mirror of https://github.com/rust-lang/rust
1857 lines
75 KiB
Rust
1857 lines
75 KiB
Rust
use crate::cmp::Ordering;
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use crate::fmt;
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use crate::hash;
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use crate::intrinsics;
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use crate::marker::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::ptr;
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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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/// `*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>` was chosen to be covariant over `T`. This makes it
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/// possible to use `NonNull<T>` when building covariant types, but introduces the
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/// risk of unsoundness if used in a type that shouldn't actually be covariant.
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/// (The opposite choice was made for `*mut T` even though technically the unsoundness
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/// could only be caused by calling unsafe functions.)
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///
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/// Covariance is correct for most safe abstractions, such as `Box`, `Rc`, `Arc`, `Vec`,
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/// and `LinkedList`. This is the case because they provide a public API that follows the
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/// normal shared XOR mutable rules of Rust.
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///
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/// If your type cannot safely be covariant, you must ensure it contains some
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/// additional field to provide invariance. Often this field will be a [`PhantomData`]
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/// type like `PhantomData<Cell<T>>` or `PhantomData<&'a mut T>`.
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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::mem::{size_of, align_of};
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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: ?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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///
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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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// 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 = crate::ptr::dangling_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 "dereferenceable" 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, while this reference exists, 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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#[must_use]
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#[unstable(feature = "ptr_as_uninit", issue = "75402")]
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#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
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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 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 "dereferenceable" 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, while this reference exists, 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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#[must_use]
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#[unstable(feature = "ptr_as_uninit", issue = "75402")]
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#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
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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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}
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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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///
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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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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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/// # 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_unstable(feature = "const_nonnull_new", issue = "93235")]
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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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/// 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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#[rustc_const_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<()>,
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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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#[rustc_const_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 API and its claimed semantics are part of the Strict Provenance experiment,
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/// see the [`ptr` module documentation][crate::ptr].
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#[must_use]
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#[inline]
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#[unstable(feature = "strict_provenance", issue = "95228")]
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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.pointer.addr()) }
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}
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/// Creates a new pointer with the given address.
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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 API and its claimed semantics are part of the Strict Provenance experiment,
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/// see the [`ptr` module documentation][crate::ptr].
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#[must_use]
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#[inline]
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#[unstable(feature = "strict_provenance", issue = "95228")]
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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.pointer.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.
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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 API and its claimed semantics are part of the Strict Provenance experiment,
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/// see the [`ptr` module documentation][crate::ptr].
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#[must_use]
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#[inline]
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#[unstable(feature = "strict_provenance", issue = "95228")]
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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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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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///
|
|
/// # Safety
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|
///
|
|
/// When calling this method, you have to ensure that all of the following is true:
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|
///
|
|
/// * The pointer must be properly aligned.
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|
///
|
|
/// * It must be "dereferenceable" in the sense defined in [the module documentation].
|
|
///
|
|
/// * The pointer must point to an initialized instance of `T`.
|
|
///
|
|
/// * 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!
|
|
/// (The part about being initialized is not yet fully decided, but until
|
|
/// it is, the only safe approach is to ensure that they are indeed initialized.)
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
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|
///
|
|
/// let mut x = 0u32;
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/// let ptr = NonNull::new(&mut x as *mut _).expect("ptr is null!");
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///
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/// let ref_x = unsafe { ptr.as_ref() };
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/// println!("{ref_x}");
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/// ```
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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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#[rustc_const_stable(feature = "const_nonnull_as_ref", since = "1.73.0")]
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#[must_use]
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#[inline(always)]
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pub const unsafe fn as_ref<'a>(&self) -> &'a T {
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// SAFETY: the caller must guarantee that `self` meets all the
|
|
// requirements for a reference.
|
|
// `cast_const` avoids a mutable raw pointer deref.
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unsafe { &*self.as_ptr().cast_const() }
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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.
|
|
///
|
|
/// For the shared counterpart see [`as_ref`].
|
|
///
|
|
/// [`as_uninit_mut`]: NonNull::as_uninit_mut
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|
/// [`as_ref`]: NonNull::as_ref
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|
///
|
|
/// # Safety
|
|
///
|
|
/// When calling this method, you have to ensure that all of the following is true:
|
|
///
|
|
/// * The pointer must be properly aligned.
|
|
///
|
|
/// * It must be "dereferenceable" in the sense defined in [the module documentation].
|
|
///
|
|
/// * The pointer must point to an initialized instance of `T`.
|
|
///
|
|
/// * 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!
|
|
/// (The part about being initialized is not yet fully decided, but until
|
|
/// it is, the only safe approach is to ensure that they are indeed initialized.)
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::ptr::NonNull;
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|
///
|
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/// let mut x = 0u32;
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|
/// let mut ptr = NonNull::new(&mut x).expect("null pointer");
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///
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|
/// let x_ref = unsafe { ptr.as_mut() };
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|
/// assert_eq!(*x_ref, 0);
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/// *x_ref += 2;
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/// assert_eq!(*x_ref, 2);
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/// ```
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|
///
|
|
/// [the module documentation]: crate::ptr#safety
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
|
|
#[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 } }
|
|
}
|
|
|
|
/// Calculates the offset from 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:
|
|
///
|
|
/// * Both the starting and resulting pointer must be either in bounds or one
|
|
/// byte past the end of the same [allocated object].
|
|
///
|
|
/// * The computed offset, **in bytes**, cannot overflow an `isize`.
|
|
///
|
|
/// * The offset being in bounds cannot rely on "wrapping around" the address
|
|
/// space. That is, the infinite-precision sum, **in bytes** must fit in a usize.
|
|
///
|
|
/// The compiler and standard library generally tries to ensure allocations
|
|
/// never reach a size where an offset is a concern. For instance, `Vec`
|
|
/// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
|
|
/// `vec.as_ptr().add(vec.len())` is always safe.
|
|
///
|
|
/// Most platforms fundamentally can't even construct such an allocation.
|
|
/// For instance, no known 64-bit platform can ever serve a request
|
|
/// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
|
|
/// However, some 32-bit and 16-bit platforms may successfully serve a request for
|
|
/// more than `isize::MAX` bytes with things like Physical Address
|
|
/// Extension. As such, memory acquired directly from allocators or memory
|
|
/// mapped files *may* be too large to handle with this function.
|
|
///
|
|
/// [allocated object]: crate::ptr#allocated-object
|
|
///
|
|
/// # 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
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.pointer, 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
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.pointer.byte_offset(count) } }
|
|
}
|
|
|
|
/// Calculates the offset from 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:
|
|
///
|
|
/// * Both the starting and resulting pointer must be either in bounds or one
|
|
/// byte past the end of the same [allocated object].
|
|
///
|
|
/// * The computed offset, **in bytes**, cannot overflow an `isize`.
|
|
///
|
|
/// * The offset being in bounds cannot rely on "wrapping around" the address
|
|
/// space. That is, the infinite-precision sum must fit in a `usize`.
|
|
///
|
|
/// The compiler and standard library generally tries to ensure allocations
|
|
/// never reach a size where an offset is a concern. For instance, `Vec`
|
|
/// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
|
|
/// `vec.as_ptr().add(vec.len())` is always safe.
|
|
///
|
|
/// Most platforms fundamentally can't even construct such an allocation.
|
|
/// For instance, no known 64-bit platform can ever serve a request
|
|
/// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
|
|
/// However, some 32-bit and 16-bit platforms may successfully serve a request for
|
|
/// more than `isize::MAX` bytes with things like Physical Address
|
|
/// Extension. As such, memory acquired directly from allocators or memory
|
|
/// mapped files *may* be too large to handle with this function.
|
|
///
|
|
/// [allocated object]: crate::ptr#allocated-object
|
|
///
|
|
/// # 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
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.pointer, 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
|
|
#[rustc_allow_const_fn_unstable(set_ptr_value)]
|
|
#[stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
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.pointer.byte_add(count) } }
|
|
}
|
|
|
|
/// Calculates the 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:
|
|
///
|
|
/// * Both the starting and resulting pointer must be either in bounds or one
|
|
/// byte past the end of the same [allocated object].
|
|
///
|
|
/// * The computed offset cannot exceed `isize::MAX` **bytes**.
|
|
///
|
|
/// * The offset being in bounds cannot rely on "wrapping around" the address
|
|
/// space. That is, the infinite-precision sum must fit in a usize.
|
|
///
|
|
/// The compiler and standard library generally tries to ensure allocations
|
|
/// never reach a size where an offset is a concern. For instance, `Vec`
|
|
/// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
|
|
/// `vec.as_ptr().add(vec.len()).sub(vec.len())` is always safe.
|
|
///
|
|
/// Most platforms fundamentally can't even construct such an allocation.
|
|
/// For instance, no known 64-bit platform can ever serve a request
|
|
/// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
|
|
/// However, some 32-bit and 16-bit platforms may successfully serve a request for
|
|
/// more than `isize::MAX` bytes with things like Physical Address
|
|
/// Extension. As such, memory acquired directly from allocators or memory
|
|
/// mapped files *may* be too large to handle with this function.
|
|
///
|
|
/// [allocated object]: crate::ptr#allocated-object
|
|
///
|
|
/// # 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_allow_const_fn_unstable(unchecked_neg)]
|
|
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
|
|
#[rustc_allow_const_fn_unstable(set_ptr_value)]
|
|
#[stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
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.pointer.byte_sub(count) } }
|
|
}
|
|
|
|
/// Calculates the distance between two pointers. The returned value is in
|
|
/// units of T: the distance in bytes divided by `mem::size_of::<T>()`.
|
|
///
|
|
/// This is equivalent to `(self as isize - origin as isize) / (mem::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:
|
|
///
|
|
/// * Both `self` and `origin` must be either in bounds or one
|
|
/// byte past the end of the same [allocated object].
|
|
///
|
|
/// * Both pointers must be *derived from* a pointer to the same object.
|
|
/// (See below for an example.)
|
|
///
|
|
/// * The distance between the pointers, in bytes, must be an exact multiple
|
|
/// of the size of `T`.
|
|
///
|
|
/// * The distance between the pointers, **in bytes**, cannot overflow an `isize`.
|
|
///
|
|
/// * The distance being in bounds cannot rely on "wrapping around" the address space.
|
|
///
|
|
/// Rust types are never larger than `isize::MAX` and Rust allocations never wrap around the
|
|
/// address space, so two pointers within some value of any Rust type `T` will always satisfy
|
|
/// the last two conditions. The standard library also generally ensures that allocations
|
|
/// never reach a size where an offset is a concern. For instance, `Vec` and `Box` ensure they
|
|
/// never allocate more than `isize::MAX` bytes, so `ptr_into_vec.offset_from(vec.as_ptr())`
|
|
/// always satisfies the last two conditions.
|
|
///
|
|
/// Most platforms fundamentally can't even construct such a large allocation.
|
|
/// For instance, no known 64-bit platform can ever serve a request
|
|
/// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
|
|
/// However, some 32-bit and 16-bit platforms may successfully serve a request for
|
|
/// more than `isize::MAX` bytes with things like Physical Address
|
|
/// Extension. As such, memory acquired directly from allocators or memory
|
|
/// mapped files *may* be too large to handle with this function.
|
|
/// (Note that [`offset`] and [`add`] also have a similar limitation and hence cannot be used on
|
|
/// such large allocations either.)
|
|
///
|
|
/// The requirement for pointers to be derived from the same allocated object 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) / mem::size_of::<T>()`.
|
|
// FIXME: recommend `addr()` instead of `as usize` once that is stable.
|
|
///
|
|
/// [`add`]: #method.add
|
|
/// [allocated object]: crate::ptr#allocated-object
|
|
///
|
|
/// # 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
|
|
/// #![feature(strict_provenance)]
|
|
/// 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, but derived from ptr1.
|
|
/// let ptr2_other = NonNull::new(ptr1.as_ptr().wrapping_byte_offset(diff)).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 the same address!
|
|
///
|
|
/// let zero = 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
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.pointer.offset_from(origin.pointer) }
|
|
}
|
|
|
|
/// Calculates the distance between two pointers. 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
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.pointer.byte_offset_from(origin.pointer) }
|
|
}
|
|
|
|
// N.B. `wrapping_offset``, `wrapping_add`, etc are not implemented because they can wrap to null
|
|
|
|
/// Calculates the distance between two pointers, *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 `mem::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
|
|
/// # #![feature(ptr_sub_ptr)]
|
|
/// # unsafe fn blah(ptr: std::ptr::NonNull<u32>, origin: std::ptr::NonNull<u32>, count: usize) -> bool {
|
|
/// ptr.sub_ptr(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
|
|
///
|
|
/// ```
|
|
/// #![feature(ptr_sub_ptr)]
|
|
/// 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.sub_ptr(ptr1), 2);
|
|
/// assert_eq!(ptr1.add(2), ptr2);
|
|
/// assert_eq!(ptr2.sub(2), ptr1);
|
|
/// assert_eq!(ptr2.sub_ptr(ptr2), 0);
|
|
/// }
|
|
///
|
|
/// // This would be incorrect, as the pointers are not correctly ordered:
|
|
/// // ptr1.sub_ptr(ptr2)
|
|
/// ```
|
|
#[inline]
|
|
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
|
|
#[unstable(feature = "ptr_sub_ptr", issue = "95892")]
|
|
#[rustc_const_unstable(feature = "const_ptr_sub_ptr", issue = "95892")]
|
|
pub const unsafe fn sub_ptr(self, subtracted: NonNull<T>) -> usize
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `sub_ptr`.
|
|
unsafe { self.pointer.sub_ptr(subtracted.pointer) }
|
|
}
|
|
|
|
/// 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
pub const unsafe fn read(self) -> T
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `read`.
|
|
unsafe { ptr::read(self.pointer) }
|
|
}
|
|
|
|
/// 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 = "CURRENT_RUSTC_VERSION")]
|
|
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.pointer) }
|
|
}
|
|
|
|
/// 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_stable(feature = "non_null_convenience", since = "CURRENT_RUSTC_VERSION")]
|
|
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.pointer) }
|
|
}
|
|
|
|
/// 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
|
|
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.pointer, 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
|
|
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.pointer, 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
|
|
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.pointer, 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
|
|
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.pointer, 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 = "CURRENT_RUSTC_VERSION")]
|
|
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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
|
|
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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
|
|
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 = "CURRENT_RUSTC_VERSION")]
|
|
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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
|
|
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 = "CURRENT_RUSTC_VERSION")]
|
|
pub 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_unstable(feature = "const_swap", issue = "83163")]
|
|
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`. It is permissible for the implementation to *always*
|
|
/// return `usize::MAX`. Only your algorithm's performance can depend
|
|
/// on getting a usable offset here, not its correctness.
|
|
///
|
|
/// 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.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// The function panics if `align` is not a power-of-two.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Accessing adjacent `u8` as `u16`
|
|
///
|
|
/// ```
|
|
/// use std::mem::align_of;
|
|
/// 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 = "CURRENT_RUSTC_VERSION")]
|
|
#[rustc_const_unstable(feature = "const_align_offset", issue = "90962")]
|
|
pub const 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.pointer, 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());
|
|
/// ```
|
|
///
|
|
/// # At compiletime
|
|
/// **Note: Alignment at compiletime is experimental and subject to change. See the
|
|
/// [tracking issue] for details.**
|
|
///
|
|
/// At compiletime, the compiler may not know where a value will end up in memory.
|
|
/// Calling this function on a pointer created from a reference at compiletime will only
|
|
/// return `true` if the pointer is guaranteed to be aligned. This means that the pointer
|
|
/// is never aligned if cast to a type with a stricter alignment than the reference's
|
|
/// underlying allocation.
|
|
///
|
|
/// ```
|
|
/// #![feature(const_nonnull_new)]
|
|
/// #![feature(const_option)]
|
|
/// #![feature(const_pointer_is_aligned)]
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// // On some platforms, the alignment of primitives is less than their size.
|
|
/// #[repr(align(4))]
|
|
/// struct AlignedI32(i32);
|
|
/// #[repr(align(8))]
|
|
/// struct AlignedI64(i64);
|
|
///
|
|
/// const _: () = {
|
|
/// let data = [AlignedI32(42), AlignedI32(42)];
|
|
/// let ptr = NonNull::<AlignedI32>::new(&data[0] as *const _ as *mut _).unwrap();
|
|
/// assert!(ptr.is_aligned());
|
|
///
|
|
/// // At runtime either `ptr1` or `ptr2` would be aligned, but at compiletime neither is aligned.
|
|
/// let ptr1 = ptr.cast::<AlignedI64>();
|
|
/// let ptr2 = unsafe { ptr.add(1).cast::<AlignedI64>() };
|
|
/// assert!(!ptr1.is_aligned());
|
|
/// assert!(!ptr2.is_aligned());
|
|
/// };
|
|
/// ```
|
|
///
|
|
/// Due to this behavior, it is possible that a runtime pointer derived from a compiletime
|
|
/// pointer is aligned, even if the compiletime pointer wasn't aligned.
|
|
///
|
|
/// ```
|
|
/// #![feature(const_pointer_is_aligned)]
|
|
///
|
|
/// // On some platforms, the alignment of primitives is less than their size.
|
|
/// #[repr(align(4))]
|
|
/// struct AlignedI32(i32);
|
|
/// #[repr(align(8))]
|
|
/// struct AlignedI64(i64);
|
|
///
|
|
/// // At compiletime, neither `COMPTIME_PTR` nor `COMPTIME_PTR + 1` is aligned.
|
|
/// const COMPTIME_PTR: *const AlignedI32 = &AlignedI32(42);
|
|
/// const _: () = assert!(!COMPTIME_PTR.cast::<AlignedI64>().is_aligned());
|
|
/// const _: () = assert!(!COMPTIME_PTR.wrapping_add(1).cast::<AlignedI64>().is_aligned());
|
|
///
|
|
/// // At runtime, either `runtime_ptr` or `runtime_ptr + 1` is aligned.
|
|
/// let runtime_ptr = COMPTIME_PTR;
|
|
/// assert_ne!(
|
|
/// runtime_ptr.cast::<AlignedI64>().is_aligned(),
|
|
/// runtime_ptr.wrapping_add(1).cast::<AlignedI64>().is_aligned(),
|
|
/// );
|
|
/// ```
|
|
///
|
|
/// If a pointer is created from a fixed address, this function behaves the same during
|
|
/// runtime and compiletime.
|
|
///
|
|
/// ```
|
|
/// #![feature(const_pointer_is_aligned)]
|
|
/// #![feature(const_option)]
|
|
/// #![feature(const_nonnull_new)]
|
|
/// use std::ptr::NonNull;
|
|
///
|
|
/// // On some platforms, the alignment of primitives is less than their size.
|
|
/// #[repr(align(4))]
|
|
/// struct AlignedI32(i32);
|
|
/// #[repr(align(8))]
|
|
/// struct AlignedI64(i64);
|
|
///
|
|
/// const _: () = {
|
|
/// let ptr = NonNull::new(40 as *mut AlignedI32).unwrap();
|
|
/// assert!(ptr.is_aligned());
|
|
///
|
|
/// // For pointers with a known address, runtime and compiletime behavior are identical.
|
|
/// let ptr1 = ptr.cast::<AlignedI64>();
|
|
/// let ptr2 = NonNull::new(ptr.as_ptr().wrapping_add(1)).unwrap().cast::<AlignedI64>();
|
|
/// assert!(ptr1.is_aligned());
|
|
/// assert!(!ptr2.is_aligned());
|
|
/// };
|
|
/// ```
|
|
///
|
|
/// [tracking issue]: https://github.com/rust-lang/rust/issues/104203
|
|
#[inline]
|
|
#[must_use]
|
|
#[stable(feature = "pointer_is_aligned", since = "1.79.0")]
|
|
#[rustc_const_unstable(feature = "const_pointer_is_aligned", issue = "104203")]
|
|
pub const fn is_aligned(self) -> bool
|
|
where
|
|
T: Sized,
|
|
{
|
|
self.pointer.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));
|
|
/// ```
|
|
///
|
|
/// # At compiletime
|
|
/// **Note: Alignment at compiletime is experimental and subject to change. See the
|
|
/// [tracking issue] for details.**
|
|
///
|
|
/// At compiletime, the compiler may not know where a value will end up in memory.
|
|
/// Calling this function on a pointer created from a reference at compiletime will only
|
|
/// return `true` if the pointer is guaranteed to be aligned. This means that the pointer
|
|
/// cannot be stricter aligned than the reference's underlying allocation.
|
|
///
|
|
/// ```
|
|
/// #![feature(pointer_is_aligned_to)]
|
|
/// #![feature(const_pointer_is_aligned)]
|
|
///
|
|
/// // On some platforms, the alignment of i32 is less than 4.
|
|
/// #[repr(align(4))]
|
|
/// struct AlignedI32(i32);
|
|
///
|
|
/// const _: () = {
|
|
/// 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));
|
|
///
|
|
/// // At compiletime, we know for sure that the pointer isn't aligned to 8.
|
|
/// assert!(!ptr.is_aligned_to(8));
|
|
/// assert!(!ptr.wrapping_add(1).is_aligned_to(8));
|
|
/// };
|
|
/// ```
|
|
///
|
|
/// Due to this behavior, it is possible that a runtime pointer derived from a compiletime
|
|
/// pointer is aligned, even if the compiletime pointer wasn't aligned.
|
|
///
|
|
/// ```
|
|
/// #![feature(pointer_is_aligned_to)]
|
|
/// #![feature(const_pointer_is_aligned)]
|
|
///
|
|
/// // On some platforms, the alignment of i32 is less than 4.
|
|
/// #[repr(align(4))]
|
|
/// struct AlignedI32(i32);
|
|
///
|
|
/// // At compiletime, neither `COMPTIME_PTR` nor `COMPTIME_PTR + 1` is aligned.
|
|
/// const COMPTIME_PTR: *const AlignedI32 = &AlignedI32(42);
|
|
/// const _: () = assert!(!COMPTIME_PTR.is_aligned_to(8));
|
|
/// const _: () = assert!(!COMPTIME_PTR.wrapping_add(1).is_aligned_to(8));
|
|
///
|
|
/// // At runtime, either `runtime_ptr` or `runtime_ptr + 1` is aligned.
|
|
/// let runtime_ptr = COMPTIME_PTR;
|
|
/// assert_ne!(
|
|
/// runtime_ptr.is_aligned_to(8),
|
|
/// runtime_ptr.wrapping_add(1).is_aligned_to(8),
|
|
/// );
|
|
/// ```
|
|
///
|
|
/// If a pointer is created from a fixed address, this function behaves the same during
|
|
/// runtime and compiletime.
|
|
///
|
|
/// ```
|
|
/// #![feature(pointer_is_aligned_to)]
|
|
/// #![feature(const_pointer_is_aligned)]
|
|
///
|
|
/// const _: () = {
|
|
/// let ptr = 40 as *const u8;
|
|
/// assert!(ptr.is_aligned_to(1));
|
|
/// assert!(ptr.is_aligned_to(2));
|
|
/// assert!(ptr.is_aligned_to(4));
|
|
/// assert!(ptr.is_aligned_to(8));
|
|
/// assert!(!ptr.is_aligned_to(16));
|
|
/// };
|
|
/// ```
|
|
///
|
|
/// [tracking issue]: https://github.com/rust-lang/rust/issues/104203
|
|
#[inline]
|
|
#[must_use]
|
|
#[unstable(feature = "pointer_is_aligned_to", issue = "96284")]
|
|
#[rustc_const_unstable(feature = "const_pointer_is_aligned", issue = "104203")]
|
|
pub const fn is_aligned_to(self, align: usize) -> bool {
|
|
self.pointer.is_aligned_to(align)
|
|
}
|
|
}
|
|
|
|
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_unstable(feature = "const_slice_from_raw_parts_mut", issue = "67456")]
|
|
#[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")]
|
|
#[rustc_const_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_const_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() * mem::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 allocated object!
|
|
/// Slices can never span across multiple allocated objects.
|
|
///
|
|
/// * 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() * mem::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")]
|
|
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
|
|
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() * mem::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 allocated object!
|
|
/// Slices can never span across multiple allocated objects.
|
|
///
|
|
/// * 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() * mem::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() };
|
|
/// # Ok::<_, std::alloc::AllocError>(())
|
|
/// ```
|
|
#[inline]
|
|
#[must_use]
|
|
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
|
|
#[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
|
|
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")]
|
|
#[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 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: ?Sized> Clone for NonNull<T> {
|
|
#[inline(always)]
|
|
fn clone(&self) -> Self {
|
|
*self
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: ?Sized> Copy for NonNull<T> {}
|
|
|
|
#[unstable(feature = "coerce_unsized", issue = "18598")]
|
|
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]
|
|
#[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: ?Sized> 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: ?Sized> 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: ?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 {
|
|
unique.as_non_null_ptr()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "nonnull", since = "1.25.0")]
|
|
impl<T: ?Sized> 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(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> {
|
|
/// Converts a `&T` to a `NonNull<T>`.
|
|
///
|
|
/// This conversion is safe and infallible since references cannot be null.
|
|
#[inline]
|
|
fn from(reference: &T) -> Self {
|
|
// SAFETY: A reference cannot be null.
|
|
unsafe { NonNull { pointer: reference as *const T } }
|
|
}
|
|
}
|