")]
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impl<T: PointeeSized> !Send for NonNull<T> {}
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/// `NonNull` pointers are not `Sync` because the data they reference may be aliased.
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// N.B., this impl is unnecessary, but should provide better error messages.
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#[stable(feature = "nonnull", since = "1.25.0")]
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impl<T: PointeeSized> !Sync for NonNull<T> {}
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impl<T: Sized> NonNull<T> {
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/// Creates a pointer with the given address and no [provenance][crate::ptr#provenance].
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///
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/// For more details, see the equivalent method on a raw pointer, [`ptr::without_provenance_mut`].
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///
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/// This is a [Strict Provenance][crate::ptr#strict-provenance] API.
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#[stable(feature = "nonnull_provenance", since = "1.89.0")]
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#[rustc_const_stable(feature = "nonnull_provenance", since = "1.89.0")]
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#[must_use]
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#[inline]
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pub const fn without_provenance(addr: NonZero<usize>) -> Self {
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let pointer = crate::ptr::without_provenance(addr.get());
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// SAFETY: we know `addr` is non-zero.
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unsafe { NonNull { pointer } }
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}
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/// Creates a new `NonNull` that is dangling, but well-aligned.
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///
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/// This is useful for initializing types which lazily allocate, like
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/// `Vec::new` does.
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///
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/// Note that the address of the returned pointer may potentially
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/// be that of a valid pointer, which means this must not be used
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/// as a "not yet initialized" sentinel value.
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/// Types that lazily allocate must track initialization by some other means.
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///
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/// # Examples
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///
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/// ```
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/// use std::ptr::NonNull;
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///
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/// let ptr = NonNull::<u32>::dangling();
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/// // Important: don't try to access the value of `ptr` without
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/// // initializing it first! The pointer is not null but isn't valid either!
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/// ```
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#[stable(feature = "nonnull", since = "1.25.0")]
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#[rustc_const_stable(feature = "const_nonnull_dangling", since = "1.36.0")]
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#[must_use]
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#[inline]
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pub const fn dangling() -> Self {
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let align = crate::ptr::Alignment::of::<T>();
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NonNull::without_provenance(align.as_nonzero())
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}
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/// Converts an address back to a mutable pointer, picking up some previously 'exposed'
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/// [provenance][crate::ptr#provenance].
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///
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/// For more details, see the equivalent method on a raw pointer, [`ptr::with_exposed_provenance_mut`].
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///
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/// This is an [Exposed Provenance][crate::ptr#exposed-provenance] API.
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#[stable(feature = "nonnull_provenance", since = "1.89.0")]
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#[inline]
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pub fn with_exposed_provenance(addr: NonZero<usize>) -> Self {
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// SAFETY: we know `addr` is non-zero.
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unsafe {
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let ptr = crate::ptr::with_exposed_provenance_mut(addr.get());
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NonNull::new_unchecked(ptr)
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}
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}
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/// Returns a shared references to the value. In contrast to [`as_ref`], this does not require
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/// that the value has to be initialized.
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///
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/// For the mutable counterpart see [`as_uninit_mut`].
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///
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/// [`as_ref`]: NonNull::as_ref
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/// [`as_uninit_mut`]: NonNull::as_uninit_mut
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///
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/// # Safety
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///
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/// When calling this method, you have to ensure that
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/// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
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/// Note that because the created reference is to `MaybeUninit<T>`, the
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/// source pointer can point to uninitialized memory.
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#[inline]
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#[must_use]
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#[unstable(feature = "ptr_as_uninit", issue = "75402")]
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pub const unsafe fn as_uninit_ref<'a>(self) -> &'a MaybeUninit<T> {
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// SAFETY: the caller must guarantee that `self` meets all the
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// requirements for a reference.
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unsafe { &*self.cast().as_ptr() }
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}
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/// Returns a unique references to the value. In contrast to [`as_mut`], this does not require
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/// that the value has to be initialized.
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///
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/// For the shared counterpart see [`as_uninit_ref`].
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///
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/// [`as_mut`]: NonNull::as_mut
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/// [`as_uninit_ref`]: NonNull::as_uninit_ref
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///
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/// # Safety
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///
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/// When calling this method, you have to ensure that
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/// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
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/// Note that because the created reference is to `MaybeUninit<T>`, the
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/// source pointer can point to uninitialized memory.
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#[inline]
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#[must_use]
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#[unstable(feature = "ptr_as_uninit", issue = "75402")]
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pub const unsafe fn as_uninit_mut<'a>(self) -> &'a mut MaybeUninit<T> {
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// SAFETY: the caller must guarantee that `self` meets all the
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// requirements for a reference.
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unsafe { &mut *self.cast().as_ptr() }
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}
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/// Casts from a pointer-to-`T` to a pointer-to-`[T; N]`.
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#[inline]
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#[unstable(feature = "ptr_cast_array", issue = "144514")]
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pub const fn cast_array<const N: usize>(self) -> NonNull<[T; N]> {
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self.cast()
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}
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}
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impl<T: PointeeSized> NonNull<T> {
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/// Creates a new `NonNull`.
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///
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/// # Safety
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///
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/// `ptr` must be non-null.
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///
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/// # Examples
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///
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/// ```
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/// use std::ptr::NonNull;
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///
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/// let mut x = 0u32;
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/// let ptr = unsafe { NonNull::new_unchecked(&mut x as *mut _) };
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/// ```
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///
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/// *Incorrect* usage of this function:
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///
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/// ```rust,no_run
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/// use std::ptr::NonNull;
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///
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/// // NEVER DO THAT!!! This is undefined behavior. ⚠️
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/// let ptr = unsafe { NonNull::<u32>::new_unchecked(std::ptr::null_mut()) };
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/// ```
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#[stable(feature = "nonnull", since = "1.25.0")]
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#[rustc_const_stable(feature = "const_nonnull_new_unchecked", since = "1.25.0")]
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#[inline]
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#[track_caller]
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pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
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// SAFETY: the caller must guarantee that `ptr` is non-null.
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unsafe {
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assert_unsafe_precondition!(
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check_language_ub,
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"NonNull::new_unchecked requires that the pointer is non-null",
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(ptr: *mut () = ptr as *mut ()) => !ptr.is_null()
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);
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NonNull { pointer: ptr as _ }
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}
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}
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/// Creates a new `NonNull` if `ptr` is non-null.
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///
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/// # Panics during const evaluation
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///
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/// This method will panic during const evaluation if the pointer cannot be
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/// determined to be null or not. See [`is_null`] for more information.
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///
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/// [`is_null`]: ../primitive.pointer.html#method.is_null-1
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///
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/// # Examples
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///
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/// ```
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/// use std::ptr::NonNull;
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///
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/// let mut x = 0u32;
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/// let ptr = NonNull::<u32>::new(&mut x as *mut _).expect("ptr is null!");
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///
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/// if let Some(ptr) = NonNull::<u32>::new(std::ptr::null_mut()) {
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/// unreachable!();
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/// }
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/// ```
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#[stable(feature = "nonnull", since = "1.25.0")]
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#[rustc_const_stable(feature = "const_nonnull_new", since = "1.85.0")]
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#[inline]
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pub const fn new(ptr: *mut T) -> Option<Self> {
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if !ptr.is_null() {
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// SAFETY: The pointer is already checked and is not null
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Some(unsafe { Self::new_unchecked(ptr) })
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} else {
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None
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}
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}
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/// Converts a reference to a `NonNull` pointer.
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#[stable(feature = "non_null_from_ref", since = "1.89.0")]
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#[rustc_const_stable(feature = "non_null_from_ref", since = "1.89.0")]
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#[inline]
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pub const fn from_ref(r: &T) -> Self {
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// SAFETY: A reference cannot be null.
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unsafe { NonNull { pointer: r as *const T } }
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}
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/// Converts a mutable reference to a `NonNull` pointer.
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#[stable(feature = "non_null_from_ref", since = "1.89.0")]
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#[rustc_const_stable(feature = "non_null_from_ref", since = "1.89.0")]
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#[inline]
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pub const fn from_mut(r: &mut T) -> Self {
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// SAFETY: A mutable reference cannot be null.
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unsafe { NonNull { pointer: r as *mut T } }
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}
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/// Performs the same functionality as [`std::ptr::from_raw_parts`], except that a
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/// `NonNull` pointer is returned, as opposed to a raw `*const` pointer.
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///
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/// See the documentation of [`std::ptr::from_raw_parts`] for more details.
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///
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/// [`std::ptr::from_raw_parts`]: crate::ptr::from_raw_parts
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#[unstable(feature = "ptr_metadata", issue = "81513")]
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#[inline]
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pub const fn from_raw_parts(
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data_pointer: NonNull<impl super::Thin>,
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metadata: <T as super::Pointee>::Metadata,
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) -> NonNull<T> {
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// SAFETY: The result of `ptr::from::raw_parts_mut` is non-null because `data_pointer` is.
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unsafe {
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NonNull::new_unchecked(super::from_raw_parts_mut(data_pointer.as_ptr(), metadata))
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}
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}
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/// Decompose a (possibly wide) pointer into its data pointer and metadata components.
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///
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/// The pointer can be later reconstructed with [`NonNull::from_raw_parts`].
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#[unstable(feature = "ptr_metadata", issue = "81513")]
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#[must_use = "this returns the result of the operation, \
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without modifying the original"]
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#[inline]
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pub const fn to_raw_parts(self) -> (NonNull<()>, <T as super::Pointee>::Metadata) {
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(self.cast(), super::metadata(self.as_ptr()))
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}
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/// Gets the "address" portion of the pointer.
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///
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/// For more details, see the equivalent method on a raw pointer, [`pointer::addr`].
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///
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/// This is a [Strict Provenance][crate::ptr#strict-provenance] API.
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#[must_use]
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#[inline]
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#[stable(feature = "strict_provenance", since = "1.84.0")]
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pub fn addr(self) -> NonZero<usize> {
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// SAFETY: The pointer is guaranteed by the type to be non-null,
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// meaning that the address will be non-zero.
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unsafe { NonZero::new_unchecked(self.as_ptr().addr()) }
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}
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/// Exposes the ["provenance"][crate::ptr#provenance] part of the pointer for future use in
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/// [`with_exposed_provenance`][NonNull::with_exposed_provenance] and returns the "address" portion.
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///
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/// For more details, see the equivalent method on a raw pointer, [`pointer::expose_provenance`].
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///
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/// This is an [Exposed Provenance][crate::ptr#exposed-provenance] API.
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#[stable(feature = "nonnull_provenance", since = "1.89.0")]
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pub fn expose_provenance(self) -> NonZero<usize> {
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// SAFETY: The pointer is guaranteed by the type to be non-null,
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// meaning that the address will be non-zero.
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unsafe { NonZero::new_unchecked(self.as_ptr().expose_provenance()) }
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}
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/// Creates a new pointer with the given address and the [provenance][crate::ptr#provenance] of
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/// `self`.
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///
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/// For more details, see the equivalent method on a raw pointer, [`pointer::with_addr`].
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///
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/// This is a [Strict Provenance][crate::ptr#strict-provenance] API.
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#[must_use]
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#[inline]
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#[stable(feature = "strict_provenance", since = "1.84.0")]
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pub fn with_addr(self, addr: NonZero<usize>) -> Self {
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// SAFETY: The result of `ptr::from::with_addr` is non-null because `addr` is guaranteed to be non-zero.
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unsafe { NonNull::new_unchecked(self.as_ptr().with_addr(addr.get()) as *mut _) }
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}
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/// Creates a new pointer by mapping `self`'s address to a new one, preserving the
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/// [provenance][crate::ptr#provenance] of `self`.
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///
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/// For more details, see the equivalent method on a raw pointer, [`pointer::map_addr`].
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///
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/// This is a [Strict Provenance][crate::ptr#strict-provenance] API.
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#[must_use]
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#[inline]
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#[stable(feature = "strict_provenance", since = "1.84.0")]
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pub fn map_addr(self, f: impl FnOnce(NonZero<usize>) -> NonZero<usize>) -> Self {
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self.with_addr(f(self.addr()))
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}
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/// Acquires the underlying `*mut` pointer.
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///
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/// # Examples
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///
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/// ```
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/// use std::ptr::NonNull;
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///
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/// let mut x = 0u32;
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/// let ptr = NonNull::new(&mut x).expect("ptr is null!");
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///
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/// let x_value = unsafe { *ptr.as_ptr() };
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/// assert_eq!(x_value, 0);
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///
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/// unsafe { *ptr.as_ptr() += 2; }
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/// let x_value = unsafe { *ptr.as_ptr() };
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/// assert_eq!(x_value, 2);
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/// ```
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#[stable(feature = "nonnull", since = "1.25.0")]
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#[rustc_const_stable(feature = "const_nonnull_as_ptr", since = "1.32.0")]
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#[rustc_never_returns_null_ptr]
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#[must_use]
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#[inline(always)]
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pub const fn as_ptr(self) -> *mut T {
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// This is a transmute for the same reasons as `NonZero::get`.
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// SAFETY: `NonNull` is `transparent` over a `*const T`, and `*const T`
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// and `*mut T` have the same layout, so transitively we can transmute
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// our `NonNull` to a `*mut T` directly.
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unsafe { mem::transmute::<Self, *mut T>(self) }
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}
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|
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/// Returns a shared reference to the value. If the value may be uninitialized, [`as_uninit_ref`]
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/// must be used instead.
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///
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/// For the mutable counterpart see [`as_mut`].
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///
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/// [`as_uninit_ref`]: NonNull::as_uninit_ref
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/// [`as_mut`]: NonNull::as_mut
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///
|
|
/// # Safety
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|
///
|
|
/// When calling this method, you have to ensure that
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|
/// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
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|
///
|
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/// # Examples
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|
///
|
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/// ```
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/// use std::ptr::NonNull;
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///
|
|
/// let mut x = 0u32;
|
|
/// let ptr = NonNull::new(&mut x as *mut _).expect("ptr is null!");
|
|
///
|
|
/// let ref_x = unsafe { ptr.as_ref() };
|
|
/// println!("{ref_x}");
|
|
/// ```
|
|
///
|
|
/// [the module documentation]: crate::ptr#safety
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
#[rustc_const_stable(feature = "const_nonnull_as_ref", since = "1.73.0")]
|
|
#[must_use]
|
|
#[inline(always)]
|
|
pub const unsafe fn as_ref<'a>(&self) -> &'a T {
|
|
// SAFETY: the caller must guarantee that `self` meets all the
|
|
// requirements for a reference.
|
|
// `cast_const` avoids a mutable raw pointer deref.
|
|
unsafe { &*self.as_ptr().cast_const() }
|
|
}
|
|
|
|
/// Returns a unique reference to the value. If the value may be uninitialized, [`as_uninit_mut`]
|
|
/// must be used instead.
|
|
///
|
|
/// For the shared counterpart see [`as_ref`].
|
|
///
|
|
/// [`as_uninit_mut`]: NonNull::as_uninit_mut
|
|
/// [`as_ref`]: NonNull::as_ref
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// When calling this method, you have to ensure that
|
|
/// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let mut x = 0u32;
|
|
/// let mut ptr = NonNull::new(&mut x).expect("null pointer");
|
|
///
|
|
/// let x_ref = unsafe { ptr.as_mut() };
|
|
/// assert_eq!(*x_ref, 0);
|
|
/// *x_ref += 2;
|
|
/// assert_eq!(*x_ref, 2);
|
|
/// ```
|
|
///
|
|
/// [the module documentation]: crate::ptr#safety
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
#[rustc_const_stable(feature = "const_ptr_as_ref", since = "1.83.0")]
|
|
#[must_use]
|
|
#[inline(always)]
|
|
pub const unsafe fn as_mut<'a>(&mut self) -> &'a mut T {
|
|
// SAFETY: the caller must guarantee that `self` meets all the
|
|
// requirements for a mutable reference.
|
|
unsafe { &mut *self.as_ptr() }
|
|
}
|
|
|
|
/// Casts to a pointer of another type.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let mut x = 0u32;
|
|
/// let ptr = NonNull::new(&mut x as *mut _).expect("null pointer");
|
|
///
|
|
/// let casted_ptr = ptr.cast::<i8>();
|
|
/// let raw_ptr: *mut i8 = casted_ptr.as_ptr();
|
|
/// ```
|
|
#[stable(feature = "nonnull_cast", since = "1.27.0")]
|
|
#[rustc_const_stable(feature = "const_nonnull_cast", since = "1.36.0")]
|
|
#[must_use = "this returns the result of the operation, \
|
|
without modifying the original"]
|
|
#[inline]
|
|
pub const fn cast<U>(self) -> NonNull<U> {
|
|
// SAFETY: `self` is a `NonNull` pointer which is necessarily non-null
|
|
unsafe { NonNull { pointer: self.as_ptr() as *mut U } }
|
|
}
|
|
|
|
/// Try to cast to a pointer of another type by checking alignment.
|
|
///
|
|
/// If the pointer is properly aligned to the target type, it will be
|
|
/// cast to the target type. Otherwise, `None` is returned.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// #![feature(pointer_try_cast_aligned)]
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let mut x = 0u64;
|
|
///
|
|
/// let aligned = NonNull::from_mut(&mut x);
|
|
/// let unaligned = unsafe { aligned.byte_add(1) };
|
|
///
|
|
/// assert!(aligned.try_cast_aligned::<u32>().is_some());
|
|
/// assert!(unaligned.try_cast_aligned::<u32>().is_none());
|
|
/// ```
|
|
#[unstable(feature = "pointer_try_cast_aligned", issue = "141221")]
|
|
#[must_use = "this returns the result of the operation, \
|
|
without modifying the original"]
|
|
#[inline]
|
|
pub fn try_cast_aligned<U>(self) -> Option<NonNull<U>> {
|
|
if self.is_aligned_to(align_of::<U>()) { Some(self.cast()) } else { None }
|
|
}
|
|
|
|
/// Adds an offset to a pointer.
|
|
///
|
|
/// `count` is in units of T; e.g., a `count` of 3 represents a pointer
|
|
/// offset of `3 * size_of::<T>()` bytes.
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// If any of the following conditions are violated, the result is Undefined Behavior:
|
|
///
|
|
/// * The computed offset, `count * size_of::<T>()` bytes, must not overflow `isize`.
|
|
///
|
|
/// * If the computed offset is non-zero, then `self` must be derived from a pointer to some
|
|
/// [allocation], and the entire memory range between `self` and the result must be in
|
|
/// bounds of that allocation. In particular, this range must not "wrap around" the edge
|
|
/// of the address space.
|
|
///
|
|
/// Allocations can never be larger than `isize::MAX` bytes, so if the computed offset
|
|
/// stays in bounds of the allocation, it is guaranteed to satisfy the first requirement.
|
|
/// This implies, for instance, that `vec.as_ptr().add(vec.len())` (for `vec: Vec<T>`) is always
|
|
/// safe.
|
|
///
|
|
/// [allocation]: crate::ptr#allocation
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let mut s = [1, 2, 3];
|
|
/// let ptr: NonNull<u32> = NonNull::new(s.as_mut_ptr()).unwrap();
|
|
///
|
|
/// unsafe {
|
|
/// println!("{}", ptr.offset(1).read());
|
|
/// println!("{}", ptr.offset(2).read());
|
|
/// }
|
|
/// ```
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[must_use = "returns a new pointer rather than modifying its argument"]
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub const unsafe fn offset(self, count: isize) -> Self
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `offset`.
|
|
// Additionally safety contract of `offset` guarantees that the resulting pointer is
|
|
// pointing to an allocation, there can't be an allocation at null, thus it's safe to
|
|
// construct `NonNull`.
|
|
unsafe { NonNull { pointer: intrinsics::offset(self.as_ptr(), count) } }
|
|
}
|
|
|
|
/// Calculates the offset from a pointer in bytes.
|
|
///
|
|
/// `count` is in units of **bytes**.
|
|
///
|
|
/// This is purely a convenience for casting to a `u8` pointer and
|
|
/// using [offset][pointer::offset] on it. See that method for documentation
|
|
/// and safety requirements.
|
|
///
|
|
/// For non-`Sized` pointees this operation changes only the data pointer,
|
|
/// leaving the metadata untouched.
|
|
#[must_use]
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub const unsafe fn byte_offset(self, count: isize) -> Self {
|
|
// SAFETY: the caller must uphold the safety contract for `offset` and `byte_offset` has
|
|
// the same safety contract.
|
|
// Additionally safety contract of `offset` guarantees that the resulting pointer is
|
|
// pointing to an allocation, there can't be an allocation at null, thus it's safe to
|
|
// construct `NonNull`.
|
|
unsafe { NonNull { pointer: self.as_ptr().byte_offset(count) } }
|
|
}
|
|
|
|
/// Adds an offset to a pointer (convenience for `.offset(count as isize)`).
|
|
///
|
|
/// `count` is in units of T; e.g., a `count` of 3 represents a pointer
|
|
/// offset of `3 * size_of::<T>()` bytes.
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// If any of the following conditions are violated, the result is Undefined Behavior:
|
|
///
|
|
/// * The computed offset, `count * size_of::<T>()` bytes, must not overflow `isize`.
|
|
///
|
|
/// * If the computed offset is non-zero, then `self` must be derived from a pointer to some
|
|
/// [allocation], and the entire memory range between `self` and the result must be in
|
|
/// bounds of that allocation. In particular, this range must not "wrap around" the edge
|
|
/// of the address space.
|
|
///
|
|
/// Allocations can never be larger than `isize::MAX` bytes, so if the computed offset
|
|
/// stays in bounds of the allocation, it is guaranteed to satisfy the first requirement.
|
|
/// This implies, for instance, that `vec.as_ptr().add(vec.len())` (for `vec: Vec<T>`) is always
|
|
/// safe.
|
|
///
|
|
/// [allocation]: crate::ptr#allocation
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let s: &str = "123";
|
|
/// let ptr: NonNull<u8> = NonNull::new(s.as_ptr().cast_mut()).unwrap();
|
|
///
|
|
/// unsafe {
|
|
/// println!("{}", ptr.add(1).read() as char);
|
|
/// println!("{}", ptr.add(2).read() as char);
|
|
/// }
|
|
/// ```
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[must_use = "returns a new pointer rather than modifying its argument"]
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub const unsafe fn add(self, count: usize) -> Self
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `offset`.
|
|
// Additionally safety contract of `offset` guarantees that the resulting pointer is
|
|
// pointing to an allocation, there can't be an allocation at null, thus it's safe to
|
|
// construct `NonNull`.
|
|
unsafe { NonNull { pointer: intrinsics::offset(self.as_ptr(), count) } }
|
|
}
|
|
|
|
/// Calculates the offset from a pointer in bytes (convenience for `.byte_offset(count as isize)`).
|
|
///
|
|
/// `count` is in units of bytes.
|
|
///
|
|
/// This is purely a convenience for casting to a `u8` pointer and
|
|
/// using [`add`][NonNull::add] on it. See that method for documentation
|
|
/// and safety requirements.
|
|
///
|
|
/// For non-`Sized` pointees this operation changes only the data pointer,
|
|
/// leaving the metadata untouched.
|
|
#[must_use]
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub const unsafe fn byte_add(self, count: usize) -> Self {
|
|
// SAFETY: the caller must uphold the safety contract for `add` and `byte_add` has the same
|
|
// safety contract.
|
|
// Additionally safety contract of `add` guarantees that the resulting pointer is pointing
|
|
// to an allocation, there can't be an allocation at null, thus it's safe to construct
|
|
// `NonNull`.
|
|
unsafe { NonNull { pointer: self.as_ptr().byte_add(count) } }
|
|
}
|
|
|
|
/// Subtracts an offset from a pointer (convenience for
|
|
/// `.offset((count as isize).wrapping_neg())`).
|
|
///
|
|
/// `count` is in units of T; e.g., a `count` of 3 represents a pointer
|
|
/// offset of `3 * size_of::<T>()` bytes.
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// If any of the following conditions are violated, the result is Undefined Behavior:
|
|
///
|
|
/// * The computed offset, `count * size_of::<T>()` bytes, must not overflow `isize`.
|
|
///
|
|
/// * If the computed offset is non-zero, then `self` must be derived from a pointer to some
|
|
/// [allocation], and the entire memory range between `self` and the result must be in
|
|
/// bounds of that allocation. In particular, this range must not "wrap around" the edge
|
|
/// of the address space.
|
|
///
|
|
/// Allocations can never be larger than `isize::MAX` bytes, so if the computed offset
|
|
/// stays in bounds of the allocation, it is guaranteed to satisfy the first requirement.
|
|
/// This implies, for instance, that `vec.as_ptr().add(vec.len())` (for `vec: Vec<T>`) is always
|
|
/// safe.
|
|
///
|
|
/// [allocation]: crate::ptr#allocation
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let s: &str = "123";
|
|
///
|
|
/// unsafe {
|
|
/// let end: NonNull<u8> = NonNull::new(s.as_ptr().cast_mut()).unwrap().add(3);
|
|
/// println!("{}", end.sub(1).read() as char);
|
|
/// println!("{}", end.sub(2).read() as char);
|
|
/// }
|
|
/// ```
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[must_use = "returns a new pointer rather than modifying its argument"]
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub const unsafe fn sub(self, count: usize) -> Self
|
|
where
|
|
T: Sized,
|
|
{
|
|
if T::IS_ZST {
|
|
// Pointer arithmetic does nothing when the pointee is a ZST.
|
|
self
|
|
} else {
|
|
// SAFETY: the caller must uphold the safety contract for `offset`.
|
|
// Because the pointee is *not* a ZST, that means that `count` is
|
|
// at most `isize::MAX`, and thus the negation cannot overflow.
|
|
unsafe { self.offset((count as isize).unchecked_neg()) }
|
|
}
|
|
}
|
|
|
|
/// Calculates the offset from a pointer in bytes (convenience for
|
|
/// `.byte_offset((count as isize).wrapping_neg())`).
|
|
///
|
|
/// `count` is in units of bytes.
|
|
///
|
|
/// This is purely a convenience for casting to a `u8` pointer and
|
|
/// using [`sub`][NonNull::sub] on it. See that method for documentation
|
|
/// and safety requirements.
|
|
///
|
|
/// For non-`Sized` pointees this operation changes only the data pointer,
|
|
/// leaving the metadata untouched.
|
|
#[must_use]
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub const unsafe fn byte_sub(self, count: usize) -> Self {
|
|
// SAFETY: the caller must uphold the safety contract for `sub` and `byte_sub` has the same
|
|
// safety contract.
|
|
// Additionally safety contract of `sub` guarantees that the resulting pointer is pointing
|
|
// to an allocation, there can't be an allocation at null, thus it's safe to construct
|
|
// `NonNull`.
|
|
unsafe { NonNull { pointer: self.as_ptr().byte_sub(count) } }
|
|
}
|
|
|
|
/// Calculates the distance between two pointers within the same allocation. The returned value is in
|
|
/// units of T: the distance in bytes divided by `size_of::<T>()`.
|
|
///
|
|
/// This is equivalent to `(self as isize - origin as isize) / (size_of::<T>() as isize)`,
|
|
/// except that it has a lot more opportunities for UB, in exchange for the compiler
|
|
/// better understanding what you are doing.
|
|
///
|
|
/// The primary motivation of this method is for computing the `len` of an array/slice
|
|
/// of `T` that you are currently representing as a "start" and "end" pointer
|
|
/// (and "end" is "one past the end" of the array).
|
|
/// In that case, `end.offset_from(start)` gets you the length of the array.
|
|
///
|
|
/// All of the following safety requirements are trivially satisfied for this usecase.
|
|
///
|
|
/// [`offset`]: #method.offset
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// If any of the following conditions are violated, the result is Undefined Behavior:
|
|
///
|
|
/// * `self` and `origin` must either
|
|
///
|
|
/// * point to the same address, or
|
|
/// * both be *derived from* a pointer to the same [allocation], and the memory range between
|
|
/// the two pointers must be in bounds of that object. (See below for an example.)
|
|
///
|
|
/// * The distance between the pointers, in bytes, must be an exact multiple
|
|
/// of the size of `T`.
|
|
///
|
|
/// As a consequence, the absolute distance between the pointers, in bytes, computed on
|
|
/// mathematical integers (without "wrapping around"), cannot overflow an `isize`. This is
|
|
/// implied by the in-bounds requirement, and the fact that no allocation can be larger
|
|
/// than `isize::MAX` bytes.
|
|
///
|
|
/// The requirement for pointers to be derived from the same allocation is primarily
|
|
/// needed for `const`-compatibility: the distance between pointers into *different* allocated
|
|
/// objects is not known at compile-time. However, the requirement also exists at
|
|
/// runtime and may be exploited by optimizations. If you wish to compute the difference between
|
|
/// pointers that are not guaranteed to be from the same allocation, use `(self as isize -
|
|
/// origin as isize) / size_of::<T>()`.
|
|
// FIXME: recommend `addr()` instead of `as usize` once that is stable.
|
|
///
|
|
/// [`add`]: #method.add
|
|
/// [allocation]: crate::ptr#allocation
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// This function panics if `T` is a Zero-Sized Type ("ZST").
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let a = [0; 5];
|
|
/// let ptr1: NonNull<u32> = NonNull::from(&a[1]);
|
|
/// let ptr2: NonNull<u32> = NonNull::from(&a[3]);
|
|
/// unsafe {
|
|
/// assert_eq!(ptr2.offset_from(ptr1), 2);
|
|
/// assert_eq!(ptr1.offset_from(ptr2), -2);
|
|
/// assert_eq!(ptr1.offset(2), ptr2);
|
|
/// assert_eq!(ptr2.offset(-2), ptr1);
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// *Incorrect* usage:
|
|
///
|
|
/// ```rust,no_run
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let ptr1 = NonNull::new(Box::into_raw(Box::new(0u8))).unwrap();
|
|
/// let ptr2 = NonNull::new(Box::into_raw(Box::new(1u8))).unwrap();
|
|
/// let diff = (ptr2.addr().get() as isize).wrapping_sub(ptr1.addr().get() as isize);
|
|
/// // Make ptr2_other an "alias" of ptr2.add(1), but derived from ptr1.
|
|
/// let diff_plus_1 = diff.wrapping_add(1);
|
|
/// let ptr2_other = NonNull::new(ptr1.as_ptr().wrapping_byte_offset(diff_plus_1)).unwrap();
|
|
/// assert_eq!(ptr2.addr(), ptr2_other.addr());
|
|
/// // Since ptr2_other and ptr2 are derived from pointers to different objects,
|
|
/// // computing their offset is undefined behavior, even though
|
|
/// // they point to addresses that are in-bounds of the same object!
|
|
///
|
|
/// let one = unsafe { ptr2_other.offset_from(ptr2) }; // Undefined Behavior! ⚠️
|
|
/// ```
|
|
#[inline]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub const unsafe fn offset_from(self, origin: NonNull<T>) -> isize
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `offset_from`.
|
|
unsafe { self.as_ptr().offset_from(origin.as_ptr()) }
|
|
}
|
|
|
|
/// Calculates the distance between two pointers within the same allocation. The returned value is in
|
|
/// units of **bytes**.
|
|
///
|
|
/// This is purely a convenience for casting to a `u8` pointer and
|
|
/// using [`offset_from`][NonNull::offset_from] on it. See that method for
|
|
/// documentation and safety requirements.
|
|
///
|
|
/// For non-`Sized` pointees this operation considers only the data pointers,
|
|
/// ignoring the metadata.
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub const unsafe fn byte_offset_from<U: ?Sized>(self, origin: NonNull<U>) -> isize {
|
|
// SAFETY: the caller must uphold the safety contract for `byte_offset_from`.
|
|
unsafe { self.as_ptr().byte_offset_from(origin.as_ptr()) }
|
|
}
|
|
|
|
// N.B. `wrapping_offset``, `wrapping_add`, etc are not implemented because they can wrap to null
|
|
|
|
/// Calculates the distance between two pointers within the same allocation, *where it's known that
|
|
/// `self` is equal to or greater than `origin`*. The returned value is in
|
|
/// units of T: the distance in bytes is divided by `size_of::<T>()`.
|
|
///
|
|
/// This computes the same value that [`offset_from`](#method.offset_from)
|
|
/// would compute, but with the added precondition that the offset is
|
|
/// guaranteed to be non-negative. This method is equivalent to
|
|
/// `usize::try_from(self.offset_from(origin)).unwrap_unchecked()`,
|
|
/// but it provides slightly more information to the optimizer, which can
|
|
/// sometimes allow it to optimize slightly better with some backends.
|
|
///
|
|
/// This method can be though of as recovering the `count` that was passed
|
|
/// to [`add`](#method.add) (or, with the parameters in the other order,
|
|
/// to [`sub`](#method.sub)). The following are all equivalent, assuming
|
|
/// that their safety preconditions are met:
|
|
/// ```rust
|
|
/// # unsafe fn blah(ptr: std::ptr::NonNull<u32>, origin: std::ptr::NonNull<u32>, count: usize) -> bool { unsafe {
|
|
/// ptr.offset_from_unsigned(origin) == count
|
|
/// # &&
|
|
/// origin.add(count) == ptr
|
|
/// # &&
|
|
/// ptr.sub(count) == origin
|
|
/// # } }
|
|
/// ```
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// - The distance between the pointers must be non-negative (`self >= origin`)
|
|
///
|
|
/// - *All* the safety conditions of [`offset_from`](#method.offset_from)
|
|
/// apply to this method as well; see it for the full details.
|
|
///
|
|
/// Importantly, despite the return type of this method being able to represent
|
|
/// a larger offset, it's still *not permitted* to pass pointers which differ
|
|
/// by more than `isize::MAX` *bytes*. As such, the result of this method will
|
|
/// always be less than or equal to `isize::MAX as usize`.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// This function panics if `T` is a Zero-Sized Type ("ZST").
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let a = [0; 5];
|
|
/// let ptr1: NonNull<u32> = NonNull::from(&a[1]);
|
|
/// let ptr2: NonNull<u32> = NonNull::from(&a[3]);
|
|
/// unsafe {
|
|
/// assert_eq!(ptr2.offset_from_unsigned(ptr1), 2);
|
|
/// assert_eq!(ptr1.add(2), ptr2);
|
|
/// assert_eq!(ptr2.sub(2), ptr1);
|
|
/// assert_eq!(ptr2.offset_from_unsigned(ptr2), 0);
|
|
/// }
|
|
///
|
|
/// // This would be incorrect, as the pointers are not correctly ordered:
|
|
/// // ptr1.offset_from_unsigned(ptr2)
|
|
/// ```
|
|
#[inline]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "ptr_sub_ptr", since = "1.87.0")]
|
|
#[rustc_const_stable(feature = "const_ptr_sub_ptr", since = "1.87.0")]
|
|
pub const unsafe fn offset_from_unsigned(self, subtracted: NonNull<T>) -> usize
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `offset_from_unsigned`.
|
|
unsafe { self.as_ptr().offset_from_unsigned(subtracted.as_ptr()) }
|
|
}
|
|
|
|
/// Calculates the distance between two pointers within the same allocation, *where it's known that
|
|
/// `self` is equal to or greater than `origin`*. The returned value is in
|
|
/// units of **bytes**.
|
|
///
|
|
/// This is purely a convenience for casting to a `u8` pointer and
|
|
/// using [`offset_from_unsigned`][NonNull::offset_from_unsigned] on it.
|
|
/// See that method for documentation and safety requirements.
|
|
///
|
|
/// For non-`Sized` pointees this operation considers only the data pointers,
|
|
/// ignoring the metadata.
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "ptr_sub_ptr", since = "1.87.0")]
|
|
#[rustc_const_stable(feature = "const_ptr_sub_ptr", since = "1.87.0")]
|
|
pub const unsafe fn byte_offset_from_unsigned<U: ?Sized>(self, origin: NonNull<U>) -> usize {
|
|
// SAFETY: the caller must uphold the safety contract for `byte_offset_from_unsigned`.
|
|
unsafe { self.as_ptr().byte_offset_from_unsigned(origin.as_ptr()) }
|
|
}
|
|
|
|
/// Reads the value from `self` without moving it. This leaves the
|
|
/// memory in `self` unchanged.
|
|
///
|
|
/// See [`ptr::read`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::read`]: crate::ptr::read()
|
|
#[inline]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub const unsafe fn read(self) -> T
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `read`.
|
|
unsafe { ptr::read(self.as_ptr()) }
|
|
}
|
|
|
|
/// Performs a volatile read of the value from `self` without moving it. This
|
|
/// leaves the memory in `self` unchanged.
|
|
///
|
|
/// Volatile operations are intended to act on I/O memory, and are guaranteed
|
|
/// to not be elided or reordered by the compiler across other volatile
|
|
/// operations.
|
|
///
|
|
/// See [`ptr::read_volatile`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::read_volatile`]: crate::ptr::read_volatile()
|
|
#[inline]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub unsafe fn read_volatile(self) -> T
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `read_volatile`.
|
|
unsafe { ptr::read_volatile(self.as_ptr()) }
|
|
}
|
|
|
|
/// Reads the value from `self` without moving it. This leaves the
|
|
/// memory in `self` unchanged.
|
|
///
|
|
/// Unlike `read`, the pointer may be unaligned.
|
|
///
|
|
/// See [`ptr::read_unaligned`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::read_unaligned`]: crate::ptr::read_unaligned()
|
|
#[inline]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub const unsafe fn read_unaligned(self) -> T
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `read_unaligned`.
|
|
unsafe { ptr::read_unaligned(self.as_ptr()) }
|
|
}
|
|
|
|
/// Copies `count * size_of::<T>()` bytes from `self` to `dest`. The source
|
|
/// and destination may overlap.
|
|
///
|
|
/// NOTE: this has the *same* argument order as [`ptr::copy`].
|
|
///
|
|
/// See [`ptr::copy`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::copy`]: crate::ptr::copy()
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.83.0")]
|
|
pub const unsafe fn copy_to(self, dest: NonNull<T>, count: usize)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `copy`.
|
|
unsafe { ptr::copy(self.as_ptr(), dest.as_ptr(), count) }
|
|
}
|
|
|
|
/// Copies `count * size_of::<T>()` bytes from `self` to `dest`. The source
|
|
/// and destination may *not* overlap.
|
|
///
|
|
/// NOTE: this has the *same* argument order as [`ptr::copy_nonoverlapping`].
|
|
///
|
|
/// See [`ptr::copy_nonoverlapping`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::copy_nonoverlapping`]: crate::ptr::copy_nonoverlapping()
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.83.0")]
|
|
pub const unsafe fn copy_to_nonoverlapping(self, dest: NonNull<T>, count: usize)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `copy_nonoverlapping`.
|
|
unsafe { ptr::copy_nonoverlapping(self.as_ptr(), dest.as_ptr(), count) }
|
|
}
|
|
|
|
/// Copies `count * size_of::<T>()` bytes from `src` to `self`. The source
|
|
/// and destination may overlap.
|
|
///
|
|
/// NOTE: this has the *opposite* argument order of [`ptr::copy`].
|
|
///
|
|
/// See [`ptr::copy`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::copy`]: crate::ptr::copy()
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.83.0")]
|
|
pub const unsafe fn copy_from(self, src: NonNull<T>, count: usize)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `copy`.
|
|
unsafe { ptr::copy(src.as_ptr(), self.as_ptr(), count) }
|
|
}
|
|
|
|
/// Copies `count * size_of::<T>()` bytes from `src` to `self`. The source
|
|
/// and destination may *not* overlap.
|
|
///
|
|
/// NOTE: this has the *opposite* argument order of [`ptr::copy_nonoverlapping`].
|
|
///
|
|
/// See [`ptr::copy_nonoverlapping`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::copy_nonoverlapping`]: crate::ptr::copy_nonoverlapping()
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.83.0")]
|
|
pub const unsafe fn copy_from_nonoverlapping(self, src: NonNull<T>, count: usize)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `copy_nonoverlapping`.
|
|
unsafe { ptr::copy_nonoverlapping(src.as_ptr(), self.as_ptr(), count) }
|
|
}
|
|
|
|
/// Executes the destructor (if any) of the pointed-to value.
|
|
///
|
|
/// See [`ptr::drop_in_place`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::drop_in_place`]: crate::ptr::drop_in_place()
|
|
#[inline(always)]
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub unsafe fn drop_in_place(self) {
|
|
// SAFETY: the caller must uphold the safety contract for `drop_in_place`.
|
|
unsafe { ptr::drop_in_place(self.as_ptr()) }
|
|
}
|
|
|
|
/// Overwrites a memory location with the given value without reading or
|
|
/// dropping the old value.
|
|
///
|
|
/// See [`ptr::write`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::write`]: crate::ptr::write()
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "const_ptr_write", since = "1.83.0")]
|
|
pub const unsafe fn write(self, val: T)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `write`.
|
|
unsafe { ptr::write(self.as_ptr(), val) }
|
|
}
|
|
|
|
/// Invokes memset on the specified pointer, setting `count * size_of::<T>()`
|
|
/// bytes of memory starting at `self` to `val`.
|
|
///
|
|
/// See [`ptr::write_bytes`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::write_bytes`]: crate::ptr::write_bytes()
|
|
#[inline(always)]
|
|
#[doc(alias = "memset")]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "const_ptr_write", since = "1.83.0")]
|
|
pub const unsafe fn write_bytes(self, val: u8, count: usize)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `write_bytes`.
|
|
unsafe { ptr::write_bytes(self.as_ptr(), val, count) }
|
|
}
|
|
|
|
/// Performs a volatile write of a memory location with the given value without
|
|
/// reading or dropping the old value.
|
|
///
|
|
/// Volatile operations are intended to act on I/O memory, and are guaranteed
|
|
/// to not be elided or reordered by the compiler across other volatile
|
|
/// operations.
|
|
///
|
|
/// See [`ptr::write_volatile`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::write_volatile`]: crate::ptr::write_volatile()
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub unsafe fn write_volatile(self, val: T)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `write_volatile`.
|
|
unsafe { ptr::write_volatile(self.as_ptr(), val) }
|
|
}
|
|
|
|
/// Overwrites a memory location with the given value without reading or
|
|
/// dropping the old value.
|
|
///
|
|
/// Unlike `write`, the pointer may be unaligned.
|
|
///
|
|
/// See [`ptr::write_unaligned`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::write_unaligned`]: crate::ptr::write_unaligned()
|
|
#[inline(always)]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "const_ptr_write", since = "1.83.0")]
|
|
pub const unsafe fn write_unaligned(self, val: T)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `write_unaligned`.
|
|
unsafe { ptr::write_unaligned(self.as_ptr(), val) }
|
|
}
|
|
|
|
/// Replaces the value at `self` with `src`, returning the old
|
|
/// value, without dropping either.
|
|
///
|
|
/// See [`ptr::replace`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::replace`]: crate::ptr::replace()
|
|
#[inline(always)]
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "const_inherent_ptr_replace", since = "1.88.0")]
|
|
pub const unsafe fn replace(self, src: T) -> T
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `replace`.
|
|
unsafe { ptr::replace(self.as_ptr(), src) }
|
|
}
|
|
|
|
/// Swaps the values at two mutable locations of the same type, without
|
|
/// deinitializing either. They may overlap, unlike `mem::swap` which is
|
|
/// otherwise equivalent.
|
|
///
|
|
/// See [`ptr::swap`] for safety concerns and examples.
|
|
///
|
|
/// [`ptr::swap`]: crate::ptr::swap()
|
|
#[inline(always)]
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
#[rustc_const_stable(feature = "const_swap", since = "1.85.0")]
|
|
pub const unsafe fn swap(self, with: NonNull<T>)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `swap`.
|
|
unsafe { ptr::swap(self.as_ptr(), with.as_ptr()) }
|
|
}
|
|
|
|
/// Computes the offset that needs to be applied to the pointer in order to make it aligned to
|
|
/// `align`.
|
|
///
|
|
/// If it is not possible to align the pointer, the implementation returns
|
|
/// `usize::MAX`.
|
|
///
|
|
/// The offset is expressed in number of `T` elements, and not bytes.
|
|
///
|
|
/// There are no guarantees whatsoever that offsetting the pointer will not overflow or go
|
|
/// beyond the allocation that the pointer points into. It is up to the caller to ensure that
|
|
/// the returned offset is correct in all terms other than alignment.
|
|
///
|
|
/// When this is called during compile-time evaluation (which is unstable), the implementation
|
|
/// may return `usize::MAX` in cases where that can never happen at runtime. This is because the
|
|
/// actual alignment of pointers is not known yet during compile-time, so an offset with
|
|
/// guaranteed alignment can sometimes not be computed. For example, a buffer declared as `[u8;
|
|
/// N]` might be allocated at an odd or an even address, but at compile-time this is not yet
|
|
/// known, so the execution has to be correct for either choice. It is therefore impossible to
|
|
/// find an offset that is guaranteed to be 2-aligned. (This behavior is subject to change, as usual
|
|
/// for unstable APIs.)
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// The function panics if `align` is not a power-of-two.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Accessing adjacent `u8` as `u16`
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// # unsafe {
|
|
/// let x = [5_u8, 6, 7, 8, 9];
|
|
/// let ptr = NonNull::new(x.as_ptr() as *mut u8).unwrap();
|
|
/// let offset = ptr.align_offset(align_of::<u16>());
|
|
///
|
|
/// if offset < x.len() - 1 {
|
|
/// let u16_ptr = ptr.add(offset).cast::<u16>();
|
|
/// assert!(u16_ptr.read() == u16::from_ne_bytes([5, 6]) || u16_ptr.read() == u16::from_ne_bytes([6, 7]));
|
|
/// } else {
|
|
/// // while the pointer can be aligned via `offset`, it would point
|
|
/// // outside the allocation
|
|
/// }
|
|
/// # }
|
|
/// ```
|
|
#[inline]
|
|
#[must_use]
|
|
#[stable(feature = "non_null_convenience", since = "1.80.0")]
|
|
pub fn align_offset(self, align: usize) -> usize
|
|
where
|
|
T: Sized,
|
|
{
|
|
if !align.is_power_of_two() {
|
|
panic!("align_offset: align is not a power-of-two");
|
|
}
|
|
|
|
{
|
|
// SAFETY: `align` has been checked to be a power of 2 above.
|
|
unsafe { ptr::align_offset(self.as_ptr(), align) }
|
|
}
|
|
}
|
|
|
|
/// Returns whether the pointer is properly aligned for `T`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// // On some platforms, the alignment of i32 is less than 4.
|
|
/// #[repr(align(4))]
|
|
/// struct AlignedI32(i32);
|
|
///
|
|
/// let data = AlignedI32(42);
|
|
/// let ptr = NonNull::<AlignedI32>::from(&data);
|
|
///
|
|
/// assert!(ptr.is_aligned());
|
|
/// assert!(!NonNull::new(ptr.as_ptr().wrapping_byte_add(1)).unwrap().is_aligned());
|
|
/// ```
|
|
#[inline]
|
|
#[must_use]
|
|
#[stable(feature = "pointer_is_aligned", since = "1.79.0")]
|
|
pub fn is_aligned(self) -> bool
|
|
where
|
|
T: Sized,
|
|
{
|
|
self.as_ptr().is_aligned()
|
|
}
|
|
|
|
/// Returns whether the pointer is aligned to `align`.
|
|
///
|
|
/// For non-`Sized` pointees this operation considers only the data pointer,
|
|
/// ignoring the metadata.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// The function panics if `align` is not a power-of-two (this includes 0).
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(pointer_is_aligned_to)]
|
|
///
|
|
/// // On some platforms, the alignment of i32 is less than 4.
|
|
/// #[repr(align(4))]
|
|
/// struct AlignedI32(i32);
|
|
///
|
|
/// let data = AlignedI32(42);
|
|
/// let ptr = &data as *const AlignedI32;
|
|
///
|
|
/// assert!(ptr.is_aligned_to(1));
|
|
/// assert!(ptr.is_aligned_to(2));
|
|
/// assert!(ptr.is_aligned_to(4));
|
|
///
|
|
/// assert!(ptr.wrapping_byte_add(2).is_aligned_to(2));
|
|
/// assert!(!ptr.wrapping_byte_add(2).is_aligned_to(4));
|
|
///
|
|
/// assert_ne!(ptr.is_aligned_to(8), ptr.wrapping_add(1).is_aligned_to(8));
|
|
/// ```
|
|
#[inline]
|
|
#[must_use]
|
|
#[unstable(feature = "pointer_is_aligned_to", issue = "96284")]
|
|
pub fn is_aligned_to(self, align: usize) -> bool {
|
|
self.as_ptr().is_aligned_to(align)
|
|
}
|
|
}
|
|
|
|
impl<T> NonNull<T> {
|
|
/// Casts from a type to its maybe-uninitialized version.
|
|
#[must_use]
|
|
#[inline(always)]
|
|
#[unstable(feature = "cast_maybe_uninit", issue = "145036")]
|
|
pub const fn cast_uninit(self) -> NonNull<MaybeUninit<T>> {
|
|
self.cast()
|
|
}
|
|
}
|
|
impl<T> NonNull<MaybeUninit<T>> {
|
|
/// Casts from a maybe-uninitialized type to its initialized version.
|
|
///
|
|
/// This is always safe, since UB can only occur if the pointer is read
|
|
/// before being initialized.
|
|
#[must_use]
|
|
#[inline(always)]
|
|
#[unstable(feature = "cast_maybe_uninit", issue = "145036")]
|
|
pub const fn cast_init(self) -> NonNull<T> {
|
|
self.cast()
|
|
}
|
|
}
|
|
|
|
impl<T> NonNull<[T]> {
|
|
/// Creates a non-null raw slice from a thin pointer and a length.
|
|
///
|
|
/// The `len` argument is the number of **elements**, not the number of bytes.
|
|
///
|
|
/// This function is safe, but dereferencing the return value is unsafe.
|
|
/// See the documentation of [`slice::from_raw_parts`] for slice safety requirements.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// // create a slice pointer when starting out with a pointer to the first element
|
|
/// let mut x = [5, 6, 7];
|
|
/// let nonnull_pointer = NonNull::new(x.as_mut_ptr()).unwrap();
|
|
/// let slice = NonNull::slice_from_raw_parts(nonnull_pointer, 3);
|
|
/// assert_eq!(unsafe { slice.as_ref()[2] }, 7);
|
|
/// ```
|
|
///
|
|
/// (Note that this example artificially demonstrates a use of this method,
|
|
/// but `let slice = NonNull::from(&x[..]);` would be a better way to write code like this.)
|
|
#[stable(feature = "nonnull_slice_from_raw_parts", since = "1.70.0")]
|
|
#[rustc_const_stable(feature = "const_slice_from_raw_parts_mut", since = "1.83.0")]
|
|
#[must_use]
|
|
#[inline]
|
|
pub const fn slice_from_raw_parts(data: NonNull<T>, len: usize) -> Self {
|
|
// SAFETY: `data` is a `NonNull` pointer which is necessarily non-null
|
|
unsafe { Self::new_unchecked(super::slice_from_raw_parts_mut(data.as_ptr(), len)) }
|
|
}
|
|
|
|
/// Returns the length of a non-null raw slice.
|
|
///
|
|
/// The returned value is the number of **elements**, not the number of bytes.
|
|
///
|
|
/// This function is safe, even when the non-null raw slice cannot be dereferenced to a slice
|
|
/// because the pointer does not have a valid address.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
|
|
/// assert_eq!(slice.len(), 3);
|
|
/// ```
|
|
#[stable(feature = "slice_ptr_len_nonnull", since = "1.63.0")]
|
|
#[rustc_const_stable(feature = "const_slice_ptr_len_nonnull", since = "1.63.0")]
|
|
#[must_use]
|
|
#[inline]
|
|
pub const fn len(self) -> usize {
|
|
self.as_ptr().len()
|
|
}
|
|
|
|
/// Returns `true` if the non-null raw slice has a length of 0.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
|
|
/// assert!(!slice.is_empty());
|
|
/// ```
|
|
#[stable(feature = "slice_ptr_is_empty_nonnull", since = "1.79.0")]
|
|
#[rustc_const_stable(feature = "const_slice_ptr_is_empty_nonnull", since = "1.79.0")]
|
|
#[must_use]
|
|
#[inline]
|
|
pub const fn is_empty(self) -> bool {
|
|
self.len() == 0
|
|
}
|
|
|
|
/// Returns a non-null pointer to the slice's buffer.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// #![feature(slice_ptr_get)]
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
|
|
/// assert_eq!(slice.as_non_null_ptr(), NonNull::<i8>::dangling());
|
|
/// ```
|
|
#[inline]
|
|
#[must_use]
|
|
#[unstable(feature = "slice_ptr_get", issue = "74265")]
|
|
pub const fn as_non_null_ptr(self) -> NonNull<T> {
|
|
self.cast()
|
|
}
|
|
|
|
/// Returns a raw pointer to the slice's buffer.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// #![feature(slice_ptr_get)]
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
|
|
/// assert_eq!(slice.as_mut_ptr(), NonNull::<i8>::dangling().as_ptr());
|
|
/// ```
|
|
#[inline]
|
|
#[must_use]
|
|
#[unstable(feature = "slice_ptr_get", issue = "74265")]
|
|
#[rustc_never_returns_null_ptr]
|
|
pub const fn as_mut_ptr(self) -> *mut T {
|
|
self.as_non_null_ptr().as_ptr()
|
|
}
|
|
|
|
/// Returns a shared reference to a slice of possibly uninitialized values. In contrast to
|
|
/// [`as_ref`], this does not require that the value has to be initialized.
|
|
///
|
|
/// For the mutable counterpart see [`as_uninit_slice_mut`].
|
|
///
|
|
/// [`as_ref`]: NonNull::as_ref
|
|
/// [`as_uninit_slice_mut`]: NonNull::as_uninit_slice_mut
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// When calling this method, you have to ensure that all of the following is true:
|
|
///
|
|
/// * The pointer must be [valid] for reads for `ptr.len() * size_of::<T>()` many bytes,
|
|
/// and it must be properly aligned. This means in particular:
|
|
///
|
|
/// * The entire memory range of this slice must be contained within a single allocation!
|
|
/// Slices can never span across multiple allocations.
|
|
///
|
|
/// * The pointer must be aligned even for zero-length slices. One
|
|
/// reason for this is that enum layout optimizations may rely on references
|
|
/// (including slices of any length) being aligned and non-null to distinguish
|
|
/// them from other data. You can obtain a pointer that is usable as `data`
|
|
/// for zero-length slices using [`NonNull::dangling()`].
|
|
///
|
|
/// * The total size `ptr.len() * size_of::<T>()` of the slice must be no larger than `isize::MAX`.
|
|
/// See the safety documentation of [`pointer::offset`].
|
|
///
|
|
/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
|
|
/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
|
|
/// In particular, while this reference exists, the memory the pointer points to must
|
|
/// not get mutated (except inside `UnsafeCell`).
|
|
///
|
|
/// This applies even if the result of this method is unused!
|
|
///
|
|
/// See also [`slice::from_raw_parts`].
|
|
///
|
|
/// [valid]: crate::ptr#safety
|
|
#[inline]
|
|
#[must_use]
|
|
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
|
|
pub const unsafe fn as_uninit_slice<'a>(self) -> &'a [MaybeUninit<T>] {
|
|
// SAFETY: the caller must uphold the safety contract for `as_uninit_slice`.
|
|
unsafe { slice::from_raw_parts(self.cast().as_ptr(), self.len()) }
|
|
}
|
|
|
|
/// Returns a unique reference to a slice of possibly uninitialized values. In contrast to
|
|
/// [`as_mut`], this does not require that the value has to be initialized.
|
|
///
|
|
/// For the shared counterpart see [`as_uninit_slice`].
|
|
///
|
|
/// [`as_mut`]: NonNull::as_mut
|
|
/// [`as_uninit_slice`]: NonNull::as_uninit_slice
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// When calling this method, you have to ensure that all of the following is true:
|
|
///
|
|
/// * The pointer must be [valid] for reads and writes for `ptr.len() * size_of::<T>()`
|
|
/// many bytes, and it must be properly aligned. This means in particular:
|
|
///
|
|
/// * The entire memory range of this slice must be contained within a single allocation!
|
|
/// Slices can never span across multiple allocations.
|
|
///
|
|
/// * The pointer must be aligned even for zero-length slices. One
|
|
/// reason for this is that enum layout optimizations may rely on references
|
|
/// (including slices of any length) being aligned and non-null to distinguish
|
|
/// them from other data. You can obtain a pointer that is usable as `data`
|
|
/// for zero-length slices using [`NonNull::dangling()`].
|
|
///
|
|
/// * The total size `ptr.len() * size_of::<T>()` of the slice must be no larger than `isize::MAX`.
|
|
/// See the safety documentation of [`pointer::offset`].
|
|
///
|
|
/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
|
|
/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
|
|
/// In particular, while this reference exists, the memory the pointer points to must
|
|
/// not get accessed (read or written) through any other pointer.
|
|
///
|
|
/// This applies even if the result of this method is unused!
|
|
///
|
|
/// See also [`slice::from_raw_parts_mut`].
|
|
///
|
|
/// [valid]: crate::ptr#safety
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// #![feature(allocator_api, ptr_as_uninit)]
|
|
///
|
|
/// use std::alloc::{Allocator, Layout, Global};
|
|
/// use std::mem::MaybeUninit;
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let memory: NonNull<[u8]> = Global.allocate(Layout::new::<[u8; 32]>())?;
|
|
/// // This is safe as `memory` is valid for reads and writes for `memory.len()` many bytes.
|
|
/// // Note that calling `memory.as_mut()` is not allowed here as the content may be uninitialized.
|
|
/// # #[allow(unused_variables)]
|
|
/// let slice: &mut [MaybeUninit<u8>] = unsafe { memory.as_uninit_slice_mut() };
|
|
/// # // Prevent leaks for Miri.
|
|
/// # unsafe { Global.deallocate(memory.cast(), Layout::new::<[u8; 32]>()); }
|
|
/// # Ok::<_, std::alloc::AllocError>(())
|
|
/// ```
|
|
#[inline]
|
|
#[must_use]
|
|
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
|
|
pub const unsafe fn as_uninit_slice_mut<'a>(self) -> &'a mut [MaybeUninit<T>] {
|
|
// SAFETY: the caller must uphold the safety contract for `as_uninit_slice_mut`.
|
|
unsafe { slice::from_raw_parts_mut(self.cast().as_ptr(), self.len()) }
|
|
}
|
|
|
|
/// Returns a raw pointer to an element or subslice, without doing bounds
|
|
/// checking.
|
|
///
|
|
/// Calling this method with an out-of-bounds index or when `self` is not dereferenceable
|
|
/// is *[undefined behavior]* even if the resulting pointer is not used.
|
|
///
|
|
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(slice_ptr_get)]
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// let x = &mut [1, 2, 4];
|
|
/// let x = NonNull::slice_from_raw_parts(NonNull::new(x.as_mut_ptr()).unwrap(), x.len());
|
|
///
|
|
/// unsafe {
|
|
/// assert_eq!(x.get_unchecked_mut(1).as_ptr(), x.as_non_null_ptr().as_ptr().add(1));
|
|
/// }
|
|
/// ```
|
|
#[unstable(feature = "slice_ptr_get", issue = "74265")]
|
|
#[rustc_const_unstable(feature = "const_index", issue = "143775")]
|
|
#[inline]
|
|
pub const unsafe fn get_unchecked_mut<I>(self, index: I) -> NonNull<I::Output>
|
|
where
|
|
I: [const] SliceIndex<[T]>,
|
|
{
|
|
// SAFETY: the caller ensures that `self` is dereferenceable and `index` in-bounds.
|
|
// As a consequence, the resulting pointer cannot be null.
|
|
unsafe { NonNull::new_unchecked(self.as_ptr().get_unchecked_mut(index)) }
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: PointeeSized> Clone for NonNull<T> {
|
|
#[inline(always)]
|
|
fn clone(&self) -> Self {
|
|
*self
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: PointeeSized> Copy for NonNull<T> {}
|
|
|
|
#[unstable(feature = "coerce_unsized", issue = "18598")]
|
|
impl<T: PointeeSized, U: PointeeSized> CoerceUnsized<NonNull<U>> for NonNull<T> where T: Unsize<U> {}
|
|
|
|
#[unstable(feature = "dispatch_from_dyn", issue = "none")]
|
|
impl<T: PointeeSized, U: PointeeSized> DispatchFromDyn<NonNull<U>> for NonNull<T> where T: Unsize<U> {}
|
|
|
|
#[stable(feature = "pin", since = "1.33.0")]
|
|
unsafe impl<T: PointeeSized> PinCoerceUnsized for NonNull<T> {}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: PointeeSized> fmt::Debug for NonNull<T> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
fmt::Pointer::fmt(&self.as_ptr(), f)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: PointeeSized> fmt::Pointer for NonNull<T> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
fmt::Pointer::fmt(&self.as_ptr(), f)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: PointeeSized> Eq for NonNull<T> {}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: PointeeSized> PartialEq for NonNull<T> {
|
|
#[inline]
|
|
#[allow(ambiguous_wide_pointer_comparisons)]
|
|
fn eq(&self, other: &Self) -> bool {
|
|
self.as_ptr() == other.as_ptr()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: PointeeSized> Ord for NonNull<T> {
|
|
#[inline]
|
|
#[allow(ambiguous_wide_pointer_comparisons)]
|
|
fn cmp(&self, other: &Self) -> Ordering {
|
|
self.as_ptr().cmp(&other.as_ptr())
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: PointeeSized> PartialOrd for NonNull<T> {
|
|
#[inline]
|
|
#[allow(ambiguous_wide_pointer_comparisons)]
|
|
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
|
|
self.as_ptr().partial_cmp(&other.as_ptr())
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: PointeeSized> hash::Hash for NonNull<T> {
|
|
#[inline]
|
|
fn hash<H: hash::Hasher>(&self, state: &mut H) {
|
|
self.as_ptr().hash(state)
|
|
}
|
|
}
|
|
|
|
#[unstable(feature = "ptr_internals", issue = "none")]
|
|
#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
|
|
impl<T: PointeeSized> const From<Unique<T>> for NonNull<T> {
|
|
#[inline]
|
|
fn from(unique: Unique<T>) -> Self {
|
|
unique.as_non_null_ptr()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
|
|
impl<T: PointeeSized> const From<&mut T> for NonNull<T> {
|
|
/// Converts a `&mut T` to a `NonNull<T>`.
|
|
///
|
|
/// This conversion is safe and infallible since references cannot be null.
|
|
#[inline]
|
|
fn from(r: &mut T) -> Self {
|
|
NonNull::from_mut(r)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
|
|
impl<T: PointeeSized> const From<&T> for NonNull<T> {
|
|
/// Converts a `&T` to a `NonNull<T>`.
|
|
///
|
|
/// This conversion is safe and infallible since references cannot be null.
|
|
#[inline]
|
|
fn from(r: &T) -> Self {
|
|
NonNull::from_ref(r)
|
|
}
|
|
}
|