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| -rw-r--r-- | library/core/src/sync/atomic.rs | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/library/core/src/sync/atomic.rs b/library/core/src/sync/atomic.rs index a3d93d7074b..0c53b6ed54a 100644 --- a/library/core/src/sync/atomic.rs +++ b/library/core/src/sync/atomic.rs @@ -801,6 +801,64 @@ impl AtomicBool { pub fn as_mut_ptr(&self) -> *mut bool { self.v.get() as *mut bool } + + /// Fetches the value, and applies a function to it that returns an optional + /// new value. Returns a `Result` of `Ok(previous_value)` if the function + /// returned `Some(_)`, else `Err(previous_value)`. + /// + /// Note: This may call the function multiple times if the value has been + /// changed from other threads in the meantime, as long as the function + /// returns `Some(_)`, but the function will have been applied only once to + /// the stored value. + /// + /// `fetch_update` takes two [`Ordering`] arguments to describe the memory + /// ordering of this operation. The first describes the required ordering for + /// when the operation finally succeeds while the second describes the + /// required ordering for loads. These correspond to the success and failure + /// orderings of [`AtomicBool::compare_exchange`] respectively. + /// + /// Using [`Acquire`] as success ordering makes the store part of this + /// operation [`Relaxed`], and using [`Release`] makes the final successful + /// load [`Relaxed`]. The (failed) load ordering can only be [`SeqCst`], + /// [`Acquire`] or [`Relaxed`] and must be equivalent to or weaker than the + /// success ordering. + /// + /// **Note:** This method is only available on platforms that support atomic + /// operations on `u8`. + /// + /// # Examples + /// + /// ```rust + /// #![feature(atomic_fetch_update)] + /// use std::sync::atomic::{AtomicBool, Ordering}; + /// + /// let x = AtomicBool::new(false); + /// assert_eq!(x.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |_| None), Err(false)); + /// assert_eq!(x.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |x| Some(!x)), Ok(false)); + /// assert_eq!(x.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |x| Some(!x)), Ok(true)); + /// assert_eq!(x.load(Ordering::SeqCst), false); + /// ``` + #[inline] + #[unstable(feature = "atomic_fetch_update", reason = "recently added", issue = "78639")] + #[cfg(target_has_atomic = "8")] + pub fn fetch_update<F>( + &self, + set_order: Ordering, + fetch_order: Ordering, + mut f: F, + ) -> Result<bool, bool> + where + F: FnMut(bool) -> Option<bool>, + { + let mut prev = self.load(fetch_order); + while let Some(next) = f(prev) { + match self.compare_exchange_weak(prev, next, set_order, fetch_order) { + x @ Ok(_) => return x, + Err(next_prev) => prev = next_prev, + } + } + Err(prev) + } } #[cfg(target_has_atomic_load_store = "ptr")] @@ -1123,6 +1181,73 @@ impl<T> AtomicPtr<T> { } } } + + /// Fetches the value, and applies a function to it that returns an optional + /// new value. Returns a `Result` of `Ok(previous_value)` if the function + /// returned `Some(_)`, else `Err(previous_value)`. + /// + /// Note: This may call the function multiple times if the value has been + /// changed from other threads in the meantime, as long as the function + /// returns `Some(_)`, but the function will have been applied only once to + /// the stored value. + /// + /// `fetch_update` takes two [`Ordering`] arguments to describe the memory + /// ordering of this operation. The first describes the required ordering for + /// when the operation finally succeeds while the second describes the + /// required ordering for loads. These correspond to the success and failure + /// orderings of [`AtomicPtr::compare_exchange`] respectively. + /// + /// Using [`Acquire`] as success ordering makes the store part of this + /// operation [`Relaxed`], and using [`Release`] makes the final successful + /// load [`Relaxed`]. The (failed) load ordering can only be [`SeqCst`], + /// [`Acquire`] or [`Relaxed`] and must be equivalent to or weaker than the + /// success ordering. + /// + /// **Note:** This method is only available on platforms that support atomic + /// operations on pointers. + /// + /// # Examples + /// + /// ```rust + /// #![feature(atomic_fetch_update)] + /// use std::sync::atomic::{AtomicPtr, Ordering}; + /// + /// let ptr: *mut _ = &mut 5; + /// let some_ptr = AtomicPtr::new(ptr); + /// + /// let new: *mut _ = &mut 10; + /// assert_eq!(some_ptr.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |_| None), Err(ptr)); + /// let result = some_ptr.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |x| { + /// if x == ptr { + /// Some(new) + /// } else { + /// None + /// } + /// }); + /// assert_eq!(result, Ok(ptr)); + /// assert_eq!(some_ptr.load(Ordering::SeqCst), new); + /// ``` + #[inline] + #[unstable(feature = "atomic_fetch_update", reason = "recently added", issue = "78639")] + #[cfg(target_has_atomic = "ptr")] + pub fn fetch_update<F>( + &self, + set_order: Ordering, + fetch_order: Ordering, + mut f: F, + ) -> Result<*mut T, *mut T> + where + F: FnMut(*mut T) -> Option<*mut T>, + { + let mut prev = self.load(fetch_order); + while let Some(next) = f(prev) { + match self.compare_exchange_weak(prev, next, set_order, fetch_order) { + x @ Ok(_) => return x, + Err(next_prev) => prev = next_prev, + } + } + Err(prev) + } } #[cfg(target_has_atomic_load_store = "8")] |