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//! Atomic `Option<Arc<T>>` that can only be filled once //! //! Since `FillOnceAtomicArc` can only be filled once it's safe to provide access to the inner `Option<Arc<T>>` and `Option<&T>` use crate::prelude::*; use std::fmt::{self, Debug, Formatter, Pointer}; use std::{sync::atomic::Ordering, sync::Arc}; /// Atomic abstraction of a `Option<Arc<T>>` that can provide access to a cloned `Option<Arc<T>>` and a `Option<&T>` pub struct FillOnceAtomicArc<T>(FillOnceAtomicOption<Arc<T>>); impl<T> FillOnceAtomicArc<T> { /// Creates new `FillOnceAtomicArc` /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicArc; /// # env_logger::init(); /// use std::sync::{Arc, atomic::Ordering}; /// let empty: FillOnceAtomicArc<()> = FillOnceAtomicArc::new(None); /// assert_eq!(empty.get_ref(Ordering::Relaxed), None); /// /// let filled = FillOnceAtomicArc::new(Arc::new(10)); /// assert_eq!(filled.get_ref(Ordering::Relaxed), Some(&10)); /// ``` #[inline] pub fn new<V>(data: V) -> Self where V: Into<Option<Arc<T>>>, { trace!("new()"); Self::from(data.into()) } /// Stores new `Arc<T>` if `FillOnceAtomicArc` currently contains a `None` /// /// This operation is implemented as a single atomic `compare_and_swap`. /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicArc; /// # env_logger::init(); /// use std::sync::atomic::Ordering; /// let option = FillOnceAtomicArc::default(); /// let old = option.try_store(5, Ordering::Relaxed); /// assert!(old.is_ok()); /// assert_eq!(option.get_ref(Ordering::Relaxed), Some(&5)); /// /// let failed_to_store = option.try_store(10, Ordering::Relaxed); /// assert!(failed_to_store.is_err()); /// assert_eq!(option.get_ref(Ordering::Relaxed), Some(&5)); /// ``` #[inline] pub fn try_store<V>(&self, data: V, order: Ordering) -> Result<(), NotEmpty> where V: Into<Arc<T>>, { self.0.try_store(data.into(), order) } /// Atomically retrieves a cloned `Option<Arc<T>>` /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicArc; /// # env_logger::init(); /// use std::sync::atomic::Ordering; /// let empty: FillOnceAtomicArc<()> = FillOnceAtomicArc::new(None); /// assert_eq!(empty.load(Ordering::Relaxed), None); /// /// let filled = FillOnceAtomicArc::from(10); /// assert_eq!(filled.load(Ordering::Relaxed).map(|a| *a), Some(10)); /// ``` #[inline] pub fn load(&self, order: Ordering) -> Option<Arc<T>> { self.0.get_ref(order).cloned() } /// Atomically extracts a reference to the element stored /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicArc; /// # env_logger::init(); /// use std::sync::atomic::Ordering; /// let empty: FillOnceAtomicArc<()> = FillOnceAtomicArc::new(None); /// assert_eq!(empty.get_ref(Ordering::Relaxed), None); /// /// let filled = FillOnceAtomicArc::from(10); /// assert_eq!(filled.get_ref(Ordering::Relaxed), Some(&10)); /// ``` #[inline] pub fn get_ref(&self, order: Ordering) -> Option<&T> { self.0.get_ref(order).map(|arc| &**arc) } /// Converts itself into a `Option<Arc<T>>` /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicArc; /// # env_logger::init(); /// let ten = FillOnceAtomicArc::from(10); /// assert_eq!(ten.into_inner().map(|a| *a), Some(10)); /// ``` #[inline] pub fn into_inner(self) -> Option<Arc<T>> { self.0.into_inner().map(|a| Arc::clone(&*a)) } /// Creates new `FillOnceAtomicArc` based on a raw pointer /// /// # Safety /// /// Unsafe because it uses a raw pointer, so it can't be sure of its origin (and ownership) /// /// You must own the pointer to call this /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicArc; /// # env_logger::init(); /// use std::{sync::Arc, sync::atomic::Ordering, ptr::null_mut}; /// let empty = unsafe { FillOnceAtomicArc::<()>::from_raw(null_mut()) }; /// assert_eq!(empty.get_ref(Ordering::Relaxed), None); /// /// let ptr = Box::into_raw(Box::new(Arc::new(10))); /// let filled = unsafe { FillOnceAtomicArc::from_raw(ptr) }; /// assert_eq!(filled.get_ref(Ordering::Relaxed), Some(&10)); /// ``` #[inline] pub unsafe fn from_raw(ptr: *mut Arc<T>) -> Self { FillOnceAtomicArc(FillOnceAtomicOption::from_raw(ptr)) } /// Atomically extracts the stored pointer /// /// If pointer returned is not null it's safe to deref as long as you don't drop the `FillOnceAtomicArc` /// /// # Safety /// /// To deref it you must ensure that it's not `null`, the `FillOnceAtomicArc` wasn't dropped /// /// Returns `null` if `FillOnceAtomicArc` is empty (was not initialized) /// /// /// ```rust /// # use voluntary_servitude::atomics::FillOnceAtomicArc; /// # env_logger::init(); /// use std::{sync::atomic::Ordering, ptr::null_mut, ops::Deref}; /// let empty: FillOnceAtomicArc<()> = FillOnceAtomicArc::new(None); /// assert_eq!(empty.get_raw(Ordering::Relaxed), null_mut()); /// /// let filled = FillOnceAtomicArc::from(10); /// assert_eq!(unsafe { (&*filled.get_raw(Ordering::Relaxed)).deref().deref() }, &10); /// ``` #[inline] pub fn get_raw(&self, order: Ordering) -> *mut Arc<T> { self.0.get_raw(order) } } impl<T> Default for FillOnceAtomicArc<T> { #[inline] fn default() -> Self { Self::from(None) } } impl<T> From<T> for FillOnceAtomicArc<T> { #[inline] fn from(value: T) -> Self { Self::from(Arc::new(value)) } } impl<T> From<Arc<T>> for FillOnceAtomicArc<T> { #[inline] fn from(into_ptr: Arc<T>) -> Self { Self::from(Some(into_ptr)) } } impl<T> From<Option<Arc<T>>> for FillOnceAtomicArc<T> { #[inline] fn from(arc: Option<Arc<T>>) -> Self { trace!("From Option<Arc<T>>"); FillOnceAtomicArc(FillOnceAtomicOption::from(arc.map(Box::new))) } } impl<T> Pointer for FillOnceAtomicArc<T> { #[inline] fn fmt(&self, f: &mut Formatter) -> fmt::Result { Debug::fmt(&self.get_raw(Ordering::Relaxed), f) } } impl<T: Debug> Debug for FillOnceAtomicArc<T> { #[inline] fn fmt(&self, f: &mut Formatter) -> fmt::Result { f.debug_tuple("FillOnceAtomicArc") .field(&self.load(Ordering::Relaxed)) .finish() } } #[cfg(test)] mod tests { use super::*; #[test] fn test_send() { fn assert_send<T: Send>() {} assert_send::<FillOnceAtomicArc<()>>(); } #[test] fn test_sync() { fn assert_sync<T: Sync>() {} assert_sync::<FillOnceAtomicArc<()>>(); } }