Add Atomic*::from_mut.
The atomic equivalent of Cell::from_mut.
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1 changed files with 97 additions and 1 deletions
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@ -110,6 +110,7 @@ use self::Ordering::*;
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use crate::cell::UnsafeCell;
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use crate::fmt;
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use crate::intrinsics;
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use crate::mem::align_of;
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use crate::hint::spin_loop;
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@ -327,6 +328,27 @@ impl AtomicBool {
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unsafe { &mut *(self.v.get() as *mut bool) }
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}
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/// Get atomic access to a `&mut bool`.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(atomic_from_mut)]
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/// use std::sync::atomic::{AtomicBool, Ordering};
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///
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/// let mut some_bool = true;
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/// let a = AtomicBool::from_mut(&mut some_bool);
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/// a.store(false, Ordering::Relaxed);
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/// assert_eq!(some_bool, false);
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/// ```
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#[inline]
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#[unstable(feature = "atomic_from_mut", issue = "76314")]
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pub fn from_mut(v: &mut bool) -> &Self {
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// SAFETY: the mutable reference guarantees unique ownership, and
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// alignment of both `bool` and `Self` is 1.
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unsafe { &*(v as *mut bool as *mut Self) }
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}
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/// Consumes the atomic and returns the contained value.
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///
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/// This is safe because passing `self` by value guarantees that no other threads are
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@ -820,6 +842,30 @@ impl<T> AtomicPtr<T> {
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unsafe { &mut *self.p.get() }
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}
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/// Get atomic access to a pointer.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(atomic_from_mut)]
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/// use std::sync::atomic::{AtomicPtr, Ordering};
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///
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/// let mut some_ptr = &mut 123 as *mut i32;
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/// let a = AtomicPtr::from_mut(&mut some_ptr);
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/// a.store(&mut 456, Ordering::Relaxed);
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/// assert_eq!(unsafe { *some_ptr }, 456);
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/// ```
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#[inline]
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#[unstable(feature = "atomic_from_mut", issue = "76314")]
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pub fn from_mut(v: &mut *mut T) -> &Self {
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let [] = [(); align_of::<Self>() - align_of::<*mut T>()];
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// SAFETY:
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// - the mutable reference guarantees unique ownership.
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// - the alignment of `*mut T` and `Self` is the same on all platforms
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// supported by rust, as verified above.
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unsafe { &*(v as *mut *mut T as *mut Self) }
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}
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/// Consumes the atomic and returns the contained value.
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///
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/// This is safe because passing `self` by value guarantees that no other threads are
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@ -1104,6 +1150,12 @@ impl<T> From<*mut T> for AtomicPtr<T> {
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}
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}
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macro_rules! if_not_8_bit {
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(u8, $($tt:tt)*) => { "" };
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(i8, $($tt:tt)*) => { "" };
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($_:ident, $($tt:tt)*) => { $($tt)* };
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}
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#[cfg(target_has_atomic_load_store = "8")]
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macro_rules! atomic_int {
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($cfg_cas:meta,
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@ -1115,7 +1167,8 @@ macro_rules! atomic_int {
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$stable_nand:meta,
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$const_stable:meta,
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$stable_init_const:meta,
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$s_int_type:expr, $int_ref:expr,
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$(from_mut: cfg($from_mut_cfg:meta),)?
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$s_int_type:literal, $int_ref:expr,
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$extra_feature:expr,
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$min_fn:ident, $max_fn:ident,
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$align:expr,
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@ -1226,6 +1279,45 @@ assert_eq!(some_var.load(Ordering::SeqCst), 5);
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}
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}
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doc_comment! {
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concat!("Get atomic access to a `&mut ", stringify!($int_type), "`.
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",
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if_not_8_bit! {
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$int_type,
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concat!(
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"**Note:** This function is only available on targets where `",
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stringify!($int_type), "` has an alignment of ", $align, " bytes."
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)
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},
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"
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# Examples
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```
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#![feature(atomic_from_mut)]
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", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
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let mut some_int = 123;
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let a = ", stringify!($atomic_type), "::from_mut(&mut some_int);
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a.store(100, Ordering::Relaxed);
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assert_eq!(some_int, 100);
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```
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"),
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#[inline]
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$(#[cfg($from_mut_cfg)])?
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#[unstable(feature = "atomic_from_mut", issue = "76314")]
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pub fn from_mut(v: &mut $int_type) -> &Self {
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let [] = [(); align_of::<Self>() - align_of::<$int_type>()];
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// SAFETY:
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// - the mutable reference guarantees unique ownership.
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// - the alignment of `$int_type` and `Self` is the
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// same on all platforms enabled by `$from_mut_cfg`
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// as verified above.
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unsafe { &*(v as *mut $int_type as *mut Self) }
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}
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}
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doc_comment! {
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concat!("Consumes the atomic and returns the contained value.
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@ -1984,6 +2076,7 @@ atomic_int! {
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
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unstable(feature = "integer_atomics", issue = "32976"),
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from_mut: cfg(not(target_arch = "x86")),
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"i64", "../../../std/primitive.i64.html",
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"",
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atomic_min, atomic_max,
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@ -2002,6 +2095,7 @@ atomic_int! {
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
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unstable(feature = "integer_atomics", issue = "32976"),
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from_mut: cfg(not(target_arch = "x86")),
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"u64", "../../../std/primitive.u64.html",
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"",
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atomic_umin, atomic_umax,
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@ -2020,6 +2114,7 @@ atomic_int! {
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unstable(feature = "integer_atomics", issue = "32976"),
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rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
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unstable(feature = "integer_atomics", issue = "32976"),
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from_mut: cfg(not(target_arch = "x86_64")),
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"i128", "../../../std/primitive.i128.html",
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"#![feature(integer_atomics)]\n\n",
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atomic_min, atomic_max,
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@ -2038,6 +2133,7 @@ atomic_int! {
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unstable(feature = "integer_atomics", issue = "32976"),
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rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
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unstable(feature = "integer_atomics", issue = "32976"),
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from_mut: cfg(not(target_arch = "x86_64")),
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"u128", "../../../std/primitive.u128.html",
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"#![feature(integer_atomics)]\n\n",
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atomic_umin, atomic_umax,
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