1400 lines
56 KiB
Rust
1400 lines
56 KiB
Rust
use super::*;
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use crate::cmp::Ordering::{self, Equal, Greater, Less};
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use crate::intrinsics;
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use crate::slice::{self, SliceIndex};
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#[lang = "mut_ptr"]
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impl<T: ?Sized> *mut T {
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/// Returns `true` if the pointer is null.
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///
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/// Note that unsized types have many possible null pointers, as only the
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/// raw data pointer is considered, not their length, vtable, etc.
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/// Therefore, two pointers that are null may still not compare equal to
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/// each other.
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///
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/// ## Behavior during const evaluation
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///
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/// When this function is used during const evaluation, it may return `false` for pointers
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/// that turn out to be null at runtime. Specifically, when a pointer to some memory
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/// is offset beyond its bounds in such a way that the resulting pointer is null,
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/// the function will still return `false`. There is no way for CTFE to know
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/// the absolute position of that memory, so we cannot tell if the pointer is
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/// null or not.
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let mut s = [1, 2, 3];
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/// let ptr: *mut u32 = s.as_mut_ptr();
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/// assert!(!ptr.is_null());
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[rustc_const_unstable(feature = "const_ptr_is_null", issue = "74939")]
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#[inline]
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pub const fn is_null(self) -> bool {
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// Compare via a cast to a thin pointer, so fat pointers are only
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// considering their "data" part for null-ness.
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(self as *mut u8).guaranteed_eq(null_mut())
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}
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/// Casts to a pointer of another type.
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#[stable(feature = "ptr_cast", since = "1.38.0")]
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#[rustc_const_stable(feature = "const_ptr_cast", since = "1.38.0")]
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#[inline]
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pub const fn cast<U>(self) -> *mut U {
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self as _
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}
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/// Decompose a (possibly wide) pointer into is address and metadata components.
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///
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/// The pointer can be later reconstructed with [`from_raw_parts_mut`].
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#[cfg(not(bootstrap))]
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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 to_raw_parts(self) -> (*mut (), <T as super::Pointee>::Metadata) {
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(self.cast(), super::metadata(self))
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}
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/// Returns `None` if the pointer is null, or else returns a shared reference to
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/// the value wrapped in `Some`. 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`]: #method.as_uninit_ref-1
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/// [`as_mut`]: #method.as_mut
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///
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/// # Safety
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///
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/// When calling this method, you have to ensure that *either* the pointer is NULL *or*
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/// all of the following is true:
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///
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/// * The pointer must be properly aligned.
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///
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/// * It must be "dereferencable" in the sense defined in [the module documentation].
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///
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/// * The pointer must point to an initialized instance of `T`.
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///
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/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
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/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
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/// In particular, for the duration of this lifetime, the memory the pointer points to must
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/// not get mutated (except inside `UnsafeCell`).
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///
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/// This applies even if the result of this method is unused!
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/// (The part about being initialized is not yet fully decided, but until
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/// it is, the only safe approach is to ensure that they are indeed initialized.)
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///
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/// [the module documentation]: crate::ptr#safety
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let ptr: *mut u8 = &mut 10u8 as *mut u8;
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///
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/// unsafe {
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/// if let Some(val_back) = ptr.as_ref() {
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/// println!("We got back the value: {}!", val_back);
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/// }
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/// }
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/// ```
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///
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/// # Null-unchecked version
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///
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/// If you are sure the pointer can never be null and are looking for some kind of
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/// `as_ref_unchecked` that returns the `&T` instead of `Option<&T>`, know that you can
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/// dereference the pointer directly.
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///
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/// ```
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/// let ptr: *mut u8 = &mut 10u8 as *mut u8;
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///
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/// unsafe {
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/// let val_back = &*ptr;
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/// println!("We got back the value: {}!", val_back);
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/// }
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/// ```
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#[stable(feature = "ptr_as_ref", since = "1.9.0")]
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#[inline]
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pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
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// SAFETY: the caller must guarantee that `self` is valid for a
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// reference if it isn't null.
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if self.is_null() { None } else { unsafe { Some(&*self) } }
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}
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/// Returns `None` if the pointer is null, or else returns a shared reference to
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/// the value wrapped in `Some`. 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`]: #method.as_ref-1
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/// [`as_uninit_mut`]: #method.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 *either* the pointer is NULL *or*
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/// all of the following is true:
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///
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/// * The pointer must be properly aligned.
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///
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/// * It must be "dereferencable" in the sense defined in [the module documentation].
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///
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/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
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/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
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/// In particular, for the duration of this lifetime, the memory the pointer points to must
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/// not get mutated (except inside `UnsafeCell`).
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///
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/// This applies even if the result of this method is unused!
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///
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/// [the module documentation]: crate::ptr#safety
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// #![feature(ptr_as_uninit)]
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///
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/// let ptr: *mut u8 = &mut 10u8 as *mut u8;
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///
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/// unsafe {
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/// if let Some(val_back) = ptr.as_uninit_ref() {
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/// println!("We got back the value: {}!", val_back.assume_init());
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/// }
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/// }
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/// ```
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#[inline]
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#[unstable(feature = "ptr_as_uninit", issue = "75402")]
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pub unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>>
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where
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T: Sized,
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{
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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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if self.is_null() { None } else { Some(unsafe { &*(self as *const MaybeUninit<T>) }) }
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}
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/// Calculates the offset from a pointer.
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///
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/// `count` is in units of T; e.g., a `count` of 3 represents a pointer
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/// offset of `3 * size_of::<T>()` bytes.
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///
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/// # Safety
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///
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/// If any of the following conditions are violated, the result is Undefined
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/// Behavior:
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///
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/// * Both the starting and resulting pointer must be either in bounds or one
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/// byte past the end of the same allocated object. Note that in Rust,
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/// every (stack-allocated) variable is considered a separate allocated object.
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///
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/// * The computed offset, **in bytes**, cannot overflow an `isize`.
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///
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/// * The offset being in bounds cannot rely on "wrapping around" the address
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/// space. That is, the infinite-precision sum, **in bytes** must fit in a usize.
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///
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/// The compiler and standard library generally tries to ensure allocations
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/// never reach a size where an offset is a concern. For instance, `Vec`
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/// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
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/// `vec.as_ptr().add(vec.len())` is always safe.
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///
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/// Most platforms fundamentally can't even construct such an allocation.
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/// For instance, no known 64-bit platform can ever serve a request
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/// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
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/// However, some 32-bit and 16-bit platforms may successfully serve a request for
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/// more than `isize::MAX` bytes with things like Physical Address
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/// Extension. As such, memory acquired directly from allocators or memory
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/// mapped files *may* be too large to handle with this function.
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///
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/// Consider using [`wrapping_offset`] instead if these constraints are
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/// difficult to satisfy. The only advantage of this method is that it
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/// enables more aggressive compiler optimizations.
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///
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/// [`wrapping_offset`]: #method.wrapping_offset
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let mut s = [1, 2, 3];
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/// let ptr: *mut u32 = s.as_mut_ptr();
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///
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/// unsafe {
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/// println!("{}", *ptr.offset(1));
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/// println!("{}", *ptr.offset(2));
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/// }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[must_use = "returns a new pointer rather than modifying its argument"]
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#[rustc_const_unstable(feature = "const_ptr_offset", issue = "71499")]
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#[inline]
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pub const unsafe fn offset(self, count: isize) -> *mut T
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where
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T: Sized,
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{
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// SAFETY: the caller must uphold the safety contract for `offset`.
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// The obtained pointer is valid for writes since the caller must
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// guarantee that it points to the same allocated object as `self`.
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unsafe { intrinsics::offset(self, count) as *mut T }
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}
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/// Calculates the offset from a pointer using wrapping arithmetic.
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/// `count` is in units of T; e.g., a `count` of 3 represents a pointer
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/// offset of `3 * size_of::<T>()` bytes.
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///
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/// # Safety
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///
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/// This operation itself is always safe, but using the resulting pointer is not.
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///
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/// The resulting pointer remains attached to the same allocated object that `self` points to.
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/// It may *not* be used to access a different allocated object. Note that in Rust, every
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/// (stack-allocated) variable is considered a separate allocated object.
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///
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/// In other words, `let z = x.wrapping_offset((y as isize) - (x as isize))` does *not* make `z`
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/// the same as `y` even if we assume `T` has size `1` and there is no overflow: `z` is still
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/// attached to the object `x` is attached to, and dereferencing it is Undefined Behavior unless
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/// `x` and `y` point into the same allocated object.
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///
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/// Compared to [`offset`], this method basically delays the requirement of staying within the
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/// same allocated object: [`offset`] is immediate Undefined Behavior when crossing object
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/// boundaries; `wrapping_offset` produces a pointer but still leads to Undefined Behavior if a
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/// pointer is dereferenced when it is out-of-bounds of the object it is attached to. [`offset`]
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/// can be optimized better and is thus preferable in performance-sensitive code.
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///
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/// The delayed check only considers the value of the pointer that was dereferenced, not the
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/// intermediate values used during the computation of the final result. For example,
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/// `x.wrapping_offset(o).wrapping_offset(o.wrapping_neg())` is always the same as `x`. In other
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/// words, leaving the allocated object and then re-entering it later is permitted.
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///
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/// If you need to cross object boundaries, cast the pointer to an integer and
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/// do the arithmetic there.
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///
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/// [`offset`]: #method.offset
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// // Iterate using a raw pointer in increments of two elements
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/// let mut data = [1u8, 2, 3, 4, 5];
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/// let mut ptr: *mut u8 = data.as_mut_ptr();
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/// let step = 2;
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/// let end_rounded_up = ptr.wrapping_offset(6);
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///
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/// while ptr != end_rounded_up {
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/// unsafe {
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/// *ptr = 0;
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/// }
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/// ptr = ptr.wrapping_offset(step);
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/// }
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/// assert_eq!(&data, &[0, 2, 0, 4, 0]);
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/// ```
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#[stable(feature = "ptr_wrapping_offset", since = "1.16.0")]
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#[must_use = "returns a new pointer rather than modifying its argument"]
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#[rustc_const_unstable(feature = "const_ptr_offset", issue = "71499")]
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#[inline]
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pub const fn wrapping_offset(self, count: isize) -> *mut T
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where
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T: Sized,
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{
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// SAFETY: the `arith_offset` intrinsic has no prerequisites to be called.
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unsafe { intrinsics::arith_offset(self, count) as *mut T }
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}
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/// Returns `None` if the pointer is null, or else returns a unique reference to
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/// the value wrapped in `Some`. If the value may be uninitialized, [`as_uninit_mut`]
|
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/// must be used instead.
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///
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/// For the shared counterpart see [`as_ref`].
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///
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/// [`as_uninit_mut`]: #method.as_uninit_mut
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/// [`as_ref`]: #method.as_ref-1
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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 *either* the pointer is NULL *or*
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/// all of the following is true:
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///
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/// * The pointer must be properly aligned.
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///
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/// * It must be "dereferencable" in the sense defined in [the module documentation].
|
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///
|
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/// * The pointer must point to an initialized instance of `T`.
|
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///
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/// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
|
|
/// arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
|
|
/// In particular, for the duration of this lifetime, 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.)
|
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///
|
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/// [the module documentation]: crate::ptr#safety
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|
///
|
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// let mut s = [1, 2, 3];
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/// let ptr: *mut u32 = s.as_mut_ptr();
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/// let first_value = unsafe { ptr.as_mut().unwrap() };
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/// *first_value = 4;
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/// # assert_eq!(s, [4, 2, 3]);
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/// println!("{:?}", s); // It'll print: "[4, 2, 3]".
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/// ```
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///
|
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/// # Null-unchecked version
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|
///
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/// If you are sure the pointer can never be null and are looking for some kind of
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|
/// `as_mut_unchecked` that returns the `&mut T` instead of `Option<&mut T>`, know that
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/// you can dereference the pointer directly.
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|
///
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/// ```
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/// let mut s = [1, 2, 3];
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/// let ptr: *mut u32 = s.as_mut_ptr();
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/// let first_value = unsafe { &mut *ptr };
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/// *first_value = 4;
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/// # assert_eq!(s, [4, 2, 3]);
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/// println!("{:?}", s); // It'll print: "[4, 2, 3]".
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/// ```
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#[stable(feature = "ptr_as_ref", since = "1.9.0")]
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#[inline]
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pub unsafe fn as_mut<'a>(self) -> Option<&'a mut T> {
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// SAFETY: the caller must guarantee that `self` is be valid for
|
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// a mutable reference if it isn't null.
|
|
if self.is_null() { None } else { unsafe { Some(&mut *self) } }
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|
}
|
|
|
|
/// Returns `None` if the pointer is null, or else returns a unique reference to
|
|
/// the value wrapped in `Some`. In contrast to [`as_mut`], this does not require
|
|
/// that the value has to be initialized.
|
|
///
|
|
/// For the shared counterpart see [`as_uninit_ref`].
|
|
///
|
|
/// [`as_mut`]: #method.as_mut
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|
/// [`as_uninit_ref`]: #method.as_uninit_ref-1
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|
///
|
|
/// # Safety
|
|
///
|
|
/// When calling this method, you have to ensure that *either* the pointer is NULL *or*
|
|
/// all of the following is true:
|
|
///
|
|
/// * The pointer must be properly aligned.
|
|
///
|
|
/// * It must be "dereferencable" in the sense defined in [the module documentation].
|
|
///
|
|
/// * 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, for the duration of this lifetime, 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 module documentation]: crate::ptr#safety
|
|
#[inline]
|
|
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
|
|
pub unsafe fn as_uninit_mut<'a>(self) -> Option<&'a mut MaybeUninit<T>>
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must guarantee that `self` meets all the
|
|
// requirements for a reference.
|
|
if self.is_null() { None } else { Some(unsafe { &mut *(self as *mut MaybeUninit<T>) }) }
|
|
}
|
|
|
|
/// Returns whether two pointers are guaranteed to be equal.
|
|
///
|
|
/// At runtime this function behaves like `self == other`.
|
|
/// However, in some contexts (e.g., compile-time evaluation),
|
|
/// it is not always possible to determine equality of two pointers, so this function may
|
|
/// spuriously return `false` for pointers that later actually turn out to be equal.
|
|
/// But when it returns `true`, the pointers are guaranteed to be equal.
|
|
///
|
|
/// This function is the mirror of [`guaranteed_ne`], but not its inverse. There are pointer
|
|
/// comparisons for which both functions return `false`.
|
|
///
|
|
/// [`guaranteed_ne`]: #method.guaranteed_ne
|
|
///
|
|
/// The return value may change depending on the compiler version and unsafe code may not
|
|
/// rely on the result of this function for soundness. It is suggested to only use this function
|
|
/// for performance optimizations where spurious `false` return values by this function do not
|
|
/// affect the outcome, but just the performance.
|
|
/// The consequences of using this method to make runtime and compile-time code behave
|
|
/// differently have not been explored. This method should not be used to introduce such
|
|
/// differences, and it should also not be stabilized before we have a better understanding
|
|
/// of this issue.
|
|
#[unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
|
|
#[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
|
|
#[inline]
|
|
pub const fn guaranteed_eq(self, other: *mut T) -> bool
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|
where
|
|
T: Sized,
|
|
{
|
|
intrinsics::ptr_guaranteed_eq(self as *const _, other as *const _)
|
|
}
|
|
|
|
/// Returns whether two pointers are guaranteed to be unequal.
|
|
///
|
|
/// At runtime this function behaves like `self != other`.
|
|
/// However, in some contexts (e.g., compile-time evaluation),
|
|
/// it is not always possible to determine the inequality of two pointers, so this function may
|
|
/// spuriously return `false` for pointers that later actually turn out to be unequal.
|
|
/// But when it returns `true`, the pointers are guaranteed to be unequal.
|
|
///
|
|
/// This function is the mirror of [`guaranteed_eq`], but not its inverse. There are pointer
|
|
/// comparisons for which both functions return `false`.
|
|
///
|
|
/// [`guaranteed_eq`]: #method.guaranteed_eq
|
|
///
|
|
/// The return value may change depending on the compiler version and unsafe code may not
|
|
/// rely on the result of this function for soundness. It is suggested to only use this function
|
|
/// for performance optimizations where spurious `false` return values by this function do not
|
|
/// affect the outcome, but just the performance.
|
|
/// The consequences of using this method to make runtime and compile-time code behave
|
|
/// differently have not been explored. This method should not be used to introduce such
|
|
/// differences, and it should also not be stabilized before we have a better understanding
|
|
/// of this issue.
|
|
#[unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
|
|
#[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
|
|
#[inline]
|
|
pub const unsafe fn guaranteed_ne(self, other: *mut T) -> bool
|
|
where
|
|
T: Sized,
|
|
{
|
|
intrinsics::ptr_guaranteed_ne(self as *const _, other as *const _)
|
|
}
|
|
|
|
/// Calculates the distance between two pointers. The returned value is in
|
|
/// units of T: the distance in bytes is divided by `mem::size_of::<T>()`.
|
|
///
|
|
/// This function is the inverse of [`offset`].
|
|
///
|
|
/// [`offset`]: #method.offset-1
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// If any of the following conditions are violated, the result is Undefined
|
|
/// Behavior:
|
|
///
|
|
/// * Both the starting and other pointer must be either in bounds or one
|
|
/// byte past the end of the same allocated object. Note that in Rust,
|
|
/// every (stack-allocated) variable is considered a separate 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.)
|
|
///
|
|
/// [`add`]: #method.add
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// This function panics if `T` is a Zero-Sized Type ("ZST").
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let mut a = [0; 5];
|
|
/// let ptr1: *mut i32 = &mut a[1];
|
|
/// let ptr2: *mut i32 = &mut 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
|
|
/// let ptr1 = Box::into_raw(Box::new(0u8));
|
|
/// let ptr2 = Box::into_raw(Box::new(1u8));
|
|
/// let diff = (ptr2 as isize).wrapping_sub(ptr1 as isize);
|
|
/// // Make ptr2_other an "alias" of ptr2, but derived from ptr1.
|
|
/// let ptr2_other = (ptr1 as *mut u8).wrapping_offset(diff);
|
|
/// assert_eq!(ptr2 as usize, ptr2_other as usize);
|
|
/// // 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!
|
|
/// unsafe {
|
|
/// let zero = ptr2_other.offset_from(ptr2); // Undefined Behavior
|
|
/// }
|
|
/// ```
|
|
#[stable(feature = "ptr_offset_from", since = "1.47.0")]
|
|
#[rustc_const_unstable(feature = "const_ptr_offset_from", issue = "41079")]
|
|
#[inline]
|
|
pub const unsafe fn offset_from(self, origin: *const T) -> isize
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `offset_from`.
|
|
unsafe { (self as *const T).offset_from(origin) }
|
|
}
|
|
|
|
/// 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. Note that in Rust,
|
|
/// every (stack-allocated) variable is considered a separate 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.
|
|
///
|
|
/// Consider using [`wrapping_add`] instead if these constraints are
|
|
/// difficult to satisfy. The only advantage of this method is that it
|
|
/// enables more aggressive compiler optimizations.
|
|
///
|
|
/// [`wrapping_add`]: #method.wrapping_add
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let s: &str = "123";
|
|
/// let ptr: *const u8 = s.as_ptr();
|
|
///
|
|
/// unsafe {
|
|
/// println!("{}", *ptr.add(1) as char);
|
|
/// println!("{}", *ptr.add(2) as char);
|
|
/// }
|
|
/// ```
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[must_use = "returns a new pointer rather than modifying its argument"]
|
|
#[rustc_const_unstable(feature = "const_ptr_offset", issue = "71499")]
|
|
#[inline]
|
|
pub const unsafe fn add(self, count: usize) -> Self
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `offset`.
|
|
unsafe { self.offset(count as isize) }
|
|
}
|
|
|
|
/// 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. Note that in Rust,
|
|
/// every (stack-allocated) variable is considered a separate 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.
|
|
///
|
|
/// Consider using [`wrapping_sub`] instead if these constraints are
|
|
/// difficult to satisfy. The only advantage of this method is that it
|
|
/// enables more aggressive compiler optimizations.
|
|
///
|
|
/// [`wrapping_sub`]: #method.wrapping_sub
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// let s: &str = "123";
|
|
///
|
|
/// unsafe {
|
|
/// let end: *const u8 = s.as_ptr().add(3);
|
|
/// println!("{}", *end.sub(1) as char);
|
|
/// println!("{}", *end.sub(2) as char);
|
|
/// }
|
|
/// ```
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[must_use = "returns a new pointer rather than modifying its argument"]
|
|
#[rustc_const_unstable(feature = "const_ptr_offset", issue = "71499")]
|
|
#[inline]
|
|
pub const unsafe fn sub(self, count: usize) -> Self
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `offset`.
|
|
unsafe { self.offset((count as isize).wrapping_neg()) }
|
|
}
|
|
|
|
/// Calculates the offset from a pointer using wrapping arithmetic.
|
|
/// (convenience for `.wrapping_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
|
|
///
|
|
/// This operation itself is always safe, but using the resulting pointer is not.
|
|
///
|
|
/// The resulting pointer remains attached to the same allocated object that `self` points to.
|
|
/// It may *not* be used to access a different allocated object. Note that in Rust, every
|
|
/// (stack-allocated) variable is considered a separate allocated object.
|
|
///
|
|
/// In other words, `let z = x.wrapping_add((y as usize) - (x as usize))` does *not* make `z`
|
|
/// the same as `y` even if we assume `T` has size `1` and there is no overflow: `z` is still
|
|
/// attached to the object `x` is attached to, and dereferencing it is Undefined Behavior unless
|
|
/// `x` and `y` point into the same allocated object.
|
|
///
|
|
/// Compared to [`add`], this method basically delays the requirement of staying within the
|
|
/// same allocated object: [`add`] is immediate Undefined Behavior when crossing object
|
|
/// boundaries; `wrapping_add` produces a pointer but still leads to Undefined Behavior if a
|
|
/// pointer is dereferenced when it is out-of-bounds of the object it is attached to. [`add`]
|
|
/// can be optimized better and is thus preferable in performance-sensitive code.
|
|
///
|
|
/// The delayed check only considers the value of the pointer that was dereferenced, not the
|
|
/// intermediate values used during the computation of the final result. For example,
|
|
/// `x.wrapping_add(o).wrapping_sub(o)` is always the same as `x`. In other words, leaving the
|
|
/// allocated object and then re-entering it later is permitted.
|
|
///
|
|
/// If you need to cross object boundaries, cast the pointer to an integer and
|
|
/// do the arithmetic there.
|
|
///
|
|
/// [`add`]: #method.add
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// // Iterate using a raw pointer in increments of two elements
|
|
/// let data = [1u8, 2, 3, 4, 5];
|
|
/// let mut ptr: *const u8 = data.as_ptr();
|
|
/// let step = 2;
|
|
/// let end_rounded_up = ptr.wrapping_add(6);
|
|
///
|
|
/// // This loop prints "1, 3, 5, "
|
|
/// while ptr != end_rounded_up {
|
|
/// unsafe {
|
|
/// print!("{}, ", *ptr);
|
|
/// }
|
|
/// ptr = ptr.wrapping_add(step);
|
|
/// }
|
|
/// ```
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[must_use = "returns a new pointer rather than modifying its argument"]
|
|
#[rustc_const_unstable(feature = "const_ptr_offset", issue = "71499")]
|
|
#[inline]
|
|
pub const fn wrapping_add(self, count: usize) -> Self
|
|
where
|
|
T: Sized,
|
|
{
|
|
self.wrapping_offset(count as isize)
|
|
}
|
|
|
|
/// Calculates the offset from a pointer using wrapping arithmetic.
|
|
/// (convenience for `.wrapping_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
|
|
///
|
|
/// This operation itself is always safe, but using the resulting pointer is not.
|
|
///
|
|
/// The resulting pointer remains attached to the same allocated object that `self` points to.
|
|
/// It may *not* be used to access a different allocated object. Note that in Rust, every
|
|
/// (stack-allocated) variable is considered a separate allocated object.
|
|
///
|
|
/// In other words, `let z = x.wrapping_sub((x as usize) - (y as usize))` does *not* make `z`
|
|
/// the same as `y` even if we assume `T` has size `1` and there is no overflow: `z` is still
|
|
/// attached to the object `x` is attached to, and dereferencing it is Undefined Behavior unless
|
|
/// `x` and `y` point into the same allocated object.
|
|
///
|
|
/// Compared to [`sub`], this method basically delays the requirement of staying within the
|
|
/// same allocated object: [`sub`] is immediate Undefined Behavior when crossing object
|
|
/// boundaries; `wrapping_sub` produces a pointer but still leads to Undefined Behavior if a
|
|
/// pointer is dereferenced when it is out-of-bounds of the object it is attached to. [`sub`]
|
|
/// can be optimized better and is thus preferable in performance-sensitive code.
|
|
///
|
|
/// The delayed check only considers the value of the pointer that was dereferenced, not the
|
|
/// intermediate values used during the computation of the final result. For example,
|
|
/// `x.wrapping_add(o).wrapping_sub(o)` is always the same as `x`. In other words, leaving the
|
|
/// allocated object and then re-entering it later is permitted.
|
|
///
|
|
/// If you need to cross object boundaries, cast the pointer to an integer and
|
|
/// do the arithmetic there.
|
|
///
|
|
/// [`sub`]: #method.sub
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// // Iterate using a raw pointer in increments of two elements (backwards)
|
|
/// let data = [1u8, 2, 3, 4, 5];
|
|
/// let mut ptr: *const u8 = data.as_ptr();
|
|
/// let start_rounded_down = ptr.wrapping_sub(2);
|
|
/// ptr = ptr.wrapping_add(4);
|
|
/// let step = 2;
|
|
/// // This loop prints "5, 3, 1, "
|
|
/// while ptr != start_rounded_down {
|
|
/// unsafe {
|
|
/// print!("{}, ", *ptr);
|
|
/// }
|
|
/// ptr = ptr.wrapping_sub(step);
|
|
/// }
|
|
/// ```
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[must_use = "returns a new pointer rather than modifying its argument"]
|
|
#[rustc_const_unstable(feature = "const_ptr_offset", issue = "71499")]
|
|
#[inline]
|
|
pub const fn wrapping_sub(self, count: usize) -> Self
|
|
where
|
|
T: Sized,
|
|
{
|
|
self.wrapping_offset((count as isize).wrapping_neg())
|
|
}
|
|
|
|
/// Sets the pointer value to `ptr`.
|
|
///
|
|
/// In case `self` is a (fat) pointer to an unsized type, this operation
|
|
/// will only affect the pointer part, whereas for (thin) pointers to
|
|
/// sized types, this has the same effect as a simple assignment.
|
|
///
|
|
/// The resulting pointer will have provenance of `val`, i.e., for a fat
|
|
/// pointer, this operation is semantically the same as creating a new
|
|
/// fat pointer with the data pointer value of `val` but the metadata of
|
|
/// `self`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// This function is primarily useful for allowing byte-wise pointer
|
|
/// arithmetic on potentially fat pointers:
|
|
///
|
|
/// ```
|
|
/// #![feature(set_ptr_value)]
|
|
/// # use core::fmt::Debug;
|
|
/// let mut arr: [i32; 3] = [1, 2, 3];
|
|
/// let mut ptr = &mut arr[0] as *mut dyn Debug;
|
|
/// let thin = ptr as *mut u8;
|
|
/// unsafe {
|
|
/// ptr = ptr.set_ptr_value(thin.add(8));
|
|
/// # assert_eq!(*(ptr as *mut i32), 3);
|
|
/// println!("{:?}", &*ptr); // will print "3"
|
|
/// }
|
|
/// ```
|
|
#[unstable(feature = "set_ptr_value", issue = "75091")]
|
|
#[must_use = "returns a new pointer rather than modifying its argument"]
|
|
#[inline]
|
|
pub fn set_ptr_value(mut self, val: *mut u8) -> Self {
|
|
let thin = &mut self as *mut *mut T as *mut *mut u8;
|
|
// SAFETY: In case of a thin pointer, this operations is identical
|
|
// to a simple assignment. In case of a fat pointer, with the current
|
|
// fat pointer layout implementation, the first field of such a
|
|
// pointer is always the data pointer, which is likewise assigned.
|
|
unsafe { *thin = val };
|
|
self
|
|
}
|
|
|
|
/// 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()
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[rustc_const_unstable(feature = "const_ptr_read", issue = "80377")]
|
|
#[inline]
|
|
pub const unsafe fn read(self) -> T
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for ``.
|
|
unsafe { read(self) }
|
|
}
|
|
|
|
/// 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()
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub unsafe fn read_volatile(self) -> T
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `read_volatile`.
|
|
unsafe { read_volatile(self) }
|
|
}
|
|
|
|
/// 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()
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[rustc_const_unstable(feature = "const_ptr_read", issue = "80377")]
|
|
#[inline]
|
|
pub const unsafe fn read_unaligned(self) -> T
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `read_unaligned`.
|
|
unsafe { read_unaligned(self) }
|
|
}
|
|
|
|
/// 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()
|
|
#[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub const unsafe fn copy_to(self, dest: *mut T, count: usize)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `copy`.
|
|
unsafe { copy(self, dest, 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()
|
|
#[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub const unsafe fn copy_to_nonoverlapping(self, dest: *mut T, count: usize)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `copy_nonoverlapping`.
|
|
unsafe { copy_nonoverlapping(self, dest, 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()
|
|
#[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub const unsafe fn copy_from(self, src: *const T, count: usize)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `copy`.
|
|
unsafe { copy(src, self, 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()
|
|
#[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub const unsafe fn copy_from_nonoverlapping(self, src: *const T, count: usize)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `copy_nonoverlapping`.
|
|
unsafe { copy_nonoverlapping(src, self, 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()
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub unsafe fn drop_in_place(self) {
|
|
// SAFETY: the caller must uphold the safety contract for `drop_in_place`.
|
|
unsafe { drop_in_place(self) }
|
|
}
|
|
|
|
/// 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()
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub unsafe fn write(self, val: T)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `write`.
|
|
unsafe { write(self, 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()
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub unsafe fn write_bytes(self, val: u8, count: usize)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `write_bytes`.
|
|
unsafe { write_bytes(self, 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()
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub unsafe fn write_volatile(self, val: T)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `write_volatile`.
|
|
unsafe { write_volatile(self, 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()
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[rustc_const_unstable(feature = "const_ptr_write", issue = "none")]
|
|
#[inline]
|
|
pub const unsafe fn write_unaligned(self, val: T)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `write_unaligned`.
|
|
unsafe { write_unaligned(self, 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()
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub unsafe fn replace(self, src: T) -> T
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `replace`.
|
|
unsafe { replace(self, 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()
|
|
#[stable(feature = "pointer_methods", since = "1.26.0")]
|
|
#[inline]
|
|
pub unsafe fn swap(self, with: *mut T)
|
|
where
|
|
T: Sized,
|
|
{
|
|
// SAFETY: the caller must uphold the safety contract for `swap`.
|
|
unsafe { swap(self, with) }
|
|
}
|
|
|
|
/// 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. The value returned can be
|
|
/// used with the `wrapping_add` method.
|
|
///
|
|
/// 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`
|
|
///
|
|
/// ```
|
|
/// # fn foo(n: usize) {
|
|
/// # use std::mem::align_of;
|
|
/// # unsafe {
|
|
/// let x = [5u8, 6u8, 7u8, 8u8, 9u8];
|
|
/// let ptr = x.as_ptr().add(n) as *const u8;
|
|
/// let offset = ptr.align_offset(align_of::<u16>());
|
|
/// if offset < x.len() - n - 1 {
|
|
/// let u16_ptr = ptr.add(offset) as *const u16;
|
|
/// assert_ne!(*u16_ptr, 500);
|
|
/// } else {
|
|
/// // while the pointer can be aligned via `offset`, it would point
|
|
/// // outside the allocation
|
|
/// }
|
|
/// # } }
|
|
/// ```
|
|
#[stable(feature = "align_offset", since = "1.36.0")]
|
|
pub fn align_offset(self, align: usize) -> usize
|
|
where
|
|
T: Sized,
|
|
{
|
|
if !align.is_power_of_two() {
|
|
panic!("align_offset: align is not a power-of-two");
|
|
}
|
|
// SAFETY: `align` has been checked to be a power of 2 above
|
|
unsafe { align_offset(self, align) }
|
|
}
|
|
}
|
|
|
|
#[lang = "mut_slice_ptr"]
|
|
impl<T> *mut [T] {
|
|
/// Returns the length of a raw slice.
|
|
///
|
|
/// The returned value is the number of **elements**, not the number of bytes.
|
|
///
|
|
/// This function is safe, even when the raw slice cannot be cast to a slice
|
|
/// reference because the pointer is null or unaligned.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// #![feature(slice_ptr_len)]
|
|
/// use std::ptr;
|
|
///
|
|
/// let slice: *mut [i8] = ptr::slice_from_raw_parts_mut(ptr::null_mut(), 3);
|
|
/// assert_eq!(slice.len(), 3);
|
|
/// ```
|
|
#[inline]
|
|
#[unstable(feature = "slice_ptr_len", issue = "71146")]
|
|
#[rustc_const_unstable(feature = "const_slice_ptr_len", issue = "71146")]
|
|
pub const fn len(self) -> usize {
|
|
#[cfg(bootstrap)]
|
|
{
|
|
// SAFETY: this is safe because `*const [T]` and `FatPtr<T>` have the same layout.
|
|
// Only `std` can make this guarantee.
|
|
unsafe { Repr { rust_mut: self }.raw }.len
|
|
}
|
|
#[cfg(not(bootstrap))]
|
|
metadata(self)
|
|
}
|
|
|
|
/// Returns a raw pointer to the slice's buffer.
|
|
///
|
|
/// This is equivalent to casting `self` to `*mut T`, but more type-safe.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// #![feature(slice_ptr_get)]
|
|
/// use std::ptr;
|
|
///
|
|
/// let slice: *mut [i8] = ptr::slice_from_raw_parts_mut(ptr::null_mut(), 3);
|
|
/// assert_eq!(slice.as_mut_ptr(), 0 as *mut i8);
|
|
/// ```
|
|
#[inline]
|
|
#[unstable(feature = "slice_ptr_get", issue = "74265")]
|
|
#[rustc_const_unstable(feature = "slice_ptr_get", issue = "74265")]
|
|
pub const fn as_mut_ptr(self) -> *mut T {
|
|
self as *mut T
|
|
}
|
|
|
|
/// 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 dereferencable
|
|
/// 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)]
|
|
///
|
|
/// let x = &mut [1, 2, 4] as *mut [i32];
|
|
///
|
|
/// unsafe {
|
|
/// assert_eq!(x.get_unchecked_mut(1), x.as_mut_ptr().add(1));
|
|
/// }
|
|
/// ```
|
|
#[unstable(feature = "slice_ptr_get", issue = "74265")]
|
|
#[inline]
|
|
pub unsafe fn get_unchecked_mut<I>(self, index: I) -> *mut I::Output
|
|
where
|
|
I: SliceIndex<[T]>,
|
|
{
|
|
// SAFETY: the caller ensures that `self` is dereferencable and `index` in-bounds.
|
|
unsafe { index.get_unchecked_mut(self) }
|
|
}
|
|
|
|
/// Returns `None` if the pointer is null, or else returns a shared slice to
|
|
/// the value wrapped in `Some`. 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`]: #method.as_ref-1
|
|
/// [`as_uninit_slice_mut`]: #method.as_uninit_slice_mut
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// When calling this method, you have to ensure that *either* the pointer is NULL *or*
|
|
/// 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, for the duration of this lifetime, 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]
|
|
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
|
|
pub unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]> {
|
|
if self.is_null() {
|
|
None
|
|
} else {
|
|
// SAFETY: the caller must uphold the safety contract for `as_uninit_slice`.
|
|
Some(unsafe { slice::from_raw_parts(self as *const MaybeUninit<T>, self.len()) })
|
|
}
|
|
}
|
|
|
|
/// Returns `None` if the pointer is null, or else returns a unique slice to
|
|
/// the value wrapped in `Some`. 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`]: #method.as_mut
|
|
/// [`as_uninit_slice`]: #method.as_uninit_slice-1
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// When calling this method, you have to ensure that *either* the pointer is NULL *or*
|
|
/// 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, for the duration of this lifetime, 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
|
|
#[inline]
|
|
#[unstable(feature = "ptr_as_uninit", issue = "75402")]
|
|
pub unsafe fn as_uninit_slice_mut<'a>(self) -> Option<&'a mut [MaybeUninit<T>]> {
|
|
if self.is_null() {
|
|
None
|
|
} else {
|
|
// SAFETY: the caller must uphold the safety contract for `as_uninit_slice_mut`.
|
|
Some(unsafe { slice::from_raw_parts_mut(self as *mut MaybeUninit<T>, self.len()) })
|
|
}
|
|
}
|
|
}
|
|
|
|
// Equality for pointers
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: ?Sized> PartialEq for *mut T {
|
|
#[inline]
|
|
fn eq(&self, other: &*mut T) -> bool {
|
|
*self == *other
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: ?Sized> Eq for *mut T {}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> Ord for *mut T {
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#[inline]
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fn cmp(&self, other: &*mut T) -> Ordering {
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if self < other {
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Less
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} else if self == other {
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Equal
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} else {
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Greater
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}
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized> PartialOrd for *mut T {
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#[inline]
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fn partial_cmp(&self, other: &*mut T) -> Option<Ordering> {
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Some(self.cmp(other))
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}
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#[inline]
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fn lt(&self, other: &*mut T) -> bool {
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*self < *other
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}
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#[inline]
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fn le(&self, other: &*mut T) -> bool {
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*self <= *other
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}
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#[inline]
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fn gt(&self, other: &*mut T) -> bool {
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*self > *other
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}
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#[inline]
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fn ge(&self, other: &*mut T) -> bool {
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*self >= *other
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}
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}
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