+++ /dev/null
-// ignore-tidy-filelength
-
-//! Manually manage memory through raw pointers.
-//!
-//! *[See also the pointer primitive types](../../std/primitive.pointer.html).*
-//!
-//! # Safety
-//!
-//! Many functions in this module take raw pointers as arguments and read from
-//! or write to them. For this to be safe, these pointers must be *valid*.
-//! Whether a pointer is valid depends on the operation it is used for
-//! (read or write), and the extent of the memory that is accessed (i.e.,
-//! how many bytes are read/written). Most functions use `*mut T` and `*const T`
-//! to access only a single value, in which case the documentation omits the size
-//! and implicitly assumes it to be `size_of::<T>()` bytes.
-//!
-//! The precise rules for validity are not determined yet. The guarantees that are
-//! provided at this point are very minimal:
-//!
-//! * A [null] pointer is *never* valid, not even for accesses of [size zero][zst].
-//! * All pointers (except for the null pointer) are valid for all operations of
-//! [size zero][zst].
-//! * All accesses performed by functions in this module are *non-atomic* in the sense
-//! of [atomic operations] used to synchronize between threads. This means it is
-//! undefined behavior to perform two concurrent accesses to the same location from different
-//! threads unless both accesses only read from memory. Notice that this explicitly
-//! includes [`read_volatile`] and [`write_volatile`]: Volatile accesses cannot
-//! be used for inter-thread synchronization.
-//! * The result of casting a reference to a pointer is valid for as long as the
-//! underlying object is live and no reference (just raw pointers) is used to
-//! access the same memory.
-//!
-//! These axioms, along with careful use of [`offset`] for pointer arithmetic,
-//! are enough to correctly implement many useful things in unsafe code. Stronger guarantees
-//! will be provided eventually, as the [aliasing] rules are being determined. For more
-//! information, see the [book] as well as the section in the reference devoted
-//! to [undefined behavior][ub].
-//!
-//! ## Alignment
-//!
-//! Valid raw pointers as defined above are not necessarily properly aligned (where
-//! "proper" alignment is defined by the pointee type, i.e., `*const T` must be
-//! aligned to `mem::align_of::<T>()`). However, most functions require their
-//! arguments to be properly aligned, and will explicitly state
-//! this requirement in their documentation. Notable exceptions to this are
-//! [`read_unaligned`] and [`write_unaligned`].
-//!
-//! When a function requires proper alignment, it does so even if the access
-//! has size 0, i.e., even if memory is not actually touched. Consider using
-//! [`NonNull::dangling`] in such cases.
-//!
-//! [aliasing]: ../../nomicon/aliasing.html
-//! [book]: ../../book/ch19-01-unsafe-rust.html#dereferencing-a-raw-pointer
-//! [ub]: ../../reference/behavior-considered-undefined.html
-//! [null]: ./fn.null.html
-//! [zst]: ../../nomicon/exotic-sizes.html#zero-sized-types-zsts
-//! [atomic operations]: ../../std/sync/atomic/index.html
-//! [`copy`]: ../../std/ptr/fn.copy.html
-//! [`offset`]: ../../std/primitive.pointer.html#method.offset
-//! [`read_unaligned`]: ./fn.read_unaligned.html
-//! [`write_unaligned`]: ./fn.write_unaligned.html
-//! [`read_volatile`]: ./fn.read_volatile.html
-//! [`write_volatile`]: ./fn.write_volatile.html
-//! [`NonNull::dangling`]: ./struct.NonNull.html#method.dangling
-
-#![stable(feature = "rust1", since = "1.0.0")]
-
-use crate::convert::From;
-use crate::intrinsics;
-use crate::ops::{CoerceUnsized, DispatchFromDyn};
-use crate::fmt;
-use crate::hash;
-use crate::marker::{PhantomData, Unsize};
-use crate::mem::{self, MaybeUninit};
-
-use crate::cmp::Ordering::{self, Less, Equal, Greater};
-
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use crate::intrinsics::copy_nonoverlapping;
-
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use crate::intrinsics::copy;
-
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use crate::intrinsics::write_bytes;
-
-/// Executes the destructor (if any) of the pointed-to value.
-///
-/// This is semantically equivalent to calling [`ptr::read`] and discarding
-/// the result, but has the following advantages:
-///
-/// * It is *required* to use `drop_in_place` to drop unsized types like
-/// trait objects, because they can't be read out onto the stack and
-/// dropped normally.
-///
-/// * It is friendlier to the optimizer to do this over [`ptr::read`] when
-/// dropping manually allocated memory (e.g., when writing Box/Rc/Vec),
-/// as the compiler doesn't need to prove that it's sound to elide the
-/// copy.
-///
-/// [`ptr::read`]: ../ptr/fn.read.html
-///
-/// # Safety
-///
-/// Behavior is undefined if any of the following conditions are violated:
-///
-/// * `to_drop` must be [valid] for reads.
-///
-/// * `to_drop` must be properly aligned. See the example below for how to drop
-/// an unaligned pointer.
-///
-/// Additionally, if `T` is not [`Copy`], using the pointed-to value after
-/// calling `drop_in_place` can cause undefined behavior. Note that `*to_drop =
-/// foo` counts as a use because it will cause the value to be dropped
-/// again. [`write`] can be used to overwrite data without causing it to be
-/// dropped.
-///
-/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
-///
-/// [valid]: ../ptr/index.html#safety
-/// [`Copy`]: ../marker/trait.Copy.html
-/// [`write`]: ../ptr/fn.write.html
-///
-/// # Examples
-///
-/// Manually remove the last item from a vector:
-///
-/// ```
-/// use std::ptr;
-/// use std::rc::Rc;
-///
-/// let last = Rc::new(1);
-/// let weak = Rc::downgrade(&last);
-///
-/// let mut v = vec![Rc::new(0), last];
-///
-/// unsafe {
-/// // Get a raw pointer to the last element in `v`.
-/// let ptr = &mut v[1] as *mut _;
-/// // Shorten `v` to prevent the last item from being dropped. We do that first,
-/// // to prevent issues if the `drop_in_place` below panics.
-/// v.set_len(1);
-/// // Without a call `drop_in_place`, the last item would never be dropped,
-/// // and the memory it manages would be leaked.
-/// ptr::drop_in_place(ptr);
-/// }
-///
-/// assert_eq!(v, &[0.into()]);
-///
-/// // Ensure that the last item was dropped.
-/// assert!(weak.upgrade().is_none());
-/// ```
-///
-/// Unaligned values cannot be dropped in place, they must be copied to an aligned
-/// location first:
-/// ```
-/// use std::ptr;
-/// use std::mem::{self, MaybeUninit};
-///
-/// unsafe fn drop_after_copy<T>(to_drop: *mut T) {
-/// let mut copy: MaybeUninit<T> = MaybeUninit::uninit();
-/// ptr::copy(to_drop, copy.as_mut_ptr(), 1);
-/// drop(copy.assume_init());
-/// }
-///
-/// #[repr(packed, C)]
-/// struct Packed {
-/// _padding: u8,
-/// unaligned: Vec<i32>,
-/// }
-///
-/// let mut p = Packed { _padding: 0, unaligned: vec![42] };
-/// unsafe {
-/// drop_after_copy(&mut p.unaligned as *mut _);
-/// mem::forget(p);
-/// }
-/// ```
-///
-/// Notice that the compiler performs this copy automatically when dropping packed structs,
-/// i.e., you do not usually have to worry about such issues unless you call `drop_in_place`
-/// manually.
-#[stable(feature = "drop_in_place", since = "1.8.0")]
-#[inline(always)]
-pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
- real_drop_in_place(&mut *to_drop)
-}
-
-// The real `drop_in_place` -- the one that gets called implicitly when variables go
-// out of scope -- should have a safe reference and not a raw pointer as argument
-// type. When we drop a local variable, we access it with a pointer that behaves
-// like a safe reference; transmuting that to a raw pointer does not mean we can
-// actually access it with raw pointers.
-#[lang = "drop_in_place"]
-#[allow(unconditional_recursion)]
-unsafe fn real_drop_in_place<T: ?Sized>(to_drop: &mut T) {
- // Code here does not matter - this is replaced by the
- // real drop glue by the compiler.
- real_drop_in_place(to_drop)
-}
-
-/// Creates a null raw pointer.
-///
-/// # Examples
-///
-/// ```
-/// use std::ptr;
-///
-/// let p: *const i32 = ptr::null();
-/// assert!(p.is_null());
-/// ```
-#[inline]
-#[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_promotable]
-pub const fn null<T>() -> *const T { 0 as *const T }
-
-/// Creates a null mutable raw pointer.
-///
-/// # Examples
-///
-/// ```
-/// use std::ptr;
-///
-/// let p: *mut i32 = ptr::null_mut();
-/// assert!(p.is_null());
-/// ```
-#[inline]
-#[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_promotable]
-pub const fn null_mut<T>() -> *mut T { 0 as *mut T }
-
-/// Swaps the values at two mutable locations of the same type, without
-/// deinitializing either.
-///
-/// But for the following two exceptions, this function is semantically
-/// equivalent to [`mem::swap`]:
-///
-/// * It operates on raw pointers instead of references. When references are
-/// available, [`mem::swap`] should be preferred.
-///
-/// * The two pointed-to values may overlap. If the values do overlap, then the
-/// overlapping region of memory from `x` will be used. This is demonstrated
-/// in the second example below.
-///
-/// [`mem::swap`]: ../mem/fn.swap.html
-///
-/// # Safety
-///
-/// Behavior is undefined if any of the following conditions are violated:
-///
-/// * Both `x` and `y` must be [valid] for reads and writes.
-///
-/// * Both `x` and `y` must be properly aligned.
-///
-/// Note that even if `T` has size `0`, the pointers must be non-NULL and properly aligned.
-///
-/// [valid]: ../ptr/index.html#safety
-///
-/// # Examples
-///
-/// Swapping two non-overlapping regions:
-///
-/// ```
-/// use std::ptr;
-///
-/// let mut array = [0, 1, 2, 3];
-///
-/// let x = array[0..].as_mut_ptr() as *mut [u32; 2]; // this is `array[0..2]`
-/// let y = array[2..].as_mut_ptr() as *mut [u32; 2]; // this is `array[2..4]`
-///
-/// unsafe {
-/// ptr::swap(x, y);
-/// assert_eq!([2, 3, 0, 1], array);
-/// }
-/// ```
-///
-/// Swapping two overlapping regions:
-///
-/// ```
-/// use std::ptr;
-///
-/// let mut array = [0, 1, 2, 3];
-///
-/// let x = array[0..].as_mut_ptr() as *mut [u32; 3]; // this is `array[0..3]`
-/// let y = array[1..].as_mut_ptr() as *mut [u32; 3]; // this is `array[1..4]`
-///
-/// unsafe {
-/// ptr::swap(x, y);
-/// // The indices `1..3` of the slice overlap between `x` and `y`.
-/// // Reasonable results would be for to them be `[2, 3]`, so that indices `0..3` are
-/// // `[1, 2, 3]` (matching `y` before the `swap`); or for them to be `[0, 1]`
-/// // so that indices `1..4` are `[0, 1, 2]` (matching `x` before the `swap`).
-/// // This implementation is defined to make the latter choice.
-/// assert_eq!([1, 0, 1, 2], array);
-/// }
-/// ```
-#[inline]
-#[stable(feature = "rust1", since = "1.0.0")]
-pub unsafe fn swap<T>(x: *mut T, y: *mut T) {
- // Give ourselves some scratch space to work with.
- // We do not have to worry about drops: `MaybeUninit` does nothing when dropped.
- let mut tmp = MaybeUninit::<T>::uninit();
-
- // Perform the swap
- copy_nonoverlapping(x, tmp.as_mut_ptr(), 1);
- copy(y, x, 1); // `x` and `y` may overlap
- copy_nonoverlapping(tmp.as_ptr(), y, 1);
-}
-
-/// Swaps `count * size_of::<T>()` bytes between the two regions of memory
-/// beginning at `x` and `y`. The two regions must *not* overlap.
-///
-/// # Safety
-///
-/// Behavior is undefined if any of the following conditions are violated:
-///
-/// * Both `x` and `y` must be [valid] for reads and writes of `count *
-/// size_of::<T>()` bytes.
-///
-/// * Both `x` and `y` must be properly aligned.
-///
-/// * The region of memory beginning at `x` with a size of `count *
-/// size_of::<T>()` bytes must *not* overlap with the region of memory
-/// beginning at `y` with the same size.
-///
-/// Note that even if the effectively copied size (`count * size_of::<T>()`) is `0`,
-/// the pointers must be non-NULL and properly aligned.
-///
-/// [valid]: ../ptr/index.html#safety
-///
-/// # Examples
-///
-/// Basic usage:
-///
-/// ```
-/// use std::ptr;
-///
-/// let mut x = [1, 2, 3, 4];
-/// let mut y = [7, 8, 9];
-///
-/// unsafe {
-/// ptr::swap_nonoverlapping(x.as_mut_ptr(), y.as_mut_ptr(), 2);
-/// }
-///
-/// assert_eq!(x, [7, 8, 3, 4]);
-/// assert_eq!(y, [1, 2, 9]);
-/// ```
-#[inline]
-#[stable(feature = "swap_nonoverlapping", since = "1.27.0")]
-pub unsafe fn swap_nonoverlapping<T>(x: *mut T, y: *mut T, count: usize) {
- let x = x as *mut u8;
- let y = y as *mut u8;
- let len = mem::size_of::<T>() * count;
- swap_nonoverlapping_bytes(x, y, len)
-}
-
-#[inline]
-pub(crate) unsafe fn swap_nonoverlapping_one<T>(x: *mut T, y: *mut T) {
- // For types smaller than the block optimization below,
- // just swap directly to avoid pessimizing codegen.
- if mem::size_of::<T>() < 32 {
- let z = read(x);
- copy_nonoverlapping(y, x, 1);
- write(y, z);
- } else {
- swap_nonoverlapping(x, y, 1);
- }
-}
-
-#[inline]
-unsafe fn swap_nonoverlapping_bytes(x: *mut u8, y: *mut u8, len: usize) {
- // The approach here is to utilize simd to swap x & y efficiently. Testing reveals
- // that swapping either 32 bytes or 64 bytes at a time is most efficient for Intel
- // Haswell E processors. LLVM is more able to optimize if we give a struct a
- // #[repr(simd)], even if we don't actually use this struct directly.
- //
- // FIXME repr(simd) broken on emscripten and redox
- #[cfg_attr(not(any(target_os = "emscripten", target_os = "redox")), repr(simd))]
- struct Block(u64, u64, u64, u64);
- struct UnalignedBlock(u64, u64, u64, u64);
-
- let block_size = mem::size_of::<Block>();
-
- // Loop through x & y, copying them `Block` at a time
- // The optimizer should unroll the loop fully for most types
- // N.B. We can't use a for loop as the `range` impl calls `mem::swap` recursively
- let mut i = 0;
- while i + block_size <= len {
- // Create some uninitialized memory as scratch space
- // Declaring `t` here avoids aligning the stack when this loop is unused
- let mut t = mem::MaybeUninit::<Block>::uninit();
- let t = t.as_mut_ptr() as *mut u8;
- let x = x.add(i);
- let y = y.add(i);
-
- // Swap a block of bytes of x & y, using t as a temporary buffer
- // This should be optimized into efficient SIMD operations where available
- copy_nonoverlapping(x, t, block_size);
- copy_nonoverlapping(y, x, block_size);
- copy_nonoverlapping(t, y, block_size);
- i += block_size;
- }
-
- if i < len {
- // Swap any remaining bytes
- let mut t = mem::MaybeUninit::<UnalignedBlock>::uninit();
- let rem = len - i;
-
- let t = t.as_mut_ptr() as *mut u8;
- let x = x.add(i);
- let y = y.add(i);
-
- copy_nonoverlapping(x, t, rem);
- copy_nonoverlapping(y, x, rem);
- copy_nonoverlapping(t, y, rem);
- }
-}
-
-/// Moves `src` into the pointed `dst`, returning the previous `dst` value.
-///
-/// Neither value is dropped.
-///
-/// This function is semantically equivalent to [`mem::replace`] except that it
-/// operates on raw pointers instead of references. When references are
-/// available, [`mem::replace`] should be preferred.
-///
-/// [`mem::replace`]: ../mem/fn.replace.html
-///
-/// # Safety
-///
-/// Behavior is undefined if any of the following conditions are violated:
-///
-/// * `dst` must be [valid] for writes.
-///
-/// * `dst` must be properly aligned.
-///
-/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
-///
-/// [valid]: ../ptr/index.html#safety
-///
-/// # Examples
-///
-/// ```
-/// use std::ptr;
-///
-/// let mut rust = vec!['b', 'u', 's', 't'];
-///
-/// // `mem::replace` would have the same effect without requiring the unsafe
-/// // block.
-/// let b = unsafe {
-/// ptr::replace(&mut rust[0], 'r')
-/// };
-///
-/// assert_eq!(b, 'b');
-/// assert_eq!(rust, &['r', 'u', 's', 't']);
-/// ```
-#[inline]
-#[stable(feature = "rust1", since = "1.0.0")]
-pub unsafe fn replace<T>(dst: *mut T, mut src: T) -> T {
- mem::swap(&mut *dst, &mut src); // cannot overlap
- src
-}
-
-/// Reads the value from `src` without moving it. This leaves the
-/// memory in `src` unchanged.
-///
-/// # Safety
-///
-/// Behavior is undefined if any of the following conditions are violated:
-///
-/// * `src` must be [valid] for reads.
-///
-/// * `src` must be properly aligned. Use [`read_unaligned`] if this is not the
-/// case.
-///
-/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
-///
-/// # Examples
-///
-/// Basic usage:
-///
-/// ```
-/// let x = 12;
-/// let y = &x as *const i32;
-///
-/// unsafe {
-/// assert_eq!(std::ptr::read(y), 12);
-/// }
-/// ```
-///
-/// Manually implement [`mem::swap`]:
-///
-/// ```
-/// use std::ptr;
-///
-/// fn swap<T>(a: &mut T, b: &mut T) {
-/// unsafe {
-/// // Create a bitwise copy of the value at `a` in `tmp`.
-/// let tmp = ptr::read(a);
-///
-/// // Exiting at this point (either by explicitly returning or by
-/// // calling a function which panics) would cause the value in `tmp` to
-/// // be dropped while the same value is still referenced by `a`. This
-/// // could trigger undefined behavior if `T` is not `Copy`.
-///
-/// // Create a bitwise copy of the value at `b` in `a`.
-/// // This is safe because mutable references cannot alias.
-/// ptr::copy_nonoverlapping(b, a, 1);
-///
-/// // As above, exiting here could trigger undefined behavior because
-/// // the same value is referenced by `a` and `b`.
-///
-/// // Move `tmp` into `b`.
-/// ptr::write(b, tmp);
-///
-/// // `tmp` has been moved (`write` takes ownership of its second argument),
-/// // so nothing is dropped implicitly here.
-/// }
-/// }
-///
-/// let mut foo = "foo".to_owned();
-/// let mut bar = "bar".to_owned();
-///
-/// swap(&mut foo, &mut bar);
-///
-/// assert_eq!(foo, "bar");
-/// assert_eq!(bar, "foo");
-/// ```
-///
-/// ## Ownership of the Returned Value
-///
-/// `read` creates a bitwise copy of `T`, regardless of whether `T` is [`Copy`].
-/// If `T` is not [`Copy`], using both the returned value and the value at
-/// `*src` can violate memory safety. Note that assigning to `*src` counts as a
-/// use because it will attempt to drop the value at `*src`.
-///
-/// [`write`] can be used to overwrite data without causing it to be dropped.
-///
-/// ```
-/// use std::ptr;
-///
-/// let mut s = String::from("foo");
-/// unsafe {
-/// // `s2` now points to the same underlying memory as `s`.
-/// let mut s2: String = ptr::read(&s);
-///
-/// assert_eq!(s2, "foo");
-///
-/// // Assigning to `s2` causes its original value to be dropped. Beyond
-/// // this point, `s` must no longer be used, as the underlying memory has
-/// // been freed.
-/// s2 = String::default();
-/// assert_eq!(s2, "");
-///
-/// // Assigning to `s` would cause the old value to be dropped again,
-/// // resulting in undefined behavior.
-/// // s = String::from("bar"); // ERROR
-///
-/// // `ptr::write` can be used to overwrite a value without dropping it.
-/// ptr::write(&mut s, String::from("bar"));
-/// }
-///
-/// assert_eq!(s, "bar");
-/// ```
-///
-/// [`mem::swap`]: ../mem/fn.swap.html
-/// [valid]: ../ptr/index.html#safety
-/// [`Copy`]: ../marker/trait.Copy.html
-/// [`read_unaligned`]: ./fn.read_unaligned.html
-/// [`write`]: ./fn.write.html
-#[inline]
-#[stable(feature = "rust1", since = "1.0.0")]
-pub unsafe fn read<T>(src: *const T) -> T {
- let mut tmp = MaybeUninit::<T>::uninit();
- copy_nonoverlapping(src, tmp.as_mut_ptr(), 1);
- tmp.assume_init()
-}
-
-/// Reads the value from `src` without moving it. This leaves the
-/// memory in `src` unchanged.
-///
-/// Unlike [`read`], `read_unaligned` works with unaligned pointers.
-///
-/// # Safety
-///
-/// Behavior is undefined if any of the following conditions are violated:
-///
-/// * `src` must be [valid] for reads.
-///
-/// Like [`read`], `read_unaligned` creates a bitwise copy of `T`, regardless of
-/// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the returned
-/// value and the value at `*src` can [violate memory safety][read-ownership].
-///
-/// Note that even if `T` has size `0`, the pointer must be non-NULL.
-///
-/// [`Copy`]: ../marker/trait.Copy.html
-/// [`read`]: ./fn.read.html
-/// [`write_unaligned`]: ./fn.write_unaligned.html
-/// [read-ownership]: ./fn.read.html#ownership-of-the-returned-value
-/// [valid]: ../ptr/index.html#safety
-///
-/// # Examples
-///
-/// Access members of a packed struct by reference:
-///
-/// ```
-/// use std::ptr;
-///
-/// #[repr(packed, C)]
-/// struct Packed {
-/// _padding: u8,
-/// unaligned: u32,
-/// }
-///
-/// let x = Packed {
-/// _padding: 0x00,
-/// unaligned: 0x01020304,
-/// };
-///
-/// let v = unsafe {
-/// // Take the address of a 32-bit integer which is not aligned.
-/// // This must be done as a raw pointer; unaligned references are invalid.
-/// let unaligned = &x.unaligned as *const u32;
-///
-/// // Dereferencing normally will emit an aligned load instruction,
-/// // causing undefined behavior.
-/// // let v = *unaligned; // ERROR
-///
-/// // Instead, use `read_unaligned` to read improperly aligned values.
-/// let v = ptr::read_unaligned(unaligned);
-///
-/// v
-/// };
-///
-/// // Accessing unaligned values directly is safe.
-/// assert!(x.unaligned == v);
-/// ```
-#[inline]
-#[stable(feature = "ptr_unaligned", since = "1.17.0")]
-pub unsafe fn read_unaligned<T>(src: *const T) -> T {
- let mut tmp = MaybeUninit::<T>::uninit();
- copy_nonoverlapping(src as *const u8,
- tmp.as_mut_ptr() as *mut u8,
- mem::size_of::<T>());
- tmp.assume_init()
-}
-
-/// Overwrites a memory location with the given value without reading or
-/// dropping the old value.
-///
-/// `write` does not drop the contents of `dst`. This is safe, but it could leak
-/// allocations or resources, so care should be taken not to overwrite an object
-/// that should be dropped.
-///
-/// Additionally, it does not drop `src`. Semantically, `src` is moved into the
-/// location pointed to by `dst`.
-///
-/// This is appropriate for initializing uninitialized memory, or overwriting
-/// memory that has previously been [`read`] from.
-///
-/// [`read`]: ./fn.read.html
-///
-/// # Safety
-///
-/// Behavior is undefined if any of the following conditions are violated:
-///
-/// * `dst` must be [valid] for writes.
-///
-/// * `dst` must be properly aligned. Use [`write_unaligned`] if this is not the
-/// case.
-///
-/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
-///
-/// [valid]: ../ptr/index.html#safety
-/// [`write_unaligned`]: ./fn.write_unaligned.html
-///
-/// # Examples
-///
-/// Basic usage:
-///
-/// ```
-/// let mut x = 0;
-/// let y = &mut x as *mut i32;
-/// let z = 12;
-///
-/// unsafe {
-/// std::ptr::write(y, z);
-/// assert_eq!(std::ptr::read(y), 12);
-/// }
-/// ```
-///
-/// Manually implement [`mem::swap`]:
-///
-/// ```
-/// use std::ptr;
-///
-/// fn swap<T>(a: &mut T, b: &mut T) {
-/// unsafe {
-/// // Create a bitwise copy of the value at `a` in `tmp`.
-/// let tmp = ptr::read(a);
-///
-/// // Exiting at this point (either by explicitly returning or by
-/// // calling a function which panics) would cause the value in `tmp` to
-/// // be dropped while the same value is still referenced by `a`. This
-/// // could trigger undefined behavior if `T` is not `Copy`.
-///
-/// // Create a bitwise copy of the value at `b` in `a`.
-/// // This is safe because mutable references cannot alias.
-/// ptr::copy_nonoverlapping(b, a, 1);
-///
-/// // As above, exiting here could trigger undefined behavior because
-/// // the same value is referenced by `a` and `b`.
-///
-/// // Move `tmp` into `b`.
-/// ptr::write(b, tmp);
-///
-/// // `tmp` has been moved (`write` takes ownership of its second argument),
-/// // so nothing is dropped implicitly here.
-/// }
-/// }
-///
-/// let mut foo = "foo".to_owned();
-/// let mut bar = "bar".to_owned();
-///
-/// swap(&mut foo, &mut bar);
-///
-/// assert_eq!(foo, "bar");
-/// assert_eq!(bar, "foo");
-/// ```
-///
-/// [`mem::swap`]: ../mem/fn.swap.html
-#[inline]
-#[stable(feature = "rust1", since = "1.0.0")]
-pub unsafe fn write<T>(dst: *mut T, src: T) {
- intrinsics::move_val_init(&mut *dst, src)
-}
-
-/// Overwrites a memory location with the given value without reading or
-/// dropping the old value.
-///
-/// Unlike [`write`], the pointer may be unaligned.
-///
-/// `write_unaligned` does not drop the contents of `dst`. This is safe, but it
-/// could leak allocations or resources, so care should be taken not to overwrite
-/// an object that should be dropped.
-///
-/// Additionally, it does not drop `src`. Semantically, `src` is moved into the
-/// location pointed to by `dst`.
-///
-/// This is appropriate for initializing uninitialized memory, or overwriting
-/// memory that has previously been read with [`read_unaligned`].
-///
-/// [`write`]: ./fn.write.html
-/// [`read_unaligned`]: ./fn.read_unaligned.html
-///
-/// # Safety
-///
-/// Behavior is undefined if any of the following conditions are violated:
-///
-/// * `dst` must be [valid] for writes.
-///
-/// Note that even if `T` has size `0`, the pointer must be non-NULL.
-///
-/// [valid]: ../ptr/index.html#safety
-///
-/// # Examples
-///
-/// Access fields in a packed struct:
-///
-/// ```
-/// use std::{mem, ptr};
-///
-/// #[repr(packed, C)]
-/// #[derive(Default)]
-/// struct Packed {
-/// _padding: u8,
-/// unaligned: u32,
-/// }
-///
-/// let v = 0x01020304;
-/// let mut x: Packed = unsafe { mem::zeroed() };
-///
-/// unsafe {
-/// // Take a reference to a 32-bit integer which is not aligned.
-/// let unaligned = &mut x.unaligned as *mut u32;
-///
-/// // Dereferencing normally will emit an aligned store instruction,
-/// // causing undefined behavior because the pointer is not aligned.
-/// // *unaligned = v; // ERROR
-///
-/// // Instead, use `write_unaligned` to write improperly aligned values.
-/// ptr::write_unaligned(unaligned, v);
-/// }
-///
-/// // Accessing unaligned values directly is safe.
-/// assert!(x.unaligned == v);
-/// ```
-#[inline]
-#[stable(feature = "ptr_unaligned", since = "1.17.0")]
-pub unsafe fn write_unaligned<T>(dst: *mut T, src: T) {
- copy_nonoverlapping(&src as *const T as *const u8,
- dst as *mut u8,
- mem::size_of::<T>());
- mem::forget(src);
-}
-
-/// Performs a volatile read of the value from `src` without moving it. This
-/// leaves the memory in `src` 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.
-///
-/// [`write_volatile`]: ./fn.write_volatile.html
-///
-/// # Notes
-///
-/// Rust does not currently have a rigorously and formally defined memory model,
-/// so the precise semantics of what "volatile" means here is subject to change
-/// over time. That being said, the semantics will almost always end up pretty
-/// similar to [C11's definition of volatile][c11].
-///
-/// The compiler shouldn't change the relative order or number of volatile
-/// memory operations. However, volatile memory operations on zero-sized types
-/// (e.g., if a zero-sized type is passed to `read_volatile`) are noops
-/// and may be ignored.
-///
-/// [c11]: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
-///
-/// # Safety
-///
-/// Behavior is undefined if any of the following conditions are violated:
-///
-/// * `src` must be [valid] for reads.
-///
-/// * `src` must be properly aligned.
-///
-/// Like [`read`], `read_volatile` creates a bitwise copy of `T`, regardless of
-/// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the returned
-/// value and the value at `*src` can [violate memory safety][read-ownership].
-/// However, storing non-[`Copy`] types in volatile memory is almost certainly
-/// incorrect.
-///
-/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
-///
-/// [valid]: ../ptr/index.html#safety
-/// [`Copy`]: ../marker/trait.Copy.html
-/// [`read`]: ./fn.read.html
-/// [read-ownership]: ./fn.read.html#ownership-of-the-returned-value
-///
-/// Just like in C, whether an operation is volatile has no bearing whatsoever
-/// on questions involving concurrent access from multiple threads. Volatile
-/// accesses behave exactly like non-atomic accesses in that regard. In particular,
-/// a race between a `read_volatile` and any write operation to the same location
-/// is undefined behavior.
-///
-/// # Examples
-///
-/// Basic usage:
-///
-/// ```
-/// let x = 12;
-/// let y = &x as *const i32;
-///
-/// unsafe {
-/// assert_eq!(std::ptr::read_volatile(y), 12);
-/// }
-/// ```
-#[inline]
-#[stable(feature = "volatile", since = "1.9.0")]
-pub unsafe fn read_volatile<T>(src: *const T) -> T {
- intrinsics::volatile_load(src)
-}
-
-/// 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.
-///
-/// `write_volatile` does not drop the contents of `dst`. This is safe, but it
-/// could leak allocations or resources, so care should be taken not to overwrite
-/// an object that should be dropped.
-///
-/// Additionally, it does not drop `src`. Semantically, `src` is moved into the
-/// location pointed to by `dst`.
-///
-/// [`read_volatile`]: ./fn.read_volatile.html
-///
-/// # Notes
-///
-/// Rust does not currently have a rigorously and formally defined memory model,
-/// so the precise semantics of what "volatile" means here is subject to change
-/// over time. That being said, the semantics will almost always end up pretty
-/// similar to [C11's definition of volatile][c11].
-///
-/// The compiler shouldn't change the relative order or number of volatile
-/// memory operations. However, volatile memory operations on zero-sized types
-/// (e.g., if a zero-sized type is passed to `write_volatile`) are noops
-/// and may be ignored.
-///
-/// [c11]: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
-///
-/// # Safety
-///
-/// Behavior is undefined if any of the following conditions are violated:
-///
-/// * `dst` must be [valid] for writes.
-///
-/// * `dst` must be properly aligned.
-///
-/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
-///
-/// [valid]: ../ptr/index.html#safety
-///
-/// Just like in C, whether an operation is volatile has no bearing whatsoever
-/// on questions involving concurrent access from multiple threads. Volatile
-/// accesses behave exactly like non-atomic accesses in that regard. In particular,
-/// a race between a `write_volatile` and any other operation (reading or writing)
-/// on the same location is undefined behavior.
-///
-/// # Examples
-///
-/// Basic usage:
-///
-/// ```
-/// let mut x = 0;
-/// let y = &mut x as *mut i32;
-/// let z = 12;
-///
-/// unsafe {
-/// std::ptr::write_volatile(y, z);
-/// assert_eq!(std::ptr::read_volatile(y), 12);
-/// }
-/// ```
-#[inline]
-#[stable(feature = "volatile", since = "1.9.0")]
-pub unsafe fn write_volatile<T>(dst: *mut T, src: T) {
- intrinsics::volatile_store(dst, src);
-}
-
-#[lang = "const_ptr"]
-impl<T: ?Sized> *const T {
- /// Returns `true` if the pointer is null.
- ///
- /// Note that unsized types have many possible null pointers, as only the
- /// raw data pointer is considered, not their length, vtable, etc.
- /// Therefore, two pointers that are null may still not compare equal to
- /// each other.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// let s: &str = "Follow the rabbit";
- /// let ptr: *const u8 = s.as_ptr();
- /// assert!(!ptr.is_null());
- /// ```
- #[stable(feature = "rust1", since = "1.0.0")]
- #[inline]
- pub fn is_null(self) -> bool {
- // Compare via a cast to a thin pointer, so fat pointers are only
- // considering their "data" part for null-ness.
- (self as *const u8) == null()
- }
-
- /// Cast to a pointer to a different type
- #[unstable(feature = "ptr_cast", issue = "60602")]
- #[inline]
- pub const fn cast<U>(self) -> *const U {
- self as _
- }
-
- /// Returns `None` if the pointer is null, or else returns a reference to
- /// the value wrapped in `Some`.
- ///
- /// # Safety
- ///
- /// While this method and its mutable counterpart are useful for
- /// null-safety, it is important to note that this is still an unsafe
- /// operation because the returned value could be pointing to invalid
- /// memory.
- ///
- /// Additionally, the lifetime `'a` returned is arbitrarily chosen and does
- /// not necessarily reflect the actual lifetime of the data.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// let ptr: *const u8 = &10u8 as *const u8;
- ///
- /// unsafe {
- /// if let Some(val_back) = ptr.as_ref() {
- /// println!("We got back the value: {}!", val_back);
- /// }
- /// }
- /// ```
- ///
- /// # Null-unchecked version
- ///
- /// If you are sure the pointer can never be null and are looking for some kind of
- /// `as_ref_unchecked` that returns the `&T` instead of `Option<&T>`, know that you can
- /// dereference the pointer directly.
- ///
- /// ```
- /// let ptr: *const u8 = &10u8 as *const u8;
- ///
- /// unsafe {
- /// let val_back = &*ptr;
- /// println!("We got back the value: {}!", val_back);
- /// }
- /// ```
- #[stable(feature = "ptr_as_ref", since = "1.9.0")]
- #[inline]
- pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
- if self.is_null() {
- None
- } else {
- Some(&*self)
- }
- }
-
- /// 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.
- ///
- /// Consider using `wrapping_offset` instead if these constraints are
- /// difficult to satisfy. The only advantage of this method is that it
- /// enables more aggressive compiler optimizations.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// let s: &str = "123";
- /// let ptr: *const u8 = s.as_ptr();
- ///
- /// unsafe {
- /// println!("{}", *ptr.offset(1) as char);
- /// println!("{}", *ptr.offset(2) as char);
- /// }
- /// ```
- #[stable(feature = "rust1", since = "1.0.0")]
- #[inline]
- pub unsafe fn offset(self, count: isize) -> *const T where T: Sized {
- intrinsics::offset(self, count)
- }
-
- /// Calculates the offset from a pointer using wrapping arithmetic.
- ///
- /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
- /// offset of `3 * size_of::<T>()` bytes.
- ///
- /// # Safety
- ///
- /// The resulting pointer does not need to be in bounds, but it is
- /// potentially hazardous to dereference (which requires `unsafe`).
- /// In particular, the resulting pointer may *not* be used to access a
- /// different allocated object than the one `self` points to. In other
- /// words, `x.wrapping_offset(y.wrapping_offset_from(x))` is
- /// *not* the same as `y`, and dereferencing it is undefined behavior
- /// unless `x` and `y` point into the same allocated object.
- ///
- /// Always use `.offset(count)` instead when possible, because `offset`
- /// allows the compiler to optimize better. If you need to cross object
- /// boundaries, cast the pointer to an integer and do the arithmetic there.
- ///
- /// # 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_offset(6);
- ///
- /// // This loop prints "1, 3, 5, "
- /// while ptr != end_rounded_up {
- /// unsafe {
- /// print!("{}, ", *ptr);
- /// }
- /// ptr = ptr.wrapping_offset(step);
- /// }
- /// ```
- #[stable(feature = "ptr_wrapping_offset", since = "1.16.0")]
- #[inline]
- pub fn wrapping_offset(self, count: isize) -> *const T where T: Sized {
- unsafe {
- intrinsics::arith_offset(self, count)
- }
- }
-
- /// 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
- /// [`wrapping_offset_from`]: #method.wrapping_offset_from
- ///
- /// # 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.
- ///
- /// * The distance between the pointers, **in bytes**, cannot overflow an `isize`.
- ///
- /// * The distance between the pointers, in bytes, must be an exact multiple
- /// of the size of `T`.
- ///
- /// * The distance being in bounds cannot rely on "wrapping around" the address space.
- ///
- /// The compiler and standard library generally try 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
- /// `ptr_into_vec.offset_from(vec.as_ptr())` 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_offset_from`] instead if these constraints are
- /// difficult to satisfy. The only advantage of this method is that it
- /// enables more aggressive compiler optimizations.
- ///
- /// # Panics
- ///
- /// This function panics if `T` is a Zero-Sized Type ("ZST").
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// #![feature(ptr_offset_from)]
- ///
- /// let a = [0; 5];
- /// let ptr1: *const i32 = &a[1];
- /// let ptr2: *const i32 = &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);
- /// }
- /// ```
- #[unstable(feature = "ptr_offset_from", issue = "41079")]
- #[inline]
- pub unsafe fn offset_from(self, origin: *const T) -> isize where T: Sized {
- let pointee_size = mem::size_of::<T>();
- assert!(0 < pointee_size && pointee_size <= isize::max_value() as usize);
-
- // This is the same sequence that Clang emits for pointer subtraction.
- // It can be neither `nsw` nor `nuw` because the input is treated as
- // unsigned but then the output is treated as signed, so neither works.
- let d = isize::wrapping_sub(self as _, origin as _);
- intrinsics::exact_div(d, pointee_size as _)
- }
-
- /// 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>()`.
- ///
- /// If the address different between the two pointers is not a multiple of
- /// `mem::size_of::<T>()` then the result of the division is rounded towards
- /// zero.
- ///
- /// Though this method is safe for any two pointers, note that its result
- /// will be mostly useless if the two pointers aren't into the same allocated
- /// object, for example if they point to two different local variables.
- ///
- /// # Panics
- ///
- /// This function panics if `T` is a zero-sized type.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// #![feature(ptr_wrapping_offset_from)]
- ///
- /// let a = [0; 5];
- /// let ptr1: *const i32 = &a[1];
- /// let ptr2: *const i32 = &a[3];
- /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
- /// assert_eq!(ptr1.wrapping_offset_from(ptr2), -2);
- /// assert_eq!(ptr1.wrapping_offset(2), ptr2);
- /// assert_eq!(ptr2.wrapping_offset(-2), ptr1);
- ///
- /// let ptr1: *const i32 = 3 as _;
- /// let ptr2: *const i32 = 13 as _;
- /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
- /// ```
- #[unstable(feature = "ptr_wrapping_offset_from", issue = "41079")]
- #[inline]
- pub fn wrapping_offset_from(self, origin: *const T) -> isize where T: Sized {
- let pointee_size = mem::size_of::<T>();
- assert!(0 < pointee_size && pointee_size <= isize::max_value() as usize);
-
- let d = isize::wrapping_sub(self as _, origin as _);
- d.wrapping_div(pointee_size as _)
- }
-
- /// 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.
- ///
- /// Consider using `wrapping_offset` instead if these constraints are
- /// difficult to satisfy. The only advantage of this method is that it
- /// enables more aggressive compiler optimizations.
- ///
- /// # 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")]
- #[inline]
- pub unsafe fn add(self, count: usize) -> Self
- where T: Sized,
- {
- 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.
- ///
- /// * 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_offset` instead if these constraints are
- /// difficult to satisfy. The only advantage of this method is that it
- /// enables more aggressive compiler optimizations.
- ///
- /// # 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")]
- #[inline]
- pub unsafe fn sub(self, count: usize) -> Self
- where T: Sized,
- {
- 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
- ///
- /// The resulting pointer does not need to be in bounds, but it is
- /// potentially hazardous to dereference (which requires `unsafe`).
- ///
- /// Always use `.add(count)` instead when possible, because `add`
- /// allows the compiler to optimize better.
- ///
- /// # 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")]
- #[inline]
- pub 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_sub())`)
- ///
- /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
- /// offset of `3 * size_of::<T>()` bytes.
- ///
- /// # Safety
- ///
- /// The resulting pointer does not need to be in bounds, but it is
- /// potentially hazardous to dereference (which requires `unsafe`).
- ///
- /// Always use `.sub(count)` instead when possible, because `sub`
- /// allows the compiler to optimize better.
- ///
- /// # 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")]
- #[inline]
- pub fn wrapping_sub(self, count: usize) -> Self
- where T: Sized,
- {
- self.wrapping_offset((count as isize).wrapping_neg())
- }
-
- /// 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`]: ./ptr/fn.read.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn read(self) -> T
- where T: Sized,
- {
- 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`]: ./ptr/fn.read_volatile.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn read_volatile(self) -> T
- where T: Sized,
- {
- 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`]: ./ptr/fn.read_unaligned.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn read_unaligned(self) -> T
- where T: Sized,
- {
- 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`]: ./ptr/fn.copy.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn copy_to(self, dest: *mut T, count: usize)
- where T: Sized,
- {
- 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`]: ./ptr/fn.copy_nonoverlapping.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn copy_to_nonoverlapping(self, dest: *mut T, count: usize)
- where T: Sized,
- {
- copy_nonoverlapping(self, dest, count)
- }
-
- /// 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_value()`.
- ///
- /// The offset is expressed in number of `T` elements, and not bytes. The value returned can be
- /// used with the `offset` or `offset_to` methods.
- ///
- /// There are no guarantees whatsover 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[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");
- }
- unsafe {
- align_offset(self, align)
- }
- }
-}
-
-
-#[lang = "mut_ptr"]
-impl<T: ?Sized> *mut T {
- /// Returns `true` if the pointer is null.
- ///
- /// Note that unsized types have many possible null pointers, as only the
- /// raw data pointer is considered, not their length, vtable, etc.
- /// Therefore, two pointers that are null may still not compare equal to
- /// each other.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// let mut s = [1, 2, 3];
- /// let ptr: *mut u32 = s.as_mut_ptr();
- /// assert!(!ptr.is_null());
- /// ```
- #[stable(feature = "rust1", since = "1.0.0")]
- #[inline]
- pub fn is_null(self) -> bool {
- // Compare via a cast to a thin pointer, so fat pointers are only
- // considering their "data" part for null-ness.
- (self as *mut u8) == null_mut()
- }
-
- /// Cast to a pointer to a different type
- #[unstable(feature = "ptr_cast", issue = "60602")]
- #[inline]
- pub const fn cast<U>(self) -> *mut U {
- self as _
- }
-
- /// Returns `None` if the pointer is null, or else returns a reference to
- /// the value wrapped in `Some`.
- ///
- /// # Safety
- ///
- /// While this method and its mutable counterpart are useful for
- /// null-safety, it is important to note that this is still an unsafe
- /// operation because the returned value could be pointing to invalid
- /// memory.
- ///
- /// Additionally, the lifetime `'a` returned is arbitrarily chosen and does
- /// not necessarily reflect the actual lifetime of the data.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// let ptr: *mut u8 = &mut 10u8 as *mut u8;
- ///
- /// unsafe {
- /// if let Some(val_back) = ptr.as_ref() {
- /// println!("We got back the value: {}!", val_back);
- /// }
- /// }
- /// ```
- ///
- /// # Null-unchecked version
- ///
- /// If you are sure the pointer can never be null and are looking for some kind of
- /// `as_ref_unchecked` that returns the `&T` instead of `Option<&T>`, know that you can
- /// dereference the pointer directly.
- ///
- /// ```
- /// let ptr: *mut u8 = &mut 10u8 as *mut u8;
- ///
- /// unsafe {
- /// let val_back = &*ptr;
- /// println!("We got back the value: {}!", val_back);
- /// }
- /// ```
- #[stable(feature = "ptr_as_ref", since = "1.9.0")]
- #[inline]
- pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
- if self.is_null() {
- None
- } else {
- Some(&*self)
- }
- }
-
- /// 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.
- ///
- /// Consider using `wrapping_offset` instead if these constraints are
- /// difficult to satisfy. The only advantage of this method is that it
- /// enables more aggressive compiler optimizations.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// let mut s = [1, 2, 3];
- /// let ptr: *mut u32 = s.as_mut_ptr();
- ///
- /// unsafe {
- /// println!("{}", *ptr.offset(1));
- /// println!("{}", *ptr.offset(2));
- /// }
- /// ```
- #[stable(feature = "rust1", since = "1.0.0")]
- #[inline]
- pub unsafe fn offset(self, count: isize) -> *mut T where T: Sized {
- intrinsics::offset(self, count) as *mut T
- }
-
- /// Calculates the offset from a pointer using wrapping arithmetic.
- /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
- /// offset of `3 * size_of::<T>()` bytes.
- ///
- /// # Safety
- ///
- /// The resulting pointer does not need to be in bounds, but it is
- /// potentially hazardous to dereference (which requires `unsafe`).
- /// In particular, the resulting pointer may *not* be used to access a
- /// different allocated object than the one `self` points to. In other
- /// words, `x.wrapping_offset(y.wrapping_offset_from(x))` is
- /// *not* the same as `y`, and dereferencing it is undefined behavior
- /// unless `x` and `y` point into the same allocated object.
- ///
- /// Always use `.offset(count)` instead when possible, because `offset`
- /// allows the compiler to optimize better. If you need to cross object
- /// boundaries, cast the pointer to an integer and do the arithmetic there.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// // Iterate using a raw pointer in increments of two elements
- /// let mut data = [1u8, 2, 3, 4, 5];
- /// let mut ptr: *mut u8 = data.as_mut_ptr();
- /// let step = 2;
- /// let end_rounded_up = ptr.wrapping_offset(6);
- ///
- /// while ptr != end_rounded_up {
- /// unsafe {
- /// *ptr = 0;
- /// }
- /// ptr = ptr.wrapping_offset(step);
- /// }
- /// assert_eq!(&data, &[0, 2, 0, 4, 0]);
- /// ```
- #[stable(feature = "ptr_wrapping_offset", since = "1.16.0")]
- #[inline]
- pub fn wrapping_offset(self, count: isize) -> *mut T where T: Sized {
- unsafe {
- intrinsics::arith_offset(self, count) as *mut T
- }
- }
-
- /// Returns `None` if the pointer is null, or else returns a mutable
- /// reference to the value wrapped in `Some`.
- ///
- /// # Safety
- ///
- /// As with `as_ref`, this is unsafe because it cannot verify the validity
- /// of the returned pointer, nor can it ensure that the lifetime `'a`
- /// returned is indeed a valid lifetime for the contained data.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// let mut s = [1, 2, 3];
- /// let ptr: *mut u32 = s.as_mut_ptr();
- /// let first_value = unsafe { ptr.as_mut().unwrap() };
- /// *first_value = 4;
- /// println!("{:?}", s); // It'll print: "[4, 2, 3]".
- /// ```
- #[stable(feature = "ptr_as_ref", since = "1.9.0")]
- #[inline]
- pub unsafe fn as_mut<'a>(self) -> Option<&'a mut T> {
- if self.is_null() {
- None
- } else {
- Some(&mut *self)
- }
- }
-
- /// 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
- /// [`wrapping_offset_from`]: #method.wrapping_offset_from-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.
- ///
- /// * The distance between the pointers, **in bytes**, cannot overflow an `isize`.
- ///
- /// * The distance between the pointers, in bytes, must be an exact multiple
- /// of the size of `T`.
- ///
- /// * The distance being in bounds cannot rely on "wrapping around" the address space.
- ///
- /// The compiler and standard library generally try 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
- /// `ptr_into_vec.offset_from(vec.as_ptr())` 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_offset_from`] instead if these constraints are
- /// difficult to satisfy. The only advantage of this method is that it
- /// enables more aggressive compiler optimizations.
- ///
- /// # Panics
- ///
- /// This function panics if `T` is a Zero-Sized Type ("ZST").
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// #![feature(ptr_offset_from)]
- ///
- /// 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);
- /// }
- /// ```
- #[unstable(feature = "ptr_offset_from", issue = "41079")]
- #[inline]
- pub unsafe fn offset_from(self, origin: *const T) -> isize where T: Sized {
- (self as *const T).offset_from(origin)
- }
-
- /// 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>()`.
- ///
- /// If the address different between the two pointers is not a multiple of
- /// `mem::size_of::<T>()` then the result of the division is rounded towards
- /// zero.
- ///
- /// Though this method is safe for any two pointers, note that its result
- /// will be mostly useless if the two pointers aren't into the same allocated
- /// object, for example if they point to two different local variables.
- ///
- /// # Panics
- ///
- /// This function panics if `T` is a zero-sized type.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// #![feature(ptr_wrapping_offset_from)]
- ///
- /// let mut a = [0; 5];
- /// let ptr1: *mut i32 = &mut a[1];
- /// let ptr2: *mut i32 = &mut a[3];
- /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
- /// assert_eq!(ptr1.wrapping_offset_from(ptr2), -2);
- /// assert_eq!(ptr1.wrapping_offset(2), ptr2);
- /// assert_eq!(ptr2.wrapping_offset(-2), ptr1);
- ///
- /// let ptr1: *mut i32 = 3 as _;
- /// let ptr2: *mut i32 = 13 as _;
- /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
- /// ```
- #[unstable(feature = "ptr_wrapping_offset_from", issue = "41079")]
- #[inline]
- pub fn wrapping_offset_from(self, origin: *const T) -> isize where T: Sized {
- (self as *const T).wrapping_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.
- ///
- /// * 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_offset` instead if these constraints are
- /// difficult to satisfy. The only advantage of this method is that it
- /// enables more aggressive compiler optimizations.
- ///
- /// # 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")]
- #[inline]
- pub unsafe fn add(self, count: usize) -> Self
- where T: Sized,
- {
- 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.
- ///
- /// * 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_offset` instead if these constraints are
- /// difficult to satisfy. The only advantage of this method is that it
- /// enables more aggressive compiler optimizations.
- ///
- /// # 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")]
- #[inline]
- pub unsafe fn sub(self, count: usize) -> Self
- where T: Sized,
- {
- 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
- ///
- /// The resulting pointer does not need to be in bounds, but it is
- /// potentially hazardous to dereference (which requires `unsafe`).
- ///
- /// Always use `.add(count)` instead when possible, because `add`
- /// allows the compiler to optimize better.
- ///
- /// # 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")]
- #[inline]
- pub 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_sub())`)
- ///
- /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
- /// offset of `3 * size_of::<T>()` bytes.
- ///
- /// # Safety
- ///
- /// The resulting pointer does not need to be in bounds, but it is
- /// potentially hazardous to dereference (which requires `unsafe`).
- ///
- /// Always use `.sub(count)` instead when possible, because `sub`
- /// allows the compiler to optimize better.
- ///
- /// # 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")]
- #[inline]
- pub fn wrapping_sub(self, count: usize) -> Self
- where T: Sized,
- {
- self.wrapping_offset((count as isize).wrapping_neg())
- }
-
- /// 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`]: ./ptr/fn.read.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn read(self) -> T
- where T: Sized,
- {
- 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`]: ./ptr/fn.read_volatile.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn read_volatile(self) -> T
- where T: Sized,
- {
- 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`]: ./ptr/fn.read_unaligned.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn read_unaligned(self) -> T
- where T: Sized,
- {
- 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`]: ./ptr/fn.copy.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn copy_to(self, dest: *mut T, count: usize)
- where T: Sized,
- {
- 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`]: ./ptr/fn.copy_nonoverlapping.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn copy_to_nonoverlapping(self, dest: *mut T, count: usize)
- where T: Sized,
- {
- 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`]: ./ptr/fn.copy.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn copy_from(self, src: *const T, count: usize)
- where T: Sized,
- {
- 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`]: ./ptr/fn.copy_nonoverlapping.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn copy_from_nonoverlapping(self, src: *const T, count: usize)
- where T: Sized,
- {
- 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`]: ./ptr/fn.drop_in_place.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn drop_in_place(self) {
- 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`]: ./ptr/fn.write.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn write(self, val: T)
- where T: Sized,
- {
- 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`]: ./ptr/fn.write_bytes.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn write_bytes(self, val: u8, count: usize)
- where T: Sized,
- {
- 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`]: ./ptr/fn.write_volatile.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn write_volatile(self, val: T)
- where T: Sized,
- {
- 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`]: ./ptr/fn.write_unaligned.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn write_unaligned(self, val: T)
- where T: Sized,
- {
- 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`]: ./ptr/fn.replace.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn replace(self, src: T) -> T
- where T: Sized,
- {
- 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`]: ./ptr/fn.swap.html
- #[stable(feature = "pointer_methods", since = "1.26.0")]
- #[inline]
- pub unsafe fn swap(self, with: *mut T)
- where T: Sized,
- {
- 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_value()`.
- ///
- /// The offset is expressed in number of `T` elements, and not bytes. The value returned can be
- /// used with the `offset` or `offset_to` methods.
- ///
- /// There are no guarantees whatsover 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[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");
- }
- unsafe {
- align_offset(self, align)
- }
- }
-}
-
-/// Align pointer `p`.
-///
-/// Calculate offset (in terms of elements of `stride` stride) that has to be applied
-/// to pointer `p` so that pointer `p` would get aligned to `a`.
-///
-/// Note: This implementation has been carefully tailored to not panic. It is UB for this to panic.
-/// The only real change that can be made here is change of `INV_TABLE_MOD_16` and associated
-/// constants.
-///
-/// If we ever decide to make it possible to call the intrinsic with `a` that is not a
-/// power-of-two, it will probably be more prudent to just change to a naive implementation rather
-/// than trying to adapt this to accommodate that change.
-///
-/// Any questions go to @nagisa.
-#[lang="align_offset"]
-pub(crate) unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
- /// Calculate multiplicative modular inverse of `x` modulo `m`.
- ///
- /// This implementation is tailored for align_offset and has following preconditions:
- ///
- /// * `m` is a power-of-two;
- /// * `x < m`; (if `x ≥ m`, pass in `x % m` instead)
- ///
- /// Implementation of this function shall not panic. Ever.
- #[inline]
- fn mod_inv(x: usize, m: usize) -> usize {
- /// Multiplicative modular inverse table modulo 2⁴ = 16.
- ///
- /// Note, that this table does not contain values where inverse does not exist (i.e., for
- /// `0⁻¹ mod 16`, `2⁻¹ mod 16`, etc.)
- const INV_TABLE_MOD_16: [u8; 8] = [1, 11, 13, 7, 9, 3, 5, 15];
- /// Modulo for which the `INV_TABLE_MOD_16` is intended.
- const INV_TABLE_MOD: usize = 16;
- /// INV_TABLE_MOD²
- const INV_TABLE_MOD_SQUARED: usize = INV_TABLE_MOD * INV_TABLE_MOD;
-
- let table_inverse = INV_TABLE_MOD_16[(x & (INV_TABLE_MOD - 1)) >> 1] as usize;
- if m <= INV_TABLE_MOD {
- table_inverse & (m - 1)
- } else {
- // We iterate "up" using the following formula:
- //
- // $$ xy ≡ 1 (mod 2ⁿ) → xy (2 - xy) ≡ 1 (mod 2²ⁿ) $$
- //
- // until 2²ⁿ ≥ m. Then we can reduce to our desired `m` by taking the result `mod m`.
- let mut inverse = table_inverse;
- let mut going_mod = INV_TABLE_MOD_SQUARED;
- loop {
- // y = y * (2 - xy) mod n
- //
- // Note, that we use wrapping operations here intentionally – the original formula
- // uses e.g., subtraction `mod n`. It is entirely fine to do them `mod
- // usize::max_value()` instead, because we take the result `mod n` at the end
- // anyway.
- inverse = inverse.wrapping_mul(
- 2usize.wrapping_sub(x.wrapping_mul(inverse))
- ) & (going_mod - 1);
- if going_mod > m {
- return inverse & (m - 1);
- }
- going_mod = going_mod.wrapping_mul(going_mod);
- }
- }
- }
-
- let stride = mem::size_of::<T>();
- let a_minus_one = a.wrapping_sub(1);
- let pmoda = p as usize & a_minus_one;
-
- if pmoda == 0 {
- // Already aligned. Yay!
- return 0;
- }
-
- if stride <= 1 {
- return if stride == 0 {
- // If the pointer is not aligned, and the element is zero-sized, then no amount of
- // elements will ever align the pointer.
- !0
- } else {
- a.wrapping_sub(pmoda)
- };
- }
-
- let smoda = stride & a_minus_one;
- // a is power-of-two so cannot be 0. stride = 0 is handled above.
- let gcdpow = intrinsics::cttz_nonzero(stride).min(intrinsics::cttz_nonzero(a));
- let gcd = 1usize << gcdpow;
-
- if p as usize & (gcd - 1) == 0 {
- // This branch solves for the following linear congruence equation:
- //
- // $$ p + so ≡ 0 mod a $$
- //
- // $p$ here is the pointer value, $s$ – stride of `T`, $o$ offset in `T`s, and $a$ – the
- // requested alignment.
- //
- // g = gcd(a, s)
- // o = (a - (p mod a))/g * ((s/g)⁻¹ mod a)
- //
- // The first term is “the relative alignment of p to a”, the second term is “how does
- // incrementing p by s bytes change the relative alignment of p”. Division by `g` is
- // necessary to make this equation well formed if $a$ and $s$ are not co-prime.
- //
- // Furthermore, the result produced by this solution is not “minimal”, so it is necessary
- // to take the result $o mod lcm(s, a)$. We can replace $lcm(s, a)$ with just a $a / g$.
- let j = a.wrapping_sub(pmoda) >> gcdpow;
- let k = smoda >> gcdpow;
- return intrinsics::unchecked_rem(j.wrapping_mul(mod_inv(k, a)), a >> gcdpow);
- }
-
- // Cannot be aligned at all.
- usize::max_value()
-}
-
-
-
-// Equality for pointers
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> PartialEq for *const T {
- #[inline]
- fn eq(&self, other: &*const T) -> bool { *self == *other }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Eq for *const T {}
-
-#[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 {}
-
-/// Compares raw pointers for equality.
-///
-/// This is the same as using the `==` operator, but less generic:
-/// the arguments have to be `*const T` raw pointers,
-/// not anything that implements `PartialEq`.
-///
-/// This can be used to compare `&T` references (which coerce to `*const T` implicitly)
-/// by their address rather than comparing the values they point to
-/// (which is what the `PartialEq for &T` implementation does).
-///
-/// # Examples
-///
-/// ```
-/// use std::ptr;
-///
-/// let five = 5;
-/// let other_five = 5;
-/// let five_ref = &five;
-/// let same_five_ref = &five;
-/// let other_five_ref = &other_five;
-///
-/// assert!(five_ref == same_five_ref);
-/// assert!(ptr::eq(five_ref, same_five_ref));
-///
-/// assert!(five_ref == other_five_ref);
-/// assert!(!ptr::eq(five_ref, other_five_ref));
-/// ```
-///
-/// Slices are also compared by their length (fat pointers):
-///
-/// ```
-/// let a = [1, 2, 3];
-/// assert!(std::ptr::eq(&a[..3], &a[..3]));
-/// assert!(!std::ptr::eq(&a[..2], &a[..3]));
-/// assert!(!std::ptr::eq(&a[0..2], &a[1..3]));
-/// ```
-///
-/// Traits are also compared by their implementation:
-///
-/// ```
-/// #[repr(transparent)]
-/// struct Wrapper { member: i32 }
-///
-/// trait Trait {}
-/// impl Trait for Wrapper {}
-/// impl Trait for i32 {}
-///
-/// fn main() {
-/// let wrapper = Wrapper { member: 10 };
-///
-/// // Pointers have equal addresses.
-/// assert!(std::ptr::eq(
-/// &wrapper as *const Wrapper as *const u8,
-/// &wrapper.member as *const i32 as *const u8
-/// ));
-///
-/// // Objects have equal addresses, but `Trait` has different implementations.
-/// assert!(!std::ptr::eq(
-/// &wrapper as &dyn Trait,
-/// &wrapper.member as &dyn Trait,
-/// ));
-/// assert!(!std::ptr::eq(
-/// &wrapper as &dyn Trait as *const dyn Trait,
-/// &wrapper.member as &dyn Trait as *const dyn Trait,
-/// ));
-///
-/// // Converting the reference to a `*const u8` compares by address.
-/// assert!(std::ptr::eq(
-/// &wrapper as &dyn Trait as *const dyn Trait as *const u8,
-/// &wrapper.member as &dyn Trait as *const dyn Trait as *const u8,
-/// ));
-/// }
-/// ```
-#[stable(feature = "ptr_eq", since = "1.17.0")]
-#[inline]
-pub fn eq<T: ?Sized>(a: *const T, b: *const T) -> bool {
- a == b
-}
-
-/// Hash a raw pointer.
-///
-/// This can be used to hash a `&T` reference (which coerces to `*const T` implicitly)
-/// by its address rather than the value it points to
-/// (which is what the `Hash for &T` implementation does).
-///
-/// # Examples
-///
-/// ```
-/// use std::collections::hash_map::DefaultHasher;
-/// use std::hash::{Hash, Hasher};
-/// use std::ptr;
-///
-/// let five = 5;
-/// let five_ref = &five;
-///
-/// let mut hasher = DefaultHasher::new();
-/// ptr::hash(five_ref, &mut hasher);
-/// let actual = hasher.finish();
-///
-/// let mut hasher = DefaultHasher::new();
-/// (five_ref as *const i32).hash(&mut hasher);
-/// let expected = hasher.finish();
-///
-/// assert_eq!(actual, expected);
-/// ```
-#[stable(feature = "ptr_hash", since = "1.35.0")]
-pub fn hash<T: ?Sized, S: hash::Hasher>(hashee: *const T, into: &mut S) {
- use crate::hash::Hash;
- hashee.hash(into);
-}
-
-// Impls for function pointers
-macro_rules! fnptr_impls_safety_abi {
- ($FnTy: ty, $($Arg: ident),*) => {
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> PartialEq for $FnTy {
- #[inline]
- fn eq(&self, other: &Self) -> bool {
- *self as usize == *other as usize
- }
- }
-
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> Eq for $FnTy {}
-
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> PartialOrd for $FnTy {
- #[inline]
- fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
- (*self as usize).partial_cmp(&(*other as usize))
- }
- }
-
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> Ord for $FnTy {
- #[inline]
- fn cmp(&self, other: &Self) -> Ordering {
- (*self as usize).cmp(&(*other as usize))
- }
- }
-
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> hash::Hash for $FnTy {
- fn hash<HH: hash::Hasher>(&self, state: &mut HH) {
- state.write_usize(*self as usize)
- }
- }
-
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> fmt::Pointer for $FnTy {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::Pointer::fmt(&(*self as *const ()), f)
- }
- }
-
- #[stable(feature = "fnptr_impls", since = "1.4.0")]
- impl<Ret, $($Arg),*> fmt::Debug for $FnTy {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::Pointer::fmt(&(*self as *const ()), f)
- }
- }
- }
-}
-
-macro_rules! fnptr_impls_args {
- ($($Arg: ident),+) => {
- fnptr_impls_safety_abi! { extern "Rust" fn($($Arg),*) -> Ret, $($Arg),* }
- fnptr_impls_safety_abi! { extern "C" fn($($Arg),*) -> Ret, $($Arg),* }
- fnptr_impls_safety_abi! { extern "C" fn($($Arg),* , ...) -> Ret, $($Arg),* }
- fnptr_impls_safety_abi! { unsafe extern "Rust" fn($($Arg),*) -> Ret, $($Arg),* }
- fnptr_impls_safety_abi! { unsafe extern "C" fn($($Arg),*) -> Ret, $($Arg),* }
- fnptr_impls_safety_abi! { unsafe extern "C" fn($($Arg),* , ...) -> Ret, $($Arg),* }
- };
- () => {
- // No variadic functions with 0 parameters
- fnptr_impls_safety_abi! { extern "Rust" fn() -> Ret, }
- fnptr_impls_safety_abi! { extern "C" fn() -> Ret, }
- fnptr_impls_safety_abi! { unsafe extern "Rust" fn() -> Ret, }
- fnptr_impls_safety_abi! { unsafe extern "C" fn() -> Ret, }
- };
-}
-
-fnptr_impls_args! { }
-fnptr_impls_args! { A }
-fnptr_impls_args! { A, B }
-fnptr_impls_args! { A, B, C }
-fnptr_impls_args! { A, B, C, D }
-fnptr_impls_args! { A, B, C, D, E }
-fnptr_impls_args! { A, B, C, D, E, F }
-fnptr_impls_args! { A, B, C, D, E, F, G }
-fnptr_impls_args! { A, B, C, D, E, F, G, H }
-fnptr_impls_args! { A, B, C, D, E, F, G, H, I }
-fnptr_impls_args! { A, B, C, D, E, F, G, H, I, J }
-fnptr_impls_args! { A, B, C, D, E, F, G, H, I, J, K }
-fnptr_impls_args! { A, B, C, D, E, F, G, H, I, J, K, L }
-
-// Comparison for pointers
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Ord for *const T {
- #[inline]
- fn cmp(&self, other: &*const T) -> Ordering {
- if self < other {
- Less
- } else if self == other {
- Equal
- } else {
- Greater
- }
- }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> PartialOrd for *const T {
- #[inline]
- fn partial_cmp(&self, other: &*const T) -> Option<Ordering> {
- Some(self.cmp(other))
- }
-
- #[inline]
- fn lt(&self, other: &*const T) -> bool { *self < *other }
-
- #[inline]
- fn le(&self, other: &*const T) -> bool { *self <= *other }
-
- #[inline]
- fn gt(&self, other: &*const T) -> bool { *self > *other }
-
- #[inline]
- fn ge(&self, other: &*const T) -> bool { *self >= *other }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> Ord for *mut T {
- #[inline]
- fn cmp(&self, other: &*mut T) -> Ordering {
- if self < other {
- Less
- } else if self == other {
- Equal
- } else {
- Greater
- }
- }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> PartialOrd for *mut T {
- #[inline]
- fn partial_cmp(&self, other: &*mut T) -> Option<Ordering> {
- Some(self.cmp(other))
- }
-
- #[inline]
- fn lt(&self, other: &*mut T) -> bool { *self < *other }
-
- #[inline]
- fn le(&self, other: &*mut T) -> bool { *self <= *other }
-
- #[inline]
- fn gt(&self, other: &*mut T) -> bool { *self > *other }
-
- #[inline]
- fn ge(&self, other: &*mut T) -> bool { *self >= *other }
-}
-
-/// A wrapper around a raw non-null `*mut T` that indicates that the possessor
-/// of this wrapper owns the referent. Useful for building abstractions like
-/// `Box<T>`, `Vec<T>`, `String`, and `HashMap<K, V>`.
-///
-/// Unlike `*mut T`, `Unique<T>` behaves "as if" it were an instance of `T`.
-/// It implements `Send`/`Sync` if `T` is `Send`/`Sync`. It also implies
-/// the kind of strong aliasing guarantees an instance of `T` can expect:
-/// the referent of the pointer should not be modified without a unique path to
-/// its owning Unique.
-///
-/// If you're uncertain of whether it's correct to use `Unique` for your purposes,
-/// consider using `NonNull`, which has weaker semantics.
-///
-/// Unlike `*mut T`, the pointer must always be non-null, even if the pointer
-/// is never dereferenced. This is so that enums may use this forbidden value
-/// as a discriminant -- `Option<Unique<T>>` has the same size as `Unique<T>`.
-/// However the pointer may still dangle if it isn't dereferenced.
-///
-/// Unlike `*mut T`, `Unique<T>` is covariant over `T`. This should always be correct
-/// for any type which upholds Unique's aliasing requirements.
-#[unstable(feature = "ptr_internals", issue = "0",
- reason = "use NonNull instead and consider PhantomData<T> \
- (if you also use #[may_dangle]), Send, and/or Sync")]
-#[doc(hidden)]
-#[repr(transparent)]
-#[rustc_layout_scalar_valid_range_start(1)]
-pub struct Unique<T: ?Sized> {
- pointer: *const T,
- // NOTE: this marker has no consequences for variance, but is necessary
- // for dropck to understand that we logically own a `T`.
- //
- // For details, see:
- // https://github.com/rust-lang/rfcs/blob/master/text/0769-sound-generic-drop.md#phantom-data
- _marker: PhantomData<T>,
-}
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: ?Sized> fmt::Debug for Unique<T> {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::Pointer::fmt(&self.as_ptr(), f)
- }
-}
-
-/// `Unique` pointers are `Send` if `T` is `Send` because the data they
-/// reference is unaliased. Note that this aliasing invariant is
-/// unenforced by the type system; the abstraction using the
-/// `Unique` must enforce it.
-#[unstable(feature = "ptr_internals", issue = "0")]
-unsafe impl<T: Send + ?Sized> Send for Unique<T> { }
-
-/// `Unique` pointers are `Sync` if `T` is `Sync` because the data they
-/// reference is unaliased. Note that this aliasing invariant is
-/// unenforced by the type system; the abstraction using the
-/// `Unique` must enforce it.
-#[unstable(feature = "ptr_internals", issue = "0")]
-unsafe impl<T: Sync + ?Sized> Sync for Unique<T> { }
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: Sized> Unique<T> {
- /// Creates a new `Unique` that is dangling, but well-aligned.
- ///
- /// This is useful for initializing types which lazily allocate, like
- /// `Vec::new` does.
- ///
- /// Note that the pointer value may potentially represent a valid pointer to
- /// a `T`, which means this must not be used as a "not yet initialized"
- /// sentinel value. Types that lazily allocate must track initialization by
- /// some other means.
- // FIXME: rename to dangling() to match NonNull?
- pub const fn empty() -> Self {
- unsafe {
- Unique::new_unchecked(mem::align_of::<T>() as *mut T)
- }
- }
-}
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: ?Sized> Unique<T> {
- /// Creates a new `Unique`.
- ///
- /// # Safety
- ///
- /// `ptr` must be non-null.
- pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
- Unique { pointer: ptr as _, _marker: PhantomData }
- }
-
- /// Creates a new `Unique` if `ptr` is non-null.
- pub fn new(ptr: *mut T) -> Option<Self> {
- if !ptr.is_null() {
- Some(unsafe { Unique { pointer: ptr as _, _marker: PhantomData } })
- } else {
- None
- }
- }
-
- /// Acquires the underlying `*mut` pointer.
- pub const fn as_ptr(self) -> *mut T {
- self.pointer as *mut T
- }
-
- /// Dereferences the content.
- ///
- /// The resulting lifetime is bound to self so this behaves "as if"
- /// it were actually an instance of T that is getting borrowed. If a longer
- /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`.
- pub unsafe fn as_ref(&self) -> &T {
- &*self.as_ptr()
- }
-
- /// Mutably dereferences the content.
- ///
- /// The resulting lifetime is bound to self so this behaves "as if"
- /// it were actually an instance of T that is getting borrowed. If a longer
- /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`.
- pub unsafe fn as_mut(&mut self) -> &mut T {
- &mut *self.as_ptr()
- }
-}
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: ?Sized> Clone for Unique<T> {
- fn clone(&self) -> Self {
- *self
- }
-}
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: ?Sized> Copy for Unique<T> { }
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: ?Sized, U: ?Sized> CoerceUnsized<Unique<U>> for Unique<T> where T: Unsize<U> { }
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: ?Sized, U: ?Sized> DispatchFromDyn<Unique<U>> for Unique<T> where T: Unsize<U> { }
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: ?Sized> fmt::Pointer for Unique<T> {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::Pointer::fmt(&self.as_ptr(), f)
- }
-}
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: ?Sized> From<&mut T> for Unique<T> {
- fn from(reference: &mut T) -> Self {
- unsafe { Unique { pointer: reference as *mut T, _marker: PhantomData } }
- }
-}
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: ?Sized> From<&T> for Unique<T> {
- fn from(reference: &T) -> Self {
- unsafe { Unique { pointer: reference as *const T, _marker: PhantomData } }
- }
-}
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<'a, T: ?Sized> From<NonNull<T>> for Unique<T> {
- fn from(p: NonNull<T>) -> Self {
- unsafe { Unique { pointer: p.pointer, _marker: PhantomData } }
- }
-}
-
-/// `*mut T` but non-zero and covariant.
-///
-/// This is often the correct thing to use when building data structures using
-/// raw pointers, but is ultimately more dangerous to use because of its additional
-/// properties. If you're not sure if you should use `NonNull<T>`, just use `*mut T`!
-///
-/// Unlike `*mut T`, the pointer must always be non-null, even if the pointer
-/// is never dereferenced. This is so that enums may use this forbidden value
-/// as a discriminant -- `Option<NonNull<T>>` has the same size as `*mut T`.
-/// However the pointer may still dangle if it isn't dereferenced.
-///
-/// Unlike `*mut T`, `NonNull<T>` is covariant over `T`. If this is incorrect
-/// for your use case, you should include some [`PhantomData`] in your type to
-/// provide invariance, such as `PhantomData<Cell<T>>` or `PhantomData<&'a mut T>`.
-/// Usually this won't be necessary; covariance is correct for most safe abstractions,
-/// such as `Box`, `Rc`, `Arc`, `Vec`, and `LinkedList`. This is the case because they
-/// provide a public API that follows the normal shared XOR mutable rules of Rust.
-///
-/// Notice that `NonNull<T>` has a `From` instance for `&T`. However, this does
-/// not change the fact that mutating through a (pointer derived from a) shared
-/// reference is undefined behavior unless the mutation happens inside an
-/// [`UnsafeCell<T>`]. The same goes for creating a mutable reference from a shared
-/// reference. When using this `From` instance without an `UnsafeCell<T>`,
-/// it is your responsibility to ensure that `as_mut` is never called, and `as_ptr`
-/// is never used for mutation.
-///
-/// [`PhantomData`]: ../marker/struct.PhantomData.html
-/// [`UnsafeCell<T>`]: ../cell/struct.UnsafeCell.html
-#[stable(feature = "nonnull", since = "1.25.0")]
-#[repr(transparent)]
-#[rustc_layout_scalar_valid_range_start(1)]
-#[cfg_attr(not(stage0), rustc_nonnull_optimization_guaranteed)]
-pub struct NonNull<T: ?Sized> {
- pointer: *const T,
-}
-
-/// `NonNull` pointers are not `Send` because the data they reference may be aliased.
-// N.B., this impl is unnecessary, but should provide better error messages.
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> !Send for NonNull<T> { }
-
-/// `NonNull` pointers are not `Sync` because the data they reference may be aliased.
-// N.B., this impl is unnecessary, but should provide better error messages.
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> !Sync for NonNull<T> { }
-
-impl<T: Sized> NonNull<T> {
- /// Creates a new `NonNull` that is dangling, but well-aligned.
- ///
- /// This is useful for initializing types which lazily allocate, like
- /// `Vec::new` does.
- ///
- /// Note that the pointer value may potentially represent a valid pointer to
- /// a `T`, which means this must not be used as a "not yet initialized"
- /// sentinel value. Types that lazily allocate must track initialization by
- /// some other means.
- #[stable(feature = "nonnull", since = "1.25.0")]
- #[inline]
- pub const fn dangling() -> Self {
- unsafe {
- let ptr = mem::align_of::<T>() as *mut T;
- NonNull::new_unchecked(ptr)
- }
- }
-}
-
-impl<T: ?Sized> NonNull<T> {
- /// Creates a new `NonNull`.
- ///
- /// # Safety
- ///
- /// `ptr` must be non-null.
- #[stable(feature = "nonnull", since = "1.25.0")]
- #[inline]
- pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
- NonNull { pointer: ptr as _ }
- }
-
- /// Creates a new `NonNull` if `ptr` is non-null.
- #[stable(feature = "nonnull", since = "1.25.0")]
- #[inline]
- pub fn new(ptr: *mut T) -> Option<Self> {
- if !ptr.is_null() {
- Some(unsafe { Self::new_unchecked(ptr) })
- } else {
- None
- }
- }
-
- /// Acquires the underlying `*mut` pointer.
- #[stable(feature = "nonnull", since = "1.25.0")]
- #[inline]
- pub const fn as_ptr(self) -> *mut T {
- self.pointer as *mut T
- }
-
- /// Dereferences the content.
- ///
- /// The resulting lifetime is bound to self so this behaves "as if"
- /// it were actually an instance of T that is getting borrowed. If a longer
- /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`.
- #[stable(feature = "nonnull", since = "1.25.0")]
- #[inline]
- pub unsafe fn as_ref(&self) -> &T {
- &*self.as_ptr()
- }
-
- /// Mutably dereferences the content.
- ///
- /// The resulting lifetime is bound to self so this behaves "as if"
- /// it were actually an instance of T that is getting borrowed. If a longer
- /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`.
- #[stable(feature = "nonnull", since = "1.25.0")]
- #[inline]
- pub unsafe fn as_mut(&mut self) -> &mut T {
- &mut *self.as_ptr()
- }
-
- /// Cast to a pointer of another type
- #[stable(feature = "nonnull_cast", since = "1.27.0")]
- #[inline]
- pub const fn cast<U>(self) -> NonNull<U> {
- unsafe {
- NonNull::new_unchecked(self.as_ptr() as *mut U)
- }
- }
-}
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> Clone for NonNull<T> {
- fn clone(&self) -> Self {
- *self
- }
-}
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> Copy for NonNull<T> { }
-
-#[unstable(feature = "coerce_unsized", issue = "27732")]
-impl<T: ?Sized, U: ?Sized> CoerceUnsized<NonNull<U>> for NonNull<T> where T: Unsize<U> { }
-
-#[unstable(feature = "dispatch_from_dyn", issue = "0")]
-impl<T: ?Sized, U: ?Sized> DispatchFromDyn<NonNull<U>> for NonNull<T> where T: Unsize<U> { }
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> fmt::Debug for NonNull<T> {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::Pointer::fmt(&self.as_ptr(), f)
- }
-}
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> fmt::Pointer for NonNull<T> {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::Pointer::fmt(&self.as_ptr(), f)
- }
-}
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> Eq for NonNull<T> {}
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> PartialEq for NonNull<T> {
- #[inline]
- fn eq(&self, other: &Self) -> bool {
- self.as_ptr() == other.as_ptr()
- }
-}
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> Ord for NonNull<T> {
- #[inline]
- fn cmp(&self, other: &Self) -> Ordering {
- self.as_ptr().cmp(&other.as_ptr())
- }
-}
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> PartialOrd for NonNull<T> {
- #[inline]
- fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
- self.as_ptr().partial_cmp(&other.as_ptr())
- }
-}
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> hash::Hash for NonNull<T> {
- #[inline]
- fn hash<H: hash::Hasher>(&self, state: &mut H) {
- self.as_ptr().hash(state)
- }
-}
-
-#[unstable(feature = "ptr_internals", issue = "0")]
-impl<T: ?Sized> From<Unique<T>> for NonNull<T> {
- #[inline]
- fn from(unique: Unique<T>) -> Self {
- unsafe { NonNull { pointer: unique.pointer } }
- }
-}
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> From<&mut T> for NonNull<T> {
- #[inline]
- fn from(reference: &mut T) -> Self {
- unsafe { NonNull { pointer: reference as *mut T } }
- }
-}
-
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: ?Sized> From<&T> for NonNull<T> {
- #[inline]
- fn from(reference: &T) -> Self {
- unsafe { NonNull { pointer: reference as *const T } }
- }
-}
--- /dev/null
+//! Manually manage memory through raw pointers.
+//!
+//! *[See also the pointer primitive types](../../std/primitive.pointer.html).*
+//!
+//! # Safety
+//!
+//! Many functions in this module take raw pointers as arguments and read from
+//! or write to them. For this to be safe, these pointers must be *valid*.
+//! Whether a pointer is valid depends on the operation it is used for
+//! (read or write), and the extent of the memory that is accessed (i.e.,
+//! how many bytes are read/written). Most functions use `*mut T` and `*const T`
+//! to access only a single value, in which case the documentation omits the size
+//! and implicitly assumes it to be `size_of::<T>()` bytes.
+//!
+//! The precise rules for validity are not determined yet. The guarantees that are
+//! provided at this point are very minimal:
+//!
+//! * A [null] pointer is *never* valid, not even for accesses of [size zero][zst].
+//! * All pointers (except for the null pointer) are valid for all operations of
+//! [size zero][zst].
+//! * All accesses performed by functions in this module are *non-atomic* in the sense
+//! of [atomic operations] used to synchronize between threads. This means it is
+//! undefined behavior to perform two concurrent accesses to the same location from different
+//! threads unless both accesses only read from memory. Notice that this explicitly
+//! includes [`read_volatile`] and [`write_volatile`]: Volatile accesses cannot
+//! be used for inter-thread synchronization.
+//! * The result of casting a reference to a pointer is valid for as long as the
+//! underlying object is live and no reference (just raw pointers) is used to
+//! access the same memory.
+//!
+//! These axioms, along with careful use of [`offset`] for pointer arithmetic,
+//! are enough to correctly implement many useful things in unsafe code. Stronger guarantees
+//! will be provided eventually, as the [aliasing] rules are being determined. For more
+//! information, see the [book] as well as the section in the reference devoted
+//! to [undefined behavior][ub].
+//!
+//! ## Alignment
+//!
+//! Valid raw pointers as defined above are not necessarily properly aligned (where
+//! "proper" alignment is defined by the pointee type, i.e., `*const T` must be
+//! aligned to `mem::align_of::<T>()`). However, most functions require their
+//! arguments to be properly aligned, and will explicitly state
+//! this requirement in their documentation. Notable exceptions to this are
+//! [`read_unaligned`] and [`write_unaligned`].
+//!
+//! When a function requires proper alignment, it does so even if the access
+//! has size 0, i.e., even if memory is not actually touched. Consider using
+//! [`NonNull::dangling`] in such cases.
+//!
+//! [aliasing]: ../../nomicon/aliasing.html
+//! [book]: ../../book/ch19-01-unsafe-rust.html#dereferencing-a-raw-pointer
+//! [ub]: ../../reference/behavior-considered-undefined.html
+//! [null]: ./fn.null.html
+//! [zst]: ../../nomicon/exotic-sizes.html#zero-sized-types-zsts
+//! [atomic operations]: ../../std/sync/atomic/index.html
+//! [`copy`]: ../../std/ptr/fn.copy.html
+//! [`offset`]: ../../std/primitive.pointer.html#method.offset
+//! [`read_unaligned`]: ./fn.read_unaligned.html
+//! [`write_unaligned`]: ./fn.write_unaligned.html
+//! [`read_volatile`]: ./fn.read_volatile.html
+//! [`write_volatile`]: ./fn.write_volatile.html
+//! [`NonNull::dangling`]: ./struct.NonNull.html#method.dangling
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use crate::intrinsics;
+use crate::fmt;
+use crate::hash;
+use crate::mem::{self, MaybeUninit};
+use crate::cmp::Ordering::{self, Less, Equal, Greater};
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use crate::intrinsics::copy_nonoverlapping;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use crate::intrinsics::copy;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use crate::intrinsics::write_bytes;
+
+mod non_null;
+#[stable(feature = "nonnull", since = "1.25.0")]
+pub use non_null::NonNull;
+
+mod unique;
+#[unstable(feature = "ptr_internals", issue = "0")]
+pub use unique::Unique;
+
+/// Executes the destructor (if any) of the pointed-to value.
+///
+/// This is semantically equivalent to calling [`ptr::read`] and discarding
+/// the result, but has the following advantages:
+///
+/// * It is *required* to use `drop_in_place` to drop unsized types like
+/// trait objects, because they can't be read out onto the stack and
+/// dropped normally.
+///
+/// * It is friendlier to the optimizer to do this over [`ptr::read`] when
+/// dropping manually allocated memory (e.g., when writing Box/Rc/Vec),
+/// as the compiler doesn't need to prove that it's sound to elide the
+/// copy.
+///
+/// [`ptr::read`]: ../ptr/fn.read.html
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `to_drop` must be [valid] for reads.
+///
+/// * `to_drop` must be properly aligned. See the example below for how to drop
+/// an unaligned pointer.
+///
+/// Additionally, if `T` is not [`Copy`], using the pointed-to value after
+/// calling `drop_in_place` can cause undefined behavior. Note that `*to_drop =
+/// foo` counts as a use because it will cause the value to be dropped
+/// again. [`write`] can be used to overwrite data without causing it to be
+/// dropped.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+/// [`Copy`]: ../marker/trait.Copy.html
+/// [`write`]: ../ptr/fn.write.html
+///
+/// # Examples
+///
+/// Manually remove the last item from a vector:
+///
+/// ```
+/// use std::ptr;
+/// use std::rc::Rc;
+///
+/// let last = Rc::new(1);
+/// let weak = Rc::downgrade(&last);
+///
+/// let mut v = vec![Rc::new(0), last];
+///
+/// unsafe {
+/// // Get a raw pointer to the last element in `v`.
+/// let ptr = &mut v[1] as *mut _;
+/// // Shorten `v` to prevent the last item from being dropped. We do that first,
+/// // to prevent issues if the `drop_in_place` below panics.
+/// v.set_len(1);
+/// // Without a call `drop_in_place`, the last item would never be dropped,
+/// // and the memory it manages would be leaked.
+/// ptr::drop_in_place(ptr);
+/// }
+///
+/// assert_eq!(v, &[0.into()]);
+///
+/// // Ensure that the last item was dropped.
+/// assert!(weak.upgrade().is_none());
+/// ```
+///
+/// Unaligned values cannot be dropped in place, they must be copied to an aligned
+/// location first:
+/// ```
+/// use std::ptr;
+/// use std::mem::{self, MaybeUninit};
+///
+/// unsafe fn drop_after_copy<T>(to_drop: *mut T) {
+/// let mut copy: MaybeUninit<T> = MaybeUninit::uninit();
+/// ptr::copy(to_drop, copy.as_mut_ptr(), 1);
+/// drop(copy.assume_init());
+/// }
+///
+/// #[repr(packed, C)]
+/// struct Packed {
+/// _padding: u8,
+/// unaligned: Vec<i32>,
+/// }
+///
+/// let mut p = Packed { _padding: 0, unaligned: vec![42] };
+/// unsafe {
+/// drop_after_copy(&mut p.unaligned as *mut _);
+/// mem::forget(p);
+/// }
+/// ```
+///
+/// Notice that the compiler performs this copy automatically when dropping packed structs,
+/// i.e., you do not usually have to worry about such issues unless you call `drop_in_place`
+/// manually.
+#[stable(feature = "drop_in_place", since = "1.8.0")]
+#[inline(always)]
+pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
+ real_drop_in_place(&mut *to_drop)
+}
+
+// The real `drop_in_place` -- the one that gets called implicitly when variables go
+// out of scope -- should have a safe reference and not a raw pointer as argument
+// type. When we drop a local variable, we access it with a pointer that behaves
+// like a safe reference; transmuting that to a raw pointer does not mean we can
+// actually access it with raw pointers.
+#[lang = "drop_in_place"]
+#[allow(unconditional_recursion)]
+unsafe fn real_drop_in_place<T: ?Sized>(to_drop: &mut T) {
+ // Code here does not matter - this is replaced by the
+ // real drop glue by the compiler.
+ real_drop_in_place(to_drop)
+}
+
+/// Creates a null raw pointer.
+///
+/// # Examples
+///
+/// ```
+/// use std::ptr;
+///
+/// let p: *const i32 = ptr::null();
+/// assert!(p.is_null());
+/// ```
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_promotable]
+pub const fn null<T>() -> *const T { 0 as *const T }
+
+/// Creates a null mutable raw pointer.
+///
+/// # Examples
+///
+/// ```
+/// use std::ptr;
+///
+/// let p: *mut i32 = ptr::null_mut();
+/// assert!(p.is_null());
+/// ```
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_promotable]
+pub const fn null_mut<T>() -> *mut T { 0 as *mut T }
+
+/// Swaps the values at two mutable locations of the same type, without
+/// deinitializing either.
+///
+/// But for the following two exceptions, this function is semantically
+/// equivalent to [`mem::swap`]:
+///
+/// * It operates on raw pointers instead of references. When references are
+/// available, [`mem::swap`] should be preferred.
+///
+/// * The two pointed-to values may overlap. If the values do overlap, then the
+/// overlapping region of memory from `x` will be used. This is demonstrated
+/// in the second example below.
+///
+/// [`mem::swap`]: ../mem/fn.swap.html
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * Both `x` and `y` must be [valid] for reads and writes.
+///
+/// * Both `x` and `y` must be properly aligned.
+///
+/// Note that even if `T` has size `0`, the pointers must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+///
+/// # Examples
+///
+/// Swapping two non-overlapping regions:
+///
+/// ```
+/// use std::ptr;
+///
+/// let mut array = [0, 1, 2, 3];
+///
+/// let x = array[0..].as_mut_ptr() as *mut [u32; 2]; // this is `array[0..2]`
+/// let y = array[2..].as_mut_ptr() as *mut [u32; 2]; // this is `array[2..4]`
+///
+/// unsafe {
+/// ptr::swap(x, y);
+/// assert_eq!([2, 3, 0, 1], array);
+/// }
+/// ```
+///
+/// Swapping two overlapping regions:
+///
+/// ```
+/// use std::ptr;
+///
+/// let mut array = [0, 1, 2, 3];
+///
+/// let x = array[0..].as_mut_ptr() as *mut [u32; 3]; // this is `array[0..3]`
+/// let y = array[1..].as_mut_ptr() as *mut [u32; 3]; // this is `array[1..4]`
+///
+/// unsafe {
+/// ptr::swap(x, y);
+/// // The indices `1..3` of the slice overlap between `x` and `y`.
+/// // Reasonable results would be for to them be `[2, 3]`, so that indices `0..3` are
+/// // `[1, 2, 3]` (matching `y` before the `swap`); or for them to be `[0, 1]`
+/// // so that indices `1..4` are `[0, 1, 2]` (matching `x` before the `swap`).
+/// // This implementation is defined to make the latter choice.
+/// assert_eq!([1, 0, 1, 2], array);
+/// }
+/// ```
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub unsafe fn swap<T>(x: *mut T, y: *mut T) {
+ // Give ourselves some scratch space to work with.
+ // We do not have to worry about drops: `MaybeUninit` does nothing when dropped.
+ let mut tmp = MaybeUninit::<T>::uninit();
+
+ // Perform the swap
+ copy_nonoverlapping(x, tmp.as_mut_ptr(), 1);
+ copy(y, x, 1); // `x` and `y` may overlap
+ copy_nonoverlapping(tmp.as_ptr(), y, 1);
+}
+
+/// Swaps `count * size_of::<T>()` bytes between the two regions of memory
+/// beginning at `x` and `y`. The two regions must *not* overlap.
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * Both `x` and `y` must be [valid] for reads and writes of `count *
+/// size_of::<T>()` bytes.
+///
+/// * Both `x` and `y` must be properly aligned.
+///
+/// * The region of memory beginning at `x` with a size of `count *
+/// size_of::<T>()` bytes must *not* overlap with the region of memory
+/// beginning at `y` with the same size.
+///
+/// Note that even if the effectively copied size (`count * size_of::<T>()`) is `0`,
+/// the pointers must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// use std::ptr;
+///
+/// let mut x = [1, 2, 3, 4];
+/// let mut y = [7, 8, 9];
+///
+/// unsafe {
+/// ptr::swap_nonoverlapping(x.as_mut_ptr(), y.as_mut_ptr(), 2);
+/// }
+///
+/// assert_eq!(x, [7, 8, 3, 4]);
+/// assert_eq!(y, [1, 2, 9]);
+/// ```
+#[inline]
+#[stable(feature = "swap_nonoverlapping", since = "1.27.0")]
+pub unsafe fn swap_nonoverlapping<T>(x: *mut T, y: *mut T, count: usize) {
+ let x = x as *mut u8;
+ let y = y as *mut u8;
+ let len = mem::size_of::<T>() * count;
+ swap_nonoverlapping_bytes(x, y, len)
+}
+
+#[inline]
+pub(crate) unsafe fn swap_nonoverlapping_one<T>(x: *mut T, y: *mut T) {
+ // For types smaller than the block optimization below,
+ // just swap directly to avoid pessimizing codegen.
+ if mem::size_of::<T>() < 32 {
+ let z = read(x);
+ copy_nonoverlapping(y, x, 1);
+ write(y, z);
+ } else {
+ swap_nonoverlapping(x, y, 1);
+ }
+}
+
+#[inline]
+unsafe fn swap_nonoverlapping_bytes(x: *mut u8, y: *mut u8, len: usize) {
+ // The approach here is to utilize simd to swap x & y efficiently. Testing reveals
+ // that swapping either 32 bytes or 64 bytes at a time is most efficient for Intel
+ // Haswell E processors. LLVM is more able to optimize if we give a struct a
+ // #[repr(simd)], even if we don't actually use this struct directly.
+ //
+ // FIXME repr(simd) broken on emscripten and redox
+ #[cfg_attr(not(any(target_os = "emscripten", target_os = "redox")), repr(simd))]
+ struct Block(u64, u64, u64, u64);
+ struct UnalignedBlock(u64, u64, u64, u64);
+
+ let block_size = mem::size_of::<Block>();
+
+ // Loop through x & y, copying them `Block` at a time
+ // The optimizer should unroll the loop fully for most types
+ // N.B. We can't use a for loop as the `range` impl calls `mem::swap` recursively
+ let mut i = 0;
+ while i + block_size <= len {
+ // Create some uninitialized memory as scratch space
+ // Declaring `t` here avoids aligning the stack when this loop is unused
+ let mut t = mem::MaybeUninit::<Block>::uninit();
+ let t = t.as_mut_ptr() as *mut u8;
+ let x = x.add(i);
+ let y = y.add(i);
+
+ // Swap a block of bytes of x & y, using t as a temporary buffer
+ // This should be optimized into efficient SIMD operations where available
+ copy_nonoverlapping(x, t, block_size);
+ copy_nonoverlapping(y, x, block_size);
+ copy_nonoverlapping(t, y, block_size);
+ i += block_size;
+ }
+
+ if i < len {
+ // Swap any remaining bytes
+ let mut t = mem::MaybeUninit::<UnalignedBlock>::uninit();
+ let rem = len - i;
+
+ let t = t.as_mut_ptr() as *mut u8;
+ let x = x.add(i);
+ let y = y.add(i);
+
+ copy_nonoverlapping(x, t, rem);
+ copy_nonoverlapping(y, x, rem);
+ copy_nonoverlapping(t, y, rem);
+ }
+}
+
+/// Moves `src` into the pointed `dst`, returning the previous `dst` value.
+///
+/// Neither value is dropped.
+///
+/// This function is semantically equivalent to [`mem::replace`] except that it
+/// operates on raw pointers instead of references. When references are
+/// available, [`mem::replace`] should be preferred.
+///
+/// [`mem::replace`]: ../mem/fn.replace.html
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `dst` must be [valid] for writes.
+///
+/// * `dst` must be properly aligned.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+///
+/// # Examples
+///
+/// ```
+/// use std::ptr;
+///
+/// let mut rust = vec!['b', 'u', 's', 't'];
+///
+/// // `mem::replace` would have the same effect without requiring the unsafe
+/// // block.
+/// let b = unsafe {
+/// ptr::replace(&mut rust[0], 'r')
+/// };
+///
+/// assert_eq!(b, 'b');
+/// assert_eq!(rust, &['r', 'u', 's', 't']);
+/// ```
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub unsafe fn replace<T>(dst: *mut T, mut src: T) -> T {
+ mem::swap(&mut *dst, &mut src); // cannot overlap
+ src
+}
+
+/// Reads the value from `src` without moving it. This leaves the
+/// memory in `src` unchanged.
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `src` must be [valid] for reads.
+///
+/// * `src` must be properly aligned. Use [`read_unaligned`] if this is not the
+/// case.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let x = 12;
+/// let y = &x as *const i32;
+///
+/// unsafe {
+/// assert_eq!(std::ptr::read(y), 12);
+/// }
+/// ```
+///
+/// Manually implement [`mem::swap`]:
+///
+/// ```
+/// use std::ptr;
+///
+/// fn swap<T>(a: &mut T, b: &mut T) {
+/// unsafe {
+/// // Create a bitwise copy of the value at `a` in `tmp`.
+/// let tmp = ptr::read(a);
+///
+/// // Exiting at this point (either by explicitly returning or by
+/// // calling a function which panics) would cause the value in `tmp` to
+/// // be dropped while the same value is still referenced by `a`. This
+/// // could trigger undefined behavior if `T` is not `Copy`.
+///
+/// // Create a bitwise copy of the value at `b` in `a`.
+/// // This is safe because mutable references cannot alias.
+/// ptr::copy_nonoverlapping(b, a, 1);
+///
+/// // As above, exiting here could trigger undefined behavior because
+/// // the same value is referenced by `a` and `b`.
+///
+/// // Move `tmp` into `b`.
+/// ptr::write(b, tmp);
+///
+/// // `tmp` has been moved (`write` takes ownership of its second argument),
+/// // so nothing is dropped implicitly here.
+/// }
+/// }
+///
+/// let mut foo = "foo".to_owned();
+/// let mut bar = "bar".to_owned();
+///
+/// swap(&mut foo, &mut bar);
+///
+/// assert_eq!(foo, "bar");
+/// assert_eq!(bar, "foo");
+/// ```
+///
+/// ## Ownership of the Returned Value
+///
+/// `read` creates a bitwise copy of `T`, regardless of whether `T` is [`Copy`].
+/// If `T` is not [`Copy`], using both the returned value and the value at
+/// `*src` can violate memory safety. Note that assigning to `*src` counts as a
+/// use because it will attempt to drop the value at `*src`.
+///
+/// [`write`] can be used to overwrite data without causing it to be dropped.
+///
+/// ```
+/// use std::ptr;
+///
+/// let mut s = String::from("foo");
+/// unsafe {
+/// // `s2` now points to the same underlying memory as `s`.
+/// let mut s2: String = ptr::read(&s);
+///
+/// assert_eq!(s2, "foo");
+///
+/// // Assigning to `s2` causes its original value to be dropped. Beyond
+/// // this point, `s` must no longer be used, as the underlying memory has
+/// // been freed.
+/// s2 = String::default();
+/// assert_eq!(s2, "");
+///
+/// // Assigning to `s` would cause the old value to be dropped again,
+/// // resulting in undefined behavior.
+/// // s = String::from("bar"); // ERROR
+///
+/// // `ptr::write` can be used to overwrite a value without dropping it.
+/// ptr::write(&mut s, String::from("bar"));
+/// }
+///
+/// assert_eq!(s, "bar");
+/// ```
+///
+/// [`mem::swap`]: ../mem/fn.swap.html
+/// [valid]: ../ptr/index.html#safety
+/// [`Copy`]: ../marker/trait.Copy.html
+/// [`read_unaligned`]: ./fn.read_unaligned.html
+/// [`write`]: ./fn.write.html
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub unsafe fn read<T>(src: *const T) -> T {
+ let mut tmp = MaybeUninit::<T>::uninit();
+ copy_nonoverlapping(src, tmp.as_mut_ptr(), 1);
+ tmp.assume_init()
+}
+
+/// Reads the value from `src` without moving it. This leaves the
+/// memory in `src` unchanged.
+///
+/// Unlike [`read`], `read_unaligned` works with unaligned pointers.
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `src` must be [valid] for reads.
+///
+/// Like [`read`], `read_unaligned` creates a bitwise copy of `T`, regardless of
+/// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the returned
+/// value and the value at `*src` can [violate memory safety][read-ownership].
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL.
+///
+/// [`Copy`]: ../marker/trait.Copy.html
+/// [`read`]: ./fn.read.html
+/// [`write_unaligned`]: ./fn.write_unaligned.html
+/// [read-ownership]: ./fn.read.html#ownership-of-the-returned-value
+/// [valid]: ../ptr/index.html#safety
+///
+/// # Examples
+///
+/// Access members of a packed struct by reference:
+///
+/// ```
+/// use std::ptr;
+///
+/// #[repr(packed, C)]
+/// struct Packed {
+/// _padding: u8,
+/// unaligned: u32,
+/// }
+///
+/// let x = Packed {
+/// _padding: 0x00,
+/// unaligned: 0x01020304,
+/// };
+///
+/// let v = unsafe {
+/// // Take the address of a 32-bit integer which is not aligned.
+/// // This must be done as a raw pointer; unaligned references are invalid.
+/// let unaligned = &x.unaligned as *const u32;
+///
+/// // Dereferencing normally will emit an aligned load instruction,
+/// // causing undefined behavior.
+/// // let v = *unaligned; // ERROR
+///
+/// // Instead, use `read_unaligned` to read improperly aligned values.
+/// let v = ptr::read_unaligned(unaligned);
+///
+/// v
+/// };
+///
+/// // Accessing unaligned values directly is safe.
+/// assert!(x.unaligned == v);
+/// ```
+#[inline]
+#[stable(feature = "ptr_unaligned", since = "1.17.0")]
+pub unsafe fn read_unaligned<T>(src: *const T) -> T {
+ let mut tmp = MaybeUninit::<T>::uninit();
+ copy_nonoverlapping(src as *const u8,
+ tmp.as_mut_ptr() as *mut u8,
+ mem::size_of::<T>());
+ tmp.assume_init()
+}
+
+/// Overwrites a memory location with the given value without reading or
+/// dropping the old value.
+///
+/// `write` does not drop the contents of `dst`. This is safe, but it could leak
+/// allocations or resources, so care should be taken not to overwrite an object
+/// that should be dropped.
+///
+/// Additionally, it does not drop `src`. Semantically, `src` is moved into the
+/// location pointed to by `dst`.
+///
+/// This is appropriate for initializing uninitialized memory, or overwriting
+/// memory that has previously been [`read`] from.
+///
+/// [`read`]: ./fn.read.html
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `dst` must be [valid] for writes.
+///
+/// * `dst` must be properly aligned. Use [`write_unaligned`] if this is not the
+/// case.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+/// [`write_unaligned`]: ./fn.write_unaligned.html
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let mut x = 0;
+/// let y = &mut x as *mut i32;
+/// let z = 12;
+///
+/// unsafe {
+/// std::ptr::write(y, z);
+/// assert_eq!(std::ptr::read(y), 12);
+/// }
+/// ```
+///
+/// Manually implement [`mem::swap`]:
+///
+/// ```
+/// use std::ptr;
+///
+/// fn swap<T>(a: &mut T, b: &mut T) {
+/// unsafe {
+/// // Create a bitwise copy of the value at `a` in `tmp`.
+/// let tmp = ptr::read(a);
+///
+/// // Exiting at this point (either by explicitly returning or by
+/// // calling a function which panics) would cause the value in `tmp` to
+/// // be dropped while the same value is still referenced by `a`. This
+/// // could trigger undefined behavior if `T` is not `Copy`.
+///
+/// // Create a bitwise copy of the value at `b` in `a`.
+/// // This is safe because mutable references cannot alias.
+/// ptr::copy_nonoverlapping(b, a, 1);
+///
+/// // As above, exiting here could trigger undefined behavior because
+/// // the same value is referenced by `a` and `b`.
+///
+/// // Move `tmp` into `b`.
+/// ptr::write(b, tmp);
+///
+/// // `tmp` has been moved (`write` takes ownership of its second argument),
+/// // so nothing is dropped implicitly here.
+/// }
+/// }
+///
+/// let mut foo = "foo".to_owned();
+/// let mut bar = "bar".to_owned();
+///
+/// swap(&mut foo, &mut bar);
+///
+/// assert_eq!(foo, "bar");
+/// assert_eq!(bar, "foo");
+/// ```
+///
+/// [`mem::swap`]: ../mem/fn.swap.html
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub unsafe fn write<T>(dst: *mut T, src: T) {
+ intrinsics::move_val_init(&mut *dst, src)
+}
+
+/// Overwrites a memory location with the given value without reading or
+/// dropping the old value.
+///
+/// Unlike [`write`], the pointer may be unaligned.
+///
+/// `write_unaligned` does not drop the contents of `dst`. This is safe, but it
+/// could leak allocations or resources, so care should be taken not to overwrite
+/// an object that should be dropped.
+///
+/// Additionally, it does not drop `src`. Semantically, `src` is moved into the
+/// location pointed to by `dst`.
+///
+/// This is appropriate for initializing uninitialized memory, or overwriting
+/// memory that has previously been read with [`read_unaligned`].
+///
+/// [`write`]: ./fn.write.html
+/// [`read_unaligned`]: ./fn.read_unaligned.html
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `dst` must be [valid] for writes.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL.
+///
+/// [valid]: ../ptr/index.html#safety
+///
+/// # Examples
+///
+/// Access fields in a packed struct:
+///
+/// ```
+/// use std::{mem, ptr};
+///
+/// #[repr(packed, C)]
+/// #[derive(Default)]
+/// struct Packed {
+/// _padding: u8,
+/// unaligned: u32,
+/// }
+///
+/// let v = 0x01020304;
+/// let mut x: Packed = unsafe { mem::zeroed() };
+///
+/// unsafe {
+/// // Take a reference to a 32-bit integer which is not aligned.
+/// let unaligned = &mut x.unaligned as *mut u32;
+///
+/// // Dereferencing normally will emit an aligned store instruction,
+/// // causing undefined behavior because the pointer is not aligned.
+/// // *unaligned = v; // ERROR
+///
+/// // Instead, use `write_unaligned` to write improperly aligned values.
+/// ptr::write_unaligned(unaligned, v);
+/// }
+///
+/// // Accessing unaligned values directly is safe.
+/// assert!(x.unaligned == v);
+/// ```
+#[inline]
+#[stable(feature = "ptr_unaligned", since = "1.17.0")]
+pub unsafe fn write_unaligned<T>(dst: *mut T, src: T) {
+ copy_nonoverlapping(&src as *const T as *const u8,
+ dst as *mut u8,
+ mem::size_of::<T>());
+ mem::forget(src);
+}
+
+/// Performs a volatile read of the value from `src` without moving it. This
+/// leaves the memory in `src` 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.
+///
+/// [`write_volatile`]: ./fn.write_volatile.html
+///
+/// # Notes
+///
+/// Rust does not currently have a rigorously and formally defined memory model,
+/// so the precise semantics of what "volatile" means here is subject to change
+/// over time. That being said, the semantics will almost always end up pretty
+/// similar to [C11's definition of volatile][c11].
+///
+/// The compiler shouldn't change the relative order or number of volatile
+/// memory operations. However, volatile memory operations on zero-sized types
+/// (e.g., if a zero-sized type is passed to `read_volatile`) are noops
+/// and may be ignored.
+///
+/// [c11]: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `src` must be [valid] for reads.
+///
+/// * `src` must be properly aligned.
+///
+/// Like [`read`], `read_volatile` creates a bitwise copy of `T`, regardless of
+/// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the returned
+/// value and the value at `*src` can [violate memory safety][read-ownership].
+/// However, storing non-[`Copy`] types in volatile memory is almost certainly
+/// incorrect.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+/// [`Copy`]: ../marker/trait.Copy.html
+/// [`read`]: ./fn.read.html
+/// [read-ownership]: ./fn.read.html#ownership-of-the-returned-value
+///
+/// Just like in C, whether an operation is volatile has no bearing whatsoever
+/// on questions involving concurrent access from multiple threads. Volatile
+/// accesses behave exactly like non-atomic accesses in that regard. In particular,
+/// a race between a `read_volatile` and any write operation to the same location
+/// is undefined behavior.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let x = 12;
+/// let y = &x as *const i32;
+///
+/// unsafe {
+/// assert_eq!(std::ptr::read_volatile(y), 12);
+/// }
+/// ```
+#[inline]
+#[stable(feature = "volatile", since = "1.9.0")]
+pub unsafe fn read_volatile<T>(src: *const T) -> T {
+ intrinsics::volatile_load(src)
+}
+
+/// 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.
+///
+/// `write_volatile` does not drop the contents of `dst`. This is safe, but it
+/// could leak allocations or resources, so care should be taken not to overwrite
+/// an object that should be dropped.
+///
+/// Additionally, it does not drop `src`. Semantically, `src` is moved into the
+/// location pointed to by `dst`.
+///
+/// [`read_volatile`]: ./fn.read_volatile.html
+///
+/// # Notes
+///
+/// Rust does not currently have a rigorously and formally defined memory model,
+/// so the precise semantics of what "volatile" means here is subject to change
+/// over time. That being said, the semantics will almost always end up pretty
+/// similar to [C11's definition of volatile][c11].
+///
+/// The compiler shouldn't change the relative order or number of volatile
+/// memory operations. However, volatile memory operations on zero-sized types
+/// (e.g., if a zero-sized type is passed to `write_volatile`) are noops
+/// and may be ignored.
+///
+/// [c11]: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `dst` must be [valid] for writes.
+///
+/// * `dst` must be properly aligned.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+///
+/// Just like in C, whether an operation is volatile has no bearing whatsoever
+/// on questions involving concurrent access from multiple threads. Volatile
+/// accesses behave exactly like non-atomic accesses in that regard. In particular,
+/// a race between a `write_volatile` and any other operation (reading or writing)
+/// on the same location is undefined behavior.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let mut x = 0;
+/// let y = &mut x as *mut i32;
+/// let z = 12;
+///
+/// unsafe {
+/// std::ptr::write_volatile(y, z);
+/// assert_eq!(std::ptr::read_volatile(y), 12);
+/// }
+/// ```
+#[inline]
+#[stable(feature = "volatile", since = "1.9.0")]
+pub unsafe fn write_volatile<T>(dst: *mut T, src: T) {
+ intrinsics::volatile_store(dst, src);
+}
+
+#[lang = "const_ptr"]
+impl<T: ?Sized> *const T {
+ /// Returns `true` if the pointer is null.
+ ///
+ /// Note that unsized types have many possible null pointers, as only the
+ /// raw data pointer is considered, not their length, vtable, etc.
+ /// Therefore, two pointers that are null may still not compare equal to
+ /// each other.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s: &str = "Follow the rabbit";
+ /// let ptr: *const u8 = s.as_ptr();
+ /// assert!(!ptr.is_null());
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[inline]
+ pub fn is_null(self) -> bool {
+ // Compare via a cast to a thin pointer, so fat pointers are only
+ // considering their "data" part for null-ness.
+ (self as *const u8) == null()
+ }
+
+ /// Cast to a pointer to a different type
+ #[unstable(feature = "ptr_cast", issue = "60602")]
+ #[inline]
+ pub const fn cast<U>(self) -> *const U {
+ self as _
+ }
+
+ /// Returns `None` if the pointer is null, or else returns a reference to
+ /// the value wrapped in `Some`.
+ ///
+ /// # Safety
+ ///
+ /// While this method and its mutable counterpart are useful for
+ /// null-safety, it is important to note that this is still an unsafe
+ /// operation because the returned value could be pointing to invalid
+ /// memory.
+ ///
+ /// Additionally, the lifetime `'a` returned is arbitrarily chosen and does
+ /// not necessarily reflect the actual lifetime of the data.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let ptr: *const u8 = &10u8 as *const u8;
+ ///
+ /// unsafe {
+ /// if let Some(val_back) = ptr.as_ref() {
+ /// println!("We got back the value: {}!", val_back);
+ /// }
+ /// }
+ /// ```
+ ///
+ /// # Null-unchecked version
+ ///
+ /// If you are sure the pointer can never be null and are looking for some kind of
+ /// `as_ref_unchecked` that returns the `&T` instead of `Option<&T>`, know that you can
+ /// dereference the pointer directly.
+ ///
+ /// ```
+ /// let ptr: *const u8 = &10u8 as *const u8;
+ ///
+ /// unsafe {
+ /// let val_back = &*ptr;
+ /// println!("We got back the value: {}!", val_back);
+ /// }
+ /// ```
+ #[stable(feature = "ptr_as_ref", since = "1.9.0")]
+ #[inline]
+ pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
+ if self.is_null() {
+ None
+ } else {
+ Some(&*self)
+ }
+ }
+
+ /// 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.
+ ///
+ /// Consider using `wrapping_offset` instead if these constraints are
+ /// difficult to satisfy. The only advantage of this method is that it
+ /// enables more aggressive compiler optimizations.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let s: &str = "123";
+ /// let ptr: *const u8 = s.as_ptr();
+ ///
+ /// unsafe {
+ /// println!("{}", *ptr.offset(1) as char);
+ /// println!("{}", *ptr.offset(2) as char);
+ /// }
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[inline]
+ pub unsafe fn offset(self, count: isize) -> *const T where T: Sized {
+ intrinsics::offset(self, count)
+ }
+
+ /// Calculates the offset from a pointer using wrapping arithmetic.
+ ///
+ /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+ /// offset of `3 * size_of::<T>()` bytes.
+ ///
+ /// # Safety
+ ///
+ /// The resulting pointer does not need to be in bounds, but it is
+ /// potentially hazardous to dereference (which requires `unsafe`).
+ /// In particular, the resulting pointer may *not* be used to access a
+ /// different allocated object than the one `self` points to. In other
+ /// words, `x.wrapping_offset(y.wrapping_offset_from(x))` is
+ /// *not* the same as `y`, and dereferencing it is undefined behavior
+ /// unless `x` and `y` point into the same allocated object.
+ ///
+ /// Always use `.offset(count)` instead when possible, because `offset`
+ /// allows the compiler to optimize better. If you need to cross object
+ /// boundaries, cast the pointer to an integer and do the arithmetic there.
+ ///
+ /// # 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_offset(6);
+ ///
+ /// // This loop prints "1, 3, 5, "
+ /// while ptr != end_rounded_up {
+ /// unsafe {
+ /// print!("{}, ", *ptr);
+ /// }
+ /// ptr = ptr.wrapping_offset(step);
+ /// }
+ /// ```
+ #[stable(feature = "ptr_wrapping_offset", since = "1.16.0")]
+ #[inline]
+ pub fn wrapping_offset(self, count: isize) -> *const T where T: Sized {
+ unsafe {
+ intrinsics::arith_offset(self, count)
+ }
+ }
+
+ /// 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
+ /// [`wrapping_offset_from`]: #method.wrapping_offset_from
+ ///
+ /// # 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.
+ ///
+ /// * The distance between the pointers, **in bytes**, cannot overflow an `isize`.
+ ///
+ /// * The distance between the pointers, in bytes, must be an exact multiple
+ /// of the size of `T`.
+ ///
+ /// * The distance being in bounds cannot rely on "wrapping around" the address space.
+ ///
+ /// The compiler and standard library generally try 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
+ /// `ptr_into_vec.offset_from(vec.as_ptr())` 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_offset_from`] instead if these constraints are
+ /// difficult to satisfy. The only advantage of this method is that it
+ /// enables more aggressive compiler optimizations.
+ ///
+ /// # Panics
+ ///
+ /// This function panics if `T` is a Zero-Sized Type ("ZST").
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// #![feature(ptr_offset_from)]
+ ///
+ /// let a = [0; 5];
+ /// let ptr1: *const i32 = &a[1];
+ /// let ptr2: *const i32 = &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);
+ /// }
+ /// ```
+ #[unstable(feature = "ptr_offset_from", issue = "41079")]
+ #[inline]
+ pub unsafe fn offset_from(self, origin: *const T) -> isize where T: Sized {
+ let pointee_size = mem::size_of::<T>();
+ assert!(0 < pointee_size && pointee_size <= isize::max_value() as usize);
+
+ // This is the same sequence that Clang emits for pointer subtraction.
+ // It can be neither `nsw` nor `nuw` because the input is treated as
+ // unsigned but then the output is treated as signed, so neither works.
+ let d = isize::wrapping_sub(self as _, origin as _);
+ intrinsics::exact_div(d, pointee_size as _)
+ }
+
+ /// 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>()`.
+ ///
+ /// If the address different between the two pointers is not a multiple of
+ /// `mem::size_of::<T>()` then the result of the division is rounded towards
+ /// zero.
+ ///
+ /// Though this method is safe for any two pointers, note that its result
+ /// will be mostly useless if the two pointers aren't into the same allocated
+ /// object, for example if they point to two different local variables.
+ ///
+ /// # Panics
+ ///
+ /// This function panics if `T` is a zero-sized type.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// #![feature(ptr_wrapping_offset_from)]
+ ///
+ /// let a = [0; 5];
+ /// let ptr1: *const i32 = &a[1];
+ /// let ptr2: *const i32 = &a[3];
+ /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
+ /// assert_eq!(ptr1.wrapping_offset_from(ptr2), -2);
+ /// assert_eq!(ptr1.wrapping_offset(2), ptr2);
+ /// assert_eq!(ptr2.wrapping_offset(-2), ptr1);
+ ///
+ /// let ptr1: *const i32 = 3 as _;
+ /// let ptr2: *const i32 = 13 as _;
+ /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
+ /// ```
+ #[unstable(feature = "ptr_wrapping_offset_from", issue = "41079")]
+ #[inline]
+ pub fn wrapping_offset_from(self, origin: *const T) -> isize where T: Sized {
+ let pointee_size = mem::size_of::<T>();
+ assert!(0 < pointee_size && pointee_size <= isize::max_value() as usize);
+
+ let d = isize::wrapping_sub(self as _, origin as _);
+ d.wrapping_div(pointee_size as _)
+ }
+
+ /// 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.
+ ///
+ /// Consider using `wrapping_offset` instead if these constraints are
+ /// difficult to satisfy. The only advantage of this method is that it
+ /// enables more aggressive compiler optimizations.
+ ///
+ /// # 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")]
+ #[inline]
+ pub unsafe fn add(self, count: usize) -> Self
+ where T: Sized,
+ {
+ 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.
+ ///
+ /// * 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_offset` instead if these constraints are
+ /// difficult to satisfy. The only advantage of this method is that it
+ /// enables more aggressive compiler optimizations.
+ ///
+ /// # 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")]
+ #[inline]
+ pub unsafe fn sub(self, count: usize) -> Self
+ where T: Sized,
+ {
+ 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
+ ///
+ /// The resulting pointer does not need to be in bounds, but it is
+ /// potentially hazardous to dereference (which requires `unsafe`).
+ ///
+ /// Always use `.add(count)` instead when possible, because `add`
+ /// allows the compiler to optimize better.
+ ///
+ /// # 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")]
+ #[inline]
+ pub 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_sub())`)
+ ///
+ /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+ /// offset of `3 * size_of::<T>()` bytes.
+ ///
+ /// # Safety
+ ///
+ /// The resulting pointer does not need to be in bounds, but it is
+ /// potentially hazardous to dereference (which requires `unsafe`).
+ ///
+ /// Always use `.sub(count)` instead when possible, because `sub`
+ /// allows the compiler to optimize better.
+ ///
+ /// # 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")]
+ #[inline]
+ pub fn wrapping_sub(self, count: usize) -> Self
+ where T: Sized,
+ {
+ self.wrapping_offset((count as isize).wrapping_neg())
+ }
+
+ /// 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`]: ./ptr/fn.read.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn read(self) -> T
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.read_volatile.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn read_volatile(self) -> T
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.read_unaligned.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn read_unaligned(self) -> T
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.copy.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn copy_to(self, dest: *mut T, count: usize)
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.copy_nonoverlapping.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn copy_to_nonoverlapping(self, dest: *mut T, count: usize)
+ where T: Sized,
+ {
+ copy_nonoverlapping(self, dest, count)
+ }
+
+ /// 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_value()`.
+ ///
+ /// The offset is expressed in number of `T` elements, and not bytes. The value returned can be
+ /// used with the `offset` or `offset_to` methods.
+ ///
+ /// There are no guarantees whatsover 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[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");
+ }
+ unsafe {
+ align_offset(self, align)
+ }
+ }
+}
+
+
+#[lang = "mut_ptr"]
+impl<T: ?Sized> *mut T {
+ /// Returns `true` if the pointer is null.
+ ///
+ /// Note that unsized types have many possible null pointers, as only the
+ /// raw data pointer is considered, not their length, vtable, etc.
+ /// Therefore, two pointers that are null may still not compare equal to
+ /// each other.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = [1, 2, 3];
+ /// let ptr: *mut u32 = s.as_mut_ptr();
+ /// assert!(!ptr.is_null());
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[inline]
+ pub fn is_null(self) -> bool {
+ // Compare via a cast to a thin pointer, so fat pointers are only
+ // considering their "data" part for null-ness.
+ (self as *mut u8) == null_mut()
+ }
+
+ /// Cast to a pointer to a different type
+ #[unstable(feature = "ptr_cast", issue = "60602")]
+ #[inline]
+ pub const fn cast<U>(self) -> *mut U {
+ self as _
+ }
+
+ /// Returns `None` if the pointer is null, or else returns a reference to
+ /// the value wrapped in `Some`.
+ ///
+ /// # Safety
+ ///
+ /// While this method and its mutable counterpart are useful for
+ /// null-safety, it is important to note that this is still an unsafe
+ /// operation because the returned value could be pointing to invalid
+ /// memory.
+ ///
+ /// Additionally, the lifetime `'a` returned is arbitrarily chosen and does
+ /// not necessarily reflect the actual lifetime of the data.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let ptr: *mut u8 = &mut 10u8 as *mut u8;
+ ///
+ /// unsafe {
+ /// if let Some(val_back) = ptr.as_ref() {
+ /// println!("We got back the value: {}!", val_back);
+ /// }
+ /// }
+ /// ```
+ ///
+ /// # Null-unchecked version
+ ///
+ /// If you are sure the pointer can never be null and are looking for some kind of
+ /// `as_ref_unchecked` that returns the `&T` instead of `Option<&T>`, know that you can
+ /// dereference the pointer directly.
+ ///
+ /// ```
+ /// let ptr: *mut u8 = &mut 10u8 as *mut u8;
+ ///
+ /// unsafe {
+ /// let val_back = &*ptr;
+ /// println!("We got back the value: {}!", val_back);
+ /// }
+ /// ```
+ #[stable(feature = "ptr_as_ref", since = "1.9.0")]
+ #[inline]
+ pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
+ if self.is_null() {
+ None
+ } else {
+ Some(&*self)
+ }
+ }
+
+ /// 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.
+ ///
+ /// Consider using `wrapping_offset` instead if these constraints are
+ /// difficult to satisfy. The only advantage of this method is that it
+ /// enables more aggressive compiler optimizations.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = [1, 2, 3];
+ /// let ptr: *mut u32 = s.as_mut_ptr();
+ ///
+ /// unsafe {
+ /// println!("{}", *ptr.offset(1));
+ /// println!("{}", *ptr.offset(2));
+ /// }
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[inline]
+ pub unsafe fn offset(self, count: isize) -> *mut T where T: Sized {
+ intrinsics::offset(self, count) as *mut T
+ }
+
+ /// Calculates the offset from a pointer using wrapping arithmetic.
+ /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+ /// offset of `3 * size_of::<T>()` bytes.
+ ///
+ /// # Safety
+ ///
+ /// The resulting pointer does not need to be in bounds, but it is
+ /// potentially hazardous to dereference (which requires `unsafe`).
+ /// In particular, the resulting pointer may *not* be used to access a
+ /// different allocated object than the one `self` points to. In other
+ /// words, `x.wrapping_offset(y.wrapping_offset_from(x))` is
+ /// *not* the same as `y`, and dereferencing it is undefined behavior
+ /// unless `x` and `y` point into the same allocated object.
+ ///
+ /// Always use `.offset(count)` instead when possible, because `offset`
+ /// allows the compiler to optimize better. If you need to cross object
+ /// boundaries, cast the pointer to an integer and do the arithmetic there.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// // Iterate using a raw pointer in increments of two elements
+ /// let mut data = [1u8, 2, 3, 4, 5];
+ /// let mut ptr: *mut u8 = data.as_mut_ptr();
+ /// let step = 2;
+ /// let end_rounded_up = ptr.wrapping_offset(6);
+ ///
+ /// while ptr != end_rounded_up {
+ /// unsafe {
+ /// *ptr = 0;
+ /// }
+ /// ptr = ptr.wrapping_offset(step);
+ /// }
+ /// assert_eq!(&data, &[0, 2, 0, 4, 0]);
+ /// ```
+ #[stable(feature = "ptr_wrapping_offset", since = "1.16.0")]
+ #[inline]
+ pub fn wrapping_offset(self, count: isize) -> *mut T where T: Sized {
+ unsafe {
+ intrinsics::arith_offset(self, count) as *mut T
+ }
+ }
+
+ /// Returns `None` if the pointer is null, or else returns a mutable
+ /// reference to the value wrapped in `Some`.
+ ///
+ /// # Safety
+ ///
+ /// As with `as_ref`, this is unsafe because it cannot verify the validity
+ /// of the returned pointer, nor can it ensure that the lifetime `'a`
+ /// returned is indeed a valid lifetime for the contained data.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// let mut s = [1, 2, 3];
+ /// let ptr: *mut u32 = s.as_mut_ptr();
+ /// let first_value = unsafe { ptr.as_mut().unwrap() };
+ /// *first_value = 4;
+ /// println!("{:?}", s); // It'll print: "[4, 2, 3]".
+ /// ```
+ #[stable(feature = "ptr_as_ref", since = "1.9.0")]
+ #[inline]
+ pub unsafe fn as_mut<'a>(self) -> Option<&'a mut T> {
+ if self.is_null() {
+ None
+ } else {
+ Some(&mut *self)
+ }
+ }
+
+ /// 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
+ /// [`wrapping_offset_from`]: #method.wrapping_offset_from-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.
+ ///
+ /// * The distance between the pointers, **in bytes**, cannot overflow an `isize`.
+ ///
+ /// * The distance between the pointers, in bytes, must be an exact multiple
+ /// of the size of `T`.
+ ///
+ /// * The distance being in bounds cannot rely on "wrapping around" the address space.
+ ///
+ /// The compiler and standard library generally try 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
+ /// `ptr_into_vec.offset_from(vec.as_ptr())` 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_offset_from`] instead if these constraints are
+ /// difficult to satisfy. The only advantage of this method is that it
+ /// enables more aggressive compiler optimizations.
+ ///
+ /// # Panics
+ ///
+ /// This function panics if `T` is a Zero-Sized Type ("ZST").
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// #![feature(ptr_offset_from)]
+ ///
+ /// 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);
+ /// }
+ /// ```
+ #[unstable(feature = "ptr_offset_from", issue = "41079")]
+ #[inline]
+ pub unsafe fn offset_from(self, origin: *const T) -> isize where T: Sized {
+ (self as *const T).offset_from(origin)
+ }
+
+ /// 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>()`.
+ ///
+ /// If the address different between the two pointers is not a multiple of
+ /// `mem::size_of::<T>()` then the result of the division is rounded towards
+ /// zero.
+ ///
+ /// Though this method is safe for any two pointers, note that its result
+ /// will be mostly useless if the two pointers aren't into the same allocated
+ /// object, for example if they point to two different local variables.
+ ///
+ /// # Panics
+ ///
+ /// This function panics if `T` is a zero-sized type.
+ ///
+ /// # Examples
+ ///
+ /// Basic usage:
+ ///
+ /// ```
+ /// #![feature(ptr_wrapping_offset_from)]
+ ///
+ /// let mut a = [0; 5];
+ /// let ptr1: *mut i32 = &mut a[1];
+ /// let ptr2: *mut i32 = &mut a[3];
+ /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
+ /// assert_eq!(ptr1.wrapping_offset_from(ptr2), -2);
+ /// assert_eq!(ptr1.wrapping_offset(2), ptr2);
+ /// assert_eq!(ptr2.wrapping_offset(-2), ptr1);
+ ///
+ /// let ptr1: *mut i32 = 3 as _;
+ /// let ptr2: *mut i32 = 13 as _;
+ /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
+ /// ```
+ #[unstable(feature = "ptr_wrapping_offset_from", issue = "41079")]
+ #[inline]
+ pub fn wrapping_offset_from(self, origin: *const T) -> isize where T: Sized {
+ (self as *const T).wrapping_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.
+ ///
+ /// * 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_offset` instead if these constraints are
+ /// difficult to satisfy. The only advantage of this method is that it
+ /// enables more aggressive compiler optimizations.
+ ///
+ /// # 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")]
+ #[inline]
+ pub unsafe fn add(self, count: usize) -> Self
+ where T: Sized,
+ {
+ 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.
+ ///
+ /// * 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_offset` instead if these constraints are
+ /// difficult to satisfy. The only advantage of this method is that it
+ /// enables more aggressive compiler optimizations.
+ ///
+ /// # 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")]
+ #[inline]
+ pub unsafe fn sub(self, count: usize) -> Self
+ where T: Sized,
+ {
+ 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
+ ///
+ /// The resulting pointer does not need to be in bounds, but it is
+ /// potentially hazardous to dereference (which requires `unsafe`).
+ ///
+ /// Always use `.add(count)` instead when possible, because `add`
+ /// allows the compiler to optimize better.
+ ///
+ /// # 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")]
+ #[inline]
+ pub 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_sub())`)
+ ///
+ /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+ /// offset of `3 * size_of::<T>()` bytes.
+ ///
+ /// # Safety
+ ///
+ /// The resulting pointer does not need to be in bounds, but it is
+ /// potentially hazardous to dereference (which requires `unsafe`).
+ ///
+ /// Always use `.sub(count)` instead when possible, because `sub`
+ /// allows the compiler to optimize better.
+ ///
+ /// # 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")]
+ #[inline]
+ pub fn wrapping_sub(self, count: usize) -> Self
+ where T: Sized,
+ {
+ self.wrapping_offset((count as isize).wrapping_neg())
+ }
+
+ /// 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`]: ./ptr/fn.read.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn read(self) -> T
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.read_volatile.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn read_volatile(self) -> T
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.read_unaligned.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn read_unaligned(self) -> T
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.copy.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn copy_to(self, dest: *mut T, count: usize)
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.copy_nonoverlapping.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn copy_to_nonoverlapping(self, dest: *mut T, count: usize)
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.copy.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn copy_from(self, src: *const T, count: usize)
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.copy_nonoverlapping.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn copy_from_nonoverlapping(self, src: *const T, count: usize)
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.drop_in_place.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn drop_in_place(self) {
+ 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`]: ./ptr/fn.write.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn write(self, val: T)
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.write_bytes.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn write_bytes(self, val: u8, count: usize)
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.write_volatile.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn write_volatile(self, val: T)
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.write_unaligned.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn write_unaligned(self, val: T)
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.replace.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn replace(self, src: T) -> T
+ where T: Sized,
+ {
+ 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`]: ./ptr/fn.swap.html
+ #[stable(feature = "pointer_methods", since = "1.26.0")]
+ #[inline]
+ pub unsafe fn swap(self, with: *mut T)
+ where T: Sized,
+ {
+ 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_value()`.
+ ///
+ /// The offset is expressed in number of `T` elements, and not bytes. The value returned can be
+ /// used with the `offset` or `offset_to` methods.
+ ///
+ /// There are no guarantees whatsover 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[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");
+ }
+ unsafe {
+ align_offset(self, align)
+ }
+ }
+}
+
+/// Align pointer `p`.
+///
+/// Calculate offset (in terms of elements of `stride` stride) that has to be applied
+/// to pointer `p` so that pointer `p` would get aligned to `a`.
+///
+/// Note: This implementation has been carefully tailored to not panic. It is UB for this to panic.
+/// The only real change that can be made here is change of `INV_TABLE_MOD_16` and associated
+/// constants.
+///
+/// If we ever decide to make it possible to call the intrinsic with `a` that is not a
+/// power-of-two, it will probably be more prudent to just change to a naive implementation rather
+/// than trying to adapt this to accommodate that change.
+///
+/// Any questions go to @nagisa.
+#[lang="align_offset"]
+pub(crate) unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
+ /// Calculate multiplicative modular inverse of `x` modulo `m`.
+ ///
+ /// This implementation is tailored for align_offset and has following preconditions:
+ ///
+ /// * `m` is a power-of-two;
+ /// * `x < m`; (if `x ≥ m`, pass in `x % m` instead)
+ ///
+ /// Implementation of this function shall not panic. Ever.
+ #[inline]
+ fn mod_inv(x: usize, m: usize) -> usize {
+ /// Multiplicative modular inverse table modulo 2⁴ = 16.
+ ///
+ /// Note, that this table does not contain values where inverse does not exist (i.e., for
+ /// `0⁻¹ mod 16`, `2⁻¹ mod 16`, etc.)
+ const INV_TABLE_MOD_16: [u8; 8] = [1, 11, 13, 7, 9, 3, 5, 15];
+ /// Modulo for which the `INV_TABLE_MOD_16` is intended.
+ const INV_TABLE_MOD: usize = 16;
+ /// INV_TABLE_MOD²
+ const INV_TABLE_MOD_SQUARED: usize = INV_TABLE_MOD * INV_TABLE_MOD;
+
+ let table_inverse = INV_TABLE_MOD_16[(x & (INV_TABLE_MOD - 1)) >> 1] as usize;
+ if m <= INV_TABLE_MOD {
+ table_inverse & (m - 1)
+ } else {
+ // We iterate "up" using the following formula:
+ //
+ // $$ xy ≡ 1 (mod 2ⁿ) → xy (2 - xy) ≡ 1 (mod 2²ⁿ) $$
+ //
+ // until 2²ⁿ ≥ m. Then we can reduce to our desired `m` by taking the result `mod m`.
+ let mut inverse = table_inverse;
+ let mut going_mod = INV_TABLE_MOD_SQUARED;
+ loop {
+ // y = y * (2 - xy) mod n
+ //
+ // Note, that we use wrapping operations here intentionally – the original formula
+ // uses e.g., subtraction `mod n`. It is entirely fine to do them `mod
+ // usize::max_value()` instead, because we take the result `mod n` at the end
+ // anyway.
+ inverse = inverse.wrapping_mul(
+ 2usize.wrapping_sub(x.wrapping_mul(inverse))
+ ) & (going_mod - 1);
+ if going_mod > m {
+ return inverse & (m - 1);
+ }
+ going_mod = going_mod.wrapping_mul(going_mod);
+ }
+ }
+ }
+
+ let stride = mem::size_of::<T>();
+ let a_minus_one = a.wrapping_sub(1);
+ let pmoda = p as usize & a_minus_one;
+
+ if pmoda == 0 {
+ // Already aligned. Yay!
+ return 0;
+ }
+
+ if stride <= 1 {
+ return if stride == 0 {
+ // If the pointer is not aligned, and the element is zero-sized, then no amount of
+ // elements will ever align the pointer.
+ !0
+ } else {
+ a.wrapping_sub(pmoda)
+ };
+ }
+
+ let smoda = stride & a_minus_one;
+ // a is power-of-two so cannot be 0. stride = 0 is handled above.
+ let gcdpow = intrinsics::cttz_nonzero(stride).min(intrinsics::cttz_nonzero(a));
+ let gcd = 1usize << gcdpow;
+
+ if p as usize & (gcd - 1) == 0 {
+ // This branch solves for the following linear congruence equation:
+ //
+ // $$ p + so ≡ 0 mod a $$
+ //
+ // $p$ here is the pointer value, $s$ – stride of `T`, $o$ offset in `T`s, and $a$ – the
+ // requested alignment.
+ //
+ // g = gcd(a, s)
+ // o = (a - (p mod a))/g * ((s/g)⁻¹ mod a)
+ //
+ // The first term is “the relative alignment of p to a”, the second term is “how does
+ // incrementing p by s bytes change the relative alignment of p”. Division by `g` is
+ // necessary to make this equation well formed if $a$ and $s$ are not co-prime.
+ //
+ // Furthermore, the result produced by this solution is not “minimal”, so it is necessary
+ // to take the result $o mod lcm(s, a)$. We can replace $lcm(s, a)$ with just a $a / g$.
+ let j = a.wrapping_sub(pmoda) >> gcdpow;
+ let k = smoda >> gcdpow;
+ return intrinsics::unchecked_rem(j.wrapping_mul(mod_inv(k, a)), a >> gcdpow);
+ }
+
+ // Cannot be aligned at all.
+ usize::max_value()
+}
+
+
+
+// Equality for pointers
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> PartialEq for *const T {
+ #[inline]
+ fn eq(&self, other: &*const T) -> bool { *self == *other }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Eq for *const T {}
+
+#[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 {}
+
+/// Compares raw pointers for equality.
+///
+/// This is the same as using the `==` operator, but less generic:
+/// the arguments have to be `*const T` raw pointers,
+/// not anything that implements `PartialEq`.
+///
+/// This can be used to compare `&T` references (which coerce to `*const T` implicitly)
+/// by their address rather than comparing the values they point to
+/// (which is what the `PartialEq for &T` implementation does).
+///
+/// # Examples
+///
+/// ```
+/// use std::ptr;
+///
+/// let five = 5;
+/// let other_five = 5;
+/// let five_ref = &five;
+/// let same_five_ref = &five;
+/// let other_five_ref = &other_five;
+///
+/// assert!(five_ref == same_five_ref);
+/// assert!(ptr::eq(five_ref, same_five_ref));
+///
+/// assert!(five_ref == other_five_ref);
+/// assert!(!ptr::eq(five_ref, other_five_ref));
+/// ```
+///
+/// Slices are also compared by their length (fat pointers):
+///
+/// ```
+/// let a = [1, 2, 3];
+/// assert!(std::ptr::eq(&a[..3], &a[..3]));
+/// assert!(!std::ptr::eq(&a[..2], &a[..3]));
+/// assert!(!std::ptr::eq(&a[0..2], &a[1..3]));
+/// ```
+///
+/// Traits are also compared by their implementation:
+///
+/// ```
+/// #[repr(transparent)]
+/// struct Wrapper { member: i32 }
+///
+/// trait Trait {}
+/// impl Trait for Wrapper {}
+/// impl Trait for i32 {}
+///
+/// fn main() {
+/// let wrapper = Wrapper { member: 10 };
+///
+/// // Pointers have equal addresses.
+/// assert!(std::ptr::eq(
+/// &wrapper as *const Wrapper as *const u8,
+/// &wrapper.member as *const i32 as *const u8
+/// ));
+///
+/// // Objects have equal addresses, but `Trait` has different implementations.
+/// assert!(!std::ptr::eq(
+/// &wrapper as &dyn Trait,
+/// &wrapper.member as &dyn Trait,
+/// ));
+/// assert!(!std::ptr::eq(
+/// &wrapper as &dyn Trait as *const dyn Trait,
+/// &wrapper.member as &dyn Trait as *const dyn Trait,
+/// ));
+///
+/// // Converting the reference to a `*const u8` compares by address.
+/// assert!(std::ptr::eq(
+/// &wrapper as &dyn Trait as *const dyn Trait as *const u8,
+/// &wrapper.member as &dyn Trait as *const dyn Trait as *const u8,
+/// ));
+/// }
+/// ```
+#[stable(feature = "ptr_eq", since = "1.17.0")]
+#[inline]
+pub fn eq<T: ?Sized>(a: *const T, b: *const T) -> bool {
+ a == b
+}
+
+/// Hash a raw pointer.
+///
+/// This can be used to hash a `&T` reference (which coerces to `*const T` implicitly)
+/// by its address rather than the value it points to
+/// (which is what the `Hash for &T` implementation does).
+///
+/// # Examples
+///
+/// ```
+/// use std::collections::hash_map::DefaultHasher;
+/// use std::hash::{Hash, Hasher};
+/// use std::ptr;
+///
+/// let five = 5;
+/// let five_ref = &five;
+///
+/// let mut hasher = DefaultHasher::new();
+/// ptr::hash(five_ref, &mut hasher);
+/// let actual = hasher.finish();
+///
+/// let mut hasher = DefaultHasher::new();
+/// (five_ref as *const i32).hash(&mut hasher);
+/// let expected = hasher.finish();
+///
+/// assert_eq!(actual, expected);
+/// ```
+#[stable(feature = "ptr_hash", since = "1.35.0")]
+pub fn hash<T: ?Sized, S: hash::Hasher>(hashee: *const T, into: &mut S) {
+ use crate::hash::Hash;
+ hashee.hash(into);
+}
+
+// Impls for function pointers
+macro_rules! fnptr_impls_safety_abi {
+ ($FnTy: ty, $($Arg: ident),*) => {
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> PartialEq for $FnTy {
+ #[inline]
+ fn eq(&self, other: &Self) -> bool {
+ *self as usize == *other as usize
+ }
+ }
+
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> Eq for $FnTy {}
+
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> PartialOrd for $FnTy {
+ #[inline]
+ fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+ (*self as usize).partial_cmp(&(*other as usize))
+ }
+ }
+
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> Ord for $FnTy {
+ #[inline]
+ fn cmp(&self, other: &Self) -> Ordering {
+ (*self as usize).cmp(&(*other as usize))
+ }
+ }
+
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> hash::Hash for $FnTy {
+ fn hash<HH: hash::Hasher>(&self, state: &mut HH) {
+ state.write_usize(*self as usize)
+ }
+ }
+
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> fmt::Pointer for $FnTy {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Pointer::fmt(&(*self as *const ()), f)
+ }
+ }
+
+ #[stable(feature = "fnptr_impls", since = "1.4.0")]
+ impl<Ret, $($Arg),*> fmt::Debug for $FnTy {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Pointer::fmt(&(*self as *const ()), f)
+ }
+ }
+ }
+}
+
+macro_rules! fnptr_impls_args {
+ ($($Arg: ident),+) => {
+ fnptr_impls_safety_abi! { extern "Rust" fn($($Arg),*) -> Ret, $($Arg),* }
+ fnptr_impls_safety_abi! { extern "C" fn($($Arg),*) -> Ret, $($Arg),* }
+ fnptr_impls_safety_abi! { extern "C" fn($($Arg),* , ...) -> Ret, $($Arg),* }
+ fnptr_impls_safety_abi! { unsafe extern "Rust" fn($($Arg),*) -> Ret, $($Arg),* }
+ fnptr_impls_safety_abi! { unsafe extern "C" fn($($Arg),*) -> Ret, $($Arg),* }
+ fnptr_impls_safety_abi! { unsafe extern "C" fn($($Arg),* , ...) -> Ret, $($Arg),* }
+ };
+ () => {
+ // No variadic functions with 0 parameters
+ fnptr_impls_safety_abi! { extern "Rust" fn() -> Ret, }
+ fnptr_impls_safety_abi! { extern "C" fn() -> Ret, }
+ fnptr_impls_safety_abi! { unsafe extern "Rust" fn() -> Ret, }
+ fnptr_impls_safety_abi! { unsafe extern "C" fn() -> Ret, }
+ };
+}
+
+fnptr_impls_args! { }
+fnptr_impls_args! { A }
+fnptr_impls_args! { A, B }
+fnptr_impls_args! { A, B, C }
+fnptr_impls_args! { A, B, C, D }
+fnptr_impls_args! { A, B, C, D, E }
+fnptr_impls_args! { A, B, C, D, E, F }
+fnptr_impls_args! { A, B, C, D, E, F, G }
+fnptr_impls_args! { A, B, C, D, E, F, G, H }
+fnptr_impls_args! { A, B, C, D, E, F, G, H, I }
+fnptr_impls_args! { A, B, C, D, E, F, G, H, I, J }
+fnptr_impls_args! { A, B, C, D, E, F, G, H, I, J, K }
+fnptr_impls_args! { A, B, C, D, E, F, G, H, I, J, K, L }
+
+// Comparison for pointers
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Ord for *const T {
+ #[inline]
+ fn cmp(&self, other: &*const T) -> Ordering {
+ if self < other {
+ Less
+ } else if self == other {
+ Equal
+ } else {
+ Greater
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> PartialOrd for *const T {
+ #[inline]
+ fn partial_cmp(&self, other: &*const T) -> Option<Ordering> {
+ Some(self.cmp(other))
+ }
+
+ #[inline]
+ fn lt(&self, other: &*const T) -> bool { *self < *other }
+
+ #[inline]
+ fn le(&self, other: &*const T) -> bool { *self <= *other }
+
+ #[inline]
+ fn gt(&self, other: &*const T) -> bool { *self > *other }
+
+ #[inline]
+ fn ge(&self, other: &*const T) -> bool { *self >= *other }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Ord for *mut T {
+ #[inline]
+ fn cmp(&self, other: &*mut T) -> Ordering {
+ if self < other {
+ Less
+ } else if self == other {
+ Equal
+ } else {
+ Greater
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> PartialOrd for *mut T {
+ #[inline]
+ fn partial_cmp(&self, other: &*mut T) -> Option<Ordering> {
+ Some(self.cmp(other))
+ }
+
+ #[inline]
+ fn lt(&self, other: &*mut T) -> bool { *self < *other }
+
+ #[inline]
+ fn le(&self, other: &*mut T) -> bool { *self <= *other }
+
+ #[inline]
+ fn gt(&self, other: &*mut T) -> bool { *self > *other }
+
+ #[inline]
+ fn ge(&self, other: &*mut T) -> bool { *self >= *other }
+}
--- /dev/null
+use crate::convert::From;
+use crate::ops::{CoerceUnsized, DispatchFromDyn};
+use crate::fmt;
+use crate::hash;
+use crate::marker::Unsize;
+use crate::mem;
+use crate::ptr::Unique;
+use crate::cmp::Ordering;
+
+/// `*mut T` but non-zero and covariant.
+///
+/// This is often the correct thing to use when building data structures using
+/// raw pointers, but is ultimately more dangerous to use because of its additional
+/// properties. If you're not sure if you should use `NonNull<T>`, just use `*mut T`!
+///
+/// Unlike `*mut T`, the pointer must always be non-null, even if the pointer
+/// is never dereferenced. This is so that enums may use this forbidden value
+/// as a discriminant -- `Option<NonNull<T>>` has the same size as `*mut T`.
+/// However the pointer may still dangle if it isn't dereferenced.
+///
+/// Unlike `*mut T`, `NonNull<T>` is covariant over `T`. If this is incorrect
+/// for your use case, you should include some [`PhantomData`] in your type to
+/// provide invariance, such as `PhantomData<Cell<T>>` or `PhantomData<&'a mut T>`.
+/// Usually this won't be necessary; covariance is correct for most safe abstractions,
+/// such as `Box`, `Rc`, `Arc`, `Vec`, and `LinkedList`. This is the case because they
+/// provide a public API that follows the normal shared XOR mutable rules of Rust.
+///
+/// Notice that `NonNull<T>` has a `From` instance for `&T`. However, this does
+/// not change the fact that mutating through a (pointer derived from a) shared
+/// reference is undefined behavior unless the mutation happens inside an
+/// [`UnsafeCell<T>`]. The same goes for creating a mutable reference from a shared
+/// reference. When using this `From` instance without an `UnsafeCell<T>`,
+/// it is your responsibility to ensure that `as_mut` is never called, and `as_ptr`
+/// is never used for mutation.
+///
+/// [`PhantomData`]: ../marker/struct.PhantomData.html
+/// [`UnsafeCell<T>`]: ../cell/struct.UnsafeCell.html
+#[stable(feature = "nonnull", since = "1.25.0")]
+#[repr(transparent)]
+#[rustc_layout_scalar_valid_range_start(1)]
+#[cfg_attr(not(stage0), rustc_nonnull_optimization_guaranteed)]
+pub struct NonNull<T: ?Sized> {
+ pointer: *const T,
+}
+
+/// `NonNull` pointers are not `Send` because the data they reference may be aliased.
+// N.B., this impl is unnecessary, but should provide better error messages.
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> !Send for NonNull<T> { }
+
+/// `NonNull` pointers are not `Sync` because the data they reference may be aliased.
+// N.B., this impl is unnecessary, but should provide better error messages.
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> !Sync for NonNull<T> { }
+
+impl<T: Sized> NonNull<T> {
+ /// Creates a new `NonNull` that is dangling, but well-aligned.
+ ///
+ /// This is useful for initializing types which lazily allocate, like
+ /// `Vec::new` does.
+ ///
+ /// Note that the pointer value may potentially represent a valid pointer to
+ /// a `T`, which means this must not be used as a "not yet initialized"
+ /// sentinel value. Types that lazily allocate must track initialization by
+ /// some other means.
+ #[stable(feature = "nonnull", since = "1.25.0")]
+ #[inline]
+ pub const fn dangling() -> Self {
+ unsafe {
+ let ptr = mem::align_of::<T>() as *mut T;
+ NonNull::new_unchecked(ptr)
+ }
+ }
+}
+
+impl<T: ?Sized> NonNull<T> {
+ /// Creates a new `NonNull`.
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must be non-null.
+ #[stable(feature = "nonnull", since = "1.25.0")]
+ #[inline]
+ pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
+ NonNull { pointer: ptr as _ }
+ }
+
+ /// Creates a new `NonNull` if `ptr` is non-null.
+ #[stable(feature = "nonnull", since = "1.25.0")]
+ #[inline]
+ pub fn new(ptr: *mut T) -> Option<Self> {
+ if !ptr.is_null() {
+ Some(unsafe { Self::new_unchecked(ptr) })
+ } else {
+ None
+ }
+ }
+
+ /// Acquires the underlying `*mut` pointer.
+ #[stable(feature = "nonnull", since = "1.25.0")]
+ #[inline]
+ pub const fn as_ptr(self) -> *mut T {
+ self.pointer as *mut T
+ }
+
+ /// Dereferences the content.
+ ///
+ /// The resulting lifetime is bound to self so this behaves "as if"
+ /// it were actually an instance of T that is getting borrowed. If a longer
+ /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`.
+ #[stable(feature = "nonnull", since = "1.25.0")]
+ #[inline]
+ pub unsafe fn as_ref(&self) -> &T {
+ &*self.as_ptr()
+ }
+
+ /// Mutably dereferences the content.
+ ///
+ /// The resulting lifetime is bound to self so this behaves "as if"
+ /// it were actually an instance of T that is getting borrowed. If a longer
+ /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`.
+ #[stable(feature = "nonnull", since = "1.25.0")]
+ #[inline]
+ pub unsafe fn as_mut(&mut self) -> &mut T {
+ &mut *self.as_ptr()
+ }
+
+ /// Cast to a pointer of another type
+ #[stable(feature = "nonnull_cast", since = "1.27.0")]
+ #[inline]
+ pub const fn cast<U>(self) -> NonNull<U> {
+ unsafe {
+ NonNull::new_unchecked(self.as_ptr() as *mut U)
+ }
+ }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> Clone for NonNull<T> {
+ #[inline]
+ fn clone(&self) -> Self {
+ *self
+ }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> Copy for NonNull<T> { }
+
+#[unstable(feature = "coerce_unsized", issue = "27732")]
+impl<T: ?Sized, U: ?Sized> CoerceUnsized<NonNull<U>> for NonNull<T> where T: Unsize<U> { }
+
+#[unstable(feature = "dispatch_from_dyn", issue = "0")]
+impl<T: ?Sized, U: ?Sized> DispatchFromDyn<NonNull<U>> for NonNull<T> where T: Unsize<U> { }
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> fmt::Debug for NonNull<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Pointer::fmt(&self.as_ptr(), f)
+ }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> fmt::Pointer for NonNull<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Pointer::fmt(&self.as_ptr(), f)
+ }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> Eq for NonNull<T> {}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> PartialEq for NonNull<T> {
+ #[inline]
+ fn eq(&self, other: &Self) -> bool {
+ self.as_ptr() == other.as_ptr()
+ }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> Ord for NonNull<T> {
+ #[inline]
+ fn cmp(&self, other: &Self) -> Ordering {
+ self.as_ptr().cmp(&other.as_ptr())
+ }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> PartialOrd for NonNull<T> {
+ #[inline]
+ fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+ self.as_ptr().partial_cmp(&other.as_ptr())
+ }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> hash::Hash for NonNull<T> {
+ #[inline]
+ fn hash<H: hash::Hasher>(&self, state: &mut H) {
+ self.as_ptr().hash(state)
+ }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> From<Unique<T>> for NonNull<T> {
+ #[inline]
+ fn from(unique: Unique<T>) -> Self {
+ unsafe { NonNull::new_unchecked(unique.as_ptr()) }
+ }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> From<&mut T> for NonNull<T> {
+ #[inline]
+ fn from(reference: &mut T) -> Self {
+ unsafe { NonNull { pointer: reference as *mut T } }
+ }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> From<&T> for NonNull<T> {
+ #[inline]
+ fn from(reference: &T) -> Self {
+ unsafe { NonNull { pointer: reference as *const T } }
+ }
+}
--- /dev/null
+use crate::convert::From;
+use crate::ops::{CoerceUnsized, DispatchFromDyn};
+use crate::fmt;
+use crate::marker::{PhantomData, Unsize};
+use crate::mem;
+use crate::ptr::NonNull;
+
+/// A wrapper around a raw non-null `*mut T` that indicates that the possessor
+/// of this wrapper owns the referent. Useful for building abstractions like
+/// `Box<T>`, `Vec<T>`, `String`, and `HashMap<K, V>`.
+///
+/// Unlike `*mut T`, `Unique<T>` behaves "as if" it were an instance of `T`.
+/// It implements `Send`/`Sync` if `T` is `Send`/`Sync`. It also implies
+/// the kind of strong aliasing guarantees an instance of `T` can expect:
+/// the referent of the pointer should not be modified without a unique path to
+/// its owning Unique.
+///
+/// If you're uncertain of whether it's correct to use `Unique` for your purposes,
+/// consider using `NonNull`, which has weaker semantics.
+///
+/// Unlike `*mut T`, the pointer must always be non-null, even if the pointer
+/// is never dereferenced. This is so that enums may use this forbidden value
+/// as a discriminant -- `Option<Unique<T>>` has the same size as `Unique<T>`.
+/// However the pointer may still dangle if it isn't dereferenced.
+///
+/// Unlike `*mut T`, `Unique<T>` is covariant over `T`. This should always be correct
+/// for any type which upholds Unique's aliasing requirements.
+#[unstable(feature = "ptr_internals", issue = "0",
+ reason = "use NonNull instead and consider PhantomData<T> \
+ (if you also use #[may_dangle]), Send, and/or Sync")]
+#[doc(hidden)]
+#[repr(transparent)]
+#[rustc_layout_scalar_valid_range_start(1)]
+pub struct Unique<T: ?Sized> {
+ pointer: *const T,
+ // NOTE: this marker has no consequences for variance, but is necessary
+ // for dropck to understand that we logically own a `T`.
+ //
+ // For details, see:
+ // https://github.com/rust-lang/rfcs/blob/master/text/0769-sound-generic-drop.md#phantom-data
+ _marker: PhantomData<T>,
+}
+
+/// `Unique` pointers are `Send` if `T` is `Send` because the data they
+/// reference is unaliased. Note that this aliasing invariant is
+/// unenforced by the type system; the abstraction using the
+/// `Unique` must enforce it.
+#[unstable(feature = "ptr_internals", issue = "0")]
+unsafe impl<T: Send + ?Sized> Send for Unique<T> { }
+
+/// `Unique` pointers are `Sync` if `T` is `Sync` because the data they
+/// reference is unaliased. Note that this aliasing invariant is
+/// unenforced by the type system; the abstraction using the
+/// `Unique` must enforce it.
+#[unstable(feature = "ptr_internals", issue = "0")]
+unsafe impl<T: Sync + ?Sized> Sync for Unique<T> { }
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: Sized> Unique<T> {
+ /// Creates a new `Unique` that is dangling, but well-aligned.
+ ///
+ /// This is useful for initializing types which lazily allocate, like
+ /// `Vec::new` does.
+ ///
+ /// Note that the pointer value may potentially represent a valid pointer to
+ /// a `T`, which means this must not be used as a "not yet initialized"
+ /// sentinel value. Types that lazily allocate must track initialization by
+ /// some other means.
+ // FIXME: rename to dangling() to match NonNull?
+ #[inline]
+ pub const fn empty() -> Self {
+ unsafe {
+ Unique::new_unchecked(mem::align_of::<T>() as *mut T)
+ }
+ }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> Unique<T> {
+ /// Creates a new `Unique`.
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must be non-null.
+ #[inline]
+ pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
+ Unique { pointer: ptr as _, _marker: PhantomData }
+ }
+
+ /// Creates a new `Unique` if `ptr` is non-null.
+ #[inline]
+ pub fn new(ptr: *mut T) -> Option<Self> {
+ if !ptr.is_null() {
+ Some(unsafe { Unique { pointer: ptr as _, _marker: PhantomData } })
+ } else {
+ None
+ }
+ }
+
+ /// Acquires the underlying `*mut` pointer.
+ #[inline]
+ pub const fn as_ptr(self) -> *mut T {
+ self.pointer as *mut T
+ }
+
+ /// Dereferences the content.
+ ///
+ /// The resulting lifetime is bound to self so this behaves "as if"
+ /// it were actually an instance of T that is getting borrowed. If a longer
+ /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`.
+ #[inline]
+ pub unsafe fn as_ref(&self) -> &T {
+ &*self.as_ptr()
+ }
+
+ /// Mutably dereferences the content.
+ ///
+ /// The resulting lifetime is bound to self so this behaves "as if"
+ /// it were actually an instance of T that is getting borrowed. If a longer
+ /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`.
+ #[inline]
+ pub unsafe fn as_mut(&mut self) -> &mut T {
+ &mut *self.as_ptr()
+ }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> Clone for Unique<T> {
+ #[inline]
+ fn clone(&self) -> Self {
+ *self
+ }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> Copy for Unique<T> { }
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized, U: ?Sized> CoerceUnsized<Unique<U>> for Unique<T> where T: Unsize<U> { }
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized, U: ?Sized> DispatchFromDyn<Unique<U>> for Unique<T> where T: Unsize<U> { }
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> fmt::Debug for Unique<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Pointer::fmt(&self.as_ptr(), f)
+ }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> fmt::Pointer for Unique<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Pointer::fmt(&self.as_ptr(), f)
+ }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> From<&mut T> for Unique<T> {
+ #[inline]
+ fn from(reference: &mut T) -> Self {
+ unsafe { Unique { pointer: reference as *mut T, _marker: PhantomData } }
+ }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> From<&T> for Unique<T> {
+ #[inline]
+ fn from(reference: &T) -> Self {
+ unsafe { Unique { pointer: reference as *const T, _marker: PhantomData } }
+ }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<'a, T: ?Sized> From<NonNull<T>> for Unique<T> {
+ #[inline]
+ fn from(p: NonNull<T>) -> Self {
+ unsafe { Unique::new_unchecked(p.as_ptr()) }
+ }
+}
projects / rust.git / commitdiff