| //! 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]. |
| //! * For a pointer to be valid, it is necessary, but not always sufficient, that the pointer |
| //! be *dereferencable*: the memory range of the given size starting at the pointer must all be |
| //! within the bounds of a single allocated object. Note that in Rust, |
| //! every (stack-allocated) variable is considered a separate allocated object. |
| //! * 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 |
| |
| // ignore-tidy-undocumented-unsafe |
| |
| #![stable(feature = "rust1", since = "1.0.0")] |
| |
| use crate::cmp::Ordering; |
| use crate::fmt; |
| use crate::hash; |
| use crate::intrinsics; |
| use crate::mem::{self, MaybeUninit}; |
| |
| #[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 = "none")] |
| pub use unique::Unique; |
| |
| mod const_ptr; |
| mod mut_ptr; |
| |
| /// 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. |
| /// |
| /// Unaligned values cannot be dropped in place, they must be copied to an aligned |
| /// location first using [`ptr::read_unaligned`]. |
| /// |
| /// [`ptr::read`]: ../ptr/fn.read.html |
| /// [`ptr::read_unaligned`]: ../ptr/fn.read_unaligned.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. |
| /// |
| /// 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()); |
| /// ``` |
| /// |
| /// 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")] |
| #[lang = "drop_in_place"] |
| #[allow(unconditional_recursion)] |
| pub unsafe fn 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. |
| 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(always)] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_promotable] |
| #[rustc_const_stable(feature = "const_ptr_null", since = "1.32.0")] |
| 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(always)] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_promotable] |
| #[rustc_const_stable(feature = "const_ptr_null", since = "1.32.0")] |
| pub const fn null_mut<T>() -> *mut T { |
| 0 as *mut T |
| } |
| |
| #[repr(C)] |
| pub(crate) union Repr<T> { |
| pub(crate) rust: *const [T], |
| rust_mut: *mut [T], |
| pub(crate) raw: FatPtr<T>, |
| } |
| |
| #[repr(C)] |
| pub(crate) struct FatPtr<T> { |
| data: *const T, |
| pub(crate) len: usize, |
| } |
| |
| /// Forms a raw slice from a pointer and a length. |
| /// |
| /// The `len` argument is the number of **elements**, not the number of bytes. |
| /// |
| /// This function is safe, but actually using the return value is unsafe. |
| /// See the documentation of [`from_raw_parts`] for slice safety requirements. |
| /// |
| /// [`from_raw_parts`]: ../../std/slice/fn.from_raw_parts.html |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// use std::ptr; |
| /// |
| /// // create a slice pointer when starting out with a pointer to the first element |
| /// let x = [5, 6, 7]; |
| /// let ptr = x.as_ptr(); |
| /// let slice = ptr::slice_from_raw_parts(ptr, 3); |
| /// assert_eq!(unsafe { &*slice }[2], 7); |
| /// ``` |
| #[inline] |
| #[stable(feature = "slice_from_raw_parts", since = "1.42.0")] |
| #[rustc_const_unstable(feature = "const_slice_from_raw_parts", issue = "67456")] |
| pub const fn slice_from_raw_parts<T>(data: *const T, len: usize) -> *const [T] { |
| unsafe { Repr { raw: FatPtr { data, len } }.rust } |
| } |
| |
| /// Performs the same functionality as [`slice_from_raw_parts`], except that a |
| /// raw mutable slice is returned, as opposed to a raw immutable slice. |
| /// |
| /// See the documentation of [`slice_from_raw_parts`] for more details. |
| /// |
| /// This function is safe, but actually using the return value is unsafe. |
| /// See the documentation of [`from_raw_parts_mut`] for slice safety requirements. |
| /// |
| /// [`slice_from_raw_parts`]: fn.slice_from_raw_parts.html |
| /// [`from_raw_parts_mut`]: ../../std/slice/fn.from_raw_parts_mut.html |
| #[inline] |
| #[stable(feature = "slice_from_raw_parts", since = "1.42.0")] |
| #[rustc_const_unstable(feature = "const_slice_from_raw_parts", issue = "67456")] |
| pub const fn slice_from_raw_parts_mut<T>(data: *mut T, len: usize) -> *mut [T] { |
| unsafe { Repr { raw: FatPtr { data, len } }.rust_mut } |
| } |
| |
| /// 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 |
| /// |
| /// ## On `packed` structs |
| /// |
| /// It is currently impossible to create raw pointers to unaligned fields |
| /// of a packed struct. |
| /// |
| /// Attempting to create a raw pointer to an `unaligned` struct field with |
| /// an expression such as `&packed.unaligned as *const FieldType` creates an |
| /// intermediate unaligned reference before converting that to a raw pointer. |
| /// That this reference is temporary and immediately cast is inconsequential |
| /// as the compiler always expects references to be properly aligned. |
| /// As a result, using `&packed.unaligned as *const FieldType` causes immediate |
| /// *undefined behavior* in your program. |
| /// |
| /// An example of what not to do and how this relates to `read_unaligned` is: |
| /// |
| /// ```no_run |
| /// #[repr(packed, C)] |
| /// struct Packed { |
| /// _padding: u8, |
| /// unaligned: u32, |
| /// } |
| /// |
| /// let packed = Packed { |
| /// _padding: 0x00, |
| /// unaligned: 0x01020304, |
| /// }; |
| /// |
| /// let v = unsafe { |
| /// // Here we attempt to take the address of a 32-bit integer which is not aligned. |
| /// let unaligned = |
| /// // A temporary unaligned reference is created here which results in |
| /// // undefined behavior regardless of whether the reference is used or not. |
| /// &packed.unaligned |
| /// // Casting to a raw pointer doesn't help; the mistake already happened. |
| /// as *const u32; |
| /// |
| /// let v = std::ptr::read_unaligned(unaligned); |
| /// |
| /// v |
| /// }; |
| /// ``` |
| /// |
| /// Accessing unaligned fields directly with e.g. `packed.unaligned` is safe however. |
| // FIXME: Update docs based on outcome of RFC #2582 and friends. |
| /// |
| /// # Examples |
| /// |
| /// Read an usize value from a byte buffer: |
| /// |
| /// ``` |
| /// use std::mem; |
| /// |
| /// fn read_usize(x: &[u8]) -> usize { |
| /// assert!(x.len() >= mem::size_of::<usize>()); |
| /// |
| /// let ptr = x.as_ptr() as *const usize; |
| /// |
| /// unsafe { ptr.read_unaligned() } |
| /// } |
| /// ``` |
| #[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 |
| /// |
| /// ## On `packed` structs |
| /// |
| /// It is currently impossible to create raw pointers to unaligned fields |
| /// of a packed struct. |
| /// |
| /// Attempting to create a raw pointer to an `unaligned` struct field with |
| /// an expression such as `&packed.unaligned as *const FieldType` creates an |
| /// intermediate unaligned reference before converting that to a raw pointer. |
| /// That this reference is temporary and immediately cast is inconsequential |
| /// as the compiler always expects references to be properly aligned. |
| /// As a result, using `&packed.unaligned as *const FieldType` causes immediate |
| /// *undefined behavior* in your program. |
| /// |
| /// An example of what not to do and how this relates to `write_unaligned` is: |
| /// |
| /// ```no_run |
| /// #[repr(packed, C)] |
| /// struct Packed { |
| /// _padding: u8, |
| /// unaligned: u32, |
| /// } |
| /// |
| /// let v = 0x01020304; |
| /// let mut packed: Packed = unsafe { std::mem::zeroed() }; |
| /// |
| /// let v = unsafe { |
| /// // Here we attempt to take the address of a 32-bit integer which is not aligned. |
| /// let unaligned = |
| /// // A temporary unaligned reference is created here which results in |
| /// // undefined behavior regardless of whether the reference is used or not. |
| /// &mut packed.unaligned |
| /// // Casting to a raw pointer doesn't help; the mistake already happened. |
| /// as *mut u32; |
| /// |
| /// std::ptr::write_unaligned(unaligned, v); |
| /// |
| /// v |
| /// }; |
| /// ``` |
| /// |
| /// Accessing unaligned fields directly with e.g. `packed.unaligned` is safe however. |
| // FIXME: Update docs based on outcome of RFC #2582 and friends. |
| /// |
| /// # Examples |
| /// |
| /// Write an usize value to a byte buffer: |
| /// |
| /// ``` |
| /// use std::mem; |
| /// |
| /// fn write_usize(x: &mut [u8], val: usize) { |
| /// assert!(x.len() >= mem::size_of::<usize>()); |
| /// |
| /// let ptr = x.as_mut_ptr() as *mut usize; |
| /// |
| /// unsafe { ptr.write_unaligned(val) } |
| /// } |
| /// ``` |
| #[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); |
| } |
| |
| /// 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() |
| } |
| |
| /// 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 {} |
| /// |
| /// 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 } |