586 lines
24 KiB
Rust
586 lines
24 KiB
Rust
use crate::cmp::Ordering;
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use crate::convert::From;
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use crate::fmt;
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use crate::hash;
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use crate::marker::Unsize;
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use crate::mem::{self, MaybeUninit};
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use crate::ops::{CoerceUnsized, DispatchFromDyn};
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use crate::ptr::Unique;
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use crate::slice::{self, SliceIndex};
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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`. If this is incorrect
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/// for your use case, you should include some [`PhantomData`] in your type to
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/// provide invariance, such as `PhantomData<Cell<T>>` or `PhantomData<&'a mut T>`.
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/// Usually this won't be necessary; covariance is correct for most safe abstractions,
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/// such as `Box`, `Rc`, `Arc`, `Vec`, and `LinkedList`. This is the case because they
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/// provide a public API that follows the normal shared XOR mutable rules of Rust.
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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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/// [`PhantomData`]: crate::marker::PhantomData
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/// [`UnsafeCell<T>`]: crate::cell::UnsafeCell
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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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pub struct NonNull<T: ?Sized> {
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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: ?Sized> !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: ?Sized> !Sync for NonNull<T> {}
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impl<T: Sized> NonNull<T> {
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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 pointer value may potentially represent a valid pointer to
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/// a `T`, which means this must not be used as a "not yet initialized"
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/// sentinel value. Types that lazily allocate must track initialization by
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/// some other means.
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#[stable(feature = "nonnull", since = "1.25.0")]
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#[rustc_const_stable(feature = "const_nonnull_dangling", since = "1.32.0")]
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#[inline]
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pub const fn dangling() -> Self {
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// SAFETY: mem::align_of() returns a non-zero usize which is then casted
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// to a *mut T. Therefore, `ptr` is not null and the conditions for
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// calling new_unchecked() are respected.
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unsafe {
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let ptr = mem::align_of::<T>() as *mut T;
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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 all of the following is true:
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///
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/// * The pointer must be properly aligned.
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///
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/// * It must be "dereferencable" in the sense defined in [the module documentation].
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///
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/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
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/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
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/// In particular, for the duration of this lifetime, the memory the pointer points to must
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/// not get mutated (except inside `UnsafeCell`).
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///
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/// This applies even if the result of this method is unused!
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///
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/// [the module documentation]: crate::ptr#safety
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#[inline]
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#[unstable(feature = "ptr_as_uninit", issue = "75402")]
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pub unsafe fn as_uninit_ref(&self) -> &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 all of the following is true:
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///
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/// * The pointer must be properly aligned.
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///
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/// * It must be "dereferencable" in the sense defined in [the module documentation].
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///
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/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
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/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
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/// In particular, for the duration of this lifetime, the memory the pointer points to must
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/// not get accessed (read or written) through any other pointer.
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///
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/// This applies even if the result of this method is unused!
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///
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/// [the module documentation]: crate::ptr#safety
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#[inline]
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#[unstable(feature = "ptr_as_uninit", issue = "75402")]
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pub unsafe fn as_uninit_mut(&mut self) -> &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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}
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impl<T: ?Sized> 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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#[stable(feature = "nonnull", since = "1.25.0")]
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#[rustc_const_stable(feature = "const_nonnull_new_unchecked", since = "1.32.0")]
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#[inline]
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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 { NonNull { pointer: ptr as _ } }
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}
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/// Creates a new `NonNull` if `ptr` is non-null.
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#[stable(feature = "nonnull", since = "1.25.0")]
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#[inline]
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pub 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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/// Acquires the underlying `*mut` pointer.
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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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#[inline]
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pub const fn as_ptr(self) -> *mut T {
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self.pointer as *mut T
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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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///
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/// # Safety
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///
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/// When calling this method, you have to ensure that all of the following is true:
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///
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/// * The pointer must be properly aligned.
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///
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/// * It must be "dereferencable" in the sense defined in [the module documentation].
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///
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/// * The pointer must point to an initialized instance of `T`.
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///
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/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
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/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
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/// In particular, for the duration of this lifetime, the memory the pointer points to must
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/// not get mutated (except inside `UnsafeCell`).
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///
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/// This applies even if the result of this method is unused!
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/// (The part about being initialized is not yet fully decided, but until
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/// it is, the only safe approach is to ensure that they are indeed initialized.)
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///
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/// [the module documentation]: crate::ptr#safety
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#[stable(feature = "nonnull", since = "1.25.0")]
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#[inline]
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pub unsafe fn as_ref(&self) -> &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.as_ptr() }
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}
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/// Returns a unique reference to the value. If the value may be uninitialized, [`as_uninit_mut`]
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/// must be used instead.
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///
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/// For the shared counterpart see [`as_ref`].
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///
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/// [`as_uninit_mut`]: NonNull::as_uninit_mut
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/// [`as_ref`]: NonNull::as_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 all of the following is true:
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///
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/// * The pointer must be properly aligned.
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///
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/// * It must be "dereferencable" in the sense defined in [the module documentation].
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///
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/// * The pointer must point to an initialized instance of `T`.
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///
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/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
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/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
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/// In particular, for the duration of this lifetime, the memory the pointer points to must
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/// not get accessed (read or written) through any other pointer.
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///
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/// This applies even if the result of this method is unused!
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/// (The part about being initialized is not yet fully decided, but until
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/// it is, the only safe approach is to ensure that they are indeed initialized.)
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///
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/// [the module documentation]: crate::ptr#safety
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#[stable(feature = "nonnull", since = "1.25.0")]
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#[inline]
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pub unsafe fn as_mut(&mut self) -> &mut T {
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// SAFETY: the caller must guarantee that `self` meets all the
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// requirements for a mutable reference.
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unsafe { &mut *self.as_ptr() }
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}
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/// Casts to a pointer of another type.
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#[stable(feature = "nonnull_cast", since = "1.27.0")]
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#[rustc_const_stable(feature = "const_nonnull_cast", since = "1.32.0")]
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#[inline]
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pub const fn cast<U>(self) -> NonNull<U> {
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// SAFETY: `self` is a `NonNull` pointer which is necessarily non-null
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unsafe { NonNull::new_unchecked(self.as_ptr() as *mut U) }
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}
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}
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impl<T> NonNull<[T]> {
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/// Creates a non-null raw slice from a thin pointer and a length.
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///
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/// The `len` argument is the number of **elements**, not the number of bytes.
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///
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/// This function is safe, but dereferencing the return value is unsafe.
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/// See the documentation of [`slice::from_raw_parts`] for slice safety requirements.
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///
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/// # Examples
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///
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/// ```rust
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/// #![feature(nonnull_slice_from_raw_parts)]
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///
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/// use std::ptr::NonNull;
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///
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/// // create a slice pointer when starting out with a pointer to the first element
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/// let mut x = [5, 6, 7];
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/// let nonnull_pointer = NonNull::new(x.as_mut_ptr()).unwrap();
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/// let slice = NonNull::slice_from_raw_parts(nonnull_pointer, 3);
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/// assert_eq!(unsafe { slice.as_ref()[2] }, 7);
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/// ```
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///
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/// (Note that this example artificially demonstrates a use of this method,
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/// but `let slice = NonNull::from(&x[..]);` would be a better way to write code like this.)
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#[unstable(feature = "nonnull_slice_from_raw_parts", issue = "71941")]
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#[rustc_const_unstable(feature = "const_nonnull_slice_from_raw_parts", issue = "71941")]
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#[inline]
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pub const fn slice_from_raw_parts(data: NonNull<T>, len: usize) -> Self {
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// SAFETY: `data` is a `NonNull` pointer which is necessarily non-null
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unsafe { Self::new_unchecked(super::slice_from_raw_parts_mut(data.as_ptr(), len)) }
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}
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/// Returns the length of a non-null raw slice.
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///
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/// The returned value is the number of **elements**, not the number of bytes.
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///
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/// This function is safe, even when the non-null raw slice cannot be dereferenced to a slice
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/// because the pointer does not have a valid address.
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///
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/// # Examples
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///
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/// ```rust
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/// #![feature(slice_ptr_len, nonnull_slice_from_raw_parts)]
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/// use std::ptr::NonNull;
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///
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/// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
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/// assert_eq!(slice.len(), 3);
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/// ```
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#[unstable(feature = "slice_ptr_len", issue = "71146")]
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#[rustc_const_unstable(feature = "const_slice_ptr_len", issue = "71146")]
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#[inline]
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pub const fn len(self) -> usize {
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self.as_ptr().len()
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}
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/// Returns a non-null pointer to the slice's buffer.
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///
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/// # Examples
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///
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/// ```rust
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/// #![feature(slice_ptr_get, nonnull_slice_from_raw_parts)]
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/// use std::ptr::NonNull;
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///
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/// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
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/// assert_eq!(slice.as_non_null_ptr(), NonNull::new(1 as *mut i8).unwrap());
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/// ```
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#[inline]
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#[unstable(feature = "slice_ptr_get", issue = "74265")]
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#[rustc_const_unstable(feature = "slice_ptr_get", issue = "74265")]
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pub const fn as_non_null_ptr(self) -> NonNull<T> {
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// SAFETY: We know `self` is non-null.
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unsafe { NonNull::new_unchecked(self.as_ptr().as_mut_ptr()) }
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}
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/// Returns a raw pointer to the slice's buffer.
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///
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/// # Examples
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///
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/// ```rust
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/// #![feature(slice_ptr_get, nonnull_slice_from_raw_parts)]
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/// use std::ptr::NonNull;
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///
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/// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
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/// assert_eq!(slice.as_mut_ptr(), 1 as *mut i8);
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/// ```
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#[inline]
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#[unstable(feature = "slice_ptr_get", issue = "74265")]
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#[rustc_const_unstable(feature = "slice_ptr_get", issue = "74265")]
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pub const fn as_mut_ptr(self) -> *mut T {
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self.as_non_null_ptr().as_ptr()
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}
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/// Returns a shared reference to a slice of possibly uninitialized values. In contrast to
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/// [`as_ref`], this does not require that the value has to be initialized.
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///
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/// For the mutable counterpart see [`as_uninit_slice_mut`].
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///
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/// [`as_ref`]: NonNull::as_ref
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/// [`as_uninit_slice_mut`]: NonNull::as_uninit_slice_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 all of the following is true:
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///
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/// * The pointer must be [valid] for reads for `ptr.len() * mem::size_of::<T>()` many bytes,
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/// and it must be properly aligned. This means in particular:
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///
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/// * The entire memory range of this slice must be contained within a single allocated object!
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/// Slices can never span across multiple allocated objects.
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///
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/// * The pointer must be aligned even for zero-length slices. One
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/// reason for this is that enum layout optimizations may rely on references
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/// (including slices of any length) being aligned and non-null to distinguish
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/// them from other data. You can obtain a pointer that is usable as `data`
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/// for zero-length slices using [`NonNull::dangling()`].
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///
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/// * The total size `ptr.len() * mem::size_of::<T>()` of the slice must be no larger than `isize::MAX`.
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/// See the safety documentation of [`pointer::offset`].
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///
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/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
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/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
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/// In particular, for the duration of this lifetime, the memory the pointer points to must
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/// not get mutated (except inside `UnsafeCell`).
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///
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/// This applies even if the result of this method is unused!
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///
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/// See also [`slice::from_raw_parts`].
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///
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/// [valid]: crate::ptr#safety
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/// [`pointer::offset`]: ../../std/primitive.pointer.html#method.offset
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#[inline]
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#[unstable(feature = "ptr_as_uninit", issue = "75402")]
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pub unsafe fn as_uninit_slice(&self) -> &[MaybeUninit<T>] {
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// SAFETY: the caller must uphold the safety contract for `as_uninit_slice`.
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unsafe { slice::from_raw_parts(self.cast().as_ptr(), self.len()) }
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}
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/// Returns a unique reference to a slice of possibly uninitialized values. In contrast to
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/// [`as_mut`], this does not require that the value has to be initialized.
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///
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/// For the shared counterpart see [`as_uninit_slice`].
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///
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/// [`as_mut`]: NonNull::as_mut
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/// [`as_uninit_slice`]: NonNull::as_uninit_slice
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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 all of the following is true:
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///
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/// * The pointer must be [valid] for reads and writes for `ptr.len() * mem::size_of::<T>()`
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/// many bytes, and it must be properly aligned. This means in particular:
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///
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/// * The entire memory range of this slice must be contained within a single allocated object!
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/// Slices can never span across multiple allocated objects.
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///
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/// * The pointer must be aligned even for zero-length slices. One
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/// reason for this is that enum layout optimizations may rely on references
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/// (including slices of any length) being aligned and non-null to distinguish
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/// them from other data. You can obtain a pointer that is usable as `data`
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/// for zero-length slices using [`NonNull::dangling()`].
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///
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/// * The total size `ptr.len() * mem::size_of::<T>()` of the slice must be no larger than `isize::MAX`.
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/// See the safety documentation of [`pointer::offset`].
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///
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/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
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/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
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/// In particular, for the duration of this lifetime, the memory the pointer points to must
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/// not get accessed (read or written) through any other pointer.
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///
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/// This applies even if the result of this method is unused!
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///
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/// See also [`slice::from_raw_parts_mut`].
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///
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/// [valid]: crate::ptr#safety
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/// [`pointer::offset`]: ../../std/primitive.pointer.html#method.offset
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///
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/// # Examples
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///
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/// ```rust
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/// #![feature(allocator_api, ptr_as_uninit)]
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///
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/// use std::alloc::{AllocRef, Layout, Global};
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/// use std::mem::MaybeUninit;
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/// use std::ptr::NonNull;
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///
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/// let memory: NonNull<[u8]> = Global.alloc(Layout::new::<[u8; 32]>())?;
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/// // This is safe as `memory` is valid for reads and writes for `memory.len()` many bytes.
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/// // Note that calling `memory.as_mut()` is not allowed here as the content may be uninitialized.
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/// # #[allow(unused_variables)]
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/// let slice: &mut [MaybeUninit<u8>] = unsafe { memory.as_uninit_slice_mut() };
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/// # Ok::<_, std::alloc::AllocErr>(())
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/// ```
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#[inline]
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#[unstable(feature = "ptr_as_uninit", issue = "75402")]
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pub unsafe fn as_uninit_slice_mut(&self) -> &mut [MaybeUninit<T>] {
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// SAFETY: the caller must uphold the safety contract for `as_uninit_slice_mut`.
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unsafe { slice::from_raw_parts_mut(self.cast().as_ptr(), self.len()) }
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|
}
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|
|
|
/// Returns a raw pointer to an element or subslice, without doing bounds
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|
/// checking.
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|
///
|
|
/// Calling this method with an out-of-bounds index or when `self` is not dereferencable
|
|
/// is *[undefined behavior]* even if the resulting pointer is not used.
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|
///
|
|
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
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|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(slice_ptr_get, nonnull_slice_from_raw_parts)]
|
|
/// 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());
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|
///
|
|
/// 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")]
|
|
#[inline]
|
|
pub unsafe fn get_unchecked_mut<I>(self, index: I) -> NonNull<I::Output>
|
|
where
|
|
I: SliceIndex<[T]>,
|
|
{
|
|
// SAFETY: the caller ensures that `self` is dereferencable 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: ?Sized> Clone for NonNull<T> {
|
|
#[inline]
|
|
fn clone(&self) -> Self {
|
|
*self
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: ?Sized> Copy for NonNull<T> {}
|
|
|
|
#[unstable(feature = "coerce_unsized", issue = "27732")]
|
|
impl<T: ?Sized, U: ?Sized> CoerceUnsized<NonNull<U>> for NonNull<T> where T: Unsize<U> {}
|
|
|
|
#[unstable(feature = "dispatch_from_dyn", issue = "none")]
|
|
impl<T: ?Sized, U: ?Sized> DispatchFromDyn<NonNull<U>> for NonNull<T> where T: Unsize<U> {}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: ?Sized> 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: ?Sized> 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: ?Sized> Eq for NonNull<T> {}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: ?Sized> PartialEq for NonNull<T> {
|
|
#[inline]
|
|
fn eq(&self, other: &Self) -> bool {
|
|
self.as_ptr() == other.as_ptr()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: ?Sized> Ord for NonNull<T> {
|
|
#[inline]
|
|
fn cmp(&self, other: &Self) -> Ordering {
|
|
self.as_ptr().cmp(&other.as_ptr())
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: ?Sized> PartialOrd for NonNull<T> {
|
|
#[inline]
|
|
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: ?Sized> 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")]
|
|
impl<T: ?Sized> From<Unique<T>> for NonNull<T> {
|
|
#[inline]
|
|
fn from(unique: Unique<T>) -> Self {
|
|
// SAFETY: A Unique pointer cannot be null, so the conditions for
|
|
// new_unchecked() are respected.
|
|
unsafe { NonNull::new_unchecked(unique.as_ptr()) }
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: ?Sized> From<&mut T> for NonNull<T> {
|
|
#[inline]
|
|
fn from(reference: &mut T) -> Self {
|
|
// SAFETY: A mutable reference cannot be null.
|
|
unsafe { NonNull { pointer: reference as *mut T } }
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: ?Sized> From<&T> for NonNull<T> {
|
|
#[inline]
|
|
fn from(reference: &T) -> Self {
|
|
// SAFETY: A reference cannot be null, so the conditions for
|
|
// new_unchecked() are respected.
|
|
unsafe { NonNull { pointer: reference as *const T } }
|
|
}
|
|
}
|